Remediation of organic halogen- contaminated wetland soils using biochar

Abstract

Organochlorine waste from papermaking has polluted soils worldwide, and the addition of biochar will improve polluted soils in a variety of scenarios. A field study (2014 to 2016) was conducted to investigate the application of wheat (Triticum aestivum L.) straw biochar (0, 20, 40, 60 Mg ha−1) to organic halogen-contaminated saline-alkali soil. The addition of biochar reduced the concentrations of adsorbable organic halogens (AOX) in the soil and extractable organic halogens (EOX) in reeds (Phragmites communis) by 9–94% and 14%–51%, respectively, and subsequently increased reed biomass by 1%–25%; these changes were related to the changes in different soil properties. Soil properties, such as the organic functional groups, surface properties, and pH, were improved following the addition of biochar, and some changes were maintained at heightened levels over time. The activity of urease, alkaline phosphatase, and sucrase enzymes in soil increased by 14 to 57%, 2 to 147%, and 1 to 75% as a function of increasing biochar amendment, respectively, while that of dehydrogenase decreased by 13% to 60%, which may have aided in the acceleration of AOX decomposition. The diversity of the bacterial community also increased due to biochar application, and is likely a key indicator of halogen degradation. The addition of biochar likely decreased the bioavailability of organic halogens by improving the function and structure of the microbial community, reducing their transfer to reeds grown in papermaking organochlorine-contaminated soils. Biochar may play an important role in reducing environmental contamination by organic halogens.