Roxarsone and its metabolites in chicken manure significantly enhance the uptake of As species by vegetables

Roxarsone is an organoarsenic feed additive which can be finally degraded to other higher toxic metabolites after excreted by animal. In this work, the uptake of As species by vegetables treated with chicken manure bearing roxarsone and its metabolites was investigated. It was showed that more than 96% of roxarsone added in chicken feed was degraded and converted to arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenate, 4-hydroxyphenylarsonic acid and other unknown As species. Arsenite and arsenate could be found in roots of vegetables but only arsenite transported up to shoots. Chicken manure bearing roxarsone and its metabolites increased 33-175% of arsenite and 28%∼seven times of arsenate in vegetable roots, 68-175% of arsenite in edible vegetable shoots. Arsenite, the most toxic As form, was the major extractable As species in vegetables accounted for 79-98%. The results reflected that toxic element As could be absorbed by vegetables via the way: roxarsone in feed → animal → animal manure → soil → crop and the uptake of As species would be enhanced by using chicken manure bearing roxarsone and its metabolites as organic fertilizer.