A multivariate assessment of soil contamination by arsenic in the urban area of Ouro Preto, Brasil

Abstract

A B S T R A C TArsenic (As) is a toxic and carcinogenic element, whose compounds are present in the environment and in biological systems. The most common way of human exposure to As is through consumption of contaminated water, inhalation of gases and ingestion of dust derived from soil. Contamination by As affects millions of people yearly throughout the planet. In the city of Ouro Preto, Brazil, in the neighborhoods of Piedade, Antônio Dias, Padre Faria, Taquaral and Alto da Cruz, 21 soil samples were collected in a 2 km 2 area for the purpose of analyzing their physical properties, chemical composition, mineralogy and the presence of As. Of all samples, 15 presented a predominantly clay texture and 12 of them presented As contents higher than 250 mg.kg -1 . In general, the As contents varied from 6 to 925 mg.kg -1 . Primary or secondary As minerals were not found, which suggests their retention and adsorption by the oxides and hydroxides of Fe, Al and clay minerals. The main minerals found were quartz, muscovite, kaolinite, goethite, hematite, illite and gibbsite. Multivariate techniques (HCA and FA) were applied to assess the spatial distribution of As and its associations. Results show that As is distributed in the North of the studied region, strongly linked to clay fraction, which, in turn, is characterized by the presence of goethite and talc, which are the carriers of As.