Bootstrapping to investigate the effect of number of macroinvertebrate samples on confidence limits of the mean

A resampling technique (bootstrapping) was used to evaluate the effects of increasing sample number on the confidence limits of mean density and the mean number of taxa (Families) in addition to the performance of four different sampling devices used to collect macroinvertebrates in three streams of contrasting anthropogenic impact. The four sampling devices were a Hess sampler, a modified Hess sampler equipped with an internal water pump, a Surber sampler, and a two-pole kick-net. In general, confidence limits decreased predictably as the number of samples increased, most notably with the addition of a third sample. The density of organisms captured with the Surber sampler was significantly lower than that of the Hess sampler but greater than that of the kick-net sampler. No significant difference in the number of Families was found among sampling devices. Based upon a minimal 10% reduction in confidence limits compared to the previous sample, a minimum of four replicates was suggested when using the Surber sampler. In general, other methods required a greater number of replicates that the Surber to adequately represent density, but this did not hold when applied to the number of taxa. Despite the inconvenience of having to bend down to use the Surber sampler, this study found no evidence to reject its apparent popularity as a sampling method for macroinvertebrates.     

Monitoring toxic cyanobacteria and cyanotoxins (microcystins and cylindrospermopsins) in four recreational reservoirs (Khon Kaen, Thailand)

The toxic cyanobacterial communities of four recreational reservoirs (Bueng Kaen Nakhon, Bueng Thung Sang, Bueng Nong Khot, and Bueng See Than) in Amphur Muang, Khon Kaen Province, Thailand, were investigated. Water samples were collected via monthly sampling from June to October 2011 for the study on the diversity and density of toxic cyanobacteria and toxin quantification. The main toxic cyanobacteria present in these reservoirs were Aphanocapsa sp., Cylindrospermopsis sp., Leptolyngbya sp., Limnothrix sp., Microcystis sp., Oscillatoria sp., Planktolyngbya sp., Planktotrix sp., and Pseudanabaena sp. The dominant bloom-forming genera in the water samples from Bueng Nong Khot and Bueng See Than were Microcystis sp. and Cylindrospermopsis sp., respectively. Enzyme-linked immunosorbent assays specific for cyanotoxins were performed to detect and quantify microcystins and cylindrospermopsins, with the highest average microcystins content (0.913 μgL^?1) being found in the sample collected from Bueng Nong Khot and the highest average cylindrospermopsins content (0.463 μgL^?1) being found in the sample collected from Bueng See Than. The application of 16S rRNA analyses to cyanobacterial isolates BKN2, BNK1, BNK2, and BST1 indicated that these isolates are most closely related to Limnothrix planctonica (JQ004026) (98 % similarity), Leptolyngbya sp. (FM177494) (99 % similarity), Microcystis aeruginosa (DQ887510) (99 % similarity), and Limnothrix redekei (FM177493) (99 % similarity), respectively.     

Removal of hexavalent chromium from contaminated ground water using zero-valent iron nanoparticles

Batch experiments were conducted on ground water samples collected from a site contaminated with Cr(VI) to evaluate the redox potential of zero-valent iron (Fe⁰) nanoparticles for remediation of Cr(VI)-contaminated ground water. For this, various samples of contaminated ground water were allowed to react with various loadings of Fe⁰ nanoparticles for a reaction period of 60 min. Data showed 100% reduction of Cr(VI) in all the contaminated ground water samples after treatment with 0.20 gL⁻¹ of Fe⁰ nanoparticles. An increase in the reduction of Cr(VI) from 45% to 100% was noticed with the increase in the loading of Fe⁰ nanoparticles from 0.05 to 0.20 gL⁻¹. Reaction kinetics of Cr(VI) reduction showed pseudo first-order kinetics with rate constant in the range of 1.1 × 10⁻³ to 3.9 × 10⁻³ min⁻¹. This work demonstrates the potential utility of Fe⁰ nanoparticles in treatment and remediation of Cr(VI)-contaminated water source.     

Assessment of seawater impact using major hydrochemical ions: a case study from Sadras, Tamilnadu, India

The impact of seawater intrusion was investigated using major hydrogeochemical ions to evaluate the origin of salinity in Sadras watershed located between Buckingham Canal and Bay of Bengal in the southeastern coast of India. From empirical data collected twice during pre- and post-monsoon seasons, it was found that groundwater was slightly acidic to mildly alkaline, and more than 44% of groundwater samples had EC > 3,000 ??S/cm in both the seasons. Results of principle component analysis (PCA) showed that Na^?+?, Cl^???, Mg^2?+?, and SO $_{4}^{\,\, 2-}$ concentrations had the highest loading factor and the samples affected by saline/seawater were separated from the cluster. Hydrochemical processes that accompany the saline/seawater were identified using ionic changes. It was observed during sampling periods that the mixing due to saline/seawater intrusion varied from 4.82?C7.86%. Negative values of ionic change (e _change) for Na^?+? and K^?+? decreased with the increasing fraction of seawater. Furthermore, salinity, sodium adsorption ratio, percentage of sodium Na (%), and exchangeable sodium percentage in well samples showed that groundwater was unsuitable for irrigation purposes.     

A comparison of sampling techniques and summary indices for assessment of water quality in the Yamaska River,Québec,based on benthic macroinvertebrates

The Yamaska River drainage basin in Quebec, Canada, is intensively farmed and heavily polluted with poorly treated domestic and industrial wastes. We investigated the responses of the resident and colonizing components of the benthic macroinvertebrate community to municipal/industrial versus agricultural pollution in the basin, and evaluated the performances of seven diversity and biotic indices for assessing water quality. Samples of riffle-dwelling, infaunal and colonizing invertebrates were collected from 13 stations representing a wide range of types and degrees of pollution using Surber, scoop and artificial substrate samplers. The data were summarized using the indices S (number of taxa), N (number of individuals), H (Shannon-Wiener's diversity index), D (Simpson's diversity index), BBI (Belgian Biotic Index), TBI (a modification of Hilsenhoff's Biotic Index), % CHIR (percentage of arthropods consisting of Chironomidae) and %OLIGO (percentage of total organisms consisting of Oligochaeta). Different components of the community generated somewhat different assessments and were, therefore, complementary. Community composition, expressed as the percentage of individuals contributed by major taxonomic groups, reflected the kinds of stresses at a station more consistently than did any of the indices. S and TBI came closest to ranking control, agricultural and municipal/industrial sites in accordance with our a priori classification, both between months and among sampling methods. %OLIGO usually separated municipal/industrial sites from control sites. Other indices were found to be less sensitive, accurate or temporally stable, or were otherwise inappropriate for use with certain sampling methods or for certain types of pollution. With most of our samples, all of the summary indices suggested that the impact of agricultural practices on stream ecosystems may be as severe as the impacts of municipal and industrial wastes.     

Dynamics of harmful dinoflagellates driven by temperature and salinity in a northeastern Mediterranean lagoon

To attempt to determine the effects of temperature and salinity on the dynamics of the dinoflagellate community, a monthly sampling was carried out from October 2008 to March 2009 at eight sampling stations in Ghar El Melh Lagoon (GML; Mediterranean Sea, Northern Tunisia). Dinoflagellates were dominant among plankton, accounting for 73.9 % of the lagoon’s overall plankton community, and were comprised of 25 different species among which 17 were reported in the literature as harmful. While no significant difference was found in the distribution of dinoflagellates among the stations, a strong monthly difference was observed. This temporal variability was due to an increase in the abundance of Prorocentrum micans from December to February, leading to a strong decrease in the Shannon diversity index from station to station. At the onset of P. micans development, dinoflagellate abundances reached 1.26.10⁵ cells l^?1. A redundance analysis indicates that both temperature and salinity have a significant effect on the dynamics of the dinoflagellate community. Using a generalized additive model, both temperature and salinity appear to have significant nonlinear relationships with P. micans abundances. Model predictions indicate that outbreaks of P. micans may occur at a temperature below 22.5 °C and with salinity above 32.5. We discuss our results against a backdrop of climate change which, by affecting temperature and salinity, is likely to have an antagonistic impact on P. micans development and subsequently on the dinoflagellate dynamics in GML.     

Phthalates removal efficiency in different wastewater treatment technology in the Eastern Cape,South Africa

The removal capacity of different wastewater treatment plant (WWTP) technologies adopted in rural areas for phthalate was investigated in the Eastern Cape, South Africa. Wastewater samples collected from three selected WWTPs which use activated sludge (AS), trickling filter (TF), and oxidation pond (OP) technology were extracted using the solid-phase extraction method followed by gas chromatography-mass spectrometry (GC-MS) analysis. The six selected phthalate esters (PAEs) dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), benzyl butyl phthalate (BBP), di(2-ethyl hexyl) phthalate (DEHP), and di-n-octyl phthalate (DOP) were detected in all the samples collected from the WWTPs. DBP was the most abundant compound in the influent, effluent, and sludge samples with a maximum detection of 2497 μgL^?1, 24.2 μgL^?1, and 1249 μg/g dW, respectively, followed by DEHP and BBP. There was a relatively high removal capacity achieved by AS in Alice, TF in Berlin, and OP in Bedford with a removal efficiency that varied between 77 and 99%, 76 and 98%, and 61 and 98%, respectively. A high significant correlation of PAE removal with total suspended solids (TSS) and turbidity suggests that the removal performance proceeded more through adsorption on settling particles and sludge than on biodegradation. However, the concentrations of PAEs detected in the final effluent and sludge samples exceeded acceptable levels allowed internationally for a safe aquatic environment. AS may have exhibited a more stable and better performance across the different seasons; however, pollution source control still deserves a special attention to prevent the risk posed by these micropollutants.     

The assessment of spatial distribution of soil salinity risk using neural network

Soil salinity in the Aral Sea Basin is one of the major limiting factors of sustainable crop production. Leaching of the salts before planting season is usually a prerequisite for crop establishment and predetermined water amounts are applied uniformly to fields often without discerning salinity levels. The use of predetermined water amounts for leaching perhaps partly emanate from the inability of conventional soil salinity surveys (based on collection of soil samples, laboratory analyses) to generate timely and high-resolution salinity maps. This paper has an objective to estimate the spatial distribution of soil salinity based on readily or cheaply obtainable environmental parameters (terrain indices, remote sensing data, distance to drains, and long-term groundwater observation data) using a neural network model. The farm-scale (∼15 km²) results were used to upscale soil salinity to a district area (∼300 km²). The use of environmental attributes and soil salinity relationships to upscale the spatial distribution of soil salinity from farm to district scale resulted in the estimation of essentially similar average soil salinity values (estimated 0.94 vs. 1.04 dS m⁻¹). Visual comparison of the maps suggests that the estimated map had soil salinity that was uniform in distribution. The upscaling proved to be satisfactory; depending on critical salinity threshold values, around 70–90% of locations were correctly estimated.     

Applications of behavioral science to biodiversity management in agricultural landscapes: conceptual mapping and a California case study

Regime shifts of major salinity constituents (Ca, Mg, Na, K, SO₄, Cl, HCO₃, and NO₃) in the lower Salinas River, an agricultural ecosystem, can have major impacts on ecosystem services central to continued agricultural production in the region. Regime shifts are large, persistent, and often abrupt changes in the structure and dynamics of social-ecological systems that occur when there is a reorganization of the dominant feedbacks in the system. Monitoring information on changes in the system state, controlling variables, and feedbacks is a crucial contributor to applying sustainability and ecosystem resilience at an operational level. To better understand the factors driving salinization of the lower Salinas River on the central coast of California, we examined a 27-year record of concentrations of major salinity constituents in the river. Although limited in providing an understanding of solute flux behavior during storm events, long-term “grab sampling” datasets with accompanying stream discharges can be used to estimate the actual history of concentrations and fluxes. We developed new concentration–discharge relationships to evaluate the dynamics of chemical weathering, hydrological processes, and agricultural practices in the watershed. Examinations of long-term records of surface water and groundwater salinity are required to provide both understanding and perspective towards managing salinity in arid and semi-arid regions while also enabling determination of the influence of external climatic variability and internal drivers in the system. We found that rock weathering is the main source of Ca, Mg, Na, HCO₃, and SO₄ in the river that further enables ion exchange between Ca, Mg, and Na. River concentrations of K, NO₃, and Cl were associated with human activities while agricultural practices were the major source of K and NO₃. A more direct anthropogenic positive trend in NO₃ that has persisted since the mid-1990s is associated with the lag or memory effects of field cropping and use of flood irrigation. Event to inter-year scale patterns in the lower Salinas River salinity are further controlled by antecedent hydrologic conditions. This study underscores the importance of obtaining long-term monitoring records towards understanding watershed changes-of-state and time constants on the range of driving processes.

     

Seasonal and spatio-temporal distribution of faecal-indicator bacteria in Tyume River in the Eastern Cape Province, South Africa

We assessed the incidence of faecal-indicator bacteria in Tyume River over a 12-month period between August 2010 and July 2011. Total coliforms, faecal coliforms and enterococci were determined by the membrane filtration method. Total coliforms were detected in counts ranging from 2.1?×?10² to 3.4?×?10⁴?CFU/100 ml. Faecal coliform counts ranged from 1?×?10² to 1.6?×?10⁴?CFU/100 ml while enterococci counts were in the range of 3.3?×?10¹ to 5.1?×?10³?CFU/100 ml. Indicator bacteria counts increased from upstream to downstream sampling sites. Counts of indicator bacteria at all sites were significantly affected by seasonal changes. The bacteriological qualities of the river water were poor, exceeding the guideline of 200 CFU/100 ml and 33 CFU/100 ml for faecal coliforms and enterococci, respectively, for recreational water. Faecal coliform counts also exceeded the 1,000 CFU/100 ml guideline for water used in fresh produce irrigation. Microbial source tracking results showed that faecal pollution was predominantly of human origin during spring at all sampling sites. During other seasons, human faecal pollution was largely confined to midstream and downstream sampling sites. Generally, the presence of faecal-indicator bacteria in the river water samples suggests faecal pollution of this freshwater resource, raising the possibility of the presence of pathogenic microorganisms in the water and a threat to public health.     

The effects of salinity,temperature and sediment on the toxicity of copper to juvenile Hediste (Nereis) diversicolor (O. F. Muller)

Without sediment, increasing salinity (7.3 to 29.2) and increasing temperature (12 to 22 °C) reduced the toxicity of copper to juvenile Hediste diversicolor. The LC₅₀ values ranged from 357 gL^-1 in 7.3 to 513 g L^-1 in 29.2 at 12°C and from 247 to 500 g L^-1 at 22°C. In deionized water all the juvenile were dead in all solutions to which copper was added (100 to 600 g L^-1). Dead worms were swollen and everted their pharynxs. In higher doses of copper (500 to 600 g L^-1) the worms were abnormal in behaviour in all salinities (0 to 29.2). The ability to swim or crawl was disturbed.With sediments increasing temperature and increasing salinity increased the toxicity of copper to the worms. The LC₅₀ values ranged from 3200 to 4100 g L^-1 at 22°C. The response of the juvenile to copper was antagonistic to increasing temperature and salinity and synergistic to increasing salinity and increasing temperature without and with the sediment respectively.     

Assessment of the labile fractions of copper and zinc in marinas and port areas in Southern Brazil

The dissolved labile and labile particulate fractions (LPF) of Cu and Zn were analyzed during different seasons and salinity conditions in estuarine waters of marina, port, and shipyard areas in the southern region of the Patos Lagoon (RS, Brazil). The dissolved labile concentration was determined using the diffusive gradients in thin films technique (DGT). DGT devices were deployed in seven locations of the estuary for 72 h and the physicochemical parameters were also measured. The LPF of Cu and Zn was determined by daily filtering of water samples. Seasonal variation of DGT–Cu concentrations was only significant (p?<?0.05) at one shipyard area, while DGT–Zn was significant (p?<?0.05) in every locations. The LPF of Cu and Zn concentrations demonstrated seasonal and spatial variability in all locations, mainly at shipyard areas during high salinity conditions. In general, except the control location, the sampling locations showed mean variations of 0.11–0.45 μg?L^?1 for DGT–Cu, 0.89–9.96 μg?L^?1 for DGT–Zn, 0.65–3.69 μg?g^?1 for LPF–Cu, and 1.35–10.87 μg?g^?1 for LPF–Zn. Shipyard areas demonstrated the most expressive values of labile Cu and Zn in both fractions. Strong relationship between DGT–Zn and LPF–Zn was found suggesting that the DGT–Zn fraction originates from the suspended particulate matter. Water salinity and suspended particulate matter content indicated their importance for the control of the labile concentrations of Cu and Zn in the water column. These parameters must be taken into consideration for comparison among labile metals in estuaries.     

Assessment and occurrence of various heavy metals in surface water of Ganga river around Kolkata: a study for toxicity and ecological impact

A study was conducted during November, 2005–October, 2006 to evaluate the surface water quality of river Ganga around Kolkata. The samples were analyzed for a number of physico-chemical parameters using standard laboratory procedures and giving prime thrust to determine the heavy metal concentrations (Fe, Mn, Cu, Zn, Pb, Cd, Cr, and Ni) of surface water at four different locations of the river Ganga around Kolkata from two points (middle of the river stream and a discharge point) at each location. Out of 96 samples analyzed, Fe, Mn, Cu, Zn, and Ni were detected in 71, 47, 38, 60, and 45 samples in the concentrations ranging from 0.013 to 5.49, 0.022 to 1.78, 0.003 to 0.033, 0.005 to 0.293, and 0.045 to 0.24 mg L^???1, respectively. Cd and Pb were detected in six and 21 samples in the range of 0.005 to 0.006 and 0.05 to 0.53 mg L^???1, respectively. But Cr was not detected in any of the samples analyzed. The metals exhibited no significant variation with respect to sampling locations as well as discharge points. However, the concentration of those metals varied with season, being higher in rainy and lower in winter season.     

The effects of the environment and ecology projects on lake management and water quality

In this study, the characteristics, benefits, and effects of the environment and ecology project, which has been implemented in Turkey for the first time to restore the natural life that has been spoilt and the ecological balance of Lake Bafa located in Great Meander Basin, are searched. Moreover, the water samples taken from the stations that were spotted in the lake have been analyzed for the physical and chemical changes taking place in water quality before and after the project. The water cycle occurring as a result of giving water that was raised in Great Meander River by the Rubber regulator, which is the most important element of the project, through the Serçin inlet and feeder channel; and draining the saline and low-quality water to the river bed of the Great Meander, will improve the water quality, the natural life, and the ecological balance of the lake in time. Thanks to the water given to the lake within the scope of project, the salinity of the lake water decreased from 25,500 to 22,500 mmhos cm^???1. The electrical conductivity, Na^?+?, Mg^?+?2, Ca^?+?2, Cl^???, $\text{CO}_\text{3} ^{-\text{2}}In this study, the characteristics, benefits, and effects of the environment and ecology project, which has been implemented in Turkey for the first time to restore the natural life that has been spoilt and the ecological balance of Lake Bafa located in Great Meander Basin, are searched. Moreover, the water samples taken from the stations that were spotted in the lake have been analyzed for the physical and chemical changes taking place in water quality before and after the project. The water cycle occurring as a result of giving water that was raised in Great Meander River by the Rubber regulator, which is the most important element of the project, through the Ser?in inlet and feeder channel; and draining the saline and low-quality water to the river bed of the Great Meander, will improve the water quality, the natural life, and the ecological balance of the lake in time. Thanks to the water given to the lake within the scope of project, the salinity of the lake water decreased from 25,500 to 22,500 mmhos cm( - 1). The electrical conductivity, Na+, Mg+2, Ca+2, Cl(-), CO3(-2), HCO3(-), and the amount of the organic substances were found as over the appropriate values for fishery. Besides, the decreases in the amounts of NO3(-), HN3(-) and PO4(-3) affect the living beings in the lake negatively. In addition, the measures to take are specified, so that the natural life of the Lake and the ecological balance can renew themselves within a short time.     

Perfluorooctane sulfonate (PFOS) distribution and effect factors in the water and sediment of the Yellow River Estuary, China

The distribution of perfluorooctane sulfonate (PFOS) was investigated in a total of 15 water and sediment samples from the Yellow River Estuary, China in April 2011. The results indicated that the concentrations of PFOS in the water and sediment samples averaged 157.5 ng/L and 198.8 ng/g and ranged from 82.30 to 261.8 ng/L and 75.48 to 457.0 ng/g, respectively. The concentrations of PFOS in the sediment column increased from 45.32 to 379.98 ng/g with the decrease of the sampling depth, which showed that the increased PFOS pollution in the sediment appeared in this region in over recent years. The distribution coefficient (K _d) of PFOS between water and sediment linearly increased from 0.37 to 4.80 L/g as the salinity (S‰) increased from 0.18 to 4.47. Correlation analysis revealed that K _d was significantly and positively correlated to the contents of total organic carbon and clay of the sediment, and salinity. Therefore, salinity was an important parameter in controlling the sediment–water interactions and the fate or transport of PFOS in the aquatic environment. The results of this study showed that the estuary was an important sink for PFOS and suggested that PFOS might be carried with the river water and transported for long distances before it reached to the sea and largely scavenged to the sediment in the estuaries due to the change in salinity.     

Assessment of water systems for contaminants from domestic and industrial sewages

The State of Minas Gerais represents one of Brazil's most outstanding mining resources. The contamination of river waterfrom kaolin processing activities may be harmful to people inthe way of slow but chronic poisoning. On the other hand, the discharge of untreated or inadequately treated domestic sewage into aquatic environments can also cause deleterious effects to the health. However, no reliable figures are available for pollutant occurrences in river water. This draws attention to thevery precarious situation that exists with respect to pollutionby organic and inorganic toxic wastes, especially with respect to humans and fauna in all its expressions. Thus, with the purpose of establishing a preliminary report to trace out industrialisation outcomes, samples of river water, vegetation and fish were collected and analysed to detect pollutant inputs.The concentration of metals was determined in suspended particle,vegetation and fish, while those of nitrite, nitrate, phosphateand chloride were determined in river water samples. The concentration of dissolved oxygen (DO) was measured in river water at the time of collection. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were also determined. Metalinputs in the samples analysed appeared to be related to effluentdischarges into the rivers. The suspended particles showed highconcentrations (in mg kg^-1) of zinc (62 600) and aluminium(559 000), while vegetation samples collected near rivers wereheavily contaminated with iron (7680). The fishes examined werecontaminated with chromium (1.5 mg kg^-1). In general, the concentrations of nitrite, nitrate, chloride, phosphate and BOD in river water were lower than the maximum values established bythe Brazilian Environmental Standards.     

Monitoring and risk assessment of pesticides in a tropical river of an agricultural watershed in northern Thailand

The increasing application of pesticides in the uplands of northern Thailand has increased the transfer of pesticides to surface water. To assess the risk of pesticide use for stream water quality, we monitored the concentrations of seven pesticides (atrazine, dichlorvos, chlorpyrifos, dimethoate, chlorothalonil, (α-, β-) endosulfan, cypermethrin) frequently used in the Mae Sa watershed (77 km²) in water and sediment samples over a period of one and a half years (2007–2008). All investigated pesticides were recorded in the river. Chlorpyrifos was detected most often in water samples (75 % at the headwater station), while cypermethrin was most often found in riverbed (86 %) and in all suspended sediment samples. The highest concentrations of the pesticides were detected during the rainy season. About 0.002 to 4.1 % by mass of the applied pesticides was lost to surface water. The risk assessment was based on the risk characterization ratio (RCR). The RCRs of dichlorvos in water, (α-, β-) endosulfan, and cypermethrin in water and sediments were higher than unity indicating that they are likely to pose a threat to aquatic ecosystem. Finally, we discuss the role of sampling design on ecotoxicological risk assessment. Our study shows that pesticide contamination of surface waters is an environmental issue in the Mae Sa watershed and that measures need to be undertaken to reduce the loss of pesticides from soil to surface waters.     

Anthropogenic nexus on organochlorine pesticide pollution: a case study with Tamiraparani river basin,South India

The levels of 17 organochlorine pesticides residues (OCPs) in surface water and sediments from Tamiraparani river basin, South India were investigated to evaluate their potential pollution and risk impacts. A total of 96 surface water and sediment samples at 12 sampling stations were collected along the river in four seasons during 2008–2009. The ΣOCP concentrations in surface water and sediments were in the range of 0.1 to 79.9 ng l⁻¹ and 0.12 to 3,938.7 ng g⁻¹ dry weight (dw), respectively. Among the OCPs, the levels of dichlorodiphenyltrichloroethanes (DDTs), aldrin, dieldrin, cis-chlordane, trans-chlordane, and mirex were dominant in the sediments. The dominant OCPs in water samples are heptachlor, o,p′-DDE, dieldrin, o,p′-DDD, and mirex, which show different source of contamination pattern among sampling seasons. The distribution pattern of DDTs, hexachlorocyclohexane, and other OCPs in the present study shows heterogenic nature of nonpoint source of pollution. Notable contamination of water and sediment sample that was observed in upstream (S2) 58 ng l⁻¹ and downstream (S11) 1,693 ng g⁻¹ dw explains agricultural and municipal outfalls, whereas frequent damming effect reduces the concentration level in the midstream. The overall spatial–temporal distribution pattern of ΣOCP residues are illustrated by GIS package.     

A geographical approach to tracking Escherichia coli and other water quality constituents in a Texas coastal plains watershed

Diffuse sources of surface water pathogens and nutrients can be difficult to isolate in larger river basins. This study used a geographical or nested approach to isolate diffuse sources of Escherichia coli and other water quality constituents in a 145.7-km² river basin in south central Texas, USA. Average numbers of E. coli ranged from 49 to 64,000 colony forming units (CFU) per 100 mL depending upon season and stream flow over the 1-year sampling period. Nitrate-N concentrations ranged from 48 to 14,041 μg?L^?1 and orthophosphate-P from 27 to 2,721 μg?L^?1. High concentrations of nitrate-N, dissolved organic nitrogen, and orthophosphate-P were observed downstream of waste water treatment plants but E. coli values were higher in a watershed draining an older part of the city. Total urban land use explained between 56 and 72 % of the variance in mean annual E. coli values (p?<?0.05) in nine hydrologically disconnected creeks. Of the types of urban land use, commercial land use explained most of the variance in E. coli values in the fall and winter. Surface water sodium, alkalinity, and potassium concentrations in surface water were best described by the proportion of commercial land use in the watershed. Based on our nested approach in examining surface water, city officials are able to direct funding to specific areas of the basin in order to mitigate high surface water E. coli numbers and nutrient concentrations.     

A simple,cost-effective multispecies toxicity test using organisms with a cosmopolitan distribution

Difficulties in making accurate, ecosystem-level predictions of environmental effects of chemicals, mixtures, and effluents based solely on the results of tests on single species have necessitated the development of more environmentally realistic, predictive testing methods. This paper describes a multispecies, community-level toxicity test based on the colonization of artificial substrates by microbial species. Tests examined the colonization of initially barren polyurethane foam artificial substrates by Protozoa from a species source colonized in a natural system. Differences in colonization were examined in microecosystems amended with low levels of cadmium, a very toxic heavy metal, and TFM, an organic biocide used against larval sea lamprey. Tests examined differences in colonization over 28 days. For cadmium, effect levels were estimated to be near 1 g 1^–1, in the low range of effect levels determined from chronic single species tests. For TFM, effect levels were estimated to be between 1 and 10 ppm, overlapping the concentrations used in environmental applications. The colonization response, which depends on naked microbial cells reproducing and migrating through toxicant amended water to new substrates, is very sensitive. Tests based on colonization can be adapted to use species from a target receiving system or can use species from a designated natural source. Field validation of these tests can employ nearly identical methods to those used in laboratory studies to assess the accuracy of predictions based on test system data.