Contamination freshwater system

Northwestern Ontario, Canada, from a heavily mercury-contaminated freshwater system Liver ... 

Salts are sometimes added to drilling muds to obtain certain desired mud characteristics. They can also enter the drilling fluid through contamination by addition of makeup water, formation-fluid inflow, and drilled formations such as salt domes, gypsum or anhydride formations. In freshwater systems, if salt contamination reaches undesirable levels, the following methods should be considered for control. 

Landfill leachate is an important point pollution source to water body, which contains DOM with a large number of unknown molecules that actively involve in biogeochemical and environmental processes (Chin et al. 1997). DOM not only plays an important role in freshwater systems for the mobility of toxic heavy metals and other pollutants but also may itself be a groundwater contaminant (Christensen etal. 1998). 

In a study involving several contaminated freshwater streams in New Jersey Pinelands, Ross and Sherrell [8] have used CFF, with a 10 kDa (ca. 3 nm) cutoff, to separate the filtrate (<0.45 pm) into colloidal and truly dissolved fractions in freshwater systems. The colloidal fraction,/cou, was calculated by difference ... 

Aquatic Contamination by Gold Ore Extractants. The separate use of mercury and cyanide has led to the contamination of freshwater systems. 

A comprehensive review on the environmental behaviour of anthropogenic contaminants in the sedimentaiy matter of freshwater systems was published very recently (Warren et al. 2003)... 

Between 1988 and 1992, Cs levels declined in sediments from 52 lakes in southern Finland by 27% and in fish tissues by 26-39%. Radiocesium-137 concentrations in whole freshwater fishes from Norwegian lakes contaminated by Chernobyl fallout were quite variable. Major sources of Cs variations included the fish weight and growth rate, and these were related to fish age and diet. Change over time in dissolved phase Cs concentrations of lake water is significantly related to water residence time and mean lake depth these variables have been incorporated into models to predict estimates of Cs decline in freshwater systems. Radiocesium-137 activity in muscle of brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) from six lakes in Cumbria, England, between June 1986 and October 1988 were highest between December 1986 and March 1987, with maximum values of about 1200 Bq/kg FW in trout and 350 in char. Maximum Cs values were related to the initial concentration of Cs in both water... 

Bioturbation in the upper layers of a cap can lead to rapid chemical migration. The normal feeding and burrowing activities of benthic organisms result in the rapid movement of particles and the contaminants with which they are associated, as well as the movement of porewater. The layer that is effectively mixed by organisms, hbio, is relatively small. More than 90% of the 240 observations of bioturbation mixing depths in fresh and salt water reported by Thoms [5] were 15 cm or less, and more than 80% were 10 cm or less. In freshwater systems, most measurements of mixing depth are of the order of 3-5 cm. Most of these measurements were based upon particle-associated radionuclides and the observed effective particle diffusion coefficients,... 

In practice, the extent to which a freshwater system has been stressed by pollutants can be determined through an examination of the presence or absence of specific chironomid species with known pollution tolerances. Finer scale analyses of relative abundances can also provide clues to the presence of specific stressors. For instance, high abundance of a chironomid species such as Dicrotendipes nervosus frequently indicates the presence of abundant decomposable organic matter, whereas species such as Cricotopus bicinctus are found more commonly in systems with high levels of inorganic contaminants (7). Since even closely related species can have distinct pollution tolerances, the need for proper identifications is particularly important and useful (d). 

DOM related to natural systems is derived predominantly from plant material and where microbial activity is slow and weak but nevertheless sustained. The unique origins of wastewater DOM are highlighted in their associated EEMs, which are most notably different from EEMs of DOM from marine and freshwater systems, where peak C predominates (Hudson et al 2007). The unique spectral characteristics of wastewater DOM have facilitated the tracking of sewage contamination in aquatic systems (Galapate et al., 1998 Baker, 2001 Baker et al., 2003, 2005 Chen et al., 2003 Holbrook et al., 2005 Hudson et al., 2008 Carstea, 2010). 

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