Environmental impact and remediation of acid mine drainage: a management problem

 Work carried out at the abandoned copper (Cu) and sulphur (S) mine at Avoca (south east Ireland) has shown acid mine drainage (AMD) to be a multi-factor pollutant. It affects aquatic ecosystems by a number of direct and indirect pathways. Major impact areas are rivers, lakes, estuaries and coastal waters, although AMD affects different aquatic ecosystems in different ways. Due to its complexity, the impact of AMD is difficult to quantify and predict, especially in riverine systems. Pollutional effects of AMD are complex but can be categorized as (a) metal toxicity, (b) sedimentation processes, (c) acidity, and (d) salinization. Remediation of such impacts requires a systems management approach which is outlined. A number of working procedures which have been developed to characterise AMD sites, to produce surface water quality management plans, and to remediate mine sites and AMD are all discussed. Received: 16 January 1996 · Accepted: 5 March 1996     

酸雨对水生态系统中一些生物的影响

本文综述酸雨对水生态系统中各营养级生物的影响。介绍酸雨引起水体酸化和水体的缓冲能力,阐述不同营养级水生生物和所处不同发育阶段对低pH的敏感性差异。还讨论了由于遗传和适应引起生物对低pH的耐受性差异。酸化水体生物群落的重要特征是,生物种类数减少,多样性降低,生物量减少和食物链遭破坏。酸性pH对水生生物的毒作用方式包括气体交换受阻、体盐调节紊乱、酸碱平衡失调,以及与金属的联合作用等.最后还对若干问题作了扼要讨论,并提出建议。     

Supergene processes on ore deposits—a source of heavy metals

The study of supergene processes (i.e., secondary processes running in ore deposits and driven by thermodynamic nonequilibrium between ore-and rock-forming minerals and natural waters, gasses, etc.) is important in order to understand the migration of heavy metals from ore into their adjacent surroundings. The contamination of the local environment can be characterized by the composition of pore waters. The Pb-Zn-Cu ore deposits of Zlaté Hory (Czech Republic) have been chosen for a detailed study of pore solutions. A simple model has been created to describe the evolution of supergene processes in the ore deposits. This model is based on the determination of chemical composition of pore solutions. The dilution of pore solutions of such mineral deposits results in acid mine drainage. Pore solutions can have, during specific stages of their evolution, relatively high concentrations of Cu (0.09 mol/kg), Zn (0.1 mol/kg), SO₄ (0.8 mol/kg) and an extremely low pH (1.38). The supergene alteration of pyrite is the most important process determining the character of pore water. This reaction causes significant acidification and is a leading source of acid mine drainage. The leached zone originates from the interaction of pyrite and limonite. Increased concentrations of heavy metals and sulfates occur in pore waters. The dynamic composition of pore waters within ore deposits undergoing the supergene process can be used to distinguish: (1) three main zoneslimonite, transition, and primary zone and (2) two areas—an area with the highest intensity of weathering processes and an area of weathering initiation. In these areas the rate of sulfide oxidation is higher as a result of low pH. From the study of these zones and areas we can further our knowledge of ore body, pore solution, acid mine drainage, and contamination of the local environment.     

Rainwater composition over a rural area with special emphasis on the size distribution of insoluble particulate matter

The rainwater composition in the vicinity of Mainz, FRG, has been investigated with special emphasis on insoluble constituents. The number size distribution was determined in the range from 0.1 m up to 100 m radius. For particles with r>0.5 m radius the shape of the size distribution of insoluble particles in rain follows the shape of the average urban and rural aerosol. In this particular size range no major size selective removal processes could be seen. For r<0.5 m the number size distribution tends to flatten compared to the average aerosol. This might be the indication of a size selective removal process (Greenfield Gap).     

Wet deposition due to fog in the Po Valley,Italy

Wet deposition due to radiation fog is examined in this paper. The area where the reported measurements were performed, the Po Valley, northern Italy, is characterized by both a high fog occurrence during the fall-winter months and fog water solutions of high ionic concentration and acidity.Estimated wet deposition for NH ₄ ⁺ , NO _inf3 ^sup- and SO _inf4 ^sup2- ions due to fog droplet settling to the ground accounts for 13.2, 12.1 and 5.3 percent with respect to bulk precipitations over the same period: January–March and October–December (fog season).Fog deposition rates show that this process can be an important pathway of trace gases and particles loss from the air. First indicative results of fog removal efficiency with respect to air particulate matter are presented.Dry deposition parameters should be taken into account in evaluating the potential effect of fog droplet deposition on vegetation.     

Environmental impact of the acid fumarolic plume of a passively degassing volcano (Vulcano Island,Italy)

This paper investigates the role played by the fumarolic plume of a passive degassing volcano in the genesis of rock coatings (RC) and in the introduction and re-distribution of metals and trace elements in the surficial environment. At La Fossa active volcano (Vulcano Island) and in the surrounding environment RC develop owing to exposure of the ground surface to the volcanic acid plume produced by the passive degassing of La Fossa. Significant positive anomalies of a wide variety of metals and trace elements (including Bi, Ag, Se, Te, Sb, Pb, As, Cu, Tl and Cd) were observed either in distal and proximal RC. Most of these anomalies are interpreted to be the result of the transport and subsequent deposition of trace elements, likely to form volatile compounds, in the fumarolic plume. Two main processes seem to control the geochemistry of RC: one is represented by the leaching and subsequent deposition of elements from the proximal toward the distal RC; the other is the direct input of trace elements carried by the emitted volcanic aerosol. The fact that most of the trace elements (particularly Pb, As, Tl, Bi, Te, Se, Cd) enriched in the RC of Vulcano are highly toxic and potentially dangerous to health in high concentration, indicates that the atmospheric metal injection by the quiescently degassing La Fossa volcano together with the subsequent deposition and remobilization by means of surficial waters may represent an environmental hazard that should be taken into account in evaluating the potential impact of volcanic air pollution on human health.     

Assessing desertification

It is widely recognized that desertification is a serious threat to arid and semiarid environments—which cover 40% of the global land surface and are populated by approximately 1 billion humans. Given the potential relevance of this problem, it is surprising that there is no consensus on the proper way to assess the desertification status of a piece of land. During the last 70 years, conflicting definitions have produced both different assessment methodologies and divergent estimates. Contrary to conceptual issues on desertification, assessment methodologies have not been reviewed comprehensively. Here, we critically review the most common methodologies to assess desertification, and describe their principal consequences on scientific and social arenas.We show that desertification assessment has shifted from simple appraisals of the interannual movement of desert boundaries to complex multivariate field surveys, to practical methodologies based on indicators of ecosystem functioning, such as rain use efficiency. Although often regarded as an evidence of stagnation and failure, these methodologies reflect the progress that desertification ecology has experienced. Future challenges for properly assessing desertification are (1) the lack of reference situations against which actual desertification could be compared, and (2) the difficulties that appear when desertification operates through structural rather than functional ecosystem changes.The coexistence of conflicting definitions and divergent estimates negatively affects societal perception, leading to scepticism and, ultimately, to a delay of eventual solutions. Societies must recognize the progress desertification ecology has made, leave behind concepts that no longer represent current knowledge, grasp the opportunity to better assess the extent and intensity of the problem, and, for the time being, realize that assessing desertification is an unsolved issue.     

Mineral formation in an acid pit lake from a high-sulfidation ore deposit: Kirki, NE Greece

Open pit mining of base-metals from the high-sulfidation epithermal type deposit of Kirki (Thrace, NE Greece) resulted in the formation of an acid pit lake by infilling of the open cast by rain and draining waters after mine closure. The high toxic metals content of the ore, the limited buffering capacity of host rocks and the direct exposure of the ore zone to weathering result in an intense release of metals into the pit lake. The acidic and oxidative pit lake waters show high concentrations of trace metals. A mineral precipitate, covering the floor of the pit lake, comprises secondary anglesite, several species of the jarosite-group, rozenite, melanterite, wroewolfeite, gypsum, bukovskyite, beaverite, scorodite and minor goethite. The mineral precipitate presents a significant heavy metal content indicating effective removal of metals from the acid waters. Compared to other pit lakes in high-sulfidation type deposits it has a higher metal load, consistent with the mineralogy and grade of ore in pit walls.     

Rainfall interception in three contrasting lowland rain forest types in Central Kalimantan, Indonesia

Rainfall interception was quantified and modeled for a Lowland Evergreen Rain Forest (LERF) and two Heath Forests (HF) of contrasting stature during a one-year period at a remote site in Central Kalimantan, Indonesia. Throughfall was measured using a roving gauge approach using 18–20 gauges per forest type. Throughfall was 82.8% of incident rainfall in the LERF vs. 89.1% in tall HF and 76.7% in stunted HF. Corresponding stemflow fractions were 0.8%, 1.3% and 2.0% of rainfall, respectively. Interception losses derived for the LERF (16.4%) and the tall HF (9.6%) were close to findings obtained for similar forest types elsewhere but the high interception loss for the stunted HF (21.3%) was unexpected. On the basis of canopy structural characteristics and wet canopy evaporation modeling it is concluded that throughfall in the stunted HF was underestimated and that the specific nature of the HF required a more intensive sampling arrangement. Throughfall sampling schemes in tropical forests, associated errors and hydrological implications are discussed.     

Tectonically induced climate and its control on the distribution of depositional systems in a continental foreland basin, Cloverly and Lakota Formations (Lower Cretaceous) of Wyoming, U.S.A.

Continental sediments of the Cloverly and Lakota Formations (Lower Cretaceous) in Wyoming are subdivided into three depositional systems: perennial to intermittent alluvial, intermittent to ephemeral alluvial, and playa. Chert-bearing sandstones, conglomerates, carbonaceous mudrocks, blocky mudrocks, and skeletal limestones were deposited by perennial to intermittent alluvial systems. Carbonaceous mudrocks contain abundant wood fragments, cuticle and cortical debris, and other vascular plant remains representing deposition in oxbow lakes, abandoned channels, and on floodplains under humid to seasonal conditions. Intraformational conglomerates, sandstones, bioturbated and blocky mudrocks with caliche nodules, and bioturbated limestones characterize deposition in intermittent to ephemeral alluvial systems. Bioturbated limestones are encased in bioturbated mudrocks with abundant pseudo-slickensides. The presence of caliche nodules in some of the blocky to bioturbated mudrocks is consistent with supersaturation and precipitation of calcium carbonate from groundwater under semi-arid conditions. Caliche nodules, pseudo-slickensides, and carbonate-rich floodplain sediments are interpreted to have been deposited by intermittent to ephemeral alluvial systems under seasonal to semi-arid climatic conditions. Laminated mudrocks, siltstones, vuggy carbonates, bedded to nodular evaporites, pebbly mudrocks, and diamictites were deposited in evaporative alkaline lakes or playas. Pebbly mudrocks and diamictites are interpreted to represent deposition from channelized and unchannelized hyperconcentrated flows on a playa, resulting from intense rain events within the basin.The areal abundance and distribution of these depositional systems change systematically across the overfilled portion of the Early Cretaceous Cordilleran foreland basin in Wyoming. The lower part (A-interval) of the Cloverly and Lakota Formations is characterized by deposits of perennial to intermittent rivers that existed 300 to 1000 km east of the Sevier fold-and-thrust belt. Proximal to the Sevier fold-and-thrust belt, the A-interval of the Cloverly Formation and upper Ephraim Formation of the Gannett Group are typified by deposits of intermittent to ephemeral rivers and their associated floodplains. In the middle part (B-interval) of the Cloverly Formation, intermittent to ephemeral alluvial systems expand to 600 km into the basin. The upper part (C-interval) of the Cloverly Formation is characterized by playa deposits in the Bighorn and Wind River Basins and intermittent to ephemeral alluvial deposits along the front of the ancestral Sevier Mountains. Deposits of perennial to intermittent alluvial systems in the C-interval of the Cloverly and Lakota Formations are restricted to the Black Hills region, almost 900 km to the east of the Sevier Mountains. The change in the areal distribution of depositional systems through time within this continental foreland basin may be attributed to the development of a rain shadow associated with the uplift of the Sevier Mountains in the Early Cretaceous.