Die Wirkung wäßriger Streuextrakte verschiedener Waldbäume auf Mycelwachstum und Konidiosporenkeimung von Fomes annosus (Fr.) Cke.

The effect of water extracts of leaf and needle litter from different forest trees on the mycelial growth and the germination rate of conidia of Fomes annosus (Fr.) Cke. Litter extracts from various forest trees and stands have distinct effects on mycelial growth and germination rate of conidia of Fomes annosus. The effects depend on concentration of the extract, period of extraction and on date of collecting the litter samples.     

Mercury contamination in the Carson River,Nevada: A preliminary study of the impact of mining wastes

From 1860 to 1890, approximately 7 100 metric tons of metallic mercury (Hg) were released into the Carson River-Lahontan Reservoir watershed as a by-product of Comstock Lode silver (Ag) and gold (Au) ore refining. Present-day Hg contamination is most severe in mine tailings, where total Hg concentrations can exceed several hundred µg/g. Hg-laden tailings were also dumped directly into the Carson River, and were subsequently transported downstream into the Lahontan Reservoir and the Stillwater Wildlife Management Area. The Hg, Ag and Au contents of sediments from the Carson River and the Lahontan Reservoir are well above local background levels, and both Ag and Au contents are positively correlated to Hg. Thus, tailings-derived Hg has been redistributed throughout the entire Carson-Lahontan watershed over the last century. Total Hg concentrations in water samples from the Carson River at seven localities show that: 1) elevated (e.g., >20 ng/L) Hg levels in Carson River waters first appear downstream from accumulations of mill tailings, 2) total Hg concentrations in unfiltered and filtered water from the Carson River increase downstream (i.e. away from the tailings piles), and 3) Hg concentrations in both the Carson River (downstream from the tailings piles) and the Lahontan Reservoir are among the highest known worldwide (100 to 1000 ng/L). Filtered water samples from the Carson-Lahontan system also have high Hg contents (up to 113 ng/L), and suggest that the >0.4 µm particle fraction constitutes over 60% of the total water-borne Hg.     

Mercury Contamination of Alluvial Sediments within the Essequibo and Mazaruni River Basins,Guyana

Small- and medium-scale mining operations in Guyana have increased significantly since the late 1980s. The majority of these gold mining operations utilize mercury (Hg) amalgamation methods in the recovery process, raising the question as to the significance of Hg inputs to the environment from mining activities. In March and April, 2001, 168 samples were collected from floodplain, sand bar, and channel bed deposits along a 350 km reach of the Mazaruni River and a 160 km reach of the Essequibo River. Distinct trends in the geochemical data suggest that much of the Hg found in the alluvial deposits is related to anthropogenic sources, including (1) Hg concentrations in floodplain, channel bed and sand bar deposits locally exceed background values defined by ferralitic soils; (2) core data reveal that Hg concentrations within floodplain deposits have increased in recent years; and (3) high Hg concentrations along the channels can be attributed to the influx of material from tributaries affected by mining operations, or to mining activities along the rivers. Recent investigations in Amazonia have argued that Hg from amalgamation mining represents a small portion of the total Hg load to riverine systems, the majority coming from the erosion of Hg enriched upland soils within deforested terrain. Geochemical data from the Essequibo and Mazaruni Rivers suggest that Hg from mining may be a more significant source in Guyana where large-scale deforestation is limited. However, it is unclear whether the increased Hg represents the direct input associated with the amalgamation process, or Hg associated with the erosion of soils and sediments that results from activities that accompany mining.     

Dispersal of mercury-contaminated sediments by geomorphic processes,sixmile canyon,Nevada, USA: Implications to site characterization and remediation of fluvial environments

The discovery of the Comstock Lode near Virginia City, Nevada, in 1859 resulted in the construction of more than 30 stamp-mills along Sixmile Canyon and its tributaries to process the gold and silver ore. Extraction of the precious metals from the ore was accomplished using a crude mercury (Hg) amalgamation process. As a result, a substantial quantity of Hg was released along with tailings materials to this tributary of the Carson River. During the past 134 years, Hg-contaminated sediments have been eroded from the mill sites and transported downstream by fluvial processes, thereby expanding the influence of Hg pollution. Geomorphic and geochemical data have been combined in this study to document the distribution, quantity, and physical dispersal of Hg-contaminated materials from Sixmile Canyon to the Carson River. These data show that the influx of Hg to the Carson River has varied through time as a function of the erosional and depositional processes operating on the Sixmile Canyon Alluvial Fan located between the canyon and the Carson River channel; relatively high influx rates to the river occurred immediately after mining began and from approximately 1933 to 1948. Hg-polluted sediments are located within discrete areas of the fan and comprise about 21 % of the total active and relict fan surface. Mass balance calculations estimate that about 31,500 kg of Hg, 18,200 oz of An, and 1,205,800 oz of Ag are contained within 710,700 m³ of contaminated materials. If site remediation is conducted, extraction of An and Ag, which is worth about $12 million at current market prices, would greatly defray the costs of clean-up activities. The study also illustrates that the effects of Hg may be temporally and spatially displaced from the period and location of milling activities. Thus, we conclude that to accurately assess the site for remediation, an understanding of the spatial and temporal variations in geomorphic dispersal processes is required.