SUMMARY OF MAJOR ISSUES AND FINDINGS
STREAM-BOTTOM SEDIMENT - Stream-bottom sediments in some urban streams and at some sites on large rivers in the Hudson River Basin have elevated concentrations of metals, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) compared to results from sites in other NAWQA Study Units; some of these concentrations exceed federal or state water-quality standards.
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The Sawmill River at Yonkers, the most densely populated urban site studied in the Hudson River Basin, had some of the highest concentrations of metals in stream-bottom sediments among NAWQA sites nationwide (p. 6). Highly urban areas are the source of most of the metals in streams draining urban and large watersheds.
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The distribution of chromium concentrations in Hudson River stream-bottom sediments is consistent with previous observations of a point source of heavy metals on the upper Hudson River (p. 6-7).
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Concentrations of lead, mercury, and zinc in stream-bottom sediments were positively related to the percentage of urban land within the watershed. Many of the metals concentrations in sediment from urban sites exceeded the proposed New York State Department of Environmental Conservation (NYSDEC) Severe Effect Levels for stream-bottom sediment (p. 6-7).
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NYSDEC proposed Severe Effect Levels for metals were not exceeded in any stream-bottom-sediment samples from sites in forested or agricultural watersheds (p. 6).
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PCBs persist in stream-bottom sediment despite being banned more than 20 years ago. PCB concentrations in Hudson River bottom-sediments exceeded the proposed NYSDEC criteria for human health bioaccumulation at all sites at which they were detected (p. 8-9) and were among the highest at NAWQA sites nationwide (p. 16).
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Spatial patterns in concentration of PAHs within the basin corresponded with factors such as location in the Hudson River Basin and proximity to urban areas (p. 8).
FISH TISSUE - Although banned for more than 20 years, PCBs, DDT and (or) its breakdown products were detected in composites of whole fish from many sites, and were most frequently detected in samples from sites on large rivers and in small urban watersheds.
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PCB concentrations in composite whole-fish samples from the Hudson River at Poughkeepsie and the Mohawk River near Utica exceeded the Food and Drug Administration (FDA) action level of 2,000 micrograms per kilogram of edible flesh (fillets). This indicates the potential for elevated concentrations in edible portions, and has prompted further investigation and fish-consumption advisories for selected species in a 40-mile section of the Mohawk River. Consumption advisories remain in effect for most species in parts of the Hudson River (p. 9).
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Concentrations of organochlorine compounds other than PCBs in composites of whole fish were below FDA action levels for edible flesh at all sites sampled. This suggests that concentrations in edible portions of these samples would not have exceeded FDA action levels for those compounds (p. 8).
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PCBs, DDT and its breakdown products, and chlordane were more likely to be detected in fish tissue than in stream-bottom sediments at sites where both whole fish samples and stream-bottom sediment samples were collected. This suggests that bioaccumulation through the food chain occurs even where these compounds cannot be detected in stream-bottom sediment (p. 8).
STREAM ECOLOGY - Most agricultural and urban streams studied supported a smaller number of intolerant fish and macroinvertebrate species than that expected in streams with undisturbed chemistry and (or) habitat.
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Fish communities at the three most highly urbanized sites sampled were numerically dominated by a single fish species. Intolerant species were entirely absent or rare at these sites (p. 10-11).
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Stream-habitat degradation was severe at channelized sites in cities and was moderate at agricultural sites where streambank vegetation had been removed and where streambank erosion had occurred (p. 11, 17). Benthic macroinvertebrate groups sensitive to suspended and (or) deposited sediment appear to be replaced by sediment-tolerant species in streams with streambank erosion (p. 11).
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Urban streams in some densely populated watersheds with undisturbed streambanks supported larger numbers of fish species intolerant to impaired water quality than urban streams with disturbed streambanks (p. 11, 17). The presence of an extensive, forested buffer zone on and adjacent to streambanks appears to mitigate potential adverse effects of urban and agricultural land use on fish communities.
SURFACE-WATER AND GROUND-WATER CHEMISTRY - The concentrations of dissolved pesticides and nutrients in samples from most sites in the Hudson River Basin were below the national median concentrations. In some samples, however, water-quality standards or guidelines for these and other constituents were exceeded.
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In general, concentrations of pesticides and other dissolved constituents are low in ground water and surface waters of the Hudson River Basin. Although 18 different pesticides or pesticide-degradation compounds were detected in three streams sampled at least monthly over 2 years (total of 108 samples), only 2 samples contained a pesticide concentration higher than a U.S. Environmental Protection Agency (USEPA) drinking-water standard; however, only 12 of the 18 compounds have established standards (p. 12).
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Atrazine was the most commonly detected pesticide in surface water and ground water and was found in nearly every sample in which any other pesticide was detected (p. 13-14). Atrazine is one of the most commonly used pesticides in the basin, hence the frequency of its detection with other pesticides is not unusual.
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Although pesticides were detected throughout the year, pesticide concentrations in streams were generally highest immediately after field application and during the first storm runoff following application (p. 13).
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In a spring 1994 survey of 46 stream and river sites in the Hudson River Basin, 32 percent of pesticide detections were insecticides in streams draining watersheds with a significant percentage of urban land. This rate of detection was 3.5 times that of streams draining agricultural or mixed-land-use watersheds. Fifty percent of all insecticide detections were in streams draining urban areas, a disproportionate amount given that only 22 percent of the streams sampled drained these areas (p. 14). The percentage of insecticide detections in urban areas reflects the use of these products on lawns and similar non-agricultural areas.
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Pesticides were detected in ground water from 25 percent of wells used for domestic water supply, no more than 2 pesticides were detected at any individual well (p. 14), and none of these detections were at concentrations above any available USEPA drinking-water standard.
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Nitrate concentration in ground water indicated the effects of human activity (concentration greater than 3.0 mg/L) in 38 percent of the samples from beneath agricultural fields, in 23 percent of the samples from beneath urban/residential areas, and in 16 percent of the samples from domestic wells (p. 15).
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Nitrate concentrations in ground water beneath agricultural areas were above the national median for such areas (p. 18). Two of sixteen wells sampled (12.5 percent) had concentrations above the USEPA Maximum Contaminant Level (MCL) (10 mg/L), however none of the wells was used as a source of drinking-water (p. 15).
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About one-third of the ground-water samples from beneath urban/residential areas contained at least one volatile organic compound, but none of the concentrations exceeded any available water-quality standards (p. 19).
