Safety risk of using asomate to reduce acid in Citrus production

Abstract

Asomate, an organo-arsenic fungicide, was historically used on various crops. Recently, a type of pesticides capable of improving the sweet taste of Citrus fruit, was occasionally used to enhance the sweetness, taste, and accelerate the ripening of citrus fruits. The primary ingredient of the pesticides was confirmed to be asomate by elemental analysis, inductively coupled plasma mass spectrometry and high-resolution mass spectrometry analysis. To assess potential risks to Citrus quality and safety, field experiments were conducted on Harumi tangor by spraying the tree with the pesticide as the treated group and clean water as control. The effects of asomate on fruit quality and residue levels in fruits, leaves, and soil were investigated. Results showed that asomate decreased organic acid content in Citrus fruits by 60.5 %, while the sugar-acid and solid-acid ratios increased from 14.26 to 30.88, and from 16.15 to 35.50, respectively, implying for fruit quality with sweeter taste. Compared to the control, spraying of asomate has caused significant arsenic residues in the pesticide treated Citrus fruits (0.042 mg/kg vs 0.015 mg/kg), leaves (2.56 mg/kg vs 0.082 mg/kg), and soil (8.89 mg/kg vs 8.33 mg/kg), posing hazards to human health and the natural environment.