Determination of Arsenic species in Rice (Case study vicinage of quarry excavation area: Arngnoy Village Sungthong District, Vientiane capital)

Bounphak Lobriayao, Nakhonekham Phichit, Noynita Xaiyabountha Department of Environmental Science, Faculty of Environmental Science, National University of Laos, P.O Box 7322, E-mail: Dicaprio439@gmail.com, Tel & Fax: +856-21-770561

Abstract

Rice is the staple food of people in Asian countries especially in Laos, where it is a carbohydrate stuff which plays an important role for source of energy to support human beings.  Arsenic (As) is a heavy metal of which naturally occurring; it can be found in soil, rocks or in natural water sources, and caused by human activities such as mining activities, the used of agro-chemicals (pesticides, herbicide, etc…) in agriculture.Therefore, it is possible to deposite and contaminate in the environment such as the paddy soil and the irrigation; afterward it can initiate the arsenic residues in the agricultural productions that harvesting from the contaminated area, which is the rice grain. Furthermore, the arsenic residue can cause the health impact to those who eating the contaminated rice.

            Our study concist of two mian objectives: 1.) Study the source of arsenic in Ban Ang Noi, Sangthong District, Vientiane Capital, and 2.) Determination of Arsenic species in Rice grian using HPLC-ICP-MS (High-Performance Liquid Chromatography-Inductively Couppled Plasma Mass spectrometry).

            According to the analysis results of arsenic contamination in the 3 types of rice samples revealed that: in the HSV sample, the total amount of arsenic was 0.11 mg/kg, the total inorganic arsenic (iAs) was 0.09 mg/kg which included the amount of inorganic arsenic As^V was 0.0178 mg/kg, the inorganic arsenic As^III was 0.0703 mg/kg; the total arsenic in the TDK8 sample was 0.19 mg/kg, the (iAs) was 0.10 mg/kg, and the amount of arsenic As^V was 0.0126 mg/kg, the amount of arsenic As^III was 0.0834 mg/kg; the total arsenic in the Composite rice was 0.14 mg/kg, the (iAs) was 0.08 mg/kg, the As^V and As^III were 0.006 mg/kg and 0.0771 mg/kg, respectively.

            In conclusion, arsenic residue contaminated in all three rice samples, but the residue of total arsenic and inorganic arsenic (iAs) did not exceed the maximum permissible limit of the international standard or CODEX (CODEX ALIMENTARIUS COMMISSION (2017)) which is 0.3 and 0.2 mg/kg, respectively.