Surface waters freshwaters

Dissolved humic substances (DHS) are the main constituents of the dissolved organic carbon (DOC) pool in surface waters (freshwaters and marine waters), groundwaters, and soil porewaters and commonly impart a yellowish-brown color to the water system. Despite the different origins responsible for the main structural characteristics of DHS, they all constitute refractory products of chemical and biological degradation and condensation reactions from plant or animal residues and play a crucial role in many biogeochemical processes. 

Maryland Criteria for toxic substances in surface waters Freshwater Acute Chronic Saltwater Acute Chronic Drinking water 20 gg/L 5.0 gg/L 300 gg/L 71 gg/L 50 gg/L BNA 2001... 

Nonreplenishable (fossil) groundwater can be tapped, but such extraction depletes reserves in much the same way as extractions from oil wells do. The terrestrial renewable freshwater supply, RFITTj, equals precipitation on land, which then subdivides into two major segments evapotranspiration from the land, and mnoff to the sea, T. Because groundwater and surface water are often hydrauhcaHy coimected, soil infiltration and groundwater... 

Water in Industry. Freshwater for industry can often be replaced by saline or brackish water, usually after sedimentation, filtration, and chlorination (electrical or chemical), or other treatments (22). Such treatment is not necessary for the largest user of water, the electric power industry, which in the United States passed through its heat exchangers in 1990 about 40% of the total supply of surface water, a quantity similar to that used for agriculture, and it was 48% of the combined fresh and saline water withdrawals (10). Single stations of 1000 MW may heat as much as 12 Mm /d by as much as 10—15°C. 

In general, silver concentrations in surface waters of the United States decreased between 1970-74 and 1975-79, although concentrations increased in the north Atlantic, Southeast, and lower Mississippi basins (USPHS 1990). About 30 to 70% of the silver in surface waters may be ascribed to suspended particles (Smith and Carson 1977), depending on water hardness or salinity. For example, sediments added to solutions containing 2 pg Ag/L had 74.9 mg Ag/kg DW sediment after 24 h in freshwater, 14.2 mg/kg DW at 1.5% salinity and 6.9 mg/kg DW at 2.3% salinity (Sanders and Abbe 1987). Riverine transport of silver to the ocean is considerable suspended materials in the Susquehanna River, Pennsylvania — that contained as much as 25 mg silver/kg — resulted in an estimated transport of 4.5 metric tons of silver to the ocean each year (USEPA 1980). The most recent measurements of silver in rivers, lakes, and estuaries using clean techniques show levels of about 0.01 pg/L for pristine, nonpolluted areas and 0.01 to 0.1 pg/L in urban and industrialized areas (Ratte 1999). 

OCCURRENCE OF SURFACTANTS IN SURFACE WATERS AND FRESHWATER SEDIMENTS—I. ALKYLPHENOL ETHOXYLATES AND THEIR DEGRADATION PRODUCTS... 

Exposure concentrations. Concentrations of NP and NPEO occurring in the aquatic environment in the EU have been summarised in Chapters 6.2.1 and 6.3.1. It can be concluded that in both freshwater and marine surface waters, concentrations of NP still exceed the PNEC of 0.33 pig L-1 derived in the EU document cited above [10]. Whereas in several freshwater systems in NW Europe (notably The Netherlands... 

Density stratification in coastal waters can result from increased freshwater flows from land due to heavy rainfall, and from seasonal surfece warming. Changes in winds and currents alter upwelling conditions that can also affect stratification, while concurrently affecting nutrient resupply to the surface waters. These changing environmental... 

Information pertaining to the occurrence of cresols in surface waters was limited. STORET (1989) and the CLAPS (1988) contained no records for o-cresol in ambient surface water. o-Cresol was detected in freshwater samples from Spirit Lake, Washington, on August 7, 1980 and from South Fork Castle Lake and Smith Creek, Washington, on September 11, 1980 at unreported concentrations (McKnight et al. 1982). The presence of cresols was attributed to the Mount St. Helens eruption on May 18, 1980 (McKnight et al. 1982). Whether or not the cresols originated from wood fires or the actual eruption was not clarified. 

Phytoplankton marine and freshwater plants that float in the surface waters, many are microscopic and include different forms of algae... 

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