P. R. Simpson

Urban Geochemistry: A study of the influence of anthropogenic activity on the heavy metal content of soils in traditionally industrial and non-industrial areas of Britain

Abstract Heavy metal concentrations have been determined in topsoils (0–15cm) in the London Borough of Richmond-upon-Thames, a non-industrial, mainly residential area of approximately 56 km 2 , and Wolverhampton an industrial city in the West Midlands of 70 km 2 . Soil samples were taken on a grid basis at a density of four per km 2 and analysis for 25 elements was carried out by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Topsoils in Richmond were found to have significantly higher concentrations of heavy metals in developed locations compared to areas of open space, whilst in Wolverhampton topsoils a greater degree of contamination with Zn was found than with Pb. GIS-based mapping techniques used in conjunction with statistical analysis of the data have highlighted the influence of land-use on the heavy metal content of topsoils in these two urban areas. The highest concentrations of Pb in Richmond-upon-Thames (> 1000 μg/g) tend to occur close to major road junctions on roads with high traffic densities. High levels of Pb (approx. 500 μg/g) also occur in the areas where the oldest housing is located (> 100 a). In Wolverhampton the highest concentrations of heavy metals, Zn in particular, are generally located to the east of the city in areas of both historical and contemporary industrial activity.

Platinum concentrations in urban road dust and soil, and in blood and urine in the United Kingdom †

Increasing Pt concentrations from vehicle catalysts have been reported from a number of countries. Analysis of Pt and Pd in soils and road dusts taken from areas of high and low traffic flows in SE England show concentrations of Pt in the range < 0.30-40.1 ng g-1 and Pd in the range < 2.1-57.9 ng g-1. Higher concentrations of Pt are associated with high traffic densities. Samples taken from streets of lower traffic flows were found to contain the lower concentrations of the ranges. Pilot studies of Pt concentrations in blood and urine using ICP-MS have been carried out. Platinum concentrations in whole blood were: precious metal workers, 780-2170, mean 1263 pmol l-1 (0.152-0.423, mean 0.246 microgram l-1); motorway maintenance workers, 645-810, mean 744 pmol l-1 (0.126-0.158, mean 0.145 microgram l-1); Imperial College staff, 590-713, mean 660 pmol l-1 (0.115-0.139, mean 0.129 microgram l-1). Platinum concentrations in urine in pmol Pt per mmol creatinine were: precious metal workers, 122-682, mean 273 [0.21-1.18, mean 0.47 microgram Pt (g creatinine)-1]; motorway maintenance workers, 13-78, mean 33.7 [0.022-0.135, mean 0.058 microgram Pt (g creatinine)-1]; Imperial College staff, 28-130, mean 65.6 [0.048-0.224, mean 0.113 microgram Pt (g creatinine)-1]. Detection limits were 0.03 microgram l-1 for both blood and urine. The possible health effects of increasing Pt in the environment are discussed. Platinum provides an excellent example of the significance of speciation in metal toxicity. Platinum allergy is confined to a small group of charged compounds that contain reactive ligand systems, the most effective of which are chloride ligand systems. Metallic Pt is considered to be biologically inert and non allergenic and since the emitted Pt is probably in the metallic or oxide form, the sensitising potential is probably very low. Platinum from road dusts, however, can be solubilised, and enter waters, sediments, soils and the food chain. There is at present no evidence for any adverse health effects from Pt in the general environment, particularly allergic reactions.

Urban geochemistry: research strategies to assist risk assessment and remediation of brownfield sites in urban areas.

Urban geochemical maps of Wolverhampton and Nottingham, based on multielement analysis of surface soils, have shown distribution patterns of “total” metals concentrations relating to past and present industrial and domestic land use and transport systems. Several methods have been used to estimate the solubility and potential bioavailability of metals, their mineral forms and potential risks to urban population groups. These include sequential chemical extraction, soil pore water extraction and analysis, mineralogical analysis by scanning electron microscopy, source apportionment by lead isotope analysis and the development of models to predict metal uptake by homegrown vegetables to provide an estimate of risk from metal consumption and exposure. The results from these research strategies have been integrated with a geographical information system (GIS) to provide data for future land-use planning.

Changes in platinum concentrations in soils and dusts from UK cities

Vehicle exhaust catalysts have been fitted to all new cars in the UK since January 1993, in order to comply with EU Stage I limits (EC Directive 91/441/EEC) on emissions of carbon monoxide, hydrocarbons and nitrogen oxides (N02 nitrogen dioxide and NO nitric oxide). A typical catalyst contains 1–3 g of platinum group metal, housed in a stainless steel box. Catalysts are designed to operate for at least 80,000 km, and their numbers are increasing worldwide, therefore Pt losses are of general environmental interest. Validated data are needed to determine concentrations in environmental media in order that potential health risks and environmental impacts of this source of Pt may be assessed.

Geochemical mapping of stream water for environmental studies and mineral exploration in the UK

Abstract The stream water hydrogeochemical database, prepared by the British Geological Surveys Geochemical Survey Programme, in conjunction with databases for stream sediments, soil samples and mineral concentrates, has recently been enhanced for a range of economic and environmental objectives. The density of systematic stream water sampling and analysis has been increased to one sample per km 2 and a broader spectrum of determinands introduced. An orientation suite of hydrogeochemical maps has been produced from water samples collected at 1279 sample sites in North Wales to test the methodology. Preliminary results indicate that bedrock geology and mineralisation are the most important variables which influence the surface water chemistry. The primary control by geological parameters is variously modified by secondary influences which include geomorphological factors (especially altitude) atmospheric (climatic and coastal effects), and anthropogenic (agriculture, urban and industrial developments). Regional hydrogeochemical stream water maps have a wide range of economic and environmental applications, especially when interpreted in conjunction with geological data. Results obtained so far indicate that interpretation is likely to be further enhanced in the future by intercomparison with regional stream sediment, hydrogeological, geomorphological, pedological, agricultural, landuse, climatic and remotely sensed datasets in a GIS environment. Hydrogeochemical sampling and analysis represents a cost-effective addition to the Regional Geochemical Survey of the UK.

Regional geochemistry and the identification of metallogenic provinces: examples from lead-zinc-barium, tin-uranium and gold deposits

Abstract Regional geochemical data from the classic mining districts of Southwest England, the Pennine orefields of Central England, and the Dalradian belt of Scotland, with its important occurrences of gold, are considered as a basis for understanding metallogenic provinces. The deposit types are granite-associated Sn-U, Mississippi Valley Type Pb-Zn-Ba-F and vein Au. It is suggested that crustal reservoirs, enriched in ore-forming elements, were important in the genesis of the examples of Sn-U and Au mineralisation studied. The reservoirs comprise evolved subalkaline granites and carbonaceous sulphur-enriched turbidities in listric faulted orogenic basins, respectively. In the case of the Pennine base-metal deposits, the reservoirs from which the ore-forming fluids were derived, comprise sedimentary basins approximating in composition to average shale and ore deposition mainly reflects the nature of basin evolution. The regional geochemical data used in the study were derived from geochemical atlases produced for different purposes and to different standards. Nevertheless, simple trace-element plots normalised, for example, to average crustal abundances can be used together with geological and geophysical criteria to summarise key characteristics of the crustal reservoirs identified and to develop methods suitable for screening spatially related data sets using Image Analysis or Geographical Information Systems.

High resolution regional hydrogeochemical baseline mapping of stream water of Wales, the Welsh borders and West Midlands region

Abstract The stream water hydrogeochemical database, produced by the Geochemical Baseline Survey (GBASE) of the British Geological Survey, has recently been enhanced in the light of experimental pilot studies in North Wales, to meet a wider range of economic and environmental objectives which require modern, integrated and strategic geochemical surveys for their implementation. Hydrogeochemical data are therefore now collected, in conjunction with geochemical data for stream sediments, soil samples and mineral concentrates. The density of sampling, based on the collection of stream water at near-baseflow conditions during the late summer period each year, has been increased to one site per 1.75 km 2 and a broader spectrum of geochemical determinants introduced. Provisional regional datasets are being prepared for an extensive region covering Wales, the Welsh Borders, and part of the West Midlands representing over 17 000 sample sites. Bedrock geology and base metal sulphide mineralisation are particularly well reflected in the stream water chemistry at the regional scale. The influence of secondary factors, such as geomorphology, atmospheric controls, and anthropogenic contamination due to agriculture, urban, industrial and military developments, can also be readily distinguished. The data obtained by systematic high resolution sampling of first and second order streams, vary in concentration over three or four orders of magnitude for many of the analytes studied here. This compares with a range of only one or two orders of magnitude for many of the analytes in stream sediment samples. The extended range in values for stream water is an important factor in the gridding, plotting and production of relatively stable maps. They are relatively unaffected either by short temporal changes in stream water flow, which are attributable either to storm events noted during the sampling campaign, or by annual differences between wet and dry summers in different years. This has enabled a series of robust surface hydrogeochemical maps to be prepared for analytical data collected during the summer sampling campaigns conducted annually from 1989 to 1994. These maps provide a unique source of synoptic baseline information for a wide range of economic and environmental applications especially, when combined with other geoscience datasets in a GIS environment.

Recent increases in platinum metals in the environment from vehicle catalytic converters

Abstract The natural and anthropogenic sources of platinum metals in the environment are reviewed with particular emphasis on platinum from vehicle exhaust catalysts (VECs). Reported increases world-wide in platinum metal concentrations in a number of environmental media over recent time are discussed. Estimations of the emission rates for platinum from petrol (gasoline) powered cars in the literature have been made from both test rig and environmental considerations. Using such emission rates, it is estimated that the total input of Pt from UK traffic during the years 1993–1999 varied between about 250 kg and 120 kg. World-wide, the annual input into the environment is estimated to be between 0·5 × 106 and 1·5 × 106 kg. The health implications of such inputs of platinum metals into the environment are considered. At present, there is no evidence for adverse effects on human health, although the effects of long-term inhalation and ingestion of PGE containing particulates is not known. Potential impacts on the environment, in particular microflora, are also important, since it is known that some PGE compounds have effects on micro-organisms at very low concentrations.

Role of high heat production granites in uranium province formation

A genetic relationship has long been indicated between acid magmatism (granite intrusion, rhyolitic and tuff vulcanicity) and the formation of uranium provinces as a result of the high mean clarke values of uranium in acid igneous rocks (4 ppm)1, 2 and their relative abundance in uranium provinces. Studies of the occurrence and distribution of uranium in granites3–8 and in acid volcanics9 enable further progress to be made in under-standing this association. It has been suggested,6,10 for example, that major uranium provinces can be formed by mass transfer of radioelements entrained in acid magmas characterized by high heat production from subcontinental lithosphere to the upper crust during cratonization following orogenesis. Rapid uplift and displacement along deep faults, hot spring activity and circulating groundwater (as a result of high geothermal gradients characteristic of such tectonic settings) may then redistribute uranium into various types of hydrothermal ore deposits. These may be closely associated with granites and acid volcanics, and epigenetic uraniferous phosphatic hot spring deposits may also occur in diatremes related to basement-controlled faults.

Abstract: Regional geochemical maps for uranium in surface drainage systems in Northern Britain: Environmental and economic implications

Regional geochemical maps for uranium in surface drainage systems in northern Britain: environmental and economic implications P.R. Simpson, 1 W.M. Edmunds, 2 N. Breward, 1 D.Flight, 1 P. Green, 1 T.R. Lister 1 and R.T. Smith I 1 British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG, England 2 British Geological Survey, Wallingford, England Uranium, thorium and potassium are the principal conlributors to natural radioactivity in the environment and occur in varying amounts in terrestrial minerals, rocks, soils and water. Uranium, which has three radioactive isotopes 238U, 235U and 23413 is the subject of this study. Systematic multielement regional geochemical mapping of the UK landmass by the British Geological Survey, which commenced in 1968, has from the outset collected data on the uranium levels of stream waters and sediments at an average density of one sample per 1.5 km 2 and one per km 2 respectively. The data provide a synoptic regional view of naturally occurring uranium levels over an area extending from Shetland to the Scottish Borders. The stream sediment and water samples have been analysed for the most part by the Delayed Neutron Method (DNM) at the HERALD facility, AWRE. Latterly and in the southern portion of the area U analyses were performed by laser-induced fluorescence techniques. U concentrations for sediments report in the range from < 1 ppm >3,000ppm. U concentrations for stream waters report in the range from <0.02ppb >50ppb. The sampling and analytical methods and the data presented have been subjected to comprehensive Quality Assurance and Quality Control procedures from the outset of the programme. The results obtained demonstrate clearly defined patterns in the distribution of U in the surface environment which mainly reflect geology and lithology. Robust patterns are generated in both media which are independent of variations in both rainfall and climate although there are some differences between the patterns indicated by stream sediments and waters. Areas of primary U enrichment which are mainly associated with granitic rocks of Lower Devonian age can be identified on the U (sediment) map. The U (water) map also confirms these locations but additionally outlines mainly Devonian lithologies where levels of U in water are enhanced. The mineralogy of uranium and the prevailing pH and redox conditions exercise an important control on its solubility in mineralising systems and surface waters. U is also more soluble in high alkalinity surface waters with a high calcite saturation index. This is probably responsible for the enhanced U (water) values in areas underlain by Old Red Sandstone rocks to the north and east of Inverness including the Black Isle, to the south of the East Grampian Batholith and in the Southern Uplands to the northwest of the Cheviot Granite, all of which are important agriculturally. The relationship between high levels of U in stream sediments and waters and radon gas and its daughters, which is probably one of the most important potential hazards associated with natural radioactivity, has potential environmental and epidemiological implications.