Abstract
Metal accumulation in sediments threatens adjacent ecosystems due to the potential of metal mobilization and the subsequent uptake into food webs. Here, contents of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) and trace elements (Ga, In, Mo, and Se) were determined for river waters and bed sediments that received sewage discharged from traditional and semiconductor industries. We used principal component analysis (PCA) to determine the metal distribution in relation to environmental factors such as pH, EC, and organic matter (OM) contents in the river basin. While water PCA categorized discharged metals into three groups that implied potential origins of contamination, sediment PCA only indicated a correlation between metal accumulation and OM contents. Such discrepancy in metal distribution between river water and bed sediment highlighted the significance of physical-chemical properties of sediment, especially OM, in metal retention. Moreover, we used Se XANES as an example to test the species transformation during metal transportation from effluent outlets to bed sediments and found a portion of Se inventory shifted from less soluble elemental Se to the high soluble and toxic selenite and selenate. The consideration of environmental factors is required to develop pollution managements and assess environmental risks for bed sediments.
Highlights
Our study site locates at the basin of the Fazih and the Wu River in Taichung, Taiwan (Fig. 1)
Data sets on environmental factors and metal contents in river water and bed sediments were subjected to principal component analysis (PCA) to ascertain factors that were responsible for the variation in metal loading in sediments
The distribution and accumulation of heavy metals and trace elements in relational to environmental factors in the basin of the Fazih and the Wu River that received sewage effluents from traditional and semiconductor industrial activities was determined by PCA
Summary
Our study site locates at the basin of the Fazih and the Wu River in Taichung, Taiwan (Fig. 1) This basin has received treated wastewater from the Taichung Industrial Park, the Taichung Precision Machinery Innovation Technology Park, the Central Taiwan Science Park, and untreated wastewater from domestic original equipment manufacturers (OEM). We aimed to determine how environmental factors such as pH, electrical conductivity (EC), oxidation-reduction potential (ORP), OM, amorphous (oxalate-extractable) aluminum (Al) and (Fe) dominate the accumulation of heavy metals and trace elements in bed sediments. Recognition of the metal enrichment factors could lead to a better estimation of the dynamics and mass balance of heavy metals and trace elements in contaminated sediments and thereby an improved strategy for wastewater discharge management
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