Tetracycline effects on arsenate reduction in agricultural soils under different soil water contents

The application of manure in agricultural soil increases the risk of co-contamination of antibiotics and heavy metals, posing significant risks to both environment and human health. However, related research about such co-contamination remains limited. This study investigated the effect of tetracycline addition on arsenate reduction in agricultural soils under varying soil water contents. Soil samples were incubated for 30 days at 50 % field capacity, 75 % field capacity and flooded conditions. Tetracycline addition (20 μg g^-1) increased the As(III) concentration by 59 % and 779 % under 50 % and 75 % field capacity after 30-d incubation, respectively, compared to that without tetracycline. Tetracycline accelerated the As(V) reduction but did not affect As(III) concentration under flooded conditions. The enhanced As(V) reduction with the presence of tetracycline could be attributed to decreased soil redox potential and increased relative abundance of arsenate-reducing bacteria (such as Comamonadaceae, Bacillaceae). Such effects were correlated with soil water content and were greatest at 75 % field capacity. The significant increase in As(III), which is more toxic and mobile than As(V), implies a substantial elevation in environmental toxicity and potential risks for bioaccumulation in agricultural products. These findings highlight the role of tetracycline in arsenic biogeochemical processes during soil wet-dry cycles and its potential risks to agricultural product safety via As(III) bioaccumulation.