Showing papers on "Water quality published in 1996"

Estimation of heavy metals in drinking water and development of heavy metal pollution index

Abstract: Four heavy metals (Copper, Cadmium, Lead and Zinc) are monitored in drinking water at twelve important residential areas using DPASV Technique. The results indicate the water to free of heavy metal pollution. The data monitored have been used to compute Heavy metal pollution index (HPI) using weighted arithmetic mean method and the proposed Pollution Index (HPI) seems to be applicable in the assesement of overall water quality with respect to heavy metal pollution.

Control of water pollution from agriculture

Abstract: Agricultural operations can contribute to water quality deterioration through the release of several materials into water: sediments, pesticides, animal manures, fertilizers and other sources of inorganic and organic matter. This ''guidelines'' document on control and management of agricultural water pollution has the objectives of delineating the nature and consequences of agricultural impacts on water quality, and of providing a framework for practical measures to be undertaken by relevant professionals and decision-makers to control water pollution.

Invasive plants and water resources in the Western Cape Province, South Africa: modelling the consequences of a lack of management.

Abstract: 1. The invasion of fynbos shrublands by woody weed species can reduce the water yield from catchment areas dramatically. We modelled the consequences of uncontrolled invasion on water yield using a geographical information system (Arc/Info). 2. Five important processes were recognized : the occurrence of fire ; the spread and establishment of alien plants after fire ; rainfall-to-run-off ratios ; growth and changes in biomass between fires ; and effects of these changes on streamflow. 3. The simulations of water yield were modelled with the Arc/Info GRID module using a 200 x 200-m grid. It was assumed that the interval between fires was 15 years and that proliferation and dispersal of alien plants took place only after fires. 4. Between fires, the model simulated the growth of the vegetation and its effects on streamflow, using relationships between rainfall and run-off, and run-off and above-ground biomass. 5. Results for the Kogelberg area in the Western Cape Province showed that alien plants invaded about 40% of the grid cells within 50 years. Cover of alien plants increased from an initial estimate of 2.4% to 62.4% after 100 years. 6. Invasion of catchment areas would result in an average decrease of 347 m 3 of water per hectare per year over 100 years, resulting in average losses of more than 30% of the water supply to the city of Cape Town. In individual years, where large areas would be covered by mature trees, losses would be much greater. 7. In addition, invasion of fynbos by alien plants will cause the extinction of many plant species, increase the intensity of fires, destabilize catchment areas with resultant erosion and diminished water quality, and decrease the aesthetic appeal of mountain areas. 8. Control of alien weed species is necessary to avert the above impacts, and the costs of control operations could be justified by the savings achieved in maintaining adequate water run-off from stable catchments in the long term.

The evaluation of waste, surface and ground water quality using the Allium test procedure.

Abstract: The bulbs of Allium cepa were grown in test liquids of various pollution levels as follows: undiluted industrial and municipal waste water; biological treatment plant output water; water from the Drava river upstream and downstream of the city of Maribor; and non-chlorinated drinking water as a negative control test. The paper presents the response of the Allium cepa genetic material to the presence of potential cytotoxic and genotoxic substances in test liquids and the suitability of the Allium cepa testing procedure as a method for short-term determination of water pollution level. The suitability of the Allium test procedure as a system for environmental monitoring is presented. The influence of water pollution on macroscopic and cytologic parameters of the common onion by application of the biological testing method was examined. The macroscopic parameter was inhibition of root growth. The cytological parameters were: aberrant cells in metaphase and anaphase, index of micronuclei appearance and inhibition of cell division. The possibility of categorization the different polluted test liquids into quality classes is presented according to the influence of the test liquids on macroscopic and cytologic parameters. Test liquids are divided into 8 quality classes: the first class is the least polluted surface waters, the second and the third classes are more polluted surface water, the fourth and the fifth classes are biological treatment plant output waters, the sixth till the eighth quality classes are untreated waste waters. The most polluted test liquids (untreated industrial and municipal waste waters) caused sublethal and even lethal effects. The most polluted tested liquids cause the inhibition of root growth over 50% (even up to 74%), decrease of mitotic index over 36% (even up to 66%), increase of presence of interphase cells with micronuclei over 3% and increase of presence of aberrant cells for more than 10 times in comparison to control test.

Microbial quality of water supply in distribution systems

Abstract: Characterizing the Distribution System: Microbial Issues Distribution System Habitats Distribution Water Temperature Trends Water Supply Transient Time Operational Factors Joint Responsibility for Water Quality Creating Microbial Quality in Drinking Water Raw Source Microbial Composition Microbial Control through Treatment Water Supply Storage and Distribution Building Plumbing Networks Attachment Devices Biological Profiles in Drinking Water Primary Microbial Groups Free-Living Amoeba and Macroinvertebrates: Protectors and Amplifiers of Bacteria Opportunistic Organisms and the Water Supply Connection Biofilms in Water Distribution Systems Characterizing Biofilm Nutrients: A Case for Biological Instability of Water Supply Water Temperature Stimulation Physical Status of Pipe Sediments Scenarios for Undetected Coliform Passages Evaluating the Public Health Significance of Biofilm Characterizing Microbial Quality in Water Supply Introduction Heterotrophic Bacteria Coliform Detection Substitute Criteria: A Word of Caution Nuisance Organisms Infrastructure Construction Acceptance Laboratory Credibility through Certification Monitoring Strategies to Characterize Water Quality Introduction Evaluating the Strategy Sample Collection and Sample Stability in Transit Special Considerations - Small Systems Networks Large System Characteristics Consolidated Systems Coliform Occurrences in Compliance Monitoring Special Purpose Monitoring Microbial Breakthroughs in Changing Source, Treatment, or Supply Parameters Introduction Factoring Source Water Characteristics Plant Operating Practices Treatment Modifications Disinfection Alternatives Impacts on Distribution Water Quality Waterborne Pathogen Invasions: A Case for Water Quality Protection in Distribution Characterizing Freshwater Quality Waterborne Pathogenic Agents Utilizing Multiple Barriers to Pathogen Passage Waterborne Pathogen Invasions: Case History Examples Pathogen Search in Waterborne Outbreaks In Retrospect - Municipal Sewage Collection Systems Stormwater Runoff Non-Metered Service Unaccounted Water Losses Water Storage Tank Structures System Flushing Distribution Residuals Water Pressure Responses to Microbial Quality Changes in Water Supply Distribution Laboratory Assistance Initial Action Responses Persistent Non-Compliance Response Sanitary Survey Approach Searching for Risks in Water Supply In Retrospect Public Awareness of Water Quality Problems Public Perception of Health Risks in Water Supply Mass Media and Public Awareness A Study of Media Attention to Technical Reality Public Relations Programs Public Awareness: What Have We Learned? Appendix: Field Investigation Check List Index

Issues, Impacts, and Implications of Shrimp Aquaculture in Thailand

Abstract: Water quality impacts to and from intensive shrimp aquaculture in Thailand are substantial. Besides the surface and subsurface salinization of freshwaters, loadings of solids, oxygen-consuming organic matter, and nutrients to receiving waters are considerable when the cumulative impacts from water exchange during the growout cycle, pond drainage during harvesting, and illegal pond sediment disposal are taken into account. Although just beginning to be considered in Thailand, partial recirculating and integrated intensive farming systems are producing promising, if somewhat limited, results. By providing on-site treatment of the effluent from the shrimp growout ponds, there is less reliance on using outside water supplies, believed to be the source of the contamination.

Chemistry of the Environment

Abstract: I. ENERGY. 1. Energy Flows and Supplies. Prologue on Energy and Sustainability. Natural Energy Flows. Human Energy Consumption. Human Energy Sources. 2. Fossil Fuels. Carbon Cycle. Origins of Fossil Fuels. Fuel Energy. Petroleum. Gas. Coal. Decarbonization. 3. Nuclear Energy. Nuclei, Isotopes, and Radioactivity. Naturally Occurring Radioisotopes. Decay Chains: The Radon Problem. Radioactivity: Biological Effects of Ionizing Radiation. Radiation Exposure. Fission. Hazards of Nuclear Power. Is Nuclear power Part of the Future? Fusion. 4. Renewable Energy. Solar Heating. Solar Thermal Electricity. Photovoltaic Electricity. Biomass. Hydroelectricity. Wind Power. Ocean Energy. Geothermal Energy. 5. Energy Utilization. Heat Engine Efficiencies. Fuel Cells. Space Heating, Cogeneration. Electricity Storage: The Hydrogen Economy. The Materials Connection. Systems Efficiency. Energy and Society. II. ATMOSPHERE. 6. Climate. Radiation Balance. Albedo: Particles and Clouds. Greenhouse Effect. Climate Modeling. International Agreements on Greenhouse Gases. 7. Oxygen Chemistry. Nitrogen Oxides: Free Energy. Nitrogen Oxides: Kinetics. Free Radical Chain Reactions. 8. Stratospheric Ozone. Atmospheric Structure. Ultraviolet Protection by Ozone. Ozone Chemistry. Catalytic Destruction of Ozone. Polar Ozone Destruction. Ozone Projections. CFC Substitutes. 9. Air Pollution. Pollutants and Their Effects. Photochemical Smog. Emission Control. Reformulated Gasoline: Oxygenates. III. HYDROSPHERE/LITHOSPHERE. 10. Water Resources. Global Perspective. Irrigation. Groundwater. U.S. Water Resources. The Oceans. Water as Solvent and as a Biological Medium. 11. From Clouds to Runoff: Water as Solvent. Unique Properties of Water. Acids, Bases, and Salts. Conjugate Acids and Bases Buffers. Water in the Atmosphere: Acid Rain. 12. Water and the Lithosphere. Earth as Acid-Base Reactor. Organic and Inorganic Carbon Cycles. Weathering and Solubilization Mechanisms. Effects of Acidification. 13. Oxygen and Life. Redox Reactions and Energy. Aerobic Earth. Water as Ecological Medium. 14. Water Pollution and Water Treatment. Water Use and Water Quality: Point and Nonpoint Sources of Pollution. Regulation of Water Quality. Water and Sewage Treatment. Health Hazards. IV. BIOSPHERE. 15. Nitrogen and Food Production. Nitrogen Cycle. Agriculture. Nutrition. 16. Pest Control. Insecticides. Herbicides. Genetically Modified Organisms (GMOs). 17. Toxic Chemicals. Acute and Chronic Toxicity. Cancer. Hormonal Effects. Persistent Organic Pollutants: dioxins and PCBs. Toxic Metals. Appendix: Organic Structure. Hydrocarbons: Alkanes. Branched Chains Isomers. Rings. Unsaturated Hydrocarbons. Molecular Shape. Carbon Framework Representations. Aromatic Compounds. Hetero-Atoms Functional Groups. Index.

Hydrology: Water Quantity and Quality Control

Abstract: Hydrology: Water Quantity and Quality Control was developed in response to the educational needs of scientists, engineers, planners, and environmentalists to aid in the understanding and solving of water control problems. As the demand for quantitative solutions increase, we find that both the scientific and lay communities can benefit from the many example problems of quantitative nature in the text. We believe the text can also be used to aid in the design of systems using hydrologic data. The text has been used in engineering curriculums as a total design content course. We incorporate hydrologic concepts, ideas, and mode ls into comprehensive water control studies. Comprehensive water quality and quantity studies are necessary when water supplies are developed or land use changes are contemplated. The emphasis of the text materials are placed on (1) measurement and interpretation of hydrologic cycle data, such as precipitation, evaporation, infiltration, and runoff, and (2) control of runoff water quality and quantity. This new edition of Hydrology: Water Quantity and Quality Control is a major revision of our previously successful text. The first edition was published in 1990, and comments from those using the text in an academic environment provided the interest for rewriting. This new version of the text includes expanded treatment of water quality and control, thus the term water quality has been included in the title. Additional problems have been added to the end of each chapter. Case studies relating to design problems have been incorporated to better explain the assumptions and choice of values for the parameters of models. An additional appendix was added to suggest classroom or laboratory problems that support and help strengthen lecture and reading materials.

A comparative analysis of eutrophication patterns in a temperate coastal lagoon

Abstract: The coastal bays and lagoons of Maryland extend the full length of the state's Atlantic coast and compose a substantial ecosystem at the land-sea margin that is characterized by shallow depth, a well-mixed water column, slow exchange with the coastal ocean, and minimal freshwater input from the land For at least 25 years, various types of measurements have been made intermittently in these systems, but almost no effort has been made to determine if water quality or habitat conditions have changed over the years or if distinctive spatial gradients in these features have developed in response to changing land uses The purpose of this work was to examine this fragmented database and determine if such patterns have emerged and how they may be related to land uses Turbidity, dissolved inorganic phosphate, algal biomass, and primary production rates in most areas of the coastal bays followed a regular seasonal pattern, which was well correlated with water temperature Nitrate concentrations were low (<5 μM), and only modestly higher in tributary creeks (<20 μM) Additionally, there was little indication of the spring bloom typical of river-dominated systems There does appear to be a strong spatial gradient in water quality conditions (more eutrophic in the upper bays, especially in tributary creeks) Comparisons of water quality data collected between 1970 and 1991 indicate little temporal change in most areas and some small improvements in a few areas, probably related to decreases in point-source discharges Seagrass communities were once extensive in these systems but at present are restricted to the eastern portion of the lower bays where water clarity is sufficient to support plant survival Even in these areas, seagrass densities have recently decreased Examination of diel dissolved oxygen data collected in the summer indicates progressively larger diel excursions from lower to upper bays and from open bays to tributary subsystems; however, hypoxic conditions (<2 mg 1−1) were rarely observed in any location Nitrogen input data (point, surface runoff, groundwater and atmospheric deposition to surface waters) were assembled for seven regions of the coastal bay system; annual loading rates ranged from 24 g N m−2 yr−1 to 397 g N m−2 yr−1 Compared with a sampling of loading rates to other coastal systems, those to the upper and lower bays were low while those to tributaries were moderate to high Regression analysis indicated significant relationships between annual nitrogen loading rates and average annual total nitrogen and chlorophyll a concentrations in the water column Similar analyses also indicated significant relationships between chlorophyll a and the magnitude of diel dissolved oxygen changes in the water column It is concluded that these simple models, which could be improved with a well-designed monitoring program, could be used as quantitative management tools to relate habitat conditions to nutrient loading rates

Seagrass depth range and water quality in southern Moreton Bay, Queensland, Australia

Abstract: Correlations between water quality parameters and seagrass depth penetration were developed for use as a biological indicator of integrated light availability and long-term trends in water quality. A year-long water quality monitoring programme in Moreton Bay was coupled with a series of seagrass depth transects. A strong gradient between the western (landward) and eastern (seaward) portions of Moreton Bay was observed in both water quality and seagrass depth range. Higher concentrations of chlorophyll a, total suspended solids, dissolved and total nutrients, and light attenuation coefficients in the water column and correspondingly shallower depth limits of the seagrass Zostera capricorni were observed in the western portions of the bay. Relatively high correlation coefficient values (r2 > 0.8) were observed between light attenuation coefficient, total suspended solids, chlorophyll a, total Kjeldahl nitrogen and Zostera capricorni depth range. Low correlation coefficient values (r2 < 0.8) between seagrass depth range and dissolved inorganic nutrients were observed. Seagrasses had disappeared over a five-year period near the mouth of the Logan River, a turbid river with increased land use in its watershed. At a site 9 km from the river mouth, a significant decrease in seagrass depth range corresponded to higher light attenuation, chlorophyll a, total suspended solids and total nitrogen content relative to a site 21 km from the river mouth. Seagrass depth penetration thus appears to be a sensitive bio-indicator of some water quality parameters, with application for water quality management.

Periphyton-Water Quality Relationships along a Nutrient Gradient in the Northern Florida Everglades

Abstract: We monitored a 14-km nutrient gradient in the northern Everglades to identify statistical relationships between periphyton and water-quality changes caused by canal discharges into the marsh. Water chemistry measurements were taken at 15 sampling stations every 2 wk over a 20-mo period to quantify changes in major ions along the gradient. Standard algal bioassays were conducted using water from each station to identify trends in nutrient limitation and algal growth potential along the gradient. Patterns of periphyton biomass accumulation and taxonomic composition on artificial substrata were determined in situ during 6 sampling events across seasons. Concentrations of most ions decreased by 8 km from inflows). Limiting nutrient assays showed a shift from P limitation at interior stations to possible limitation by other nutrients at peri...

An examination of short-term variations in water quality at a karst spring in Kentucky

Abstract: Water quality at many karst springs undergoes very high amplitude but relatively brief degradation following influxes of runoff. Accurately recording transient variations requires more rigorous sampling strategies than traditional methods. A pilot study to determine the usefulness of high-frequency, flow-dependent sampling strategies, combined with coincidental quantitative dye tracer tests, was implemented in the Big Spring Ground-Water Basin in Mammoth Cave National Park, Kentucky. Data recorded following two separate runoff events showed that the concentrations of two nonpoint source pollutants, fecal coliform bacteria and suspended sediment, greatly exceeded prerunoff event values for very short periods of time. A phreatic conduit segment, calculated at 17 million liters in volume, instantaneously propagated head changes, caused by direct runoff entering the aquifer, from the ground-water inputs to Big Spring. A significant delay between the initial increases in discharge and the arrival of direct runoff, as indicated by a steady decrease in specific conductance, represented the time required to displace this volume of phreatic water. The delay showed that sampling a karst spring only during peak discharge would be an unreliable sampling method. Runoff from two different subcatchments was tagged with tracer dye and the timing of the passage of the resultant dye clouds throughmore » Big Spring were compared to water quality variations. Distinct lag times between the arrival of direct runoff at Big Spring and the bacteria and suspended sediment waveforms were shown through the concurrent quantitative tracer tests to be related to the areal distribution of land-cover type within the basin.« less

The determination of total nitrogen and total phosphorus concentrations in freshwaters from land use, stock headage and population data: testing of a model for use in conservation and water quality management

Abstract: 1. Nutrient concentrations (particularly N and P) determine the extent to which water bodies are or may become eutrophic. Direct determination of nutrient content on a wide scale is labour intensive but the main sources of N and P are well known. This paper describes and tests an export coefficient model for prediction of total N and total P from: (i) land use, stock headage and human population; (ii) the export rates of N and P from these sources; and (iii) the river discharge. Such a model might be used to forecast the effects of changes in land use in the future and to hindcast past water quality to establish comparative or baseline states for the monitoring of change. 2. The model has been calibrated against observed data for 1988 and validated against sets of observed data for a sequence of earlier years in ten British catchments varying from uplands through rolling, fertile lowlands to the flat topography of East Anglia. 3. The model predicted total N and total P concentrations with high precision (> 95% of the variance in observed data explained). It has been used in two forms: the first on a specific catchment basis; the second for a larger natural region which contains the catchment with the assumption that all catchments within that region will be similar. Both models gave similar results with little loss of precision in the latter case. This implies that it will be possible to describe the overall pattern of nutrient export in the UK with only a fraction of the effort needed to carry out the calculations for each individual water body. 4. Comparison between land use, stock headage, population numbers and nutrient export for the ten catchments in the pre-war year of 1931, and for 1970 and 1988 show that there has been a substantial loss of rough grazing to fertilized temporary and permanent grasslands, an increase in the hectarage devoted to arable, consistent increases in the stocking of cattle and sheep and a marked movement of humans to these rural catchments. 5. All of these trends have increased the flows of nutrients with more than a doubling of both total N and total P loads during the period. On average in these rural catchments, stock wastes have been the greatest contributors to both N and P exports, with cultivation the next most important source of N and people of P. Ratios of N to P were high in 1931 and remain little changed so that, in these catchments, phosphorus continues to be the nutrient most likely to control algal crops in standing waters supplied by the rivers studied.

Arsenic contamination in surface drainage and groundwater in part of the southeast Asian tin belt, Nakhon Si Thammarat Province, southern Thailand

Abstract: The occurrence of human health problems resulting from arsenic contamination of domestic water supplies in Ron Phibun District, Nakhon Si Thammarat Province, southern Thailand was first recognized in 1987. The area has an extensive history of bedrock and alluvial mining, the waste from which is typically rich in arsenopyrite and related alteration products. In 1994 a collaborative study was instigated involving Thai and British government authorities to establish the distribution and geochemical form of As in surface drainage and aquifer systems in the affected area, the probable sources of As contamination, and the potential for problem alleviation. Hydrochemical analyses of surface- and groundwaters have confirmed the presence of dissolved As at concentrations exceeding WHO potable water guidelines by up to a factor of 500. Contamination of the shallow alluvial aquifer system is systematically more severe than the underlying carbonate-hosted aquifer. Deep boreholes may therefore provide the best available potable water source for the local population. The presence of up to 39% of total As as arsenite (H3AsO3) within the carbonate aquifer may, however, constitute a ‘hidden’ toxicological risk, not evident in the shallow groundwater (in which arsenate species account for > 95% of total As). Mineralogical investigations of As-rich tailings and flotation wastes were undertaken to evaluate their likely impact on water quality. The results indicate that although some flotation wastes contain up to 30% As, the rate of leaching is extremely low. Consequently the As loading of drainage emanating from such waste is below the subregional average. Analyses of the silty alluvium that covers much of the central sector of the study area have highlighted As concentrations of up to 5000 mg kg−1, probably carried by disseminated arsenopyrite. Following sulfide dissolution, the mobility of As in this material may be high (with resultant contamination of shallow groundwater) due to the low Fe content of the soil. On the basis of the data acquired, a range of pollution mitigation schemes are currently under investigation including Fe supplementation of alluvium and microbial degradation of disseminated arsenopyrite.

Trends in nutrients

Abstract: The roles of nitrogen (N) and phosphorus (P) as key nutrients determining the trophic status of water bodies are examined, and evidence reviewed for trends in concentrations of N and P species which occur in freshwaters, primarily in northern temperate environments. Data are reported for water bodies undergoing eutrophication and acidification, especially water bodies receiving increased nitrogen inputs through the atmospheric deposition of nitrogen oxides (NOx). Nutrient loading on groundwaters and surface freshwaters is assessed with respect to causes and rates of change, relative rates of change for N and P, and implications of change for the future management of lakes, rivers and groundwaters. In particular, the nature and emphasis of studies for N species and P fractions in lakes versus rivers and groundwaters are contrasted. This review paper primarily focuses on results from North America and Europe, particularly for the UK where a wide range of data sets exists. Few nutrient loading data have been published on water bodies in less developed countries; however, some of the available data are presented to provide a global perspective. In general, N and P concentrations have increased dramatically (>20 times background concentrations) in many areas and causes vary considerably, ranging from urbanization to changes in agricultural practices.

Global warming, river flows and water resources

Abstract: Global Warming, River Flows and Water Resources Climate Change and Hydrological Processes Assessing the Effects of Climate Change The Great Britain Case Study: Catchments, Models and Scenarios Changes in Water Resources in Britain Changes in River Flows over Time Changes in Water Quality Implications for Water Resources and Water Management

Contribution of nitrogen species and phosphorus fractions to stream water quality in agricultural catchments

Abstract: The contribution from agricultural catchments to stream nitrogen and phosphorus concentrations was assessed by evaluation of the chemical composition of these nutrients in agricultural runoff for both surface and subsurface flow pathways. A range of land uses (grazed and ungrazed grassland, cereals, roots) in intensive agricultural systems was studied at scales from hillslope plots (0.5 m2) to large catchment (>300 km2). By fractionating the total nutrient load it was possible to establish that most of the phosphorus was transported in the unreactive (particulate and organic) fraction via surface runoff. This was true regardless of the scale of measurement. The form of the nitrogen load varied with land use and grazing intensity. High loads of dissolved inorganic nitrogen (with >90% transported as NH4-N) were recorded in surface runoff from heavily grazed land. In subsurface flow from small (2 km2) subcatchments and in larger (>300 km2) catchments, organic nitrogen was found to be an important secondary constituent of the total nitrogen load, comprising 40% of the total annual load.

Occurrence and accumulation of pesticides and organic contaminants in river sediment, water and clam tissues from the san Joaquin River and tributaries, California

Abstract: A study was conducted in 1992 to assess the effects of anthropogenic activities and land use on the water quality of the San Joaquin River and its major tributaries. This study focused on pesticides and organic contaminants, looking at distributions of contaminants in water, bed and suspended sediment, and the bivalve Corbicula fluminea. Results indicated that this river system is affected by agricultural practices and urban runoff. Sediments from Dry Creek contained elevated concentrations of polycyclic aromatic hydrocarbons (PAHs), possibly derived from urban runoff from the city of Modesto; suspended sediments contained elevated amounts of chlordane. Trace levels of triazine herbicides atrazine and simazine were present in water at most sites. Sediments, water, and bivalves from Orestimba Creek, a westside tributary draining agricultural areas, contained the greatest levels of DDT (1,1,1-trichloro-2,2-bis[p-chlorophenyl]ethane), and its degradates DDD (1,1-dichloro-2,2-bis[p-chlorophenyl]ethane), and DDE (1,1-dichloro-2,2-bis[p-chlorophenyl]ethylene). Sediment adsorption coefficients (Koc), and bioconcentration factors (BCF) in Corbicula of DDT, DDD, and DDE at Orestimba Creek were greater than predicted values. Streams of the western San Joaquin Valley can potentially transport significant amounts of chlorinated pesticides to the San Joaquin River, the delta, and San Francisco Bay. Organochlorine compounds accumulate in bivalves and sediment and may pose a problem to other biotic species in this watershed.

US outbreaks of cryptosporidiosis

Abstract: Drinking water has been implicated as the mode of transmission in several outbreaks of cryptosporidiosis throughout the United States. This review of US outbreaks describes characteristics of the raw water supply, suspected sources of contamination, water treatment methods, and corrective actions. Of the total number of outbreaks, roughly half were associated with groundwater sources; the majority of affected individuals, however, were served by drinking water drawn from surface water. Wastewater was implicated as the source of contamination of raw or treated water for roughly half of the outbreaks. Nonpoint sources, such as agricultural runoff, were suspected sources of contamination in the remaining outbreaks. The majority of affected individuals were served by treatment plants using coagulant addition, filtration, and chlorine disinfection processes. Although treatment deficiencies and suboptimal operational practices were noted during some of the outbreaks, all treatment plants were complying with federal and local regulations. Existing regulations and water supply systems, especially those utilizing surface water sources, should be reevaluated.

Sediment retention in a bottomland hardwood wetland in Eastern Arkansas

Abstract: One of the often-stated functions of wetlands is their ability to remove sediments and other particulates from water, thus improving water quality in the adjacent aquatic system. However, actual rates of suspended sediment removal have rarely been measured in freshwater wetland systems. To address this issue, suspended sediment dynamics were measured in a 85-km2 bottomland hardwood (BLH) wetland adjacent to the highly turbid Cache River in eastern Arkansas during the 1988–1990 water years. A suspended sediment mass balance was calculated using depth-integrated, flow-weighted daily measurements at wetland inflow and outflow points. Over the three-year period, suspended sediment load decreased an average of 14% between upstream and downstream sampling points. To test the idea that the suspended sediments were retained by the adjacent wetland and to determine what portion of the BLH forest was most responsible for retaining the suspended sediments, concurrent measurements of sediment accretion were made at 30 sites in the wetland using feldspar clay marker horizons, sedimentation disks, the137cesium method, and dendrogeomorphic techniques. Sedimentation rates exceeding 1 cm/yr were measured in frequently flooded areas dominated byNyssa aquatica andTaxodium distichum. Maximum sedimentation rates did not occur on the natural levee, as would be predicted by classical fluvial geomorphology, but in the “first bottom,” where retention time of the water reached a maximum. Multiple regression was used to relate sedimentation rates with several physical and biological factors. A combination of distance from the river, flood duration, and tree basal area accounted for nearly 90% of the variation in sedimentation rates.

Variation in Microbial Biomass and Activity in Four Different Wetland Types

Abstract: Functional evaluation of wetlands in nutrient cycling, water quality maintenance, and wetland construction and restoration contexts requires knowledge of differences in microbial processes between different wetland types and understanding of the nature and extent of variation in these processes within a given wetland type. In this study, we measured a suite of microbial variables (microbial biomass C and N content, denitrification enzyme activity, potential net N mineralization and nitrification, and soil respiration) that are indices of wetland nutrient cycling and water quality maintenance functions in four different wetland types (calcareous fens, red maple swamps, woodland pools, and wet clay meadows) in eastern New York state. Total soil C and N content, water content, pH, water-table levels, and groundwater NH 4 + , NO 3 - and electrical conductivity were also measured. The clay meadow wetlands were drier and had lower levels of organic matter and most microbial variables than the other wetland types. Site-to-site variation within the fens was very high and was not strongly controlled by water-table levels. Organic matter content and N status appear to be strong regulators of microbial biomass and activity in fens. Red maple swamps and woodland pools had similar levels of most microbial variables. Variation within these wetland types was controlled by hydrology and organic matter quality. The suite of microbial variables that we measured identified potential functional differences between wetland types and should be useful for comparisons of the water quality maintenance value of different wetlands and for functional evaluation of altered or restored sites.

Evaluating plant performance with endospores

Abstract: Spores of aerobic spore-forming bacteria were used as microbial surrogates for evaluating drinking water treatment plant performance. A method for assaying for the microbial surrogate was developed. Various water sources were surveyed, and data were collected from coagulation and chlorine inactivation studies. Evaluations for spore removals and turbidity and particle removals were compared for pilot-scale and full-scale water treatment plants.

Narrow-mouthed water storage vessels and in situ chlorination in a Bolivian community : A simple method to improve drinking water quality

Abstract: Epidemiologic investigations of the Latin America cholera epidemic have repeatedly implicated untreated drinking water and water touched by hands during storage as important vehicles for disease transmission To prevent such transmission, we provided a new narrow-mouthed, plastic, water storage vessel and 5% calcium hypochlorite solution for home disinfection of stored water to a Bolivian Aymara Indian community at risk for cholera We evaluated acceptance of this intervention and its effect on water quality Each of 42 families in the study obtained water from a household well; fecal coliform bacteria were found in water from 39 (93%) of 42 wells and 33 (79%) of 42 usual water storage vessels One group of families received the special vessels and chlorine (group A), a second received only the special vessels (group B), and a third served as a control group (group C) Water samples collected every three weeks from group A special vessels had lower geometric mean fecal coliform colony counts (P < 00001) and lower geometric mean Escherichia coli colony counts (P < 00001) than water from group B or C vessels Adequate levels of free chlorine persisted in these vessels for at least 5 hr The special vessels and chlorine solution were well accepted and continued to be used for at least six months Use of the vessel and chlorine solution produced drinking water from nonpotable sources that met World Health Organization standards for microbiologic quality

Changes in plant communities relative to hydrologic conditions in the Florida Everglades

Abstract: Distribution and percent cover of plant species in relation to hydroperiod (i.e., depth and duration of flooding) were examined along eight vegetation transects in Water Conservation Area 3A of the Everglades where water-level recorders were either present or subsequently installed. Transects were monitored between 1978 and 1984 to detect changes in plant communities resulting from the operation of water-control structures to improve distribution of water to WCA 3A. Hydroperiod increased significantly at four transects where long-term hydrologic data were available. Distribution of some obligate wetland species such asSagittaria lancifolia increased significantly with longer flooding duration. Several taxa, includingNymphaea odorata andUtricularia spp., showed significant positive relationships with annual increases in water depth.Typha domingensis increased in frequency and cover at two transects close to the northernmost water-control structure despite showing no significant relationship with increased hydroperiod. Therefore, it seems that some other environmental factor, such as inputs of phosphorus enriched water through the structure, may be encouraging the encroachment of this species. Improved hydroperiod may be inadequate for Everglades restoration without water quality improvements since it will likely result in monotypic stands ofT. domingensis.