Distribution study of inorganic arsenic (III) and (V) species in soil and their mobility in the area of Baia-Mare, Romania

摘要

Baia-Mare industrial site in NW Romania was investigated to assess the distribution, speciation and mobility of inorganic arsenic species in soil. Contents and fractions of As(III), As(V) and total As leachable in water, 1 M HCl and 10 M HCl were determined in soil by single extraction. Total arsenic content in the selected sample, determined after a matrix modification with Mg(NO3)(2) was in the range 10-1725 mu g g(-1). The contents (mu g g(-1)) of leachable As3+ (As5+) species by single extraction were: 0.1-70 (0.8-950) in water, 0.2-90 (1.6-1200) in 1 M HCl and 0.8-100 (8-1500) in 10 M HCl, showing that arsenic (V) species represented more than 90% of the total. Leaching tests indicated a high availability of arsenic in water, although poorly reactive phases were encountered as well. Compared to the total arsenic in soil, fractions of 9-34% were leachable in water, 39-80% in 1 M HCl and 77-94% in 10 M HCl. Contamination was higher at the surface than at depth and decreased with the distance from the pollutant source. Centres for pyrometallurgical processing of ores are mainly responsible for pollution with water soluble species, while centres for ores concentration for pollution with poorly reactive arsenic species soluble in 10 M HCl and Mg(NO3)(2). According to the sequential extraction data, soils in the area could be divided into three categories according to its maximum mobility in water, 1 M HCl and 10 M HCl. Good precision (RSD 7.5-17.6%) and recovery degree (101 +/- 3%) were achieved for arsenic determination in five certified soils (n = 5).