Environmental impact of metals derived from mining activities: Processes, predictions, prevention

The concentrations of total nitrogen (TN), total phosphorus (TP), As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in both surface water and sediment samples from the upper Tigris River were determined to evaluate the level of contamination. All metal concentrations in water samples, except Cu, were lower than the maximum permitted concentration for the protection of aquatic life. TN, TP and metal concentrations in sediment samples from the first three sites situated downstream of Ergani Copper Mine Plant were much higher than those at other sites. There was a significant decrease in the concentrations of heavy metals in sediment from the last site downstream of the Dicle Dam. Sediment pollution assessment was undertaken using enrichment factor (EF) and geoaccumulation index ( I geo ). The sediments of sites downstream of the copper mine plant showed significant enrichment with Cd, Co, Cu, Pb and Zn, indicating metallic discharges from the Ergani Copper Mine Plant. The I geo values revealed that Cu (5.09), Co (4.26) and Zn (3.18) were significantly accumulated in the study area. Based on the comparison with sediment quality guidelines, the concentrations of Cr, Cu, Ni, Pb and Zn at sites downstream of the copper mine plant are likely to result in harmful effects on sediment-dwelling organisms. Cluster analysis suggests that As, Cd, Co, Cu, Ni, Pb and Zn are derived from anthropogenic sources, particularly metallic discharges of the copper mine plant.

Assessment of nutrient and heavy metal contamination in surface water and sediments of the upper Tigris River, Turkey

The role of fluvial geomorphic processes in the dispersal of heavy metals from mine sites

This paper reviews the major sources and transport characteristics of heavy metals in the hydrological cycle. It is demonstrated that heavy metal releases to the environment have changed from 19th and early 20th century production-related activities to consumption-oriented factors in more recent times. The relative roles of particle size, sorption and desorption processes, partitioning and the chemical speciation of heavy metals on fine sediments are identified to understand the likely fate of heavy metals released into fluvial systems. It is argued that the spatial and temporal distribution of heavy metals in the river corridor depends not only on an understanding of metal solubility and speciation, but also on an understanding of sediment dynamics which control, for example, floodplain alluviation and the accumulation of metals in the bottom sediments of contaminated rivers, lakes and reservoirs. Existing long- and short-term records are examined to identify the current state of knowledge about the factors which affect heavy metal releases into aquatic environments. With limited exceptions, it is shown that few long-term studies of trends in heavy metal transport are available although, for some major rivers, limited data on trends in metal concentration exists. Palaeolimnological reconstruction techniques, based on an analysis of lake and reservoir sediments, are identified as a possible means of supplementing monitored records of heavy metal transport. Although numerous studies have suggested that trends in atmospheric contamination, mining and urbanization may be identified in the bottom sediment record, other research has shown that the radionuclide-based chronology and the heavy metal distribution within the sediment are more likely to be a function of post-depositional remobilization than the history of metal loading to the basin. Despite these limitations, it is shown that the incorporation of reservoir bottom sediment analysis into a heavy metal research programme, based in river corridors of Midland England, provides an opportunity to identify and quantify the relative contribution of point and non-point contributions to the heavy metal budget and to relate trends in metal contamination to specific periods of catchment disturbance.

Heavy metals in the hydrological cycle: Trends and explanation

Several aspects of metal speciation in sediments are reviewed: (1) Due to the instability of polluted solid materials, sample handling and storage prior to analysis is problematic. In particular, changes from reducing to oxidizing conditions, which involve transformations of sulfides and a shift to more acid conditions, increase the mobility of critical metals. (2) Simple “standard” leaching tests can be used for easily soluble components such as halides or sulfates, but in most cases are not adequate for assessing mobility of trace metals. With sequential extraction procedures rearrangements of specific solid “phases” can be evaluated prior to their actual remobilisation. (3) Estimation of long-term release of metals from solids can be made using a test procedure, which combines data from column experiments applying controlled intensivation of parameters such as pH-value, redox potential and temperature with results from sequential extraction of the contaminated solids before and after exposure....

S.B Bradley

Papers

Heavy metals in the Hamps and Manifold valleys, North Staffordshire, U.K.: distribution in floodplain soils