Abstract
Suspended particles in rivers can act as carriers of potentially bioavailable metal species and are thus an emerging area of interest in river system monitoring. The delineation of bulk metals concentrations in river water into dissolved and particulate components is also important for risk assessment. Linear relationships between bulk metal concentrations in water (CW,tot) and total suspended solids (TSS) in water can be used to easily evaluate dissolved (CW, intercept) and particle-bound metal fluxes (CSUS, slope) in streams (CW,tot = CW + CSUS TSS). In this study, we apply this principle to catchments in Iran (Haraz) and Germany (Ammer, Goldersbach, and Steinlach) that show differences in geology, geochemistry, land use and hydrological characteristics. For each catchment, particle-bound and dissolved concentrations for a suite of metals in water were calculated based on linear regressions of total suspended solids and total metal concentrations. Results were replicable across sampling campaigns in different years and seasons (between 2013 and 2016) and could be reproduced in a laboratory sedimentation experiment. CSUS values generally showed little variability in different catchments and agree well with soil background values for some metals (e.g. lead and nickel) while other metals (e.g. copper) indicate anthropogenic influences. CW was elevated in the Haraz (Iran) catchment, indicating higher bioavailability and potential human and ecological health concerns (where higher values of CSUS/CW are considered as a risk indicator).
Highlights
River bed sediment pollution is a long-standing area of environmental concern [1,2]
The dissolved (CW, intercepts) and particle-bound (CSUS, slopes) concentrations of single metals were calculated for each event/sampling campaign using linear regressions between total concentrations of metals and the respective total suspended solids (TSS) values in river water/artificial suspensions
The additional laboratory tests– spanning a larger TSS range–show very good agreement with the natural bulk river water samples. Both data sets were in close agreement with data reported by Nasrabadi et al [18] for samples taken from ten locations distributed over the whole Haraz Catchment in May and December 2012. This indicates that the variability of CSUS and CW is low in the river water despite the relatively large catchment area and diverse geology
Summary
River bed sediment pollution is a long-standing area of environmental concern [1,2]. Toxic metals/metalloids are readily transported by carriers (e.g. suspended solids) towards lakes, estuaries, or oceans. In contrast to many other frequently studied pollutants (e.g. organic compounds) they are non-degradable [3,4]. Environmental quality standards for many metals (e.g., nickel, lead) are based on dissolved or bioavailable concentrations [5], suspended sediments may contribute to mass flux and relocation of metals.
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