Investigation of sediment properties and provenance in the EastRiver (Dongjiang), China

Abstract

Fluvial sediments, as a product of erosion, are associated with a wide range of environmental issues. In particular, sediment quality and its origin represent one of the focuses of contemporary water management. This study examines the characteristics and provenance of fine bed sediments in a humid sub-tropical macro scale catchment – the East River basin in South China. Sampling was carried out in the dry seasons of 2007 – 2008, following the protocol of USGS OFR 94-458. Sample density was one per 200 km2. The particle size, grain roundness, geochemistry, mineral magnetic parameters, clay mineralogy, along with C and N, were determined for the <2-mm and <63-μm size fractions.

A geochemical baseline, along with its spatial distribution, was developed for the East River by using a statistical approach. The geochemistry was generally consistent with upper crustal abundance of China and with world average suspended matter concentrations. Some analytes, such as arsenic and sulphur, were elevated and were found to associate with anthropogenic activities, whilst rare earth elements (REEs) were affiliated with the igneous geology in the study basin. These associations were also detected from exploratory factor analysis, as well as the longitudinal profiles developed for the main stem of the river.

Sediment source apportionment was carried out by utilizing the fingerprinting procedure on three geologic groups. Results indicate that provenance of sediments in the East River was more or less uniform among the different geologies, but the accuracy of the apportionment has been compromised by the relatively high within-group variance of the source categories. Results suggested that source apportionment was only viable by utilizing the <63-μm fraction, and grain size correction factor shall not be employed on samples with a high granulometric variance. REE represents a robust signature to indicate provenance from igneous lithology, in particular, granites.