IMPACT OF METAL MINING ON THE WATER QUALITY IN THE TAMAR CATCHMENT

This study discusses the effects of past mining activities on sediment and water quality in streams and rivers in the Tamar catchment. High trace element concentrations, both in water and sediments, were observed in streams and rivers draining areas associated with abandoned mine sites. Maximum concentrations were observed in the Gunnislake/Calstock mining district, where intense metalliferous mining took place during the 19th century. Mine waste from abandoned mine sites in this area contained up to 6.3% arsenopyrite, 5.8% pyrite, 0.3% chalcopyrite and 24% scorodite. As a result, high concentrations of trace elements of up to 180000 mg kg‾¹ As, 6500 mg kg‾¹ Cu were determined in these wastes. Sequential extraction of the mine waste revealed that in most cases, the oxidisable fraction accounted for large proportions of mobile species, followed by the reducible fraction. The exchangeable fraction was relatively low, except for Cu in samples from fine grained waste heaps, in which significant amounts of secondary minerals, such as Fe oxides/oxyhydroxides and Fe-As-O minerals were observed, suggesting trace elements had the tendency to be retained and recycled within the fine grained waste heaps. The Fe oxides/oxyhydroxides can contain up to 12% As and Fe-As-O minerals can contain up to 25% As and 6% Cu, indicating that the As and Cu associated with Fe oxide phases represent their reducible fraction. The coarse grained waste heaps, with higher permeability and low cohesion characteristics, had a higher potential to produce acid leachate and were more susceptible to erosion than the fine grained waste heaps. Contaminants from abandoned mine sites entered aquatic systems within the catchment, as shown by the high concentrations of trace elements (up to 25000 mg kg‾¹ As, 28000 mg kg‾¹ ' Cu, 32000 mg kg‾¹ Mn, 9200 mg kg‾¹ Pb and 2700 mg kg‾¹ Zn) observed in sediments in water channels draining these mine sites. Some streams and adits draining abandoned mine sites carried acidic waters with pH values frequently below pH 4. Dissolved concentrations up to 560 μg L‾¹ As, 7600 μg L‾¹ Cu, 3800 μg L‾¹ Fe, 5700 μg L‾¹ Mn, 170 pg L‾¹ Pb and 2500 μg L‾¹ Zn, and particulate concentrations up to 1600 μg UI As, 7900 μg L‾¹ Fe, 290 pg U' Ni, 11 pg U' Pb and 91 μg L-¹ Zn were observed in channels draining abandoned mine sites. In total, the annual flux of trace elements from 25 studied streams and adits input ca. 13,000 kg Fe, 4300 kg Mn, 4200 kg Cu, 3600 kg Zn, 1400 kg As, 400 kg Ni, 350 kg Co, 43 kg Pb, and 6.6 kg Cd into the Tamar estuary. Seven important point sources of metals to the River Tamar were identified. The mass balance calculation revealed that over 50% of trace elements were not accounted for by the studied point sources, suggesting an importance of diffuse sources. The inputs of solid and dissolved contaminants from the intensive mining district affect the water and sediment quality of the Tamar estuary, an important ecosystem in southwest England. This work has provided important information on the relative importance of point and diffuse sources, ‾which is essential in the formulation of effective catchment management strategie

Lead pollution of coastal sediments by ceramic waste

© 2018 Ceramic fragments and fractionated (<2 mm) sediment have been sampled from two beaches in southwest England, along with sediment from a control beach where ceramic waste was lacking. Analysis of the glazed ceramic surfaces by X-ray fluorescence (XRF) spectrometry returned concentrations of Pb up to 729,000 mg kg−1, while XRF analysis of sediment samples revealed high but heterogeneous concentrations of Pb at the two sites impacted by ceramic waste (median = 292 and 737 mg kg−1) compared with the control beach (median ~ 20 mg kg−1). These observations are attributed to the disposal of contemporary and historical ceramic products, and the subsequent attrition of material and contamination of local sediment. Extraction of a milled ceramic composite (Pb = 2780 mg kg−1) by 1 M HCl, revealed a high (34%) environmental mobility and availability of Pb; extraction in a solution of protein, however, suggested a low (0.1%) bioaccessibility to sediment-ingesting invertebrates

Physicochemical composition of wastes and co-located environmental designations at legacy mine sites in the south west of England and Wales: Implications for their resource potential

© 2016 This work examines the potential for resource recovery and/or remediation of metalliferous mine wastes in the south west of England and Wales. It does this through an assessment of the physicochemical composition of several key metalliferous legacy mine waste piles and an analysis of their co-location with cultural, geological and ecological designations. Mine waste samples were taken from 14 different sites and analysed for metal content, mineralogy, paste pH, particle size distribution, total organic carbon and total inorganic carbon. The majority of sites contain relatively high concentrations (in some cases up to several % by mass) of metals and metalloids, including Cu, Zn, As, Pb, Ag and Sn, many of which exceed ecological and/or human health risk guideline concentrations. However, the economic value of metals in the waste could be used to offset rehabilitation costs. Spatial analysis of all metalliferous mine sites in the south west of England and Wales found that around 70% are co-located with at least one cultural, geological and ecological designation. All 14 sites investigated are co-located with designations related to their mining activities, either due to their historical significance, rare species assemblages or geological characteristics. This demonstrates the need to consider the cultural and environmental impacts of rehabilitation and/or resource recovery on such sites. Further work is required to identify appropriate non-invasive methodologies to allow sites to be rehabilitated at minimal cost and disturbance

Lead mobilisation in the hyporheic zone and river bank sediments of a contaminated stream : contribution to diffuse pollution

Purpose Past metal mining has left a legacy of highly contaminated sediments representing a significant diffuse source of contamination to water bodies in the UK and worldwide. This paper presents the results of an integrated approach used to define the role of sediments in contributing to the dissolved lead (Pb) loading to surface water in a mining-impacted catchment. Materials and methods The Rookhope Burn catchment, northern England, UK, is affected by historical mining and processing of lead ore. Quantitative geochemical loading determinations, measurements of interstitial water chemistry from the stream hyporheic zone, and inundation tests of bank sediments were carried out. Results and discussion High concentrations of Pb in the sediments from the catchment, identified from the British Geological Survey (BGS) Geochemical Baseline Survey of the Environment (GBASE) data, demonstrate both the impact of mineralisation and widespread historical mining. The results from stream water show that the stream Pb load increased in the lower part of the catchment, without any apparent or significant contribution of point sources of Pb to the stream. Relative to surface water, the interstitial water of the hyporheic zone contained high concentrations of dissolved Pb in the lower reaches of the Rookhope Burn catchment, downstream of a former mine washing plant. Concentrations of 56 μg l-1 of dissolved Pb in the interstitial water of the hyporheic zone may be a major cause of the deterioration of fish habitats in the stream and be regarded as a serious risk to the target of good ecological status as defined in the European Water Framework Directive. Inundation tests provide an indication that bank sediments have the potential to contribute dissolved Pb to surface water. Conclusions The determination of Pb in the interstitial water and in the inundation water, taken with water Pb mass balance and sediment Pb distribution maps at the catchment scale, implicate the contaminated sediments as a large Pb supply to surface water. Assessment of these diffuse contaminant sources is critical for the successful management of mining-impacted catchments

Sediment fingerprinting in agricultural catchments: A critical re-examination of source discrimination and data corrections

Fine sediment source fingerprinting techniques have been widely applied in agricultural river catchments. Successful source discrimination in agricultural environments depends on the key assumption that land-use source signatures imprinted on catchment soils are decipherable from those due to other landscape factors affecting soil and sediment properties. In this study, we re-examine this critical assumption by investigating (i) the physical and chemical basis for source discrimination and (ii) potential factors that may confound source un-mixing in agricultural catchments, including particle size and organic matter effects on tracer properties. The study is situated in the River Tamar, a predominantly agricultural catchment (920km2) in south-west England that has also been affected by mining. Source discrimination focused on pasture and cultivated land uses and channel banks. Monthly, time-integrated suspended sediment samples were collected across seven catchments for a 12-month period. Physical and chemical properties measured in source soils and sediment included fallout radionuclides (137Cs, excess 210Pb), major and minor element geochemical constituents, total organic carbon and particle size. Source discrimination was entirely dependent on differences in tracer property concentrations between surface and sub-surface soils. This is based on fallout radionuclide concentrations that are surface-elevated, while many geochemical properties are surface-depleted due to weathering and pedogenetic effects, although surface soil contamination can reverse this trend. However, source discrimination in the study catchments was limited by (i) rotation of cultivated and pasture fields resulting in reduced differences between these two sources, and (ii) the cultivated source signature resembling a mix of the pasture and channel bank sources for many tracer properties. Furthermore, a combination of metal pollution from abandoned historic mines and organic enrichment of sediment from upland areas of peaty soils resulted in the non-conservative behaviour of some tracer properties in several catchments. Differences in the particle size and organic carbon content of source soils could explain much of the variation in these properties in downstream sediment, rather than selective transport effects. Inconsistent relationships between particle size, organic carbon and tracer property concentrations further undermined the basis for the use of widely applied corrections to tracer datasets. Sensitivity analysis showed that correcting source tracer data for differences in organic matter can produce large changes to source contribution estimates that cannot be justified, and such corrections should not be used. Confounding factors related to poor source discrimination and non-conservative behaviour are highly likely to affect sediment fingerprinting studies in many agricultural catchments. As a result, estimates of source contributions in many fingerprinting studies may contain significant unquantified errors. © 2013 Elsevier B.V

Microbial recovery of metallic nanoparticles from industrial wastes and their environmental applications

"In recent years, metallic nanoparticles (NPs) have been produced by biological methods using bacteria and have been used with remarkable environmental applications. This paper emphasizes the basic aspects of microbial synthesis of metallic nanoparticles, from the selection of the strain to the settings of reaction parameters. Mechanisms involved in the microbial production of NPs are also discussed, summarizing general findings and implications in the process. There is also a section dedicated to the identification of wastes as a source of precious metals and the production of metallic NPs from waste streams containing ionic metals to give a vision of the opportunities to implement microbial synthesis as a treatment–recovery technology. Environmental applications of biogenic NPs are reviewed in detail indicating that the implementation of these nanomaterials enable the achievement of higher removal efficiencies and greater extent of transformation of recalcitrant compounds in wastewater treatment systems. Under this scenario and based on the information reviewed concluding remarks and futures perspectives are enunciated. © 2018 Society of Chemical Industry.