Ranking of Basin-Scale Factors Affecting Metal Concentrations in River Sediment

Tom Lotz,Christian Opp

doi:10.3390/app12062805

Abstract

River sediments often contain potentially harmful pollutants such as metals. Much research has been conducted to identify factors involved in sediment concentrations of metals. While most metal pollution studies focus on smaller scales, it has been shown that basin-scale parameters are powerful predictors of river water quality. The present study focused on basin-scale factors of metal concentrations in river sediments. The study was performed on the contiguous USA using Random Forest (R.F.) to analyze the importance of different factors of the metal pollution potential of river sediments and evaluate the possibility of assessing this potential from basin characteristics. Results indicated that the most important factors belonged to the groups Geology, Dams, and Land cover. Rock characteristics (contents of K2O, CaO, and SiO2) and reservoir drainage area were strong factors. Vegetation indices were more important than land cover types. The response of different metals to basin-scale factors varied greatly. The R.F. models performed well with prediction errors of 16.5% to 28.1%, showing that basin-scale parameters hold sufficient information for predicting potential metal concentrations. The results contribute to research and policymaking dependent on understanding large-scale factors of metal pollution.

Highlights

IntroductionRivers can be proxy indicators of many landscape and catchment processes
As matter transport systems, rivers can be proxy indicators of many landscape and catchment processes
The information obtained for the watersheds from the NHDPlus was substituted with information from the National Inventory of Dams (NID) [27], which stores information about more than 90,000 dams in the U.S In the NID, different types of dam construction are distinguished, among them Gravity (PG), which are created from a single block of concrete or stone masonry; Earth (ER), which are constructed from soil; Rockfilled (ER), which are constructed from rocks and boulders; or Timber crib (TC), constructed from wood [28]

Summary

Introduction

Rivers can be proxy indicators of many landscape and catchment processes. Before water reaches the stream, it moves from precipitation through many different river basin features, such as vegetation, soil, and geology. The water may dissolve substances from soil and rocks during this movement or transport matter. As a kind of archive, the sediments in the river itself, along its banks, and the whole floodplain can be used to determine relationships and interactions between processes such as land cover change, runoff formation, and soil erosion [1,2]. Sediments can function as matter sinks for different materials and chemicals. Depending on conditions, this function can be reversed. The same sediments can become sources, releasing accumulated materials back into the river water [3,4]

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Conclusion