Academic literature on the topic 'Geosmin (GSM)'

Abstract A new electrochemical sensor based on molecular imprinting technology was developed, for rapid and sensitive detection of the odorous substance geosmin (GSM) in water. In this method, the molecularly imprinted membrane was successfully modified on the surface of the glassy carbon electrode (GCE) using the electrochemical deposition method. In the presence of the target analyte (geosmin), the target analyte occupies the detection site and the detection signal will attenuate. As the concentration of the target analyte increases, the attenuation of the electrical signal becomes more pronounced. This sensor can quantitatively detect geosmin at concentrations as low as 5 ng/L, which is currently the lowest limit of detection (LOD) for GSM detection by an electrochemical sensor in reported studies. The modified GCE provided an analytical curve for GSM detection in the range of 5–200 ng/L.

This study was conducted to obtain the basic data of two common odorants—geosmin and 2-methylisoborneol (GSM and 2-MIB)—in environmental water. More specifically, the headspace solid-phase microextraction coupled to gas chromatography mass spectrometry (HS-SPME/GC-MS) was applied to determine the levels of GSM and 2-MIB in water samples, and the samples were collected depending on water sources, conventional treatment processes, and seasons. The significant difference was shown for the 2-MIB levels of source waterP<0.05, the concentrations of GSM and 2-MIB decreased significantly as treatment process of tap water moved forward(P<0.0001), and the significant differences for the levels of GSM and 2-MIB were observed among three sampling periods(P<0.01). The levels of GSM and 2-MIB in all water samples were lower than 10 ng L−1, the odor threshold concentration (OTC), and the conventional treatment process plays a significant role in removing odorants in tap water.

Understanding water quality events in a multiple-impoundment series is important but seldom presented comprehensively. Therefore, this study was conducted to systematically understand the explosion event of geosmin (GSM) in the North Han River (Chuncheon, Soyang, Euiam, and Cheongpyeong Reservoirs) and Han River (Paldang Reservoir), which consists of a cascade reservoir series, the largest drinking water source system in South Korea. We investigated the spatiotemporal relationship of harmful cyanobacterial blooms in the upstream reservoir (Euiam) with the water quality incident event caused by the GSM in the downstream reservoir (Paldang) from January to December 2011. The harmful cyanobacterial bloom occurred during August–September under a high water temperature (>20 °C) after a heavy-rainfall-based flood runoff event. The high chlorophyll-a (Chl-a) concentration in the upper Euiam Reservoir was prolonged for two months with a maximum concentration of 1150.5 mg m−3, in which the filamentous Dolichospermum circinale Kütz dominated the algal community at a rate of >99%. These parameters remarkably decreased (17.3 mg Chl-a m−3) in October 2011 when the water temperature decreased (5 °C) and soluble reactive phosphorus was depleted. However, high and unprecedented GSM concentrations, with a maximum value of 1640 ng L−1, were detected in the downstream reservoirs (Cheongpyeong and Paldang); the level was 11 times higher than the value (10 ng L−1) recommended by the World Health Organization. The concentrations of GSM gradually decreased and had an adverse effect on the drinking water quality until the end of December 2011. Our study indicated that the time lag between the summer–fall cyanobacterial outbreak in the upstream reservoir and winter GSM explosion events in the downstream reservoirs could be attributed to the transport and release of GSM through the effluent from hydroelectric power generation in this multiple-reservoir system. Therefore, we suggest that a structural understanding of the reservoir cascade be considered during water quality management of drinking water sources to avoid such incidents in the future.

Geosmin (GSM) and 2-methylisoborneol (MIB)-induced off-flavors can cause serious problems in a recirculating aquaculture system (RAS), such as delayed harvest and increased production costs, but also damage producers’ reputation. Traditionally, off-flavors have been removed by depuration before harvesting. Rainbow trout (Oncorhynchus mykiss) and European whitefish (Coregonus lavaretus) are commercially valuable species produced for consumers, both being suitable for rearing in RAS. In this study, European whitefish and rainbow trout were raised from juvenile up to 240 g (European whitefish) and 660 g (rainbow trout) to monitor the long-term accumulation of off-flavors. The concentrations in fillet of rainbow trout reached 3.6 ng·g−1 (MIB) and 5.6 ng∙g−11 (GSM) with lipid content of 22.5%, while for European whitefish up to 3.2 ng·g−1 (MIB) and 3.9 ng·g−1 (GSM) were found with 14.8% in lipid content. Concentrations up to 58 ng·L−1 (MIB) and 49 ng·L−1 (GSM) were found in the circulating water. Based on the results, the accumulation of MIB proceeds at similar pace for both species. In the case of GSM, the accumulation started similarly for both species but proceeded more quickly for rainbow trout after 140 days of the experiment, with a statistically significant difference (p < 0.05).

Nanofiltration (NF) has been shown to be an effective way of removing organic micropollutants from drinking water due to its size exclusion properties. A rapid bench scale membrane test unit was utilised to trial six NF membranes to remove the algal metabolites, microcystin, cylindrospermopsin, 2-methylisoborneol (MIB) and geosmin (GSM). Membrane fouling due to the algal metabolites was observed for both charged and neutral metabolites. MIB and GSM were removed effectively by low molecular weight cut-off (MWCO) membranes but less effectively by a higher MWCO membrane. Removal of MIB and GSM by the higher MWCO membrane was improved as the membrane fouled. Microcystin was initially removed to above 90% by tight NF membranes but fouling of several membranes caused decreased percent removals over time. Tight NF membranes afforded removals of 90–100% for cylindrospermopsin, while removal by the higher MWCO membrane was lower but improved with time due to fouling.

The objective of our study was to survey the accumulated 2-methylisoborneol (MIB) and geosmin (GSM) in fillets of five important farmed fish species in Hungarian aquaculture in relation to MIB and GSM concentrations in water and sediment in the aquatic systems where they were raised: (the planktivorous silver carp (Hypophthalmichthys molitrix), the herbivorous grass carp (Ctenopharyngodon idella), the bottom-feeding omnivorous common carp (Cyprinus carpio), the omnivorous tilapia (Oreochromis niloticus) and the carnivorous African catfish (Clarias gariepinus)). Water, sediment and fish samples were collected from different experimental aquatic systems which included a combined aquaculture–algae (CAA) system, effluent-fed fishponds, a pond recycling system and a traditional fishpond. MIB and GSM contents were extracted with distillation-headspace solid-phase – microextraction (SPME) and extracts analysed by GC-MS. Results showed that off-flavour contents in fish fillets were related to the feeding habits of the studied fish species. Higher GSM concentrations were found in the fillet of bottom-feeding common carp than in the silver carp or African catfish in all studied aquatic systems. Usually, low GSM concentrations were detected in the water of fishponds but sometimes the levels of this odour compound in carp fillet were well above the limits of human detection. This suggests that the off-flavour tainting of common carp may originate from the sediment or benthic algal/actinomycete sources. Negligible MIB levels were found in all samples in all of the studied aquatic systems.

Aquaponics is a technique where a recirculating aquaculture system (RAS) and hydroponics are integrated to grow plants and fish in a closed system. We investigated if the growth of rainbow trout (Oncorhynchus mykiss) and baby spinach (Spinacia oleracea) would be affected in a coupled aquaponic system compared to the growth of the fish in RAS or plants in a hydroponic system, all systems as three replicates. We also investigated the possible effects of plants on the onset of nitrification in biofilters and on the concentration of off-flavor-causing agents geosmin (GSM) and 2-methylisoborneol (MIB) in rainbow trout flesh and spinach. For the fish grown in aquaponics, the weight gain and specific growth rates were higher, and the feed conversion ratio was lower than those grown in RAS. In spinach, there were no significant differences in growth between aquaponic and hydroponic treatments. The concentration of GSM was significantly higher in the roots and MIB in the shoots of spinach grown in aquaponics than in hydroponics. In fish, the concentrations of MIB did not differ, but the concentrations of GSM were lower in aquaponics than in RAS. The onset of nitrification was faster in the aquaponic system than in RAS. In conclusion, spinach grew equally well in aquaponics and hydroponic systems. However, the aquaponic system was better than RAS in terms of onset of nitrification, fish growth, and lower concentrations of GSM in fish flesh.

A simple, rapid, sensitive and high-efficiency method for determ-ination of odorous compounds such as 2-methylisobomeol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (Geosmin) in the source of drinking water was developed by solid-phase microe- xtraction(SPME) followed by gas chromatography-mass spectrometry(GC-MS). In this study, various of SPME conditions have been optimized in detail. The results show that DVB/CAR/ PDMS fiber was found to possess the best extraction efficiency for the odorous compounds in water. SPME was carried out by using 25mL samples, addition of 6 g NaCl, stirring at 1150 rpm and temperature at 80°C for 15 min to enrich the target analytes. After that, the fiber was desorbed at 250°C for 2min and determined by GC-MS. 2-MIB and GSM were separated within 15 min using a HP-5MS capillary column and detected in the selective ion monitoring mode. The optimized method has been proved with excellent linearity and precision. Using this method, the calibration curves of 2-MIB and GSM were linear in the range of 10-500 ng/L, and the correlation coefficients were both above 0.9984. The detection limits (S/N=3) of 2-MIB and GSM were 1.2 and 0.9 ng/L, respectively. The optimized SPME was proved to be a very practical method for determination of the trace odorous compounds in the source of drinking water and applied with satisfactory results.

Abstract Adsorption was found to be an acceptable treatment option to remove geosmin (GSM) and 2-methylisoborneol (2-MIB). It is meaningful to investigate the adsorption capacity of granular activated carbon (GAC) for the two algal odorants in water, and the influences of natural organic material (NOM) and particle size. The adsorption process was studied with the four isotherm models (Langmuir, Freundlich, Temkin, and modified Freundlich), four kinetic models (pseudo first-order, pseudo second-order, Elovich, and intra-particle), and thermodynamics. The results showed that the adsorption of both compounds could be best described by the modified Freundlich isotherm and pseudo second-order model, and the obtained thermodynamic parameters (changes in heat of adsorption, entropy, and Gibbs free energy) revealed that the adsorption was endothermic and spontaneous. Downsizing the particle size of GAC was effective for improving the adsorption capacity and rate. The concentrations of the two odorants could be reduced from 500 ng L−1 to less than 10 ng L−1 with the presence of NOM (&lt;20 mg L−1 total organic carbon, TOC).

Abstract As the water diversion reservoir showed high organic matter and high algae in summer, the potassium permanganate pre-oxidation/dissolved air flotation/carbon sand double filter process was developed. The test results show that the optimum operation conditions of the combined process were as follows: the dosage of KMnO4 was 0.3 mg/L, the dosage of polymeric aluminum ferric chloride (PAFC) was 3.0 mg/L (Al3+), the reflux ratio was 10%, and the dissolved gas pressure was 0.3 Mpa. Taking Ji'nan Queshan reservoir water algae pollution as the research object, the average removal rate of chlorophyll a, blue-green algae, turbidity, particle number and total organic carbon (TOC) reached 66.64%, 95.44%, 94.45%, 99.34% and 46.68%, respectively; the methylisoborneol (MIB) removal rate was 92.47%, the odor level decreased with process flow from raw water level 4 to effluent level 1.5, geosmin (GSM) dropped below the detection limit, and the total removal rate of trihalomethane formation potential (THMFP) was 33.56%. The effluent of the combined process meets the requirements of the Hygienic Standard for Drinking Water (GB5749-2006) after it is disinfected.

Fish farming with Recirculating Aquaculture Systems (RAS) is becoming widespread to fill the demand gap due to diminishing wild caught sea foods. Barramundi fish has a high demand as a premium Australian seafood, and is grown as an RAS farmed-fish. However, the accumulation of ‘earthy’ or ‘muddy’ off-flavours due to taint accumulation as geosmin (GSM) or 2-methylisoborneol (MIB) in the fish-flesh of is a major concern. Inconsistent quality of farmed barramundi has been identified as a major issue in buyer resistance. Established predictive models for chemical taint in fish-flesh have been based on steady-state assumptions. However, it was thought debatable as to whether a steady-state assumption could be upheld i.e. there was no evidence that the net chemicals exchange is zero across the fish body and RAS water phase. Against this background, an original, new and quantitative model that predicts the time dependent concentration of taste-taint chemicals as GSM and MIB in harvested fish-flesh was developed (Hathurusingha & Davey, 2013; Hathurusingha & Davey, 2014; Davey & Hathurusingha, 2014). This model is based on conservation of mass and energy, and thermodynamic processes established in (bio)chemical engineering with chemical uptake and elimination routes into and from the fish considered. The model was simulated for two RAS species, barramundi (Lates calcarifer) and rainbow trout (Onchorhynchus mykiss) with independent data (n ≥ 14) and showed good agreement with experimental observations. A major benefit of this new model is that simulations can be used to investigate a range of growth protocols in RAS farming to minimize taint in fish-flesh. An advantage is that it can readily be simulated in standard spread-sheeting tools by users with a range of sophistication. Extensive experimental testing of the new model was carried out in both pilot- and commercial-scale plants using low concentrations (≤ 10 mg L⁻¹) of hydrogen peroxide (H₂O₂) as a benign biocide to limit natural occurring taste-taint chemicals in the RAS growth water, and subsequently into the fish-flesh. A dedicated methodology and new dosing apparatus (ProMinent Fluid Control Pty Ltd, Germany) for controlled H₂O₂ dosing was developed. The analyses of taste-taint chemicals as GSM and MIB in water and fish-flesh was carried out with Solid-Phase Micro-Extraction (SPME) followed by Gas Chromatography Mass spectroscopy (GC-MS) (skills training was obtained at both the University of Laval and University of Waterloo, Canada). Preliminary investigations with a low concentration of H₂O₂ (5 mg L⁻¹) in pilot-scale (2,500 L) studies with barramundi fish demonstrated its potential to mitigate development of GSM and MIB in RAS water. It was found that controlled dosing of low concentrations of H₂O₂ did not impact the pH level in growth waters and was not detrimental to the health and well-being of the fish as fingerlings (0.01 kg) and until harvest at 240 days (0.8 kg). Additional benefits of H₂O₂ as benign biocide include a fish product of whiter colour, an increased dissolved oxygen concentration (Cₒₓ) in the growth water, a reduction in the number of gill flukes, and improved particles distribution with increased C:N ratio, and; improved availability of organic carbon in the growth water. Based on these preliminary investigations H₂O₂ was ‘optimised’ at a (low) concentration of 2.5 mg L⁻¹ as a benign biocide. This was investigated in commercial-scale studies (conducted at Barra Fresh Farm, South Australia) for a typical growth of 240 day for barramundi as the selected RAS fish. The emerging risk methodology of Davey and co-workers (e.g. Chandrakash et al., 2015) was applied for the first time to investigate quantitatively the impact of naturally occurring fluctuations in taste-taint chemicals in the RAS water and their accumulation in the fish-flesh. This predictive approach was justified because of the prohibitively expensive time and analytical costs that experimental studies would have necessitated. A Refined Monte Carlo (with Latin Hypercube) simulation of GSM and MIB in the growth water (Cᴡ), water temperature (T) and growth time (t) was used to simulate typical RAS farmed barramundi. It was found in RAS farming of barramundi it would be expected some 10.10 % of all 240 day harvests, averaged over the long term, would result in fish with taste-taint as GSM above the desired consumer rejection threshold concentration (0.74 μg kg⁻¹) due to natural fluctuations in an uncontrolled RAS environment. For MIB this predicted failure rate was 10.56 % (Hathurusingha & Davey, 2016). The vulnerability to taste-taint failure as GSM and MIB was shown to be principally controlled by the time to fish harvest, and to a lesser extent by concentration and fluctuation of these taint chemicals in the RAS water. This work was of practical benefit because growth time can be readily controlled by farmers. The methodology appears generalizable and therefore is applicable to a range of RAS farmed fish (and possible crustaceans e.g. prawns- Macrobrachium sp.). In extensive commercial-scale RAS studies with barramundi and controlled H2O2 dosing, fish grown from fingerlings to harvest at 240 day was investigated. This was to observe an entire production cycle. Results from a H₂O₂ ‘treated’ growth tank (30,000 L) were compared directly with those obtained from an identical ‘control’ tank (30,000 L). Increased organic matter (three (3) to four (4) times pilot-scale findings) reduced H₂O₂ efficacy through inhibiting generation of reactive oxygen species (ROSs). This is thought to be a consequence of the need to scale (48 times volume) the pilot-scale studies for in-tank mixing. Analyses of fish-flesh (n ≥ 167) showed (moderate) predicted exponential correlation between taste-taint concentrations in the fish-flesh and the growth-mass of the fish for both GSM and MIB as predicted. In addition, the research findings highlighted that accumulation of taste-taint compounds was mainly governed by the combined effect of mass of the fish (mᵳ) and taste-taint concentrations in the growth water (Cᴡ). Comparisons between the model predictions and experimental observations showed good agreement over the range of low taste-taint concentration (0 to 2, μg kg⁻¹), especially below the consumer rejection threshold (~ 0.7 μg kg⁻¹). However, a minor anomaly was an over-prediction for greater concentrations (2 to 11, μg kg⁻¹). Current predictions are therefore conservative or ‘safe’ by about 20 %. Possible reasons for over prediction might be attributed to rapid fluctuation of taste-taint concentration in growth water with growth time and different (exponential) growth constants shown by larger and smaller fish, and; errors in obtaining representative samples from fish-flesh. Model predictions and experiments further highlighted that the new model could be meaningfully applied to RAS systems with lower variations and/or lower taste-taint concentrations in RAS growth water. These theoretical and experimental results are the first for RAS farmed fish covering an entire production period to harvest. Approval for this research was gained from both The University of Adelaide Animal Ethics Committee Science and, Australian Pesticides and Veterinary Medicines Authority (see Appendices F and G). Research findings will be of immediate benefit to RAS farmers, fish processors and risk analysts in foods processing.
Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2016.

Indiana University-Purdue University Indianapolis (IUPUI)
Eagle Creek Reservoir (ECR), located in the Midwestern U.S., is a freshwater limnic system plagued by seasonal Harmful Algal Blooms (HABs) which generate water-fouling Geosmin (GSM) and 2-Methylisoborneol (MIB) Taste and Odor (T&O) compounds. Past investigations of T&O event dynamics have identified Actinomycetes as responsible for MIB production and several genera of cyanobacteria for GSM production. During 2018, a temporally and spatially expansive sampling regimen of the reservoir was carried out and a battery of biological, chemical, physical, and hyperspectral experiments performed. The resulting data was analyzed using time series, cross-correlation, lag time, and multivariate analyses as well as machine learning algorithms to pick apart and interrogate any relationships between HABs, T&O events, and environmental parameters. The results show that local weather and watershed conditions exert significant control over the state of the reservoir and the behavior of the algal community. GSM and MIB peaked during early May under well-mixed, cold, and nutrient-rich water column conditions, then declined under summer thermal stratification before making a small resurgence during late season mixing. Bloom die-off and decay was effectively ruled out as a mechanism controlling T&O concentrations, and no links were found between T&O concentrations and algal biomass. Strong evidence was found that GSM/MIB concentrations were a response by bloom microbes to changing nutrient conditions within the reservoir, and it was determined that nutrient fluxes from the watershed 30-40 days prior to peak T&O concentrations are likely instrumental in the development of the slow- ix growing microbes characteristic of the reservoir. Attempts were made to assess spatial and temporal variability but no significant spatial differences were identified; differences between sampling sites were far smaller than differences between different sampling dates. The findings here add to the growing body of literature showing T&O and HAB dynamics are more closely linked to the relative abundance and speciation of nutrients than other parameters. Additionally, these findings carry important implications for the management of ECR and other similar freshwater reservoirs while highlighting the importance of reducing watershed eutrophication.