Effects of residual disinfectant on soil and lettuce crop irrigated with chlorinated water

The accidental or continuous release of residual chlorine in water reclaimed for irrigational purposes could compromise the crop yield and increase the load of toxic organo-halogenated compounds, posing additional risks for environment and human health. This studywas aimed at assessing the consequences of using chlorinatedwater for irrigating lettuce crops grown in pots with two different types of soil. The results show that the accumulation of extractable organo-halogenated compounds (EOX) in soil, roots and leaves is directly related to the chlorine concentration in the irrigation water. The accumulation of EOX in sandy soils is not significant, while it reached up to 300% of the control in the silty-clay soil, demonstrating that the phenomenon is linked to the organicmatter content in the soil. The accumulation of EOX in the soil appears to play a significant role in subsequent bioaccumulation in cultures irrigated with tap water (long term memory effect). Chloramines also demonstrated to have similar impacts as the free chlorine from hypochlorite. The consistent bioaccumulation of 400-700 ?gCl kg-1 of EOX in the leaves of crops irrigated with just 0.2 mgCl L-1 of residual chlorine, as compared to levels below the detection limit of 75 ?gCl kg-1 in the control crops, evidences the potential impact on food chain and human health.