Hydrochemical Monitoring and Heavy Metal Contaminations at the Narim Mine Creek in the Sulcheon District, Republic of Korea

The Narim gold mine is located approximately 200km southeast of Seoul within the Sulcheon mineralised district in the Yeongnam massif, Korea. In this study, environmental geochemical analyses were undertaken for soil, sediment and water samples collected in April, September and November in 1998 from the Narim mine creek. The mine area consists mainly of granitic gneiss; however, mineral constituents of soil and sediment near the mine were mainly composed of quartz, feldspar, mica, amphibole, some pyrite and clay minerals. Also were found some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite, various hydroxide and unidentified secondary minerals. Generally, high concentrations of heavy metals in the soil and sediment are correlated with a high proportion of secondary minerals. Hydrochemical compositions of water samples are characterised by relative significant enrichment of Na⁺+K⁺ and alkali metals in the ground water, whereas the surface and mine waters are relatively enriched in Ca²⁺+Mg²⁺ and heavy metals. Anion contents of the ground waters are typically enriched in HCO₃ ^–, NO₃ ^– and Cl^–, whereas the surface and mine waters are highly enriched in HCO₃ ^– and SO₄ ^2–. The pH and EC values of the surface water from the non-mine creek are relatively lower compared with those of the surface water around the mine and waste dump. The range of D and ¹⁸O values (d parameters) of the water samples are shown in distinct two groups for the April waters of 10.1–13.1, and for the November waters of 5.8–7.9, respectively. This range variation indicates that two group water were composed of distinct waters because of seasonal difference. Geochemical modelling showed that mostly heavy toxic metals may exist largely in the form of free metal (M²⁺) and metal-sulphate (MSO₄ ^2–), and SO₄ ^2– concentration influenced the speciation of heavy metals in the mine water. These metals in the ground water could be formed of CO₃ ^– and OH^– complex ions. Using a computer program, saturation indices of albite, calcite, dolomite in mostly surface water show undersaturated and progressively evolved toward the saturation state, however, ground and mine waters are nearly saturated. The gibbsite, kaolinite and smectite are supersaturated in the surface and ground water, respectively. Calculated water-mineral reaction and stabilities suggest that the weathering of silicate minerals may be stable kaolinite. The clay minerals of K-illite and Na-smectite will be transformed to more stable kaolinite owing to the continuous reaction.     

Geochemical Characteristics of the Acid Mine Drainage in the Water System in the Vicinity of the Dogye Coal Mine in Korea

This study investigated geochemical characteristics of the acid mine drainage (AMD) discharged from the abandoned mine adits in the vicinity of the Dogye coal mine in Korea. Acid mine drainage discharged from Jeoncha pit adit of the Dogye coal mine, which is the main source of the AMD in the study area, had a pH value of 3.0 and concentrations of 2148mg SO₄ ^2– L^–1, 229mg Fe L^–1, 71mg A1 L^–1 and 11mg Mn L^–1. The reduction of some metal concentrations downstream from the discharge point could be explained on the basis of dilution and precipitation. The order of removal of metal ions downstream from the discharge point was Fe>A1, Cu>Zn, Mn. Acidity could be used as a good determining factor offering comprehensive and quantitative values for the polluting extent of acid mine drainage. The acidities existing in all acidic water samples in the Gunahan district originated primarily from mineral acidity, especially in the upper Nahan Creek from dissolved Fe and Al and in the middle and down Nahan Creek from dissolved Al. From the application of the WATEQ4F program, it was determined that predominant species of dissolved Fe in all water samples was Fe²⁺, and those of dissolved Al were AlSO₄ ⁺ and Al³⁺ except for IW2 sample which was associated with white precipitates. The species of dissolved Al in IW2 sample include also AlOH²⁺ and Al(OH)₂ ⁺. The saturation indices of goethite and haematite were positive in the water samples associated with ochrous precipitates (usually called Yellow Boy), therefore these solids might be precipitated. For the IW2 sample, the saturation indices of amorphous Al(OH)₃ and gibbsite were positive, so theoretically these solids might also be precipitated. By XRD analysis, it was found that goethite occurs in ochrous precipitates, and gibbsite in white precipitates.     

Environmental Geochemistry of Soils and Waters of Susaki Area, Korinthos, Greece

Soil and water samples were collected from the Susaki area of Korinthos and analysed for heavy metals in order to evaluate their environmental impact. The geology of the studied area includes ultrabasic rocks and Neogene and Quaternary deposits whereas magnesite veins are found within the ultrabasic rocks. In the north part of the studied area post volcanic emissions of H₂S, CO₂ and H₂O vapor continue to the present day. All the samples were analysed for heavy metals by the ICP method. The element ranges (in g g^–1) for soil samples are: Cu 11–63, Pb 5–256, Zn 21–604, Ni 183–2665, Co 12–124, Mn 456–1434, As 5–104, Sr 44–730, V 21–84, Cr 163–2346, Ba 48–218, Zr 3–41, Y 3–13. The metals Pb, Zn, Ni, Co, Cr, Fe, Cu, Mn, As and Sr are enriched in the Susaki soils. The element ranges for water samples are: Cu 65–103ppb, Pb<10ppb, Zn<5ppb, Ni 21–163ppb, Co 2–12ppb, As<30ppb, Cr<20ppb, Ba 36–785ppb, Sb<10ppb, W<10ppb, Bi<30ppb, Mn 0.0–0.9 g g^–1, Fe 0.01–0.22 g g^–1, Na 843–3076 g g^–1, K 98–278 g g^–1, Si 39–65 g g^–1, P 0.1–0.2 g g^–1. There is a natural pollution of soils with elevated concentrations of Ni, Co, Mn, Fe and Cr due to the presence of ultrabasic rocks. Another natural case of As pollution of soils is due to the volcanic activity and the geothermal field in the area. The geochemical data of ground waters and also the ¹⁸, D data showed a mixing in different proportions between sea water and meteoric water.     

Wet deposition chemistry studies at Suva, Fiji, a remote tropical island site in the south Pacific

A field project encompassing wet-only rainwater sampling was initiated as a bilateral Fiji/Australia activity. Normally, biweekly samples were collected, using a wet-only rainwater sampler, and analysed for H⁺, Na⁺, K⁺, Mg²⁺, NH₄ ⁺, Cl^–, NO₃ ^–, SO₄ ^2–, PO₄ ^3-, methane sulphonic acid, oxalic acid, formic acid and acetic acid. The pH of the rainwater ranged between 5.730 and 4.480 with an average value of 5.176, slightly lower than the pH of unpolluted rainwater saturated with atmospheric CO₂(pH = 5.650). Na⁺and Cl^–were the major ions with average concentrations of 98.15 M and 109.57 M respectively. There is an excellent correlation between the cation sum (average 147.71 eq L^-1) and the anion sum (average 142.12 eq L^-1) attesting to the quality of the data generated. This paper presents the detailed results of the study for a relatively clean remote island site in Suva, Fiji, latitude 18° 09 S, longitude 178° 27 E, height 6 m, and outlines prospects for further work.     

Effect of ammonia on survival and osmoregulation in different life stages of the lobsterHomarus americanus

Acute toxicity of ammonia was determined for cultured larval, postlarval, and wild adult lobsters (Homarus americanus) in 1988. Ammonia tolerance was found to increase with ontogenetic development. Based on 96-h LC₅₀ values of 58 mg l^–1 NH₄ ⁺ + NH₃ l^–1 seawater (0.72 mg NH₃ l^–1) for Stage I larvae, 87 mg NH₄ ⁺ + NH₃ l^–1 (1.7 mg NH₃ l^–1) for Stage II larvae, 125 mg NH₄ ⁺ + NH₃ l^–1 (2.13 mg NH₃) for Stage III larvae, 144 mg NH₄ ⁺ + NH₃ l^–1 (2.36 mg NH₃ l^–1) for Stage IV postlarvae, 377 mg NH₄ ⁺ + NH₃ l^–1 (5.12 mg NH₃ l^–1) for adult lobsters at 5°C and 219 mg NH₄ ⁺ + NH₃ l^–1 (3.25 mg NH₃ l^–1) for adult lobsters at 20°C, recommendations for safe levels of total ammonia and un-ionized ammonia were calculated using an application factor of 0.1. Effects of ammonia on osmoregulatory capacity were studied on postlarvae and adults. Ability of postlarvae and adults to hyper-regulate in low-salinity media decreased after exposure to ammonia. In postlarval lobsters, osmoregulatory capacity was significantly affected in ammonia concentrations exceeding 32 mg l^–1. Osmoregulatory capacity in adult lobsters (5 and 20°C) was affected at 150 mg l^–1. In postlarval lobsters, a minimum exposure time of 12 h was required to impair osmoregulatory capacity. The decrease in hemolymph osmotic pressure was caused by lower hemolymph sodium concentrations. The presence of ammonia in the external medium could markedly affect the Na⁺/NH₄ ⁺ transport mechanism by permanently, temporarily, or partially impairing the transport sites for sodium.     

Environmental Accumulation of Airborne Fluorides in Romania

The nature and extent of pollution from an aluminium smelter and a fertiliser factory in Romania were studied. These are large industrial complexes, and both types of industry are known to release fluorides into the atmosphere. In grass samples collected from around the aluminium smelter, the maximum fluoride levels were found to be 4023mgkg^–1 and 162mgkg^–1 in unwashed and washed grass samples respectively, and 89mgkg^–1 in soils. For the fertiliser factory, the maximum levels in washed grasses were found to be 207mgkg^–1, and 11mgkg^–1 in the soils. In both locations, these maximum values were obtained in samples collected from within 200m of the factory limits, and compare with regional background levels of less than 10mgkg^–1 for grasses and 2mgkg^–1 for soils. The high fluoride levels of fluoride in the grasses are sufficient to give cause for concern for the effects that these could have on the local population and on grazing animals.     

Effects of ammonia on survival and osmoregulation of various development stages of the shrimp Penaeus japonicus

In Penaeus japonicus, the tolerance to ammonia increased with the development from nauplius to late juvenile. The 48-h LC₅₀ of ammonia in nauplii (III–V), 96-h LC₅₀ in zoeae (I–III), mysis (I–III), post-larvae (PL1) and late juveniles (10.4±1.1 g) were respectively 5.0, 6.1 to 8.1, 9.4 to 10.9, 15.5 and 52.7 mg Nl^-1 (0.5, 0.6 to 0.7, 0.9, 1.3 and 3.1 mg NH₃–Nl^-1). In a chronic experiment (20 d), the LC₅₀ in post-larvae (PL1) was 19.1 (1.4) at 96 h and 16.2 mg Nl^-1 (1.3 mg NH₃–Nl^-1) at 480 h. Osmoregulatory capacity (OC) was calculated as the osmotic gradient between the hemolymph and the external medium at given salinities. The effects of ammonia on OC, Na⁺ and Cl^- regulation and gill Na⁺–K⁺ ATPase activity in late juveniles were examined in fullstrength seawater, SW (1050 mosm kg^-1, 36 S) and in dilute SW (450 mosm kg^-1, 15%.), after 48 or 96 h exposure to various concentrations of ammonia. Ambient ammonia disrupted both hypo- and hyper-osmoregulation; decreased OC resulted from impaired Na⁺ and Cl^- regulation. Gill Na⁺–K⁺ ATPase activity increased in SW and was not affected in dilute SW. The decrease of OC was ammonia-dose-dependent. The threshold ammonia concentrations affecting hypo-OC and hyper-OC were, respectively, 16 (1.3) and 32 mg Nl^-1 (2.3 NH₃–Nl^-1) for a 48 h exposure; these concentrations were lower than the 48-h LC₅₀ value, 65.3 mg Nl^-1 (3.5 NH₃–Nl^-1). The time course of exposure to sublethal ammonia (48 mg Nl^-1) demonstrated that the effect on osmoregulation was time-dependent. This effect was also temporary, and the exposed shrimps recovered control OC values after removal of excessive ambient ammonia. The possibility of using OC as an indicator of physiological condition in osmoregulating crustaceans and the acting mode of ammonia on osmotic and ionic regulation are discussed.     

Evaluation of Public Housing Lead Risk Assessment Data

A unique data set from lead risk assessments performed on 67 public housing developments from across the United States was made available for analyzes. The data set includes results of lead analysis from 5906 dust wipes and from 1222 soil samples. A total of 487 dwelling units in these developments, as well as associated common areas, were sampled, all by the same team of inspectors. The number of dwelling units within a development that were sampled reflected the guidelines then in force, the 1990 Interim HUD Guidelines, rather than those specified in the 1995 Guidelines. Median dust lead loadings for floors, 151gm^–2 (14gft^–2), and window sills, 936gm^–2 (87gft^–2), were much less than former HUD limits of 1076gm^–2 (100gft^–2) and 5380gm^–2 (500gft^–2), respectively and are only about one-third of the recently established limits of 431gm^–2 (40gft^–2) and 2690gm^–2 (250gft^–2). In contrast, the median lead loading for window troughs, 8560gm^–2 (795gft^–2), was almost identical to the HUD clearance limit of 8610gm^–2 (800gft^–2). There was a strong positive correlation between floor and window trough lead loading values for samples from the same dwelling units and those from common areas of the housing developments. Door threshold samples, which may reflect conditions exterior to the dwelling unit, were collected from 53 dwelling units. Median lead loading levels of these samples were more than ten times higher than those in floor samples from the same dwelling units, were about the same as window sill samples and about one-half of levels in window trough samples. Composite sample results, simulated by averaging results from four samples within a dwelling unit, revealed that in order to have the same rate of excedence of standards, the composite standards would have to be reduced, for example, from the single sample value of 1076gm^–2 (100gft^–2) to 527gm^–2 (49gft^–2) for floor samples and from the single sample value of 8610gm^–2 (800gft^–2) to 5160gm^–2 (479gft^–2) for window troughs. For this public housing data set, the portion of the units in developments containing more than 225 units which exceeded the established limit for window samples was the same when using either the full data set or a random one-half of the data set. This suggests that, for this data set, the number of dwelling units sampled was excessive . Thus, the required increase in the number of dwelling units to be sampled specified in the 1995 Guidelines for developments with more than 225 dwelling units, may not have been necessary if this data set is representative of public housing developments in the United States.     

A Preliminary Study on Soil–Gas Radon Geochemistry According to Different Bedrock Geology in Korea

Three study areas of Kwanak campus (Seoul National University), Boeun (Choongbuk) and Gapyung (Kyonggi) were selected and classified according to their bedrock types in order to investigate soil–gas radon concentrations. The mean values of radon concentrations decreased in the order of Gapyung (40BqL^–1) > Kwanak campus (30BqL^–1) > Boeun (22BqL^–1), and decreased in the order of granite gneiss > banded gneiss > granite > black slate–shale > mica schist > shale–limestone > phyllite schist according to bed rock types. Variation in radon emanation with water content in soils and with soil grain size was assessed by the modified Morse (1976) 3min method. Soil–gas radon concentrations increased with increasing water content in the range of less than about 6–16wt.%, but decreased above 6–16wt.%. Radon concentrations also increased with decreasing soil grain size. Radioactivity analysis of radionuclides of ²³⁸U series in some soil samples indicated their possible radioactive disequilibrium between ²²⁶Ra and ²³⁸U due to the differing geochemical behaviour of intermediate radionuclides. Thus, a radioactive isotope geochemical approach should be necessary for soil–gas radon study.     

A Geochemical Survey of Topsoil in the City of Oslo, Norway

The city of Oslo is situated centrally in the Oslo-graben, which is a Permian rift basin consisting of different kinds of volcanic and sedimentary rocks. In the summer of 1998, approximately 300 samples of surface soil (2–3cm) were taken systematically, 1km^–2. The investigated area covers about 500km². Samples were dissolved in 7M HNO₃ and analysed for 29 elements with ICP-AES, mercury with cold-vapour technique (CV-AAS) and arsenic and cadmium with a graphite furnace (GF-AAS). A factor analysis is frequently used to identify relationships among sets of interrelated variables. To describe the covariant relationships among the elements, a factor analysis has been completed. The first factor contains the elements Sc, Fe, Li, Co, Al, Cr, Be, K, Ni, V, Mg, Y, Ba, Zr, Mn and As (listed with decreasing communality). These elements are typical for the minerals in the area and most of these elements have a near normal distribution. Sources for this factor are probably geological. The second factor contains Cd, Hg, P, Zn, Cu, Ba and Pb. They have a log-normal distribution. Road traffic is probably one of the sources contributing to this factor. In Norway studded tyres are used frequently in the winter season which results in large amounts of road dust. Leaded petrol has been a major source for Pb but is not in use any more. Wear and tear of tyres and brakes contribute also to this factor. Other sources contributing to this factor are probably industry, rubbish incineration, crematoria and release of some of these elements from structural material by fire. Factors 3, 4 and 6 with elements such as Ca, Na, La, Ti and Sr probably have geological sources. They are associated with minerals like amphiboles, pyroxenes and feldspars and some of the elements are from sea aerosols. Factor 5 contains Mn, Cd, Zn, As and Pb. Manganese may be derived from many different sources such as rock weathering, windblown dust, agriculture and traffic. Since As and Mn are placed in both factor 1 and 5 they probably have both geological and anthropogenic sources. Concentrations of the elements in the second factor are much higher in the central parts of Oslo, than in the rest of Oslo. The median value of Hg in the centre is 0.48mgkg^–1, which is 8 times higher than that in the rest of the city. Also, the other elements have much higher levels in the centre. The industrial district north-east of the centre also has high values. The distribution of arsenic is regular throughout the whole city, but has a slightly higher level in the centre. Norm values for contaminated land used by the Norwegian authorities are 2mg As kg^–1 and 25mg Cr kg^–1. Of 297 samples, 61% contain more than 25mg Cr kg^–1 and 79% more than 3mg As kg^–1, which is the detection limit of the analysis. These samples will therefore be regarded as contaminated. Factor analysis places these elements in the geological factor. The Norm value of zinc is 150mgkg^–1, and 40% of the samples contain more than this. The Norm value of lead is 150mgkg^–1, and 35% of the samples contain. Road traffic is probably the major source for these elements.     

Evaluation and remediation of organics,nutrients and heavy metals in landfill leachate – a case study in Beijing

Leachate pollution in landfill sites is a major source of environmental concern. This study evaluates organics, nutrients and heavy metals in a landfill site in Beijing, and introduces a method combining coagulation–flocculation with filtration for the advanced treatment of leachate. The results confirm that COD_Cr, TN, NH₄⁺ ? N, TP, Mn and As in leachate treated by an anaeobic–oxic biological method are unable to meet discharge or surface water quality standards. When treated with coagulation–flocculation combined with filtration under optimal conditions (cationic polyacrylamide dosage of 8.0 mg/L; polyaluminium chloride dosage of 350 mg/L; 0.4–0.6 mm ceramsite media in the filtration process), the residual NH₄⁺? N, TN, Mn and As in the leachate meet the maximum allowed values for landfill leachate discharge or surface water quality standards in China; the exceptions are chemical oxygen demand and total phosphorus. Leachate treatment processes could be further strengthened or improved.     

Identification and assessment of water pollution as a consequence of a leachate plume migration from a municipal landfill site (Tucumán,Argentina)

Landfills constitute potential sources of different pollutants that could generate human health and environmental problems. While some landfills currently work under the protection of a bottom liner with leachate collection, it was demonstrated that migration could take place even yet with these cautions. The purpose of this paper is to assess the pollution caused by a leachate plume from a municipal landfill that is affecting both groundwater and surface waters. The research was carried out at Pacará Pintado landfill in northwestern Argentina. Analysis of water samples indicates that leachate is affecting groundwater under the landfill area and an abandoned river channel hydraulically connected. In the center of the landfill area, the plume is anoxic and sulfate, nitrate, iron and manganese reduction zones were identified. Leachate plume presented high concentration of organic matter, Fe, Mn, NH₄ ⁺, Cl^? and Cr reaching an extension of 900 m. The presence of a leachate plume in a landfill site with a single liner system implies that the use of this groundwater pollution control method alone is not enough especially if permeable sediments are present below.     

Environmental Impacts of a Secondary Lead Smelter in Landskrona, Southern Sweden

Scandinavia has one secondary lead smelter that recycles lead from approximately 85% of used car batteries in Scandinavia and which has been active since the 1940s. The smelter, situated in Landskrona, has undergone a comprehensive clean up programme during the last decade, during which time production has doubled, while at the same time discharges of dust and lead to the atmosphere have decreased.Top and depth soil samples were taken on a 0.5km×0.5Km grid throughout the city of Landskrona, which covers an area of approximately 15km². Samples were analysed by ICPAES for a number of elements including Pb, Zn, Cu, Cd, As, Sb and Hg. Road dust samples from selected sites were collected and similarly analysed. Blood samples were taken from 37 volunteer schoolchildren (aged 8–11) from two schools in Landskrona. House dust samples were taken from each child's home. Soil samples were taken from homes which had gardens, public and school play areas. Elevated heavy metal concentrations were found in close proximity to the secondary lead smelter, and this soil enrichment influences the whole of the town, modified to some extent by the prevailing wind. The smelter does not influence the soil lead concentration at distances greater than 3.5km, where the soil reflects the background value for the area.Road dust samples also show decreases in lead concentrations with distance from the smelter. The average level of lead in house dust was considerably lower than that found in Birmingham, UK. Blood lead levels in the child population ranged from 1.5–5.1gdl^–1, with a mean of 3.05gdl^–1, showing a distinct decrease from those measured in 1978–82. No significant difference in blood lead concentrations with distance of the home from the smelter, nor between attenders at the two schools was revealed in the limited number of children studied.     

Nitrate reductase and urease enzyme activity in the marine diatom<Emphasis Type="Italic"> Thalassiosira weissflogii</Emphasis> (Bacillariophyceae): interactions among nitrogen substrates

The dissolved nitrogen pool in aquatic systems is comprised of many different nitrogen forms, both inorganic and organic. Interaction among these nitrogen forms at the level of uptake and enzyme activity is, with the exception of NH₄⁺ and NO₃^–, not completely understood. Nitrate reductase (NR) and urease (UA) activities in the marine diatom Thalassiosira weissflogii (Grunow) Fryxell et Hasle were measured in NO₃^–, NH₄⁺, and urea-sufficient cultures before and after challenge additions of NH₄⁺, NO₃^–, and urea in a factorial design. NR and UA were constitutively expressed during growth on NO₃^–, NH₄⁺, and urea. Growth on NH₄⁺ or urea resulted in NR activities that were <10% of the activity observed in the NO₃^–-grown culture, while growth on NO₃^– resulted in UA values that were ~35% of the activities during growth on either NH₄⁺ or urea. The addition of NH₄⁺ or urea to NO₃^–-grown cultures resulted in an immediate decrease in cellular NO₃^– uptake rate, which was not mirrored by an immediate repression of in vitro NR activity; however, the diel peak in NR was suppressed in these challenge experiments. The addition of NO₃^– or NH₄⁺ to urea-grown cultures resulted in non-significant decreases in the urea uptake rate. UA was not impacted by NO₃^– addition, but NH₄⁺ addition significantly decreased UA throughout the experiment. These studies demonstrate that the uptake and assimilation of NO₃^– and urea may not be subject to the same internal feedback mechanism when challenged with other nitrogen substrates.Communicated by J.P. Grassle, New Brunswick     

Photosynthetic acclimation and biochemical responses ofGelidium sesquipedale cultured in chemostats under different qualities of light

The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to assess the effects of light quality and photon-fluence rate (PFR) on growth, photosynthesis and biochemical composition. Plants under blue and red light (BL and RL) showed higher growth rates than under white light (WL) of the same PFR (40 mol m^–2 s^–1). The light-saturated rate of photosynthesis was higher for algae grown under BL and RL than for algae grown under WL. When algae were transferred to WL of moderate PFR (100 mol m^–2 s^–1), the light-saturated rate of photosynthesis decreased, being higher in previously RL-grown algae than in previously BL- and WL-grown algae. The initial slope of photosynthesis-irradiance (PI) curves () was affected by PFR but not by light quality. Pigment content was little affected by light quality. Light-quality treatments also affected the biochemical composition of the alga; previous exposure to various light treatments activate or repress several metabolical pathways that are fully expressed in the subsequent phase of WL of moderate PFR. Thus, phycobiliproteins and soluble proteins increased for previously BL- and RL-grown algae, whereas insoluble carbohydrate concentration was reduced, indicating a change of the C-partitioning between carbon compounds and organic nitrogen compounds. Inorganic nitrogen metabolism was also affected by light: under WL of moderate PFR, NO₃ ^– was totally depleted from sea water, and maximal values of NO₃ ^– uptake were recorded. In addition, neither NO₂ ^– nor NH₄ ⁺ was released. However, when algae were transferred to a low PFR, there was a drastic reduction of NO₃ ^– uptake under WL, which only partially recovered over time. It was accompanied by the release of NO₂ ^–, but not NH₄ ⁺, to the culture medium. Under BL and RL, however, there was a transient enhancement of NO₃ ^– uptake that was followed by a net release of NO₂ ^– and NH₄ ^–. Growth rates were not correlated with PFR. This could be due to the the dynamics of internal carbon mobilization and accumulation in the algae. When algae were exposed to a moderate PFR of WL, carbon requirements for growth were satisfied by photosynthesis. Thus, there was a net accumulation of carbon in the tissue. In contrast, when algae were exposed to low PFRs of either WL, BL or RL, observed growth rates could not be maintained by photosynthesis and carbon was mobilized.     

The chemistry of aluminum in the environment

There is increased concern over the effects of elevated concentrations of Al in the environment. Unfortunately, studies of the environmental chemistry and toxicity of Al have been limited by our understanding of the processes regulating the aqueous concentration, speciation and bioavailability of this element.Although Al is the most abundant metallic element in the Earth's crust, it is highly insoluble and generally unavailable to participate in biogeochemical reactions. However, under highly acidic or alkaline conditions, or in the presence of complexing ligands, elevated concentrations may be mobilized to the aquatic environment. Ecologically significant concentrations of Al have been reported in surface waters draining acid-sensitive regions that are receiving elevated inputs of acidic deposition. Acid- sensitive watersheds are characterized by limited release of basic cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and/or retention of strong acid anions (SO₄ ^2–, NO₃ ^–, Cl^–). Under these conditions inputs of strong acids are not completely neutralized, but rather acidic water is exported from the terrestrial environment. It has been hypothesized that acidic deposition to acid-sensitive watersheds mobilizes Al within the mineral soil, causing elevated concentrations in soil solutions and surface waters. As a result of mineral phase solubility constraints, concentrations of aqueous Al increase exponentially with decreases in pH below 6.0.Monomeric Al occurs as a series of complexes in the aqueous environment, including aquo, OH^–, F^–, SO₄ ^2–, HCO₃ ^– and organic species. Of these aquo, OH^–, F^– and organic complexes are the most significant in natural waters.Elevated concentrations of Al are ecologically significant because: 1) Al is an important pH buffer in acidic waters, regulating the lower limit of pH values following acidification by strong acids; 2) through adsorption and coagulation reactions, Al may alter the cycling and availability of important elements like phosphorus, organic carbon and certain trace metals; 3) Al may serve as a coagulant facilitating the removal of light attenuating materials, thereby increasing the clarity and decreasing the thermal stability of lakes; and 4) Al is potentially toxic to organisms. Better understanding of the chemistry and speciation of Al is essential to assess these effects.     

Elemental Contamination of Rainwater by Airborne Dust in Tamale Township Area of the Northern Region of Ghana

Rainwater samples were collected from Tamale town in the 1997 and 1998 rainy seasons. During this period road construction in the Tamale area resulted in the generation of suspended dust in the atmosphere. Analysis of the samples for major ions showed elevated levels of Cl^–. Ion ratios with Cl^– (Na⁺/Cl^–, K⁺/Cl^–, Ca²⁺/Cl^–/Cl^– Mg²⁺/Cl^– and SO₄ ^2–/Cl^–) in rainwater samples were higher than the corresponding ratios in seawater. Some samples also showed elevated concentrations of Fe, Mn, Al and Zn, all of which except Zn showed a correlation with the dry periods between rainfall events. Consequently, it was concluded that dust generated from lateritic soils was probably the major cause of the increase in concentration of these metals. Aluminium and Fe concentrations were observed to be higher than the World Health Organization drinking water guide limits.     

Removal of contaminants in leachate from landfill by waste steel scrap and converter slag

This study may be the first investigation to be performed into the potential benefits of recycling industrial waste in controlling contaminants in leachate. Batch reactors were used to evaluate the efficacy of waste steel scrap and converter slag to treat mixed contaminants using mimic leachate solution. The waste steel scrap was prepared through pre-treatment by an acid-washed step, which retained both zero-valent iron site and iron oxide site. Extensive trichloroethene (TCE) removal (95%) occurred by acid-washed steel scrap within 48 h. In addition, dehalogenation (Cl⁻ production) was observed to be above 7.5% of the added TCE on a molar basis for 48 h. The waste steel scrap also removed tetrachloroethylene (PCE) through the dehalogenation process although to a lesser extent than TCE. Heavy metals (Cr, Mn, Cu, Zn, As, Cd, and Pb) were extensively removed by both acid-washed steel scrap and converter slag through the adsorption process. Among salt ions (NH₄⁺, NO₃⁻, and PO₄³⁻), PO₄³⁻ was removed by both waste steel scrap (100% within 8 h) and converter slag (100% within 20 min), whereas NO₃^- and NH₄⁺ were removed by waste steel scrap (100% within 7 days) and converter slag (up to 50% within 4 days) respectively. This work suggests that permeable reactive barriers (PRBs) with waste steel scrap and converter slag might be an effective approach to intercepting mixed contaminants in leachate from landfill.     

The Behaviour of Selenium in Geological Processes

Selenium contents were analyzed from a total of 244 soil samples collected over different rock types at a sampling density of one sample per 4km² around Geita gold mining areas, Northwestern Tanzania. Comparisons using literature survey contents of selenium in geological materials and some implications on the selenium in soils are compiled and discussed. Most selenium occurs as simple selenides in small quantities in low temperature hydrothermal deposits devoid of sulphur. It has been observed that to a large extent selenium content is increased more than most trace elements in the upper parts of the Earth perhaps through extraterrestrial deposition. In deep-seated rocks selenium is associated with sulphur but being volatile selenium and sulphur do not behave according to the crystallochemical law. Due to the higher stability of S⁶⁺, Se⁴⁺ and Se⁰ separate during migration. Thus, selenium is especially found in deep-seated plutonic rocks where large magma bodies cooled slowly and sulphur is available to precipitate sulphides. Selenium, which occurs with sulphides, is inhomogeneously deposited into continental margins. It is increased during magmatic differentiation and is highest in basic rocks. In magmatic and metamorphic conditions, selenium is found in the crystal structures of sulphides while in pneumatolytic and hydrothermal processes, it is relatively enriched into the late differentiates compared to sulphur. In metamorphic rocks selenium is more widely distributed. Selenium content in soils in the investigated area varies from (0.3–0.5gg^–1) in laterite and in black cotton soil 0.4gg^–1. Of all volcanic rocks selenium is highest in volcanogenic rocks especially the basalts. Surface waters are enriched in selenium, which they leach from volcanic materials. Selenium in sediments containing clay and organic matter is elevated but the content decreases with increased metamorphism. Selenium in volcanic areas can be used as a pathfinder in prospecting for volcanogenic ore deposits. S/Se ratios are distinct in different rock types and can thus be used to elucidate the origin of rocks, ores, and sediments.