Submitted in part candidature for an Msc in Environmental Techniques in Earth System Science.

1. The speciation of solute and sediment-bound metals in the mining affected Tisa drainage basin, Eastern Europe. Graham Bird (gbb97@aber.ac.uk) Institute of Geography and Earth Sciences, University of Wales Aberystwyth, Aberystwyth, Ceredigion, SY23 3DB Sampling and Analytical methodologies Surface waters and channel sediments were sampled at 34 sites along the study reach. Samples 1-17 were collected by Macklin et al. (in press) during 2000, samples 18-34 were collected by the author during July 2001. Water samples were filtered through 0.45mm membranes, acidified with HNO3 and analysed for Al, As, Cd, Cu, Hg, Ni, Pb and Zn using ICP-MS. Field measurements of EC and pH were made (Eh was also measured on the Tisa and Cris rivers) at the time of sampling. Given the limitations of Pt electrodes used in Eh meters, values of Eh were calibrated using the Fe2+/Fe3+ redox pair An Eh/pH stability diagram was constructed for As species. Channel sediments were collected using a stainless steel trowel, air-dried and sieved to <63mm. A four-stage SEP adapted from Tessier et al. (1979) was used to identify partitioning analogous to 1) ‘bioavailable’ 2) ‘Fe/Mn oxide’ 3) ‘organic matter/sulphides’ and 4) ‘residual’ phases. Reference materials and blind duplicates were also included. All supernatants were analysed for As, Cd, Cu, Ni, Pb and Zn using ICP-MS. Introduction The speciation of metals in the environment is of primary importance to their toxicity and mobility, perhaps more so than total concentrations. The need to determine the speciation of metals in mining affected fluvial catchments is particularly important where human interaction with the riverine environment is widespread. Solute speciation is governed by the Eh and pH of the aqueous environment. In sediments, metals will be partitioned amongst various organic and inorganic phases of the sediment with differing adsorption strengths. The nature solute speciation and sediment-metal partitioning will affect the environmental significance of metals in the environment. Figure 1: A map showing the sample sites used by this study. The study area Thirty-four samples were were taken along a 828 km trans-boundary study reach comprising the rivers Lapus, Somes, Tisa and Cris. The rivers Lapus and Somes flow through Maramures County in northwest Romania, a region that is extensively mined for base and precious metals. The Baiut mine is situated at the top of the study reach, the River Lapus is also fed by the Rivers Cavnic and Sasar, which drain actively mined land. The River Tisa is dammed between sites 22 and 23. • Study aims • To investigate patterns in metal distribution and metal speciation within the study reach through the use of Eh/pH diagrams and a sequential extraction procedure (SEP). • To assess the environmental significance of metals of metalliferous pollution within the reach and evaluate the importance of trans-boundary metal movement. • The application of a heavy metal pollution index (HPI) to metal concentrations in surface waters. Plate 1: Filtering a surface water sample Plate 2: Collecting channel sediment Solute metal concentrations Metal concentrations in the Lapus and Somes rivers peak downstream of the Baiut mine at sites 1 and 2 and are above EU Maximum Admissible Concentrations (EU MAC). Concentrations reduce downstream of the mine as water pH increases (r2 = 0.8) but peak again downstream of the River Sasar confluence. In the rivers Tisa and Cris concentrations of all metals, except Hg, are below EU MAC and Guide limits and generally below global averages. Table 1: Descriptive statistics of solute metal concentrations Figure 2 indicates downstream patterns of Cd and Hg along the study profile. Cd patterns are typical of Al, As, Cu, Ni, Pb and Zn patterns in the study reach. Solute metal speciation in the rivers Tisa and Cris The rivers Tisa and Cris have a geochemically stable surface water environment (pH range = 7.4 – 8.4, Eh range = 0.18V – 0.21V). This has resulted in a spatially stable pattern of speciation for As, Cd, Cu, Hg, Ni, Pb and Zn as can be seen in Figure 4 in relation to As. Calibrated and uncalibrated Eh/pH relationships generally exhibit similar stability predictions. Potential problems related to toxicity and mobility of metals are mitigated by the low concentrations present in the rivers Tisa and Cris. Hg provides a relevant example of the implications of different species predictions made by calibrated and uncalibrated Eh relationships (Figure 5). Predictions made using the uncalibrated relationship suggest that Hg will be present as Hg2+ ions with SO42- anions compared to the HgO compound predicted using calibrated Eh. Free Hg ions will be more susceptible to conversion to highly toxic organo-mercurials. Sediment-bound metal partitioning Percentage recoveries of summed metal concentrations in each phase versus phase four (Aqua-Regia soluble) repeats; suggest a good experimental and analytical performance. Mean recovery was 93 percent, with the negative discrepancy a likely result of slight dilution effects during the use of the SEP. Partitioning patterns were spatially stable particularly along the River Tisa as indicated by Cd in Figure 6, the figure also indicates the importance of ‘organic matter/sulphides’ near to the Baiut mine (six-metal mean partitioning of 96%). Table 2 shows the dominant phase to which each metal was partitioned in along the Romanian and Hungarian sections of the study reach. To remove the skewing effect site 1 was omitted from mean calculations. Cd and Zn are strongly associated with the ‘bioavailable’, the similar partitioning patterns of these two metals is unsurprising given their close geochemical association. Table 2: Dominant partitioning of metals Figure 7 indicates that at sites where sediment-metal concentrations of As, Cd and Zn exceed New Dutch List ‘action’ values the environmental significance of Cd and Zn is generally much greater due to dominant partitioning in the ‘bioavailable’ fraction. Figure 4: Stability of As species predicted using Eh and pH. Al As Cd Cu Hg Ni Pb Zn Lapus/Somes Mean 152 11.7 13.3 172 0.8 48.9 36.7 2169 Range 390-884 1.3-124 0.0-143 1.6-2118 nd-1.5 6.7-448 4.6-389 12.9-17611 Tisa/Cris Mean 9.4 2.4 0.1 1.9 4.8 1.2 0.8 5.4 Range 2.1-75 1.5-3.9 nd-0.6 0.5-3.5 0.4-26.6 0.6-1.9 nd-2.8 nd-52 Calibrated Eh Uncalibrated Eh Cris Tisa Tisa Lapus Somes Figure 5: Partitioning of Cd within channel sediments. Figure 5: Stability of Hg species predicted using Eh and pH No data point = concentration is non-detectable Rivers Lapus and Somes Rivers Tisa and Cris As ‘Residual’ (65.8%) ‘Residual’ (79.1%) Cd ‘Bioavailable’ (72.1%) ‘Bioavailable’ (73.9%) Cu ‘Fe/Mn oxides’ (31.1%) ‘Residual’ (40.3%) Ni ‘Residual’ (42.1%) ‘Residual’ (54%) Pb ‘Fe/Mn oxides’ (77.9%)‘Fe/Mn oxides’ (65.4%) Zn ‘Bioavailable’ (51.1%) ‘Fe/Mn oxides’ (37.7%) Calibrated Eh Uncalibrated Eh Figure 2: Cd and Hg concentrations in surface waters. Heavy Metal Pollution Index (HPI) The index was developed by Mohan et al. (1996) for the assessment of groundwater pollution. The HPI is a arithmetic mean quality method based upon a composite of measured concentrations for a number of metals versus water quality guidelines (EC 80/778/EEC). Figure 3 highlights HPI values calculated at each site, values exceeding 100 indicate water is unfit for human consumption. Removal of Hg from the HPI reduces all coefficients for the rivers Tisa and Cris to <10. • Conclusions • Water and sediment geochemistry on the River Lapus are influenced by the Baiut mine, however with increasing distance downstream the influence of local point sources and background geochemistry increase. • The HPI can be seen to be a highly useful quantitative approach to assessing water quality and suggests water especially in the River Tisa should not be used for human consumption. • The influence of speciation upon toxicity and mobility of solute metals in the River Tisa is mitigated by low concentrations and alkaline pH. Hg is more problematic due to potential for conversion to organo-mercurials. • Partitioning of sediment-bound metals is spatially stable, especially in the River Tisa. The Baiut mine exerts an influence in the upper Lapus with metals bound to the ‘sulphide’ phase. • Cd and Zn are ‘environmentally significant’ due to association with the ‘bioavailable’ phase, especially a pollution hot-spots in the Lapus and Somes. As is ‘environmentally insignificant’ due to its dominant association with the ‘residual phase’. As Cd Zn ‘Bioavailable’ ‘Fe/Mn oxides’ ‘Organic/sulphides’ ‘Residual’ • References • Mohan S. V., Nithila P., and Reddy S. J. (1996): ‘Estimation of heavy metals in drinking water and development of heavy metal pollution index.’ Journal of Environmental Science and Health (A31) pp283-289 • Tessier A., Campbell P. G. C. and Bisson M. (1979): ‘Sequential extraction procedure for the speciation of trace metals.’ Analytical Chemistry (51) pp844-851. Lapus Somes Tisa Cris Figure 3: Calculated HPI values for individual sample sites. Figure 7: Partitioning of As, Cd and Zn at pollution hot-spots. Submitted in part candidature for an Msc in Environmental Techniques in Earth System Science. 1st October 2001