Influence of water chemistry on colloid-size Cu-based pesticides particles: A case of Cu(OH)(2) commercial fungicide/bactericide

The intensive, widespread, and ever-increasing applications of Cu-based pesticides in agriculture could potentially increase environmental exposures via different routes. Unlike ionic/bulk forms, the fate, transport, and toxicity of colloid-size Cu-based pesticides are not well studied. This paper provides evaluation outcomes of granule and dispersion characterizations, stability, and dissolution of colloid-size particles of Cu(OH)(2) commercial pesticide product at a range of water chemistry. The evaluated product contained about 35% weight of metallic Cu equivalent and Cu(OH)(2) particles with sizes < 1 mu m of which a fraction of nanoscale particles exist. The presence of Ca2+ at ionic strengths of >0.01 M and 0.001-0.2 M significantly influenced (p < 0.001) particle size (PS) and zeta-potential values, respectively at all investigated pH values. Cu dissolution at pH 5.5 was significant (p < 0.001) and exceeded Cu dissolutions at pH 7.0 by 87-90% and at pH 8.5 by 87-95% in all dispersions. The order of Cu dissolution was pH 5.5 > pH 7.0 > pH 8.5 in all dispersions. Cu dissolution was relatively reduced by 53% by increasing HA from 0 to 5 mg L-1 and enhanced by 55% by increasing HA from 5 to 15 mg L-1 , however, the overall Cu dissolution was decreased by 27% by increasing HA from 0 to 15 mg L-1. Thus, HAs reduced the dissolution of Cu at pH < 7. The findings provide an insight into how water chemistry influences the fate and transport of colloid-size Cu-based pesticides particles. (C) 2019 Elsevier Ltd. All rights reserved.