Abstract
This study explored the stratigraphic distribution and soil/shallow aquifer characteristics surrounding a chromium ore processing residue (COPR) dumpsite at a former chemical factory in China. Total Cr levels in top soils (5–10 cm) nearby the COPR dumpsite were in the range of 8571.4–10711.4 mg/kg. Shallow aquifers (1–6 m) nearby the COPR dumpsite showed a maximum total Cr level of 9756.7 mg/kg. The concentrations of Cr(VI) in groundwater nearby the COPR dumpsite were 766.9–1347.5 mg/L. These results display that the top soils, shallow aquifers, and groundwater of the study site are severely polluted by Cr(VI). Then, three aquifers (silt, clay, and silty clay), respectively, collected from the depth of 1.4–2.4 m, 2.4–4.8 m, and 4.8–11.00 m were first used to evaluate the adsorption characteristics and transport behavior of Cr(VI) in shallow aquifers by both batch and column experiments. The adsorption of Cr(VI) on tested aquifers was well described by pseudo-second-order equation and Freundlich model. The adsorption capacities of Cr(VI) on three aquifers followed the order: clay > silty clay > silt. The kinetics proved that Cr(VI) is not easily adsorbed by the aquifer mediums but transports with groundwater. Thermodynamics indicated that Cr(VI) adsorption on tested aquifers was feasible, spontaneous, and endothermic. Cr(VI) adsorption on tested aquifers decreased with increasing pH. Furthermore, the transport of Cr(VI) in adsorption columns followed the sequence of clay < silty clay < silt. Desorption column experiments infer that the Cr(VI) adsorbed on aquifers will desorb and release into groundwater in the case of rainwater leaching. Therefore, a proper treatment of the COPR and a comprehensive management of soils are vital to prevent groundwater pollution.
Highlights
Chromium (Cr) is widely used in various chemical industries, such as electroplating, steelmaking, metallurgy, leather tanning, pigment manufacturing, wood preservative, and textile dyeing [1]
Cr(VI) exposure could cause skin irritation, respiratory cancer, and kidney damage [5]. e contamination of soils and groundwater with Cr(VI) has posed a chronic public health and environmental threat due to its high solubility, mobility, toxicity, and mutagenic and carcinogenic properties [6]. e drinking water standard for total Cr of US EPA is 100 μg/L [7]. e permitted concentration of Cr(VI) in drinking water based on the World Health Organization (WHO) guideline is 0.05 mg/L [8]
It was reported that only 100 million tons of Chromium ore processing residue (COPR) were treated in China Journal of Chemistry from 2005 to 2010, yet 300 million tons of COPR still harm the environment [11]
Summary
Chromium (Cr) is widely used in various chemical industries, such as electroplating, steelmaking, metallurgy, leather tanning, pigment manufacturing, wood preservative, and textile dyeing [1]. Many studies reported about metal adsorption in soil, but fewer studies combine adsorption batch experiments with adsorption/desorption column experiments to investigate the adsorption characteristics and transport behavior of heavy metal in soil and its risk to groundwater. We measured the concentrations of Cr(VI) in top soils (5–10 cm), shallow aquifers and groundwater nearby the COPR dumpsite and explored the stratigraphic distribution and soil characteristics of the study site. E objectives of the present work were to (1) evaluate the concentrations of Cr(VI) in top soils, shallow aquifers, and groundwater nearby the COPR dumpsite, (2) investigate the adsorption characteristics of Cr(VI) in different aquifers and gain insight into the adsorption mechanism of Cr(VI) in these aquifers, and (3) reveal the adsorption-desorption behaviors of Cr(VI) in aquifers by dynamic column studies. E results of our study can be used to predict the fate and transport behavior of Cr(VI) in polluted soils and aquifers, which will be helpful to value the risk of contaminant migration and to establish effective remediation plans for contaminated soils
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
