Cyanidation of mercury-rich tailings in artisanal and small-scale gold mining: identifying strategies to manage environmental risks in Southern Ecuador

In many countries, such as Brazil, Colombia, Ecuador, Indonesia, Venezuela and Zimbabwe, amalgamated tailings are leached with cyanide to recover remaining gold. This paper describes a recently completed study conducted at seven gold processing centers in Portovelo-Zaruma, Southern Ecuador, which involved consultation with local miners. The objective of the study was to understand the behaviour of mercury (with a focus on mercury loss) in artisanal gold mining operations through the evaluation of two cyanidation processes (Merrill-Crowe and Carbon-in-pulp), using a participatory approach. In order to assess the kinetics of mercury dissolution in cyanide, a bottle roll test was conducted in the laboratory. In the Merrill-Crowe cyanidation process, an average of 24.2% of metallic mercury was determined to be trapped at the bottom of the agitation tanks; 33.1% of mercury is lost in association with solid material and 11.7% is lost in solution. Approximately 31.0% of mercury in solution is sent to the zinc precipitation cells from which 27.8% is precipitated on the zinc shavings, with 3.23% remaining in solution. The mercury precipitated on to the zinc is lost to the atmosphere when the shavings are burned at 900 °C. In the Carbon-in-pulp (CIP) leaching system, 11.2% of the mercury is lost with the solid tailings; 31.6% of the mercury is associated with fine particles in suspension and 50.8% is likely dissolved. About 2.68% is trapped at the bottom of the tank and 3.72% is absorbed by the activated carbon. The bottle roll test revealed that mercury dissolution is directly proportional to cyanide concentration. At 10 g/ton of cyanide, approximately 42% of mercury was leached, whereas all gold was solubilized. During this study, miners recognized the risk associated with the cyanidation of mercury-rich tailings, and were aware of how much mercury is discharged to local streams and to the atmosphere. The active participation of miners in this study has led to the strengthening of their knowledge and awareness of mercury contamination, and has enhanced their understanding of the nature of the problem, as well as the weaknesses and strengths of the system they operate.     

Revolution or inch-by-inch? Campaign approaches on climate change by environmental groups

Climate change is a significant environmental, social and environmental problem that has been identified by scientists in consensus internationally. The Australian Government’s response is considered by environmental non-government organisations (NGOs) to be inadequate. NGOs are ‘change agents’ of society, and in this role they are agitating to influence political decision-making on climate change response. This paper outlines the campaign strategies being used by Australian NGOs to attract public and political attention to the issue of climate change. Using seven NGOs as case studies, the archival materials of these organisations were accessed and analysed. Current academic and other literature also was used to reflect on their effectiveness. Four campaign themes and, within these, fifteen activities were identified. The results indicate that the notion of whether NGOs are undertaking an ‘revolutionary’ or ‘incremental’ approach, or any other narrow strategic approach put forward by various scholars is too simple for analysing campaigns: none of the NGOs appear to intentionally favour one type of strategy. The question raised by this finding is whether the NGOs’ current ‘multi-strategic’ approach is effective. This research contributes to filling the information gap with regard to NGO campaign strategies on environmental issues, and highlights the need for further research.     

An evaluation of the extraction efficiencies of some common extractants for Fe, Cr, Mn, Ni, Pb and Cu on five grain-size fractionated, tropical marine sediments

A number of extractants and extraction procedures were evaluated using a variety of tropical marine sediments fractionated on the basis of grain size. Total metal levels obtained by X-ray fluorescence analysis were used in the normalization of levels obtained by these extractants/extraction procedures. A change in extraction efficiency with change in the pH of the extractant used was observed for Fe and Mn irrespective of particle size of the fraction. Iron was extracted uniformly at each leaching level for the <53micro fractions. Manganese had comparable extraction efficiencies with both weak and strong extractants. The extraction efficiencies for Cr were generally low possibly due to an association with the residual phase. The ease with which both Pb and Ni were extracted indicated that they were only loosely bound in the sediments. The extraction efficiencies for Cu varied widely for the fractions of larger particle sizes but fell within narrow ranges for the <53micro fractions.     

Estimation of septic tank setback distances based on transport of E. coli and F-RNA phages

Setback distances between septic tank systems and the shorelines of Lake Okareka, New Zealand were determined from model simulations for a worst-case scenario, using the highest hydraulic conductivity and gradient measured in the field, removal rates of the microbial indicators (Escherichia coli and F-RNA phages) determined from a column experiment, and maximum values of the design criteria for the disposal system, and assuming an absence of an unsaturated zone, a continuous discharge of the raw effluent from a failed or non-complying treatment system (both indicators at concentrations of 1x10(7) counts/100 ml) into the groundwater and no sorption of pathogens in the aquifer. Modelling results suggest that the minimal setback distances were 16 m to satisfy the New Zealand Recreational Water Quality Guidelines for E. coli <126 per 100 ml (Ministry for the Environment, 1999) and 48 m to meet the Drinking-Water Standards for New Zealand 2000 for enteric virus <1 per 100 l (Ministry of Health, 2000). These distances may be applicable for other lakeshores in pumice sand aquifers with groundwater velocities <7 m/day. Findings of laboratory column and batch experiments provided an insight into the microbial attenuation and transport processes in pumice sand aquifers. Bacterial removal was predominately through filtration (87-88%) and partially by die-off (12-13%), while viral removal was by both die-off (45%) and filtration (55%). In addition, microbial die-off in groundwater without aquifer material (i.e., free microbes) was much lower than die-off in groundwater with aquifer material (i.e., sorbed microbes) and contributed only 2-6% to the total removal. This implies that the setback distances estimated from die-off rates for the free microbes, determined in the laboratory without considering aquifer media and other removal processes, which are often reported in the literature, could be larger than necessary.     

Developing sustainable practices to adapt to the impacts of climate change: a case study of agricultural systems in eastern England (UK)

The weight of scientific evidence suggests that human activities are noticeably influencing the world's climate. However, the effects of global climate change will be unevenly spread, due to local variations in vulnerability and adaptive capacity. Using downscaled projections of future UK climates over the next 50 years, this paper investigates the impacts of, and possible responses to, climate change in one small area in eastern England, selected as a test-bed for sustainable agriculture. It shows that local agricultural systems are vulnerable to changes in the climate. At present, however, these considerations have a limited effect on agricultural operations, which are mainly driven by short-term events and 'non-climate' policies, such as agricultural price support. The capacity of agricultural systems to adapt successfully to climate change will be determined by the ability of producers to integrate climate change into their planning strategies with a view to ultimately ensuring sustainable agricultural practices in the long term. Electronic Publication     

液相色谱-正离子模式电喷雾质谱分析源水和饮用水中的22种碱性和中性农药及其代谢物

本文开发了一种定量分析源水和饮用2种农药及其代谢物的方法.本法采用固相萃取法处理水样,液相色谱和电喷雾质谱进行检测.回收率、灵敏度、准确性及精密度均达到了英国法规的要求.     

Nonadditive effects of leaf litter species diversity on breakdown dynamics in a detritus-based stream

Since species loss is predicted to be nonrandom, it is important to understand the manner in which those species that we anticipate losing interact with other species to affect ecosystem function. We tested whether litter species diversity, measured as richness and composition, affects breakdown dynamics in a detritus-based stream. Using full-factorial analyses of single- and mixed-species leaf packs (15 possible combinations of four dominant litter species; red maple [Acer rubrum], tulip poplar [Liriodendron tulipifera], chestnut oak [Quercus prinus], and rhododendron [Rhododendron maximum]), we tested for single-species presence/absence (additive) or species interaction (nonadditive) effects on leaf pack breakdown rates, changes in litter chemistry, and microbial and macroinvertebrate biomass. Overall, we found significant nonadditive effects of litter species diversity on leaf pack breakdown rates, which were explained both by richness and composition. Leaf packs containing higher litter species richness had faster breakdown rates, and antagonistic effects of litter species composition were observed when any two or three of the four litter species were mixed. Less-consistent results were obtained with respect to changes in litter chemistry and microbial and macroinvertebrate biomass. Our results suggest that loss of litter species diversity will decrease species interactions involved in regulating ecosystem function. To that end, loss of species such as eastern hemlock (Tsuga canadensis) accompanied by predicted changes in riparian tree species composition in the southeastern United States could have nonadditive effects on litter breakdown at the landscape scale.     

Voice as Entry to Agriculturalists’ Conservationist Identity: A Cultural Inventory of the Yellowstone River

We explored the communicative construction of a conservationist identity among primary producers by excavating voices of agriculturalists operating along the Yellowstone River (Montana, USA). We used a cultural inventory approach to discover and then listen to informants’ voices as they constructed their conservation identity. Those who self-identified as conservationists talked about their ecological and social responsibilities, and described challenges they faced in protecting individual resources and system processes of the watershed. For these agriculturalists, conservation and production are inextricably linked, and enable them to provide a sustainable resource base for future generations. Insight from these voices enhances understanding of what sustainability could mean to those who self-identify as both conservationists and primary producers.