Effects of irrigation with HCH-contaminated water on crop performance and HCH accumulation in plant and soil

Abstract

Lindane production is very ineffective since, for each ton of lindane obtained, between 6 and 10 tons of hexachlorocyclohexane (HCH) isomers and other toxic compounds are produced. Due to the disposal of these residues, contaminated zones still exist, and many dumpsites are close to rivers and water reservoirs. The current study examines the consequences of irrigating pea, maize, and alfalfa, with water containing different HCH concentrations on the accumulation of HCH in plant material and soils. The experiments were conducted on pots under controlled conditions using drinking water (as reference) and water with several HCH concentrations: 0.5 μg L^-1 (the maximum threshold allowed for human consumption), 2.5 μg L^-1, 5 μg L^-1, and 20 μg L^-1. Results showed that both surface and overhead irrigation with these HCH concentrations did not cause any toxicity effects on the considered crops. However, under overhead irrigation with HCH concentrations higher than 5 μgL^-1 HCH is absorbed by maize leaves and its concentration in plant biomass surpassed the EU maximum residue level of 10 μg kg^-1. In the case of fodder maize, an HCH concentration of 0.84 μg L^-1 in irrigation water produced an HCH concentration in plant above 20 μg kg^-1 dry matter, the upper threshold established in the Spanish legislation, that limits the use for animal feeding. In the case of alfalfa, HCH was detected in treatments with the highest HCH concentration (13 μg L^-1) under surface irrigation, but concentration was below the EU maximum residue level. In conclusion, in overhead irrigated systems, water with HCH concentrations below 5 μg L^-1 does not produce HCH accumulation in pea and maize grain above the maximum residue levels; however, for fodder maize, the HCH concentration in irrigation water should be controlled to avoid HCH accumulation in plants above the limit for animal feeding.

Keywords: Environmental risk; Foliar uptake; Hexachlorocyclohexane; Organochlorines; Overhead irrigation; Surface irrigation.