Effects of low-molecular-weight organic acids on the speciation of Pb in purple soil and soil solution

Abstract

Lead (Pb) in purple soil was selected as the research target, using one-step extraction method with 0.01 mol·L-1 sodium nitrate as the background electrolyte to study the release effect of citric acid (CA), tartaric acid (TA) and acetic acid (AC) with different concentrations. Sequential extraction and geochemical model (Visual Minteq v3.0) were applied to analyze and predict the speciation of Pb in soil solid phase and soil solution phase. Then the environmental implications and risks of low-molecule weight organic acid (LMWOA) on soil Pb were analyzed. The results indicated that all three types of LMWOA increased the desorption capacity of Pb in purple soil, and the effect followed the descending order of CA>TA>AC. After the action of LMWOAs, the exchangeable Pb increased; the carbonate-bound Pb and Fe-Mn oxide bound Pb dropped in soil solid phase. Organic bound Pb was the main speciation in soil solution phase, accounting for 45.16%-75.05%. The following speciation of Pb in soil solution was free Pb, accounting for 22.71%-50.25%. For CA and TA treatments, free Pb ions and inorganic bound Pb in soil solution increased with increasing LMWOAs concentration, while organic bound Pb suffered a decrease in this process. An opposite trend for AC treatment was observed compared with CA and TA treatments. Overall, LMWOAs boosted the bioavailability of Pb in purple soil and had a potential risk to contaminate underground water. Among the three LMWOAs in this study, CA had the largest potential to activate soil Pb.

Keywords

Environmental risk; Lead; Low molecule weight organic acid (LMWOA); Metal speciation; Purple soil

Published in

Huan Jing Ke Xue
2016, volume: 37, pages: 1523-1530
Publisher: Science Press

SLU Authors

• Jiang, Tao

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • Southwest University

UKÄ Subject classification

Environmental Sciences
Soil Science

Publication identifier

• DOI: https://doi.org/10.13227/j.hjkx.2016.04.043

Permanent link to this page (URI)

https://res.slu.se/id/publ/130359