Outlet Sites Research Articles

Water Quality Evaluation in Akilpur lake, Dighwara, Saran of North Bihar

Akilpur lake is surrounded by agricultural lands and cover about 1500 meter in length and 300 meter in width and connected occasionally with Ganga river in flooding period of the year. The agricultural and anthropogenic activities increasingly polluted the water quality of the lake. This research was carried out to monitor the water quality status of the lake on the monthly basis from January 2021 to December 2021. The water samples were collected from inlet, mid-lake, and outlet sites and analyzed for different physical and chemical parameters, following the standard American Public Health Organization methods. The results were compared with surface water quality standard given by Bureau of Indian Standards. It was observed that mid-lake water was not much affected by different pollution sources as compared to inlet and outlet waters. The lake water was observed increasingly polluted than earlier and there is need of care to monitor lake for sustainable perspective.

Significant tipping points of sediment microeukaryotes forewarn increasing antibiotic pollution

Antibiotic pollution imposes urgent threats to public health and microbial-mediated ecological processes. Existing studies have primarily focused on bacterial responses to antibiotic pollution, but they ignored the microeukaryotic counterpart, though microeukaryotes are functionally important (e.g., predators and saprophytes) in microbial ecology. Herein, we explored how the assembly of sediment microeukaryotes was affected by increasing antibiotic pollution at the inlet (control) and across the outlet sites along a shrimp wastewater discharge channel. The structures of sediment microeukaryotic community were substantially altered by the increasing nutrient and antibiotic pollutions, which were primarily controlled by the direct effects of phosphate and ammonium (−0.645 and 0.507, respectively). In addition, tetracyclines exerted a large effect (0.209), including direct effect (0.326) and indirect effect (−0.117), on the microeukaryotic assembly. On the contrary, the fungal subcommunity was relatively resistant to antibiotic pollution. Segmented analysis depicted nonlinear responses of microeukaryotic genera to the antibiotic pollution gradient, as supported by the significant tipping points. We screened 30 antibiotic concentration-discriminatory taxa of microeukaryotes, which can quantitatively and accurately predict (98.7% accuracy) the in-situ antibiotic concentration. Sediment microeukaryotic (except fungal) community is sensitive to antibiotic pollution, and the identified bioindicators could be used for antibiotic pollution diagnosis.

Forecasting Abrupt Depletion of Dissolved Oxygen in Urban Streams Using Discontinuously Measured Hourly Time‐Series Data

AbstractDepletion of dissolved oxygen (DO) is a major cause of fish kills in urban streams. Although forecasting short‐term DO concentrations in streams prior to hypoxic events is necessary, such efforts have been rarely made. In this study, 24‐h forecasting models were developed for DO concentrations in three urban streams of South Korea. To forecast the DO concentrations at the outlet sites, which coincide with fish kill hot spot areas, water quality parameters at the lower reaches and hydrometeorological parameters were used as input variables. The monitoring data were measured hourly between 2017 and 2018 and divided into training and test sets at a ratio of 8:2. Tenfold cross validation was performed for hyperparameter optimization. Due to the dynamic characteristics of DO concentrations and the discontinuity in time‐series data, a long short‐term memory (LSTM) neural network modeling approach was selected. Overall, a high degree of accuracy was recorded for all study streams. Although hypoxic events were forecast with lower accuracy, the timing and magnitude of abrupt DO depletion were well captured. Water temperature and DO concentrations at the lower reaches and 24‐h cumulative precipitation were important variables for forecasting DO concentrations at all stream outlets. In particular, the importance of cumulative precipitation across all streams indicated that the effects of nonpoint sources were critical in depleting DO in urban streams. Monitoring of both lower reaches and outlets in conjunction with a variable importance analysis enhanced interpretability of the LSTM model outputs. This study improves our understanding of precursors of hypoxic events in urban streams.

Anthropogenic particles in sediment from an Arctic fjord

The research on plastic pollution is increasing worldwide but little is known about the contamination levels in the Arctic by microplastics and other anthropogenic particles (APs) such as dyed fibres. In this study, two different sampling designs were developed to collect 68 sediment subsamples in five locations in a remote Arctic fjord, Kongsfjorden, northwest of Svalbard. Those five stations composed a transect from a sewage outlet recently installed close to the northernmost settlement, Ny-Ålesund, to an offshore site. Plastics and other APs were extracted by density separation and analysed by both Raman and Fourier Transform Infrared spectroscopy. Among the 37 APs found, 19 were microplastics. The others were classified as APs due to the presence of a dye or another additive. On average, 0.33 AP 100 g−1 were found in the surface sediment and their sizes ranged between 0.10 and 6.31 mm. The site most polluted by APs was located at the mouth of the fjord while the less polluted ones were the offshore and the outlet sites. We believe that currents in the fjord have carried APs towards the mouth of the fjord where an eddy could retain APs which might sink the seafloor due to various reasons (ingestion & packaging, fouling-induced changes in buoyancy). In the cores, several different APs were found down to a depth of 12 cm. These APs may have been present in the sediments for decades or been transported deeper by biota. Here we provided data on plastic but also on other anthropogenic particles from a remote fjord in Svalbard.

Isolation and characterization of a multidrug-resistant Clostridioides difficile toxinotype V from municipal wastewater treatment plant.

Wastewater treatment plant (WWTP) is regarded as a potential source for transmission of Clostridioides difficile from urban areas into the surface water, through feces of human and animals. The aim of this study was to screen and characterize the C. difficile bacteria in inlet and outlet wastewater of different WWTPs in Tehran, Iran. Totally, 72 samples were collected from three different WWTPs (inlet site and outlet sites) during a year. C. difficile was isolated and characterized in terms of toxins, toxinotype, resistance profile and genes, and colonization factors using PCR. One C. difficile toxinotype V was isolated from the outlet samples. The isolate was susceptible to vancomycin but resistant to metronidazole, tetracycline, ciprofloxacin, and moxifloxacin using MIC Test Strips. The isolated C. difficile was toxigenic (tcdA, tcdB, cdtA, cdtB positive and CPE positive) and had tcdC-A genotype. No mutations were found in fliC and fliD. The slpA sequence type was 078 - 01. The C. difficile was positive for tetM, int, but negative for vanA, nim, and tndX genes. Mutations were not observed in gyrA and gyrB genes. This study provided evidence of presence of a multidrug-resistant C. difficile toxinotype V in one of the municipal WWTP. The transmission of such isolate to the environment and reuse of treated wastewater by human pose a threat to human health and dissemination of antibiotic resistant bacteria which are untreatable.

Microecological Relationships Between Area Income, Off-Premise Alcohol Outlet Density, Drinking Patterns, and Alcohol Use Disorders: The East Bay Neighborhoods Study.

Distinguishing the impacts of neighborhood income and off-premise alcohol outlet density on alcohol use has proven difficult, particularly given the conflation of these measures across neighborhood areas. We explicitly test for differential effects related to individual and area income and outlet densities on alcohol use and alcohol use disorders (AUDs) by implementing a stratified microecological sample. The East Bay Neighborhoods Study included a survey of 984 residents of 72 microenvironments within a geographically contiguous 6-city area in California and Systematic social observations of each site. The sites included 18 areas in each of 4 strata (high/low median household income and off-premise outlet density). We assessed 4 outcomes: 28-day drinking frequency, average quantity of alcohol consumed per drinking occasion, 28-day drinking volume, and Alcohol Use Disorders Identification Test (AUDIT) score. We used zero-inflated negative binomial regression with standard errors adjusted for site clusters to relate drinking measures to individual-level age, race/ethnicity, gender, marital status, education, and income, and neighborhood indicators of site strata, physical disorder, and physical decay. An interaction term was tested representing site-level by individual-level income. Living in a high-income site, regardless of off-premise alcohol outlet density, was associated with more frequent drinking and higher alcohol dependence/problems. Both individual-level income and site-level income were related to greater frequencies of use, but lower income drinkers in high-income areas drank more than comparable drinkers in low-income areas. Study participants living in high-density off-premise alcohol outlet sites drank less frequently but did not differ in terms of either AUDIT scores or heavy drinking from participants living in low-density sites. Using a stratified microecological sampling design, we were able to directly assess statistical associations of off-premise outlet density and neighborhood median household income with patterns of drinking and AUDs. Caution should be used interpreting prior study findings linking off-premise outlet densities to drinking.

Effect of Desalination Discharge on the Abundance and Diversity of Reef Fishes.

Global growth in desalination industries has increased the need for an evidence-based understanding of associated environmental impacts. We completed a seven-year assessment of the responses of fish assemblages to hypersaline discharge from the large Sydney Desalination Plant. At 12 times before, eight times during, and four times following the cessation of discharging hypersaline brine, we sampled reef fishes at two outlet sites and two close reference sites, as well as four reference sites that were located from 2-8 km from the outlet. At each site and each time of sampling, five 50 m video transects were used to sample reef fish assemblages. Following the commencement of discharging, there was a 279% increase in the abundance of fish around the outlet, which included substantially greater abundances of pelagic and demersal fish, as well as fishes targeted by recreational and commercial fishers. Following the cessation of discharge, abundances of fishes mostly returned to levels such that there was no longer a significant effect compared to the period prior to the commencement of the desalination plant's operations. Overall, our results demonstrate that well-designed marine infrastructure and processes used to support the growing demand for potable water can also enhance local fish abundances and species richness.

Response of microbial communities of karst river water to antibiotics and microbial source tracking for antibiotics

In southwestern China, karst river water is the main source of water for humans. As emerging pollutants, antibiotics have contaminated karst river water in some areas for a long time. Microbiota is highly susceptible to environmental changes, and can be used in tracing the source of antibiotics in complex systems such as karst water. Ten karst river water samples were collected along the river flow. The diversity and structure of the microbial community were analyzed together with environmental factors through correlation analysis, the random forest algorithm and co-occurrence network analysis. At genus level, Arcobacter was significantly positively correlated with the antibiotics, indicating that Arcobacter and antibiotics probably came from the same source. Based on co-occurrence network analysis between microbes, the microbial community was divided into eight modules, and the relative abundance of three modules was significantly correlated with antibiotics. The co-occurrence networks between bacteria and antibiotic resistance genes (ARGs) showed that pathogenic bacteria potentially carried multiple ARGs. This could increase the disease risk to humans and disease transmission in the study area. When river water flowed underground, the concentration of antibiotics decreased for the two underground river outlet sites, but abundance of bacteria and ARGs increased. Microbial source tracking studies showed that contamination was derived from humans rather than livestock. The ranking importance of prediction for antibiotics in this study area from random forest follows: specific bacteria Arcobacter > ARGs > ecological clusters. This study will be helpful in identifying the effect of antibiotics discharge on the microbial community, improving evaluation of antibiotics' risks and contaminants source tracking.

Glacier recession and glacial lake outburst flood studies in Zanskar basin, western Himalaya

Glacier recession and formation of glacial lakes along with outburst flood hazards are increasing in response to changing climate in the Himalayan region. This study describes evolution of Dalung and Padam glaciers and their associated lakes employing multi-temporal datasets of Landsat (MSS, TM, ETM+), Indian Remote Sensing LISS-III, Google EarthTM, ASTER GDEM and Survey of India topographic maps. The Dalung Glacier (DG) and Lake (DL) are present in Suru River catchment whereas the Padam Glacier (PG) and Lake (PL) are present in Tsarap River catchment of Zanskar basin, western Himalaya. From 1962 to 2015; the DG and PG have shrunk at different rates. The DG has shrunk by 2.6 ± 0.56 km2 (19.2 ± 4.1%) at a rate of 0.05 ± 0.01 km2 a−1 whereas, the PG has shrunk by 3.4 ± 0.65 km2 (12.7 ± 2.4%) at a rate of 0.06 ± 0.01 km2 a−1. The frontal recession was recorded as 1.240 ± 0.02 km (15.7 ± 2.0%) at a rate of 20 ± 0.4 m a−1 for DG and 2.690 ± 0.5 m (21.3 ± 2.1%) at a rate of 50.7 ± 0.1 m a−1 for PG. Consequently, the proglacial glacial lakes have formed indicating an expansion of 20 ± 3.4% (DL) and 58 ± 4.5% (PL) during 1990–2015. Using integrated criteria of standard indices for the identification of potentially dangerous glacial lakes (PDGLs), the lakes were found to be vulnerable and have a potential to cause breaching in the coming years. In order to provide inputs for the emergency action plan, one dimensional MIKE 11 Model was used to generate the peak flood hydrographs at the lake and other vulnerable sites downstream. Highest peak discharge of 3361.7 m3 s−1 (DL) and 4210.3 m3 s−1 (PL) were estimated at the lake sites which has reduced to 1520.9 m3 s−1 and 1722.4 m3 s−1 respectively at the outlet sites. The reduced discharge at downstream sites still bears the potential to create dangerous flood hazards.

DETERMINATION OF ARSENIC CONTENT IN WASTEWATER-FED FISH POND IN HOANG MAI DISTRICT, HANOI, VIETNAM

Aquaculture in pond fed with wastewater has been practiced since the 1960s in Hoang Mai and Thanh Tri districts in Hanoi, Vietnam. Wastewater after directly discharged in to Kim Nguu and To Lich river is currently used for cultivation of vegetables and fishes. According to the previous studies, the content of some heavy metals in water and sediments from Kim Nguu and To Lich river exceeded the Vietnamese standard values. In this study, arsenic concentration in water, sediment, fish and plant collected from a wastewater fed-fish pond in Hoang Mai district, Ha Noi, Vietnam were determined by graphite furnace atomic absorption spectrometry (GF/AAS). Arsenic concentration in water collected from inlet and outlet sites of the pond were of 45.86 and 23.22 μg/L, respectively and those levels were higher than the Vietnamese standard. About 14% of arsenic entered the fish pond was in the suspended particulate mater (SPM) form. Arsenic concentration in the sediment ranged from 12.26 to 23.87 mg/kg (dry weight). The highest levels of arsenic found in the sediment near the pond outlet were probably caused by the movement of the sediment and heavy metals with the water flow. Based on the Vietnamese standards for agriculture soils, the studied pond sediment is not safe for crop application. Arsenic contents of 0.20 and 0.06 mg/kg (dry weight) were found in tissues of common carp and tilapia. The lower As contents in the outlet water in comparison to the inlet water showed that part of As was removed in the fish pond by different processes including the sedimentation and bio-adsorption. The As contents in the coarse stems/leaves of the water spinach samples were about 2.6 times higher than those in the shoot tips/younger leaves. As the findings, the water spinach and fish in this wastewater –fed fish pond were considered safe for human consumption with respect to arsenic content and Vietnamese standard.

Weather, Landscape, and Management Effects on Nitrate and Soluble Phosphorus Concentrations in Subsurface Drainage in the Western Lake Erie Basin

Abstract. Subsurface drainage, while an important and necessary agricultural production practice in the Midwest, contributes nitrate (NO3-N) and soluble phosphorus (P) to surface waters. Eutrophication (i.e., excessive enrichment of surface water by NO3-N and soluble P) supports harmful algal blooms in receiving waters. The magnitude of NO3-N and soluble P loss in subsurface drainage varies greatly by landscape, weather, and field management factors. This study evaluated both the relative and combined impacts of these factors on observed NO3-N and soluble P concentrations in subsurface drainage water in the Western Lake Erie Basin watershed. Water quality data from multiple drainage outlet sites in northwest Ohio provided evidence that the primary management factors affecting NO3-N and soluble P loss were the amount and time of fertilizer application. Results strongly support following Tri-State fertilizer recommendations and 4R nutrient stewardship principles to reduce the risk of NO3-N and soluble P loss. Results also provided evidence of NO3-N and soluble P transport to subsurface drains via different pathways. Due to differences in NO3-N and soluble P transport through the soil profile (via baseflow and preferential flow, respectively), management approaches taken to reduce one nutrient may exacerbate losses of the other. Further research is needed to address potential changes in field hydrology (and consequently the in-field transport of soluble nutrients) from different types of agricultural best management practices (BMPs) and to evaluate optimal stacking of BMPs to achieve reductions in both NO3-N and soluble P loss. Controlled drainage has a high potential for stacking with other BMPs because it is primarily a physical discharge and load reduction practice. Keywords: Agriculture, Eutrophication, Nutrient transport, Regression analysis, Water quality.

Sediment accretion and carbon storage in constructed wetlands receiving water treated with metal-based coagulants

In many regions of the world, subsidence of organic rich soils threatens levee stability and freshwater supply, and continued oxidative loss of organic matter contributes to greenhouse gas production. To counter subsidence in the Sacramento-San Joaquin Delta of northern California, we examined the feasibility of using constructed wetlands receiving drainage water treated with metal-based coagulants to accrete mineral material along with wetland biomass, while also sequestering carbon in wetland sediment. Nine field-scale wetlands were constructed which received local drainage water that was either untreated (control), or treated with polyaluminum chloride (PAC) or iron sulfate (FeSO4) coagulants. After twenty three months of flooding and coagulant treatment, sediment samples were collected near the inlet, middle, and outlet of each wetland to determine vertical accretion rates, bulk density, sediment composition, and carbon sequestration rates. Wetlands treated with PAC had the highest and most spatially consistent vertical accretion rates (∼6cmyr−1), while the FeSO4 wetlands had similarly high accretion rates near the inlet but rates similar to the untreated wetland (∼1.5cmyr−1) at the middle and outlet sites. The composition of the newly accreted sediment in the PAC and FeSO4 treatments was high in the added metal (aluminum and iron, respectively), but the percent metal by weight was similar to native soils of California. As has been observed in other constructed wetlands, the newly accreted sediment material had lower bulk densities than the native soil material (0.04–0.10gcm−3 versus 0.2–0.3gcm−3), suggesting these materials will consolidate over time. Finally, this technology accelerated carbon burial, with rates in PAC treated wetland (0.63kgCm−2yr−1) over 2-fold greater than the untreated control (0.28kgCm−2yr−1). This study demonstrates the feasibility of using constructed wetlands treated with coagulants to reverse subsidence by accreting the resulting organo-metal flocculent and storing carbon at rates exceeding untreated wetlands. Management and design questions remain for how to best integrate this technology into heavily subsided land to lower the risks and consequences associated with levee failure, improve water quality, and ultimately restore these lands to tidal wetlands.

Potency of constructed wetlands for deportation of pathogens index from rural, urban and industrial wastewater

Pathogen removal is essential for wastewater treatment and its potential reuse in agriculture. Three field-scale wastewater treatment systems consisting of free surface flow were operated around 1.5 years receiving water from urban domestic, rural domestic and industrial sources. The study was conducted to evaluate seasonal performance of constructed wetland systems in removing Escherichia coli, Enterococci and total coliforms under continuous hydraulic flow. Results displayed that all three wetlands gain recognition in removing pathogen load with high removal efficacy till water reaches output ports. Removal efficiencies were even higher, 66–93, 78–92 and 80–94% for E. coli, Enterococci and total coliforms, respectively, within constructed wetlands. Remarkably at shorter temporal scales in CW-A, greater homogeneity of pathogen concentrations was assessed at wetland outlet sites. In outlet ports, results displayed a highly effective removal of E. coli concentration 80–90% (June 2015), 86–92% (October 2015) and 79–92% (February 2016), Enterococci 80–94% (June 2015), 83–94% (October 2015) and 80–94% (February 2016) and total coliforms 85–93% (June 2015), 87–95% (October 2015) and 88–96% (February 2016). Positive correlation was observed between bacterial indicators (E. coli–Enterococci, r = 0.038; p < 0.01 and E. coli–total coliforms, r = 0.142; p < 0.01). Removal of bacterial indicators in constructed wetland was also displayed by PCA in which three-component analysis of variance was 98.39% and showed a clear decrease in measured parameter gradients toward samples from outlet ports. Constructed wetlands provide cost-effective treatment systems for reducing the pathogen load in wastewater in variable agro-climatic conditions and thus improve water quality.

Descriptive and multivariate analyses of four Tunisian wastewater treatment plants: A comparison between different treatment processes and their efficiency improvement

This study was undertaken to evaluate the performance of four wastewater treatment plants/processes over a 4 year period. The wastewater flow evolution, energy consumption, and quality indicator parameters (BOD5, COD and TSS) at the inlet and outlet sites of the plants were determined. In comparing three domestic WWTPs with different wastewater treatment processes, the multivariate analyses (RDA and ANOVA) showed that although the Agareb plant received the highest pollution load, it displayed a high level of removal efficiency especially for COD, BOD, TSS, TKN and NH4+. It also revealed that the fluctuations in the wastewater composition and its contamination by varied industrial discharge could lead to the decrease in performance of the WWTP with activated sludge process as observed for the Southern Sfax plant. However, the electrolysis of the outlet water of Southern Sfax plant showed a significant improvement in COD removal.

Characteristics of trace metals in traffic-derived particles in Hsuehshan Tunnel, Taiwan: size distribution, potential source, and fingerprinting metal ratio

Abstract. Traffic emissions are a significant source of airborne particulate matter (PM) in ambient environments. These emissions contain an abundance of toxic metals and thus pose adverse effects on human health. Size-fractionated aerosol samples were collected from May to September 2013 by using micro-orifice uniform deposited impactors (MOUDIs). Sample collection was conducted simultaneously at the inlet and outlet sites of Hsuehshan Tunnel in northern Taiwan, which is the second-longest freeway tunnel (12.9 km) in Asia. This endeavor aims to characterize the chemical constituents and size distributions, as well as fingerprinting ratios of particulate metals emitted by vehicle fleets. A total of 36 metals in size-resolved aerosols were determined through inductively coupled plasma mass spectrometry. Three major groups – namely, tailpipe emissions (Zn, Pb, and V in fine mode), wear debris (Cu, Cd, Fe, Ga, Mn, Mo, Sb, and Sn), and resuspended dust (Ca, Mg, K, and Rb) – of airborne PM metals were categorized on the basis of the results of enrichment factor, correlation matrix, and principal component analysis. Size distributions of wear-originated metals resembled the pattern of crustal elements, which were predominated by super-micron particulates (PM1–10). By contrast, tailpipe exhaust elements such as Zn, Pb, and V were distributed mainly in submicron particles. By employing Cu as a tracer of wear abrasion, several inter-metal ratios – including Fe / Cu (14), Ba / Cu (1.05), Sb / Cu (0.16), Sn / Cu (0.10), and Ga / Cu (0.03) – served as fingerprints for wear debris. However, the data set collected in this work is useful for further studies on traffic emission inventory and human health effects of traffic-related PM.

Effects of small impoundments on downstream crayfish assemblages

Dams and impoundments, both large and small, affect downstream physicochemical characteristics and up- and downstream biotic communities. I tested whether small dams and their impoundments altered downstream crayfish assemblages in northern Mississippi. I sampled crayfish and measured physicochemical variables at 4 sites downstream of impoundments (outlet sites) and 4 sites not influenced by impoundments (undammed sites) in August, September, and November 2004. In November 2010, I sampled 7 undammed, 6 outlet, and 3 intermediate sites (influenced by beaver activity or ∼1 km downstream of an impoundment). Crayfish assemblages differed between undammed and outlet sites. Catch-per-unit-effort (CPUE) of Orconectes (Trisellescens) sp. was higher in undammed than outlet sites in both years. Procambarus (Pennides) spp. CPUE was lower in undammed than outlet sites in November 2010 and nearly so in November 2004. In 2004, Procambarus (Ortmannicus) hayi was common in autumn at outlet sites but virtually absent from undammed sites, but in 2010, P. hayi CPUE did not differ between categories. Cambarus striatus CPUE, which was low overall, did not differ between categories in 2004 but was higher in undammed sites in 2010. Seasonal differences among taxa in reproductive timing were important to understanding impoundment effects. The most consistent difference in habitat was that undammed sites had significantly higher width:depth ratios than did outlet sites. Based on the number of mapped small impoundments and a conservative estimate that each impoundment influenced crayfish assemblages over 2 km, I estimated that impoundments probably affect crayfish assemblages in >284 km of stream in the upper Little Tallahatchie River subbasin. Extrapolated to the entire Gulf Coastal Plain, impoundments may influence crayfish assemblages over thousands of stream kilometers.

Molecular Analysis of Bacterial Communities in Biofilms of a Drinking Water Clearwell

Microbial community structures in biofilms of a clearwell in a drinking water supply system in Beijing, China were examined by clone library, terminal restriction fragment length polymorphism (T-RFLP) and 454 pyrosequencing of the amplified 16S rRNA gene. Six biofilm samples (designated R1–R6) collected from six locations (upper and lower sites of the inlet, middle and outlet) of the clearwell revealed similar bacterial patterns by T-RFLP analysis. With respect to the dominant groups, the phylotypes detected by clone library and T-RFLP generally matched each other. A total of 9,543 reads were obtained from samples located at the lower inlet and the lower outlet sites by pyrosequencing. The bacterial diversity of the two samples was compared at phylum and genus levels. Alphaproteobacteria dominated the communities in both samples and the genus of Sphingomonas constituted 75.1%–99.6% of this phylum. A high level of Sphingomonas sp. was first observed in the drinking water biofilms with 0.6–1.0 mg L−1 of chlorine residual. Disinfectant-resistant microorganisms deserve special attention in drinking water management.This study provides novel insights into the microbial populations in drinking water systems and highlights the important role of Sphingomonas species in biofilm formation.

Recent water quality trends and a comparison to sediment-core records for two riverine lakes of the Upper Mississippi River basin: Lake St. Croix and Lake Pepin

Long-term water quality monitoring data from two riverine lakes in the Upper Mississippi River basin, Lakes St. Croix and Pepin, were analyzed to compare the long-term average water quality conditions and land use distributions, water quality trends and loads at lake inlets and outlets, trends from long-term versus short-term monitoring records, and the ability of paleolimnological cores to accurately infer lake water quality conditions. During the 1976–2004 period, the long-term average concentrations of nutrients, suspended solids, and chlorophyll-a were consistently lower at the Lake St. Croix inlet versus the Lake Pepin inlet, which drains a greater proportion of urban and agricultural runoff. Despite these differences, nutrient trends were similar at the inlets to both lakes; reductions in total phosphorus and ammonium concentrations were attributed to improvements in point source technologies, whereas increasing nitrate concentrations were attributed to both point source changes and nonpoint source increases. Despite improvements in several water quality variables, nitrate concentrations are increasing in both lakes, sediment trends indicate persistent nonpoint source inputs to Lake Pepin, and current total phosphorus concentrations remain well above pre-1950s levels in both lakes. Since urban development and agriculture are increasing in the Lake St. Croix and Lake Pepin Watersheds, continued point source regulation and additional nonpoint source control efforts will be needed to further improve water quality in these lakes. The 1976–2004 trends for most water quality variables were similar at inlet versus outlet sites on Lake St. Croix. Trends at Lake Pepin inlet versus outlet sites were less similar, but data availability limited the comparison to the 1993–2003 period. While the truncated data record highlighted short-term trends in both lakes, the full data record was most useful for exploring general patterns in water quality. Length of monitoring record affected our ability to detect trends at the inlets to both lakes, and altered the magnitude of detected trends. During the two decades of the 1980s and 1990s, paleolimnological estimates of retained phosphorus loads were similar to those estimated from recent water quality monitoring. These similarities support the use of paleolimnological approaches to infer past water quality conditions in Lakes St. Croix and Pepin.

Mercury and Methylmercury Concentrations in Muscle Tissue of Fish Caught in Major Rivers of the Czech Republic

The aim of the study was to evaluate mercury contamination at twelve outlet sites of rivers in the Czech Republic (Labe, Ohře, Vltava, Berounka, Sázava, Otava, Lužnice, Svratka, Dyje, Morava and Odra). As an indicator, we used muscle tissue of the chub (Leuciscus cephalus) caught at selected sites in 2007. A total of 96 fish were examined. Total mercury was determined by atomic absorption spectrophotometry using the AMA 254 analyzer and methylmercury was determined by gas chromatography with electron-capture detection. Total mercury (THg) and methylmercury (MeHg) concentrations ranged 0.039–0.384 mg kg-1 fresh weight and 0.033–0.362 mg kg-1 fresh weight, respectively. Mercury bound in methylmercury (HgMe) made up on average about 82.2% of total mercury. The highest mercury concentrations were found in fish from Obříství, a site on Labe (THg 0.263 ± 0.086 mg kg-1; MeHg 0.256 ± 0.084 mg kg-1). Mercury concentrations in fish from rivers that cross the borders of the Czech Republic (Labe, Odra and Morava) were low. The Czech Republic therefore does not contribute significantly to river pollution outside its national borders. Hazard indices of the sites monitored were well below 1, and reached 1.365 only in Obříství on Labe for fisherman’s family members (i.e. in the case of annual consumption of 10 kg fish). This indicates possible hazards involved in eating meat of fish caught in that location. Based on PTWI for methylmercury, the maximum amount of fish meat allowed for consumption per week was calculated. The site with the lowest value was Obříství on Labe (0.44 kg). The results of this study present a partial contribution to health risk assessment on the major rivers in Czech Republic.

Sequential Extraction of Lead from Grain Size Fractionated River Sediments Using the Optimized BCR Procedure

Fluvial bed sediments are widely used for characterizing anthropogenic contaminant signals in urban watersheds. This study presents the first preliminary examination of sequentially extracted Pb from grain size fractionated bed sediments using the optimized (standardized) BCR procedure. Baseline sediment samples and samples from the vicinity of three storm-sewer outlets in Nuuanu Stream, Honolulu, Hawaii, were examined. The weighted average Pb liberated from four sequentially extracted phases was 144 ± 26 mg/kg (±SD). These Pb concentrations are high compared to 3 mg/kg leached by a 0.5 M HCl solution, and 13 mg/kg from a 4-acid total digestion of baseline sediments. Over a 1.8 km section of stream channel, land use variations and traffic density differences had little impact on the magnitude of Pb in specific phases for each of the six grain size fractions examined. Regardless of grain size or spatial location, Pb in the reducible phase exceeded that in oxidizable, residual and acid extractable phases. Weighted reducible Pb concentrations for three sewer outlet sites ranged from 69 to 92 mg/kg, and this phase typically accounted for 70–80% of all labile Pb. The <63 μm grain size class did not exhibit the highest Pb concentration, instead this was found in either the 125–250 μm or 500–1,000 μm fractions. Examining bed sediment phase associations of Pb over a smaller length dimension (i.e., 40 m) centered around one sewer outlet, indicated higher concentrations at the outlet (180 mg/kg) compared to upstream (132 mg/kg) or downstream (150 mg/kg). The differences were primarily associated with higher Pb concentrations in the reducible and oxidizable phases of the coarse sand fractions (500–2,000 μm) at the outlet. Overall, all data point to a significant anthropogenic signal for Pb in bed sediments in the urbanized section of Nuuanu Stream.