Abstract: DETERMINATION OF CHEMICAL SPECIES OF ARSENIC AND TRACE ELEMENTS IN ENVIRONMENTAL WATER IN THE BAYANNAOERMENG BY NAAYang Ruiying Zhu Xuping(Institute of High Energy Physics,Laboratory of Nuclear Analysis Technigues,the Chinese Acadmy of Sciences,P.O.Box 2732,Beijing 100080)ABSTRACTA method for determining As(Ⅲ) and As(Ⅴ) by NAA after extraction and coprecipitation has been proposed. The total inorganic arsenic targets are prepared by coprecipitation with Fe(OH)3. The As(Ⅴ) targets are prepared by coprecipitation of the aqueous phases after extraction. The As(Ⅲ) targets are prepared by coprecipitation after extraction and backextraction. The targets are irradiated and analysed by NAA. The accuracy of the procedure is checked by analysing NBSSRM 1643b and Chinese standard reference materials (GBW),the obtained results agree quite well with literature values. The lower limit of the method is 0.02 μg/L.Key words Neutron activation analysis (NAA) Arsenic species