Seasonal and spatial variation of diffuse (non-point) source zinc pollution in a historically metal mined river catchment, UK

Copper and zinc interact significantly in their joint toxicity to Chlamydomonas reinhardtii: Insights from physiological and transcriptomic investigations

Copper (Cu) and zinc (Zn) often discharge simultaneously from industrial and agricultural sectors and cause stress to aquatic biota. Although microalgae have been extensively investigated for their responses to Cu or Zn exposure, how they cope with the mixtures of two metals, especially at transcriptomic level, remains largely unknown. In this study, Chlamydomonas reinhardtii was exposed to environmentally relevant concentrations of two metals. It was found that Zn promoted the entry of Cu into the algal cells. With the increase of combined toxicity, extracellular polymeric substances (EPS) and cell wall functional groups immobilized significant amounts of Cu and Zn. Furthermore, C. reinhardtii adjusted resistance strategies internally, including starch consumption and synthesis of chlorophyll and lipids. Upon high level of Cu and Zn coexistence, synergistic effects were observed in lipid peroxidation and catalase (CAT) activity. Under 1.05 mg/L Cu + 0.87 mg/L Zn, 256 differentially expressed genes (DEGs) were mainly involved in oxidative phosphorylation, ribosome, nitrogen metabolism; while 4294 DEGs induced by 4.21 mg/L Cu + 3.48 mg/L Zn were mainly related to photosynthesis, citric acid cycle, etc. Together, this study revealed a more comprehensive understanding of mechanisms of Cu/Zn detoxification in C. reinhardtii, emphasizing critical roles of photosynthetic carbon sequestration and energy metabolism in the metal resistance.

Seasonal differences in trace metal concentrations in the major rivers of the hyper-arid southwestern Andes basins of Peru

The southern rivers of Peru originate in the Andes Mountains and flow in a southwestern direction to the Pacific Ocean through one of the most hyper-arid regions of the world. During each sub-equatorial summer from December to February, rains and snow melt in the Andes increase the streamflow in these rivers, even as they pass through the 100 km arid zone to the ocean. This study quantified seasonal dynamics of 34 trace metal elements (TM) and other constituent concentrations in four southern river basins of Peru (Chili-Quilca, Tambo, Camana-Majes-Colca, and Ocoña) during 2019-2020. Consistent with previous studies, we observed that: (1) the river water in the southern basins had relatively high concentrations of B, As, Fe, Al, Mn, P, Pb and Ni, with As the most ubiquitous toxic TM in all the basins, often detected at concentrations surpassing Peruvian and USEPA regulated concentrations; and (2) basins with the most to least toxic TM contamination were the Tambo > Chili-Quilca > Camana-Majes-Colca > Ocoña. Seasonal streamflow strongly influenced the concentrations of twenty TM, with 15 TM (Al, Au, Ba, Cd, Co, Cu, Fe, Gd, Mn, Ni, P, Pb, Ti, Yb and Zr) consistently higher in the wet season, and with As, B, Ge, Li, and Pd higher in the dry season. Our results improve the understanding of seasonal variability and vulnerability in western Andes superficial water sources, which are highly influenced by both local geogenic and anthropogenic conditions. A Spanish translation of this paper is available in the online Supplementary Material.

Zinc transport and partitioning of a mine-impacted watershed: An evaluation of water and sediment quality

Watershed systems influenced by mining waste products can persist for many years after operations are ceased, leading to negative impacts on the health of the surrounding environment. While geochemical behaviors of these trace metals have been studied extensively at the benchtop-scale, much fewer studies have looked at controls on their distributions at the watershed-level. In this study, trace metals (As, Cd, Cr, Cu, Ni, and Zn) were reported from water and stream bed sediments at eight sites between the years 2014-2018 along a watershed undergoing active remediation efforts. Zn was determined to be the only trace metal analyzed with concentrations above EPA and Kansas Department of Health guidelines for both water and sediment in the watershed, and thus was the primary focus for determining the health of the watershed system. Controls on trace metal pollution distribution over the watershed were investigated to determine where remediation efforts should be focused. Surface cover seemed to have the highest effectivity with pasture lands having a strong positive correlation to Zn concentrations. Initial remediation efforts were assessed by calculating the geoaccumulation index (Igeo) and the contamination factor (Cf-sediment) from sediments and contamination factor from water (Cf-water) after decades of chat pile removal efforts. Most of the sites showed significant reduction in metal concentration values compared to previous studies in the watershed for water and sediment, with four sites still reporting concentrations that reveal potential health risks. Results from this study will inform management and policy makers for areas to focus their remediation efforts on the Spring River Watershed as well as providing a framework for assessing pollution at a watershed scale.

A cuvette-compatible Zn2+sensing tool for conventional spectrofluorometers prepared by copolymerization of macrocyclic fluoroionophores on quartz glass surface

We report here the development of a surface-modified quartz glass sheet, which affords an opportunity for converting conventional spectrofluorometers to ion-selective optochemical sensors by placing it diagonally into a photometric cuvette. Moreover, we describe a generalizable technique, which allows the usage of any polymerizable ionophores for developing multiple-use fluorescent chemosensors of various selectivity. A fluorescent bis(acridino)-crown ether containing allyl groups was photocatalytically copolymerized with a methacrylate-acrylamide-based monomer mixture to obtain an ion-selective sensor membrane layer on the surface of the cuvette-compatible glass sheet. This glass membrane-based direct optode enabled the analysis of Zn²⁺above a lower limit of detection of 2.2×10^-7mol·L^-1with an excellent reusability. Limiting factors, like pH and competing ionic or organic agents were thoroughly investigated. Moreover, spiked river-water samples were measured to demonstrate applicability. The proposed sensor placed in any conventional spectrofluorometer provides an innovative method for perturbation-free analysis of Zn²⁺for all the chemists in need of a fast, easy-to-use, portable and regenerable analyzer without the requirement of an analyte-specific instrumentation.

Occurrence and distribution characteristics of heavy metals in the surface water of Yongding River Basin, China

Yongding River is a vital socioeconomic zone in China in providing daily usage for humans, animals, and running of industries and agriculture. This study first provides a comparative assessment for the heavy metal pollution in the surface water from 82 estuarine locations along the basin, including the Guanting Reservoir and seven wastewater treatment plants (WWTPs). The occurrence, distribution, potential sources, and water quality relating to the detected heavy metals were addressed. Eleven typical elements (Pb, Cr, As, Cd, Sb, Ba, V, Ti, Zn, Ni, and Be) were investigated, and the results showed that all the measured concentrations were below the WHO guideline limits. Most heavy metals exhibited higher levels in the middle of Yongding River basin due to the discharge of WWTPs. Pb, Ti, Zn, and Cd in the surface water mainly originated from anthropogenic discharge, while Sb and V were mostly contributed to geogenic sources according to the principal component analysis. Three documented methods, water quality index (WQI), heavy metal pollution (HPI), and Nemerow pollution index (Pn) values, were used to evaluate the contamination monitoring of surface water. All the locations were classified as low and moderate risk except Y12, B2, and Y13 for their Pn values were higher than 1.0. The present study highlights the status of heavy metals in Yongding River basin which is helpful in providing fundamental data for assessment of water quality and the effective protection for Yongding River basin in the future.

Assessment of heavy metal pollution and ecological risk in river water and sediments in a historically metal mined watershed, Northeast Japan

Mining legacies continue to impact the geochemical cycles in historically mined watersheds after mine closure. The Hokuroku District in Northeast Japan is a famous metal mining area with a long mining history; however, studies on the distribution mechanisms and pollution characteristics of heavy metals in these historically mined watersheds after the boom period of mining activities are lacking. This study aims to provide fundamental insights into the effects of the mining activities and hydrological conditions on heavy metal pollution in the Kosaka watershed, Hokuroku District. Sampling was performed in terms of watershed segmentation, and the outlet of the tributary within each sub-watershed was also sampled to capture the diffusional pollution status. The distributions of Zn, Cu, Cd, Pb and As in river water and sediments, as well as their pollution characteristics and ecological risks, were analysed under different hydrological conditions. Our findings provide evidence of the ecological risk in surface water induced by Zn, Cu and Pb pollution in the Kosaka River system. In a high proportion of the sub-watershed, there was moderate to strong enrichment in Cd, Cu and Zn in the river sediments. The sub-watersheds with high pollution levels and ecological risk were highly consistent with the sub-watersheds encompassing abandoned mine sites. Suspended particles carried large amounts of Pb and Cu, especially on rainy days. The heavy metal contents in river water were very sensitive to occasional rainfall events; rainy days posed the most risk to organisms in the Kosaka River, followed by the low-water-level season and the high-water-level season.

Zinc removal from highly acidic and sulfate-rich wastewater in horizontal sub-surface constructed wetland

This study demonstrated the successful use of a laboratory-scale baffled horizontal constructed wetland substituted with mixed organic media for zinc removal from high acidity (∼610 mg L^-1 as CaCO₃), sulfate-rich (∼1,300 mg L^-1) wastewater. The wetland was planted with Typha latifolia. The mean zinc concentration in the influent was gradually increased from 0.56 ± 0.02 mg L^-1 to 5.3 ± 0.42 mg L^-1. The mean zinc concentration in the outflow was 0.22 ± 0.19 mg L^-1, which accounted for 95% zinc removal throughout the study. However, total zinc uptake by the plants was 533 mg kg^-1, accounting for only 1.2% of total zinc removal; therefore, major zinc retention occurred within wetland media (83%). The overall activity and specific sulfidogenic activity decreased at the end of the study to 1.43 mg chemical oxygen demand removed per mg of TVS per day and 0.60 mg sulfate reduced per mg of TVS per day, respectively. Additionally, 16S rRNA sequencing revealed major dominant phyla present: Firmicutes (36%), Proteobacteria (16%), Actinobacteria (8.8%), Planctomycetes (7.8%), Chloroflexi (3.5%), Acidobacteria (1.9%) and Fibrobacteres (1.5%).

Baseflow and Stormflow Zinc Loads in a Small Agricultural River Catchment Influenced by an Industrial Area

A stringent environmental quality standard for zinc (Zn) has been enacted by regulators because of its toxicity to aquatic life. This study’s objective was to evaluate the variability of Zn concentrations and fluxes in the baseflow and stormflow and to estimate the contribution of Zn from point and non-point sources. By using high-resolution temporal sampling, the suspended solids (SS), iron (Fe), and Zn concentrations were measured in a small agricultural river catchment. Fe, as the natural non-point source, and Zn were evaluated using the end member mixing analysis (EMMA) to identify the source apportionment (point and non-point). The results indicate that in the baseflow, Zn mainly originated from point sources and was possibly discharged by manufacturing industries. By contrast, the non-point sources (diffuse sources) were responsible for extremely high SS, Fe, and Zn levels in the stormflow. In addition, Zn discharge during the stormflow was 93 times higher than that during the baseflow. According to the EMMA, approximately 74% of the Zn was from point sources. River management can be improved if Zn point sources are adequately treated. During a storm event, it is also important to control the particulate Zn released into the river.

Microwave Sensors for In Situ Monitoring of Trace Metals in Polluted Water

Thousands of pollutants are threatening our water supply, putting at risk human and environmental health. Between them, trace metals are of significant concern, due to their high toxicity at low concentrations. Abandoned mining areas are globally one of the major sources of toxic metals. Nowadays, no method can guarantee an immediate response for quantifying these pollutants. In this work, a novel technique based on microwave spectroscopy and planar sensors for in situ real-time monitoring of water quality is described. The sensors were developed to directly probe water samples, and in situ trial measurements were performed in freshwater in four polluted mining areas in the UK. Planar microwave sensors were able to detect the water pollution level with an immediate response specifically depicted at three resonant peaks in the GHz range. To the authors’ best knowledge, this is the first time that planar microwave sensors were tested in situ, demonstrating the ability to use this method for classifying more and less polluted water using a multiple-peak approach.

Joint recording of contamination status, multi-element dynamics, and source identification on a sub-catchment scale: The example Lahn River (Germany)

Investigations on the enrichment level, binding dynamics, and source identification of contaminants are important objectives of environmental research into surface waters, but are often carried out independently of each other. To simultaneously address these issues an investigative approach is presented that combines multi-element analyses of water and suspended particulate matter (SPM) and is applied on the scale of a sub-catchment, using the Lahn River (Germany) as an example. Analyses of water and SPM comprised phosphorus (P), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), lead (Pb), and uranium (U). For the dissolved phase, the investigations additionally included nitrogen compounds (NH₄, NO₃) and dissolved organic carbon (DOC). SPM of the Lahn showed increased average concentrations of Zn (2.13 g kg^-1), Cd (4.01 mg kg^-1), and Pb (160 mg kg^-1). The water phase sampled from points along the length of the Lahn showed significant spatial differences in the dissolved concentrations of Mn (15.7-98.4 μg l^-1), Co (0.08-0.66 μg l^-1), Ni (0.75-4.69 μg l^-1), Zn (19.9-187 μg l^-1), and Cd (0.01-0.18 μg l^-1), which could be attributed to the inflow of two tributaries draining historic mining areas. The study emphasizes the importance of mine waters during low water periods and proves that such sources can differently affect the SPM quality and the dissolved concentrations of their receiving waters.

Simulated Aquifer Heterogeneity Leads to Enhanced Attenuation and Multiple Retention Processes of Zinc

Alluvial aquifers serve as one of the main water sources for domestic, agricultural, and industrial purposes globally. Groundwater quality, however, can be threatened by naturally occurring and anthropogenic metal contaminants. Differing hydrologic and biogeochemical conditions between predominantly coarse-grained aquifer sediments and embedded layers or lenses of fine-grained materials lead to variation in metal behavior. Here, we examine processes controlling Zn partitioning within a dual-pore domain-reconstructed alluvial aquifer. Natural coarse aquifer sediments from the Wind River-Little Wind River floodplain near Riverton, WY, were used in columns with or without fine-grained lenses to examine biogeochemical controls on Zn concentrations, retention mechanisms, and transport. Following the introduction of Zn to the groundwater source, Zn preferentially accumulated in the fine-grained lenses, despite their small volumetric contributions. While the clay fraction dominated Zn retention in the sandy aquifer, the lenses supported additional reaction pathways of retention-the reducing conditions within the lenses resulted in ZnS precipitation, overriding the contribution of organic matter. Zinc concentration in the groundwater controlled the formation of Zn-clays and Zn-layered double hydroxides, whereas the extent of sulfide production controlled precipitation of ZnS. Our findings illustrate how both spatial and compositional heterogeneities govern the extent and mechanisms of Zn retention in intricate groundwater systems, with implications for plume behavior and groundwater quality.

Effect of an extreme flood event on solute transport and resilience of a mine water treatment system in a mineralised catchment

Extreme rainfall events are predicted to become more frequent with climate change and can have a major bearing on instream solute and pollutant transport in mineralised catchments. The Coledale Beck catchment in north-west England was subject to an extreme rainfall event in December 2015 that equated to a 1 in 200-year event. The catchment contains the UK's first passive metal mine water treatment system, and as such had been subject to intense monitoring of solute dynamics before and after commissioning. Due to this monitoring record, the site provides a unique opportunity to assess the effects of a major storm event on (1) catchment-scale solute transport, and (2) the resilience of the new and novel passive treatment system to extreme events. Monitoring suggests a modest decline in treatment efficiency over time that is not synchronous with the storm event and explained instead by changes in system hydraulic efficiency. There was no apparent flushing of the mine system during the event that could potentially have compromised treatment system performance. Analysis of metal transport in the catchment downstream of the mine suggests relatively subtle changes in instream chemistry with modest but statistically-significant reductions in zinc in the lower catchment irrespective of flow condition after the extreme event, but most parameters of interest show no significant change. Increased export of colloidal iron and aluminium is associated with major landslips in the mid-catchment after the storm and provide fresh sorption sites to attenuate dissolved zinc more rapidly in these locations, corroborated by laboratory experiments utilising site materials to investigate the attenuation/release of metals from stream and terrestrial sediments. The data are important as they show both the resilience of passive mine water treatment systems to extreme events and the importance of catchment-scale monitoring to ensure continued effectiveness of treatment initiatives after major perturbation.

Qualitative and quantitative adsorption mechanisms of zinc ions from aqueous solutions onto dead carp derived biochar

The adsorption mechanisms of Zn2+ on carp biochars mainly include precipitation with minerals, exchange with cations, and complexation with OFGs. The pyrolysis temperature of carp biochars has a significant effect on the mechanisms of Zn2+ adsorption.

Critical Shifts in Trace Metal Transport and Remediation Performance under Future Low River Flows

Exceptionally low river flows are predicted to become more frequent and more severe across many global regions as a consequence of climate change. Investigations of trace metal transport dynamics across streamflows reveal stark changes in water chemistry, metal transformation processes, and remediation effectiveness under exceptionally low-flow conditions. High spatial resolution hydrological and water quality datasets indicate that metal-rich groundwater will exert a greater control on stream water chemistry and metal concentrations because of climate change. This is because the proportion of stream water sourced from mined areas and mineralized strata will increase under predicted future low-flow scenarios (from 25% under Q45 flow to 66% under Q99 flow in this study). However, mineral speciation modelling indicates that changes in stream pH and hydraulic conditions at low flow will decrease aqueous metal transport and increase sediment metal concentrations by enhancing metal sorption directly to streambed sediments. Solute transport modelling further demonstrates how increases in the importance of metal-rich diffuse groundwater sources at low flow could minimize the benefits of point source metal contamination treatment. Understanding metal transport dynamics under exceptionally low flows, as well as under high flows, is crucial to evaluate ecosystem service provision and remediation effectiveness in watersheds under future climate change scenarios.

Ecological Risk Assessment of Heavy Metals in Water Bodies around Typical Copper Mines in China

In order to understand the heavy metal pollution status and ecological effect in aquatic environment around copper mine areas, seven heavy metals (Cd, Cd, Cr, Cu, Hg, Zn, the Ni, and Pb) in aquatic environments in seven representative copper mine regions were selected from the literature in 2005–2013 for ecological risk assessment by using potential ecological risk index, geoaccumulation index, nemerow index and species sensitivity distribution method (Potential Affected Fraction (PAF) and Multi-Substance PAF (MSPAF)). The results of sediment ecological risk analysis showed that Cd, Cu and Pb were the main pollutants in sediments. The results of species sensitivity distribution analysis showed that the HC5 values (Hazardous Concentration for 5% of species) of seven heavy metals were different with order Zn > Cr > Cd > Pb > Cu > Ni > Hg. The MSPAF of seven copper mines in the following order with species sensitivity distribution method was as follows: Dabaoshan (99%) = Dahongshan (99%) = Baiyin (99%) > Dexing (97%) > Jinchuan (92%) > Tongling (39%) > Daye (24%). This study analyzes the impact of copper mining on the aquatic environment, and the results of this study will be great value for the comprehensive pollution governance of mining.

Heavy metal accumulation, geochemical fractions, and loadings in two agricultural watersheds with distinct climate conditions

The main aim of this study was to explore the effects of climate conditions on the transport and transformation of heavy metals. Sedimentary geochemical analysis and watershed modeling were used to investigate the distinctions between heavy metal pollution under different climate conditions. The results showed that the average concentrations of Cu, Cd, and Pb in sediments of the subtropical watershed (36.64, 0.60, and 133.69 mg/kg, respectively) were higher than those of the temperate watershed (26.58, 0.19, and 23.17 mg/kg, respectively) because of surface runoff-induced heavy metal loadings under higher precipitation. Also, the labile fractions, which mainly originated from anthropogenic sources, showed higher percentages in the subtropical watershed (67.84-91.33%), thereby indicating that the transport of heavy metals was promoted by surface runoff. Moreover, higher percentages of acid-soluble fractions of Cu and Pb (23.55-33.60%) in the subtropical watershed suggested that higher temperatures accelerated the transformation of heavy metal fractions, thus contributing to the transportation of heavy metals. Overall, climate conditions were the dominant factors for the differences between the subtropical and temperate watersheds. The results of this study suggest that the effects of climate conditions on the transport, enrichment, and bioavailability of heavy metals are of great significance. Such effects should therefore be the focus of future studies.

A novel Cyphos IL 104-based polymer inclusion membrane (PIM) probe to mimic biofilm zinc accumulation

The presence of Zn in surface waters from abandoned mining zones is a critical issue since excess Zn concentrations may affect aquatic life and whole ecosystems. We present, for the first time, a simple tool based on a polymer inclusion membrane (PIM) intended to monitor Zn in river water by mimicking metal accumulation in the biofilm. The PIM-based probe contains a polymeric membrane prepared using cellulose triacetate (CTA, 50% w/w) as the base polymer, nitrophenyloctyl ether (NPOE) as the plasticizer (20% w/w), and the ionic liquid (IL) Cyphos 104 as the extractant (30% w/w). The accumulation of Zn in the acceptor phase (0.01 M HNO₃) was evaluated for different free metal concentrations at 4 h accumulation time resulting in a good correlation between the free metal concentration and the accumulated one. We also found that the metal accumulated agrees with the free metal fraction upon addition of EDTA in the donor solution. The results for Zn accumulation with the PIM-based probe were found to be comparable to those obtained for a biofilm that was grown in a stream from an abandoned mine area and subsequently translocated to the laboratory and put in contact with Zn polluted stream water, so confirming the effectiveness of this new probe in mimicking Zn accumulation in the biofilm.

The Impact of Metal-Rich Sediments Derived from Mining on Freshwater Stream Life

Metal-rich sediments have the potential to impair life in freshwater streams and rivers and, thereby, to inhibit recovery of ecological conditions after any remediation of mine water discharges. Sediments remain metal-rich over long time periods and have long-term potential ecotoxicological interactions with local biota, unless the sediments themselves are physically removed or replaced by less metal-rich sediment. Laboratory-derived environmental quality standards are difficult to apply to the field situation, as many complicating factors exist in the real world. Therefore, there is a strong case to consider other, field-relevant, measures of toxic effects as alternatives to laboratory-derived standards and to seek better biological tools to detect, diagnose and ideally predict community-level ecotoxicological impairment. Hence, this review concentrated on field measures of toxic effects of metal-rich sediment in freshwater streams, with less emphasis on laboratory-based toxicity testing approaches. To this end, this review provides an overview of the impact of metal-rich sediments on freshwater stream life, focusing on biological impacts linked to metal contamination.

Hydrotransport-Oriented Zn, Cu, and Pb Behavior Assessment and Source Identification in the River Network of a Historically Mined Area in the Hokuroku Basin, Northeast Japan

Aquatic ecosystems continuously receive potentially hazardous heavy metals from natural and anthropogenic sources. Focusing on the origin of heavy metals, this study aims to estimate the load contribution of tributaries from individual watershed and human drainage and to dissect the source of heavy metals, as commonly required for environmental impact assessment. Using integrated water dynamics, Geographic Information System (GIS), and chemical analysis, we identified and evaluated the heavy metal sources of the Kosaka river system in Hokuroku basin, which is a historically mined area in Northeast Japan, both in the high-water and low-water seasons. The migration and diffusion behaviors of heavy metals along with hydro-transport were analyzed, and the effects of mining activities on regional water quality both in the high-water and low-water seasons were clarified. The results indicate that Zn pollution was obvious in the Kosaka River network, especially in the downstream area. The spatial heterogeneity of heavy metal outflows from tributary watersheds was obvious, and the variations had strong correlations with mine site locations. The heavy metal flows in the mainstream increased sharply in the vicinity downstream of the Kosaka refinery drainage outlets. Compared to the low-water season, the influences of human drainage were slighter in high-water season, with lower contribution rates due to the dilution effect of the greater water discharge. Downscale sampling is effective to identify pollutant sources in regional basins.

Heavy Metal Soil Contamination Detection Using Combined Geochemistry and Field Spectroradiometry in the United Kingdom

Technological advances in hyperspectral remote sensing have been widely applied in heavy metal soil contamination studies, as they are able to provide assessments in a rapid and cost-effective way. The present work investigates the potential role of combining field and laboratory spectroradiometry with geochemical data of lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd) in quantifying and modelling heavy metal soil contamination (HMSC) for a floodplain site located in Wales, United Kingdom. The study objectives were to: (i) collect field- and lab-based spectra from contaminated soils by using ASD FieldSpec^® 3, where the spectrum varies between 350 and 2500 nm; (ii) build field- and lab-based spectral libraries; (iii) conduct geochemical analyses of Pb, Zn, Cu and Cd using atomic absorption spectrometer; (iv) identify the specific spectral regions associated to the modelling of HMSC; and (v) develop and validate heavy metal prediction models (HMPM) for the aforementioned contaminants, by considering their spectral features and concentrations in the soil. Herein, the field- and lab-based spectral features derived from 85 soil samples were used successfully to develop two spectral libraries, which along with the concentrations of Pb, Zn, Cu and Cd were combined to build eight HMPMs using stepwise multiple linear regression. The results showed, for the first time, the feasibility to predict HMSC in a highly contaminated floodplain site by combining soil geochemistry analyses and field spectroradiometry. The generated models help for mapping heavy metal concentrations over a huge area by using space-borne hyperspectral sensors. The results further demonstrated the feasibility of combining geochemistry analyses with filed spectroradiometric data to generate models that can predict heavy metal concentrations.

Predicting the Benefits of Mine Water Treatment under Varying Hydrological Conditions using a Synoptic Mass Balance Approach

Geochemical and hydrological data from abandoned mine watersheds demonstrated that (1) point sources of pollution fail to account for total receiving watercourse metal load at higher flows and (2) an inverse relationship exists between river flow and pH due to peatland runoff. Quantifying the varying importance of point and diffuse pollution sources enabled prediction of treatment benefits for a major point source of pollution in one watershed. Instream zinc load increases with river flow (∼3 to 14 kg Zn/d) due to diffuse groundwater and surface runoff pollution sources at higher flows. Lab tests demonstrated that metal release from the streambed, driven by pH decreases at higher flows, also contribute to increased downstream metal loads. Predicting point source treatment benefits demonstrates major instream improvements at low flow (zinc decreases from >800 to 120 μg Zn/L). At higher flows treatment benefits diminish (Zn decreases from 240 to only 200 μg Zn/L) due to the greater influence of diffuse sources. A quantitative understanding of the variable importance of point and diffuse sources of pollution, and instream processes of metal attenuation and release, is crucial to evaluating the benefits of treatment to downstream water quality.

Hydrogeochemical behavior of an anthropogenic mine aquifer: Implications for potential remediation measures

This study characterizes the hydrogeochemical behavior of one of the most pollutant sources in the Iberian Pyrite Belt, namely, the Poderosa adit outflow. This artificial spring arises from an anthropogenic mine aquifer with a similar hydrogeological behavior to karstic systems, where the infiltration area is an endorheic zone and the aquifer shows allogenic recharge. Recent mining has markedly increased the contaminant levels. The pollutant load released from the adit to the receiving water body is very high, with average loads of 280 kg/day of Fe, 47 kg/day of Al, 17 kg/day of Cu and so on. However, a high variability is observed related to hydrological and geochemical factors, especially during intense rainy episodes. Thus, the pollutant load during these events suffers a dramatic increase, i.e., from ~100-200 kg/day of Fe during base flow to almost 2200 kg/day during the flow peak. These data highlight the importance of short but intense rainy events on metal fluxes from mining areas, which has been previously reported in surface waters but scarcely reported in mine adits, with expected lower response times to rainfall. The pollutant load released by non-point sources, i.e., spoil heaps, is lower than that released from the adit most of the year, although it increased noticeably during intense rainy events. Some remediation measures were adopted during the 1990s without a suitable hydrogeological characterization and were shown to be ineffective. On the basis of the obtained results, potential restoration measures are discussed.

Synoptic sampling and principal components analysis to identify sources of water and metals to an acid mine drainage stream

Combining the synoptic mass balance approach with principal components analysis (PCA) can be an effective method for discretising the chemistry of inflows and source areas in watersheds where contamination is diffuse in nature and/or complicated by groundwater interactions. This paper presents a field-scale study in which synoptic sampling and PCA are employed in a mineralized watershed (Lion Creek, Colorado, USA) under low flow conditions to (i) quantify the impacts of mining activity on stream water quality; (ii) quantify the spatial pattern of constituent loading; and (iii) identify inflow sources most responsible for observed changes in stream chemistry and constituent loading. Several of the constituents investigated (Al, Cd, Cu, Fe, Mn, Zn) fail to meet chronic aquatic life standards along most of the study reach. The spatial pattern of constituent loading suggests four primary sources of contamination under low flow conditions. Three of these sources are associated with acidic (pH <3.1) seeps that enter along the left bank of Lion Creek. Investigation of inflow water (trace metal and major ion) chemistry using PCA suggests a hydraulic connection between many of the left bank inflows and mine water in the Minnesota Mine shaft located to the north-east of the river channel. In addition, water chemistry data during a rainfall-runoff event suggests the spatial pattern of constituent loading may be modified during rainfall due to dissolution of efflorescent salts or erosion of streamside tailings. These data point to the complexity of contaminant mobilisation processes and constituent loading in mining-affected watersheds but the combined synoptic sampling and PCA approach enables a conceptual model of contaminant dynamics to be developed to inform remediation.

Effect of addition of sewage sludge and coal sludge on bioavailability of selected metals in the waste from the zinc and lead industry

This study evaluated the content of bioavailable forms of selected heavy metals present in the waste from Zn and Pb processing that can potentially have an effect on the observed difficulties in reclamation of landfills with this waste. The particular focus of the study was on iron because its potential excess or deficiency may be one of the causes of the failure in biological reclamation. The study confirmed that despite high content of total iron in waste (mean value of 200.975gkg^-1), this metal is present in the forms not available to plants (mean: 0.00009gkg^-1). The study attempted to increase its potential bioavailability through preparation of the mixtures of this waste with additions in the form of sewage sludge and coal sludge in different proportions. Combination of waste with 10% of coal sludge and sewage sludge using the contents of 10%, 20% and 30% increased the amounts of bioavailable iron forms to the level defined as sufficient for adequate plant growth. The Lepidum sativum test was used to evaluate phytotoxicity of waste and the mixtures prepared based on this waste. The results did not show unambiguously that the presence of heavy metals in the waste had a negative effect on the growth of test plant roots.

Abandoned PbZn mining wastes and their mobility as proxy to toxicity: A review

Lead and zinc (PbZn) mines are a common occurrence worldwide; and while approximately 240 mines are active, the vast majority have been abandoned for decades. Abandoned mining wastes represent a serious environmental hazard, as Pb, Zn and associated metals are continuously released into the environment, threatening the health of humans and affecting ecosystems. Iron sulfide minerals, when present, can form acid mine drainage and increase the toxicity by mobilizing the metals into more bioavailable forms. Remediation of the metal waste is costly and, in the case of abandoned wastes, the responsible party(ies) for the cleanup can be difficult to determine, which makes remediation a complex and lengthy process. In this review, we provide a common ground from a wide variety of investigations about concentrations, chemical associations, and potential mobility of Pb, Zn and cadmium (Cd) near abandoned PbZn mines. Comparing mobility results is a challenging task, as instead of one standard methodology, there are 4-5 different methods reported. Results show that, as a general consensus, the metal content of soils and sediments vary roughly around 1000mg/kg for Zn, 100 for Pb and 10 for Cd, and mobilities of Cd>Zn>Pb. Also, mobility is a function of pH, particle size, and formation of secondary minerals. New and novel remediation techniques continue to be developed in laboratories but have seldom been applied to the field. Remediation at most of the sites has consisted of neutralization (e.g. lime,) for acid mine discharge, and leveling followed by phytostabilization. In the latter, amendments (e.g. biochar, fertilizers) are added to boost the efficiency of the treatment. Any remediation method has to be tested before being implemented as the best treatment is site-specific. Potential treatments are described and compared.

Assessing metal transfer to vegetation and grazers on reclaimed pyritic Zn and Pb tailings

A study of the concentrations of zinc and lead in an engineered soil capping system overlying sulphide mine tailings was undertaken. Tailings geochemistry, soil cover and vegetation were monitored over a 4-year period, and a cattle grazing demonstration exercise was conducted over a 1-year period. Whilst the tailings had a relatively high pyrite content and demonstrated oxidation, a circum neutral pH was observed for the duration of the study period due to the high dolomitic content. No evidence of metal mobility into the soil cover and vegetation was observed over the monitoring period. Relatively high Zn herbage content is attributed to the glacial till component of the soil cover. Similarly, no evidence of metal transfer to grazing cattle was observed through blood and tissue analysis with Zn content not significantly different from control animals. Pb tissue content was below limit of detection.

Combine the soil water assessment tool (SWAT) with sediment geochemistry to evaluate diffuse heavy metal loadings at watershed scale

Assessing the diffuse pollutant loadings at watershed scale has become increasingly important when formulating effective watershed water management strategies, but the process was seldom achieved for heavy metals. In this study, the overall temporal-spatial variability of particulate Pb, Cu, Cr and Ni losses within an agricultural watershed was quantitatively evaluated by combining SWAT with sediment geochemistry. Results showed that the watershed particulate heavy metal loadings displayed strong variability in the simulation period 1981-2010, with an obvious increasing trend in recent years. The simulated annual average loadings were 20.21 g/ha, 21.75 g/ha, 47.35 g/ha and 21.27 g/ha for Pb, Cu, Cr and Ni, respectively. By comparison, these annual average values generally matched the estimated particulate heavy metal loadings at field scale. With spatial interpolation of field loadings, it was found that the diffuse heavy metal pollution mainly came from the sub-basins dominated with cultivated lands, accounting for over 70% of total watershed loadings. The watershed distribution of particulate heavy metal losses was very similar to that of soil loss but contrary to that of heavy metal concentrations in soil, highlighting the important role of sediment yield in controlling the diffuse heavy metal loadings.

Flood-related contamination in catchments affected by historical metal mining: an unexpected and emerging hazard of climate change

Floods in catchments affected by historical metal mining result in the remobilisation of large quantities of contaminated sediment from floodplain soils and old mine workings. This poses a significant threat to agricultural production and is preventing many European river catchments achieving a 'good chemical and ecological status', as demanded by the Water Framework Directive. Analysis of overbank sediment following widespread flooding in west Wales in June 2012 showed that flood sediments were contaminated above guideline pollution thresholds, in some samples by a factor of 82. Most significantly, silage produced from flood affected fields was found to contain up to 1900 mg kg(-1) of sediment associated Pb, which caused cattle poisoning and mortality. As a consequence of climate related increases in flooding this problem is likely to continue and intensify. Management of contaminated catchments requires a geomorphological approach to understand the spatial and temporal cycling of metals through the fluvial system.

Mine water geochemistry and metal flux in a major historic Pb-Zn-F orefield, the Yorkshire Pennines, UK

Recent studies have shown up to 6 % of rivers in England and Wales to be impacted by discharges from abandoned metal mines. Despite the large extent of impacts, there are still many areas where mine water impact assessments are limited by data availability. This study provides an overview of water quality, trace element composition and flux arising from one such area; the Yorkshire Pennine Orefield in the UK. Mine drainage waters across the orefield are characterised by Ca-HCO3-SO4-type waters, with moderate mineralization (specific electrical conductance: 160-525 μS cm(-1)) and enrichment of dissolved Zn (≤2003 μg L(-1)), Ba (≤971 μg L(-1)), Pb (≤183 μg L(-1)) and Cd (≤12 μg L(-1)). The major ion composition of the waters reflects the Carboniferous gritstone and limestone-dominated country rock, the latter of which is heavily karstified in parts of the orefield, while sulphate and trace element enrichment is a product of the oxidation of galena, sphalerite and barite mineralization. Contaminant flux measurements at discharge sites highlight the disproportionate importance of large drainage levels across the region, which generally discharge into first-order headwater streams. Synoptic metal loading surveys undertaken in the Hebden Beck sub-catchment of the river Wharfe highlight the importance of major drainage levels to instream baseflow contamination, with diffuse sources from identifiable expanses of waste rock becoming increasingly prominent as river flows increase.

Spatial and temporal trace metal distribution of a Peruvian basin: recognizing trace metal sources and assessing the potential risk

Recent efforts have been made to determine the environmental impact of mining over the past 11 years in the Jequetepeque River basin, in northern Peru. We have now analyzed data from two studies to elucidate the spatial and temporal trace metal distributions and to assess the sources of contamination. These two studies were carried out from 2003 to 2008 by a Peruvian government administration and from 2008 to 2010 by us. We analyzed 249 samples by principal component analysis, measuring: pH, electrical conductivity, total dissolved solids, total suspended solids, chloride, weak-acid-dissociable cyanide, total cyanide, nitrite and nitrate, ammonium, sulfate, and trace metals and metalloids (Al, As, Ca, Cd, Cu, Cr, Fe, Mg, Mn, Ni, Pb, and Zn). Within the spatial distribution of the basin, the highest Al, As, Cu, Fe, Ni, and Pb concentrations were found at the closest point to the mine sites for both periods of time, with the higher peaks measured during the first years of the sampling data. Temporal trends showed higher concentrations of Cu and Fe in samples taken before 2005, at which point the two mines were closed. Risk assessment was quantified by the hazard quotient as related to water ingestion. The risk for human health posed by the concentrations of several trace metals and metalloids was found to be highly adverse (As and Cr), significant (Al, Cd, Cu, Fe, and Pb), or minimal (Ni and Zn).

Spatial distribution and source apportionment of water pollution in different administrative zones of Wen-Rui-Tang (WRT) river watershed, China

Water quality degradation in river systems has caused great concerns all over the world. Identifying the spatial distribution and sources of water pollutants is the very first step for efficient water quality management. A set of water samples collected bimonthly at 12 monitoring sites in 2009 and 2010 were analyzed to determine the spatial distribution of critical parameters and to apportion the sources of pollutants in Wen-Rui-Tang (WRT) river watershed, near the East China Sea. The 12 monitoring sites were divided into three administrative zones of urban, suburban, and rural zones considering differences in land use and population density. Multivariate statistical methods [one-way analysis of variance, principal component analysis (PCA), and absolute principal component score-multiple linear regression (APCS-MLR) methods] were used to investigate the spatial distribution of water quality and to apportion the pollution sources. Results showed that most water quality parameters had no significant difference between the urban and suburban zones, whereas these two zones showed worse water quality than the rural zone. Based on PCA and APCS-MLR analysis, urban domestic sewage and commercial/service pollution, suburban domestic sewage along with fluorine point source pollution, and agricultural nonpoint source pollution with rural domestic sewage pollution were identified to the main pollution sources in urban, suburban, and rural zones, respectively. Understanding the water pollution characteristics of different administrative zones could put insights into effective water management policy-making especially in the area across various administrative zones.

Stormflow hydrochemistry of a river draining an abandoned metal mine: the Afon Twymyn, central Wales

Contaminated drainage from metal mines is a serious water-quality problem facing nations that exploit metal mineral resources. Measurements of river hydrochemistry during baseflow are common at mine sites, whilst detailed hydrochemical information regarding stormflow is limited and often confined to a single event. This study investigates the seasonal evolution of stormflow hydrochemistry at an abandoned metal mine in central Wales, UK, and the possible sources and mechanisms of metal release. Significant flushing of metals was observed during stormflow events, resulting in concentrations that severely exceeded water-quality guidelines. The relationship between metal concentrations and river discharge suggests dissolution of efflorescent metal sulphates on the surface of the mine spoil as the principal source of the contamination. High fluxes of Pb during stormflows are linked to extended periods of dry weather prior to storm events that produced water table drawdown and encouraged oxidation of Pb sulphide in the mine spoil. However, some Pb flushing also occurred following wet antecedent conditions. It is suggested that Fe oxide reduction in mine spoil and translatory flows involving metal-rich pore waters results in flushing during wetter periods. Detailed measurements of stormflow hydrochemistry at mine sites are essential for accurate forecasting of long-term trends in metals flux to understand metal sources and mechanisms of release, to assess potential risks to water quality and instream ecology, and to gauge the potential effectiveness of remediation. In order to protect riverine and riparian ecosystems, it is suggested that routine monitoring of stormflows becomes part of catchment management in mining-impacted regions.