RESEARCH ARTICLE Abandoned coal mining sites: using ecotoxicological tests to support an industrial organic sludge amendment Claudete G. Chiochetta & Marilice R. Radetski & Albertina X. R. Corrêa & Vinícius Tischer & Erasmo N. Tiepo & Claudemir M. Radetski Received: 19 August 2012 / Accepted: 16 October 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract The different stages involved in coal mining- related activities result in a degraded landscape and sites associated with large amounts of dumped waste material. Remediation of these contaminated soils can be carried out by application of industrial organic sludge if the concerns regarding the potential negative environmental impacts of this experimental practice are properly addressed. In this context, the objective of this study was to use ecotoxicological tests to determine the quantity of organic industrial sludge that is required as a soil amendment to restore soil production while avoiding environmental impact. Chemical analysis of the solids (industrial sludge and soil) and their leachates was carried out as well as a battery of ecotoxicity tests on enzymes (hydrolytic activity), bacteria, algae, daphnids, earthworms, and higher plants, according to standardized methodologies. Solid and leachate samples of coal-contaminated soil were more toxic than those of industrial sludge towards enzyme activity, bacteria, algae, daphnids, and earthworms. In the case of the higher plants (lettuce, corn, wild cabbage, and Surinam cherry) the industrial sludge was more toxic than the coal- contaminated soil, and a soil/sludge mixture (66:34 % dry weight basis) had a stimulatory effect on the Surinam cherry biomass. The ecotoxicological assessment of the coal- contaminated soil remediation using sludge as an amendment is very important to determine application rates that could promote a stimulatory effect on agronomic species without negatively affecting the environment. Keywords Coal mining sites . Acid mine drainage . Soil remediation . Biotests . Industrial sludge Introduction From the energy supply point of view, coal mining is an important economic activity in developing countries, but exploitation of this resource may originate several environ- mental impacts. The different stages involved in coal mining (i.e., extraction, processing-concentration, coal use, and mine deactivation) can result in a degraded landscape, asso- ciated with large amounts of dumped waste material, depending on the technologies adopted during the mining process and the chemical composition of the coal (Pompêo et al. 2004; Juwarkar and Jambhulkar, 2008). It is well established that most coal mining sites have reduced local agroforest productivity, since the physical, chemical, and biological properties of soils dumped in waste areas after coal mining are altered (Lunardi-Neto et al. 2008; Kopezinski 2000). Furthermore, the surrounding ecosystems are disturbed, causing an ecological imbalance (Juwarkar and Jambhulkar 2008; McAllister and Milioli 2000). The coal found in the “Carboniferous basin” of Santa Catarina State (south of Brazil) is a mixture of schistic, pyritic, and carbonaceous materials where only 27 % (dry mass basis) has energetic value (Santa Catarina State 2004). Thus, 73 % (dry mass basis) of the coal exploited is wasted and has been dumped on surface soil, originating over 1,000 abandoned sites where pyrite is oxidized to form the well- documented acid mine drainage (AMD), considered the most serious environmental pollution problem in the mining industry, which is currently a global problem (Santa Catarina State, 2004; Lattuada et al. 2009). Besides soil min- eral leaching (together with toxic metal solubilization), the soil dumped as coal waste suffers from the absence of N and P, Responsible editor: Zhihong Xu C. G. Chiochetta : M. R. Radetski : A. X. R. Corrêa : V. Tischer : E. N. Tiepo : C. M. Radetski (*) Laboratório de Remediação Ambiental, UNIVALI - Universidade do Vale do Itajaí, Rua Uruguai, 458, Itajaí, SC 88302-202, Brazil e-mail: radetski@univali.br Environ Sci Pollut Res DOI 10.1007/s11356-012-1269-2