A preliminary investigation for Cu distribution in paddy soil and rice plants in contaminated paddy fields

Abstract

The soil sample of a paddy field was found to be contaminated by copper (Cu). The application of wastewater as the nitrogen fertilizer was identified as the cause in this study. The concentration of Cu in soil and rice plants was therefore explored. The paddy soil characteristics indicated a strong anaerobic environment. The Cu concentration in topsoil was 123 ± 24 mg kg−1. The Community Bureau of Reference (BCR)’s fractionation of Cu from high to low was residual fraction (62.1%) > organically bounded and sulfide-bounded fractions (24.2%) > iron oxide and manganese oxide fraction (8.8%) > acid-soluble fractions (4.8%). The concentration of Cu in rice organs was the highest in the roots, followed by the straw, grain, and husk. The correlation of Cu in rice straws with every fractionation of Cu in soil was strong. However, the weak correlation between Cu in rice grains and soil was found. The result of Cu mass balance in the soil–rice cultivation system showed that less than 0.1% of Cu was translocated to rice plant. The average Cu intake through rice grain consumption (621 μg day−1) indicated the Cu supply to human body basic need without any potential negative health impacts to consumer. However, this level of Cu may cause toxicity to rice growth and productivity. Soil replacement may be more appropriate than soil treatment in this study. In addition, agricultural practices should be managed to prevent further contamination and promote more aerobic conditions.