Arsenic Accumulation And Distribution In Rice And Fine Particulate Matter(PM_2.5)

Arsenic is a ubiquitous pollutant, and it is non-degradable, highly mobile and easily bio-accumulated in environment. It was defined as “group 1 carcinogen”. Arsenic is related to a series of health problems, such as skin cancer, diabetes, and cardiovascular disease. Food and potable water were the primary sources of human arsenic exposure. As the stable food crop in China, rice has been thought to be the largest contributor（about 60%） of inorganic arsenic ingestion through food consumption. In recent years, atmospheric contamination was increasingly serious. Inhaled exposure was defined as an important source of arsenic exposure, followed to potable water and food. Most of atmospheric arsenic exists in fine airborne particles(PM_2.5), which can get into the pulmonary alveoli, with a great risk to human. So it is crucial to know arsenic content and distribution in rice and fine airborne particles.In this study, rice and PM_2.5 were studied as the main object. We studied arsenic concentrations and distribution in rice planted in Nansi Lake area-a main rice producing base in Shandong Province. The sources of arsenic in rice were analyzed and the potential long-time health risk in a low dose was assessed. Furthermore, arsenic concentrations and distributions in PM_2.5 were analyzed, and its potential cancer risk was assessed. The major results of this paper were as follows:1. The arsenic concentrations of polished rice from Nansi Lake was below national standards. However, inorganic arsenic concentrations in hull and bran exceeded the limited value of food-safety standard. Inorganic arsenic（As（III）+As（V）） were the major components in hull, bran, polished rice. Dimethylarsinic acid（DMA） was founded in bran and polished rice only. However, DMA and monomethylarsonic acid（MMA） were founded in hull. The transport Factor（TF） of arsenic from root to leaf were calculated. The transport efficiencies were as followed: stem-leaf > root-stem. Arsenic concentrations of paddy soil and irrigation water from six typical rice planting area SZ, QH, XZ, WS, JX and TFs in Nansi Lake area were 5.5⁹.9 μg/L and 6.3¹3.6 mg/kg, respectively. The results indicated that the plant environment in Nansi Lake was a low arsenic exposure area. The sources of arsenic in rice were analyzed in this study. The results showed that irrigation water, soil, fertilizer and herbicide were the main influence factors on arsenic concentration of rice grain. Arsenic in polished rice was affected by fertilizer and herbicide. Hazard quotients（HQ） were used to evaluate health risk of polished rice. The results showed that its risk remained small.2. In this study, arsenic species were extracted from the PM_2.5 filters using 1% nitric acid（HNO3） solution via microwave assisted extraction, and determined by HPLC–ICP–MS. All of the four arsenic species were completely separated within 10 min. The detection limits for As（III）, DMA, MMA, As（V） were in the range of 0.6¹.0 μg/L. The RSD（relative standard deviation） of As（III）, DMA, MMA, As（V） were 1.30%、1.30%、1.00%、0.79%, respectively. Compared with total arsenic detected by atomic fluorescence spectrophotometer, the recoveries of HPLC-ICP-MS were from 91.8% to 100.5%. On the basis of the arsenic speciation analysis method, arsenic concentration and species in PM_2.5 in summer and winter of Jinan city were determined. The results showed that arsenic concentrations of PM_2.5 in winter were almost two times higher than in summer. The major arsenic speciation in PM_2.5 samples was As（V）, only a small amount As（III） was founded in part samples in winter. A positive correlation was founded between the PM_2.5 levels and arsenic concentrations. In Jinan, the cancer risk of inorganic arsenic in PM_2.5 should be concerned.