Integrated Assessment of Artisanal and Small-Scale Gold Mining in Ghana—Part 2: Natural Sciences Review

This paper is one of three synthesis documents produced via an integrated assessment (IA) that aims to increase understanding of artisanal and small-scale gold mining (ASGM) in Ghana. Given the complexities surrounding ASGM, an integrated assessment (IA) framework was utilized to analyze socio-economic, health, and environmental data, and co-develop evidence-based responses with stakeholders. This paper focuses on the causes, status, trends, and consequences of ecological issues related to ASGM activity in Ghana. It reviews dozens of studies and thousands of samples to document evidence of heavy metals contamination in ecological media across Ghana. Soil and water mercury concentrations were generally lower than guideline values, but sediment mercury concentrations surpassed guideline values in 64% of samples. Arsenic, cadmium, and lead exceeded guideline values in 67%, 17%, and 24% of water samples, respectively. Other water quality parameters near ASGM sites show impairment, with some samples exceeding guidelines for acidity, turbidity, and nitrates. Additional ASGM-related stressors on environmental quality and ecosystem services include deforestation, land degradation, biodiversity loss, legacy contamination, and potential linkages to climate change. Though more research is needed to further elucidate the long-term impacts of ASGM on the environment, the plausible consequences of ecological damages should guide policies and actions to address the unique challenges posed by ASGM.


Table of Contents
Total mercury (Hg) levels in soils near Ghanaian small-scale gold mining sites and reference non-mining sites.
1 Table S2 Total mercury (Hg) levels in edible plants near Ghanaian smallscale gold mining sites.
5 Table S3 Total mercury (Hg) levels in sediment near Ghanaian small-scale gold mining sites and reference non-mining sites.
7 Table S4 Total mercury (Hg) levels in water near Ghanaian small-scale gold mining sites and reference non-mining sites.
11 Table S5 Total mercury (Hg) levels in fish and shellfish in Ghana and the Gulf of Guinea.
15 Table S6 Total mercury (Hg) levels in lichen and seaweed bioindicators and tailings in Ghana and from the Gulf of Guinea.
22 Table S7 Total arsenic (As) levels in soils near Ghanaian small-scale mining sites and reference non-mining sites.
25 Table S8 Total arsenic (As) levels in edible plants near Ghanaian small-scale mining sites and reference non-mining sites.
26 Table S9 Total arsenic (As) levels in sediment near Ghanaian small-scale mining sites and reference non-mining sites.

27
Table S10 Total arsenic (As) levels in water near Ghanaian small-scale mining sites and reference non-mining sites.
28  Data has been extracted from a book chapter that was contributed to by the authors.
Dumasi area (soil from a miner's house with roasting activity), Wassa West District, Western Region Data has been extracted from a book chapter that was contributed to by the authors.
1 Table S1. Total mercury (Hg) levels in soils near Ghanaian small-scale gold mining sites and reference non-mining sites. ND = Not detectable or below the detection limit. This work was carried using the atomic absorption spectrum. Results were compared with literature and found to be consistent. Surface soil samples (0-10 cm) collected close to the main River Ankobra and its major tributaries at Ankobra, Bonsa, Subri, Beppoh, Bawdie, Terebebie, and Efuanta.

-2007
Samples were collected monthly (for 10 months; Sep. 2006 to Jun. 2007) from farms sites where large and small-scale mining occurs, at three depths (0-5cm, 10-15cm, and 25-30cm). [3] Table S1. Total mercury (Hg) levels in soils near Ghanaian small-scale gold mining sites and reference non-mining sites. ND = Not detectable or below the detection limit.  [10] Samples taken from a refinery in Bolgatanga in August 2012 from the top 1-2 cm of soil. Samples were collected from within the refinery and at 3 and 6 meters away.

River Pra Basin, Western, Central & Ashanti Regions
Samples taken from the Rivers Offin, Upper Pra and Lower Pra, once in the wet & dry season each. [8] Table S1. Total mercury (Hg) levels in soils near Ghanaian small-scale gold mining sites and reference non-mining sites. ND = Not detectable or below the detection limit.    Data has been extracted from a book chapter (12) that was contributed to by the authors of the article. Samples were collected in the wet and dry seasons of the year to observe the variation in (total) mercury levels during these two major seasons.  Data from 2 bridge sites on the river (Twifo Praso, Praso) colected once per month in July, Aug., Sept. and Feb. Nine samples were collected at each bridge site--6 analyzed in a lab and 3 analyzed with a Hg thermometer in the field--at 0.8 and 2 m depths. Data from 1 bridge site on the river colected once per month in July, Aug., Sept. and Feb. Nine samples were collected at each bridge site--6 analyzed in a lab and 3 analyzed with a Hg thermometer in the field--at 0.8 and 2 m depths.    [8] Table S5. Total mercury (Hg) levels in fish and shellfish in Ghana and the Gulf of Guinea. Hg concentrations are presented in wet weight (dry weight values were converted to w.w. assuming 80% moisture [32] Samples collected from commercial catches from fisherman in villages along the reservoir from Feb. through Dec. Fish Table S5. Total mercury (Hg) levels in fish and shellfish in Ghana and the Gulf of Guinea. Hg concentrations are presented in wet weight (dry weight values were converted to w.w. assuming 80% moisture [32]             Reference sites: Non-mining locations [47] [47] [22] Table S10. Total arsenic (As) levels in water near Ghanaian small-scale mining sites and reference non-mining sites. ND = Not detectable or below the detection limit. [52] [53] Samples collected in June and July 2011 from drinking water sources cited by ASGM community members.

Study Location
Table S10. Total arsenic (As) levels in water near Ghanaian small-scale mining sites and reference non-mining sites. ND = Not detectable or below the detection limit.

Study Location
Year collected Reference sites: Non-mining locations [22] [54] Table S10. Total arsenic (As) levels in water near Ghanaian small-scale mining sites and reference non-mining sites. ND = Not detectable or below the detection limit.        Fruit was harvested from 6 farms, and 10 fruits were harvested from each tree. Kumasi data is control.

Study Location
Fruit was harvested from 6 farms, and 10 fruits were harvested from each tree.
Fruit was harvested from 6 farms, and 10 fruits were harvested from each tree. 1991 1991 1991 Reference sites: Non-mining locations -Table S18. Total lead (Pb) levels in water near Ghanaian small-scale mining sites and reference non-mining sites. ND = Not detectable or below the detection limit.

Study location
Year collected  Samples from 8 sites at the Pompora Treatment Plant (the old pyrometallurgical pre-treatment plant). Samples were all below detection limit (10 µg/L).

Stream Surface water
Samples collected in June and July 2011 from drinking water sources cited by ASGM community members.
Surface water [54] [52] Table S19. Guidelines and standards for mercury (Hg) in ecological media. Data are reviewed by the number of sampling sites exceeding guideline values for total, mining (ASGM and/or LSGM), and non-mining sampling sites. US EPA [59,60] FAO/WHO [61] US EPA [62] n sampling sites* Mercury (Hg) Standard Table S20. Guidelines and standards for arsenic (As) in ecological media. Data are reviewed by the number of sampling sites exceeding guideline values for total, mining (ASGM and/or LSGM), and non-mining sampling sites.