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Shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are affected by submarine disposal
of industrial gold mine tailings and small-scale gold mining using mercury amalgamation. Industrial mine tailings contained
590–660 ppm arsenic, 490–580 ppm antimony, and 0.8–5.8 ppm mercury. Electron microprobe survey found both colloidal iron–arsenic-phases
without sulphur and arsenian pyrite in tailings and sites to which tailings had dispersed, but only arsenopyrite in sediments
affected by artisanal mining. Antimony in tailings was present as antimony oxides, colloidal iron–antimony phases, colloidal
iron–antimony phases, and stibnite in sediments affected by both types of mining. A sequential extraction found that 2% of
arsenic held in tailings and tailings-contaminated sediments was exchangeable, 20–30% was labile, including weakly adsorbed,
carbonate- and arsenate bound, 20–30% was metastable, probably incorporated into iron or manganese oxyhydroxides, or strongly
adsorbed to silicate minerals, and 40–48% was relatively insoluble, probably incorporated into sulphides or silicates. Arsenic
in sediments affected by artisanal gold mining was 75–95% relatively insoluble. Antimony in all sediments was >90% relatively
insoluble. Relative solubility patterns of most other metals did not differ between industrial tailings-affected, artisanal-mining
affected areas, and fluvial sediments. Results suggest that submarine tailings disposal is not suitable for refractory Carlin-like
gold deposits because ore processing converts arsenic to forms unstable in anoxic marine sediments.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
125.
Trace element concentrations in shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are
affected by submarine disposal of industrial gold mine tailings and unregulated dumping of tailings and wastewater from small-scale
gold mining using mercury amalgamation. Industrial mine tailings contained 590–690 ppm arsenic, 490–580 ppm antimony, and
0.8–5.8 ppm mercury. Tailings-affected sediment As and Sb concentrations were 20–30 times higher than in muddy sediments not
contaminated with tailings, and 50–60 times higher than pre-mining average. Highest mercury concentrations were observed in
sediments affected by small-scale mining using mercury amalgamation (5–29 ppm). Concentrations of most other trace elements
were comparable in sediments affected by both types of mining and were slightly higher than regional averages for sediments
collected before the onset of industrial mining. Elevated concentrations of both As and Sb in approximately equal proportions
suggest tailings dispersal of at least 3.5 km. Mercury released from artisanal gold mining dispersed up to 4 km from river
mouths. Slight increases in concentrations of non-mercury trace elements in areas affected by artisanal mining over pre-industrial
mining concentrations were probably caused by increased rates of erosion.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
126.
Evan D. G. Fraser 《Climatic change》2007,83(4):495-514
This paper builds on existing theory and proposes a framework to identify vulnerability to climate change in food systems by examining historic cases where common environmental problems caused famine. Cases presented are (1) Ireland’s Potato Famine, (2) El Niño induced famines during the Colonial period, and (3) Ethiopia between 1965 and 1997. Three factors stand out as common in each. Prior to each famine: (1) there were very few ways that people could obtain a living in the worst affected regions; (2) livelihoods in famine stricken communities came to depend on highly specialized agro-ecosystems that were sensitive to environmental change; (3) institutions failed to provide adequate safety nets to protect livelihoods from failure. This analysis suggests that vulnerability to climate change in food systems can be assessed by looking at agro-ecosystems, livelihoods and institutions. Local conditions, however, mean that ways of measuring these three factors will vary from place to place. As a result, direct comparisons are difficult. By conceptualizing these three variables as the axes of a three dimensional “vulnerability” space, it is possible to compare regions and look at trends over time by studying the paths through this “space” as traced by changes at the agro-ecosystem, livelihood, and institutional scale. 相似文献
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Fritz Petersen Jason A. Hubbart Elliott Kellner Evan Kutta 《Environmental Earth Sciences》2018,77(22):754
A high-spatial resolution study design was used to investigate the relationship between land use practices, stream physicochemistry, hydroclimate, and stream Escherichia (E) coli concentrations in a mixed-land-use watershed in the Appalachian region. Stream samples were collected daily from six monitoring sites and analyzed for total E. coli counts using an enzyme metabolism indicator method. Statistical comparison of E. coli concentration time series showed significant (p?<?0.05) differences between study sites. Although highest average E. coli concentrations were observed at two agricultural sites (534 and 582 colony-forming counts (CFU) per 100 mL, respectively), highest total loadings were observed within the receiving stream, with values increasing downstream (2?×?1012 and 4.2?×?1012 study total CFU for bracketed upstream and downstream sites, respectively). No single physical variable displayed a significant correlation (p?<?0.05) with observed E. coli concentration at every site. However, sites displayed different patterns of significant correlations (p?<?0.05) between E. coli concentration and both physicochemical (e.g. pH, dissolved oxygen saturation) and hydroclimate variables (e.g. streamflow and precipitation). Percent agricultural land cover was the only land use category that showed significant (p?<?0.04) correlation with study average E. coli concentrations, thereby emphasizing the importance of land use practices to stream pathogen regimes. Results validate the analytical method and provide high-resolution, detailed, quantitative characterizations of stream E. coli regimes, thereby supplying land and water resource managers with science-based information to advance management decisions and improve public health. 相似文献
129.
Channel instability has occurred in the Bell River in the form of meander cutoffs, a number of which have occurred since 1952. Increased sediment loading from widespread gully erosion in the catchment has been proposed as the trigger for this instability. Willow species of the Salix family, in particular S. caprea, have been planted along the banks in an effort to prevent further channel shifting. This study reports the results of an investigation into the effect of vegetation on channel form and stability over a 17 km stretch of channel. Results indicate that riparian vegetation has significant effects on channel form which have implications for channel stability. Riparian vegetation increases bank stability and reduces channel cross-sectional area, thereby inducing stability at flows less than bankfull. Evidence indicates that narrow stable stretches are associated with relatively high levels of riparian vegetation. Wider, unstable channels are associated with relatively less riparian vegetation. The effectiveness of riparian vegetation relative to bank sediments was investigated. A dense growth of willows was found to have an equivalent effect to banks with a silt-clay ratio of about 70 per cent. The channel narrowing induced by vegetation may contribute to channel shifting at high flows. The reduced channel capacity is thought to result in more frequent overbank flooding which may ultimately lead to channel avulsion. Thus where increased sediment loading is pushing the channel towards instability, vegetation may be effective in imparting local stability, but it is unable to prevent long-term channel shifts, and may rather help to push the system towards more frequent avulsions. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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