Mining Catchment Research Articles

Anthropogenic legacy sediment budgets in heavily disturbed historical mining catchments

Unregulated metal mining mobilises high volumes of waste sediments to river systems within impacted catchments, increasing sediment yields, contaminating floodplain stores, and profoundly altering long-term patterns of channel planform evolution. However, quantifying the actual scale of historical mine sediment production and dispersal remains a significant challenge, due largely to the variable quality, character and availability of disparate datasets relating to past mining operations. In this study, we reconstruct anthropogenic sediment production associated with historical lead mining between 1700 and 1948 for a globally significant orefield in the North Pennines, UK, that includes the headwater catchments of two major river systems: the River South Tyne and the River Tees. Using a range of interdisciplinary methods including digital terrain analyses and ore-to-waste sediment scaling ratios, we find that mining produced 4.4 × 105 t of lead ore during the study period, but also mobilised an estimated 7.2 × 106 t of associated waste sediment. Approximately 67 % of this waste sediment cannot be accounted for within extant anthropogenic sediment storage landforms within the catchment areas. Surface working using managed water supply (hushing) was the key sediment production process, with 64 % of waste sediment originating from surficial hushing but only 36 % from subterranean mining. The high connectivity of hushes with river channels resulted in minimal (<1 %) long-term sediment storage in the form of hush outwash fans. We find pronounced spatial and temporal variability in legacy sediment production and storage, which has important implications for understanding reach-scale patterns of channel response to historic mining operations.

Organic-mineral colloids regulate the migration and fractionation of rare earth elements in groundwater systems impacted by ion-adsorption deposits mining in South China

Ion-adsorption rare earth element (REE) deposits distributed in the subtropics provide a rich global source of REEs, but in situ injection of REEs extractant into the mine can result in leachate being leaked into the surrounding groundwater systems. Due to the lack of understanding of REE speciation distribution, particularly colloidal characteristics in a mining area, the risks of REEs migration caused by in situ leaching of ion-adsorption REE deposits has not been concerned. Here, ultrafiltration and asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4-ICP-MS) were integrated to characterize the size and composition of REEs in leachate and groundwater from mining catchments in South China. Results show that REEs were associated with four fractions: 1) the <1 kDa fraction including dissolved REEs; 2) the 1 – 100 kDa nano-colloidal fraction containing organic compounds; 3) the 100 kDa – 220 nm fine colloids including organic-mineral (Fe, Mn and Al (oxy)hydroxides and clay minerals); 4) the >220 nm coarse colloids and acid soluble particles (ASPs) comprising minerals. Influenced by the ion exchange effect of in situ leaching, REEs in leachate were mostly dissolved (79 %). The pH of the groundwater far from the mine site was increased (5.8 – 7.3), the fine organic-mineral colloids (46 % – 80 %) were the main vectors of transport for REEs. Further analysis by AF4 revealed that the fine colloids can be divided into mineral-rich (F1, 100 kDa – 120 nm) and organic matter-rich (F2, 120 – 220 nm) populations. The main colloids associated with REEs shifted from F1 (64 % ∼ 76 %) to F2 (50 % ∼ 52 %) away from the mining area. For F1 and F2, the metal/C molar ratio decreased away from the mining area and middle to heavy REE enrichment was presented. According to the REE fractionation, organic matter was the predominant component capable of binding REEs in fine colloids. Overall, our results indicate that REEs in the groundwater system shifted from the dissolved to the colloidal phase in a catchment affected by in situ leaching, and organic-mineral colloids play an important role in facilitating the migration of REEs.

Controls of groundwater mineralization assessment in a mining catchment in the Upper West Region, Ghana: Insights from hydrochemistry, pollution indices of groundwater, and multivariate statistics

Natural and anthropogenic activities have proven to be the main sources of contaminants in groundwater. Hence, the need for continuous evaluation of the controlling factors of groundwater mineralization for monitoring purposes. The study assessed the controls of the groundwater mineralization in the Julie gold belt of the Upper West Region of Ghana using hydrochemistry, pollution index of groundwater (PIG), percentage of pollution index (PPI), factor analysis, and a multivariate linear regression model. TDS ​> ​HCO3− ​> ​NO3− ​> ​Ca2+ ​> ​Mg2+ ​> ​Na+ ​> ​Cl− ​> ​SO42− ​> ​K+ ​> ​CO32− ​> ​F− are the trends in the abundance of the hydrochemical parameters and are generally within WHO acceptable limits, with the exception of F− and NO3− contents in 5 and 32 communities, respectively. Waters containing Mg2+, Na+, HCO3−, and SO42− evolved into Mg–HCO3–Na–SO4. The PIG indicated pollution levels of 73.3% and 26.7% from mineral dissolution and agricultural activities, respectively, from the PPI values. From the indices, shallow meteoric water (r2 ​> ​1 values), factor analysis, and regression model approaches, anthropogenic activities, and mineral dissolution are the main controlling factors for the groundwater chemical composition in the area.

Geochemical distributions of natural radionuclides in surface soils and sediments impacted by lead-zinc mining activity

This study investigated the distribution features of uranium-238 (238U), radium-226 (226Ra), thorium-232 (232Th), and potassium-40 (40K) and evaluated the associated environmental radiological hazards of the topsoil and river sediments in the Jinding lead-zinc (Pb-Zn) mine catchment from Southwest China. The activity concentrations of 238U, 226Ra, 232Th, and 40K ranged from 24.0 ± 2.29–60.3 ± 5.26 Bq.kg-1, from 32.5 ± 3.95–69.8 ± 3.39 Bq.kg-1, from 15.3 ± 2.24–58.3 ± 4.92 Bq.kg-1, and from 203 ± 10.2–1140 ± 27.4 Bq.kg-1, respectively. The highest activity concentrations for all these radionuclides were primarily found in the mining areas and decreased with increasing distance from the mining sites. The radiological hazard indices, including radium equivalent activity, absorbed gamma dose rate in the air, outdoor annual effective dose equivalent, annual gonadal dose equivalent, and excess lifetime cancer, revealed that the highest values were observed in the mining area and downstream, specifically in the vicinity of the ore body. These elevated values exceeded the global mean value but remained below the threshold value, suggesting that routine protection measures for Pb-Zn miners during production activities are sufficient. The correlation analysis and cluster analysis revealed strong associations between radionuclides such as 238U, 226Ra, and 232Th, indicating a common source of these radionuclides. The activity ratios of 226Ra/238U, 226Ra/232Th, and 238U/40K varied with distance, suggesting the influence of geological processes and lithological composition on their transport and accumulation. In the mining catchment areas, the variations in these activity ratios increased indicated the impact of limestone material dilution on the levels of 232Th, 40K, and 238U in the upstream region. Moreover, the presence of sulfide minerals in the mining soils contributed to the enrichment of 226Ra and the removal of 238U caused those activity ratios decreased in the mining areas. Therefore, in the Jinding PbZn deposit, the patterns of mining activities and surface runoff processes in the catchment area favored the accumulation of 232Th and 226Ra over 40K and 238U. This study provides the first case study on the geochemical distributions of natural radionuclides in a typical Mississippi Valley-type PbZn mining area and offers fundamental information on radionuclide migration and baseline radiometric data for PbZn deposits worldwide.

Effects of in situ leaching on the origin and migration of rare earth elements in aqueous systems of South China: Insights based on REE patterns, and Ce and Eu anomalies

In situ leaching of ion-adsorption rare earth element (REE) deposits has released large amounts of REE-containing wastewater. However, the origin, speciation, distribution and migration of REEs in aqueous systems of the mining catchment are poorly understood. Groundwater, surface water, in situ leachates and weathered granite soil samples were collected from a catchment affected by mining activities in South China. The REE concentrations in groundwater (6.18 × 10–3–0.49 μmol L–1) and surface water (2.54–44.05 μmol L–1) decreased from upstream to downstream. REEs in groundwater were detected in organic matter associated (FA-REE) colloids, while the REE3+ and REE(SO4)+ were converted to REE(CO3)+ and FA-REE colloids from leachates and upstream surface water to downstream. The REE patterns of leachates and upstream groundwater (light and middle REE enrichment) resembled those of soil, but showed heavy REE enrichment due to FA-REE colloids in the downstream. REE in surface water were derived from middle REE enriched leachate. The Ce and Eu anomalies in the water samples indicated the REE origin (i.e., mining activities) and the hydrological variations (e.g., oxidation environment and water-rock interaction). Our results reveal the origin and fate of REE in aqueous systems of ion-adsorption REE mining catchments.

Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)

Abstract. Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive alternative technique to the conventional analysis of the geochemical properties. Here, we investigated the performance of four multi-proxy approaches based on (1) colour parameters, (2) geochemical properties, (3) colour parameters coupled with geochemical properties and (4) the entire visible spectrum to discriminate sediment source contributions in a mining catchment of New Caledonia. This French archipelago located in the south-west Pacific Ocean is the world's sixth largest producer of nickel. Open-cast nickel mining increases soil degradation and the downstream transfer of sediments in river systems, leading to the river system siltation. The sediment sources considered in the current research were therefore sediment eroded from mining sub-catchments and non-mining sub-catchments. To this end, sediment deposited during two cyclonic events (i.e. 2015 and 2017) was collected following a tributary design approach in one of the first areas exploited for nickel mining on the archipelago, the Thio River catchment (397 km2). Source (n=24) and river sediment (n=19) samples were analysed by X-ray fluorescence and spectroscopy in the visible spectra (i.e. 365–735 nm). The results demonstrated that the individual sediment tracing methods based on spectroscopy measurements (i.e. (1) and (4)) were not able to discriminate sources. In contrast, the geochemical approach (2) did discriminate sources, with 83.1 % of variance in sources explained. However, it is the inclusion of colour properties in addition to geochemical parameters (3) which provides the strongest discrimination between sources, with 92.6 % of source variance explained. For each of these approaches ((2) and (3)), the associated fingerprinting properties were used in an optimized mixing model. The predictive performance of the models was validated through tests with artificial mixture samples, i.e. where the proportions of the sources were known beforehand. Although with a slightly lower discrimination potential, the “geochemistry” model (2) provided similar predictions of sediment contributions to those obtained with the coupled “colour + geochemistry” model (3). Indeed, the geochemistry model (2) showed that mining tributary contributions dominated the sediments inputs, with a mean contribution of 68 ± 25 % for the 2015 flood event, whereas the colour + geochemistry model (3) estimated that the mining tributaries contributed 65 ± 27 %. In a similar way, the contributions of mining tributaries were evaluated to 83 ± 8 % by the geochemistry model (2) versus 88 ± 8 % by the colour + geochemistry model (3) for the 2017 flood event. Therefore, the use of these approaches based on geochemical properties only (2) or of those coupled to colour parameters (3) was shown to improve source discrimination and to reduce uncertainties associated with sediment source apportionment. These techniques could be extended to other mining catchments of New Caledonia but also to other similar nickel mining areas around the world.

Reconstructing the impact of nickel mining activities on sediment supply to the rivers and the lagoon of South Pacific Islands: Lessons learnt from the Thio early mining site (New Caledonia)

Opencast mining has exacerbated land degradation in New Caledonia, a French archipelago located in the south-west Pacific Ocean. Developed since the 1880s, mining has become the major economic activity in some catchments, which strongly disrupted sediment dynamics. Reconstructing the temporal changes of sediment source contributions is essential to understand the driving factors of soil erosion in response to i) the occurrence of cyclones, ii) the changes in mining practices during the last several decades, and iii) other soil degradation processes such as extensive soil erosion induced by fires, overgrazing and trampling of invasive species, and landslides. Accordingly, a multi-parameter analysis including gamma spectrometry, color and X-ray fluorescence measurements was conducted on a sediment core collected in a deltaic floodplain at the outlet of one of the first areas exploited for nickel mining, the Thio River catchment (397-km2). One geochemical tracer (i.e. K) has been used to quantify changes in sediment sources in the successive sediment layers deposited since the beginning of mining activity. The results showed that the contribution of mining tributaries largely dominated, with a mean contribution of 74% (SD 13%) of material sampled in the sediment core. This contribution notably increased after the mechanization of mining activities (i.e. from 1950s; increase of 18%). The occurrence of Cyclone Alison in 1975 triggered the progressive transfer of mining waste accumulated on the foothills over 25 years into the river system. This tipping point could be identified in the sediment sequence, which demonstrates that over the last 41 years (i.e. 1975–2016), a ~84-cm deep sediment deposit has accumulated in the alluvial floodplain of the Thio River catchment (mean annual deposition rate of 2 cm yr−1). Currently, the progressive release and downstream transfer of this mining waste is still ongoing ~45 years after Cyclone Alison. Although environmental legislation was introduced in 1975, mining tributary contributions to sediment still dominate (80%, SD 5%). Overall, this multi-proxy approach to examining the cumulative effects of mining activities on downstream sediment dynamics could be implemented in other mining catchments of New Caledonia and around the world to compare the respective mining source contributions to sediment and their evolution throughout time in these contrasted areas.

Evaluating controls on potentially toxic element release in circum-neutral mine water: a case study from the abandoned Pb\u2013Zn mines of Leadhills and Wanlockhead, South of Scotland, United Kingdom

Historic sulphidic Pb–Zn mining catchments at Leadhills and Wanlockhead, in the south of Scotland, UK have a legacy of mining of PbS (galena) and ZnS (sphalerite) from the twelfth century to the 1930s. The mining activities created tailing piles, ponds, adits and contaminated soils that contribute leaching and surface runoff of potentially toxic elements, particularly lead (Pb), which impact on the surface water and groundwater and are rapidly diluted in the wider catchment area. Studies by environmental regulators have shown that Pb, Cd and Zn in water can locally exceed the Environmental Quality Standards (EQS), particularly at Leadhills. To evaluate geochemical controls on release, 20 water sources (adits, surface water and near-surface groundwater) were sampled over four seasons (spring, summer, autumn and winter) over a 1-year period and characterized. Samples were circum-neutral pH from 6.3 to 7.9 (with average total dissolved solids < 55.0 mg/L), with no characteristics of acid mine drainage. The concentrations of PTEs in the water exceed UK EQS and WHO standards (and non-compliance on the Water Framework Directives). Geochemical modelling (GWB and PHREEQCv2) predicted mineral control on solubility which identified PbSO4 (anglesite), Fe2O3 ferric oxide (haematite), Fe3O4 (magnetite), FeCO3 (siderite), CaMg(CO3)2 (dolomite), CaCO3 (calcite) and Ca(Fe·Mg)(CO3)2 (ankerite) to be important. These were confirmed in solid phases analysed from tailings and sediments in contact with the hydrological cycle at the sites. Multivariate statistical analysis (PCA) of water samples associated with leaching through mine tailings showed strong seasonal variation with some elements (Fe, Cu, Cd, Pb, Na, Ca and Zn) with higher variance. The strong negative association of pH with soluble Zn, Cu, As, Cd and Pb highlights typical sulfide oxidation processes are taking place and supported by a positive correlation with temperature. Dissolution processes of mineral phases indicated by positive association of TDS and EC with Na, Ca and Zn. The data from PCA suggest contributions with potential for active generation of acid mine drainage and dissolution of solid phases influencing the release of PTEs into surface waters.

Comparative methods for predicting cyanide pollution in artisanal small-scale gold mining catchment by using logistic regression and kriging with GIS

It has been reported that persistent cyanide pollution occurs in artisanal small-scale gold mining (ASGM) catchment areas in Burkina Faso. In the present study, logistic regression (LR) and Regression Kriging (RK) methods were applied to predict cyanide pollution hazard at the catchment level as well as to determine the most vulnerable areas to prioritize for restoration of degraded ecosystems. Soil samples were collected from two ASGM sites in Burkina Faso: the northern Zougnazagmiline site and the southern Galgouli site. Free cyanide (FCN) concentration in each sample was measured and the use of the LR and RK methods identified the relationships between pollution sources and pathways. However, RK was able to identify more areas with a high cyanide hazard than LR. Nevertheless, the two methods reveal that the cyanidation zones and catchments outlets within the two catchments are where the highest risk of cyanide pollution occurs, with probabilities of 0.8 and 1 in Zougnazagmiline and Galgouli, respectively.

Investigating the use of fallout and geogenic radionuclides as potential tracing properties to quantify the sources of suspended sediment in a mining catchment in New Caledonia, South Pacific

PurposeNew Caledonia, a French island located in the south-west Pacific Ocean, has vast nickel resources. Open-cast mining has strongly increased soil erosion and the subsequent downstream transfer of sediments in river systems resulting in fundamental morphological changes (e.g., hyper-sedimentation, over-burden). Understanding the sediment source contributions from mining activities is therefore important to guide the implementation of effective management measures.Materials and methodsA pilot sediment tracing study was conducted in the Thio River (400 km2) catchment draining the island’s first mine. Sediment deposited during the February 25, 2015, and April 10, 2017, flood events was collected with a tributary tracing design, including main stem (n = 19) and tributary (n = 24) samples. The tributaries were classified into two source types: sub-catchments draining mining sites and sub-catchments devoid of mining activities. Three sets of potential tracing parameters (i.e., fallout radionuclides, geogenic radionuclides, and elemental geochemistry) were examined for their potential to model the contributions of sediment from mining versus non-mining tributaries to sediment collected on the Thio River.Results and discussionThe very low fallout radionuclide activities (137Cs and 210Pbxs) found in the source and sediment samples demonstrate that most material transiting the river network is derived from subsoil sources. Geogenic radionuclides and elemental geochemistry were therefore utilized in the tributary tracing approach. Accordingly, U and K were selected as the optimal tracers of the two main lithological regions supplying sediment to the main stem of the Thio River. Model results demonstrated that tributaries with mining activity dominated the sediment supply to the Thio River with mean sediment contributions of 68% (SD 28%) for the 2015 flood and 86% (SD 7%) for the 2017 event.ConclusionsGeogenic radionuclides and elemental geochemistry were more effective at discriminating between tributaries with and without mines than fallout radionuclides. The similarity of the model results from tracing with geogenic radionuclides and elemental geochemistry illustrates their potential to investigate sediment source contributions in similar catchments across the South Pacific Islands affected by mining activities.

Controls on rare-earth element transport in a river impacted by ion-adsorption rare-earth mining

Rare-earth elements (REEs) are known to be a group of emerging pollutants, but the geochemistry of REEs in river waters in ion-adsorption rare-earth mining areas has attracted little attention. In this study, samples of the <0.45 μm and 0.22–0.45 μm (large colloids) water fractions and acid-soluble particles (ASPs) were collected from a river impacted by ion-adsorption rare-earth mining activities. The roles of ligand complexation, colloid binding, and particle adsorption in REE transport and distribution were also investigated. Results showed higher concentrations of REEs in the <0.45 μm fraction of all sampling sites (3.30 × 10−2–9.42 μM) compared with that in the control site (1.21 × 10−3 μM); this fraction was also characterized by middle REE enrichment at upstream sites, where REEs are mainly controlled by the <0.22 μm fraction (55%–94% of the species found in the <0.45 μm fraction) and ligand complexation (REE3+, REE(SO4)+, and REE(CO3)+). At downstream sites, heavy REE enrichment was observed, which was largely determined by binding to large colloids (68%–83% of the species found in the <0.45 μm fraction) and adsorption to particles (>90% of the acidified bulk water). Furthermore, REE patterns indicated that the REE-associated large colloids were mineral or mixed mineral–organic matter (OM) at upstream sites and OM-dominated or functionalized at downstream sites. The particles were mainly coated by inorganic matter substances (e.g., Fe/Al oxyhydroxides). In summary, our results reveal that REE patterns provide a useful tool to study the fate of REEs in ion-adsorption rare-earth mining catchments.

Thallium release from acid mine drainages: Speciation in river and tap water from Valdicastello mining district (northwest Tuscany)

In this work we present an advantageous method for the simultaneous separation and detection of Tl(I) and Tl(III) species through ion chromatography coupled with on-line inductively coupled plasma – mass spectrometry. Chromatographic separation between Tl(III) and Tl(I) was achieved in less than two minutes. The method was validated by recovery experiments on real samples, and by comparing the sum of the concentrations of individual Tl species with total thallium values obtained from continuous flow ICP-MS. The experimental procedure offers an accurate, sensitive and interference-free method for Tl speciation at trace levels in environmental samples. This allowed us to investigate the Tl speciation in acid mine drainages (AMD), surface waters and springs in a mining catchment in Valdicastello Carducci (Tuscany, Italy), where severe Tl contamination ad been evidenced previously. This study shows for the first time that Tl(III), in addition to Tl(I), is present in considerable amounts in water samples affected by acid mining outflow, raising the question of the origin of this thermodynamically unstable species.

Biodegradation of free cyanide by bacterial species isolated from cyanide-contaminated artisanal gold mining catchment area in Burkina Faso

Soil and water samples were collected from a watershed in Burkina Faso where illegal artisanal gold extraction using cyanidation occurs. The samples were used to evaluate cyanide contamination and the presence of cyanide degrading bacteria (CDB). Free cyanide (F-CN) was detected in all samples, with concentrations varying from 0.023 to 0.9 mg kg−1, and 0.7–23 μg L−1 in the soil and water samples, respectively. Potential CDB also were present in the samples. To test the effective F-CN degradation capacity of the isolated CDB species, the species were cultivated in growth media containing 40, 60 or 80 mg F-CN L−1, with or without nutrients, at pH 9.5 and at room temperature. More than 95% of F-CN was degraded within 25 h, and F-CN degradation was associated with bacterial growth and ammonium production. However, initial concentrations of F-CN higher than 100 mg L−1 inhibited bacterial growth and cyanide degradation. Abiotic tests showed that less than 3% of F-CN was removed by volatilization. Thus, the degradation of F-CN occurred predominately by biological mechanisms, and such mechanisms are recommended for remediation of contaminated soil and water.The bacteria consortium used in the experiment described above exist in a Sahelian climate, which is characterized by a long hot and dry season. Because the bacteria are already adapted to the local climate conditions and show the potential for cyanide biodegradation, further applicability to other contaminated areas in West Africa, where illegal gold cyanidation is widespread, should be explored.

Socioeconomic Impact of Mining Activity: Effects of Gold Mining on Local Communities in Tanzania and Mali

The effect of extractive activity on economic growth and development is a long debated issue in economics literature. While most of the existing literature focuses on the macroeconomic impacts of natural resource abundance, there is a rather limited but growing strand of literature that studies the local economy impact of extractive activity using micro data. This paper aims to contribute to this literature by providing new evidence on the effects of gold mining in two resource-rich African countries: Tanzania and Mali.We utilize a rich data set collected from various sources and apply a differences-in-differences estimation strategy to see whether individuals/households geographically close to mines, are affected differently from the opening of mines. We look at a number of outcome variables including various measures of children’s health indicators, households’ access to facilities, and women and men’s employment status. The first part of the analysis is at the household/individual level where the data is kept and treatment is defined at. As a second attempt, we aggregate the data up to the district level by using the appropriate poverty mapping techniques and apply Abadie et al. (2010)’s Synthetic Control Group method to study whether mining districts behave differently from non-mining districts after mines start operation.We reach different conclusions for the two case countries. In the case of Tanzania, we show that households in the immediate mining catchment area are negatively affected from extractive activity whereas this effect becomes positive when we consider households that are located in neighboring and further away catchment areas. In the case of Mali, any significant positive impact of mining activity is on those households who are located closer to the mines. Those households, who are still in the catchment area but further away from the mine, are either not affected or negatively affected from mining activity.

Modelling remediation scenarios in historical mining catchments

Local remediation measures, particularly those undertaken in historical mining areas, can often be ineffective or even deleterious because erosion and sedimentation processes operate at spatial scales beyond those typically used in point-source remediation. Based on realistic simulations of a hybrid landscape evolution model combined with stochastic rainfall generation, we demonstrate that similar remediation strategies may result in differing effects across three contrasting European catchments depending on their topographic and hydrologic regimes. Based on these results, we propose a conceptual model of catchment-scale remediation effectiveness based on three basic catchment characteristics: the degree of contaminant source coupling, the ratio of contaminated to non-contaminated sediment delivery, and the frequency of sediment transport events.

Speciation of heavy metals in the surface waters of a former tin mining catchment

This study was conducted to investigate the chemical speciation of dissolved and particulate elements (Pb, Zn, Cu, Cr, As and Sn) in the mining wastewater. Speciation patterns of dissolved elements were estimated by adsorptive stripping voltammeter while particulate elements were analysed using a newly developed sequential extraction leaching procedure. The procedure has been operationally defined among five host fractions, namely exchangeable, carbonate, reducible, organic bound and residual. A total of six elements (Pb, Zn, Cu, Cr, As and Sn) were analysed in 30 samples at 10 locations (P1–P10) representing three subsequent samples at the same location to obtain the average value from ex-tin mining catchment. The results showed that the heavy metal pollution in P4 and P8 was more severe than in other sampling sites, especially Sn and Pb pollution. In the water samples at P4 and P8, both the total contents and the most dangerous non-residual fractions of Sn and Pb were extremely high. More than 90% of the total concentrations of As and Cr existed in the residual fraction. Cu and Zn mainly (more than 60%) occurred in the residual fraction. However, Pb and Sn were predominantly present in the non-residual fractions of the surface water. For all the six dissolved elements, the less labile species formed the predominant fraction in their speciation patterns. We conclude that the speciation patterns of particulate elements show that most of the Pb, Zn, Cu, Cr, As and Sn were found in the reducible fraction whereas Pb and Sn were mainly associated with the organic fraction.

Chemical Speciation and Potential Mobility of Heavy Metals in the Soil of Former Tin Mining Catchment

This study describes the chemical speciation of Pb, Zn, Cu, Cr, As, and Sn in soil of former tin mining catchment. Total five sites were selected for sampling and subsequent subsamples were collected from each site in order to create a composite sample for analysis. Samples were analysed by the sequential extraction procedure using optical emission spectrometry (ICP OES). Small amounts of Cu, Cr, and As retrieved from the exchangeable phase, the ready available for biogeochemical cycles in the ecosystem. Low quantities of Cu and As could be taken up by plants in these kind of acidic soils. Zn not detected in the bioavailable forms while Pb is only present in negligible amounts in very few samples. The absence of mobile forms of Pb eliminates the toxic risk both in the trophic chain and its migration downwards the soil profile. The results also indicate that most of the metals have high abundance in residual fraction indicating lithogenic origin and low bioavailability of the metals in the studied soil. The average potential mobility for the metals giving the following order: Sn > Cu > Zn > Pb > Cr > As.

Bioaccumulation of Heavy Metals in Fish Species Collected From Former Tin Mining Catchment

This study has been carried out to determine the accumulation of heavy metals (arsenic, copper, lead, tin and zinc) in fish samples collected from former tin mining catchment. Total eight types of fish family having fifteen different species are identified. Cyperinidae is the most abundant family with eight different species found in the catchment. Fish samples were analysed by using inductively coupled plasma optical emission spectrophotometer ICP-OES. The accuracy of method is validated by certified reference material. The highest level of arsenic was observed in Hampala macrolepidota while Osteochilus hasselti shows the least. For Copper concentrations, the maximum was obtained in Mastacembelus armatus and the minimum in Oxyeleotris marmorata. High levels of lead, tin and zinc were found in the Rasbora elegans, Trichogaster trichopterus, Oxyeleotris marmorata respectively while Macrobrachium resenbergii,Mastacembelus armatus, Rasbora elegans had the least concentrations. The sequence of order of the heavy metals measured was Sn > Pb >Zn > Cu> As, respectively. The results showed elevated levels of tin, led and zinc in all the fish samples although copper and arsenic were available in relatively low concentration in the most samples. Sn, Pb, and Zn concentration in the samples were greater than Malaysia food act permissible levels. Hazard index 1 suggests the probability of adverse health effects. Although the heavy metals anal ysed in the catchment did not pose any immediate health risk to humans but due to thebioaccumulation and magnification of these heavy metals in humans, it is essential to safeguard levels of the metals in the environment.

Study of chemical forms of heavy metals collected from the sediments of tin mining catchment

The chemical speciation of heavy metals (arsenic, chromium, copper, lead, zinc and tin) in the sediments of the former tin mining catchment Bestari Jaya, Peninsular Malaysia was determined using the latest version of the Community Bureau of Reference, the BCR 3-step, sequential extraction procedure. A fourth step was introduced for the digestion and analysis of the residue. The analysis of total metal content was carried out using microwave-assisted acid digestion. The percentage of each metal obtained from the four steps extraction (acid-soluble + reducible + oxidisable + residual) is in good agreement with the percentage of total metal content obtained from microwave digestion, which implies that the accuracy of the procedure. The degree of pollution in catchment sediments was assessed using geoaccumulation index Igeo and pollution intensity IPOLL. The results indicates that: (1) the sediments have been polluted with arsenic (8.8%), chromium (12.9%), copper (17.4%), lead (19.5%), zinc (14.9%) and tin (33.8%) and have high anthropogenic influences; (2) the calculation of geo-accumulation index suggests that catchment sediments have background concentrations of all the studied metals (Igeo < 0); (3) high I POLL, showed that all of these heavy metals pose a high environmental risk; and (4) the mobility order of metals in sediments at S1 and S2 was Sn>Pb>Zn>Cr >Cu >As, whereas at S3, S4 and S5 it was Cu>Pb>Zn>Cr>Sn>As. In conclusion, acidic pH, total organic carbon, scavenging ability and co-precipitation (inclusion, occlusion and adsorption) of studied metals with non-metals could account for changes in the geochemistry of the catchment sediments.

Morphology, Geology and Water Quality Assessment of Former Tin Mining Catchment

Bestari Jaya, former tin mining catchment covers an area of 2656.31 hectares comprised of four hundred and forty-two different-size lakes and ponds. The present study area comprise of 92 hectares of the catchment that include four large size lakes. Arc GIS version 9.2 used to develop bathymetric map, Global Positioning System (GPS) for hydrographical survey and flow meter was utilized for water discharge analysis (flow routing) of the catchment. The water quality parameters (pH, temperature, electric conductivity, dissolved oxygen DO, total dissolved solids TDS, chlorides, ammonium, nitrates) were analyzed by using Hydrolab. Quality assurance (QA) and quality control (QC) procedures were strictly followed throughout the field work and data analysis. Different procedures were employed to evaluate the analytical data and to check for possible transcription or dilution errors, changes during analysis, or unusual or unlikely values. The results obtained are compared with interim national water quality standards for Malaysia indicates that water quality of area is highly degraded. It is concluded that Bestri Jaya ex-mining catchment has a high pollution potential due to mining activities and River Ayer Hitam, recipient of catchment water, is a highly polluted river.