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

Lindane production is very ineffective since, for each ton of lindane obtained, between 6 and 10 tons of hexachlorocy-clohexane (HCH) isomers and other toxic compounds are produced. Due to the disposal of these residues, contami-nated zones still exist, and many dumpsites are close to rivers and water reservoirs. The current study examines consequences of irrigating pea, maize, and alfalfa, with water containing different HCH concentrations on the accumu-lation 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 mu g L-1 (the maximum threshold allowed for human consumption), 2.5 mu g L-1, 5 mu g L-1, and 20 mu g L-1. Results showed that both surface and overhead irriga-tion with these HCH concentrations did not cause any toxicity effects on the considered crops. However, under over-head irrigation with HCH concentrations higher than 5 mu gL-1HCH is absorbed by maize leaves and its concentration in plant biomass surpassed the EU maximum residue level of 10 mu g kg-1. In the case of fodder maize, an HCH concen-tration of 0.84 mu g L-1 in irrigation water produced an HCH concentration in plant above 20 mu g kg-1 dry matter, 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 mu g L-1) under surface irrigation, but concentration was below the EU maximum residue level. In conclusion, in overhead irrigated systems, water with HCH concentra-tions below 5 mu g 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.