Environmental assessment: contamination of phreatic aquifer in areas impacted by waste from coal processing activities R.B. Binotto a , E.C. Teixeira a, * , J.C.D. Sanchez b , D. Migliavacca a , A.S. Nanni a a Fundac Ëa Äo Estadual de Protec Ëa Äo Ambiental, Rua Carlos Chagas 55/707, Porto Alegre, RS, 90.030020, Brazil b Fundac Ëa Äo de Cie Ãncia e Tecnologia, Porto Alegre, RS, Brazil Received 22 February 1999; received in revised form 12 October 1999; accepted 9 December 1999 Abstract The objective of the present work was to evaluate the degree of contamination of groundwater in areas under in¯uence of inadequate disposal of residues from coal-processing activities. Charqueadas and Sa Äo Jero à nimo Counties were selected for the study. The contamination of groundwater from the phreatic aquifer was evaluated in a sequence of steps: initially, the target area was selected; then, the piezometers were installed and groundwater was sampled. The location of piezometers was based on the results obtained from the mapping of pollution sources, geophysical and hydrogeological studies. The results showed that the groundwater (phreatic aquifer) from the region studied is in¯uenced, in variables degrees of intensity, by the type and characteristics of residues, the lithological pro®le of the site and the distance from the pollution sources. Physical and chemical characterization revealed that coal waste in¯uenced more signi®cantly groundwater contamination, evidenced by acidic pH values, as well as high values of conductivity, total dissolved solids (TDS), sulfates, ferrous iron and metals (Ni, Fe, Co, Cr and Mn). The statistical analysis applied to the variables studied gave a General Groundwater Index for each well. By the application of this index, it was possible to highlight the kind of residues and variables that are affecting the groundwater quality. q 2000 Elsevier Science Ltd. All rights reserved. Keywords: Groundwater; Coal waste; Contamination; Water quality 1. Introduction Southern Brazil is known by the occurrence and utiliza- tion of coal in several industries and in the generation of energy. In the Rio Grande do Sul State (RS) the largest Brazilian coal reserves are found and account for 60% of the national total. Increased coal production is expected, as the generation of hydro-electricity tends to decrease and to enable a more signi®cant exploration of coal as a mineral resource, especially in the Rio Grande do Sul State. A larger production implies a signi®cant increase in the steps involved in coal-processing activities. These activities generate large volumes of solid residues whose inadequate disposal can cause severe environmental problems, of irreversible character if not conveniently planned, with the adequate adoption of processes of environmental control. From these problems, those related to the groundwater contamination in areas under in¯uence of such residues acquire extreme importance due to the possibility of utilization of such aquifers as supplies of drinkable water, in view of the increasing degradation of surface waters resources. In the Rio Grande do Sul State, the Baixo Jacuõ  Region has a large concentration of coal waste and ash deposits in ¯ooding zones and without vegetable coverage [1±3]. The location of most areas currently used for the disposal of residues from coal-processing activities existing in that region (especially mining operations and power stations) used to be based solely on an economic decision, not taking into account the negative impacts that such deposits could cause to the environment. The intensity of the environmental problems in the Baixo Jacuõ  Region due to the chaotic occupation of sites by coal- processing residues makes clear the need for evaluation of the in¯uence of such materials in the contamination of groundwater be evaluated. In view of this, the present work aims to assess the extent of groundwater (phreatic aquifer) contamination in Charqueadas and Sa Äo Jero Ãnimo counties, as a function of the inadequate disposal of coal waste and ash. The small availability of data referring to the quality of groundwater in coal regions, the need for the development of technical and legal criteria that should regulate the disposal of waste from coal preparation and Fuel 79 (2000) 1547±1560 0016-2361/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved. PII: S0016-2361(99)00291-4 www.elsevier.com/locate/fuel * Corresponding author. Tel.: 1 51-225-1588; fax: 1 51-212-4151. E-mail address: gerpro.pesquisa@fepam.rs.gov.br (E.C. Teixeira).