Arsenic in Untreated and Treated Manure: Sources, Biotransformation, and Environmental Risk in Application on Soils: A Review

Abstract

Arsenic (As) is an environmental toxicant that poses toxic effects to public health throughout the world. Arsenic speciation in the environment is driven by biological processes that determine As fate, mobility, and toxicity in the environment. However, recent advances in the livestock industry, particularly in pigs, have accelerated the application of As to promote growth, and most of the As is excreted from the manure. The application of As-contaminated manure in agriculture can cause environmental toxicity. The present review focuses on As sources, fate, biotransformation, and environmental risk in animal manure and its application. The main source of As in manure is feed additives. This review suggests that As is present at high concentrations in untreated manure, and this could pose threats to the environment in general and to public health in particular. Composting and digestion could be effective strategies to treat As-contaminated manure. Arsenic-transformed/speciation in manure occurs through a methylation process driven by the arsM gene. The application of As-treated manure in soil could improve soil quality with no potential environmental risk. This review could be helpful for environmental policy-making and in regard to strategies for the management of As-contaminated manure.