Heavy metal contamination from mining sites in South Morocco: Monitoring metal content and toxicity of soil runoff and groundwater (original) (raw)
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Chemosphere, 2006
Our work was conducted to investigate the heavy metal toxicity of tailings and soils collected from five metal mines located in the south of Morocco. We used the MetPAD TM biotest Kit which detects the toxicity specifically due to the heavy metals in environmental samples. This biotest initially developed to assess the toxicity of aquatic samples was adapted to the heterogeneous physico-chemical conditions of anthropogenic soils. Contrasted industrial soils were collected from four abandoned mines (A, B, C and E) and one mine (D) still active. The toxicity test was run concurrently with chemical analyses on the aqueous extracts of tailings materials and soils in order to assess the potential availability of heavy metals. Soil pH was variable, ranging from very acidic (pH 2.6) to alkaline values (pH 8.0-8.8). The tailings from polymetallic mines (B and D) contained very high concentrations of Zn (38 000-108 000 mg kg À1 ), Pb (20 412-30 100 mg kg À1 ), Cu (2019-8635 mg kg À1 ) and Cd (148-228 mg kg À1 ). Water-extractable metal concentrations (i.e., soil extracts) were much lower but were highly toxic as shown by the MetPAD TM test, except for soils from mines A, E and site C3 from mine C. The soil extracts from mine D were the most toxic amongst all the soils tested. On this site, the toxicity of soil water extracts was mainly due to high concentrations of Zn (785-1753 mg l À1 ), Cu (1.8-82 mg l À1 ) and Cd (2.0-2.7 mg l À1 ). The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in tailings materials and soils. Therefore, the MetPAD TM test can be used as a rapid and sensitive predictive tool to assess the heavy metal availability in soils highly contaminated by mining activities.
Biota as toxic metal indicators
Metal in the environment arises from both natural sources and human activities. Toxic metals in air, soil, and water have become a global problem. They are potential hazards to aquatic, animal, and human life because of their toxicity, bioaccumulative, and non-biodegradable nature. The major impacts of metal pollutants can be stated as ecosystem contamination and health problems of exposed human populations. Those problems have been a cause of increasing public concern throughout the world. Some trace metals are used by living organisms to stabilize protein structures, facilitate electron transfer reactions, and catalyze enzymatic reactions. But even metals that are biologically essential can be harmful to living organisms at high levels of exposure. An increasing concentration of heavy metals in the environment can modify mineral and enzyme functions of human beings. During the last two decades, the interest in using bioindicators as monitoring tools to assess environmental pollution with toxic metals has increased. Bioindicators are flora and fauna members, which are collected and analyzed to measure the levels of metal contaminants. Bioindicators therefore identify health hazards. Various living organisms, such as microbes, fungi, plants, animals, and humans, are used to monitor toxic metals from air, water, sediment, soil, and food chain. Here, we review recent bioindicators, toxicity assessment, and ecological effects. Fig. 1 a Value of world mining activities, b world metals value at mine (Ö stensson 2006)
Environmental risk assessment of metal-contaminated areas using different bioassays
Nova Biotechnologica et Chimica, 2020
Mining activities in the areas Krompachy and Rudňany-Markusovce were focused on mining and processing of copper and mercury ore and left harmful effects on the region of Eastern Slovakia. The aim of this study is using different screening methods (XRF, Phytotoxkit and earthworm bioassays) for environmental risk assessment of metal-contaminated areas. Elemental analysis by X-ray fluorescence spectrometry indicated severe pollution of studied soils by Cu, Ni, As and Hg, which exceeded limit values. Significant positive correlation is found between Pb and Zn occurrence in the agricultural soil from Krompachy: Kluknava, and for the contents of particular metals in soil from permanent grass vegetation in Kolinovce locality, namely between Pb and Ni, Pb and Zn, and between Hg and Zn contents. A 7-day bioassay and avoidance test with the Dendrobaena veneta was used to assess the environmental risk of heavy metals in soils. The earthworms mortality was very little influenced by metals in Kr...
Predicting metal toxicity in sediments: A critique of current approaches
Integrated Environmental Assessment and Management, 2007
The ability to predict metal toxicity in sediments based on measurements of simple chemical parameters is not possible using currently available sediment-quality guidelines (SQGs). Past evaluations of available SQGs for metals indicated little difference in their predictive abilities; however, the scientific understanding of cause-effect relationships is progressing rapidly. Today, it is clear that they can be protective of benthic ecosystem health, but single-value SQGs will be ineffective for predicting the toxicity of metals in sediments. Recent exposure-effects models and the sediment biotic ligand model both indicate that a better approach would be to have SQG concentrations, or ranges, that are applied to different sediment types. This review indicates that significant improvements in laboratory and field-based measurements, better recording of parameters that influence metal toxicity in sediments, as well as quantification of the metal exposure routes and the relative contribution of dissolved and particulate sources to toxic effects are needed to improve the power of predictive models and the overall effectiveness of SQGs for metals. Simply exposing benthic organisms to contaminated sediments and reporting effects concentrations or thresholds based on particulate metal concentrations will provide little information to aid future SQG development. For all tests, careful measurement and reporting of concentrations of particulate metal-binding phases (e.g., sulfide, organic carbon, and iron phases), metal partitioning between porewater and sediments, and porewater pH are considered as minimum data requirements. When using metal-spiked sediments, much better efforts are required to achieve sediment properties that resemble those of naturally contaminated sediments. Our current understanding of metal toxicity indicates that considerably greater information requirements will be needed to predict sublethal and chronic effects of metals, because the toxic, metabolically available concentration of metals within an organism will fluctuate over time. Based on the review of exposure and effects models, along with improved measurement of metal exposure-related parameters, the measurement of the short-term uptake rate of metals into organisms is likely to improve future models.
Toxic Metal Implications on Agricultural Soils, Plants, Animals, Aquatic life and Human Health
International Journal of Environmental Research and Public Health
The problem of environmental pollution is a global concern as it affects the entire ecosystem. There is a cyclic revolution of pollutants from industrial waste or anthropogenic sources into the environment, farmlands, plants, livestock and subsequently humans through the food chain. Most of the toxic metal cases in Africa and other developing nations are a result of industrialization coupled with poor effluent disposal and management. Due to widespread mining activities in South Africa, pollution is a common site with devastating consequences on the health of animals and humans likewise. In recent years, talks on toxic metal pollution had taken center stage in most scientific symposiums as a serious health concern. Very high levels of toxic metals have been reported in most parts of South African soils, plants, animals and water bodies due to pollution. Toxic metals such as Zinc (Zn), Lead (Pb), Aluminium (Al), Cadmium (Cd), Nickel (Ni), Iron (Fe), Manganese (Mn) and Arsenic (As) ar...
Characterizing toxicity of metal-contaminated sediments from mining areas
Applied Geochemistry, 2015
This paper reviews methods for testing the toxicity of metals associated with freshwater sediments, linking toxic effects with metal exposure and bioavailability, and developing sediment quality guidelines. The most broadly applicable approach for characterizing metal toxicity is whole-sediment toxicity testing, which attempts to simulate natural exposure conditions in the laboratory. Standard methods for whole-sediment testing can be adapted to test a wide variety of taxa. Chronic sediment tests that characterize effects on multiple endpoints (e.g., survival, growth, and reproduction) can be highly sensitive indicators of adverse effects on resident invertebrate taxa. Methods for testing of aqueous phases (pore water, overlying water, or elutriates) are used less frequently. Analysis of sediment toxicity data focuses on statistical comparisons between responses in sediments from the study area and responses in one or more uncontaminated reference sediments. For large or complex study areas, a greater number of reference sediments is recommended to reliably define the normal range of responses in uncontaminated sediments-the 'reference envelope'. Data on metal concentrations and effects on test organisms across a gradient of contamination may allow development of concentration-response models, which estimate metal concentrations associated with specified levels of toxic effects (e.g. 20% effect concentration or EC20). Comparisons of toxic effects in laboratory tests with measures of impacts on resident benthic invertebrate communities can help document causal relationships between metal contamination and biological effects. Total or total-recoverable metal concentrations in sediments are the most common measure of metal contamination in sediments, but metal concentrations in labile sediment fractions (e.g., determined as part of selective sediment extraction protocols) may better represent metal bioavailability. Metals released by the weak-acid extraction of acid-volatile sulfide (AVS), termed simultaneously-extracted metals (SEM), are widely used to estimate the 'potentially-bioavailable' fraction of metals that is not bound to sulfides (i.e., SEM-AVS). Metal concentrations in pore water are widely considered to be direct measures of metal bioavailability, and predictions of toxicity based on pore-water metal concentrations may be further improved by modeling interactions of metals with other pore-water constituents using Biotic Ligand Models. Data from sediment toxicity tests and metal analyses has provided the basis for development of sediment quality guidelines, which estimate thresholds for toxicity of metals in sediments. Empirical guidelines such as Probable Effects Concentrations or (PECs) are based on associations between sediment metal concentrations and occurrence of toxic effects in large datasets. PECs do not model bioavailable metals, but they can be used to estimate the toxicity of metal mixtures using by calculation of probable effect quotients (PEQ = sediment metal concentration/PEC). In contrast, mechanistic guidelines, such as Equilibrium Partitioning Sediment Benchmarks (ESBs) attempt to predict both bioavailability and mixture toxicity. Application of these simple bioavailability models requires more extensive chemical characterization of sediments or pore water, compared to empirical guidelines, but may provide more reliable estimates of metal toxicity across a wide range of sediment types.
Human Health Risk and Bioaccessibility of Toxic Metals in
Journal of Health and Pollution
Accumulation of excess amounts of metal contaminants in the environment threatens the health of plants and animals because these metals exert biological effects on all life forms. 7, 8 Metal pollution in soils is of concern to researchers and regulatory agencies because most metals have adverse health effects. 9 Long term exposure to metals can result in reduced intelligence in humans, DNA damage, and memory impairment. 10,11 The toxic effects of metals are normally defined by their nature. For example, mercury and lead affect almost every human organ, arsenic is known to be a human Background. Anthropogenic activities such as artisanal mining pose a major environmental health concern due to the potential for discharge of toxic metals into the environment. Objectives. To determine the distribution and pollution patterns of arsenic (As), iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), manganese (Mn), copper (Cu) and zinc (Zn) in the topsoil of a mining community in Ghana, along with potential human health risks and in vitro bioaccessibility. Methods. Concentrations of metals were determined using X-ray fluorescence techniques and validated using inductively coupled plasma-mass spectrometry. Results. Concentrations of the metals in topsoil were in the order of magnitude of Cu (31.38 mg/kg) < Ni (45.39 mg/kg) < As (59.66 mg/kg) < Cr (92.87 mg/kg) < Zn (106.98 mg/kg) < Mn (1195.49 mg/kg) < Fe (30061.02 mg/kg). Geo-statistical and multivariate analyses based on hazard indices including contamination, ecological risks, geo-accumulation, and pollution load suggest that the topsoils are contaminated in the study area. The potential ecological risk index (PERI) showed high ecological risk effects (PERI=269.09), whereas the hazard index (1×10 −7 ) and carcinogenic risk index (1×10 −5 ) indicated low human health risks. Elevated levels of As, Cr, Ni, and Zn were found to emanate from anthropogenic origins, whereas Fe, Mn, and Cu levels were attributed mainly to geological and atmospheric depositions. Physicochemical parameters (pH, electrical conductivity and total organic carbon) showed weak positive correlations to the metal concentrations. Elemental bioaccessibility was variable, decreasing in the order of Mn (35±2.9%) > Cu (29±2.6%) > Ni (22±1.3%) > As (9±0.5%) > Cr (4±0.6%) > Fe (2±0.4%). Conclusions. Incorporation of in-vitro bioaccessibility into the risk characterization models resulted in a hazard index of less than 1, implying low human health risks. However, due to accumulation effects of the metals, regular monitoring is required. Competing Interests. The authors declare no competing financial interests.
The Iberian Pyrite Belt (SW Iberian Peninsula) has intense mining activity. Currently, its fluvial networks receive extremely acid lixiviate residue discharges that are rich in sulphates and metals in solution (acid mine drainage, AMD) from abandoned mines. In the current study, the sediment and water quality were analysed in three different areas of the Odiel River to assess the risk associated with the metal content and its speciation and bioavailability. Furthermore, sediment contact bioassays were performed using the freshwater clam Corbicula fluminea to determine its adequacy as a biomonitoring tool in relation to theoretical risk indexes and regulatory thresholds. Reburial activity and mortality were used as the toxic responses of clams when exposed to contaminated sediment.
Environmental Toxicology and Chemistry, 2003
The bioconcentration factor (BCF) and bioaccumulation factor (BAF) are used as the criteria for bioaccumulation in the context of identifying and classifying substances that are hazardous to the aquatic environment. The BCF/BAF criteria, while developed as surrogates for chronic toxicity and/or biomagnification of anthropogenic organic substances, are applied to all substances including metals. This work examines the theoretical and experimental basis for the use of BCF/BAF in the hazard assessment of Zn, Cd, Cu, Pb, Ni, and Ag. As well, BCF/BAFs for Hg (methyl and inorganic forms) and hexachlorobenzene (HCB) were evaluated. The BCF/BAF data for Zn, Cd, Cu, Pb, Ni, and Ag were characterized by extreme variability in mean BCF/BAF values and a clear inverse relationship between BCF/BAF and aqueous exposure. The high variability persisted when even when data were limited to an exposure range where chronic toxicity would be expected. Mean BCF/BAF values for Hg were also variable, but the inverse relationship was equivocal, in contrast with HCB, which conformed to the BCF model. This study illustrates that the BCF/ BAF criteria, as currently applied, are inappropriate for the hazard identification and classification of metals. Furthermore, using BCF and BAF data leads to conclusions that are inconsistent with the toxicological data, as values are highest (indicating hazard) at low exposure concentrations and are lowest (indicating no hazard) at high exposure concentrations, where impacts are likely. Bioconcentration and bioaccumulation factors do not distinguish between essential mineral nutrient, normal background metal bioaccumulation, the adaptive capabilities of animals to vary uptake and elimination within the spectrum of exposure regimes, nor the specific ability to sequester, detoxify, and store internalized metal from metal uptake that results in adverse effect. An alternative to BCF, the accumulation factor (ACF), for metals was assessed and, while providing an improvement, it did not provide a complete solution. A bioaccumulation criterion for the hazard identification of metals is required, and work directed at linking chronic toxicity and bioaccumulation may provide some solutions.
Quantification of Metal Contaminants and Risk Assessment in Some Urban Watersheds
Journal of Water Resource and Protection, 2020
Contamination by heavy metals is a serious threat to aquatic systems due to their level of toxicity at elevated levels. The pollution of urban watersheds is of particular concern because of its potential impact on the watershed ecosystem and the receiving larger water bodies. This study assessed the occurrence and distribution of cadmium, copper, nickel, lead and zinc in water and sediment samples collected from three urban watersheds in Lagos, Nigeria. The concentrations of metals were determined using atomic absorption spectrometry. The health risk index (HRI) of water usage was evaluated for both adults and children. HRI for cadmium and lead in some of the watersheds recorded HRI > 1 values, a cause for health concern. The pH of water ranged from 6.48 ± 0.28-6.54 ± 0.47 (2016) and 6.18 ± 0.56-6.53 ± 0.17 (2018) respectively while, for sediments, the pH values ranged from 6.14 ± 0.48-6.9 ± 0.15 and 5.38 ± 0.22-6.4 ± 0.38 for 2016 and 2018 respectively. The levels of metals in the water samples during the 2016 sampling cycle were found to be within the World Health Organization (WHO) guideline limits for drinking water. However, the 2018 cadmium, lead and zinc concentrations for Ira-Ipaye and Akesan watersheds exceed the WHO guideline limits. Cadmium was not detected in Ira-Ipaye and Akesan 2016 sediment samples. Statistical t-test and analysis of variance (ANOVA) were used to ascertain significant differences of metals concentration in the three watersheds. The pH and metal concentration values obtained for water and sediment for the year 2016 and 2018 were non-significantly different.