A statewide sediment and water quality approach to characterize pollution in wadeable streams of South Carolina.

摘要

At present, little data is available concerning the overall quality of small aquatic ecosystems in South Carolina. The data presented here comprises the elemental contamination results from the first two years of an ongoing study with the South Carolina Department of Natural Resources of wadeable streams in South Carolina. The overall goal of this thesis is to assess overall ecosystem quality in order to provide information needed for improved management strategies. The data focus on elemental contaminants found in water and sediments in 2006 and 2007 and relationships between metals and land cover in the drainage areas or watersheds of the sites sampled. Sites were randomly selected using known streams and GIS-determined watersheds of appropriate size (less than 150 km2). GIS and the National Land Cover Data Set (NLCD) were used to determine the land use distribution for each sampled watershed. Water and sediment samples were collected and analyzed using Inductively Coupled Plasma -- Mass Spectrometry, Inductively Coupled Plasma -- Atomic Emission Specrtrometry and Cold Vapor Atomic Absorption Spectrometry. Among the elements of interest are aluminum, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, silver, zinc, and others (total of 17 elements of interest). Results indicate that a number of sites exceed the published US EPA constant contaminant concentration (CCC) and contaminant maximum concentration (CMC) for a few waterborne or dissolved metals (e.g., cadmium, copper and nickel). In addition, a small number of sites exceed published risk threshold values for metal-contaminated sediments. Linear regression was used to correlate individual dissolved element measurements with land cover in individual watersheds and ecoregions. Results indicate that changes in land can change pollutant loads and impact the quality of the stream. The strongest relationships were observed for agricultural and forest land use with several metals (e.g., chromium, nickel, selenium, and potassium). Developed land area did not show significant effects in these small and largely rural watersheds. Relationships were also considered for the whole study and are separated by watershed and ecoregion. Principle components analysis (PCA) was applied to watershed land uses to simplify interpretation and to reveal parameters responsible for metal contamination variability. A geostatistical analysis indicated elemental contamination can be focused in smaller areas around the state of South Carolina and that there are indeed hot-spots of elemental contamination.