Jürg Zobrist

CHEMICAL WEATHERING OF SILICATE ROCKS AS A FUNCTION OF ELEVATION IN THE SOUTHERN SWISS ALPS

Surface water and soil samples were collected from a series of small catchments on granitic gneiss in the Canton of Ticino in southern Switzerland. Elevations of the sampling points ranged from 220 to 2400 m; vegetation varied correspondingly from deciduous forest through coniferous forest to alpine pasture and essentially unvegetated rock and talus. Annual precipitation averaged 1.9 to 2.4 m. The concentrations of the major cations and silica in surface waters decreased more or less exponentially with elevation. The cationic denudation rate decreased from about 500 meq/m2 · y at the lower elevations to about 20 meq/m2 · y at the highest. Alkalinity decreased from 250 to about −7 μeq/1. Although total concentrations decreased with elevation, there were no clear systematic trends in the ratios of the concentrations of the major cations and silica. This suggests that the nature of the secondary minerals formed during weathering in the area does not change with elevation, despite great changes in soil type and environmental conditions. The clay mineralogy of the soils is dominated by unweathered and slightly weathered bedrock minerals: mica and chlorite, hydrobiotite, and poorly characterized mixed-layer material. Small amounts of kaolinite and smectite were observed in a few samples, but there do not appear to be any systematic trends in clay mineralogy with elevation. Mass-balance arguments suggest that the major (in terms of solute generation) weathering product is either kaolinite or a mixture of A1(OH)3 and 2:1 clays. The lack of dependence of weathering stoichiometry on elevation (a surrogate for several environmental variables) or solute concentrations perhaps reflects the importance of local relief, which did not vary systematically with elevation.

Biogeochemical changes in groundwater-infiltration systems: Column studies

A laboratory continuous flow-through sand reactor was used to study qualitatively and quantitatively the biogeochemical processes resulting from an input of an easily degradable organic substance (lactate) into a model aquifer. The primary occurring redox processes are mediated by microorganisms and can be described by the classical sequence of inorganic redox reactions in aquatic systems. In the steady state situation, the nitrate and sulfate reduction follow a pseudo first-order kinetics, with respective rate constants of (2.7 +/- 0.2) . 10(-1) min-1 and (2.3 +/- 0.3) . 10(-2) min-1. These rate constants are within the same range of other laboratory and field studies when taking the population densitv of microorganisms into account.

Case studies on the chemical composition of fogwater: The influence of local gaseous emissions

Abstract In order to study the mechanisms governing the composition of fogwater, sequential samples were taken during two fog events over several hours and analyzed chemically. In addition, preliminary measurements of gases (HCl, HNO 3 , NH 3 ) and aerosols (H 2 SO 4 , NH 4 NO 3 , NH 4 Cl and ammonium sulfates) were made. The uptake of gaseous HCl in the fog droplets was a major source of acidity: in extreme cases pH values of 2.08 and 1.94 and Cl − concentrations up to 10 −2 M were observed. HCl originated from a local source, most probably a refuse incinerator from which plumes of the stack gas reached the sampling site. The NH + 4 , NO − 3 and SO −2 4 concentrations (in the range of 0.1–2 mrnol l −1 ) were regulated by the inputs of aerosols and the liquid water content of the fog. The contribution of dissolved S(IV) (0.06–0.27 mmol l −1 ) to the total aqueous sulfur varied with time, according to the pH-dependent solubility of SO 2 and to oxidation reactions.

Sulfide oxidation and acid mine drainage formation within two active tailings impoundments in the Golden Quadrangle of the Apuseni Mountains, Romania

Sulfidic mine tailings have to be classified as one of the major source of hazardous materials leading to water contamination. This study highlights the processes leading to sulfide oxidation and acid mine drainage (AMD) formation in the active stage of two tailings impoundments located in the southern part of the Apuseni Mountains, in Romania, a well-known region for its long-term gold-silver and metal mining activity. Sampling was undertaken when both impoundments were still in operation in order to assess their actual stage of oxidation and long-term behavior in terms of the potential for acid mine drainage generation. Both tailings have high potential for AMD formation (2.5 and 3.7 wt.% of pyrite equivalent, respectively) with lesser amount of carbonates (5.6 and 3.6 wt.% of calcite equivalent) as neutralization potential (ABA=-55.6 and -85.1 tCaCO(3)/1000 t ) and showed clear signs of sulfide oxidation yet during operation. Sequential extraction results indicate a stronger enrichment and mobility of elements in the oxidized tailings: Fe as Fe(III) oxy-hydroxides and oxides (transformation from sulfide minerals, leaching in oxidation zone), Ca mainly in water soluble and exchangeable form where gypsum and calcite are dissolved and higher mobility of Cu for Ribita and Pb for Mialu. Two processes leading to the formation of mine drainage at this stage could be highlighted (1) a neutral Fe(II) plume forming in the impoundment with ferrihydrite precipitation at its outcrop and (2) acid mine drainage seeping in the unsaturated zone of the active dam, leading to the formation of schwertmannite at its outcrop.

Community Perception of Water Quality in a Mining-Affected Area: A Case Study for the Certej Catchment in the Apuseni Mountains in Romania

Mining-contaminated sites and the affected communities at risk are important issues on the agenda of both researchers and policy makers, particularly in the former communist block countries in Eastern Europe. Integrated analyses and expert based assessments concerning mining affected areas are important in providing solid policy guidelines for environmental and social risk management and mitigation. Based on a survey for 103 households conducted in a former mining site in the Certej Catchment of the Apuseni Mountains, western Romania, this study assesses local communities’ perceptions on the quality of water in their living area. Logistic regression was used to examine peoples’ perception on the quality of the main river water and of the drinking water based on several predictors relating to social and economic conditions. The results from the perception analysis were then compared with the measurements of heavy metal contamination of the main river and drinking water undertaken in the same study area. The findings indicate that perception and measurement results for the water quality in the Certej Catchment are convergent, suggesting an obvious risk that mining activities pose on the surface water. However, the perception on drinking water quality was little predicted by the regression model and does not seem to be so much related to mining as to other explanatory factors, such as special mineralogy of rock and soils or improper water treatment infrastructure, facts suggested by the measurements of the contaminants. Discussion about the implications of these joint findings for risk mitigation policies completes this article.

Steady-state modelling of biogeochemical processes in columns with aquifer material 1. Speciation and mass balances

A laboratory column containing aquifer sand was used to study biogeochemical processes occurring in groundwater. As a carbon source for the microbially mediated processes, lactate was introduced into the system.

Experimental study and steady-state simulation of biogeochemical processes in laboratory columns with aquifer material.

Packed bed laboratory column experiments were performed to simulate the biogeochemical processes resulting from microbially catalyzed oxidation of organic matter. These included aerobic respiration, denitrification, and Mn(IV), Fe(III) and SO(4) reduction processes. The effects of these reactions on the aqueous- and solid-phase geochemistry of the aquifer material were closely examined. The data were used to model the development of alkalinity and pH along the column. To study the independent development of Fe(III)- and SO(4)-reducing environments, two columns were used. One of the columns (column 1) contained small enough concentrations of SO(4) in the influent to render the reduction of this species unimportant to the geochemical processes in the column. The rate of microbially catalyzed reduction of Mn(IV) changed with time as evidenced by the variations in the initial rate of Mn(II) production at the head of the column. The concentration of Mn in both columns was controlled by the solubility of rhodochrosite (MnCO(3(S))). In the column where significant SO(4) reduction took place (column 2), the concentration of dissolved Fe(II) was controlled by the solubility of FeS. In column 1, where SO(4) reduction was not important, maximum dissolved Fe(II) concentrations were controlled by the solubility of siderite (FeCO(3(S))). Comparison of solid-phase and aqueous-phase data suggests that nearly 20% of the produced Fe(II) precipitates as siderite in column 1. The solid-phase analysis also indicates that during the course of experiment, approximately 20% of the total Fe(III) hydroxides and more than 70% of the amorphous Fe(III) hydroxides were reduced by dissimilatory iron reduction. The most important sink for dissolved S(-II) produced by the enzymatic reduction of SO(4) was its direct reaction with solid-phase Fe(III) hydroxides leading initially to the formation of FeS. Compared to this pathway, precipitation as FeS did not constitute an important sink for S(-II) in column 2. In this column, the total reacted S(-II) estimated from the concentration of dissolved sulfur species was in good agreement with the produced Cr(II)-reducible sulfur in the solid phase. Solid-phase analysis of the sulfur species indicated that up to half of the originally produced FeS may have possibly transformed to FeS(2).

Water Chemistry of Swiss Alpine Rivers

Average concentrations of dissolved nutrients (NO3, DRP, K) in the large alpine rivers Rhine, Rhone, Ticino, and Inn, and in small alpine streams and glacier streams, are low compared to those in midland rivers. Concentrations of NO3 in the large rivers clearly exceed background concentrations. In spite of limited anthropogenic activities in alpine catchments, DRP concentrations in large rivers exhibited a downward trend over the last 30 years. Time series of NO3 concentrations were first increasing and then leveled off. Export coefficients of NO3 and DRP in alpine streams fall in the range of those estimated for nonagricultural lands and forests on the Swiss Plateau.

Mining and the environment.

Metal ores and coal are mined in large quantities: for nonferrous metals alone, total global annual production amounts to approximately 50×10 t (50 Mt, Lottermoser 2010). Mining products are vital and indispensable to our modern society and contribute significantly to our wealth. Currently, the monetary value of global copper and gold production amounts to about €100,000 million/year for each of these metals. On the other hand, mining and the mineral processing steps associated with them generate huge amounts of wastes, some of which are chemically reactive. Whereas the annual production rates of metals or coal can be determined fairly well, appraising the amount of mining waste deposited in a country or continent is a very challenging task, and any estimates are necessarily rough. A country-by-country inventory for the European Union in 1999 assessed the quantity of stored waste rock—mainly overburden material—as 4,700 Mt and that of the processing wastes or tailings as 1,200 Mt (BRGM 2001). In the opinion of the authors of this study, the quantities reported represented lower limits to the actual quantities involved. The authors also noted that differences in the national regulations of the 13 EU member countries resulted in a degree of uncertainty in the data collected. Globally, material flows of mine waste by far exceed those of waste from non-mining industries and of municipal waste. Heaps of waste rock covering land surfaces is estimated to require about 1 to 3 ha/Mt of solid waste. These piles may generate dust and discharge fine particles into surface waters, and they also deface the local landscape: open-pit mining operations, for instance, leave large cavities in the scenery. Leachates from overburden and gangue materials that do not contain a substantial amount of sulphidic minerals create seldom a chemical water quality problem. By contrast, deposits of processing wastes (tailings) often have a severe impact on all types of natural waters. The extraction of non-ferrous metals from sulphidic ores has been going on for a long time. Because such ores contain pyrite in notable concentrations, the tailings also contain pyrite, often in a finely milled form. Pyrite, and to a smaller extent additional other pyritic minerals, are oxidised when they come into contact with air. Together with percolating water, this produces a leachate containing sulphuric acid, known as acid mine drainage (AMD) or acid rock drainage. The acid produced by the oxidation of sulphidic minerals dissolves various other minerals that may contain heavy metals, arsenic and other hazardous elements. AMD, its acidity and the resulting elevated concentrations of noxious substances represent the key issue when assessing the risk to natural waters and soils posed by mine tailings. Coal deposits also contain pyritic minerals. Hence, the outflows from underground mines and open-pit lakes often turn acidic. Physically unstable tailing dams are at risk of bursting during heavy rainfall, potentially causing a disastrous mudflow. Such events attract widespread attention in the media, whereas the chronic impacts of AMD are hardly ever reported on. The formation of AMD is a slow process that continues even after mining operations have ceased. Therefore, the outflows from abandoned mines and tailings—several thousands of orphaned sites exist in the EU—also need to be investigated. The monitoring data gained need to be assessed in relation to the risk that contamination poses to ecological and human health. Such results and monitoring data represent one starting point for remedial measures. Often, such measures are very costly, and a natural attenuation approach is sometimes the only feasible solution. The most important key point for remediation is understanding the biogeochemical behaviour of the constituents of the tailings both in general and under the specific climatic and hydrological conditions prevailing at a particular site. Severe failures in tailing handling have resulted in environmental disasters such as the Ajka red mud spill in Hungary in 2010 (Mayes et al. 2011) and the Baia Mare and Baia Borse Responsible editor: Philippe Garrigues

ESTROM 2008 International Conference

The target audience for the conference was environmental scientists and engineers, water managers, and environment and health authorities. In addition, organizations dealing with the protection of water bodies, e.g., the International Commission for the Protection of the Danube River (ICPDR), stakeholders, nongovernmental organizations, decision makers, and drinking water suppliers, were addressed. The Organizing Committee consisted of Walter Giger, Jurg Bloesch, and Jurg Zobrist (Eawag, Dubendorf, Switzerland), Nicolae Panin and Alina Pavel (Institute GeoEcoMar, Bucharest, Romania), Viorel Ungureanu (University of Bucharest, Romania), Elisabeth Schenker (Swiss National Science Foundation, Bern, Switzerland), and Paolo Demaria (Demaria Event Management, Zurich, Switzerland). Summarized oral reports of the nine ESTROM projects concerning contaminants in wastewaters, surface waters and sediments, and drinking waters of Romania, monitoring and mitigation of pollution, and implementation of respective measures were also presented. The conference was opened by Prof. Anton Anton, State Secretary of the Romanian Ministry of Education, Research and Youth and President of the National Authority of Scientific Research. He welcomed 120 participants from 17 countries (Fig. 1) and reflected in his lively speech on the special current situation of research activities in Romania. Dr. Simon Geissbuhler, Charge d’affaires of the Swiss Embassy in Romania, emphasized the importance of Swiss–Romanian cooperation by stressing that each side can learn from the other, also in the sector of scientific research and environmental protection. The conference was organized in five half-day sessions, of which each included one keynote lecture, two topic talks, and one or two reports of the ESTROM projects. During the whole conference, 46 posters were on display (ESTROM 2008; Fig. 2). The following sections overview the oral presentations of sessions 1 to 5 and the podium discussion. Detailed reports on the ESTROM projects are presented in separate articles contained in this Special Issue of Environmental Science and Pollution Research (see references). The presentations are also downloadable as digital files (ESTROM 2008). Environ Sci Pollut Res (2009) 16 (Suppl 1):S9–S13 DOI 10.1007/s11356-009-0206-5