Mapping of arsenic pollution with reference to paddy cultivation in the middle Indo-Gangetic Plains

A detailed field study was carried out to monitor (i) the arsenic contents in irrigation groundwater and paddy soil and (ii) the accumulation of arsenic in the roots and grains of different paddy varieties grown in the arsenic-contaminated middle Indo-Gangetic Plains of Northern India. Results showed the highest arsenic contamination in the irrigation groundwater (312 μg l(-1)) and in paddy soil (35 mg kg(-1)) values that were significantly exceeded the recommended threshold values of 100 μg l(-1) (EU) and 20 mg kg(-1) (FAO), respectively. The paddy soil arsenic content ranged from 3 to 35 mg kg(-1) with a mean value of 15 mg kg(-1). The soil arsenic content was found to be influenced by the soil texture, carbon, macronutrients, phosphorus, sulfur, hydrolases, and oxidoreductases properties of the paddy soils as revealed in the principal component analyses. Higher root accumulation (>10 mg kg(-1)) of arsenic was observed in 6 of the 17 paddy varieties grown in the study area. The range of arsenic content accumulated in the paddy roots was 4.1 to 16.2 mg kg(-1) dry weight (dw) and in the grains 0.179 to 0.932 mg kg(-1) dw. Out of 17 paddy varieties, eight had 0 > .55 mg kg(-1) grain arsenic content and were found unsafe for subsistence maximum daily tolerable dietary intake (MTDI) by human beings according to the regulatory standards.