Journal articles: 'Conservative and non-conservative environmental tracers'

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Champ, D. R., and J. Schroeter. "Bacterial Transport in Fractured Rock – A Field-Scale Tracer Test at the Chalk River Nuclear Laboratories." Water Science and Technology 20, no. 11-12 (November 1, 1988): 81–87. http://dx.doi.org/10.2166/wst.1988.0269.

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The potential for transport of bacteria by groundwater in fractured crystalline rock was assessed in a series of field-scale tracer tests. The breakthrough curves for injected Escherichla coll and “non-reactive” particle tracers were compared with those for conservative inorganic and radioactive tracers. Rapid transport, relative to the conservative tracers, of both bacteria and non-reactive particles was observed. The first appearance of both was with, or slightly before, the conservative tracers for water movement. Removal of the bacteria and particles by filtration processes occurred and was quantified through the calculation of filter factors. The filtration process in this fracture system is similar to that found in a gravel aquifer. From the results we can conclude that particulate contaminants can be very rapidly transported in fracture systems and that continuing sources of contamination could lead to relatively high local concentrations of particulate contaminants compared with the average at any given distance from the source. It was also concluded that the use of traditional conservative tracers, for water movement, to assess the potential for movement of particulate contaminants could lead to significant underestimates of exposure to particulate contaminants due to consumption of water from water recovery wells located in fractured media.

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Gresch, M., D. Braun, and W. Gujer. "The role of the flow pattern in wastewater aeration tanks." Water Science and Technology 61, no. 2 (January 1, 2010): 407–14. http://dx.doi.org/10.2166/wst.2010.803.

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Reactor hydraulics is one of the key factors for plant performance and plant control. The residence time distribution is a good but limited indicator of reactor hydraulics. A more detailed view is obtained by direct observations within the reactor. Two different techniques (conservative tracer, reactive tracer) are discussed to detect major anomalies in the flow field of a wastewater aeration tank. Experiments with conservative tracers give valuable information over a very limited period of time making the analysis of the flow field difficult. On the other hand, reactive tracers can be monitored long term which helps identifying the flow pattern provided that a high spatial and temporal resolution of the measurements is applied. Experimental data is used to determine the structure and the parameters of a compartment model that corresponds well with the measurements.

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Stephenson, Ruth, Craig Sheridan, and Uwe Kappelmeyer. "A curve-shift technique for the use of non-conservative organic tracers in constructed wetlands." Science of The Total Environment 752 (January 2021): 141818. http://dx.doi.org/10.1016/j.scitotenv.2020.141818.

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Lizaga, Ivan, Borja Latorre, Leticia Gaspar, and Ana Navas. "Consensus ranking as a method to identify non-conservative and dissenting tracers in fingerprinting studies." Science of The Total Environment 720 (June 2020): 137537. http://dx.doi.org/10.1016/j.scitotenv.2020.137537.

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Eatough, D. J., C. L. Benner, H. Tang, V. Landon, G. Richards, F. M. Caka, J. Crawford, E. A. Lewis, L. D. Hansen, and N. L. Eatough. "The chemical composition of environmental tobacco smoke III. Identification of conservative tracers of environmental tobacco smoke." Environment International 15, no. 1-6 (January 1989): 19–28. http://dx.doi.org/10.1016/0160-4120(89)90005-6.

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von Gunten, U., M. Elovitz, and H. P. Kaiser. "Calibration of full-scale ozonation systems with conservative and reactive tracers." Journal of Water Supply: Research and Technology—AQUA 48, no. 6 (September 1999): 250–56. http://dx.doi.org/10.2166/aqua.1999.0027.

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Lemke, Dennis, Pierre-André Schnegg, Marc Schwientek, Karsten Osenbrück, and Olaf A. Cirpka. "On-line fluorometry of multiple reactive and conservative tracers in streams." Environmental Earth Sciences 69, no. 2 (February 27, 2013): 349–58. http://dx.doi.org/10.1007/s12665-013-2305-3.

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Barberá, J. A., B. Andreo, and C. Almeida. "Using non-conservative tracers to characterise karstification processes in the Merinos-Colorado-Carrasco carbonate aquifer system (southern Spain)." Environmental Earth Sciences 71, no. 2 (September 7, 2013): 585–99. http://dx.doi.org/10.1007/s12665-013-2754-8.

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Puente, C. E., O. Robayo, M. C. Díaz, and B. Sivakumar. "A fractal-multifractal approach to groundwater contamination. 1. Modeling conservative tracers at the Borden site." Stochastic Environmental Research and Risk Assessment 15, no. 5 (October 2001): 357–71. http://dx.doi.org/10.1007/pl00009791.

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Chen, Hao, Fu Li Chen, Yong Ying Zhu, Ming Zeng, Chen Sun, and Qiang Bao. "Numerical Study of Water Exchange in Environment Engineering in Pulandian Bay." Advanced Materials Research 908 (March 2014): 425–28. http://dx.doi.org/10.4028/www.scientific.net/amr.908.425.

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By the tracers of dissolved conservative substance, establishing the convection diffusion numerical model of water exchange in the bay. The water exchange simulation results derive the half-exchange period of each region.And based on the hydrological data,model results show the tidal current field and the half-exchange period,analyzing the water exchange properties and the convective transport of pollutants to the Pulandian Bay.The numerical simulation results provide the scientific basis and basic data for the sea area construction and environmental protection.

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Rodriguez, A., A. Sánchez-Arcilla, J. M. Redondo, E. Bahia, and J. P. Sierra. "Pollutant dispersion in the nearshore region: modelling and measurements." Water Science and Technology 32, no. 9-10 (November 1, 1995): 169–78. http://dx.doi.org/10.2166/wst.1995.0682.

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Some results on pollutant dispersion modelling and tracer measurements for the Mediterranean Spanish coast are presented. Two hydrodynamic models have been used to simulate wind and wave induced circulation in the nearshore and surf zones respectively. A “near field” model has been used in order to simulate the initial conditions for the local “far field” dispersion model. Two study cases are presented: The first one shows the mixing of conservative tracers in a Mediterranean surf zone from an experimental and numerical models used to predict bacterial dispersion from the main sea outfalls of Barcelona City. The comparison between dye dispersion experiments and model in the surf zone is good, while the outfall predictions show the importance of accurately modelling the effects of buoyancy on the plume.

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Pietrzak, Damian, Jarosław Kania, Ewa Kmiecik, and Katarzyna Wątor. "Identification of transport parameters of chlorides in different soils on the basis of column studies." Geologos 25, no. 3 (December 1, 2019): 225–29. http://dx.doi.org/10.2478/logos-2019-0024.

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Abstract Knowledge of transport patterns of chemicals in groundwater is essential for environmental assessment of their potential impact. In the present study, the mobility of a chloride tracer injected into three different soils was investigated, using column experiments. The column tests were performed under steady-state conditions to determine parameters of chloride migration through soils. Based on breakthrough curves, pore-water velocity, dispersion coefficient and dispersivity constant were calculated for each soil sample using CXTFIT/STANMOD software. Pore-water velocity was in the range of 0.31 cm/min for fine sand, to 0.35 cm/min for silty sand and to 0.40 cm/min for vari-grained sand. The highest values of dispersion coefficient and dispersivity constant were observed for silty sand (0.55 cm2/min and 1.55 cm, respectively), while the lowest value was found for fine sand (0.059 cm2/min and 0.19 cm, respectively). Column experiments for chlorides (conservative tracer) are a preliminary stage for further research which will be undertaken to investigate migration parameters of selected neonicotinoids (reactive tracers) through different soils.

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Hamann, Ilse M., and James H. Swift. "A consistent inventory of water mass factors in the intermediate and deep Pacific Ocean derived from conservative tracers." Deep Sea Research Part A. Oceanographic Research Papers 38 (1991): S129—S169. http://dx.doi.org/10.1016/s0198-0149(12)80008-2.

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Kiecak, Aleksandra, Friederike Breuer, and Christine Stumpp. "Column Experiments on Sorption Coefficients and Biodegradation Rates of Selected Pharmaceuticals in Three Aquifer Sediments." Water 12, no. 1 (December 19, 2019): 14. http://dx.doi.org/10.3390/w12010014.

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The presence of pharmaceuticals in the environment, and in groundwater, has been recognized as a great environmental concern. Biodegradation and sorption are the main processes leading to the removal of contamination from the water phase. The aim of this study was to determine the transport processes of selected pharmaceuticals (antipyrine, atenolol, carbamazepine, caffeine, diclofenac, ketoprofen, sulfamethoxazole) in selected sediments (coarse sand, medium sand, sandy loam) in laboratory experiments. Moreover, the impact of flow velocities on the sorption and degradation rates of the selected compounds was studied. Column experiments were performed at three flow velocities, under abiotic and biotic conditions, applying conservative (bromide) and reactive tracers (pharmaceuticals). From the breakthrough curves, retardation factors and degradation rates were determined and the influence of variable flow conditions on transport parameters was evaluated. Low observed concentrations and recoveries of atenolol indicated a strong influence of sorption on its transport. Diclofenac, caffeine, and carbamazepine were also affected by sorption but to a lesser extent. Sulfamethoxazole, ketoprofen, and antipyrine were recovered nearly completely, indicating an almost conservative transport behavior. Biodegradation was small for all the compounds, as the results from biotic and abiotic column experiments were similar. Transport of the tested pharmaceuticals was not influenced by different flow velocities, as similar modelled degradation rates and retardation factors were found for all tested flow velocities.

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de Grandpré, Jean, Monique Tanguay, Abdessamad Qaddouri, Mohamed Zerroukat, and Chris A. McLinden. "Semi-Lagrangian Advection of Stratospheric Ozone on a Yin–Yang Grid System." Monthly Weather Review 144, no. 3 (February 19, 2016): 1035–50. http://dx.doi.org/10.1175/mwr-d-15-0142.1.

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Abstract The lack of formal mass conservation that is inherent to the standard semi-Lagrangian transport scheme represents a significant model limitation that needs to be addressed. The magnitude of this impact depends on the nature of the advected quantity and particularly on the strength of species spatiotemporal variability. In this study, this issue is examined in the context of two configurations of the Environment Canada Global Environmental Multiscale (GEM) model. The first configuration (GEM Lat–Lon) is based on a global latitude–longitude grid system with the Arakawa C grid in the horizontal. The second configuration (GEM Yin–Yang) uses the overset Yin–Yang grid, which is singularity free and has quasi-uniform resolution. Both model versions have been used for studying the mass conservation property of passive and nonpassive tracers such as stratospheric ozone using different shape-preserving schemes and a global mass fixer. Experiments with idealized tracers indicate that the implementation of a global mass fixer and a conservative shape-preserving scheme reduces the error field in both 2D and 3D configurations. In the case of stratospheric ozone, the study demonstrates that the mass conservation error is significantly reduced with the use of the Yin–Yang grid. This is attributed to the quasi-uniform nature of the grid that contributes to improve the accuracy of the computation particularly in high-latitude regions where most of the ozone mass resides. The study demonstrates the potential benefits of using a quasi-uniform Yin–Yang grid system and shows that chemical constituents can serve as a useful diagnostic for the evaluation of numerical weather prediction (NWP) models.

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Sélas, B., A. Lakel, Y. Andres, and P. Le Cloirec. "Wastewater reuse in on-site wastewater treatment: bacteria and virus movement in unsaturated flow through sand filter." Water Science and Technology 47, no. 1 (January 1, 2003): 59–64. http://dx.doi.org/10.2166/wst.2003.0016.

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In on-site wastewater treatment plants, effluents are pre-treated by septic tank and treated by soil infiltration or sand filtration systems, with unsaturated flow conditions. These systems remove efficiently carbon, nitrogen and suspended solids. But for microbial pollution, the treatment efficiency depends on the hydrodynamic behaviour and filtering media characteristics. Contamination of superficial water and groundwater due to pathogenic viruses and pathogenic bacteria is responsible for many diseases. The objective of this study is to approach the mechanisms and operating conditions to control bacteria and virus release in the environment. Experiments were carried out on reactors of different length packed with sand. Hydraulic load of 90 cm.d−1 with a pulse periodic flow was used. The influence of chemical composition of the solution on the treatment efficiency has also been studied. For the first time, the residence time distribution (RTD) has been studied using a conservative tracer (KI), to determine the main hydrodynamic parameters. For the second time, the RTD with bacterial and viral tracers (E. coli, bacteriophage MS2) was applied, with the aim to define microbial behaviour in filtering media, including adsorption and filtration phenomena. This work allowed us to determine retardation factors according to the hydraulic loads and chemical composition.

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Zaman, M., M. L. Nguyen, A. J. Gold, P. M. Groffman, D. Q. Kellogg, and R. J. Wilcock. "Nitrous oxide generation, denitrification, and nitrate removal in a seepage wetland intercepting surface and subsurface flows from a grazed dairy catchment." Soil Research 46, no. 7 (2008): 565. http://dx.doi.org/10.1071/sr07217.

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Little is known about seepage wetlands, located within agricultural landscapes, with respect to removing nitrate (NO3−) from agricultural catchments, mainly through gaseous emissions of nitrous oxide (N2O) and dinitrogen (N2) via denitrification. These variables were quantified using a push–pull technique where we introduced a subsurface water plume spiked with 15N-enriched NO3− and 2 conservative tracers [bromide (Br−) and sulfur hexafluoride (SF6)] into each of 4 piezometers and extracted the plume from the same piezometers throughout a 48-h period. To minimise advective and dispersive flux, we placed each of these push–pull piezometers within a confined lysimeter (0.5 m diameter) installed around undisturbed wetland soil and vegetation. Although minimal dilution of the subsurface water plumes occurred, NO3−-N concentration dropped sharply in the first 4 h following dosing, such that NO3−-limiting conditions (<2 mg/L of NO3-N) for denitrification prevailed over the final 44 h of the experiment. Mean subsurface water NO3− removal rates during non-limiting conditions were 15.7 mg/L.day. Denitrification (based on the generation of isotopically enriched N2O plus N2) accounted for only 7% (1.1 mg/L.day) of the observed groundwater NO3− removal, suggesting that other transformation processes, such as plant uptake, were responsible for most of the NO3− removal. Although considerable increases in 15N-enriched N2O levels were initially observed following NO3− dosing, no net emissions were generated over the 48-h study. Our results suggest that this wetland may be a source of N2O emissions when NO3− concentrations are elevated (non-limited), but can readily remove N2O (function as a N2O sink) when NO3− levels are low. These results argue for the use of engineered bypass flow designs to regulate NO3− loading to wetland denitrification buffers during high flow events and thus enhance retention time and the potential for NO3−-limiting conditions and N2O removal. Although this type of management may reduce the full potential for wetland NO3− removal, it provides a balance between water quality goals and greenhouse gas emissions.

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Bryce Cooper, A. "Coupling Wetland Treatment to Land Treatment: an Innovative Method for Nitrogen Stripping?" Water Science and Technology 29, no. 4 (February 1, 1994): 141–49. http://dx.doi.org/10.2166/wst.1994.0177.

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The ability of two small wetlands to remove added nitrate was studied as part of a wider investigation into the feasibility of using a combined forest irrigation-wetland treatment system to meet strict receiving water limits. In laboratory microcosm experiments, wetland sediments removed nitrate at rates between 0.019 - 0.609 g m−2 d−1, with rates being dependent upon nitrate loading and the vegetation that supplied the decaying organic matter (Typha orientalis > Carex spp. > Azollafiliculoides). Denitrification could account for between 32 - 100% of the observed nitrate loss, indicating that in some microcosms other nitrate removal processes were operating. Additions of bromide (a conservative tracer) and nitrate to the two wetlands demonstrated more rapid nitrate loss in a Typha stand (decay coefficient, ke = 4.44 d−1) compared to loss in an Azolla pond (ke = 1.1 d−1). The time course of bromide concentration at the wetland outlets, and its distribution within the wetlands, showed the presence of preferential flow paths and “dead” zones. This non-uniform flow is a common characteristic of wetlands and, in this case, may exert a major control on the scheme's overall nitrate removal efficiency.

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Pratte, Steve, Michelle Garneau, and François De Vleeschouwer. "Late-Holocene atmospheric dust deposition in eastern Canada (St. Lawrence North Shore)." Holocene 27, no. 1 (July 28, 2016): 12–25. http://dx.doi.org/10.1177/0959683616646185.

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Dust deposition in two ombrotrophic peatlands (Baie and Ile du Havre peatland (IDH) bogs) of the Estuary and Gulf of the St. Lawrence in eastern Canada was reconstructed using elemental geochemistry. The rare earth elements (REEs) and other lithogenic element concentrations were measured by ICP-oES and Q-ICP-MS along two peat cores spanning the last 4000 years. Principal component analyses on the geochemical profiles show that REEs display the same behavior as Al, Ti, Sc, and Zr, all conservative elements, which suggests that REEs are immobile in the studied peat bogs and can be used as tracers of dust deposition. Plant macrofossils were also used to infer past environmental and humidity changes. The dust fluxes were reconstructed using the sum of REEs (ΣREE). The range of dust deposition varies from 0.2 to 3.8 g m−2 yr−1 in the Baie bog, while the IDH bog shows lower fluxes ranging between 0.1 and 1.2 g m−2 yr−1. The highest dust fluxes in the Baie bog were recorded from 1750–1000 cal. BP to 600–100 cal. BP and occur at the same time as periods of high variability in the macrofossil record (i.e. successive layers dominated by Sphagnum or Ericaceae). The timing of these events in the dust and macrofossil records also corresponds to documented cold periods. These two periods have been identified as episodes of climatic instability, which could have been caused by changes in the wind regime.

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Cao, Viet, Mario Schaffer, Reza Taherdangkoo, and Tobias Licha. "Solute Reactive Tracers for Hydrogeological Applications: A Short Review and Future Prospects." Water 12, no. 3 (February 28, 2020): 653. http://dx.doi.org/10.3390/w12030653.

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Tracer testing is a mature technology used for characterizing aquatic flow systems. To gain more insights from tracer tests a combination of conservative (non-reactive) tracers together with at least one reactive tracer is commonly applied. The reactive tracers can provide unique information about physical, chemical, and/or biological properties of aquatic systems. Although, previous review papers provide a wide coverage on conservative tracer compounds there is no systematic review on reactive tracers yet, despite their extensive development during the past decades. This review paper summarizes the recent development in compounds and compound classes that are exploitable and/or have been used as reactive tracers, including their systematization based on the underlying process types to be investigated. Reactive tracers can generally be categorized into three groups: (1) partitioning tracers, (2) kinetic tracers, and (3) reactive tracers for partitioning. The work also highlights the potential for future research directions. The recent advances from the development of new tailor-made tracers might overcome existing limitations.

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Medici, Giacomo, Landis Jared West, Pippa Joanne Chapman, and Steven Allan Banwart. "Prediction of contaminant transport in fractured carbonate aquifer types: a case study of the Permian Magnesian Limestone Group (NE England, UK)." Environmental Science and Pollution Research 26, no. 24 (June 25, 2019): 24863–84. http://dx.doi.org/10.1007/s11356-019-05525-z.

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AbstractViruses and bacteria which are characterized by finite lives in the subsurface are rapidly transported via fractures and cavities in fractured and karst aquifers. Here, we demonstrate how the coupling of a robust outcrop characterization and hydrogeophysical borehole testing is essential for prediction of contaminant velocities and hence wellhead protection areas. To show this, we use the dolostones of the Permian Magnesian Limestone aquifer in NE England, where we incorporated such information in a groundwater flow and particle tracking model. Within this aquifer, flow in relatively narrow (mechanical aperture of ~ 10−1–1 mm) fractures is coupled with that in pipe cavities (~ 0.20-m diameter) following normal faults. Karstic cavities and narrow fractures are hydraulically very different. Thus, the solutional features are represented within the model by a pipe network (which accounts for turbulence) embedded within an equivalent porous medium representing Darcian flowing fractures. Incorporation of fault conduits in a groundwater model shows that they strongly influence particle tracking results. Despite this, away from faulted areas, the effective flow porosity of the equivalent porous medium remains a crucial parameter. Here, we recommend as most appropriate a relatively low value of effective porosity (of 2.8 × 10−4) based on borehole hydrogeophysical testing. This contrasts with earlier studies using particle tracking analyses on analogous carbonate aquifers, which used much higher values of effective porosity, typically ~ 102 times higher than our value, resulting in highly non-conservative estimates of aquifer vulnerability. Low values of effective flow porosities yield modelled flow velocities ranging from ~ 100 up to ~ 500 m/day in un-faulted areas. However, the high fracturing density and presence of karstic cavities yield modelled flow velocities up to ~ 9000 m/day in fault zones. The combination of such flow velocities along particle traces results in 400-day particle traces up to 8-km length, implying the need for large well protection areas and high aquifer vulnerability to slowly degrading contaminants.

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Huang, Yibin, Yanmei Li, Peter S. K. Knappett, Daniel Montiel, Jianjun Wang, Manuel Aviles, Horacio Hernandez, Itza Mendoza-Sanchez, and Isidro Loza-Aguirre. "Water Quality Assessment Bias Associated with Long-Screened Wells Screened across Aquifers with High Nitrate and Arsenic Concentrations." International Journal of Environmental Research and Public Health 19, no. 16 (August 11, 2022): 9907. http://dx.doi.org/10.3390/ijerph19169907.

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Semi-arid regions with little surface water commonly experience rapid water table decline rates. To hedge against the falling water table, production wells in central Mexico are commonly installed to depths of several hundred meters below the present water table and constructed as open boreholes or perforated casings across their entire length. Such wells represent highly conductive pathways leading to non-negligible flow across chemically distinct layers of an aquifer—a phenomenon known as ambient flow. The objectives of this study were to estimate the rate of ambient flow in seven production wells utilizing an end-member mixing model that is constrained by the observed transient chemical composition of produced water. The end-member chemical composition of the upper and lower layers of an urban aquifer that overlies geothermal heat is estimated to anticipate the future quality of this sole source of water for a rapidly growing urban area. The comprehensive water chemistry produced by seven continuously perforated municipal production wells, spanning three geologically unique zones across the city of San Miguel de Allende in Guanajuato State, was monitored during one day of pumping. The concentration of conservative constituents gradually converged on steady-state values. The model indicates that, relative to the lower aquifer, the upper aquifer generally has higher specific conductance (SC), chloride (Cl), nitrate (NO3), calcium (Ca), barium (Ba) and magnesium (Mg). The lower aquifer generally has a higher temperature, sodium (Na), boron (B), arsenic (As) and radon (Rn). Ambient flow ranged from 33.1 L/min to 225.7 L/min across the seven wells, but this rate for a given well varied depending on which tracer was used. This new 3D understanding of the chemical stratification of the aquifer suggests that as water tables continue to fall, concentrations of geothermally associated contaminants of concern will increase in the near future, potentially jeopardizing the safety of municipal drinking water.

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Cross, Jessica N., Jeremy T. Mathis, Nicholas R. Bates, and Robert H. Byrne. "Conservative and non-conservative variations of total alkalinity on the southeastern Bering Sea shelf." Marine Chemistry 154 (August 2013): 100–112. http://dx.doi.org/10.1016/j.marchem.2013.05.012.

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Lindegren, Roger, and Leif G. Anderson. "‘NO’ as a conservative tracer in the Weddell Sea." Marine Chemistry 35, no. 1-4 (November 1991): 179–87. http://dx.doi.org/10.1016/s0304-4203(09)90016-0.

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Tang, Jie, Chungang Chen, Xueshun Shen, Feng Xiao, and Xingliang Li. "A Positivity-preserving Conservative Semi-Lagrangian Multi-moment Global Transport Model on the Cubed Sphere." Advances in Atmospheric Sciences 38, no. 9 (July 22, 2021): 1460–73. http://dx.doi.org/10.1007/s00376-021-0393-7.

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AbstractA positivity-preserving conservative semi-Lagrangian transport model by multi-moment finite volume method has been developed on the cubed-sphere grid. Two kinds of moments (i.e., point values (PV moment) at cell interfaces and volume integrated average (VIA moment) value) are defined within a single cell. The PV moment is updated by a conventional semi-Lagrangian method, while the VIA moment is cast by the flux form formulation to assure the exact numerical conservation. Different from the spatial approximation used in the CSL2 (conservative semi-Lagrangian scheme with second order polynomial function) scheme, a monotonic rational function which can effectively remove non-physical oscillations is reconstructed within a single cell by the PV moments and VIA moment. To achieve exactly positive-definite preserving, two kinds of corrections are made on the original conservative semi-Lagrangian with rational function (CSLR) scheme. The resulting scheme is inherently conservative, non-negative, and allows a Courant number larger than one. Moreover, the spatial reconstruction can be performed within a single cell, which is very efficient and economical for practical implementation. In addition, a dimension-splitting approach coupled with multi-moment finite volume scheme is adopted on cubed-sphere geometry, which benefitsthe implementation of the 1D CSLR solver with large Courant number. The proposed model is evaluated by several widely used benchmark tests on cubed-sphere geometry. Numerical results show that the proposed transport model can effectively remove nonphysical oscillations and preserve the numerical non-negativity, and it has the potential to transport the tracers accurately in a real atmospheric model.

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Periáñez, R., and C. Miró. "Time scales for conservative and non-conservative radionuclide transport in the English Channel." Radioprotection 44, no. 5 (2009): 11–16. http://dx.doi.org/10.1051/radiopro/20095009.

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Yevenes-Burgos, M. A., and C. M. Mannaerts. "Untangling hydrological pathways and nitrate diffusive sources by chemical appraisal in a stream network of a reservoir catchment." Hydrology and Earth System Sciences Discussions 8, no. 2 (March 2, 2011): 2289–322. http://dx.doi.org/10.5194/hessd-8-2289-2011.

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Abstract. Stable water isotopes and water hydrochemistry of a catchment in the Alentejo region, south Portugal, were analysed to investigate source origins of water and nitrate flows towards a reservoir. The 353 km2 headwater catchment of Roxo river, is strongly influenced by agricultural impacts, and high variations in water and chemical inflows into an important drinking and irrigation water supply (108 m3) are observed. This leads to regular disputes on water quantity and quality amongst local authorities and population. Three sampling campaigns in different seasons were used to address the temporal and spatial variations in stream and groundwater hydrochemistry and water isotopic signatures. A total of 27 sampling points from the stream network, shallow groundwater and reservoir were used. Isotopic signatures and chemistry of precipitation were obtained from local data of the Global Network of Isotopes in Precipitation (GNIP) and the Global Atmosphere Watch (GAWSIS) network. Other meteorological, hydrological and environmental datasets were obtained from local authorities. The stable water isotopes deuterium (δ2H), oxygen-18 (δ18O) together with chloride (Cl–) and sulphate (SO42–) were used as environmental tracers in the hydrological pathways. Water pathways were then related with nitrate concentrations to elucidate potential relationships between the water and nutrient sources. Interpretation of isotope signatures showed a high degree of isotope enrichment in both surface (stream flow) and shallow groundwater. For the entire period, most of stream waters were located right of the global meteoric water line or GMWL and plotted along a local evaporation line (LEL) established for the study area. The LEL showed slopes similar to stream systems in other dry environments. Monthly stream flow and precipitation, seasonal isotope compositions and major ion chemistry data were used for an evaluation of the relative contribution of water sources using an end-member mixing analysis. An extensive PCA or principal component analysis preceded the mixing analysis. Contributions of the three water end-members in the catchment: groundwater, surface runoff and precipitation to stream flow could be identified based on their 2H, 18O and Cl– signatures. Also two hydro chemical data outliers for Cl– and NO3– from two sample points were identified by the analysis and could be related to local waste water outfalls, giving the method also diagnostic value for pollution source allocation. The shallow groundwater source could be related to stream nitrate concentrations during the wet seasons, indicating a linkage between hydrological flow paths, nitrate sources and season. Conversely, weak links between precipitation, and surprisingly also surface water runoff and nitrate levels were found. In this catchment, we found a consistent pattern of the particular groundwater end member, being main source of nitrate to the stream water and reservoir, based on conservative mixing of the different water sources.

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Engdahl, Nicholas B., Timothy R. Ginn, and Graham E. Fogg. "Scalar dissipation rates in non-conservative transport systems." Journal of Contaminant Hydrology 149 (June 2013): 46–60. http://dx.doi.org/10.1016/j.jconhyd.2013.03.003.

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Belikov, D., S. Maksyutov, T. Miyasaka, T. Saeki, R. Zhuravlev, and B. Kiryushov. "Mass-conserving tracer transport modelling on a reduced latitude-longitude grid." Geoscientific Model Development Discussions 3, no. 4 (October 20, 2010): 1737–81. http://dx.doi.org/10.5194/gmdd-3-1737-2010.

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Abstract. The need to perform long-term simulations with reasonable accuracy has led to the development of mass-conservative and efficient numerical methods for solving the transport equation in forward and inverse models. We designed and implemented a flux-form (Eulerian) tracer transport algorithm in the National Institute for Environmental Studies Transport Model (NIES TM), which is used for simulating diurnal and synoptic-scale variations of tropospheric long-lived constituents, as well as their seasonal and inter-annual variability. Implementation of the flux-form method requires the mass conservative wind fields. However, the model is off-line and is driven by datasets from a global atmospheric model or data assimilation system, in which vertically integrated mass changes are not in balance with the surface pressure tendency and mass conservation is not achieved. To rectify the mass-imbalance, a flux-correction method is employed. To avoid singularity near the poles caused by the small grid size arising from the meridional convergence problem, the proposed model uses a reduced latitude-longitude grid scheme, in which the grid size is doubled several times approaching the poles. This approach overcomes the Courant condition in the Polar Regions, maintains a reasonably high integration time-step and ensures adequate model performance during simulations. To assess the model performance, we performed global transport simulations for SF6, 222Rn and CO2. The results were compared with observations available from the World Data Centre for Greenhouse Gases, GLOBALVIEW and the Hateruma monitoring station, Japan. Overall, the results show that the proposed flux-form version of NIES TM can produce tropospheric tracer transport more realistically than previously possible. The reasons for this improvement are discussed.

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Sarma, Arup Kumar, and Anupal Baruah. "Performance of conservative and non-conservative two-dimensional shallow water models in wavy river bed." International Journal of Hydrology Science and Technology 1, no. 1 (2022): 1. http://dx.doi.org/10.1504/ijhst.2022.10046835.

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Sarma, Arup Kumar, and Anupal Baruah. "Performance of conservative and non-conservative two-dimensional shallow water models in wavy river bed." International Journal of Hydrology Science and Technology 1, no. 1 (2022): 1. http://dx.doi.org/10.1504/ijhst.2022.10046835.

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Bork, Marcus, Jens Lange, Markus Graf-Rosenfellner, and Friederike Lang. "Controls of fluorescent tracer retention by soils and sediments." Hydrology and Earth System Sciences 24, no. 2 (March 3, 2020): 977–89. http://dx.doi.org/10.5194/hess-24-977-2020.

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Abstract. Fluorescent dyes like uranine (UR) and sulforhodamine B (SRB) have been used for decades as artificial tracers in hydrological studies. Recently, attempts have been made to trace organic pollutants in soil with such dyes, but the knowledge of the controls of sorption of UR and SRB in soils is still incomplete and poorly standardised. For this reason, we selectively controlled clay, organic matter (OM) and pH within batch experiments and quantified systematically the impact and possible interactions of these controls on the adsorption of UR and SRB. Sorption isotherms were determined using a sandy sediment and a silty loamy subsoil and topsoil (0.6–2.8 % organic carbon (OC)) at pH values of 5.5, 6.5 and 7.5. Additionally, OM was removed from topsoil and subsoil samples by H2O2 treatment and the clay mineral montmorillonite was added to the sandy sediment. We found a negative relationship between the linear sorption coefficient Kd and pH that was stronger for UR than for SRB. Increasing repulsion forces between negative sorption sites and tracer functional groups at higher pH values might explain these results. Adsorption of UR and SRB increased with increasing clay content due to more specific surface area and associated sorption sites. An addition of 4 % of the clay mineral montmorillonite sufficed to adsorb nearly 100 % of both tracers. The influence of OM was more complex: while the adsorption of UR increased with increasing OC concentration, the opposite was observed for SRB. Our study indicates the high relevance of physico-chemical properties of soils and sediments for the fate of applied tracers and for their more conservative or non-conservative behaviour. Overall, the reported results will help to optimise the use of fluorescent tracers in terrestrial ecosystems and to increase their potential as a cheap and fast tool to gain insights into the fate of pollutants in soils and sediments.

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Belikov, D., S. Maksyutov, T. Miyasaka, T. Saeki, R. Zhuravlev, and B. Kiryushov. "Mass-conserving tracer transport modelling on a reduced latitude-longitude grid with NIES-TM." Geoscientific Model Development 4, no. 1 (March 22, 2011): 207–22. http://dx.doi.org/10.5194/gmd-4-207-2011.

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Abstract. The need to perform long-term simulations with reasonable accuracy has led to the development of mass-conservative and efficient numerical methods for solving the transport equation in forward and inverse models. We designed and implemented a flux-form (Eulerian) tracer transport algorithm in the National Institute for Environmental Studies Transport Model (NIES TM), which is used for simulating diurnal and synoptic-scale variations of tropospheric long-lived constituents, as well as their seasonal and inter-annual variability. Implementation of the flux-form method requires the mass conservative wind fields. However, the model is off-line and is driven by datasets from a global atmospheric model or data assimilation system, in which vertically integrated mass changes are not in balance with the surface pressure tendency and mass conservation is not achieved. To rectify the mass-imbalance, a flux-correction method is employed. To avoid a singularity near the poles, caused by the small grid size arising from the meridional convergence problem, the proposed model uses a reduced latitude–longitude grid scheme, in which the grid size is doubled several times approaching the poles. This approach overcomes the Courant condition in the Polar Regions, maintains a reasonably high integration time-step, and ensures adequate model performance during simulations. To assess the model performance, we performed global transport simulations for SF6, 222Rn, and CO2. The results were compared with observations available from the World Data Centre for Greenhouse Gases, GLOBALVIEW, and the Hateruma monitoring station, Japan. Overall, the results show that the proposed flux-form version of NIES TM can produce tropospheric tracer transport more realistically than previously possible. The reasons for this improvement are discussed.

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Storck, Florian R., Christian Skark, Frank Remmler, and Heinz-Jürgen Brauch. "Environmental fate and behavior of acesulfame in laboratory experiments." Water Science and Technology 74, no. 12 (September 28, 2016): 2832–42. http://dx.doi.org/10.2166/wst.2016.452.

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Acesulfame is a widely used artificial sweetener. It can be discharged into surface water by domestic wastewater due to its incomplete retention during wastewater treatment. Concentrations may reach up to 10 μg/L for smaller rivers. State-of-the-art analysis allows the determination of acesulfame traces (0.01 μg/L) and thus a potential tracking of the presence of wastewater in riverbank filtrate. To evaluate the behavior of acesulfame in the aquatic environment, biodegradation and sorption of acesulfame were tested. Batch experiments yielded low sorption for several soils (estimated solid–water distribution coefficient of acesulfame <0.1 L/kg). Biodegradation in a fixed-bed reactor was not observed at environmental concentrations of 9 μg/L in aqueous compost and soil extract (observation period 56 days). Only in diluted effluent of a wastewater treatment plant did biodegradation start, after 17 days of operation, and acesulfame completely fade, within 28 days. Flow-through column experiments indicated conservative behavior of acesulfame (recovery >83%) and long-term observations at different concentration levels yielded no biodegradation. Overall, laboratory experiments demonstrated a conservative behavior of acesulfame under conditions typical for riverbank filtration. However, there are hints for certain settings which favor an adaptation of the microbial community and facilitate a rapid biodegradation of acesulfame.

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Comfort, S. D., W. P. Inskeep, and R. H. Lockerman. "Observed and Simulated Transport of a Conservative Tracer under Line‐Source Irrigation." Journal of Environmental Quality 22, no. 3 (July 1993): 554–61. http://dx.doi.org/10.2134/jeq1993.00472425002200030021x.

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Fox, Garey A., Rob Malone, George J. Sabbagh, and Ken Rojas. "Interrelationship of Macropores and Subsurface Drainage for Conservative Tracer and Pesticide Transport." Journal of Environmental Quality 33, no. 6 (November 2004): 2281–89. http://dx.doi.org/10.2134/jeq2004.2281.

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Bazykin, Georgii A., and Alexey S. Kondrashov. "Major role of positive selection in the evolution of conservative segments of Drosophila proteins." Proceedings of the Royal Society B: Biological Sciences 279, no. 1742 (June 6, 2012): 3409–17. http://dx.doi.org/10.1098/rspb.2012.0776.

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Slow evolution of conservative segments of coding and non-coding DNA is caused by the action of negative selection, which removes new mutations. However, the mode of selection that affects the few substitutions that do occur within such segments remains unclear. Here, we show that the fraction of allele replacements that were driven by positive selection, and the strength of this selection, is the highest within the conservative segments of Drosophila protein-coding genes. The McDonald–Kreitman test, applied to the data on variation in Drosophila melanogaster and in Drosophila simulans , indicates that within the most conservative protein segments, approximately 72 per cent (approx. 80%) of allele replacements were driven by positive selection, as opposed to only approximately 44 per cent (approx. 53%) at rapidly evolving segments. Data on multiple non-synonymous substitutions at a codon lead to the same conclusion and additionally indicate that positive selection driving allele replacements at conservative sites is the strongest, as it accelerates evolution by a factor of approximately 40, as opposed to a factor of approximately 5 at rapidly evolving sites. Thus, random drift plays only a minor role in the evolution of conservative DNA segments, and those relatively rare allele replacements that occur within such segments are mostly driven by substantial positive selection.

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Yang, Fan, and Dongfang Liang. "Random-walk simulation of non-conservative pollutant transport in shallow water flows." Environmental Modelling & Software 134 (December 2020): 104870. http://dx.doi.org/10.1016/j.envsoft.2020.104870.

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Di Fede, Olga, Federica Canepa, Vera Panzarella, Rodolfo Mauceri, Carmine Del Gaizo, Alberto Bedogni, Vittorio Fusco, et al. "The Treatment of Medication-Related Osteonecrosis of the Jaw (MRONJ): A Systematic Review with a Pooled Analysis of Only Surgery versus Combined Protocols." International Journal of Environmental Research and Public Health 18, no. 16 (August 10, 2021): 8432. http://dx.doi.org/10.3390/ijerph18168432.

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Medication-related osteonecrosis of the jaw (MRONJ) is a serious adverse reaction of antiresorptive and antiangiogenic agents, and it is also a potentially painful and debilitating condition. To date, no specific studies have prospectively evaluated the efficacy of its treatment and no robust standard of care has been established. Therefore, a systematic review (2007–2020) with a pooled analysis was performed in order to compare MRONJ surgical techniques (conservative or aggressive) versus combined surgical procedures (surgery plus a non-invasive procedure), where 1137 patients were included in the pooled analysis. A statistically significant difference in the 6-month improvement rate, comparing combined conservative surgery versus only aggressive (91% versus 72%, p = 0.05), was observed. No significant difference regarding any group with respect to the 6-month total resolution rate (82% versus 72%) was demonstrated. Of note, conservative surgery combined with various, adjuvant, non-invasive procedures (ozone, LLLT or blood component + Nd:YAG) was found to achieve partial or full healing in all stages, with improved results and the amelioration of many variables. In conclusion, specific adjuvant treatments associated with minimally conservative surgery can be considered effective and safe in the treatment of MRONJ, although well-controlled studies are a requisite in arriving at definitive statements

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Ki, Seo Jin, Jin Hwan Hwang, Joo-Hyon Kang, and Joon Ha Kim. "An analytical model for non-conservative pollutants mixing in the surf zone." Water Science and Technology 59, no. 11 (June 1, 2009): 2117–24. http://dx.doi.org/10.2166/wst.2009.231.

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Accurate simulation of the surf zone is a prerequisite to improve beach management as well as to understand the fundamentals of fate and transport of contaminants. In the present study, a diagnostic model modified from a classic solute model is provided to illuminate non-conservative pollutants behavior in the surf zone. To readily understand controlling processes in the surf zone, a new dimensionless quantity is employed with index of kappa number (K, a ratio of inactivation rate to transport rate of microbial pollutant in the surf zone), which was then evaluated under different environmental frames during a week simulation period. The sensitivity analysis showed that hydrodynamics and concentration gradients in the surf zone mostly depend on n (number of rip currents), indicating that n should be carefully adjusted in the model. The simulation results reveal, furthermore, that large deviation typically occurs in the daytime, signifying inactivation of fecal indicator bacteria is the main process to control surf zone water quality during the day. Overall, the analytical model shows a good agreement between predicted and synthetic data (R2=0.51 and 0.67 for FC and ENT, respectively) for the simulated period, amplifying its potential use in the surf zone modelling. It is recommended that when the dimensionless index is much larger than 0.5, the present modified model can predict better than the conventional model, but if index is smaller than 0.5, the conventional model is more efficient with respect to time and cost.

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McMahon, C. A., M. Fegan, J. Wong, S. C. Long, L. McKittrick, K. Thomas, T. P. Ryan, and B. Rafferty. "Transfer of conservative and non-conservative radionuclides from the Sellafield Nuclear Fuel Reprocessing plant to the coastal waters of Ireland." Radioprotection 40 (May 2005): S629—S634. http://dx.doi.org/10.1051/radiopro:2005s1-092.

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Guillet, Gaëlle, Julia L. A. Knapp, Sylvain Merel, Olaf A. Cirpka, Peter Grathwohl, Christian Zwiener, and Marc Schwientek. "Fate of wastewater contaminants in rivers: Using conservative-tracer based transfer functions to assess reactive transport." Science of The Total Environment 656 (March 2019): 1250–60. http://dx.doi.org/10.1016/j.scitotenv.2018.11.379.

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Gladwell, G. M. L. "Follower forces: Leipholz's researches into generalized variational principles." Canadian Journal of Civil Engineering 17, no. 3 (June 1, 1990): 287–93. http://dx.doi.org/10.1139/l90-035.

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Classical variational principles, for conservative systems, are associated with the names of Lagrange and Hamilton. Generalized variational principles for nonconservative systems were introduced by various authors and in various physical contexts in the period 1945 – 1966. This review traces their development and their use, by Leipholz, in the period 1971 – 1986. Key words: follower forces, variational principles, generalized, nonconservative, adjoint systems, stability, divergence, flutter.

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Ferguson, W. J., and A. Kaddouri. "A Mass Conservative Non-Isothermal Subsurface Three-Phase Flow Model: Formulation and Application." Water, Air, & Soil Pollution 153, no. 1-4 (March 2004): 269–91. http://dx.doi.org/10.1023/b:wate.0000019950.92893.65.

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Kriest, Iris. "Calibration of a simple and a complex model of global marine biogeochemistry." Biogeosciences 14, no. 21 (November 8, 2017): 4965–84. http://dx.doi.org/10.5194/bg-14-4965-2017.

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Abstract. The assessment of the ocean biota's role in climate change is often carried out with global biogeochemical ocean models that contain many components and involve a high level of parametric uncertainty. Because many data that relate to tracers included in a model are only sparsely observed, assessment of model skill is often restricted to tracers that can be easily measured and assembled. Examination of the models' fit to climatologies of inorganic tracers, after the models have been spun up to steady state, is a common but computationally expensive procedure to assess model performance and reliability. Using new tools that have become available for global model assessment and calibration in steady state, this paper examines two different model types – a complex seven-component model (MOPS) and a very simple four-component model (RetroMOPS) – for their fit to dissolved quantities. Before comparing the models, a subset of their biogeochemical parameters has been optimised against annual-mean nutrients and oxygen. Both model types fit the observations almost equally well. The simple model contains only two nutrients: oxygen and dissolved organic phosphorus (DOP). Its misfit and large-scale tracer distributions are sensitive to the parameterisation of DOP production and decay. The spatio-temporal decoupling of nitrogen and oxygen, and processes involved in their uptake and release, renders oxygen and nitrate valuable tracers for model calibration. In addition, the non-conservative nature of these tracers (with respect to their upper boundary condition) introduces the global bias (fixed nitrogen and oxygen inventory) as a useful additional constraint on model parameters. Dissolved organic phosphorus at the surface behaves antagonistically to phosphate, and suggests that observations of this tracer – although difficult to measure – may be an important asset for model calibration.

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Patel, Tejal L., and Prachi G. Shah. "Management of post-partum haemorhage at tertiary care center." International Journal of Reproduction, Contraception, Obstetrics and Gynecology 12, no. 2 (January 20, 2023): 354–59. http://dx.doi.org/10.18203/2320-1770.ijrcog20230037.

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Background: In developing countries like India post-partum haemorrhage (PPH) contributes to 35% of all maternal deaths and 239 per 1,00,000 deaths. So, PPH is a high-risk condition which increases maternal morbidities and mortalities. Hence it mandates a multidisciplinary approach. Audit of misses and near misses helps to determine causes of maternal morbidity and mortality and identify gaps in care. Aim of the study was to study conservative and definitive management of PPH. Methods: A retrospective analysis of all patients who has undergone PPH and also cases who referred from outside with PPH in department of obstetrics and gynaecology at civil hospital Ahmedabad from January 2021 to January 2022. Results: Out of 6029 deliveries there were 171 cases of PPH (2.8%). Which of 150 cases (87.7%) managed by conservative management (uterine conserving) and 21 (12.3%) cases were required definitive management (hysterectomy) due to failure of conservative management. Out of all cases 78.8% cases of PPH were due to atonicity of uterus and 19.1% cases were due to traumatic cause. Early recourse to hysterectomy was recommended especially where bleeding is associated with morbidly adherent placenta. Conclusions: PPH is an important cause of morbidity and mortality. We now have more options for conservative management which can greatly reduce its sequelae and more importantly in patients with wider issues of reproductive health. But in case of intractable bleeding and non-responsive by conservative management definitive management (Hysterectomy) is life saving and last resource.

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Bai, Chunmei, and Yusong Li. "Time series analysis of contaminant transport in the subsurface: Applications to conservative tracer and engineered nanomaterials." Journal of Contaminant Hydrology 164 (August 2014): 153–62. http://dx.doi.org/10.1016/j.jconhyd.2014.06.002.

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Perez-Cornago, Aurora, Almudena Sanchez-Villegas, Maira Bes-Rastrollo, Alfredo Gea, Patricio Molero, Francisca Lahortiga-Ramos, and Miguel Ángel Martinez-Gonzalez. "Relationship between adherence to Dietary Approaches to Stop Hypertension (DASH) diet indices and incidence of depression during up to 8 years of follow-up." Public Health Nutrition 20, no. 13 (June 23, 2016): 2383–92. http://dx.doi.org/10.1017/s1368980016001531.

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AbstractObjectiveOur aim was to evaluate the relationship between adherence to different Dietary Approaches to Stop Hypertension (DASH) diet indices and the risk of depression.DesignIn a prospective study we assessed 14051 participants of a dynamic (permanently ongoing recruitment) prospective cohort (the Seguimiento Universidad de Navarra (SUN) Project), initially free of depression. At baseline, a validated FFQ was used to assess adherence to four previously proposed DASH indices (Dixon, Mellen, Fung and Günther). To define the outcome we applied two definitions of depression: a less conservative definition including only self-reported physician-diagnosed depression (410 incident cases) and a more conservative definition that required both clinical diagnosis of depression and use of antidepressants (113 incident cases). Cox regression and restricted cubic splines analyses were performed.ResultsAfter a median follow-up period of 8 years, the multiple-adjusted model showed an inverse association with the Fung DASH score (hazard ratio (HR)=0·76; 95 % CI 0·61, 0·94) when we used the less conservative definition of depression, and also under the more conservative definition (HR=0·63; 95 % CI 0·41, 0·95). We observed a weak inverse association with the Mellen DASH score, but no statistically significant association was found for the other definitions. The restricted cubic splines analyses suggested that these associations were non-linear (U-shaped).ConclusionsModerate adherence to the DASH diet as operationalized by Fung and Mellen was related to lower depression risk. Since these associations were non-linear, additional prospective studies are required before the results can be generalized and clinical recommendations can be given.

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Lai, Keith C. K., Irene M. C. Lo, and Peter Kjeldsen. "Natural Gradient Tracer Test for a Permeable Reactive Barrier in Denmark. II: Spatial Moments Analysis and Dispersion of Conservative Tracer." Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management 10, no. 4 (October 2006): 245–55. http://dx.doi.org/10.1061/(asce)1090-025x(2006)10:4(245).

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Zhang, Peng, Rui Wang, Zhijun Li, Yuhan Wang, Chunshi Gao, Xin Lv, Yuanyuan Song, and Bo Li. "The risk of smoking on multiple sclerosis: a meta-analysis based on 20,626 cases from case-control and cohort studies." PeerJ 4 (March 15, 2016): e1797. http://dx.doi.org/10.7717/peerj.1797.

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Background.Multiple sclerosis (MS) has become a disease that represents a tremendous burden on patients, families, and societies. The exact etiology of MS is still unclear, but it is believed that a combination of genetic and environmental factors contribute to this disease. Although some meta-analyses on the association between smoking and MS have been previously published, a number of new studies with larger population data have published since then. Consequently, these additional critical articles need to be taken into consideration.Method.We reviewed articles by searching in PubMed and EMBASE. Both conservative and non-conservative models were used to investigate the association between smoking and the susceptibility to MS. We also explored the effect of smoking on the susceptibility to MS in strata of different genders and smoking habits. The association between passive smoking and MS was also explored.Results.The results of this study suggest that smoking is a risk factor for MS (conservative model: odds ratio (OR) 1.55, 95% CI [1.48–1.62],p< 0.001; non-conservative model: 1.57, 95% CI [1.50–1.64],p< 0.001). Smoking appears to increase the risk of MS more in men than in women and in current smokers more than in past smokers. People who exposed to passive smoking have higher risk of MS than those unexposed.Conclusion.This study demonstrated that exposure to smoking is an important risk factor for MS. People will benefit from smoking cessation, and policymakers should pay attention to the association between smoking and MS.

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Journal articles on the topic 'Conservative and non-conservative environmental tracers'

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