Kevin Telmer

CARBON FLUXES, PCO2 AND SUBSTRATE WEATHERING IN A LARGE NORTHERN RIVER BASIN, CANADA : CARBON ISOTOPE PERSPECTIVES

Abstract Isotopic composition of dissolved inorganic carbon ( δ 13 C DIC ) in the Ottawa River basin is about −8 and −16‰ for lowland carbonate and upland silicate tributaries, respectively. This suggests that (1) the source of DIC to the Ottawa River is soil respiration and carbonate weathering, (2) exchange with the atmosphere is unidirectional or volumetrically unimportant, and (3) in-river respiration and photosynthesis are not significant influences on the river carbon budget. Accepting these constraints, chemical and isotopic data are used to reconstitute soil pCO2 for tributary catchments. Averages for upland silicate, mixed, and lowland carbonate basins are calculated to be roughly 2000, 5000, and 30,000 ppm, respectively. These values are used as input to model the pathway of carbon through the watershed—rain water to soil water to river water. The flux of carbon from the Ottawa River as DIC is calculated to be 4.3×1010 mol C/a. Utilizing carbon isotopes, 75% and 25% of the Ca2++Mg2+ flux is calculated to originate from carbonate and silicate weathering, respectively, and 61% of the DIC is calculated to originate from organic respiration. The latter represents some 6% of respired carbon in the basin, assuming an average respiration rate of 0.5 mmol C m−2 h−1. Based on a diffusion model, CO2 evasion to the atmosphere from the Ottawa River and its tributaries is estimated to be 1.3×1010 mol C/a or 30% of the DIC flux.

World emissions of mercury from artisanal and small scale gold mining

We estimate mercury releases from artisanal and small scale gold mining (ASGM) based on available data about mercury and gold exports and imports by country and from field reports from the countries known to have active ASGM communities. The quality of the estimates ranges from reasonable to poor across the countries. This paper aims to give a first order estimate of the amount and location of mercury being released into the environment globally by ASGM, to motivate stakeholders to improve the quality of these estimates, to illustrate the linkages between global mercury trade and its use in ASGM, and the fourth objective is to provide a practical outline of the options available for reducing mercury use in ASGM. We estimate that artisanal and small scale gold mining releases between 640 to 1350 Mg of mercury per annum into the environment, averaging 1000 Mg yr-1, from at least 70 countries. 350 Mg yr-1 of this are directly emitted to the atmosphere while the remainder (650 Mg yr-1) are released into the hydrosphere (rivers, lakes, soils, tailings). However, a significant but unknown portion of the amount released into the hydrosphere is later emitted to the atmosphere when it volatilizes (latent emissions). Considering that ASGM is growing, latent emissions conservatively amount to at least 50 Mg yr-1 bringing the total emission of mercury to the atmosphere from ASGM to 400 Mg yr-1. This estimate of emission to the atmosphere differs from the previous one provided in the 2002 UNEP Global Mercury Assessment both in terms of its magnitude (400 Mg yr-1, versus 300 Mg yr-1) and in the way the estimate has been made. The current estimate is based on a better understanding of ASGM and on a wider variety of information sources, more field evidence, better extrapolation methods, and independent testing by analysis of official trade data.

Using ALOS/PALSAR and RADARSAT-2 to Map Land Cover and Seasonal Inundation in the Brazilian Pantanal

The Brazilian Pantanal is a large continuous tropical wetland with large biodiversity and many threatened habitats. The interplay between the distribution of vegetation, the hydrology, the climate and the geomorphology nourishes and sustains the large diversity of flora and fauna in this wetland, but it is poorly understood at the scale of the entire Pantanal. This study uses multi-temporal L-band ALOS/PALSAR and C-band RADARSAT-2 data to map ecosystems and create spatial-temporal maps of flood dynamics in the Brazilian Pantanal. First, an understanding of the backscattering characteristics of floodable and non-floodable habitats was developed. Second, a Level 1 object-based image analysis (OBIA) classification defining Forest, Savanna, Grasslands/Agriculture, Aquatic Vegetation and Open Water cover types was achieved with accuracy results of 81%. A Level 2 classification separating Flooded from Non-Flooded regions for five temporal periods over one year was also accomplished, showing the interannual variability among sub-regions in the Pantanal. Cross-sensor, multi-temporal SAR data was found to be useful in mapping both land cover and flood patterns in wetland areas. The generated maps will be a valuable asset for defining habitats required to conserve the Pantanal biodiversity and to mitigate the impacts of human development in the region.

Global Mercury Emissions to the Atmosphere from Natural and Anthropogenic Sources

This chapter provides an up-to-date overview of global mercury emissions from natural and anthropogenic sources at country and regional/continental scale. The information reported in Chapters 2–8 is the basis of the assessment reported in this chapter, however, emissions data related to sources and regions not reported in chapters 2–8 have been derived, to the extent possible, from the most recent peer-reviewed literature and from official technical reports. Natural sources, which include the contribution from oceans and other surface waters, rocks, top soils and vegetation, volcanoes and other geothermal activities and biomass burning are estimated to release annually about 5207 Mg of mercury, part of which represent previously deposited anthropogenic and natural mercury from the atmosphere to ecosystem-receptors due to historic releases and part is a new contribution from natural reservoirs. Current anthropogenic sources, which include a large number of industrial point sources are estimated to release about 2917 Mg of mercury on an annual basis, the major contribution is from fossil fuel-fired power plants (1422 Mg yr-1), artisanal small scale gold mining (400 Mg yr-1), waste disposal (187 Mg yr-1), non-ferrous metals manufacturing (310 Mg yr-1) and cement production (236 Mg yr-1). Our current estimate of global emissions suggest that summing up the contribution from natural and anthropogenic sources nearly 8124 Mg of mercury is released annually to the global atmosphere. The evaluation of global emissions presented in this report differs from previous published assessments because in the past, emissions from several sources, i.e., forest fires and coal-bed fires have not been accounted for, and also because of improved knowledge of some anthropogenic and natural sources (i.e., emissions from oceans, vegetation) as suggested by the most up-to-date literature.

The spatial resolution of LA-ICP-MS line scans across heterogeneous materials such as fish otoliths and zoned minerals

LA-ICP-MS line scans can provide equivalent or better information about the distribution of elements in heterogeneous solids than discrete spot analysis; and at much reduced time and cost. However, to do so, the spatial resolution for given instrumentation and operating conditions must be known. Here, we present a quantitative and reproducible method to do this that requires line scans across a sandwich of three glasses of varying certified concentrations of trace elements. To produce sufficient counting statistics, only Ca, Sr, Rb, and Pb were analysed. Raw data (counts per second) are reduced to “instantaneous concentration” and then filtered to produce concentration profiles that contain the same dimensions as the original data. The spatial resolution is empirically determined from these profiles by using a statistical “confidence” window. Spatial resolution is controlled by the magnitude of concentration gradients, the direction of concentration shifts, and the instrumental configuration and settings such as cell size and shape, and the speed of the scan. Spatial resolution is better for increasing concentration profiles than decreasing ones by a factor of 2. The relationship between the magnitude of the concentration gradient and the spatial resolution is linear. Therefore, once the range of concentration variation is known in any target, a minimum resolution can be determined from this linear relationship. The spatial resolutions of the three elements examined are observed to be the same suggesting that element specific ablation behaviours are not a significant control on spatial resolution. A Sr concentration profile from a natural sample (fish otolith) is generated, and the resolutions from the glass sandwich are applied. For the concentrations observed and the settings and hardware used, a minimum spatial resolution of 50 µm was calculated. Concentration variations at smaller scales can be detected but not quantified.

Isotopic constraints on the transpiration, evaporation, energy, and gross primary production Budgets of a large boreal watershed: Ottawa River Basin, Canada

The residual signals of the physical and chemical processes undergone in a river basin are stored in the isotopic composition of river water and are used here to isolate and quantify fluxes of water, energy and carbon for a large boreal river basin. The integrated nature of the river signal is exploited to provide meaningful basin-wide annual averages for fluxes difficult to quantify and extrapolate by studying highly variable interface exchanges at discrete locations. The slope of the linear regression of deuterium (δD) and oxygen (δ18O) isotopes for the Ottawa River is ∼6.0, considerably less than the slope of the local meteoric water line (7.7). This discrepancy is a consequence of evaporative loss from open water bodies and soils and, through a new method, is calculated to be 8.1% of annual precipitation. As well, on the basis of thirty years of daily meteorological and discharge data, annual evapotranspiration for the Ottawa River basin is calculated to be 53.1%. Combining the evaporation and evapotranspiration calculations apportions 45% of the water losses to transpiration. The energy required to drive these cycles is calculated to be 8% of annual solar radiation for total evapotranspiration and 13% of growing season solar radiation for transpiration. These energies are transformed into latent heat. The water use efficiency ratio is used to estimate total fixation of carbon (gross primary production (GPP)) for the basin at 15.6 mol C m−2 yr−1. This rate is substantially greater than the export of carbon via rivers plus rates estimated for carbon respiration in the literature, indicating that the boreal forest is a plausible component of the postulated “missing” carbon sink. Comparison of accumulation rates of C in peatlands and the rates required to account for the missing sink suggest that peat accumulation rates are ∼20 times too slow to account for the missing sink flux. Speculatively, the living biomass of the boreal forest is the dominant sink. Accepting this, the respiration rate needed for a steady state balance between the calculated boreal forest GPP and the missing global carbon sink is found to be around 5.6 mol C m−2 yr−1.

The role of smelter emissions and element remobilization in the sediment chemistry of 99 lakes around the Horne smelter, Québec

Ninety-nine lakes were sampled at varying distances up to 75 km from the Horne smelter at Rouyn-Noranda, Quebec, to study the influence of the smelter versus other factors on metal concentrations in lake sediments. Most of these lakes lie within the Abitibi Greenstone Belt, a zone of extensive base metal and gold mineralization and the focus of a mining and smelting economy for almost a century. Lake sediment cores, c. 25 cm long, were collected and sampled at the top (0–2 cm) and the bottom (18–20 cm) to capture sediment that was deposited after the smelter was in operation (‘post-industrial’) and well before the mining and smelting activity was started (‘pre-industrial’). Additionally, nine cores were sampled in 1 cm increments to depths of up to 50 cm to study temporal patterns and potential element remobilization in detail. The cores were analysed for an extensive suite of elements. This paper focuses on those elements that are emitted by the smelter for which there are records of emissions through time, namely As, Cd, Cu, Pb and Zn. A spatial statistical approach – a logistic model of metal content versus distance from the smelter – was used investigate the relationship of sediment chemistry with smelter emissions and other possible influences. Using Cu as a representative proxy for the other emitted metals, this analysis demonstrates that elements are enriched in lake sediments by a factor of about three times around the smelter, that the impact of the smelter is detectable in lakes to a distance of at least 50 km, and that there is no obvious association between sediment Cu concentration and bedrock geology, land-use, lake pH, or lake morphometry (lake area/lake catchment area). The nine lakes studied in detail show enrichment towards the sediment–water interface (SWI) and relatively steady concentrations below depths of c. 10 cm. However, depth profiles do not match changes in the magnitude of smelter emissions through time, nor do they match changes in emission chemistry (element ratios) through time. Element ratios do generally move towards the chemistry of the emissions, suggesting smelter influence, but do not do so predictably. For example, (i) trends in the Cu/Pb ratio continue to the very bottom of cores into material deposited hundreds of years before industrialization, and (ii) proximity to the smelter does not lead to greater similarity between sediment and emission chemistry. These results suggest that significant element remobilization is occurring and that it differs from lake to lake and from element to element. We conclude that lakes within 50 km of the smelter have elevated metal concentrations in their near-surface sediments due to stack emissions but, due to element cycling and mobility, it is difficult to quantitatively determine the magnitude of metal increase attributable to the smelter. We also suggest that due to upward remobilization, the duration of industrial metal enrichments in surface sediments (the residence time) may be increased, thereby making surface enrichments more persistent than would be predicted by the sedimentation rate.

Toward an assessment of the global inventory of present-day mercury releases to freshwater environments

Aquatic ecosystems are an essential component of the biogeochemical cycle of mercury (Hg), as inorganic Hg can be converted to toxic methylmercury (MeHg) in these environments and reemissions of elemental Hg rival anthropogenic Hg releases on a global scale. Quantification of effluent Hg releases to aquatic systems globally has focused on discharges to the global oceans, rather than contributions to freshwater systems that affect local exposures and risks associated with MeHg. Here we produce a first-estimate of sector-specific, spatially resolved global aquatic Hg discharges to freshwater systems. We compare our release estimates to atmospheric sources that have been quantified elsewhere. By analyzing available quantitative and qualitative information, we estimate that present-day global Hg releases to freshwater environments (rivers and lakes) associated with anthropogenic activities have a lower bound of ~1000 Mg·a−1. Artisanal and small-scale gold mining (ASGM) represents the single largest source, followed by disposal of mercury-containing products and domestic waste water, metal production, and releases from industrial installations such as chlor-alkali plants and oil refineries. In addition to these direct anthropogenic inputs, diffuse inputs from land management activities and remobilization of Hg previously accumulated in terrestrial ecosystems are likely comparable in magnitude. Aquatic discharges of Hg are greatly understudied and further constraining associated data gaps is crucial for reducing the uncertainties in the global biogeochemical Hg budget.

Distribution of Artisanal and Small-Scale Gold Mining in the Tapajós River Basin (Brazilian Amazon) over the Past 40 Years and Relationship with Water Siltation

An innovative remote sensing approach that combines land-use change and water quality information is proposed in order to investigate if Artisanal and Small-scale Gold Mining (ASGM) area extension is associated with water siltation in the Tapajos River Basin (Brazil), containing the largest small-scale gold mining district in the world. Taking advantage of a 40-year period of the multi-satellite imagery archive, the objective of this paper is to build a normalized time-series in order to evaluate the influence of temporal mining expansion on the water siltation data (TSS, Total Suspended Solids concentration) derived from previous research. The methodological approach was set to deliver a full characterization of the ASGM expansion from its initial stages in the early 1970s to the present. First, based on IRS/LISSIII images acquired in 2012, the historical Landsat image database (1973–2001) was corrected for radiometric and atmospheric effects using dark vegetation as reference to create a normalized time-series. Next, a complete update of the mining areas distribution in 2012 derived from the TerraClass Project (an official land-use classification for the Brazilian Amazon) was conducted having IRS/LISSIII as the base map with the support of auxiliary data and vector editing. Once the ASGM in 2012 was quantified (261.7 km2) and validated with photos, a reverse classification of ASGM in 2001 (171.7 km2), 1993 (166.3 km2), 1984 (47.5 km2), and 1973 (15.4 km2) with the use of Landsat archives was applied. This procedure relies on the assumption that ASGM changes in the land cover are severe and remain detectable from satellite sensors for decades. The mining expansion area over time was then combined with the (TSS) data retrieved from the same atmospherically corrected satellite imagery based on the literature. In terms of gold mining expansion and water siltation effects, four main periods of ASGM activities were identified in the study area: (i) 1958–1977, first occurrence of mining activities and low water impacts; (ii) 1978–1993, introduction of low-budget mechanization associated with very high gold prices resulting in large mining area expansion and high water siltation levels; (iii) 1994–2003, general recession of ASGM activities and exhaustion of easy-access gold deposits, resulting in decreased TSS; (iv) 2004 to present, intensification of ASGM encouraged by high gold prices, resulting in an increase of TSS.

Assessing occupational mercury exposures and behaviours of artisanal and small-scale gold miners in Burkina Faso using passive mercury vapour badges

Abstract Artisanal and small‐scale gold mining (ASGM) is a crucial economic activity in Burkina Faso, however it is associated with significant mercury exposure and health concerns. The aim of the present study was to assess the level of mercury (Hg) vapour exposures and occupational behaviours at a representative site using Hg vapour monitor badges and questionnaires. To our knowledge this is the first time that personal exposure to Hg vapour during ASGM activities has been reported. The study population were ASGM workers who completed a questionnaire (n=100) or participated with an occupational exposure assessment using commercially available passive Hg vapour samplers (n=44). Occupational exposure to Hg was high during open‐air burn events with a time weighted average (TWA) exposure of 7026±6857 &mgr;g/m3 for burners, and 1412±2870 &mgr;g/m3 for bystanders. Most (82%) of the people present at the burn exceeded the Permissible Exposure Limit (PEL) of 100 &mgr;g/m3, and 11% exceeded the level considered to be Immediately Dangerous to Life and Health (IDLH) of 10,000 &mgr;g/m3. Even control workers who were not present at the burn exceeded the PEL (24%), likely due to legacy Hg contamination producing latent Hg releases to the atmosphere. Similarly, 86% of the miners at the burn and 59% of control workers had an 8‐h TWA that exceeded the Recommended Exposures Limit (REL). Several occupational behaviours that may contribute to Hg exposures were documented. This study corroborates previous studies suggesting that Hg exposure during amalgam burning is very high, and demonstrates the plausibility of using passive vapour monitoring badges rather than costly and logistically difficult biomonitoring methods. Mercury reduction and elimination interventions are strongly needed to reduce Hg exposure in ASGM communities, particularly as countries come into compliance with the Minamata Convention. HighlightsMeasures occupational exposure to mercury vapour in artisanal and small‐scale gold mining.Uses passive mercury vapour monitors, an economic alternative to biomonitoring.Extremely high levels of mercury exposure detected that exceed guideline values.Area air sampling with LUMEX supports the exposure levels measured by the passive samplers.Pertinent as a possible monitoring approach for Minamata Convention compliance.