Publications by authors named "Shannon Bartelt-Hunt"

80 Publications

Modeling the vertical transport of antibiotic resistance genes in agricultural soils following manure application.

Environ Pollut 2021 Sep 29;285:117480. Epub 2021 May 29.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, United States. Electronic address:

Antibiotic resistance genes (ARGs) may be introduced to agricultural soil through the land application of cattle manure. During a rainfall event, manure-borne ARGs may infiltrate into subsurface soil and leach into groundwater. The objective of this study was to characterize and model the vertical transport of manure-borne ARGs through soil following the land application of beef cattle manure on soil surface. In this study, soil column experiments were conducted to evaluate the influence of manure application on subsurface transport of four ARGs: erm(C), erm(F), tet(O) and tet(Q). An attachment-detachment model with the decay of ARGs in the soil was used to simulate the breakthrough of ARGs in leachates from the control column (without manure) and treatment (with manure) soil columns. Results showed that the first-order attachment coefficient (k) was five to six orders of magnitude higher in the treatment column than in the control column. Conversely, the first-order detachment and decay coefficients (k and μ) were not significantly changed due to manure application. These findings suggest that in areas where manure is land-applied, some manure-borne bacteria-associated ARGs will be attached to the soil, instead of leaching to groundwater in near terms.
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http://dx.doi.org/10.1016/j.envpol.2021.117480DOI Listing
September 2021

Stockpiling versus Composting: Effectiveness in Reducing Antibiotic-Resistant Bacteria and Resistance Genes in Beef Cattle Manure.

Appl Environ Microbiol 2021 07 27;87(16):e0075021. Epub 2021 Jul 27.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.

Manure storage methods can affect the concentration and prevalence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in cattle manure prior to land application. The objective of this study was to compare stockpiling and composting with respect to their effectiveness in reducing ARB and ARGs in beef cattle manure in a field-scale study. Field experiments were conducted in different seasons with different bulking agents for composting. For both the winter-spring cycle and the summer-fall cycle, ARB concentrations declined below the limit of quantification rapidly in both composting piles and stockpiles; however, ARB prevalence was significantly greater in the composting piles than in the stockpiles. This was likely due to the introduction of ARB from bulking agents. There was no significant change in ARG concentrations between initial and final concentrations for either manure storage treatment during the winter-spring cycle, but a significant reduction of the ARGs (B), (O), and (Q) over time was observed for both the composting pile and stockpile during the summer-fall cycle. Results from this study suggest that (i) bulking agent may be an important source of ARB and ARGs for composting; (ii) during cold months, the heterogeneity of the temperature profile in composting piles could result in poor ARG reduction; and (iii) during warm months, both stockpiling and composting can be effective in reducing ARG abundance. Proper treatment of manure is essential to reduce the spread of antibiotic resistance and protect human health. Stockpiling and composting are two manure storage methods which can reduce antibiotic-resistant bacteria and resistance genes, although few field-scale studies have examined the relative efficiency of each method. This study examined the ability of both methods in both winter-spring and summer-fall cycles, while also accounting for heterogeneity within field-scale manure piles. This study determined that bulking agents used in composting could contribute antibiotic-resistant bacteria and resistance genes. Additionally, seasonal variation could hinder the efficacy of composting in colder months due to heterogeneity in temperature within the pile; however, in warmer months, either method of manure storage could be effective in reducing the spread of antibiotic resistance.
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http://dx.doi.org/10.1128/AEM.00750-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8315184PMC
July 2021

Surface and Groundwater Contamination, Community and Ecosystem Exposures Are the Unintentional Consequences from "Recycling" Treated Seed Products.

Environ Sci Technol 2021 05 15;55(9):5605-5607. Epub 2021 Apr 15.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Omaha, Nebraska 68182, United States.

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http://dx.doi.org/10.1021/acs.est.1c01305DOI Listing
May 2021

Nitrogen removal in vermifiltration: Mechanisms, influencing factors, and future research needs.

J Environ Manage 2021 Mar 30;281:111868. Epub 2020 Dec 30.

Nebraska Water Center, University of Nebraska-Lincoln, NE, USA; Daugherty Water for Food Global Institute, University of Nebraska-Lincoln, NE, USA; Dept. of Civil and Environmental Engineering, University of Nebraska-Lincoln, NE, USA. Electronic address:

To meet global health and sanitation goals, there is a continued need for sustainable wastewater treatment alternatives that require minimal energy and investment. Vermifiltration, a technology gaining relevance in Africa and Asia, may be an alternative to traditional wastewater treatment systems due to its cost-effectiveness, ease of application and maintenance, and sustainability. However, nitrogen removal in vermifiltration is not well understood since most of the prior research focuses on organics removal. Thus, a state of the art review is necessary to separately focus on the mechanisms associated with nitrogen removal in vermifiltration, along with the factors affecting nitrogen removal. For the first time, this review attempts to present the types of vermifilter based on their flow pattern. The review further discusses the current status of the application of vermifiltration, along with the benefits and limitations associated with the adoption of this technology. It also explores possible strategies that could be adopted to maximize the nitrogen removal potential of vermifilters as optimizing nitrogen removal is critical for improving the performance of vermifiltration based treatment systems.
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http://dx.doi.org/10.1016/j.jenvman.2020.111868DOI Listing
March 2021

Real-world activity, fuel use, and emissions of heavy-duty compressed natural gas refuse trucks.

Sci Total Environ 2021 Mar 5;761:143323. Epub 2020 Nov 5.

Department of Civil Engineering, University of Nebraska-Lincoln, Omaha, NE 68182-0178, United States of America. Electronic address:

Over 50% of new refuse truck sales have been compressed natural gas (CNG). Compared to diesel, CNG is less expensive on diesel gallon equivalent (dge) basis. This study quantifies the real-world fuel use and tailpipe exhaust emissions from three front- and three side-loader refuse trucks, each with a spark ignition CNG engine, three-way catalyst, and similar gross weight. Measurements were made at 1 Hz using a portable emissions measurement system (PEMS). Inter-cycle and inter-vehicle variability is quantified. Effect of vehicle weight was analyzed and comparisons were made with MOVES predicted cycle average emission rates. In total, about 220,000 s of data covering 490 miles of operation were recorded. The average fuel economy was 1.9 miles per dge. On average the trucks spent 53% of time in idle, which includes trash collection activity. The average speeds were 10 mph and 5 mph, for front- and side-loader trucks, respectively. Overall, compared to side-loader trucks, front-loader trucks had 55% better fuel economy and 60% lower emission rates. Compared to diesel trucks, CNG truck cycle average NO and PM emission rates, at 1.2 g/mile and 0.006 g/mile respectively, were substantially lower while CO and HC rates, at 29 g/mile and 6 g/mile respectively, were considerably higher. Fuel use and CO emissions rates increased by 10% due to increase in truck weight during trash collection, while CO emissions rates increased by up to 30%. Compared to measured values, MOVES estimated cycle average fuel use and CO emissions were 25% lower, CO emissions are 70% lower, and NO emissions were 200% higher. Results from this study can be used to improve solid waste life cycle and tailpipe emission factor models and, when combined with previous studies on diesel refuse trucks, evaluate the effect on fuel use and emissions from adoption of CNG refuse trucks.
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http://dx.doi.org/10.1016/j.scitotenv.2020.143323DOI Listing
March 2021

Evaluation of depth-dependent properties of municipal solid waste using a large diameter-borehole sampling method.

J Air Waste Manag Assoc 2021 04 23;71(4):433-446. Epub 2020 Dec 23.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Omaha, NE, USA.

This study is to analyze geotechnical properties and biological status of undisturbed municipal solid waste (MSW) associated with depth by using a large-diameter borehole sampling method. Through the method, a 28 m-borehole with 0.8 m of the diameter was drilled into the MSW body consisting of ten-lift layers of waste placed over 4000 days in an operating landfill. MSW sample cuttings were collected from the field site, weighted, and transferred to a laboratory for additional experiments to measure various properties such as moisture content, constituent characterization, unit weights, specific gravity, decomposition state, saturation, and compression rates with regard to waste depth. Also, the methane production obtained from MSW decomposition tests indicated that waste mass was relatively consistent throughout the depth of borehole and had not reached the accelerated production phase of methane. The wet and dry unit weights of the MSW sample with different depths produced excellent trends of the first-order rate with vertical stress. First Oder Rate Equation (FORE) analysis indicated that the maximum total and dry unit weight of MSW ( and ) achieved at depth in the waste mass were 12.9 kN/m and 10.6 kN/m, respectively. Based on the waste shrinkage ratio (WSR) defined as the initial dry unit weight divided by succeeding dry unit weight, the height of the original MSW pile was estimated to be 40.5 m. Different compression parameters, including aggregated MSW compression index (C), modified compression index (C), and compression ratio parameter (C'), were comparably evaluated, which can be beneficial to understand compressibility and settlement processes in a landfill.: Geotechnical properties and biological status of undisturbed municipal solid waste (MSW) associated with depth were analyzed by using a large-diameter borehole sampling method. The wet and dry unit weights of the MSW sample with different depths produced excellent trends of the first-order rate with vertical stress. Based on the waste shrinkage ratio (WSR) defined as the initial dry unit weight divided by succeeding dry unit weight, the height of the original MSW pile was estimated to be 40.5 m. Different compression parameters, including aggregated MSW compression index (C), modified compression index (C), and compression ratio parameter (C'), were comparably evaluated, which can be beneficial to understand compressibility and settlement processes in a landfill.
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http://dx.doi.org/10.1080/10962247.2020.1848942DOI Listing
April 2021

Antibiotic resistance genes in swine manure slurry as affected by pit additives and facility disinfectants.

Sci Total Environ 2021 Mar 3;761:143287. Epub 2020 Nov 3.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States. Electronic address:

Manure storage facilities are critical control points to reduce antibiotic resistance genes (ARGs) in swine manure slurry before the slurry is land applied. However, little is known about how exogenous chemicals entering the manure storage facilities may affect the fate of ARGs. The objective of this study was to analyze the impact of six commonly used pit additives and four facility disinfectants on the concentration of ARGs in swine manure slurry. Bench scale reactors, each containing approximately 50 L of liquid swine manure, were dosed with additives or disinfectants and were sampled for 40 days. Seven antibiotic resistance genes along with the intI1 gene and the 16S rRNA gene were monitored. Out of the six additives tested, Sludge Away significantly reduced the time-averaged absolute abundance of erm(C), erm(F), tet(Q), and the 16S rRNA gene as compared to the no additive control. Out of the four disinfectants tested, Tek-Trol significantly reduced the time-averaged absolute abundance of erm(B), erm(C), erm(F), intI1, tet(Q), and tet(X) than did the no-disinfectant control. According to Spearman's rank correlation, three genes erm(F), tet(Q), and tet(X) showed a strong to perfectly positive correlation and the two genes erm(B) and tet(O) showed a moderate to strong correlation in both the additive and disinfectant tests. Overall, the disinfectants were more effective in controlling the absolute abundance of ARGs than were the pit additives.
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http://dx.doi.org/10.1016/j.scitotenv.2020.143287DOI Listing
March 2021

Climate change impacts the subsurface transport of atrazine and estrone originating from agricultural production activities.

Environ Pollut 2020 Oct 18;265(Pt A):115024. Epub 2020 Jun 18.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, United States. Electronic address:

Climate change will impact soil properties such as soil moisture, organic carbon and temperature and changes in these properties will influence the sorption, biodegradation and leaching of trace organic contaminants to groundwater. In this study, we conducted a modeling case study to evaluate atrazine and estrone transport in the subsurface under current and future climate conditions at a field site in central Nebraska. According to the modeling results, in the future, enhanced evapotranspiration and increased average air temperature may cause drier soil conditions, which consequently reduces the biodegradation of atrazine and estrone in the water phase. On the other hand, greater transpiration rates lead to greater root solute uptake which may decrease the concentration of atrazine and estrone in the soil profile. Another consequence of future climate is that the infiltration and leaching rates for both atrazine and estrone may be lower under future climate scenarios. Reduced infiltration of trace organic compounds may indicate that lower trace organic concentrations in groundwater may occur under future climate scenarios.
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http://dx.doi.org/10.1016/j.envpol.2020.115024DOI Listing
October 2020

Measuring the occurrence of antibiotics in surface water adjacent to cattle grazing areas using passive samplers.

Sci Total Environ 2020 Jul 1;726:138296. Epub 2020 Apr 1.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-6105, USA. Electronic address:

A wide variety of antibiotics and other pharmaceuticals are used in livestock production systems and residues passed to the environment, often unmetabolized, after use and excretion. Antibiotic residues may be transported from manure-treated soils via runoff and are also capable of reaching surface and groundwater systems through a variety of pathways. The occurrence and persistence of antibiotics in the environment is a concern due to the potential for ecological effects and proliferation of environmental antibiotic resistance in pathogenic organisms. In the present study, the occurrence and seasonal variation of 24 commonly-used veterinary antibiotics was evaluated in surface water adjacent to several livestock production systems using Polar Organic Chemical Integrative Samplers (POCIS). Uptake rates for all compounds, nine of which have not been previously reported, were measured in the laboratory to permit estimation of changes in the time-weighted average (TWA) antibiotic concentrations during exposure. The antibiotics detected in POCIS extracts included sulfadimethoxine, sulfamethoxazole, trimethoprim, sulfamerazine, sulfadiazine, lincomycin, erythromycin, erythromycin anhydro- and monensin. The maximum TWA concentration belonged to sulfadiazine (25 ng/L) in the August-September sampling period and coincided with the highest number of precipitation events. With the exception of monensin that showed an increase in concentration over the stream path, none of the detected antibiotics were prescribed to livestock at the facility. The detection of antibiotics not prescribed by the facility may be attributable to the environmental persistence of previously used antibiotics, transfer by wind from other nearby livestock production sites or industrial uses, and/or the natural production of some antibiotics.
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http://dx.doi.org/10.1016/j.scitotenv.2020.138296DOI Listing
July 2020

Predicting Escherichia coli loads in cascading dams with machine learning: An integration of hydrometeorology, animal density and grazing pattern.

Sci Total Environ 2020 Jun 12;722:137894. Epub 2020 Mar 12.

Department of Biological Systems Engineering, University of Nebraska-Lincoln, 223 L. W. Chase Hall, Lincoln, NE 68583-0726, United States.

Accurate prediction of Escherichia coli contamination in surface waters is challenging due to considerable uncertainty in the physical, chemical and biological variables that control E. coli occurrence and sources in surface waters. This study proposes a novel approach by integrating hydro-climatic variables as well as animal density and grazing pattern in the feature selection modeling phase to increase E. coli prediction accuracy for two cascading dams at the US Meat Animal Research Center (USMARC), Nebraska. Predictive models were developed using regression techniques and an artificial neural network (ANN). Two adaptive neuro-fuzzy inference system (ANFIS) structures including subtractive clustering and fuzzy c-means (FCM) clustering were also used to develop models for predicting E. coli. The performances of the predictive models were evaluated and compared using root mean squared log error (RMSLE). Cross-validation and model performance results indicated that although the majority of models predicted E. coli accurately, ANFIS models resulted in fewer errors compared to the other models. The ANFIS models have the potential to be used to predict E. coli concentration for intervention plans and monitoring programs for cascading dams, and to implement effective best management practices for grazing and irrigation during the growing season.
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http://dx.doi.org/10.1016/j.scitotenv.2020.137894DOI Listing
June 2020

Influence of Setback Distance on Antibiotics and Antibiotic Resistance Genes in Runoff and Soil Following the Land Application of Swine Manure Slurry.

Environ Sci Technol 2020 04 1;54(8):4800-4809. Epub 2020 Apr 1.

Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.

The environmental spread of antibiotics and antibiotic resistance genes (ARGs) from the land application of livestock wastes can be a potential public health threat. The objective of this study was to assess the effects of setback distance, which determines how close manure may be applied in relation to surface water, on the transport of antibiotics and ARGs in runoff and soil following land application of swine manure slurry. Rainfall simulation tests were conducted on field plots covered with wheat residues, each of which contained an upslope manure region where slurry was applied and an adjacent downslope setback region that did not receive slurry. Results show that all three antibiotics (chlortetracycline, lincomycin, and tiamulin) and seven out of the ten genes tested ((B), (C), , (O), (Q), (X), and the 16S rRNA gene) decreased significantly in runoff with increased setback distance. Only , chlortetracycline, and tiamulin decreased significantly in surface soil with increased setback distance, while the other analytes did not exhibit statistically significant trends. By using linear regression models with field data, we estimate that a setback distance between 34-67 m may allow manure-borne antibiotics and ARGs in runoff to reach background levels under the experimental conditions tested.
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http://dx.doi.org/10.1021/acs.est.9b04834DOI Listing
April 2020

Swine slurry characteristics as affected by selected additives and disinfectants.

Environ Pollut 2020 May 25;260:114058. Epub 2020 Jan 25.

Nebraska Water Center, University of Nebraska, Lincoln, NE, United States.

Current swine industry practice is to house animals in confinement facilities which capture and store feces and urine as slurry in pits below the production area. Additives and disinfectants may be introduced into the manure pits. This study was conducted to measure the effects of additives and disinfectants on temporal changes in swine slurry characteristics. Slurry from a commercial swine production facility in southeast Nebraska, USA was collected and transferred to 57 L reactors located within a greenhouse. Selected additives and disinfectants were added to the reactors and physical properties, chemical characteristics, and antibiotic concentrations were monitored for 40 days. Concentrations of dry matter (DM), total nitrogen (TN), phosphorus pentoxide (PO), calcium (Ca), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu) were significantly greater than the Control in each of the reactors containing additives. The reactors in which the additives MOC-7, More Than Manure®, Sludge Away, and Sulfi-Doxx were introduced had significantly greater values of chemical oxygen demand (COD), total volatile solids (TVS), total suspended solids (TSS), total solids (TS), dry matter (DM), TN, PO, Ca, Mg, Zn, Fe, Mn, Cu and chlortetracycline than the other additive treatments. Concentrations of TVS and TSS were significantly lower in the reactors containing Clorox® and Virkon™ than the other disinfectant treatments. The total dissolved solids (TDS) concentration of 26,500 mg L and pH value of 7.27 obtained for the reactors containing Tek-Trol were significantly greater than measurements obtained for the other treatments. Concentrations of chlortetracycline and tiamulin of 8840 and 28.8 ng g, respectively, were significantly lower for the treatments containing Tek-Trol. The sodium (Na) concentration of 1070 mg L measured in the reactors containing Clorox® was significantly greater than values for the other disinfectant treatments. The introduction of selected additives and disinfectants may influence certain physical properties, chemical characteristics, and antibiotic concentrations of swine slurry.
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http://dx.doi.org/10.1016/j.envpol.2020.114058DOI Listing
May 2020

Fate and transport of antibiotics and antibiotic resistance genes in runoff and soil as affected by the timing of swine manure slurry application.

Sci Total Environ 2020 Apr 7;712:136505. Epub 2020 Jan 7.

Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States. Electronic address:

Land application of swine manure slurry is a common practice to supplement nutrients to soil for crop production. This practice can introduce antibiotic residues and antibiotic resistance genes (ARGs) into the environment. Field testing is critical in identifying manure management practices effective in minimizing the environmental impacts of manure-borne antibiotic and ARGs. The objective of this study was to determine how the timing of swine manure application relative to rainfall events impacts the fate and transport of antibiotics and ARGs in surface runoff and manure-amended soil. Swine manure slurry was either broadcast or injected on test plots in the field. A set of three 30-min simulated rainfall events, 24 h apart, were initiated on manured plots 1 day, 1 week, 2 weeks, or 3 weeks after the manure application. Results showed that an interval longer than 2 weeks between application and rainfall often significantly reduced the levels of antibiotics and ARGs tested in runoff with the exception of tet(X). For soil samples from broadcast plots, concentrations of two of the three antibiotics tested (lincomycin and tiamulin) decreased substantially in the first two weeks after manure application. In contrast, concentrations of most of the ARGs tested (tet(Q), tet(X), and erm(A)) in soil did not change significantly during the test period. Information obtained from the study can be beneficial in designing manure management practices and estimating the environmental loading of antibiotics and ARGs resulting from manure application.
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http://dx.doi.org/10.1016/j.scitotenv.2020.136505DOI Listing
April 2020

Escherichia coli concentrations in waters of a reservoir system impacted by cattle and migratory waterfowl.

Sci Total Environ 2020 Feb 29;705:135607. Epub 2019 Nov 29.

Biological Systems Engineering Department, University of Nebraska, Lincoln, United States of America.

Recent pathogenic Escherichia coli contamination of fresh vegetables that originated from irrigation water has increased awareness and importance of identifying sources of E. coli entering agroecosystems. However, inadequate methods for accurately predicting E. coli occurrence and sources in waterways continue to limit the identification of appropriate and effective prevention and treatment practices. Therefore, the primary objectives of this study were to: (1) Determine the concentration of E. coli during storm events in a hydrologic controlled stream situated in a livestock research operation that is located in the Central Flyway for avian migration in the United States. Great Plains; and (2) Identify trends between E. coli concentrations, grazing rotations, and avian migration patterns. The study sampled five rainfall events (three summer and two fall) to measure E. coli concentrations throughout storm events. A combination of cattle density and waterfowl migration patterns were found to significantly impact E. coli concentrations in the stream. Cattle density had a significant impact during the summer season (p < .0001), while waterfowl density had a significant impact on E. coli concentrations during the fall (p = .0422). The downstream reservoir had exceedance probabilities above the Environmental Protection Agency freshwater criteria > 85% of the growing season following rainfall events. Based on these findings, implementation of best management practices for reducing E. coli concentrations during the growing season and testing of irrigation water prior to application are recommended.
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http://dx.doi.org/10.1016/j.scitotenv.2019.135607DOI Listing
February 2020

Prediction of nitrate accumulation and leaching beneath groundwater irrigated corn fields in the Upper Platte basin under a future climate scenario.

Sci Total Environ 2019 Oct 1;685:514-526. Epub 2019 Jun 1.

Department of Civil Engineering, University of Nebraska-Lincoln, 844 N 16th St, Lincoln, NE 68508, USA. Electronic address:

Understanding the impacts of future climate change on soil hydrological processes and solute transport is crucial to develop appropriate strategies to minimize the adverse impacts of agricultural activities on groundwater quality. To evaluate the direct effects of climate change on the transport and accumulation of nitrate-N, we developed an integrated modeling framework combining climatic change, nitrate-N infiltration in the unsaturated zone, and groundwater level fluctuations. The study was based on a center-pivot irrigated corn field at the Nebraska Management Systems Evaluation Area (MSEA) site. Future groundwater recharge (GR) and actual evapotranspiration (ET) rates were predicted via an inverse vadose zone modeling approach by using climatic data generated by the Weather Research and Forecasting (WRF) climate model under the RCP 8.5 scenario, which was downscaled from the global CCSM4 model to a resolution of 24 km by 24 km. A groundwater flow model was first calibrated on the basis of historical groundwater table measurements and then applied to predict the future groundwater table in 2057-2060. Finally, the predicted future GR rate, ET rate, and groundwater level, together with future precipitation data from the WRF climate model, were used in a three-dimensional (3D) model to predict nitrate-N concentrations in the subsurface (saturated and unsaturated parts) from 2057 to 2060. The future GR was predicted to decrease in the study area, as compared with the average GR data from the literature. Correspondingly, the groundwater level was predicted to decrease (30 to 60 cm) over the 5 years of simulation in the future. The nitrate-N mass in the simulation domain was predicted to increase but at a slower rate than in the past. Sensitivity analysis indicated that the accumulation of nitrate-N is sensitive to groundwater table elevation changes and irrigation rates.
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http://dx.doi.org/10.1016/j.scitotenv.2019.05.417DOI Listing
October 2019

Enhanced biodegradation of atrazine at high infiltration rates in agricultural soils.

Environ Sci Process Impacts 2019 Jun;21(6):999-1010

Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.

The objective of this study was to assess the persistence and transport of atrazine at high infiltration rates expected from higher intensity precipitation associated with climate change scenarios in the midwestern U.S. The transport and transformation of atrazine was monitored in column experiments at high infiltration rates (64-119 mm d-1) associated with increased precipitation intensity. The optimum linear sorption and the lumped Monod biokinetic parameters were determined by inverting observed break-through curves (BTCs) using the advection-dispersion-sorption-degradation model. Batch microcosm studies were also conducted to examine the effect of moisture content (5%, 15% and 25%) on atrazine degradation and support the column results. BTCs from both soil types with continuous atrazine input showed a characteristic pattern of a pulse input i.e. lag phase prior to rapid atrazine degradation. The rate of atrazine leaching at higher infiltration rates was not fast enough to counteract the effect of enhanced degradation. Higher infiltration rates enriched the distribution of hydroxyatrazine in the soil profile for sandy loam, but their effect was minimal in loam soil. The pattern of degradation obtained in batch microcosms agreed with the column results. In both soils, mean half-life of atrazine was lower (4-8 days) at high soil moisture contents. Under future climate change scenarios, where more intense precipitation is likely to result in higher infiltration rates and increased soil moisture, the potential for groundwater pollution from atrazine may be reduced, especially in areas with a long history of atrazine application to soil.
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http://dx.doi.org/10.1039/c8em00594jDOI Listing
June 2019

Assessing the Accuracy of Citizen Scientist Reported Measurements for Agrichemical Contaminants.

Environ Sci Technol 2019 05 9;53(10):5633-5640. Epub 2019 May 9.

Department of Civil Engineering , University of Nebraska Lincoln , Omaha , Nebraska 68182 , United States.

Citizen science is a research tool capable of addressing major environmental challenges, including contamination of water resources by agrichemicals, such as nutrients and pesticides. The objectives of this study were (1) to identify the proportion of accurate observations by citizen scientists using rapid assessment water quality tools, and (2) to characterize how a user's prior experience with water quality tools was associated with the accuracy of citizen scientists. To achieve these objectives, we conducted group testing with over 136 citizen scientists and compared their results from water quality testing of water samples to results obtained using laboratory analytical methods. Following brief training, we observed that accuracy of reported results varies based on the user's experience level where experienced and expert users shared consistent and reliable measurements. Where erroneous measures were reported, citizen scientists tend to overestimate contaminant concentrations when using colorimetric water quality tools. Additionally, we identified differences in accuracy related to the types of water quality assessment tools used by citizen scientists from each experience group. This study demonstrates the importance of evaluating participant background experience in designing citizen science campaigns.
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http://dx.doi.org/10.1021/acs.est.8b06707DOI Listing
May 2019

Microbial communities in the rhizosphere and the root of lettuce as affected by Salmonella-contaminated irrigation water.

FEMS Microbiol Ecol 2018 09;94(9)

Department of Civil Engineering.

Reclaimed wastewater is increasingly used as a source of irrigation water in croplands. The enteric pathogens in reclaimed wastewater may accumulate in soil and plants and cause food safety concerns. The objective of this study was to determine the effects of irrigation water containing Salmonella on the microbial communities in the rhizosphere and in the root of lettuce. The effects were also examined with three variables (soil texture, lettuce cultivar and harvest time) in a factorial design. Analyses of the 16S rRNA gene sequences show that the microbial communities in the root were significantly different from those in the rhizosphere, although ∼80% of the microbes in the root originated from the rhizosphere. Salmonella in irrigation water significantly altered the structure of the microbial community in the rhizosphere, but not in the root. Salmonella internalized in lettuce root was observed when contaminated water was used for irrigation. Compared to lettuce cultivar and harvest time, soil texture played a more significant role in shaping the bacterial communities in the rhizosphere and in the root. Results from this study could advance understanding about the long-term impact of reclaimed wastewater as a source of irrigation water on the microbiota associated with leafy green vegetables.
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http://dx.doi.org/10.1093/femsec/fiy135DOI Listing
September 2018

The Fate of Synthetic and Endogenous Hormones Used in the US Beef and Dairy Industries and the Potential for Human Exposure.

Curr Environ Health Rep 2018 06;5(2):225-232

Department of Civil Engineering, University of Nebraska Lincoln, 1110 S. 67th Street, Omaha, NE, 681822-0178, USA.

Purpose Of Review: Growth-enhancing chemicals used by the beef and dairy industries may be bioavailable to humans via milk, meat, and other environmental matrices. This review evaluates the potential for environmental transport and bioavailability of the active chemical to humans.

Recent Findings: Bovine somatostatin is detectable in milk; however, there is no evidence that the protein persists in the environment nor that it is active in humans. In contrast, steroids are transported through milk and meat to humans where they may exert biological activity. Furthermore, environmental matrices such as raw water and dust may also allow for the environmental transport and bioavailability of steroids to humans. Endogenous and exogenous steroids can be found in the meat, milk, and waste materials produced by cattle. While the concentrations may be low, exposure to these matrices, most notably dairy products made with whole milk, can be a source of exogenous steroids to humans.
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http://dx.doi.org/10.1007/s40572-018-0197-9DOI Listing
June 2018

Three-dimensional modeling of nitrate-N transport in vadose zone: Roles of soil heterogeneity and groundwater flux.

J Contam Hydrol 2018 04 27;211:15-25. Epub 2018 Feb 27.

Department of Civil Engineering, University of Lincoln-Nebraska, Lincoln, NE, USA. Electronic address:

Contamination of groundwater from nitrogen fertilizers in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have considered a controlled field work to investigate the influence of soil heterogeneity and groundwater flow on nitrate-N distribution in both root zone and deep vadose zone. In this work, a numerical model was developed to simulate nitrate-N transport and transformation beneath a center pivot-irrigated corn field on Nebraska Management System Evaluation area over a three-year period. The model was based on a realistic three-dimensional sediment lithology, as well as carefully controlled irrigation and fertilizer application plans. In parallel, a homogeneous soil domain, containing the major sediment type of the site (i.e. sandy loam), was developed to conduct the same water flow and nitrate-N leaching simulations. Simulated nitrate-N concentrations were compared with the monitored nitrate-N concentrations in 10 multi-level sampling wells over a three-year period. Although soil heterogeneity was mainly observed from top soil to 3 m below the surface, heterogeneity controlled the spatial distribution of nitrate-N concentration. Soil heterogeneity, however, has minimal impact on the total mass of nitrate-N in the domain. In the deeper saturated zone, short-term variations of nitrate-N concentration correlated with the groundwater level fluctuations.
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http://dx.doi.org/10.1016/j.jconhyd.2018.02.005DOI Listing
April 2018

Adsorption and decontamination of α-synuclein from medically and environmentally-relevant surfaces.

Colloids Surf B Biointerfaces 2018 Jun 9;166:98-107. Epub 2018 Mar 9.

Department of Civil Engineering, University of Nebraska-Lincoln, United States; Center for Nanohybrid Functional Materials, University of Nebraska-Lincoln, United States. Electronic address:

The assembly and accumulation of α-synuclein fibrils are implicated in the development of several neurodegenerative disorders including multiple system atrophy and Parkinson's disease. Pre-existing α-synuclein fibrils can recruit and convert soluble non-fibrillar α-synuclein to the fibrillar form similar to what is observed in prion diseases. This raises concerns regarding attachment of fibrillary α-synuclein to medical instruments and subsequent exposure of patients to α-synuclein similar to what has been observed in iatrogenic transmission of prions. Here, we evaluated adsorption and desorption of α-synuclein to two surfaces: stainless steel and a gold surface coated with a 11-Amino-1-undecanethiol hydrochloride self-assembled-monolayer (SAM) using in-situ combinatorial quartz crystal microbalance with dissipation and spectroscopic ellipsometry. α-Synuclein was found to attach to both surfaces, however, increased α-synuclein adsorption was observed onto the positively charged SAM surface compared to the stainless steel surface. Dynamic light scattering data showed that larger α-synuclein fibrils were preferentially attached to the stainless steel surface when compared with the distributions in the original α-synuclein solution and on the SAM surface. We determined that after attachment, introduction of a 1N NaOH solution could completely remove α-synuclein adsorbed on the stainless steel surface while α-synuclein was retained on the SAM surface. Our results indicate α-synuclein can bind to multiple surface types and that decontamination is surface-dependent.
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http://dx.doi.org/10.1016/j.colsurfb.2018.03.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5911191PMC
June 2018

A review of the fate of engineered nanomaterials in municipal solid waste streams.

Waste Manag 2018 May 21;75:427-449. Epub 2018 Feb 21.

Department of Water-Atmosphere-Environment, Institute of Waste Management, University of Natural Resources and Life Sciences, Muthgasse 107, 1190 Vienna, Austria.

Significant knowledge and data gaps associated with the fate of product-embedded engineered nanomaterials (ENMs) in waste management processes exist that limit our current ability to develop appropriate end-of-life management strategies. This review paper was developed as part of the activities of the IWWG ENMs in Waste Task Group. The specific objectives of this review paper are to assess the current knowledge associated with the fate of ENMs in commonly used waste management processes, including key processes and mechanisms associated with ENM fate and transport in each waste management process, and to use that information to identify the data gaps and research needs in this area. Literature associated with the fate of ENMs in wastes was reviewed and summarized. Overall, results from this literature review indicate a need for continued research in this area. No work has been conducted to quantify ENMs present in discarded materials and an understanding of ENM release from consumer products under conditions representative of those found in relevant waste management process is needed. Results also indicate that significant knowledge gaps associated with ENM behaviour exist for each waste management process investigated. There is a need for additional research investigating the fate of different types of ENMs at larger concentration ranges with different surface chemistries. Understanding how changes in treatment process operation may influence ENM fate is also needed. A series of specific research questions associated with the fate of ENMs during the management of ENM-containing wastes have been identified and used to direct future research in this area.
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http://dx.doi.org/10.1016/j.wasman.2018.02.012DOI Listing
May 2018

Using Watershed Boundaries to Map Adverse Health Outcomes: Examples From Nebraska, USA.

Environ Health Insights 2018 24;12:1178630217751906. Epub 2018 Jan 24.

Department of Environmental, Agricultural & Occupational Health, University of Nebraska Medical Center, Omaha, NE, USA.

In 2009, a paper was published suggesting that watersheds provide a geospatial platform for establishing linkages between aquatic contaminants, the health of the environment, and human health. This article is a follow-up to that original article. From an environmental perspective, watersheds segregate landscapes into geospatial units that may be relevant to human health outcomes. From an epidemiologic perspective, the watershed concept places anthropogenic health data into a geospatial framework that has environmental relevance. Research discussed in this article includes information gathered from the literature, as well as recent data collected and analyzed by this research group. It is our contention that the use of watersheds to stratify geospatial information may be both environmentally and epidemiologically valuable.
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http://dx.doi.org/10.1177/1178630217751906DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5788116PMC
January 2018

Dehydration of Prions on Environmentally Relevant Surfaces Protects Them from Inactivation by Freezing and Thawing.

J Virol 2018 04 28;92(8). Epub 2018 Mar 28.

Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, USA

Chronic wasting disease (CWD) is an emerging prion disease in North America. Recent identification of CWD in wild cervids from Norway raises the concern of the spread of CWD in Europe. CWD infectivity can enter the environment through live animal excreta and carcasses where it can bind to soil. Well-characterized hamster prion strains and CWD field isolates in unadsorbed or soil-adsorbed forms that were either hydrated or dehydrated were subjected to repeated rounds of freezing and thawing. We found that 500 cycles of repeated freezing and thawing of hydrated samples significantly decreased the abundance of PrP and reduced protein misfolding cyclic amplification (PMCA) seeding activity that could be rescued by binding to soil. Importantly, dehydration prior to freezing and thawing treatment largely protected PrP from degradation, and the samples maintained PMCA seeding activity. We hypothesize that redistribution of water molecules during the freezing and thawing process alters the stability of PrP aggregates. Overall, these results have significant implications for the assessment of prion persistence in the environment. Prions excreted into the environment by infected animals, such as elk and deer infected with chronic wasting disease, persist for years and thus facilitate horizontal transmission of the disease. Understanding the fate of prions in the environment is essential to control prion disease transmission. The significance of our study is that it provides information on the possibility of prion degradation and inactivation under natural weathering processes. This information is significant for remediation of prion-contaminated environments and development of prion disease control strategies.
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http://dx.doi.org/10.1128/JVI.02191-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874414PMC
April 2018

Response and recovery of fathead minnows (Pimephales promelas) following early life exposure to water and sediment found within agricultural runoff from the Elkhorn River, Nebraska, USA.

Sci Total Environ 2018 Mar 18;618:1371-1381. Epub 2017 Oct 18.

Department of Environmental, Agricultural and Occupational Health, University of Nebraska - Medical Center, Omaha, NE 68198-6805, United States; Department of Biology, University of Nebraska at Omaha, Omaha, NE 68182-0040, United States; Idaho Water Resources Research Institute, University of Idaho, Moscow, ID 83844-3002, United States. Electronic address:

Agricultural runoff is a non-point source of chemical contaminants that are seasonally detected in surface water and sediments. Agrichemicals found within seasonal runoff can elicit endocrine disrupting effects in organisms as adults, juveniles and larvae. The objectives of this study were (1) to determine if exposure to water, sediment or the water-sediment combination collected from an agricultural runoff event was responsible for changes in endocrine-responsive gene expression and development in fathead minnow larvae, and (2) whether such early life exposure leads to adverse effects as adults. Larvae were exposed during the first month post-hatch to water and sediment collected from the Elkhorn River and then allowed to depurate in filtered water until reaching sexual maturity, exemplifying a best-case recovery scenario. Gas chromatography mass spectrometry (GC/MS) analysis of the water and sediment samples detected 12 pesticides including atrazine, acetochlor, metolachlor and dimethenamid. In minnow larvae, exposure to river water upregulated androgen receptor gene expression whereas exposure to the sediment downregulated estrogen receptor α expression. Adult males previously exposed to both water and sediment were feminized through the induction of an ovipositor structure whereas no impacts were observed in other reproductive or sex characteristic endpoints for either sex based on exposure history. Results from this study indicate that both water and sediments found in agricultural runoff elicit responses from minnow larvae, and larvae can recover following early life exposure under a best-case scenario.
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http://dx.doi.org/10.1016/j.scitotenv.2017.09.259DOI Listing
March 2018

Compensatory response of fathead minnow larvae following a pulsed in-situ exposure to a seasonal agricultural runoff event.

Sci Total Environ 2017 Dec 3;603-604:817-826. Epub 2017 Apr 3.

Department of Environmental, Agricultural and Occupational Health, University of Nebraska - Medical Center, Omaha, NE 68198-6805, United States; Department of Biology, University of Nebraska at Omaha, Omaha, NE 68182-0040, United States. Electronic address:

Agriculturally-dominated waterways such as those found throughout the Midwestern United States often experience seasonal pulses of agrichemical contaminants which pose a potential hazard to aquatic organisms at varying life stages. The objective of this study was to characterize the developmental plasticity of fathead minnow larvae in a natural environment subject to a seasonal episodic perturbation in the form of a complex mixture of agricultural stressors. Fathead minnow larvae were maintained at the Elkhorn River Research Station for a 28-d in situ exposure to an agrichemical pulse event. Minnow larvae were sampled after 14 and 28days to characterize developmental plasticity through growth measures and relative gene expression. Concentrations of agrichemical contaminants measured in water using polar organic chemical integrative samplers and composite sediment samples throughout the 28-d exposure were quantified using gas chromatography-mass spectrometry. Elevated concentrations of acetochlor, atrazine, and metolachlor were indicative of inputs from agricultural sources and were associated with reductions in body mass, condition factor, and androgenic gene expression in river exposed fathead minnow larvae. However, following a 14-d in situ depuration during the post-pulse period, river exposed larvae overcompensated in previously suppressed biological endpoints. These results indicate that fathead minnow larvae are capable of compensatory responses following episodic exposure to agrichemical stressors.
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http://dx.doi.org/10.1016/j.scitotenv.2017.03.093DOI Listing
December 2017

Stereoselective Degradation of Estradiol and Trenbolone Isomers in Alluvial Sediment.

Environ Sci Technol 2016 12 30;50(24):13256-13264. Epub 2016 Nov 30.

Department of Civil Engineering, University of Nebraska-Lincoln, Peter Kiewit Institute , Omaha, Nebraska 68182-0178, United States.

Stereoisomers of estradiol (E2) or trenbolone (TB) can occur together in the environment receiving human or livestock wastes. However, the effect of their co-occurrence on persistence has not been well elucidated. A sandy and a silt loam sediment were used to establish microcosms with α- and β-isomers of E2 or TB spiked individually and together. Sediments were sampled periodically and analyzed for E2 and TB isomers and their transformation products using derivatization gas chromatography-mass spectrometry. Results showed that stereoselective degradation was significant for E2 in both sediments and TB in the sandy sediment with β-isomers decaying more rapidly than α-isomers. In the sandy sediment containing limited natural organic carbon and nutrients, co-occurrence of both isomers of either E2 or TB decreased the dissipation rates. In the silt loam sediment with abundant organic matter and nutrients, the decay rates of both isomers were not changed in the presence of the other isomer. Estrone (E1) and trendione (TD) were detected as primary metabolites of E2 and TB isomers, respectively. The formation and decay profiles of E1 were similar in both sediments with 92-100% of E2 transformed to E1. The TD profiles were different across sediments with ∼100% of TB transformed to TD except in the sandy sediment where 51-60% of 17α-TB was converted to TD. These results indicate that the transformation processes of steroid hormone are stereoselective in sediment and co-occurrence of stereoisomers can prolong steroid persistence and thus pose greater environmental risk.
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http://dx.doi.org/10.1021/acs.est.6b02171DOI Listing
December 2016

Effect of rainfall timing and tillage on the transport of steroid hormones in runoff from manure amended row crop fields.

J Hazard Mater 2017 Feb 4;324(Pt B):436-447. Epub 2016 Nov 4.

Dept. of Animal Science, Univ. of Nebraska-Lincoln, Haskell Agricultural Laboratory, 57905 866 Road, Concord, NE 68728-2828, United States.

Runoff generated from livestock manure amended row crop fields is one of the major pathways of hormone transport to the aquatic environment. The study determined the effects of manure handling, tillage methods, and rainfall timing on the occurrence and transport of steroid hormones in runoff from the row crop field. Stockpiled and composted manure from hormone treated and untreated animals were applied to test plots and subjected to two rainfall simulation events 30days apart. During the two rainfall simulation events, detection of any steroid hormone or metabolites was identified in 8-86% of runoff samples from any tillage and manure treatment. The most commonly detected hormones were 17β-estradiol, estrone, estriol, testosterone, and α-zearalenol at concentrations ranging up to 100-200ngL. Considering the maximum detected concentrations in runoff, no more than 10% of the applied hormone can be transported through the dissolved phase of runoff. Results from the study indicate that hormones can persist in soils receiving livestock manure over an extended period of time and the dissolved phase of hormone in runoff is not the preferred pathway of transport from the manure applied fields irrespective of tillage treatments and timing of rainfall.
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http://dx.doi.org/10.1016/j.jhazmat.2016.11.009DOI Listing
February 2017

Detection, Occurrence and Fate of Emerging Contaminants in Agricultural Environments.

Water Environ Res 2016 Oct;88(10):913-29

Nebraska Water Center, part of the Robert B. Dougherty Water for Food Institute, 202 Water Sciences Laboratory, University of Nebraska, Lincoln, NE 68583-0844, USA.

A total of 59 papers published in 2015 were reviewed ranging from detailed descriptions of analytical methods, to fate and occurrence studies, to ecological effects and sampling techniques for a wide variety of emerging contaminants likely to occur in agricultural environments. New methods and studies on veterinary pharmaceuticals, steroids, antibiotic resistance genes in agricultural environments continue to expand our knowledge base on the occurrence and potential impacts of these compounds. This review is divided into the following sections: Introduction, Analytical Methods, Steroid Hormones, Pharmaceutical Contaminants, Transformation Products, and "Antibiotic Resistance, Drugs, Bugs and Genes".
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http://dx.doi.org/10.2175/106143016X14696400494335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5896310PMC
October 2016

Impact of sediment particle size on biotransformation of 17β-estradiol and 17β-trenbolone.

Sci Total Environ 2016 Dec 4;572:207-215. Epub 2016 Aug 4.

Department of Civil Engineering, University of Nebraska-Lincoln, Peter Kiewit Institute, Omaha, NE 68182-0178, United States. Electronic address:

Soil/sediment particle size has been reported to influence the sorption and bioavailability of steroid hormones in the environment. However, the impact of particle size on biotransformation has not been well elucidated. The present study investigated the dissipation of 17β-estradiol and 17β-trenbolone and the formation and degradation of the subsequent transformation products in different size fractions of a sandy and a silt loam sediment. The results showed that the decay of 17β-estradiol and 17β-trenbolone associated with fine particles followed a biphasic pattern with more rapid decay in the initial phase followed by a second phase with slower decay of the residues compared to their decay rates in the sand fraction. Estrone and trendione were detected as a primary biotransformation product for 17β-estradiol and 17β-trenbolone, respectively. The parent-to-product conversion ratios and the degradation rates of estrone and trendione varied among different size fractions, but no consistent correlation was observed between decay rates and sediment particle size. Estrone and trendione decayed in the whole sediments at rates not statistically different from those associated with the fine fractions. These results indicate that fine particles may play an important role in influencing the persistence of and the potential risk posed by steroid hormones in the aquatic systems.
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http://dx.doi.org/10.1016/j.scitotenv.2016.08.004DOI Listing
December 2016
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