326 Bud, Duma, Denuþ, Taºcu BHM, 152. Jg. (2007), Heft 10 Water pollution due to mining activity. Causes and consequences. I. Bud, S. Duma, I. Denuþ, I. Taºcu In Baia Mare mining area, the exploitation activity has a long history with important impact in water pollution. Actually, the closure mining activity for some perimeters may lead to the increase of hydrostatic level which will carry of siccated sulphates formed along mining activity duration. In some mining perimeters the volume of these sulphates is very impor- tant. The paper includes a syntheses of water analyses done (in 2006–2007) at the exit of the underground gallery. The conclusion is that in the next years the values analysed will increase due to the presence of these sulphates. The closure of mining activity was done with ignorance concerning environmental consequences in short and specially long term, taking no measures to diminish this impact. Wasserverunreinigung aufgrund von Bergbauaktivitäten. Ursachen und Konsequenzen. Bergbau, insbesondere der Abbau von Nicht-Eisen-Metallerze hat in Baia Mare (Rumänien) eine lange Tradition. Der Beitrag diskutiert umweltre- levante Aspekte der Nicht-Eisen-Metall-Industrie. Festgehalten wird, dass die Schließung von Bergbaubetriebe grund- sätzlich die Umweltkonsequenzen in mittel- und langfristiger Hinsicht ignoriert hat. Es wurden generell keine Maßnah- men gesetzt, um Auswirkungen auf die Umwelt zu minimieren. 1. Introduction Mining industry is an important generator of pollutants emitted in air, water and soil, and large volumes of ster- ile deposits in tailing and waste dams. The specific of this industry, from environmental protection point of view, is that it generates pollutants along the activity and after closure with long-term impact. This industry with its branches exploitation and min- eralurgy is a huge consumer of industrial water and an important contributor to the pollution of natural receptors. Natural water in mining regions has various composi- tions, in function of quantities and qualities of mining water receipted, of meteoric water and residual water overflowed. Following the extraction activity and ore min- ing preparation, a huge volume of admixture water (con- taminate with different pollutants, reagents, metallic ions, suspensions, etc) which have a very toxic action to envi- ronment. In consequence, the natural environment suf- fers important evolutional degradations. The mineral exploitation, underground or quarries, is associated with important local modification of surface configuration, which affects the regional and basin hydrologic regime, both in quantity (by amplification of surface debits infiltrated in inferior zones) and specially quality (by important mineral substances dissolved and overflowed in natural receptors). 2. Geology of Baia Mare Area Baia Mare mining area is one of the most important min- ing zones, placed in the NV of Romania, where the ore deposits exploitation activities and mineralurgy methods started hundreds years ago and evaluated in the rhythm of human community development in the area. The mineral useful substances of Baia Mare metalo- genetic district, forming predominantly non-ferrous exploitable accumulations, belong, from the geologic point of view, to metalogenetic province of eruptive neo- gen. They are disposed, from the geomorphologic point of view, on the southern side of volcanic mountains Oas – Gutai – Varatec – Tibles. The majority of these ore deposits are veins, corresponding to fractures where hydrothermal solutions circulated, on the last period of magma differentiation, which determinate their forma- tion. The veins are over five hundreds and are dissemi- nated irregularly in Baia Mare region. The thickness of the veins is between some decime- ters and some meters (regularly 2–3 m); Baia Sprie Prin- cipal Vein has between 10–30 m of thickness and Cre- menea Suior vein arrive to 57 m Concerning the depth of veins, its variable, between some meters to some hun- dreds meters. The hosted rocks of these veins belong to the follow- ing formations: -– volcanic neogene rocks – represented by dacites and numerous varieties of andezites – volcano-sedimentary acid formation, Miocene, con- taining pyroclastic rocks (especially riodacitic rocks) – miocene melase – including marls, sands, clays, sandstones, etc – paleogen flysh-represented by marls, sandstones, clays, etc Concerning the mineralogical composition, metallic ore deposits could be classified in following categories: – gold – silver ores (Baita, Sasar, Valea Rosie, Dealul Crucii, Suior – superior part) where gold and silver appear in native form or combined in sulfosalts PhD. Simona Duma, Ioan Bud, PhD., Ioan Denuþ, PhD., Ioana Taºcu, PhD., alle: North University of Baia Mare, Dr. V. Babes Street 62A, 430083 Baia Mare / Rumänien.