Municipal Point Sources Research Articles

Eutrophication: Early warning signals, ecosystem-level and societal responses, and ways forward

Eutrophication, i.e. nutrient over-enrichment, has been a topic for academic and societal debate for the past five decades both on land and in aquatic systems fed by nutrients as diffuse loading from agricultural lands and as wastewater from industrial and municipal point-sources. The use of nutrients (primarily nitrogen and phosphorus) in excess became a problem with the onset of large-scale production and use of artificial fertilizers after World War II, and the effects on the aquatic environment became obvious some two to three decades later. In this Perspective, four seminal papers on eutrophication are discussed in light of the current knowledge of the problem, including future perspectives and outlooks in the light of global climate change and the demand for science-based holistic ecosystem-level policies and management options.

Downstream Effects of Upstream Causes

The United States Environmental Protection Agency considers nutrient pollution in stream ecosystems one of the United States’ most pressing environmental challenges. But limited independent replicates, lack of experimental randomization, and space- and time-varying confounding handicap causal inference on effects of nutrient pollution. In this article, the causal g-methods are extended to allow for exposures to vary in time and space in order to assess the effects of nutrient pollution on chlorophyll a—a proxy for algal production. Publicly available data from North Carolina’s Cape Fear River and a simulation study are used to show how causal effects of upstream nutrient concentrations on downstream chlorophyll a levels may be estimated from typical water quality monitoring data. Estimates obtained from the parametric g-formula, a marginal structural model, and a structural nested model indicate that chlorophyll a concentrations at Lock and Dam 1 were influenced by nitrate concentrations measured 86 to 109 km upstream, an area where four major industrial and municipal point sources discharge wastewater. Supplementary materials for this article, including a standardized description of the materials available for reproducing the work, are available as an online supplement.

Innovation in Outcomes-Based Water Quality Policy: A Case Study from the Yahara Watershed, Wisconsin, USA

This case examines the risks and opportunities for stakeholders involved in an experimental water quality management program in Wisconsin, USA. This program pays for pounds of pollution reduced through soil conservation practices on farm fields and other high-runoff areas across the landscape—nonpoint sources of pollution—by redirecting funds from the sewerage plant and municipal point sources of pollution. Uncertain monitoring and modeling of pollution sources used for program payments and accountability create perceived and real risks to program participants and the environment, including the threat of regulatory enforcement, lost revenue, and failure to achieve environmental outcomes. On the other hand, in this case study, regulatory flexibility also opened a space for stakeholder dialog and programmatic cooperation that could lead to more adaptive and locally acceptable watershed pollution control in the future.

Bioavailability of mercury in power plant wastewater and ambient river samples: Evidence that the regulation of total mercury is not appropriate.

Mercury (Hg) is a neurotoxin that can cause debilitating effects to human and environmental receptors under high exposure conditions. For industrial and municipal point sources that discharge Hg, wastewater limitations on total Hg (THg) concentrations or loads are typical. While this regulatory practice provides simplicity for regulated industry and water resource agencies (i.e., for analytical detection and reporting purposes), it ignores the important considerations of speciation and bioavailability. In this study, water samples were collected from multiple power plant wastewater, simulated mixing zone, and ambient river locations (N = 10 to 20) and were analyzed for bioavailable Hg forms (methylmercury and acid-labile Hg, or BHg), THg, and dissolved Hg. The median concentration of THg in wastewater, mixing zone, and ambient river samples was 7.1, 5.3, and 2.3 ng/L, respectively. The percentages of THg as BHg (median values) were 18.7%, 29.3%, and 8.5% for wastewater, mixing zone, and ambient river samples. The percentages of methylmercury (MeHg) as THg were not statistically different between paired ambient and mixing zone samples (P > 0.05); this result indicates that wastewater did not increase the MeHg fraction when mixed with ambient water. Multiple regression analysis indicated that variation in THg for combined wastewater and mixing zone samples could be adequately explained by pooled water quality parameters (total suspended solids, total dissolved solids, sulfate, total organic carbon, pH, specific conductivity; r2 = 0.51; P < 0.05); however, no significant regression relationships were apparent for the percentage of BHg. These results, at least for the wastewater samples evaluated, indicate that regulating THg is likely overly conservative, and mechanisms to regulate the bioavailable forms of Hg are needed. If Hg fish tissue monitoring data indicate that concentrations are less than consumption thresholds, metal translator methodologies or bioavailability-based criterion techniques (as currently used for non-Hg trace elements) should be allowed for Hg. Integr Environ Assess Manag 2019;15:142-147. © 2018 SETAC.

A tool for assisting municipalities in developing riparian shade inventories

Streams in many urbanized watersheds have elevated water temperature, and stream temperature is a regulated aspect of water quality in many parts of the western U.S. Some municipal point source polluters develop temperature mitigation plans that involve compensatory measures linked to stream temperature, principally increasing riparian shade. In this paper we describe a tool designed to help municipalities and other riparian property managers develop inventories of current and potential stream shade. The tool is based on the insolation module of the published model Heat Source to which we made the following modifications: (1) developed user interfaces and regional supporting geospatial data that minimize data acquisition and user expertise requirements; (2) incorporated LiDAR data to produce direct high spatial resolution estimates of riparian vegetation architecture; (3) created a new method to estimate site specific potential vegetation, with concomitant changes in the shading algorithm involving finer discretization and fewer parameter requirements. The new tool produces estimates of existing shade conditions comparable to those derived from on the ground field measurements for small to medium sized streams. We used the tool to develop a riparian shade inventory and a map of potential shade restoration for the City of Albany, Oregon, U.S.A. Results of this case study demonstrate that the tool can help municipalities meet shade reporting and monitoring goals at a minimum cost, including identifying specific areas with highest potential gains in shade. However, the case study identified limitations in some regional GIS framework data that potentially limit broad applicability or increase costs.

Site-Specific Simulation of Nutrient Control Policies: Integrating Economic and Water Quality Effects

A watershed-based modeling system is developed to assess alternative nutrient abatement policies, including fertilizer taxes, application caps, and uniform reductions. A microeconometric model of nutrient use is estimated using farm-level data, prices, and spatially detailed soil and land characteristics. Results are interfaced with a physical watershed model to predict water quality changes. Simulations demonstrate differences in water quality effects across policies. For nitrate loads at the watershed outlet, an application cap provides slightly superior performance for small reductions, but a tax is more efficient under larger reductions. Phosphorus reductions at the sub- watershed level vary but provide information about policy tradeoffs. Worsening surface water quality is an important and multifaceted issue encompassing problems such as hypoxic zones, fish kills, drinking water concerns, and diminished recreational opportunities. While regulating industrial and municipal point sources of water pollution has become common, non-point or diffuse sources, including agricultural sources, remain relatively uncontrolled. Agriculture's primary non-point source contribution to water quality problems is the use of fertilizers in the crop production process. Of the common fertilizer components, nitrogen and phosphorus are major nonpoint causes of impaired waters throughout most of the United States (U.S. Geological Survey, 1999). Public policy has yet to effectively address many of the concerns related to nonpoint source pollution and government bodies struggle to find the means to achieve changes in related pollution. Many of the difficulties associated with policy implementation arise from the need for solutions tailored to a specific watershed. This aspect of the problem is most acute in areas where a large proportion of water body impairment is due to nonpoint sources of pollution; each area has a unique distribution of nonpoint source pollutants that degrade water quality. The goal of this study is to develop a framework for assessing policies designed to improve water quality in a given watershed; here, the Raccoon River watershed in Iowa. This watershed experiences some of the highest nitrate concentrations in the country and contains a number of nutrient-impaired lakes and waterways. Policy assessment requires examination of tradeoffs between water quality improvement and impact on net returns for farm operators. Policies examined here include a tax on each nutrient, a per-acre application cap, and a uniform reduction in application levels, following common policy options discussed by Griffin and Bromley (1982), Helfand and House (1995), and Shortle and Horan (2001). The analysis is conducted via the development and application of two complementary modeling frameworks. The first is a production model used to determine fertilizer input choice and farm net-return response to policy implementation. The second is a physical model, the Soil and Water Assessment Tool (SWAT), which predicts watershed-wide effects of changing

Fecal coliform modeling under two flow scenarios in St. Louis Bay of Mississippi

St. Louis Bay, along with its two major tributaries, Wolf River and Jourdan River, are included in the Mississippi 1998 Section 303(d) List for violation of the designated water use of recreation and shellfish harvesting. Fecal coliform was identified as one of the pollutants that caused the water quality impairment. In order to facilitate the total maximum daily loads (TMDL) development, the fecal coliform dynamics was investigated under 2 flow scenarios with a calibrated and validated modeling framework by integration of Environmental Fluid Dynamic Code (EFDC) and Hydrological Simulation Program Fortran (HSPF). EFDC was used to model the hydrodymics and fecal coliform transportation in the Bay and the tributaries, whereas HSPF was applied to compute the flow and fecal coliform loadings from the watersheds. The total amount of precipitation in the dry year simulation corresponds to a 50-year return period of low flow condition, and a 10-year return period of high flow condition for wet weather simulation. For EFDC modeling, the fecal coliform sources considered were the contributions from the 2 upper watersheds (no tidal influence), the 28 small surrounding watershed, and 12 municipal, industrial, and domestic point sources. When simulating the fecal coliform loadings from the 2 upper watersheds using HSPF, the simulated non-point source loadings of fecal coliform included wildlife, land application of hog and cattle manure, land application of poultry litter, and grazing animals. The EFDC modeling results indicated that the wet weather exerted greater stress on fecal coliform water quality conditions. The number of exceedance of fecal coliform water quality standard in wet year simulation is much higher than that in dry year simulation. The impact of the upper rural watersheds loads on fecal coliform levels in the St. Louis Bay is much less significant than that from the surrounding urban runoff. Fecal coliform TMDL development should be based on high flow conditions since the decision makers are more concerned about worse scenarios. This fecal coliform modeling research would provide useful information of critical condition selection for TMDLs development in similar coastal areas.

Spatial patterns of submerged macrophytes and heavy metals in the hypertrophic, contaminated, shallow reservoir Lake Qattieneh/Syria

Our investigation on macrophytes in Lake Qattieneh, a large, shallow reservoir in western Syria, is a first assessment of ecological status of this lake. We studied spatial distribution patterns of aquatic macrophyte vegetation and heavy metal concentrations to determine if they can be used as indicators of point sources of pollution. Industrial and municipal point sources at the lake shore increase nutrient load and contamination by heavy metals. Water analyses revealed high concentrations of some heavy metals at some littoral sites: Ni 88.7 μg L −1, Cr 49.99 μg L −1, Co 14.38 μg L −1, and Cu 11.65 μg L −1. Despite hypertrophic conditions and high heavy metal contamination, we recorded several submerged macrophyte species with heterogeneous spatial distribution patterns. Whereas Potamogeton pectinatus L. dominates in the eastern part of the lake, near industrial point sources, both Myriophyllum spicatum L. and Potamogeton lucens L. form extended patches in the western part of the lake. The shallow, littoral areas near villages are dominated by Ranunculus trichophyllus Chaix in Villars and Ceratophyllum demersum L. The west–east gradient in nutrient and heavy metal concentrations in waters and sediments are reflected by the spatial distribution of submersed species. While the heavy metal concentrations of the water body vary considerably in different seasons, the contents in submersed macrophytes integrate seasonal variations of longer time periods. Spatial distribution and tissue accumulation of littoral macrophyte species reflect the environmental conditions at respective sites such as heavy metal contents in water and sediment.

HISTORICAL EUTROPHICATION IN A RIVER–ESTUARY COMPLEX IN MID-COAST MAINE

European settlement of New England brought about a novel disturbance regime that impacted rivers and estuaries through overfishing, deforestation, dams, and water pollution. The negative consequences of these activities intensified with industrialization in the 19th and 20th centuries, often resulting in ecosystem degradation. Since environmental legislation was implemented in the 1970s, improvement in water quality has been tangible and widespread; however, ecological recovery can require substantial amounts of time and may never be complete. To document the natural baseline conditions and investigate the recovery of a severely degraded river-estuary complex in mid-coast Maine, we examined diatoms, pollen, total organic carbon, total nitrogen, stable isotopes, total phosphorus, biogenic silica, and trace metals in intertidal sediments and established a chronology with 14C, 210Pb, and indicator pollen horizons. Both climate variability and human effects were evident in the sedimentary record of Merrymeeting Bay, the freshwater tidal portion of the Kennebec estuary. Natural climate variability was apparent in an episode of high sedimentation and altered diatom abundance during the 12th and 13th centuries and in changing pollen abundances between the 16th and 19th centuries, indicative of regional cooling. During the 18th century, colonial land clearance began an era of high sedimentation and eutrophication that strongly intensified with industrialization during the late 19th and 20th centuries. Improvements in water quality over the past 30 years in response to environmental regulation had little effect on ecosystem recovery as represented by the sedimentary record. Diatom composition and productivity and high fluxes of organic C, total P, and biogenic Si in recent sediments indicate that rates of nutrient loading remain high. These environmental proxies imply that aquatic productivity in Merrymeeting Bay was originally nutrient limited and water clarity high, relative to today. Further recovery may require more stringent regulation of nutrient inputs from industrial and municipal point sources. This historical study can contribute to public debate about the environmental management of this unusual river-estuary complex by describing its long-term natural baseline, thereby illustrating the upper limit of its potential for recovery.

Characterising phosphorus transfers in rural catchments using a continuous bank-side analyser

Abstract. A six-month series of high-resolution synchronous stream discharge and total phosphorus (TP) concentration data is presented from a 5 km2 agricultural catchment in the Lough Neagh basin, Northern Ireland. The data are hourly averages of 10-minute measurements using a new bankside, automatic, continuous monitoring technology. Three TP transfer "event-types" occur in this catchment: (1) chronic, storm independent transfers; (2) acute, storm dependent transfers; (3) acute, storm independent transfers. Event-type 2 transferred over 90% of the total 279 kg TP load in 39% of the total period; it corresponded to diffuse transfers from agricultural soils. Event-types 1 and 3, however, maintained the river in a highly eutrophic state between storm events and were characteristic of point source pollution, despite there being no major industrial or municipal point sources. Managing P transfers at the catchment scale requires a robust monitoring technology to differentiate between dynamic, multiple sources and associated event types and so enable a reliable assessment of the performance of mitigation measures, monitored at catchment outlets. The synchronous and continuous TP and discharge data series generated in this study demonstrate how this is possible.

Estimations of municipal point source pollution in the context of river basin management

Integrated presentation of total emissions on catchment scale is prerequisite for many tasks in integrated management of point and diffuse sources of pollution. This paper will focus on emissions of nutrients from municipal point sources. Based on calculations of discharges of N, P from households into wastewater and on the detailed evaluation of data from 76 municipal wastewater treatments plants, this paper presents ranges of specific loads of inhabitants and population equivalents in the raw wastewater. In addition data of these treatment plants have been evaluated in respect of the treatment efficiency for nitrogen and phosphorus (average reduction rates) dependent on the design characteristic (with or without nitrification, denitrification or enhanced phosphorus removal). The results of the investigation show that the specific N and P loads from households in Austria lie within the range 1.6-2.0 g P/(inhabitant.d) and 11- 13 g N/(inhabitant.d). The specific contribution of industries to municipal wastewater varies between 0.3 and 2.0 gP/(pe.d) and 0 and 13 g N/(pe.d) with average values of 1.3 g P/(pe.d) and 6.5 g N/(population equivalent (pe)/d). As average values for municipal wastewater (contributions from household and industry) this leads to specific influent loads of 1.5 g P/(pe.d) and 8.8 g N/(pe.d). Average treatment efficiencies of treatment plants are for instance 50% nitrogen removal in treatment plants with nitrification and 80% in treatment plants with nitrification/denitrification. For phosphorus a removal of about 85% can be expected where the treatment plant was designed for enhanced phosphorus removal. Finally a method for load estimations based on standard values as mentioned above was tested for the estimation of emission from municipal point sources of selected regions.

Organochlorine and Metal Contaminant Exposure and Effects in Hatching Black-Crowned Night Herons ( Nycticorax nycticorax ) in Delaware Bay

Pea Patch Island in Delaware Bay is the site of the largest heronry north of Florida. From 1989-93, the population of nine species of wading birds numbered approximately 12,000 pairs, but has recently declined to about 7,000 pairs. Because Delaware Bay is a major shipping channel and receives anthropogenic releases of toxic substances from agricultural, industrial, and municipal point and nonpoint sources, contaminant exposure and effects to the heronry have been an ongoing concern. In 1997, pipping (early hatching stage) black-crowned night herons (Nycticorax nycticorax) were collected from separate nests at Pea Patch Island and from a coastal reference site, Middle Island in Rehoboth Bay, Delaware. There was no evidence of malformations or hepatic histopathological lesions in embryos, and their body and liver weights did not differ between sites. Biomarkers of petroleum hydrocarbons, polyhalogenated contaminant, and metal exposure (cytochrome P450 induction and oxidative stress responses) did not differ (p > 0.05) between sites, although activities of benzyloxy-O-dealkylase and ethoxyresorufin-O-dealkylase were somewhat elevated in 3 of the 15 embryos collected from Pea Patch Island. Concentrations of 21 organochlorine pesticides and metabolites were relatively low at both sites, with p,p'-DDE values well below the threshold associated with eggshell thinning. Although total PCB concentration was modestly elevated (p < 0.05) in Pea Patch Island heron embryos, levels of arylhydrocarbon receptor-active PCB congeners, polychlorinated dibenzodioxins and dibenzofurans, and toxic equivalents were low and did not differ between sites. Concentrations of Cd and Mn in pipping embryos from Pea Patch Island were slightly greater (p < 0.05) than values observed in Middle Island embryos, but levels of these and the other metals and metalloids (e.g., Hg and Se) were below values associated with toxicity. In conclusion, it seems unlikely that chlorinated hydrocarbon and metal contaminant exposure constitutes a direct threat to the reproductive success of black-crowned night herons at Pea Patch Island. However, low-level exposure to these contaminants may constitute one of many stressors that in combination could adversely affect the stability of the wading bird population at this large heronry.

History of Mercury Loading in the Upper Mississippi River Reconstructed from the Sediments of Lake Pepin

An array of sediment cores was analyzed to determine historical trends in mercury (Hg) accumulation in Lake Pepin, a natural lake on the Upper Mississippi River. Whole-basin Hg accumulation rates increased from 3 kg/yr before European settlement (ca. 1830) to a maximum of 357 kg/yr in the 1960s. The recent Hg accumulation rate (110 kg/yr, 1990−1996) is experimentally indistinguishable from measured Hg loadings in the river entering the lake, indicating that accumulation rates in Lake Pepin correspond quantitatively to river loadings. The modern accumulation rate represents a decline of almost 70% from the peak value, reflecting large decreases in Hg inputs to the Mississippi River from industrial and municipal point sources in the metropolitan Minneapolis/St.Paul area upstream. A total of 18.1 t of Hg has been deposited in Lake Pepin since 1800; half of that (9.0 t) was deposited between 1940 and 1970, when regional growth accelerated rapidly but pollution control mechanisms were inadequate. Point sources accounted for approximately 60% of the Hg accumulating in Lake Pepin in the 1960s, but these inputs have been virtually eliminated since then.

Wet weather control demonstration activities in southeast Michigan: some lessons learned

Wayne County's Rouge River National Wet Weather Demonstration Project (Rouge Project) is a comprehensive program to restore the water quality of the Rouge River, a tributary to the Detroit River in southeast Michigan. The Rouge River Watershed is largely urbanized with over 1.5 million people in 48 communities and 3 countries. Sources of pollution to the river include industrial and municipal point sources, storm water runoff, combined sewer overflows (CSOs) and other minor sources. While the Rouge Project first focused on controlling the 150 CSO discharges the focus shifted to other sources of pollution, such as storm water in order to restore the river. This paper describes the lessons learned in building institutional and regulatory frameworks necessary to accommodate a watershed approach to wet weather pollution management. Also described are the consensus building strategies which were used to engage numerous stakeholders, provide them opportunities to influence decisions, and participate in the Rouge River restoration. The Rouge Project is demonstrating that a watershed-based pollution management program is achieving faster and more cost-effective restoration and protection of water resources.

Wet weather control demonstration activities in Southeast Michigan: Some lessons learned

Wayne County's Rouge River National Wet Weather Demonstration Project (Rouge Project) is a comprehensive program to restore the water quality of the Rouge River, a tributary to the Detroit River in southeast Michigan. The Rouge River Watershed is largely urbanized with over 1.5 million people in 48 communities and 3 counties. Sources of pollution to the river include industrial and municipal point sources, storm water runoff, combined sewer overflows (CSOs) and other minor sources.While the Rouge Project first focused on controlling the 150 CSO discharges the focus shifted to other sources of pollution, such as storm water in order to restore the river. This paper describes the lessons learned in building institutional and regulatory frameworks necessary to accommodate a watershed approach to wet weather pollution management. Also described are the consensus building strategies which were used to engage numerous stakeholders, provide them opportunities to influence decisions, and participate in the Rouge River restoration.The Rouge Project is demonstrating that a watershed-based pollution management program is achieving faster and more cost-effective restoration and protection of water resources.

Acute and chronic toxicity of industrial and municipal effluents in Maryland, U.S.

Since 1987, an effluent biomonitoring program of major and selected minor industrial and municipal point source dischargers has been conducted for Maryland's Department of the Environment. Acute and chronic toxicity test procedures were developed and implemented for testing freshwater (Pimephales promelas, Daphnia magna, and Ceriodaphnia dubia) and estuarine (Cyprinodon variegatus and Mysidopsis bahia) invertebrates and fish. Results from the laboratory bioassays were used by Maryland to identify toxic discharges to state waters. Beginning in 1987, totals of 488 and 89 effluent samples were tested for acute and chronic toxicity, respectively. Both the frequency of acute and chronic toxicity and the severity of the toxicity of the remaining toxic effluents have decreased dramatically since the inception of the program. Examples are presented concerning the use of these data by Maryland to regulate toxic discharges. These results indicate the important role whole‐effluent toxicity testing plays in controlling the point source discharge of toxic substances to surface waters.

NUTRIENTS IN STREAMS DURING BASEFLOW IN SELECTED ENVIRONMENTAL SEVFINGS OF THE POTOMAC RiVER BASIN1

ABSTRACT: A regional assessment of water quality in small streams was conducted within four areas of distinct physiography and lithology in the upper Potomac River Basin. The Potomac River is a major tributary to the Chesapeake Bay, and this study provides new insight on the relationships between nutrient concentrations in small streams and watershed characteristics within this river basin. Nutrient concentrations were compared to land‐use data including categories for agriculture (cropland and pasture), urban areas, and forests. Among agricultural areas, streams draining areas of intense row cropping typically contained higher nitrate concentrations than did those draining pastures. Streams draining forested areas typically had the lowest nutrient concentrations. Streams in areas underlain by carbonate bedrock were more likely to contain elevated concentrations of inorganic nitrogen and potassium than did streams in areas underlain by fractured siliciclastic or crystalline rocks, and we suggest that this is a physical phenomenon related to high hydraulic conductivities in carbonate ground‐water systems. The median nitrate concentrations were highest in the Great Valley portion of the Valley and Ridge physiographic province, particularly in watersheds that have both carbonate bedrock and intensive row cropping. Values of nitrate in these streams ranged up to 8.99 mg/L as nitrogen. The soluble phosphorus concentrations during baseflow were generally low in all sub‐units, even in some settings with potential for high phosphorus inputs such as urban areas with municipal point sources or agricultural areas. The mobility of phosphorus in these environments may be hindered by adsorption and geochemical reactions.

Impact of Point and Nonpoint Source Pollution on Pore Waters of Two Chesapeake Bay Tributaries

Chesapeake Bay and its tributaries are contaminated by industrial and municipal point sources and agricultural nonpoint sources of pollution. The objective of this study was to compare the porewater characteristics of two Chesapeake Bay tributaries: Wicomico River (WR) contaminated by point source and Pocomoke River (PR) contaminated by both point and nonpoint sources of pollution. Four study sites (1 mile before, adjacent to, and 1 and 2 miles after the sewage treatment plant) were chosen to collect sediment samples in both the rivers. The sediment–pore waters were analyzed for toxicity using Microtox marine luminescent bacteria—Vibrio fischeri.USEPA toxicity identification evaluation tests on these pore waters confirmed that the contaminants (ammonia and heavy metals) in WR were from municipal point sources, whereas in PR the contamination (metals, pesticides, and PCBs) was from nonpoint sources (agriculture) of pollution. The toxicity (and the concentration of contaminants) decreased both upstream and downstream from the most polluted site in both the rivers.

Development of a Mass Balance Model of the Fate of 17 Chemicals in the Bay of Quinte

A multi-segment water quality model based on the QWASI (Quantitative Water Air Sediment Interaction) fugacity/aquivalence approach is developed for the Bay of Quinte. The model of the bay consists of seven water column compartments, five sediment compartments, the atmosphere, and two compartments in Lake Ontario. Chemicals enter the bay from tributaries and runoff, industrial and municipal point sources, the atmosphere, and Lake Ontario. Over 50 rate expressions are used to describe the transport and transformation of chemicals through and between segments under steady-state conditions. A food chain model applicable to organic chemicals and consisting of six trophic levels is also described. The bay model was calibrated with concentration data for arsenic and pentachlorophenol and tested with copper and zinc data sets. Since varying amounts of information were available for the remaining chemicals, the bay and food chain models were used to “back-calculate” the loadings of 10 chemicals based on known in-bay water, sediment, or fish concentrations. For all chemicals (four inorganics and 13 organics), the model gives order-of-magnitude estimates of loadings, concentrations in water, sediment and biota, amounts, rates of movement, and estimates of persistence from which appropriate remedial measures are discussed.

Modified Low Flow Frequency Analysis Applied to a Wastewater Allocation Study

The South Nation River was studied for its ability to assimilate wastewater effluents from municipal and industrial point sources for both existing and anticip…