Controls on the nature and distribution of an alga in coal mine-waste environments and its potential impact on water quality

 A dominant non-bacterial microorganism that may strongly impact environmental conditions in acid mine drainage at several Indiana coal mine sites is a single-celled protozoan, Euglena mutabilis. Field data suggest E. mutabilis has high tolerance for elevated total dissolved solids (TDS), to 18 g/l, and acid conditions to pH 1.7. Distribution is restricted to unmixed effluent pH<4.6, with prolific growth between pH 3.0 and 3.5. Additional factors influencing E. mutabilis include preference for areas with lower mineral/colloidal precipitation rates and a stable substrate of iron-rich precipitates. Initial studies indicate that in areas of prolific growth it contributes to oversaturation of dissolved oxygen by up to 200%. The presence of small orange intracellular crystalline-like structures, similar in color to iron oxyhydroxides, suggests that E. mutabilis may be sequestering iron, and possibly other metals. Further work is needed to determine if E. mutabilis contributes to natural mitigation of poor water quality at these and other coal mine sites. Received: 13 January 2000 · Accepted: 2 May 2000     

Lake and reservoir water quality affected by metals leaching from tropical soils, Bangladesh

 The release of metals during weathering has been studied in order to assess its geochemical controls and possible effects on environmental health in Bangladesh. A total of 27 soil samples and 7 surface water samples were collected from four locations covering three major regions in the country. Results show that weathering effects are a strong function of climatic conditions. Surface waters are typically enriched in Al, Mg, Ca, Na, K, As, Ba, Cr, Cu, Ni, Pb and Zn. The solubility of metal ions, organometallic complexes, co-precipitation or co-existence with the colloidal clay fraction are the main processes that lead to metal enrichment in lake and reservoir water. Aluminium concentrations exceed World Health Organization (WHO) drinking-water standards in all samples, and in two regions, arsenic concentrations also significantly exceed WHO standards. The elevated levels of As indicate that arsenic contamination of water supplies in Bangladesh is not confined to groundwater. Received: 4 June 1999 · Accepted: 17 August 1999     

Water quality assessment in Akpabuyo, Cross River basin, South-Eastern Nigeria

 A baseline study involving analyses of surface and subsurface water samples from the Akpabuyo area was carried out in order to assess their suitability for drinking, domestic and agricultural purposes. Study results show that the waters are acidic (3.41≤pH≤6.28), soft (hardness 2.09–10.68 mg/l as CaCO₃), fresh (conductivity <1400 μs/cm) and characterised by low sodium adsorption ratio, SAR (0.08–0.59). In addition, the mean values of the major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and anions (SO₄ ^2–, Cl^–, HCO₃ ^–) are all within the World Health Organisation (WHO) standards. Taking all this into consideration (except pH), the waters may be regarded as excellent for drinking, domestic and agricultural purposes. On the basis of regression equations, the major cations (K, Na, Ca, Mg) correlate well with conductivity. Finally, results also show that four chemical facies are delineated. These include Ca-Cl, Na-Cl, Ca-SO₄ and Ca-HCO₃. Received: 19 June 1996 / Accepted: 15 April 1997     

Surface water quality evaluation in Odukpani, Calabar Flank, south-eastern Nigeria

 The present article is the second in a series of baseline water quality evaluation studies in parts of south-eastern Nigeria. Study results indicate that the water samples from the study are generally acidic, soft and fresh in addition to low sodium and salinity hazard. Regression equations indicate a good positive correlation between conductivity and Na, Ca, Mg and SO₄. Ca-SO₄ and Ca-Cl constitute the major facies in the area. Generally the waters in the area are good for most domestic and agricultural purposes. Received: 14 April 1997 · Accepted: 3 February 1998     

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     

Environmental considerations in the fertilizer use decision

 The increase in the use of fertilizer in agricultural production has been associated with a substantial increase in agricultural productivity in the United States. This increase in fertilizer use has been driven by a variety of economic forces including variations in the price of output and changing relative factor prices. Associated with the increase in the use of fertilizer have been adverse environmental consequences that are not reflected in the costs and returns of agricultural production. That is, externalities exist whose cost need to be internalized. Because the use of fertilizer has been shown to respond to market forces, it is efficient to use the market to control the use of fertilizer. This can be done through, for example, the use of a fertilizer tax. Received: 31 December 1996 · Accepted: 13 May 1997     

Sediment–water interaction, acidity and other water quality parameters in a subtropical setting, Pimpama River, southeast Queensland

 The geological setting and landuse activities of the Pimpama River catchment are typical for many drainage systems in southeast Queensland. The river originates in coastal ranges of Late Paleozoic age, crosses a floodplain developed during the Late Pleistocene-Holocene sea-level fluctuations and flows into the southern part of the Moreton Bay. The formation of sedimentary pyrite associated with the mid-Holocene transgression is an important feature of this coastal setting. The oxidation and hydrolysis of pyrite and the consequent production of sulfuric acid are controlled by the amount and seasonality of rainfall and influenced locally by landuse activities. The acid production and the leaching of dissolved metals from river alluvium and estuarine sediments impact substantially on land and aquatic habitats. The water quality of the Pimpama River and its tributaries reflects the lithology of the bedrock and can vary largely depending on season, tidal regimes, sediment lithology, local topography and agricultural activities. Monitoring of river water for several seasons revealed four types of events, each with a different response in terms of water quality: (a) occasional showers during the dry season cause low pH and high amounts of dissolved metals in the water, (b) the first heavy rain of the wet season can produce very toxic conditions (low pH and high concentrations of metals) that can result in a fish kill, (c) towards the end of the wet season, prolonged flushing of pyrite oxidation products leads to short-term recovery of the aquatic system (neutral pH and lower amounts of dissolved metals in the water) and (d) a flood event can produce low pH, salinity and high concentrations of metals, which can represent lethal conditions for aquatic life. Assessment of saturation indexes for representative weathering and oxidation products such as clays, goethite, gibbsite and jarosite shows that these mineral phases can precipitate only when the water reaches neutral pH. Received: 21 September 1998 · Accepted: 1 December 1998     

Influence of arsenic-bearing gold deposits on water quality in Zloty Stok mining area (SW Poland)

 The Sudety Mountains contain polymetallic deposits which have been exploited since the Middle Ages. Distinct concentrations of As, Hg, F, Cr in surface water near Zloty Stok suggested that groundwater in the area could also contain elevated metal concentrations. Water samples from 15 locations including Zloty Stream, mine adit discharges, and selected springs generally show low levels of dissolved components and near-neutral pH. However, arsenic concentrations range from 0.99 mg/l to 26.16 mg/l at all 15 sample locations. Mercury concentrations were locally as high as 0.011 mg/l. These high arsenic and mercury concentrations significantly exceed water quality standards and raise concerns for using Zloty Stream for potable water. Recieved: 21 December 1998 · Accepted: 8 June 1999     

Do tides affect water quality in the upper phreatic zone of a small oceanic island, Sipadan Island, Malaysia?

 Sipadan Island is a small oceanic island with limited storage of fresh groundwater. A study was carried out to determine the effect of tidal change on the groundwater quality of such an island using temperature, dissolved oxygen content, conductivity, salinity, and pH values as indicators. Overall, the results indicated that the groundwater quality changes with tides, but the trends of fluctuation differs between the observed parameters. It was found that the percentages of changes during the period of study were 0.8% (temperature), 53% (dissolved oxygen), 61% (conductivity), 58% (salinity), and 1.7% (pH) at the centre of the island; and 0.9% (temperature), 33% (dissolved oxygen), 40% (conductivity), 42% (salinity), and 9% (pH) at a station 120 m from the coast, based on 2.9-m and 2.8-m tidal ranges at each station. Received: 5 July 1995 · Accepted: 6 November 1995     

Conceptual model of the evolution of groundwater quality at the wet zone in Sri Lanka

 The evolution of groundwater quality at a wet zone in Sri Lanka was made clear using field investigation, chemical and isotopic analyses methods. In the wet zone, the concentrations of major ions and electrical conductivity (EC) in the groundwater are low with small seasonal change. Except for sodium, silica and chloride, the EC and other major ion concentrations increase along the groundwater flow direction. The contributions of bicarbonate and calcium ions to the increase in EC are the largest among the major ions. The groundwater quality shows calcium-bicarbonate type, the initial stage of the Chebotarev series. There is a seasonal change in isotopic composition. The isotopically lighter groundwater was found at the valley bottom in the rainy season. Under the very heavy precipitation conditions, the slope of the regression line between δD and δ¹⁸O and deuterium excess for groundwater are close to 8 and 10, respectively. In other cases, the slopes of the regression lines and deuterium excess are, less than 8 and 10, respectively. Received: 5 August 1998 · Accepted: 19 October 1998     

Hydrogeological studies on the mechanical behavior of landfill gases and leachate of the Nanjido Landfill in Seoul, Korea

 The Nanjido Landfill is the largest uncontrolled landfill in Korea and it causes various kinds of environmental problems. Landfill gases and leachate are recognized as the most serious environmental problems associated with the landfill. This study employs a series of numerical models and uses test data to interpret the distribution and flow of landfill gases and leachate. Leachate seepage appears about 40–60 m higher than the estimated basal groundwater table. Thus, seepage data indicate that perched or floating leachate layers are formed in the unsaturated zone of the landfill. The leachate production rate is estimated using infiltration test data and a model for unsaturated groundwater flow. Geochemical data indicate that the landfill leachate degrades the basal groundwater quality along the downgradient zone. The environmental impact of the leachate on river water is estimated. Received: 17 June 1996 · Accepted: 2 October 1996     

Environmental impact of geothermal fluids on surface water, groundwater and streambed sediments in the Akarcay Basin, Turkey

In this study, the impact of geothermal water on ground and surface waters has been investigated in Akarcay Basin, Turkey. The release of thermal return water from district heating in the city of Afyon and from thermal baths has a considerable environmental impact on the main stream. Historical analyses of stream water quality data show that the present pollution is associated primarily with thermal return water of district heating system. Currently, about 6% of stream water comprises of thermal water. The pollution seems to degrade the water quality in Lake Eber. Streambed sediments were found to be in equilibrium with polluted water and may lead to additional pollution in lake water. Thermal groundwater intrusion to fresh water production wells was detected mainly at sites close to geothermal fields. Solutions to remove thermal water from surface environment are suggested.     

Water quality and sediment geochemistry in lakes of Yunnan Province, southern China

 Yungui Plateau lakes in southwestern China are economically important, although few have been studied previously. Water and sediments of 24 lakes throughout Yunnan Province were sampled in October 1994. We describe the chemical and physical characteristics of Yunnan lakes, and address effects of regional geology and human influences on water quality and sediment type. Water quality differs between deep Yunnan lakes of tectonic origin and shallow solution basins. Shallow lakes generally have higher nutrient concentrations and appear to be more susceptible to riparian disturbance than deeper lakes. Shallow lakes with high macrophyte standing crops, nevertheless, exhibit nutrient-poor waters. Principal ions Ca²⁺, Mg²⁺, and HCO₃ ^– reflect regional carbonate geology, except in Cheng Hai, which is a sodium bicarbonate lake. Specific conductance and δ¹⁸O are positively correlated, indicating that evaporation concentrates both solutes and ¹⁸O. Large, shallow lakes in southeastern Yunnan exhibit ¹⁸O-enriched waters because of substantial evaporation, whereas small, deep lakes are ¹⁸O-depleted. Lake waters are ¹⁸O-depleted in small, shallow basins that receive substantial rainwater input relative to their small volumes. ¹⁸O enrichment in Cheng Hai suggests that a recent 5-m water-level decline in this lake was caused by increased evaporation or diversion of freshwater inflow. Yunnan watersheds have undergone substantial deforestation, agricultural cultivation, soil erosion, and industrialization. Limnetic nutrient concentrations indicate that human activities have affected water quality. Organic matter content is low in sediments because of increased non-carbonate, clastic sediment yield from watersheds. Environmental policies are needed to balance ecological contraints with economic activities that impact water quality. Received: 1 July 1996 / Accepted: 2 October 1996     

Karst water control and management in the Hanxing mining area of North China

 The Hanxing mining area of North China includes three coalfields: Fengfeng, Handan and Xingtai. Six or seven coal seams can be commercially mined in Permo-Carboniferous strata, among which the lower three, accounting for 37% of the total reserves, are threatened with karst water from the underlain Ordovician limestone. Hundreds of water inrush accidents have occurred and over 30 mines have been flooded, resulting in heavy economic losses and casualties. In order to avoid water inrushes and keep the mines safely operational, dewatering in the karst aquifer was considered an essential measure. Unfortunately, this practice has caused serious environmental problems such as surface subsidence (sinkhole), dry spring, and water supply shortage. On the basis of a series of investigations and tests in the last 20 years, an alternative method, mining with water pressure, has been proposed and is the main focus of this paper. By using this method, the karst water in the limestone can be preserved to some extent and the coals can be mined in a relatively safe way. Received: 22 March 1996 · Accepted: 8 April 1996     

The impact of human activities in the Malia coastal area (Crete) on groundwater quality

The evaluation of the long-term effects of seawater intrusion into the aquifers due to negative water balance and nitrate pollution of drinking-water quality due to human activities requires detailed knowledge of both the transport of the chemical constituents and the geochemical processes within aquifers. Hydrogeological and hydrochemical studies in the unconfined aquifer of Malia have provided the necessary data to define the areas at increased risk from these phenomena. The solution of the second Fick's low under given boundary conditions gave an estimate of the propagation of groundwater pollution by NO₃ ^–. Additionally, in order to simulate the ion concentration changes during a period, for example a period of positive water balance or refreshening, groundwater transport and cation exchange reactions were modelled using the code PHREEQM. Received: 25 July 1997 · Accepted: 4 November 1997     

Geochemical factors controlling the chemical nature of water and sediments in the Gomti River, India

 R-mode factor analysis of the recently acquired data on water and sediment chemistry has been performed. Basic chemical parameters have been merged together which aid in interpreting a few empirical geochemical factors controlling the chemical nature of water and sediments of the Gomti River, a major Himalayan tributary of the Ganges drainage basin. Water chemistry seems to be controlled by three factors: bicarbonate, rainfall and silicate and phosphate factors. Sediment chemistry is largely controlled by the following four factors: clay, adsorption/desorption, Fe-Mn hydroxide and mercury factors. These factors show spatial and temporal variability in terms of their R-scores. Received: 8 September 1997 · Accepted: 15 December 1997     

Catastrophic and dangerous inflows to salt mines in Poland as related to the origin of water determined by isotope methods

 Tritium, ¹⁴C, δ¹³C, δ¹⁸O and δD measurements indicated as early as 1973 the existence of inflows of modern meteoric water to the Wapno salt mine in a Zechstein diapir. In spite of these early warnings, the continuation of improper exploitation led, in 1977, to sudden flooding of the mine followed by catastrophic land subsidence. The lesson learned from that catastrophe, as well as the results of isotope investigations performed in the Inowrocław salt mine, led to the decision to flood the mine artificially in order to avoid a similar land subsidence. The Kłodawa mine was not regarded to be in danger of flooding due to a thick clay cap. In fact, a large number of usually short-lasting water occurrences had the isotopic composition characteristic for evaporated ocean water. However, since 1956 an inflow has existed with δ¹⁸O and δD values close to that of pre-Quaternary saline waters and brines in the Mesozoic formations adjacent to the diapir. Two other inflows have recently occurred with the initial δ¹⁸O and δD values of modern waters. As a consequence, the mine is regarded to be in danger, and the exploitation of salt in the areas of inflows has been stopped. The Wieliczka mine, southern Poland, exploits Miocene salts overthrusted together with the Carpathian flysch from the south. The most dangerous and catastrophic inflows were caused by human errors. Isotope data show the water to be of glacial or Holocene age stored in Tertiary, slightly cemented rocks of low permeability, which neighbor the mine from the north. Owing to specific geology, the mine has survived for a long time, in spite of relatively large and long-lasting inflows. However, its existence is in permanent danger. Received: 7 March 1997 · Accepted: 17 November 1998     

Origin and distribution of saline groundwaters in the upper Miocene aquifer system, coastal Rhodope area, northeastern Greece

 This paper describes the origins and distribution of saline groundwaters in the coastal area of Rhodope, Greece. The aquifer system includes two aquifers within coarse-grained alluvial sediments in the coastal part of the study area. Two major water-quality groups occur in the study area, namely Ca²⁺-rich saline groundwater and Ca²⁺-poor, almost fresh groundwater. The main process controlling the groundwater chemistry is the exchange of calcium and sodium between the aquifer matrix and intruding seawater. The natural salt water in the study area is probably residual water that infiltrated the aquifer system during repeated marine transgressions in late Pleistocene time. Seawater intrusion into the coastal aquifer system occurs as a result of overpumping in two seawater wedges separated vertically by a low-permeability layer. The rate of intrusion averages 0.8 m/d and is less than expected due to a decline of the aquifer's permeability at the interface with the seawater. The application of several hydrochemical techniques (Piper and Durov diagrams; Na⁺/Cl^–, Ca²⁺/Cl^–, Mg²⁺/Cl^–, and Br^–/Cl^– molar ratios; Ca²⁺/Mg²⁺ weight ratio; and chloride concentrations), combined with field observations, may lead to a better explanation of the origin of the saline groundwater. Received, May 1997 / Revised, May 1998, December 1998 / Accepted, February 1999     

Effects of geology and human activity on the dynamics of salt-water intrusion in three coastal aquifers in southern Spain

 Mathematical modelling of salt-water intrusion processes in three aquifers on the southern coast of Spain (Río Verde, Río Vélez and Castell de Ferro) reveals that, although all three systems are subject to the same climate and seasonal over-exploitation, geological and human factors have very different effects on the dynamics of contamination. In the Río Verde aquifer, the most important influence is the high volume of extractions occurring during the dry season; in Río Vélez, the intrusion is strongly controlled by infiltration of water from the river to the aquifer, and, in the Castell de Ferro system, an intensely karstified carbonate massif lying in contact with both the sea water and the detrital aquifer represents the main entrance point for influx of sea water and subsequent washing of the aquifer. We have undertaken a mathematical simulation of various possible measures to counteract intrusion, according to the specific characteristics of the process in each aquifer. These measures include artificial recharge, use of natural recharge from the river as a hydraulic barrier, and the construction of a low-permeability barrier. Received: 5 December 1995 · Accepted: 12 April 1996     

The impact of incorrectly estimating factor productivity in agriculture on the environment and human health

 This paper explores the implications of a misspecification of the production function on the use of factor inputs in the context of the adoption of an alternative production practice (a technological innovation) designed to mitigate the impact of agricultural production on human health and the environment. It is demonstrated that if the level of the use of some inputs is considered rather than their consumptive use (i.e., the actual amount used by a plant), the productivity of the input is inaccurately measured. It is also demonstrated that an aggregate production function approach can lead to overestimation of the value of the marginal product of an input due to the frequently implicit assumptions that the output supply, output demand, and fertilizer demand are infinitely price elastic. The implications of the results are important for determining the optimal use of inputs such as fertilizer and pesticides which have known adverse impacts on the environment and human health. Received: 22 November 1996 · Accepted: 4 May 1998