The geochemistry of the Black Warrior River, Alabama

Based on discharge, the Mobile/Alabama River System (MARS) is the fourth largest river system in the lower 48 United States. As the largest sub-basin in the MARS and completely within the state of Alabama, the Black Warrior River has the potential to contribute a significant amount of dissolved material to the MARS due to its geological and anthropogenic diversity. The Black Warrior River drains three of the geological provinces in the state and anthropogenic pollutant sources include discharges from surface coal mines, coalbed methane production, various industries, municipal waste water, and agricultural runoff.; There were three aspects to this work. First was a statistical analysis of historical USGS data the time period 1966 to 1995. Calcium, Cl− , SO₄=, discharge and precipitation were correlated over time for seven locations within the MARS. Chloride and SO ₄= increased over time at the Black Warrior River location and coincided with the development of the coalbed methane industry upstream from this sample location.; Second, a preliminary geochemical profile of the MARS was performed on 15 surface water samples collected in 1996. Although the system as a whole did not seem impacted by anthropogenic activities, the Black Warrior was shown to have enriched concentrations of major elements except Ca and HCO₃ − compared to the other MARS basins and enriched Co and Mo compared to the world river average. These results led to the choice of the Black Warrior River as the focus of a more detailed geochemical study.; A geochemical analysis was performed on samples collected at 12 locations along the Black Warrior River. Samples were collected three times between 1997 and 1999 and analyzed for 11 major elements and 11 trace metals. Although only SO₄=, Co, and Mo were higher than the world river average, all elements except Ca and HCO₃− were enriched in areas influenced by mining compared to the relatively pristine areas sampled in this study. This is especially true for Cl− , Br−, NO₃−, SO₄=, and Mo. This work shows the influence of anthropogenic activities on the overall geochemistry of the MARS and the impact of the Black Warrior River to this system.