2e: Artisanal Small-scale Gold Mining (ASGM): Current and historical emissions, current practices and future projections

In developing countries across Asia, South America, and sub-Saharan Africa, mercury is utilized to isolate gold from sediment in artisanal mining, the largest anthropogenic source of mercury emissions. This mercury is then released into the environment either through local atmospheric emissions or as mining tailings, presenting a health risk for humans and biota. Though many studies have examined the health impacts of the mercury vapor, little is known about the fate of local mining waste, including the extent of contamination and its pathway of loss, especially in sub-Saharan Africa. In this study, we examine mercury from artisanal gold mining in southeastern Senegal. This region currently produces over 4 million tons of gold per year, while releasing over 5 tons of mercury into the atmosphere; these values are expected to increase in the future. We examine the ecological impact of artisanal gold mining using soil, water, and sediment samples collected from three mining communities to determine the pathway of mercury into the environment. We assess patterns in total mercury and methylmercury concentrations in huts where mercury is burned, piles of mine tailings, and along transects to the nearby streams. We utilize these patterns to gain insight into biotic and human exposure to mercury both in the mining villages and downstream communities. We will present data on the implications of this contamination for ecosystems.

Mercury, the only liquid metal element at ambient temperature and pressure, has a low boiling point (357 ℃). Therefore, mercury evaporates easily at ambient conditions and is readily emitted from various sources. In 2010, the majority of global anthropogenic emissions of mercury to the atmosphere were associated with artisanal and small-scale gold mining (37.1 %).

One of the gold mining activity area in Barito river watershed is located in Mangkahui Village, Murung sub District, Murung Laya Regency which approximately 470 km apart from Palangkaraya city, the capital city of Central Kalimantan. Gold processing plants are located at the center of the Mangkahui Village. There were fifteen gold processing plants constructed along the main road in the village (within 500 m) which consists of 10 to 24 steel-made ball mills at every single processing plant which employees 30 to 40 workers.

Mercury concentration in atmosphere, water and soil were observed in the ASGM activity sites. We also observed the mercury concentration in fish and rice. Based on our field observation, we conducted human health risk assessment originated from ASGM activity. Health risk assessment was conducted by the Hazard Quotient (HQ) and Hazard Index(HI) which is provided by the US EPA.

Exposure to even small amounts of mercury (Hg) can cause serious health problems in people. Therefore, many assessments of mercury exposure levels in various countries have been conducted during recent decades. Mongolia is a mining-rich country that in 2000 earned approximately equal amounts of export revenue from mining and livestock. Increasing large-scale and rampant small-scale mining activity in Mongolia is raising fears about the possibility of regional environmental pollution. River water and atmospheric mercury were collected between 26 August and 7 September 2014. In this region the people who engaged mercury mining was called as Ninja. With the hearing survey, they said mercury is not used in their mining area however, high mercury concentration (1,300 ng/L) in river water was observed. In addition, high mercury concentration in the atmosphere is also observed. Based on our results, we conducted human health risk assessment (Hazard Quotient, Hazard Index) which is provided by the US EPA. Result from the risk analysis, not only the people who worked near the mining activity site but also residents near the mining site may at risk.

Mercury (Hg) is one of the most harmful pollutants. The release of this metal into the environment from gold mining activities represents a risk to human health and the ecosystem. The aim of this study was to assess the levels of total Hg (T-Hg) in human hair and several environmental matrices within the Biogeographic Choco area, at the Colombian Pacific region. Total Hg levels were measured using pyrolysis coupled with atomic absorption spectrometry. The median T-Hg level in human hair samples from Quibdo, Choco´s most populated city, was 1.36 μg/g (range: 0.02-116.4 μg/g), whereas in Paimado, a place near gold mining operations on the Quito River, an affluent of Atrato River, it was 0.67 μg/g (range: 0.07-6.47 μg/g). In Quibdo, air samples within gold shops displayed Hg concentrations two orders of magnitude greater than those found in reference sites. Although extensive gold mining activities are carried out in several affluents of Atrato River, sediment samples from places along the river stream showed relatively low levels of T-Hg, probably because of high flow conditions due to abundant rainfall present all year-round. However, it is clear that Hg released from gold extraction is spread through the ecosystem, as T-Hg levels were found to increase according to the trophic level of examined fish species. In some carnivorous fish, average T-Hg concentrations were above international guidelines, especially in Pseudopimelodus schultzi, Ageneiosus pardalis, Sternopygus aequilabiatus, Rhamdia quelen and Hoplias malabaricus, whereas low T-Hg levels were registered in Cyphocharax magdalenae and Hemiancistrus wilsoni. In short, the use of Hg in gold mining in this region of Colombia is causing its bioaccumulation in wildlife and humans, threatening biodiversity and human health.

The distribution of total mercury (T-Hg) and organic mercury (org-Hg) in the soil around the artisanal and small-scale gold mining (ASGM) area along the Cikaniki River was investigated. The soil samples were collected from two sites in the forest near the ASGM village and four sites in the national park, approximately 13 km upstream from the ASGM village. The samplings were conducted in March and August 2014. At each site, after the fallen leaves and branches were collected, the soil samples were collected every 2 cm from the surface up to a depth of 20 cm. The samples were placed in plastic bags with seals and brought back to laboratory. The samples were freeze-dried, ground with agate mortar, and used for determination of T-Hg and org-Hg concentrations, total organic carbon (TOC) and total nitrogen (TN) contents, and chemical composition of the soil. The T-Hg concentration was measured by cold vapor atomic absorption spectrometry (CVAAS) after nitric, perchloric, and sulfuric acid digestion of the samples. The org-Hg was extracted from solid samples using hydrochloric acid/toluene/L-cysteine and measured through CVAAS after mixed acid digestion in the same manner as that for T-Hg. The average concentrations of T-Hg in the forest soils of national park and those near the ASGM village were 1.1 mg kg1 and 1.4 mg kg-1, respectively. The average concentrations of org-Hg in these areas were 3.2 mg kg1 and 3.0 mg kg1, respectively. The average concentrations of T-Hg in the fallen leaves collected from these areas were 1.1 mg kg1 and 4.9 mg kg1, respectively. The T-Hg concentration in the soil varied with depth tending to show the highest values at the surface or the layers several centimeters from the surface. The org-Hg and TOC contents showed similar vertical variations as that shown by T-Hg, except for the near-surface layers containing TOC greater than 30%. A linear relations were observed among TOC, T-Hg and org-Hg for the samples containing TOC smaller than 30%. From the relation between TOC and TN, it was suggested that the samples having TOC greater than 30% contain insufficiently decomposed fallen leaves. The mercury discharged into atmosphere by mining activities is transported to a remote site and causes an increase in the mercury concentration at the surfaces by deposition. The mercury deposited on the surfaces can be trapped and retained by organic matter and then subjected to methylation with the decomposition of the organic matter.

Mercury and cyanide interaction in the aquatic environment of gold mining communities, increases the solubility of mercury. This causes Hg to be highly bioavailable for methylation. Hence, cyanidation and amalgamation techniques adopted respectively by Large Scale (LSGM), and, Artisanal and Small-Scale (ASGM) gold miners in Southwestern Ghana makes it imperative to investigate the levels of methylmercury in Hg-contaminated aquatic environments loaded with cyanide. Total and Methylmercury levels in sediments from Rivers Aprepre and Ankobra located in the Prestea-Huni Valley district of Southwestern Ghana have been investigated. Total mercury content was determined by CV-AAS after acid digestion with HF/HNO3/HCl. Extraction of MeHg from sediment was achieved using H2SO4/KBr/CuSO4 and methylene chloride. This was followed by aqueous phase propylation coupled to purge and trap -GC-AFS detection. MeHg in sediments from River Aprepre (known to receive effluent from both ASM and LSM) varied between 6.11 to 14.83 ng/g (2.5-3.7% of THg), whilst THg ranged from 241 to 405 ng/g dry mass. MeHg in sediments from River Ankobra (which is further away from cyanide exposure) ranged from 0.09 to 0.24 ng/g (0.08-0.12% of THg), with total mercury (THg) varying from 76 to 307 ng/g dry mass. Further investigation on temperature fractionation and water solubility (Milli-Q water and Rain water) is on-going to identify the various mercury compounds, and the water-soluble Hg compounds respectively to aid the verification of the MeHg levels in the sediments from the two Rivers. Temperature fractionation is being carried out with a Jozef Stefan Institute in-house designed apparatus; which consist of CV-AAS detector (Lumex, RA-915+), Pyrolytic cell, Pyro-915+ pump, tube furnace etc. Results from these experiments would be presented.

Southeast Asia has experienced a tremendous upsurge in Artisanal and Small-scale Gold Mining (ASGM) and other surface mining in recent decades, leading to concerns over environmental and human health impacts, particularly associated with widespread use of mercury (Hg) in ASGM. Researchers, conservationists and government authorities need ways to quickly identify the magnitude and extent of land/water areas impacted directly or indirectly by ASGM and other surface mining to assess priorities for further investigation, particularly regarding mercury use and its impacts on environmental and human health.

This poster presents results of a rapid assessment of ASGM and other surface mining disturbance in important watersheds in Indonesia, Laos (Lao PDR) and Myanmar where mining has proliferated over the past two decades, conducted through systematic visual search of imagery (available as of May 2017) in Google Earth Pro 7.1.8.3036 (GEP). This approach allows rapid identification of areas impacted by mining, thereby providing an information baseline for planning research, monitoring and conservation.

The rapid assessment approach uses typical visual characteristics of ASGM and other surface mining disturbance (e.g., changes in spectral reflectance of ground surface from primarily green to white, beige or brown associated with removal of canopy vegetation cover and excavation, presence of small- to medium-sized pits filled with water of different colors (e.g., green, turquoise), discoloration of watercourses) as a search image for use in searching imagery. Searching begins with watercourses as top priority and systematically expands to other areas (e.g., plateaus, mountains) that are likely to have mining impacts. Caveats of the approach are that it is not 100% accurate—areas can be missed and misidentified—and does not provide a quantitative estimate of area impacted by mining.

The rapid assessment approach was used to assess ASGM and other surface mining disturbance in: (1) Batang Hari River watershed, Jambi Province, Sumatra, Indonesia; (2) Sekong River watershed, Attapeu and Sekong Provinces, Laos; and (3) Upper Ayeyarwaddy River and Chindwin River watersheds, Myanmar. Results are presented. Each case study also had a unique component. The Myanmar study compared rapid assessment results to results in an existing database. The Sumatra study traced development of mining by analyzing historical imagery in GEP. The Laos study attempted to quantify mining areas in one subwatershed using draw tools in GEP.