Effluent Plume Research Articles

Characteristics and sedimentation of initial effluent discharged from excavated levee ponds for channel catfish

Most channel catfish are produced in excavated levee ponds that are constructed with fixed drains extending from the deepest part of the pond through the levee. When these ponds are drained, sediment accumulated in and around the drainpipe inlet is discharged with the first flush of water, resulting in a high initial solids concentration in the effluent. This study was conducted to evaluate (1) the quality and settling characteristics of initial pond effluent from excavated ponds with fixed internal drains and (2) the spatial and temporal changes in water quality as the first flush of catfish pond effluent flowed through a 1-m wide vegetated drainage ditch. Chemical and settling characteristics of effluent samples collected at the discharge point during the first 20min of discharge were determined. The initial discharge was very high in total suspended solids, volatile suspended solids, total nitrogen, and total phosphorus. The initial solids concentration was 900 times higher than that of the bulk pond water. After 15min, poorly consolidated sediment from around the drain inlet had been discharged, and effluent quality was identical to the bulk pond water. The median-settling velocity of solids decreased from 0.7cm/s at the start of pond draining to 0.03cm/s after 15min. After initial effluent plumes had flowed 150–200m downstream, nearly all solids, nitrogen, and phosphorus in the initial effluent were removed and concentrations of those substances were lower than in bulk pond water. The duration of poor water quality of initial effluent from catfish ponds with internal drains was brief (ca. 10min) and discharged solids settled rapidly after flowing through 150–200m of vegetated ditch extending from pond effluent outfalls.

Use of Fecal Steroids To Infer the Sources of Fecal Indicator Bacteria in the Lower Santa Ana River Watershed, California: Sewage Is Unlikely a Significant Source

The Santa Ana River (SAR), CA and adjacent wetlands have been identified as potential sources of fecal indicator bacteria (FIB) to the surf zone at Huntington Beach, CA. A suite of fecal steroids, including coprostanol (COP), epicoprostanol (eCOP), cholesterol (CHOE), cholestanol (CHOA), alpha-cholestanone (aONE), beta-cholestanone (bONE), beta-sitosterol (bSIT), stigmasterol (STIG), stigmastanol (STAN), and campesterol (CAM), were used as chemical markers to examine whether sewage was a significant source of FIB within the lower Santa Ana River watershed. A total of 54 water samples were collected from three locations in the intertidal zone near the mouth of the Santa Ana River at different tidal stages. Steroid ratios in SAR samples were different from those found in raw and treated sewage from a local wastewater treatment plant or in nearby effluent plume and did not appear to be influenced by the sampling location, daily tides, and spring/neap tidal cycle. The characteristics of steroid ratios suggested a diagenetic ratherthan a biogenic source forthe COP content of the samples. The log-based concentrations of COP and FIB in the SAR samples were not significantly correlated, inconsistent with sewage being the source of FIB in the study area. In addition, multivariate statistical analysis showed that the concentrations of FIB were better correlated with bird fecal steroids than with the typical sewage sterols. The results implied that sewage was not a significant source of fecal steroids, and therefore perhaps FIB to the study area. Instead, birds may be one possible source of the intermittently high levels of FIB observed in the lower Santa Ana River watershed and the nearby surf zone.

Endocrine disruption and health effects of caged mussels, Elliptio complanata, placed downstream from a primary-treated municipal effluent plume for 1 year

Freshwater mussels, Elliptio complanata, were caged in special benthic pens and were immersed at one upstream (Ups) site and two downstream sites (8 and 11 km) of a primary-treated municipal effluent plume for 1 year. The levels of metallothionein-like proteins (MT), lipid peroxidation, protein-free DNA strands and glutathione S-transferase (GST) activity were assayed in digestive gland, gill and gonad tissues to evaluate biological effects and damage. The levels of monoamines (serotonin and dopamine) in nerve ganglia, ATP-dependent transport activity and monoamine oxidase (MAO) activity were also investigated in the homogenates, synaptosomes and mitochondria, respectively. Results showed that significant amounts of sediment accumulated in cages and 82% of mussels survived the yearlong exposure period at the downstream sites. MT-like proteins were induced in all tissues with the following response intensity: gill (3-fold), digestive gland (1.4-fold) and gonad tissues (1.3-fold). Lipid peroxidation decreased (2.5-fold) in digestive gland but increased in gill (1.6-fold) and in gonad tissues (1.5-fold). GST activity was readily increased in digestive gland (2.5-fold), suggesting the presence of organic contaminants in the plume. Levels of protein-free DNA strands did not vary significantly in digestive gland and gill tissues but were significantly reduced in gonad tissues (2.5-fold) relative to the upstream site. In visceral nerve ganglia, both serotonin and ATP-dependent serotonin transport decreased 1.7-fold with a 4-fold increase of 5-hydroxyindole acetate (5-HIAA, a serotonin metabolite) level relative to the upstream site. However, MAO activity was somewhat reduced at downstream sites (0.7- to 0.9-fold of the activity at the upstream site). Dopamine levels were found to be decreased (1.5-fold), but dopamine ATP-dependent transport activity was increased 1.8-fold, suggesting reduced dopaminergic activity. These results indicate that estrogenic chemicals are likely at play, and the increased dopamine and decreased serotonin ATP-dependent transport suggest that the municipal plume was serotonergic for mussels located at the downstream sites. Mussels exposed for 1 year display a complex but characteristic pattern of responses that could lead to harmful health effects including neuroendocrine disruption of reproduction.

Consequences of xenoestrogen exposure on male reproductive function in spottail shiners (Notropis hudsonius).

There is limited information on the physiological consequences associated with exposure to xenoestrogens under field conditions. The objectives of this study were to determine the presence of estrogenic chemicals in the St. Lawrence River and their effects on male reproduction in the spottail shiner (Notropis hudsonius). Hepatic vitellogenin (VTG) mRNA levels in immature shiners indicate extensive estrogenic contamination spanning almost 50 km both upstream and downstream from the island of Montreal. Stages of spermatogenesis were assessed in fish captured at sites having varying levels of estrogenic contamination. In control fish, 95% had testis of either stage IV (50%) or stage V (45%) of spermatogenesis. At Ile Dorval, where VTG mRNA levels are moderate, fish had testes of stage III (38%) and IV (45%) and only 15% of fish were at spermatogenic stage V. In contrast, at Ilet Vert and Ile Beauregard, located in the sewage effluent plume from the City of Montreal and where hepatic VTG mRNA levels are high in fish, none of the fish were at stage V and 8% of fish at Ilet Vert were at stage II of development. Sperm concentration and various motility parameters were significantly lower in shiners from Ilet Vert as compared with those from Iles de la Paix (reference). Histological analyses of testes revealed that more than one-third of the fish captured at sites with the highest estrogenic contamination displayed intersex, a condition in which ovarian follicles were developing within the testis. These data indicate that there is significant estrogenic contamination in the St. Lawrence River that is associated with impaired reproductive function in male fish.

Effects of municipal effluents on serotonin and dopamine levels in the freshwater mussel Elliptio complanata

Sex differentiation and gametogenesis represent critical steps in the reproductive process and are subject to hormonal control by serotonin, dopamine and steroids such as estradiol-17β and testosterone. The purpose of this study sought to examine the endocrine-disrupting activity that a primary-treated municipal effluent might have on the metabolism of biogenic amine levels. First, serotonin receptors transfected in Chinese hamster ovary (CHO) cells were used to screen for the presence of serotonin receptor agonist or antagonist. Second, one group of Elliptio complanata mussels were exposed to single compounds likely to be found in municipal wastewaters and another group was exposed in situ to the municipal effluent plume for 90 days in experimental cages. Results showed that solid phase C-8 extracts of surface water downstream a municipal effluent could activate the transport of serotonin by receptors at a distance of at least 5 km from its outfall thereby indicating the presence of serotonin mimics in the effluent dispersion plume. Levels of serotonin and monoamine oxidase (MAO) activity in nerve ganglia of mussels exposed for 90 days to the municipal effluent were, respectively, reduced and increased at a distance 10-km downstream. Injections of estradiol-17β and nonylphenol in mussels decreased the levels of serotonin and dopamine, but increased MAO activity in the gonad and nerve ganglia. Exposure to estrogenic chemicals present in municipal effluents may therefore alter the normal metabolism of serotonin and dopamine, both of which are involved in sexual differentiation in bivalves and fish. Chemicals acting through E2 receptor-mediated pathways and serotonin receptors are likely to cause the observed effects.

Heat flux estimate of warm water flow in a low-temperature diffuse flow site, southern East Pacific Rise 17°25′ S

A low-temperature diffuse flow site associated with abundant vent fauna was found by submersible observations on the southern East Pacific Rise at 17°25′ S in 1997. This site was characterized by thin sediment covered pillow and sheet lavas with collapsed pits up to ∼15 m in diameter. There were three warm water vents (temperature: 6.5 to 10.5 °C) within the site above which the vented fluids rise as plumes. To estimate heat flux of the warm water vents, a temperature logger array was deployed and the vertical temperature distribution in the water column up to 38 m above the seafloor was monitored. A stationary deep seafloor observatory system was also deployed to monitor hydrothermal activity in this site. The temperature logger array measured temperature anomalies, while the plumes from the vents passed through the array. Because the temperature anomalies were measured in only specific current directions, we identified one of the vents as the source. Heat flux from the vent was estimated by applying a plume model in crossflow in a density-stratified environment. The average heat flux from September 13 to October 18, 1997 was 39 MW. This heat flux is as same order as those of high-temperature black smokers, indicating that a large volume flux was discharged from the vent (1.9 m3/s). Previous observations found many similar warm water flow vents along the spreading axis between 17°20′ S–30′ S. The total heat flux was estimated to be at least a few hundred mega-watts. This venting style would contribute to form effluent hydrothermal plumes extended above the spreading axis.

Inventory of nutrient compounds in the Yellow Sea

Nutrient species were analyzed from samples collected in the Yellow Sea in May 1998, including NO 3 −, NO 2 −, NH 4 +, PO 4 3−, SiO 3 2−, dissolved organic nitrogen (DON), particulate nitrogen, dissolved organic phosphorus (DOP), particulate phosphorus, etc. The exchange fluxes of nutrients across the sediment/water interface were determined by incubation of sediment on board the ship. The concentrations of N, P and Si compounds were high in coastal areas of the Yellow Sea, reflecting the effects of the Changjiang effluent plume, surface runoff in the west and east coasts and the circulation in the Yellow Sea. The high proportions of DON and DOP should be considered in models of nutrients cycling, which could help to explain observations of nutrient limitation in ecosystems of the Yellow Sea. The vertical distribution of N, P and Si compounds in the water column showed stratification feature. Simple box model was used to estimate the water-mass balance and nutrient budgets for the Yellow Sea. The data suggested that water turn-over time is about 2.2 years. Nutrient budgets demonstrated that net sink of NO 3 −, NH 4 + and SiO 3 2− can be mainly from water column into bottom sediments and/or transform to other forms of nitrogen (e.g. particulate pool and gas species). A net source of PO 4 3− is estimated to be 75% of inputs from external sources in the Yellow Sea.

Nitrous oxide sources and sinks in coastal aquifers and coupled estuarine receiving waters

Sources and sinks of the atmospherically reactive gas nitrous oxide (N 2O) were determined in the heavily nutrient loaded Childs River in Cape Cod, MA. Surface waters were supersaturated and bottom waters were depleted with N 2O throughout the system. In apparent septic effluent plumes, N 2O concentrations reached 3 orders of magnitude above atmospheric equilibrium. Because nitrate and N 2O concentrations correlated in groundwater entering the estuary, septic tank effluent appeared responsible for the supersaturated concentrations of N 2O in surface waters. A hyperbolic function fit nitrate and N 2O concentrations in the water column of the estuary with a maximum supersaturation of approximately 60 nM. From surface water supersaturation we predicted a release of 480 nmol N 2O m −2 h −1 to the atmosphere in the summer. Property plots of salinity vs. bottom-water N 2O suggested a benthic sink of N 2O. Consistent with this trend, sediments consumed rather than released N 2O in most flux measurements. Nutrient loading did not directly alter benthic N 2O flux, potentially because stratification limited exposure of sediments to nitrate-rich surface waters, but macroalgal cover increased benthic N 2O consumption. Sediment N 2O consumption averaged 111 nmol N 2O m −2 h −1 and correlated with oxygen uptake. Losses from the system to the atmosphere and sediments exceeded inputs of N 2O contaminated groundwater, which suggests missing N 2O sources.

Evaluation of caged freshwater mussels as an alternative method for environmental effects monitoring (EEM) studies

On three occasions between 1998 and 2000, freshwater mussels were collected by divers in Lake Memphremagog during the spring and transplanted to various locations in the St-François River (Quebec, Canada). Mussel growth was monitored by comparing total weight and length at the beginning and end of the exposure period. In 1998, mussels were caged for 60 days at 10 stations, including locations receiving treated effluents from three pulp and paper mills. Overall, there was an apparent trend of increased mussel growth from upstream to downstream along the river. However, mussels caged downstream from the effluent discharge of a bleached kraft pulp and paper mill grew more slowly than those caged immediately upstream in the river. In 1999 and 2000, we further investigated the situation in the vicinity of this bleached kraft mill. The measurements again indicated that growth of mussels in the effluent plume from this mill was reduced in comparison to sites upstream. Overall, in terms of growth, the caged mussels responded both positively and negatively to different environmental conditions. Compared with other monitoring approaches used at these sites during the same period, the caged mussel experiment results were consistent with the trends observed with the benthic invertebrate survey but not with the trends observed for fish.

Water flume study of the enhancement of buoyant rise in pairs of merging plumes

When multiple stacks are grouped or ganged together at a site, the effluent plumes are often observed to merge downwind, forming a single buoyant plume whose rate of rise is enhanced relative to the rise of the plumes individually. The magnitude of this rise enhancement depends on many factors, and the few available models for rise enhancement do not always agree with one another. In the present study the rise behaviour of pairs of merging, buoyant plumes was studied by physical modelling in a water flume at 1:500 scale. The experiments were conducted at several stack separation distances and various exit velocity ratios for stack pairs aligned with, or perpendicular to, the ambient flow. Limited experiments were also done with the stacks aligned at other angles to the flow. The stack releases were made buoyant by heating the source water, and the resulting plumes were measured with an array of sensitive temperature probes. From these measurements it was possible to determine the plume structure and rise rates. For small stack separations when the stacks are aligned with the ambient flow, the experimental results show that the enhanced rise is close to, and sometimes above, the maximum theoretical rise enhancement factor of 2 1/3. For the perpendicular orientation there is little or no rise enhancement. The rise enhancement for other stack orientations is somewhere between these two extremes. A plausible physical explanation for the observed behaviour is given, based on initial momentum shielding and line vortex dynamics in the merging plumes.

Identifying cryptic tidal influences within deltaic successions: an example from the Marsdenian (Namurian) interval of the Pennine Basin, UK

Research literature abounds on the depositional processes and products associated with macro-tidal regimes, whereas there is little available literature on sediments deposited in micro-tidal regimes. This paper presents new field-based sedimentological interpretations of the Marsdenian (Namurian, Carboniferous) interval of the Pennine Basin, a basin-fill that is classically regarded as the archetypal fluvial-dominated delta system. This paper reinterprets discrete lithostratigraphic units, and suggests they were deposited under the influence of weak tidal currents. We highlight three lithofacies that contain tidally influenced deposits within the Marsdenian interval of the Pennine Basin; a cross-bedded sandstone with mud drapes and reactivation surfaces, a heterolithic ripple-laminated sandstone with muddy drapes and silty mudstone interlaminations, and a rhythmic–parallel-bedded sandstone with mudstone–siltstone interlaminations. Evidence for cryptic tidal signatures in tractionally transported and reworked sediments is qualitative, and largely dependent on the sedimentologist's view of what constitutes a diagnostic number of tidal indicators (i.e. mud-drape couplets, reactivation surfaces). In areas away from either tractional deposition or reworking, sediments deposited from suspension are more likely to preserve indicators of tidal processes. This paper focuses on a lithofacies interpreted as a tidally influenced sand-rich delta-front mouthbar deposited from a buoyant effluent plume. Time-series analysis of laminae thickness variations in this facies implies that these variations are rhythmic. We review how the interaction of tidal currents and buoyant plume processes modifies depositional products. This model implies that the rhythmic variation observed in the Marsdenian interval is attributed to the modulation of plume deposition by tidal currents with a semi-diurnal and diurnal tidal periodicity.

A influência das condições de estabilidade atmosférica nas flutuações de concentração nas superfícies de um obstáculo isolado

A dispersão da pluma de poluentes próxima a obstáculos é um tema de interesse para arquitetos, agências reguladoras e meteorologistas da poluição do ar. Neste trabalho investiga-se as influências das condições de estabilidade atmosférica e do tempo de média na razão entre as concentrações máximas e as concentrações médias e na intensidade da flutuações de concentração, nas superfícies de um obstáculo isolado. Os dados para realização deste trabalho foram obtidos dos experimentos de campo realizados por Santos (2000). Foram utilizados detectores de foto-ionização com alta freqüência (50Hz) para se obter as flutuações turbulentas de concentração. Na região do fluxo incidente, as séries temporais de concentração apresentaram episódios de concentração nula seguidos de altos valores “instantâneos” de concentração, sugerindo que nesta região existem vórtices de escalas da turbulência de tamanhos maiores ou comparáveis ao tamanho da pluma. A estratificação térmica influenciou os valores da intensidade das flutuações turbulentas de concentração na região de esteira

Biomarker study of a municipal effluent dispersion plume in two species of freshwater mussels.

The toxicological effects of a primary-treated municipal effluent plume were investigated in two species of freshwater mussels, Elliptio complanata and Dreissena polymorpha, exposed for 62 days at sites upstream and downstream of an effluent outfall in the St. Lawrence River (Quebec, Canada). Levels of metallothioneins (MT), cytochrome P4501A1 activity, DNA damage, total lipids, relative levels of vitellins, and phagocytic activity (in E. complanata hemocytes) were determined after the exposure period. A parallel analysis measured heavy metals and coprostanol in mussel tissues. The results show that significant levels of coprostanol and some metals (specifically, Cu, Hg, Sb, Se, and Zn) had accumulated in mussels caged 5 km downstream of the effluent plume. Mixed-function oxidase activity, MT in gills, total lipids, DNA damage (in D. polymorpha only), and total hemolymph bacteria (in E. complanata only) had increased in these mussels, while levels of total cadmium (Cd), MT in digestive glands or whole soft tissues, phagocytic activity, and DNA damage in the digestive gland (in E. complanata only) were diminished. The exposure of mussels to surface waters contaminated by a municipal effluent led to many stress responses, depending on both the tissues and the species being examined.

Chemical Plume Tracing

Given a measurable concentration of a dissolved substance at a point within a fluid flow, where is the source? As physicists and engineers we often look at this problem from a more traditional perspective given a point source release of a substance, we seek to describe the temporal and spatial evolution of the effluent plume. Animals, seeking to evade predators or to locate mates or sources of food, contend with this problem routinely every day, and they have evolved a keen ability to locate these sources. Thus whereas our traditional approach when studying point source releases in the field of fluid mechanics is to seek to understand the fate of the source material and hence to study the forward problem, animals, and hence the biologists who study them, traditionally approach the study of the point-source-in-a-fluid as an inverse problem. This Special Issue on chemical plume tracing presents the work of an interdisciplinary research team, assembled by the Defense Advanced Research Projects Agency (DARPA) and the Office of Naval Research (ONR) to develop the ability to track chemical plumes to their sources. The fundamental approach to this research has been biomimetic. Both ONR and DARPA currently support research programs that seek either to integrate biological sensors or materials directly into new technology, or to capitalize on our knowledge about biological systems and processes to design new technological approaches to meet the demanding capability requirements of many armed services applications. This “biocentric” approach spans many disciplines and length scales. Some workers seek to enhance the performance of Navy surface and underwater platforms by a careful hydrodynamic analysis of swimming animals (Triantafyllou and Triantafyllou, 1995; Gordon et al., 2000; Bandyopadhyay, 2002). Others attempt to harness the power of single molecular motors to provide new energy sources (Montemagno and

Transport of Sewage-Contaminated Sediment in Northeastern Hamilton Harbour

Dispersal patterns associated with sewage discharges from an STP outfall in northeastern Hamilton Harbour were obtained in 1992 and 1996 using coprostanol as a tracer. Both surveys revealed a distinctive shore-parallel pattern, characterized by a south-eastward trend and a second transport direction toward the northwest and southwest. As physical support for the tracer patterns, vertical profiles of currents near the outfall were monitored during four time periods from 1991 to 2000. Current data indicated the flow at the outfall was complicated; there was flow in all directions at all depths. However, the cumulative surface flow followed the prevailing wind (toward the east and northeast), while the bottom flow was approximately in opposition to the surface flow (to the west-northwest). Combining this circulation structure with the seasonal variation in buoyancy of the effluent discharge, the bi-directional transport pattern interpreted from the tracer distribution could be explained using a model in which the STP effluent plume was advected by local current at a position in the water column where the plume was stable. During January through August when the effluent was denser than ambient harbour water, it tended to be advected by flows lower in the water column moving the plume toward the north to west and into the central basin. During the rest of the year, it was lighter and more influenced by surface currents, which advected the plume onshore (toward the east and northeast) where it was deflected by shoreline geometry in a shore-parallel direction toward the southeast.

Immunocompetence of bivalve hemocytes as evaluated by a miniaturized phagocytosis assay

Immune function in bivalves can be adversely affected by long-term exposure to environmental contaminants. Investigating alterations in immunity can therefore yield relevant information about the relationship between exposure to environmental contaminants and susceptibility to infectious diseases. We have developed a rapid, cost-effective, and miniaturized immunocompetence assay to evaluate the phagocytic activity, viability, and concentration of hemocytes in freshwater and marine bivalves. Preliminary experiments were performed to optimize various aspects of the assay including 1) the time required for adherence of hemocytes to polystyrene microplate wells, 2) the time required for internalization of fluorescent bacteria, 3) the ratio of hemocytes to fluorescent bacteria in relation to phagocytosis, 4) hemolymph plasma requirements, and 5) the elimination of fluorescence from (noninternalized) bacteria adhering to the external surface of hemocytes. The results of these experiments showed the optimal adherence time for hemocytes in microplate wells to be 1 h, that phagocytosis required at least 2 h of contact with fluorescently labeled E. coli cells, that the number of fluorescent E. coli cells had a positive effect on phagocytic activity, that at least 2.5 million cells/mL were required to measure a significant intake, and that a linear increase in uptake of bacteria (R = 0.91; p < 0.01) could be obtained with concentrations of up to 1.3 x 10(6) hemocytes/mL. Afterward, the assay was used in two field studies to identify sites having the potential to affect the immunocompetence of bivalves. The first study was conducted on Mya arenaria clams collected at selected contaminated sites in the Saguenay River (Quebec, Canada), and the second examined Elliptio complanata freshwater bivalves that had been exposed to a municipal effluent plume in the St. Lawrence River (Quebec, Canada). In the Saguenay River field study a significant increase in phagocytosis was observed at sites closest to polluted areas. Phagocytotic activity varied over time and was highest during the warmest months (June, July, and August), closely paralleling the spawning period of Mya arenaria clams. In contrast, a drop in phagocytic activity was observed in Elliptio complanata mussels exposed to surface water 4 km downstream of a major municipal effluent plume, with a concomitant increase in the number of hemocytes in the hemolymph. It appears that both immunosuppressive and immunostimulative effects are likely to occur in the field and that responses will be influenced by the type and intensity of contaminants at play.

Modeling the Mixing of Wastewater Effluent Discharged from Ocean Outfalls using a Hybrid Model

A hybrid model in which line plume equations are used for the computation of the initial mixing in the near field and a random-walk particle-tracking model is used for the simulation of the far field transport was developed to predict the mixing characteristics of wastewater effluent plumes discharged from ocean outfalls. In the particle-tracking model, the governing equation is transformed to the σ coordinate to use grid velocities computed by the σ-layered hydrodynamic model. In addition, the particles introduced at the end of the near field are distributed with the normal distribution to represent the vertical concentration distribution of the wastewater plume. The results of model applications to the Masan sea outfall in Korea show that there is no large difference between the minimum dilutions for the summer and winter seasons even though the effluent plume is trapped at mid-depth during the summer season due to density stratifications. The periodic variation of the ambient current does not have a significant effect on near field dilutions, since the ambient velocities at the outfall site are quite low. The simulation results of the far field transport with settling processes reveal that concentrations at the bottom layer in the vicinity of the outfall site Eire higher than those in the remote sites from the outfall. This simulated result agrees with the depositional trend of the contaminated sediment that was obtained from the field survey.

Impact of Bleached Kraft Pulp Mill Effluent on the Nearshore Benthic Community of Jackfish Bay, Lake Superior

Abstract We assessed the impact of bleached kraft pulp mill effluent on benthic invertebrate community structure in the shallow (1 m) nearshore waters of Jackfish Bay, Lake Superior. Duplicate benthic samples were collected from 0.5 m2 quadrats at twenty-three stations along two shorelines of Jackfish Bay up to 1800 m from the point of effluent discharge, and from a reference station located within the Jackfish Bay study area. Detrended correspondence analysis (DCA) revealed a gradient of stations on both shorelines which was strongly correlated with distance from effluent outfall and hence exposure to the effluent plume. Within this gradient were two distinct clusters of stations. The first cluster contained all but one station on both shores &amp;lt;300 m from the outfall; these stations receive constant exposure to the effluent and were dominated (&amp;gt;90%) by tubificids (Limnodrilus hoffmeisteri, Tubifex tubifex, T. ignotus and Spirosperma ferox) and the naidid Chaetogaster diaphanus. The second cluster contained all stations on both shores &amp;gt;300 m from the outfall; community structure at these stations was generally comparable to that at the reference site and was characterized by several species of Chironomidae, C. diaphanus and Nais barbata, and low numbers of several insect taxa. The results of this study show that benthic community structure in nearshore environments can be significantly impacted by pulp mill effluent and should be considered in monitoring assessments. At Jackfish Bay, such impacts appear to be restricted primarily to within the first 500 m of effluent discharge.

Field measurement and modelling of two-dimensional river mixing

Wastewater treatment facilities commonly discharge effluent to large receiving streams. An effluent plume may easily extend for many tens of kilometres downstream of a discharge point. A characteristic of the effluent plume is the existence of significant transverse concentration gradients in the river as the discharged effluent slowly mixes with the river water. Within this two-dimensional, transverse mixing zone accurate delineation of the effluent plume is essential for water quality monitoring and for management of the receiving stream. The capability to mathematically model two-dimensional river mixing and to predict effluent plume concentrations is a valuable tool for water quality management. An overview of two-dimensional river mixing theory is presented. Tracer methods for delineating effluent plumes resulting from continuous or transient input to rivers are described, and the results of tracer studies conducted on the Athabasca River in western Canada are presented. A computer modelling procedure for simulating two-dimensional river mixing is described. Application of the model is explained and comparison of model output to measured tracer concentrations is presented.

Evaluation of estrogenic effects of municipal effluents to the freshwater mussel Elliptio complanata

Municipal effluents are an important source of estrogens to the aquatic environment. The purpose of this study was to examine the estrogenicity of municipal effluents to the indigenous freshwater mussel, Elliptio complanata. First, estradiol-binding sites in gonad homogenates were characterized to determine the binding affinity and specificity of estrogens. Mussels were exposed to increasing concentrations of a municipal effluent for 96 h at 15°C. In another experiment, mussels were placed in cages and submerged for 62 days at 1.5 km upstream and 5 km downstream of a municipal effluent plume in the St. Lawrence River. Mussels were harvested for assessment of vitellogenin-like proteins in the hemolymph and determination of total lipid, carbohydrate and protein in the gonad. The presence of specific estrogen-binding sites was found in both male and female gonads. Binding of estradiol to cytosol proteins reached saturation, yielding a dissociation constant of 0.4 nM. Vitellogenin (Vg) levels increased significantly in both the hemolymph and the gonad after exposure to the effluent. Moreover, females appeared to be more sensitive than males to producing Vg. Mussels exposed in situ to contaminated surface waters had higher levels of Vg at the downstream site, again, females had higher levels of Vg than did males. On the other hand, lipid and sugar levels in male gonads were significantly increased at the downstream site. Moreover, mussels at the downstream site had decreased shell growth length and increased total and soft tissue weights. We conclude that municipal effluents contain bio-available xenoestrogens at levels sufficient to elicit effects in freshwater mussels.