Arsenic Levels in Crops Irrigated with Water Containing MSMA

Abstract

Mature plants of tomato(Lycopersicon esculentumMill. ‘Super Sioux’), cucumber(Cucumis sativasL. ‘Early pickling’), and pinto bean(Phaseolus vulgarisL.), in small field plots, were exposed once to sprinkler or furrow irrigation water containing 0.11 kg/ha or 1.12 kg/ha MSMA (monosodium methanearsonate). Concentrations of MSMA in water were about 0.22 ppmw and 2.2 ppmw for the two rates, respectively. Samples of crops and soil were subsequently analyzed for elemental arsenic content by colorimetric and atomic absorption methods. Arsenic residues were higher, compared to controls, only in crops exposed to MSMA applied in sprinkler irrigation. Average arsenic levels were highest in tomatoes exposed to 2.2 ppmw MSMA by sprinkler irrigation, and after 30 and 45 days were 0.26 ppm and 0.35 ppm, respectively. Average arsenic levels in sprinkler-irrigated crops ranged from double to triple the arsenic levels in control (untreated) crops. Atomic absorption was more sensitive than the colorimetric method and could detect smaller differences in arsenic content of samples. The average arsenic residues in soil varied from 1 to 3 ppm, but the differences could not be attributed to treatment with MSMA.