Contaminated Sediments: Inorganic Constituents

Abstract

Owing to a variety of physical and chemical factors, in conjunction with aquatic physicochemical conditions, fluvial/lacustrine suspended and bed sediments can act as both sources and carriers of a wide variety of inorganic constituents and nutrients. Many of these constituents reflect local environmental conditions and are derived from both point and nonpoint sources. When sources have an anthropogenic origin, and chemical levels exceed the typical range of local baseline concentrations, sediments can be described as contaminated. Most land‐use categories (e.g. agriculture, forested, and rangeland) do not appear to exert a substantial effect on sediment‐associated inorganic chemical levels. On the other hand, mining and/or mining‐related activities are a major exception, and although this land use can be geographically limited, it can cause extensive local and downstream sediment contamination. Urban centers and urbanization (increasing amounts of impervious surfaces), as a result of industrial and wastewater discharges, power generation, and transportation‐related activities, also can cause extensive sediment contamination. Population density can be related to urbanization and, at levels ≥27 people (p) km −2 , also appears to exercise a substantive effect on sediment chemistry. In fact, population density appears to be a more consistent influence than urban percentage, and displays stronger positive correlations with sediment contamination. The most common sediment‐associated inorganic/nutrient contaminants appear to be Pb, Hg, Ag, Zn, Cd, Cu, Sb, S, Ni, Sn, Cr, As, TC (total carbon), Co, Fe, P, and TOC (total organic carbon).

A Review of Selected Inorganic Surface Water Quality-Monitoring Practices: Are We Really Measuring What We Think, and If So, Are We Doing It Right?

“…Turbidity, which results from variations in SSC and color, is responsible for most current sediment-associated total maximum daily load (TMDLs) calculations. , Other than SSCs and/or turbidity, sediment-associated chemical concentrations largely are unregulated because there are few if any established limits for sediment-associated chemical constituents. The reasons for this appear to relate to disagreements over how to estimate sediment-associated constituent bioavailability. − Currently, only five countries regulate sediment-associated chemical constituents: Canada, New Zealand, Australia, The Netherlands, and Germany; however, many have established guidelines. , Contrariwise, when environmental/water-quality monitoring program objectives are nonregulatory, for example, estimating annual fluxes for various chemical constituents (Figure ; SI Figure 3), or the determination/identification of the sources/sinks of suspended sediment (e.g., sediment fingerprinting), or identifying water-quality trends, or for evaluating land-use impacts, or in dealing with eutrophication issues, then sediment-associated chemical constituents should be included. ,, …”

“…Inorganic constituents that primarily are sediment-associated are called hydrophobes, and normally are bound to sediment particle surfaces . This group includes heavy metals/trace elements (e.g., Pb, Zn, Hg) and nutrients (e.g., N, P).…”

“…In countries where sediment-associated chemistry is regulated, elevated levels of these constituents are viewed as contaminants. Also, numerous sediment-associated constituents are markers for various land-use effects. − The annual fluxes of sediment-associated nutrients can be substantial. For example, in the lower MRB more than 75% of the P, 50% of the C and 30% of the N are sediment bound .…”

Mining Activities and Associated Environmental Impacts in Arid Climates: A Literature Review

“…Particle size fractionation has been used to investigate land use and fluvial deposition of contaminated mine waste (Horowitz & Stephens, 2008;Horowitz, 1993Horowitz, , 1988Horowitz, , 2008. Horowitz (2008) and others used air elutriation to evaluate each fraction of contaminated sediment and found that the finer aeolian fraction contained 10 times more metals than the larger fractions (Callender, 1988;Lu et al, 2012).…”

“…Horowitz (2008) and others used air elutriation to evaluate each fraction of contaminated sediment and found that the finer aeolian fraction contained 10 times more metals than the larger fractions (Callender, 1988;Lu et al, 2012). When using this method of evaluating the lighter fractions, it was obvious that contaminants associated with the smaller particles can be transported farther (compared to shorter transport for larger size particulates) and deposited by aeolian processes in areas where there is no anthropogenic activities (Horowitz & Stephens, 2008;Lu et al, 2012).…”