Small-scale Mining Activities Research Articles

The Use of C-Band and X-Band SAR with Machine Learning for Detecting Small-Scale Mining

Illicit small-scale mining occurs in many tropical regions and is both environmentally and socially hazardous. The aim of this study was to determine whether the classification of Synthetic Aperture Radar (SAR) imagery could detect and map small-scale mining in Ghana by analyzing multi-temporal filtering applied to three SAR datasets and testing five machine-learning classifiers. Using an object-based image analysis approach, we were successful in classifying water bodies associated with small-scale mining. The multi-temporally filtered Sentinel-1 dataset was the most reliable, with kappa coefficients at 0.65 and 0.82 for the multi-class classification scheme and binary-water classification scheme, respectively. The single-date Sentinel-1 dataset has the highest overall accuracy, at 90.93% for the binary water classification scheme. The KompSAT-5 dataset achieved the lowest accuracy at an overall accuracy of 80.61% and a kappa coefficient of 0.61 for a binary-water classification scheme. The experimental results demonstrated that it is possible to classify water as a proxy to identify illegal mining activities and that SAR is a potentially accurate and reliable solution for the detection of SSM in tropical regions such as Ghana. Therefore, using SAR can assist local governments in regulating small-scale mining activities by providing specific spatial information on the whereabouts of small-scale mining locations.

Planning for the effective and sustainable management of Ghana’s artisanal small-scale gold mining industry

Over the years, artisanal small-scale mining (ASM) activities have been associated with unacceptable mining practices, which pose several health and environmental risks to communities and nations at large. Ghana is currently confronted with pollution of its main water bodies, which has reduced the supply of good quality water to the populace. To address these problems, several attempts - policy formulation, formalisation and introduction of technical assistance - have been undertaken by the government of Ghana and other international bodies such as United Nations Industrial Development Organisation-UNIDO. Despite these attempts, majority of artisanal small-scale miners are not registered and even some registered miners together with unregistered miners indulge in unacceptable mining practices. Premised on these, the study sought to undertake a thorough review of the challenges associated with the management of ASM in Ghana and provide a framework for the effective management of the sector. Consequently, a three-pronged approach (problem analysis, planning and implementation and enforcement) with a cross-cutting focus on monitoring and evaluation is recommended.

Impact of Small-Scale Mining Activities on Physicochemical Properties of Soils in Dunkwa East Municipality of Ghana.

The quality of soils in rehabilitated small-scale mined sites needs thorough investigation since a lot of changes do occur. The study assessed the impacts of small-scale mining activities on concentration and distribution of soil physicochemical properties and heavy metals. The soil samples were collected from 120 (50 m × 50 m) plots. The concentrations of soil physicochemical properties (Ca, Mg, Na, N, P, K, and OC and EC) varied significantly (p < 0.05) between unmined and mined soils. However, there were no statistically, significant differences (p < 0.05) observed in the concentrations of Cd, Hg, Pb, As, and Cu between the unmined and mined soils. Despite the generally poor (33.8%) soil quality in the study area, mining activities further reduced it by 24.2%. Soils from mined sites with unfilled/partially filled pits had higher levels of K, Mg, and Na. As mined sites fallow period increased, concentrations of OC and Cd increased, while Ca, Mg, pH, Cu, Pb, and As and value of EC decreased. The number of years that mined land remained fallow, and whether the pits were filled or unfilled during this period should be factored into the mined land rehabilitation processes.

Effect of small-scale illegal mining on surface water and sediment quality in Ghana

ABSTRACT In Ghana, small-scale mining (SSM) has been carried out for many years, generating employment and income. Currently, illegal artisanal mining (‘galamsey’) has impacted the environment negatively, resulting in land degradation and water pollution. The government of Ghana, responding to public outcry against the negative effects of ‘galamsey’, placed a ban on illegal small-scale mining activities in March 2017. This ban stopped both ‘legal’ small-scale and the illegal artisanal miners from carrying out any such activity. In July 2018, this study was carried out to examine the status of water and sediment quality in eight endemic regions of illegal mining to ascertain the outcome of the ban on the water quality of the rivers. Methodologies in the Standard Methods for the Examination of Water and Wastewater were followed. Results of the study indicated that the rivers were high in total suspended solids (TSS), turbidity and colour, suggesting inflow of wastewater from the illegal mining activities and some run-off. Colour had a strong correlation with turbidity (r = 0.95) and TSS (r = 0.94), suggesting that the pollution originates from the same sources. Low levels of metals were found in both water and sediment. However, very high concentrations of Fe were detected in both water and sediment. Mercury concentrations were low in the water column but relatively higher in the sediment. A comparison of the general water quality status of the water bodies in the Pra Basin in 2013 and 2018 using the Water Quality Index (WQI) showed a marginal improvement in quality in 2018 over 2013 in the Pra Basin. The improvement of water quality in 2018 is attributable to the ban.

Assessment of surface water quality and mercury levels from Artisanal and small-scale gold mining (ASGM) along Acupan River, Benguet, Philippines.

Artisanal and small-scale mining activities are most evident among communities surrounding the Acupan River in Itogon Benguet. The mining activities include manual extraction of gold ores, use of improvised ball/rod mills and sluice boxes, and metallurgical processing such as cyanidation, carbon-in-pulp (CIP) and amalgamation. This study evaluates the influence of small-scale mining and the geology/mineralization of the Acupan Au-Ag-Te deposit to the water quality of the Acupan River and to the possible human exposures to Hg within the small-scale mining community. Different water quality parameters were monitored along selected sites along the Acupan River for a year and the results showed that the low average values of dissolve oxygen (DO) (2.54-4.53mg L-1) and the relatively high average values of pH (8.84-10.10), sulfate (300.00-1133.33mg L-1), nitrate (11.33-134.67mg L-1), arsenic (As) (0.227-0.574mg L-1) and mercury (Hg) (0.004-0.054mg L-1) have exceeded the acceptable criteria limit of the Department of Environment and Natural Resources for Class C waters. The exceeded values are noted to occur in areas where extensive small-scale mining activities are being done and have affected as well the downstream areas. To test possible human contamination in the use of Hg, hair samples from 56 volunteers were analyzed for total Hg (T-Hg) following standard protocols. The T-Hg concentrations in hair samples are mostly inorganic and are determined in various parameters such as sex, geographic location, occupation, age, fish consumption and localization in hair. Though not significantly different, higher Hg values are noted in males (1.280 ± 0.446ngmg-1) than among females (0.651 ± 0.163ngmg-1) as well as those with ages 41-50years (3.130 ± 2.330ngmg-1) as compared to other age groups. The higher amounts of inorganic Hg in human hairs could be attributed to the discrete yet prevalent use of amalgamation. The findings of this study emphasize the need for better regulations of the small-scale mining activities and for stricter implementation of the total ban on the use of Hg in ore processing to ensure better water quality of Acupan River as well as the health and safety of the communities surrounding the river.

Assessing the impacts of artisanal mining on the quality ofvf South-western Rivers System in Ghana.

Artisanal small-scale mining has been part of Ghana's history, but recent public outcry on the devastating impacts of the phenomenon on water bodies, due to expansion in the sector, has led to clamp downs by various governments on the activity. This has called for evaluation of the water quality of the South-western Rivers System, which are small-scale mining endemic areas. Thirty-five river samples were collected in July 2018 and were analyzed for physico-chemical parameters using procedures outlined in the Standard Methods for the Examination of Water and Wastewaters. The results revealed that the rivers are polluted with Fe and Cu, accompanied by very high levels of turbidity (mean = 488 NTU) and total suspended solids (TSS) (mean = 382mg/L). NH3-N, PO4-P, BOD, and DO levels indicated mild pollution in the waters. Pollution of the rivers is attributable to impacts of artisanal small-scale mining, surface run-off as a result of high intensity rainfall, anthropogenic (indiscriminate waste disposal) and geogenic factors such as dissolution of minerals from the soil zone. It was observed that, if not strictly regulated, turbidity and TSS levels arising mainly from illegal small-scale mining activities could lead to shutdowns of a number of Ghana Water Company Limited treatment plants, leading to water supply challenges in the study area.

Artisanal and small-scale mining activities as post-mining land use in abandoned mine sites: a case of Giyani and Musina areas, Limpopo Province of South Africa

South Africa has many artisanal and small-scale mining (ASM) activities that some are registered and others informal and illegal. This paper presents an overview of ASM operations in the vicinity of abandoned mine sites found in Giyani and Musina areas, Limpopo Provine of South Africa. It looks at the mining processes, environmental problems, and health and safety risks of ASM in the area. It also provideds a discussion of practical ways of dealing with the problems of artisanal and small-scale mining operations in a harmonized way with the rehabilitation of the abandoned mine sites. The exploitation of waste rock dumps for aggregate production in Musina demonstrated that formalized ASM activities can be the best alternative uses of the abandoned mine sites. However, artisanal gold mining around Giyani revealed the health and safety risks and environmental problems of these operations. The artisanal gold mining activities worsened the health and safety and the environmental problems of the abandoned mine sites. Therefore, this paper recommends that the efforts of coming up with strategies to formalize and regulate artisanal mining in South Africa be deepened for these activities to be accepteble as sustainable as post-mining land-uses in abandoned mines.

The Socio-Economic Implications of Artisanal and Small-Scale Mining on Mining Communities in Northern Ghana

Small-Scale Mining (SSM) predates Large-Scale Mining (LSM) in Ghana but was relegated to the background in the 1980s following the Economic Reforms and Structural Adjustment Programmes which heavily liberalized the mining sector. Conversely, the small-scale mining sector continues to boom attracting a large chunk of the labour force in the mining sector. The small-scale mining sector has affected the livelihoods of several thousands of people especially those living in mining communities across the country. This study sought to ascertain the impact of small-scale mining on the livelihoods of people living in mining communities in the Northern Ghana. The study aimed at examining the socio-economic effects of artisanal and small-scale mining on the mining communities in northern Ghana. The approaches that were used to gather and analyse the data for the study included qualitative and quantitative research approaches. The study shows that the impact of small-scale Mining activities on livelihoods has been both positive and negative. It is recommended that small-scale mining firms should be required by law to introduce Alternative Livelihood Programmes or Interventions in the communities where they operate. Thus, communities can cope with the adverse effects of mining activities on their livelihoods.

Effect of home processing methods on the levels of heavy metal contaminants in four food crops grown in and around two mining towns in Ghana.

Unregulated small-scale mining activities, by young untrained men using some poisonous chemicals, occur in several agricultural forest belts in Ghana. These activities contaminate water bodies in these areas, which happen to be the main farming sites where food crops are intensively cultivated. The presence of these heavy metal contaminants in popular food staples is therefore worrying because of its adverse health implications. Previous studies have shown that processing is able to decrease the concentrations of heavy metals in foods. This study investigated the effectiveness of home processing methods (boiling, frying and roasting) in significantly reducing the levels of heavy metal contaminants in food crops grown in and around two main mining centers in Ghana. The heavy metals contaminants analyzed for, were Arsenic (As), Cadmium, (Cd), lead (Pb), Manganese (Mn), and Mercury (Hg), determined using atomic absorption spectrometry (AAS) and inductively-coupled plasma mass spectrometry (ICP-MS). From the data, the average daily intakes of the heavy metals and the associated long-term health risks to consumers were assessed. Unprocessed samples from Akwatia had higher levels of contaminants than those from Obuasi. Levels of Mn, Pb and As recorded in all unprocessed samples were higher compared to WHO permissible limits in foods. The levels showed a decreasing trend in the processed samples; with the lowest As and Pb content recorded after frying and boiling. The study showed that roasting allowed for the least reduction in the heavy metal contaminations in the four food crops. The levels of Cd in both processed and unprocessed samples were within safe WHO specifications. Except for Pb in unprocessed cassava, boiled cassava and unprocessed plantain and Hg (unprocessed yam and roasted yam), the hazard indices of all metals in all food crops were less than one and posed no risk to consumers. The study therefore reveals that the normal home processing methods are able to reduce the levels of heavy metal contaminants found in cassava, cocoyam, plantain and yam considerably.

Effects of Illegal Mining on the Environment, Economy, and Agricultural Productivity

The mining of minerals has contributed enormously to most African countries' economies. However, the activities involved in these sectors have turned to hunt our environment and human life due to the lack of regulation in this sector. This paper is a review of the effects of illegal mining on the environment, the economy and agricultural productivity in Ghana. The review employed key word findings at the initial stage to obtain relevant articles; peer-reviewed and non-reviewed articles, both published and non-published and other articles from reputable media sources. The findings from the study revealed that in Ghana, just like most African countries, artisanal and small-scale mining has contributed positively to the economy through job creation, increased mineral output, specifically gold, and concurrently increased the GDP of the country. Nonetheless, the downsides of unregistered and unregulated small-scale mining activities overshadow the benefits derived from it. Notable negativities associated with artisanal and small scale mining include: loss of mineral revenue through smuggling, food insecurity, destruction to surface and underground water through toxic contamination and pollution caused by mud and sediments, air and noise pollution and destruction of biodiversity, including the natural flora and fauna and water species. Death, injuries, respiratory and skin diseases, noise-induced hearing loss, physical and psychological stress, malaria, and HIV are among the common legacies of illegal mining. Among other recommendations, the study suggests that perpetrators found in illegal mining activities should be duly dealt with according to law. Also, small-scale mining concessions duly registered and regulated should be demarcated to avoid encroachment into forest reserves, farmlands, and river courses.

HEAVY METALS CONTAMINATION AND DISTRIBUTION IN SURFACE WATER AND SEDIMENT OF THE ABOABO STREAM, AHAFO REGION, GHANA

Activities of illegal small-scale miners promote continual introduction of wide pollutants into the Aboabo stream. Their toxicity poses health threats to the inhabitants of Krapoo village in the Ahafo Region, Ghana. The study assesses the impacts of illegal small-scale mining activities on the water quality of the stream. Levels of physico-chemical and microbiological parameters were determined using standard methods. Samples of sediment, water and plant were acid-digested with aqua-regia. Total Arsenic and Total Cadmium were analysed using Flame Atomic Absorption Spectrophotometer (FLAAS) whiles Total Mercury was analysed using Cold Vapour Atomic Absorption Spectrophotometer (CV-AAS). Turbidity, faecal coliforms and E-coli readings exceeded permissible limit of 5NTU and 0MPN/100ml respectively by Ghana’s Environmental Protection Agency (GS 1212) and World Health Organisation (WHO). Temperature, Electrical Conductivity and pH values were within the limit of &lt;30oC, 1500μs/cm and 6.5-85 respectively at both seasons. Total suspended solids readings at the midstream were higher than the permissible limit. However, levels of total dissolved solutes and dissolved oxygen recorded, were below the limit. The sediments were also heavily polluted with Mercury, Arsenic and Cadmium. Alchornea cordifolia, Chromolaena odorata and Spigella anthelmia growing within the stream were taken to assess their efficiency in removing the heavy metals from the stream. It was observed that the plants species had bioaccumulation factor (BF) greater than 1 for cadmium. Alchornea cordifolia was the only plant with BF greater than 1 for mercury. The plants species are potential hyper accumulators for mercury and cadmium hence are suitable for phytoremediation.

Artisanal and small-scale mining, and COVID-19 in sub-Saharan Africa: A preliminary analysis

This article offers preliminary reflections on the potential impact of COVID-19 on artisanal and small-scale mining (ASM) activities – low-tech, labor-intensive mineral extraction and processing – in sub-Saharan Africa. In doing so, it revisits the core ideas put forward in the literature in support of showcasing the sector more prominently in the region’s rural development strategies. For decades, scholars have been gathering evidence that points to ASM being the most important rural nonfarm activity in sub-Saharan Africa, as well as how, in providing a supplementary source of income, the sector helps millions of the region’s impoverished farm-dependent families cope with unexpected economic stresses and shocks. Sub-Saharan Africa has managed to avoid high numbers of COVID-19 infections and deaths thus far but it has already felt the economic impacts of the pandemic, perhaps nowhere more than in its remote rural areas, which are already poverty-stricken and produce food at mostly subsistence levels. Intensifying support for ASM, an economic activity which again, many rural Africans are already involved in and familiar with the benefits it provides, in rural development and adaptation plans linked to COVID-19, should be prioritized by the region’s governments and donors. Findings from ongoing research in Mali, Liberia and Ghana – the locations of three of the largest and most dynamic ASM economies in sub-Saharan Africa – reveal that despite its proven ability to stabilize and catalyze development in the region’s rural economies, that even this sector has been affected by COVID-19. They more importantly shed light on how the pandemic has impacted ASM-dependent communities, and importantly, offer clues on how to make the sector more robust and better position it to steer rural communities through the crisis.

Investigating the Potential of Radar Interferometry for Monitoring Rural Artisanal Cobalt Mines in the Democratic Republic of the Congo

Greater awareness of the serious human rights abuses associated with the extraction and trade of cobalt in the Democratic Republic of the Congo (DRC) has applied increasing pressure for businesses to move towards more responsible and sustainable mineral sourcing. Artisanal and small-scale mining (ASM) activities in rural and remote locations may provide heightened opportunities to conceal the alleged human rights violations associated with mining, such as: hazardous working conditions, health impacts, child labour, child trafficking, and debt bondage. In this study, we investigate the feasibility of the Intermittent Small Baseline Subset (ISBAS) interferometric synthetic aperture radar (InSAR) method, teamed with high temporal frequency Sentinel-1 imagery, for monitoring ASM activity in rural locations of the “Copperbelt”, the DRC. The results show that the ISBAS descriptive variables (mean, standard deviation, minimum, and maximum) were significantly different (p-value = ≤ 0.05) between mining and non-mining areas. Additionally, a significant difference was found for the ISBAS descriptive variables mean, standard deviation, and minimum between the different mine types (industrial, surface, and tunnels). As expected, a high level of subsidence (i.e., negative ISBAS pixel value) was a clear indicator of mine activity. Trial activity thresholds were set for the descriptive variables mean (-2.43 mm/yr) and minimum (-5.36 mm/yr) to explore an ISBAS approach to active mine identification. The study concluded that the ISBAS method has great potential as a monitoring tool for ASM, with the ability to separate mining and non-mining areas based on surface motion values, and further distinguish the different mine types (industrial, surface, and tunnel). Ground data collection and further development of ISBAS analysis needs to be made to fully understand the value of an ISBAS-based ASM monitoring system. In particular, surrounding the impact of seasonality relative to longer-term trends in ASM activity.

Condemned to the periphery: The lived experiences of women in artisanal gold mining activities in Karamoja sub-region, Uganda

This paper explores the lived experiences of women in artisanal gold mining activities at Lolung and Chepkararat mines in Karamoja, north-eastern Uganda. It reports on the results of a study based on a qualitative research design, with data collected through key informant interviews, site observations, and focus group discussions. Although artisanal gold mining provides women with diverse opportunities, including employment and possibilities to earn an income, our results suggest that most of the lucrative mining opportunities are not available to them. Rather, the majority of women are engaged in undervalued, less-lucrative, and less-remunerated but labour-intensive support work that mirrors their domestic household routines. This contributes to their marginalization in society. Moreover, socio-cultural and customary moralities and practices are continually manipulated thereby legitimizing the exclusion of women from specific mining activities. We suggest that broadening the everyday resistance mechanisms of women miners, alongside the formalization of artisanal and small-scale mining (ASM) activities, reinforced with affirmative action and education, could gradually reverse the marginalization of women in gold mines and contribute to their meaningful engagement in mining.

Perception of Small-Scale Miners on Interventions to Eradicate Illegal Small-Scale Mining in Ghana

The proliferation of illegal mining in Ghana, coupled with its environmental impacts, especially on water bodies has compelled the government to ban all artisanal small-scale mining (ASM) activities in the country. The ban is intended to promote environmental sustainability while the government takes steps to provide sustainable health, and environmental-friendly ASM in Ghana. This paper assesses the perception of registered miners on the current approach by the Ghanaian government to stop illegal mining. Analyses of data from focus group discussions and key informant interviews revealed that the miners felt “left out” of the entire process. They maintained that they were not directly involved in the process to ban illegal mining in Ghana. To them, the proliferation of illegal mining in Ghana is the result of non-performing government institutions, corruption, and cumbersome licensing procedures. The article calls for improvement in the collaboration between the government and miners through a simplified participatory framework for the management of ASM in Ghana.

Heavy Metals in the Soils of Placer Small-Scale Gold Mining Sites in Myanmar.

Background.Artisanal and small-scale mining activities are widely practiced globally. Concentrations of heavy metals associated with gold, such as copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) can increase in the environment as a result of mining activities, leading to environmental pollution and pose toxicity risks to humans and animals.Objectives.The aim of the present study was to investigate soil concentrations of toxic heavy metals in placer small-scale gold mining operations in Myanmar.Methods.Soil samples were collected from three placer small-scale gold mining sites: Site A located in the Hmawbon public protected forest, Site B and Site C, situated in the Nant-Kyin reserved forest around Nar Nant Htun village. At each site, soil samples were collected from four gold mining stages (ore processing, sluicing, panning, and amalgamation). Atomic absorption spectroscopy was utilized to examine the concentrations of As, Cd, Pb, and Hg.Results.The highest heavy metal concentrations were generally found in the amalgamation stages across all the gold mining sites. Across the three mining sites, the maximum heavy metal concentrations in the amalgamation stage were 22.170 mg.kg−1 for As, 3.070 mg.kg−1 for Cd, 77.440 mg.kg−1 for Hg, and 210.000 mg.kg−1 for Pb.Conclusions.The present study examined the concentrations of As, Cd, Hg and Pb in the soil of several small-scale gold mining sites in Banmauk Township, Myanmar. The results demonstrated the presence of high concentrations of heavy metals in the soil of the gold mining sites. Miners in this area work without proper personal protective equipment, and frequent exposure to heavy metals in the soil may cause adverse health effects. The present study provides baseline data for future risk assessment studies of heavy metal contamination in gold mines.Competing Interests.The authors declare no competing financial interests

Land, labour and capital: Small and large-scale miners in Papua New Guinea

This paper provides the first detailed characterisation of the interface dynamics between artisanal and small-scale mining (ASM) and large-scale mining (LSM) activities in Papua New Guinea, recently termed ‘ASM-LSM interfaces’. We characterise these interfaces across the project lifecycle at operational, non-operating, and future mines. Despite industry commitment to contemporary standards for social responsibility, our study shows that large-scale miners actively co-construct ASM-LSM interfaces and contribute to their intensification, which often results in violence, dispossession, and entrenched inequalities. By focussing on interfaces, we identify the influences and effects on the underlying elements that small and large-scale mining activities have in common, namely land, labour and capital. This provides the basis to chart the ‘mining encounters’ among the host of actors entangled in these extractive zones, and the competing interests that arise at each resource conjuncture.

Shifting sands: Legal dispossession of small-scale miners in an extractivist era

This article argues that the entanglements of a growing global demand for construction material and neoliberal resource governance result in an incremental and piecemeal form of dispossession. While mining in Colombia has been broadly researched, little has been said about sand extraction and the challenges small-scale artisanal miners face when trying to formalise their activities. This article seeks to fill this gap by following a group of areneros (manual sand extractors) who attempt to defend their right to sand extraction against a competing mining claim. Drawn into the domain of the state, the areneros navigate a changing institutional setup and a complex legislation that favours the wealthy, the lettered and the connected. Political-economic interests are masked behind procedures, symbols and legal-administrative means, which create a ‘state effect’ and result in a subtle form of legal dispossession. The article points towards a scalar model of dispossession, in which small-scale mining activities pass through ‘small-scale intermediaries’ to end up in the hands of private corporate actors with capital and technical expertise to conduct large-scale extraction. The article adds to the limited literature on sand extraction and challenges the view that the activity is merely conducted by criminal actors; yet, it argues that subsistence mining is under threat by government and corporate interests, positioning sand extraction as a new resource frontier. As small-scale miners find themselves in the conflict between two competing rights regimes and two competing production logics, they are doubly stretched between proletarianization and eviction, criminalisation and self-erosion.

Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.

Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.