Abstract
The rapid increase of reclaimed water irrigation on agricultural soils requires investigation of its impact on soil health. In this study, a simulation experiment for various lengths of long-term reclaimed water irrigation time (98, 196 and 236 years, respectively) was conducted in the southeast suburb of Beijing, China. Unirrigated soil served as the control. The environmental behavior of seven trace elements (As, Cd, Cr, Cu, Hg, Pb and Zn) at different soil depths in 0–600 cm profiles was analyzed. Results showed that the 0–30 and 200–300 cm soil layers were more likely to accumulate trace elements under long-term reclaimed water irrigation, although the accumulation in the 0–600 cm profiles was not particularly obvious. Correlation analysis showed that the trace element concentrations and distribution were significantly related to clay fraction and organic matters (OM), whereas they were not related to redox potential (Eh). The potential ecological risk assessment showed that the long-term reclaimed water irrigation did not result in a significantly increased ecological risk. However, Cd and Hg were identified as the metals with the highest potential ecological risk in the study area and the trace element contents in the top 0–30 cm soil layer should be carefully monitored. Future studies are required to clarify the environmental risks of trace elements under long-term reclaimed water irrigation as they might slowly accumulate in soil with time.
Highlights
Rapid economic development and sharp increases in population have greatly stimulated water consumption in industrial, agricultural and domestic use and aggravated the shortage of fresh water resources
At 300–600 cm depth, the contents of Cd, Cu, Hg and Pb increased by 0.4%, 4%, 5% and 2%, respectively and the As, Cr, Zn contents decreased by 0.1%, 2% and According to the change in trace element contents in soil profiles after long-term reclaimed water irrigation, the top 30 cm and 200–300 cm soil layers were more likely to accumulate trace elements especially As, Cu and Hg in the study area, which might be explained by the higher clay and organic matters (OM)
This paper studied the environmental behavior of As, Cd, Cr, Cu, Hg, Pb and Zn in soil profiles of the study area under long-term reclaimed water irrigation and the potential ecological risk
Summary
Rapid economic development and sharp increases in population have greatly stimulated water consumption in industrial, agricultural and domestic use and aggravated the shortage of fresh water resources. The increase in water consumption has exacerbated the volume of sewage discharge. The use of reclaimed water can reduce the volume of sewage discharge and alleviate the pressure of demand for fresh water resources [1]. Use of reclaimed water for irrigation has been commonly adopted because of several advantages, such as increased utilization of water resources, alleviation of pressure on fresh water sources, nitrogen and phosphorus nutrient recovery to crops, fertilizer use reduction and decreased disposal costs [3,4,5]. On the other hand, unregulated irrigation using reclaimed water over many years might lead to the accumulation of toxic and harmful substances, such as heavy metals
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