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An investigation of environmental geochemistry of shale rock, soil and water in parts of Abakaliki, southern Benue Trough , Nigeria was carried out in order to evaluate the impact of shale bedrock in the soil and water environment. Shale rock, soil and water samples were collected from ten (10) locations within the study area and were analysed for major and trace elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In situ parameters such as pH, in water were measured in the field. The results show that Pb is highly enriched while As. Cr, Co, Fe, Ni, Sr, V and Zn are slightly enriched in the shales relative to the global shale average. Similar geochemical trend was observed for surface and subsurface soils. Also, the mean concentrations of As, Co. Cu. Mn, Pb and Zn in soils at both depths are higher than the mean concentrations in the shale bedrock in the area of study, implying relative enrichments of these metals in the soils of the study area. In addition, the mean values of Al, Fe, Ti, Cr, Ni, Sr and V in both soil depths are lower than the values recorded in the shale bedrock. Relationship between pH and metal load suggested that the waters are dominantly near neutral to alkaline range suggesting that acidic contaminants do not affect the water quality. The mean concentrations of Al, Fe, Mn and Pb in groundwater and surface water were above the regulatory standards indicating contamination of the water. The calculated enrichment factor, anthropogenic input, pollution index for soil indicated that the soil are highly contaminated through numerous geogenic and anthropogenic sources with Pb being the most toxic metal with the shale bedrock and the mineral load contained in them as the major contributor of these contaminants.

Mining activities have introduced various heavy metals and metalloids to surrounding soil environments, causing adverse impacts to the ecological environment system. The extremely high concentratio...

The chemistry of semiconductor wafer processing liquid waste, contaminated by heavy metals, was investigated to determine arsenic content. Arsenic and gallium concentrations were determined for waste slurries collected from gallium arsenide (GaAs) wafer processing at three industrial sources and compared to slurries prepared under laboratory conditions. The arsenic and gallium content of waste slurries was analyzed using inductively coupled plasma mass-spectrometry (ICP-MS) and it is reported that the arsenic content of the waste streams was related to the wafer thinning process, with slurries from wafer polishing having the highest dissolved arsenic content at over 1,900 mgL(-1). Lapping slurries had much lower dissolved arsenic (< 90 mgL(-1)) content, but higher particulate contents. It is demonstrated that significant percentage of GaAs becomes soluble during wafer lapping. Grinding slurries had the lowest dissolved arsenic content at 15 mgL(-1). All three waste streams are classified as hazardous waste, based on their solids content and dissolved arsenic levels and treatment is required before discharge or disposal. It is calculated that as much as 93% of material is discarded through the entire GaAs device manufacturing process, with limited recycling. Although gallium can be economically recovered from waste slurries, there is little incentive to recover arsenic, which is mostly landfilled. Options for treating GaAs processing waste streams are reviewed and some recommendations made for handling the waste. Therefore, although the quantities of hazardous waste generated are miniscule in comparison to other industries, sustainable manufacturing practices are needed to minimize the environmental impact of GaAs semiconductor device fabrication.

Concurrent 24-hr samples of particulate matter of median aerodynamic diameter less than 10 microm (PM10) were collected over a 10-day period in August 2000 at four sites along a transect in west-central Scotland, UK (passing from the coast through the city of Glasgow) in line with the prevailing southwesterly wind. Each sample was analyzed for chloride (Cl(-)), nitrate (NO3(-)), sulfate (SO4(2-)), ammonium (NH4(+)), calcium (Ca(2+)), iron (Fe), and organic hydrocarbon material (OHM). The contribution from elemental carbon (EC) was estimated. Sampling days were categorized according to local wind direction, synoptic flow, and air mass back trajectories. Chemical mass balance (CMB) reconstruction of the following PM10 components was derived for each wind direction group and at each transect location: ammonium sulfate ((NH4)2SO4), ammonium nitrate (NH4NO3), sodium chloride (NaCl), gypsum (CaSO4), OHM, EC, soil/surface dusts, and particle-bound water. The results showed that PM10 at the coastal site was dominated by the marine background (NaCl) compared with the urban sites, which were dominated by local primary (EC and soil/resuspension) and secondary sources (NH4NO3, (NH4)2SO4, and OHM). There was evidence of Cl(-) depletion as NaCl aerosol passes over urban areas. There was also evidence of long-range transport of primary PM10 (EC and OHM); for example, at the coastal site from transport from Ireland. The work demonstrates how the general approach of combining mass reconstruction along a transect with other information such as wind/air-mass direction generates insight into the sources contributing to PM10 over a more extended spatial scale than at a single receptor.

The mobility and bioavailability of As and Sb in relation to soil-biota transfer were evaluated at a former Sb mining and smelting site (Glendinning, SW Scotland, UK). The study specifically assessed the accumulation of As and Sb in different environmental components (soil, plants and earthworms) across mining area to estimate risk factors for the biota. Total concentrations and fractions of As and Sb in soils were determined. The latter using both a single solute and a non-specific stepwise sequential extraction (CISED) method. Mineralogical information was gathered from XRD and SEM analysis used to identify element distribution patterns. Pseudo-total (aqua-regia) levels of As and Sb in the soils varied between 50-17,400 mg kg(-1) and 10-1,200 mg kg(-1), respectively. Both elements are predominantly associated with Fe (or Al) oxides/hydroxides, by adsorption around silicate grains, representing a potentially bioavailable fraction. Antimony was also associated with sulphide phases. The highest values of As and Sb in biota were recorded in the earthworms (960 mg kg(-1) and 27 mg kg(-1), respectively). Bioconcentration factors for both elements were below 1 and the highest for earthworms. Total and leached As levels in soils and biota were positively and significantly correlated, but only for Sb in earthworms and grass. Bioavailability of As in the biota, was shown to be limited by pH. In spite of the considerably high As and Sb contents of the soil the plant contamination remained comparably low, but still exceeded background values.

A pilot study of production of respirable and inhalable dusts from sawing and sanding medium density fibreboard (MDF) and softwood in a typical cabinet-making workshop produced high but variable exposure levels at the bench and operator position. Exposure levels for the total inhalable fraction (approximately