Sustainable removal of soil arsenic by naturally-formed iron oxides on plastic tubes

Arsenic (As) pollution in paddy fields is a major threat to rice safety. Existing As remediation techniques are costly, require external chemical addition and degrade soil properties. Here, we report the use of plastic tubes as a recyclable tool to precisely extract As from contaminated soils. Following insertion into flooded paddy soils, polyethylene tube walls were covered by thin but massive Fe coatings of 76.9-367 mg Fe m? 2 in 2 weeks, which adsorbed significant amounts of As. The formation of tube-wall Fe oxides was driven by local Fe-oxidizing bacteria with oxygen produced by oxygenic phototrophs (e.g., Cyanobacteria) or diffused from air through the tube wall. The tubes with As-bound Fe oxides can be easily separated from soil and then washed and reused. We tested the As removal efficiency in a pot experiment to remove As from -20 cm depth/40 kg soils in a 2-year experiment and achieved an overall removal efficiency of 152 mg As m(-2) soil year(-1), comparable to phytor-emediation with the As hyperaccumulator Pteris vittata. The cost of Fe hooks was estimated at 8325 RMB ha(-1) year(-1), and the profit of growing rice (around 16080 RMB ha(-1) year(-1) can be still maintained. The As accu-mulated in rice tissues was markedly decreased in the treatment (> 11.1 %). This work provides a low-cost and sustainable soil remediation method for the targeted removal of As from soils and a useful tool for the study and management of the biogeochemical Fe cycle in paddy soils.

Automated summary

This study presents a method of extracting arsenic from contaminated soil using plastic tubes, which are covered with iron oxides that can easily be separated from the soil, providing a low-cost and sustainable soil remediation technique.