Comparison of Various Single Chemical Extraction Methods for Predicting the Bioavailability of Arsenic in Paddy Soils

Abstract

The Codex Committee of Contaminants in Food (CCCF) has been discussing a new standard for arsenic (As) in rice since 2010 and a code of practice for the prevention and reduction of As contamination in rice since 2013. Therefore, our current studies focus on setting a maximum level of As in rice and paddy soil by considering bioavailability in the remediation of As contaminated soils. This study aimed to select an appropriate single chemical extractant for evaluating the mobility of As in paddy soil and the bioavailability of As to rice. Nine different extractants, such as deionized water, 0.01 M Ca(NO 3 ) 2 Woo-Ri Go, Seon-Hee Jeong, Anitha Kunhikrishnan, Gyeong-Jin Kim, Ji-Hyock Yoo, Namjun Cho, Kwon-Rae Kim, Kye-Hoon Kim, and Won-Il Kim 465 IntroductionThe Ministry of Environment established the criteria of soil contamination for heavy metal(loid)s in the agricultural fields designated by the Soil Environment Conservation Law in 1996 (MOE, 1996). The Ministry of Food and Drug Safety also established the criteria of 0.2 mg/kg for cadmium (Cd) in polished rice in Korea (KFDA, 2000). Recently, our regulations for agricultural environment including soil, irrigation water, agricultural materials (fertilizer and compost etc.), and agricultural products are being gradually reinforced (KFDA, 2011;MOE, 2010a). The CCCF (Codex Committee of Contaminants in Foods) have been under discussion on the maximum levels for arsenic (As) in polished rice since 2010 (FAO/WHO, 2014).In Korea, the standard method of analyzing heavy metal(loid)s contamination in soils is by aqua regia digestion (MOE, 2010b). This method is acceptable to evaluate the environmental burden of pollutants to the soil and to decide the proper environmental management and human safety. However, this method is not useful for assessing the metal bioavailability to crops. In order to minimize the risk of heavy metal(loid)s to the agricultural environment, crops, livestock, and humans exposed during the agricultural activities, considering bioavailability for the remediation of heavy metal(loid)s is necessary for agro-food safety (Naidu et al., 2003;Heemsbergen et al., 2009;Kim et al., 2009;Salazar et al., 2012;Bolan et al., 2014). Even though the development of analytical methods for measuring the bioavailability of heavy metal(loid)s in agricultural soils was rare in Korea, various assessment techniques were already developed worldwide. Bioavailability of metal(loid)s in agricultural soils was determined mainly by the concentration of metal(loid)s, the species and fractions of a specific metal(loid), and the physico-chemical properties of soils (Ruby et al., 1993;Geebelen et al., 2002;Kim et al., 2012a). Various single and stepwise sequential extraction methods were suggested to estimate the bioavailability of heavy metal(loid)s in agricultural soils. The Soil Environment Conservation Law recommended the use of 0.1 M HCl for cadmium (Cd), lead (Pb), copper (Cu), chromium (Cr), nickel (Ni), and zinc (Zn) and 1.0 M HCl for As to evaluate their bioavailability ...