Urban Soil Pollution Research Articles

Urban soil pollution and the playfields of small children

The chemical composition of urban surface soil in Tromso, northern Norway has been mapped to describe the environmental load of toxic elements in different parts of the city. Surface soil samples were collected from 275 locations throughout the city center and nearby suburban areas. Natural background concentrations were determined in samples of the local bedrock. Surface soil in younger, suburban parts of the city shows low concentrations of heavy metals, reflecting the local geochemistry. The inner and older parts of the city are generally polluted with lead (Pb), zinc (Zn) and tin (Sn). The most important sources of this urban soil pollution are probably city fires, industrial and domestic waste, traffic, and shipyards. In this paper two different approaches have been used. First, as a result of the general mapping, 852 soil and sand samples from kindergartens and playgrounds were analyzed. In this study concentrations of arsenic (As) up to 1800 ppm were found, most likely due to the extensive use of CCA (copper, chromium, arsenic) impregnated wood in sandboxes and other playground equipment. This may represent a significant health risk especially to children having a high oral intake of contaminated sand and soil. Secondly a pattern of tin (Sn) concentrations was found in Tromso city with especially high values near shipyards. Further investigation indicated that this pattern most probably reflected the use of the highly toxic tributyltin (TBr). Thus determination of total Sn in surface soils could be a cost-effective way to localize sources of TBT contamination in the environment.

Characteristics of Metal Element Distribution in Urban Surface Soil and Plants: Observations in Kyoto City Area and Stochastic Analysis

To design a rational management system of urban soil pollution, it is necessary to know first the regional soil pollution characteristics and their governing mechanism. In this study, the X-ray fluorescence (XRF) method was selected for quick monitoring of metal concentrations in many solid samples. Soil and plant samples were collected along two streets and at a sports ground in Kyoto City area, and their metal concentrations were determined by the XRF method. Those metal concentrations in soil and plants were analyzed in a stochastic manner. The results obtained in this study can be summarized as follows: (i) The XRF method is useful for quick monitoring of many solid samples because its simple pre-treatment requirement for concentration determination. The practical quantitative detection limits are determined (e.g., 0.010mg g−1 for Zn). (ii) Metal concentrations in surface soils along two streets in Kyoto City showed that the soil contamination was heavier in the central part of the city. (iii) Some metal concentration correlation with sampling distance showed a distance dependent decrease of correlation coefficient, but other metals did not, which suggested random distribution in surface soil of the surveyed area. (iv) Most metal concentrations in grasses had a negative correlation with some element concentration in soil, and some metal concentration in grasses was larger than in soil. These facts indicate that grasses might be used for remediation of polluted soil.

Predicting the Gas Diffusion Coefficient in Undisturbed Soil from Soil Water Characteristics

The gas diffusion coefficient in soil (DP), and its dependency on soil physical characteristics, governs the diffusive transport of oxygen, greenhouse gases, fumigants, and volatile organic pollutants in agricultural, forest, and urban soils. Accurate models for predicting DP as a function of air‐filled porosity (ϵ) in natural, undisturbed soil are needed for realistic gas transport and fate simulations. Using data from 126 undisturbed soil layers, we obtained a high correlation (r2 = 0.97) for a simple, nonlinear expression describing DP at −100 cm H2O of soil water potential (DP,100) as a function of the corresponding air‐filled porosity (ϵ100), equal to the volume of soil pores with an equivalent pore diameter >30 μm. A new DP(ϵ) model was developed by combining the DP,100(ϵ100) expression with the Burdine relative hydraulic conductivity model, the latter modified to predict relative gas diffusivity in unsaturated soil. The DP,100 and Burdine terms in the DP(ϵ) model are both related to the soil water characteristic (SWC) curve and, thus, the actual pore‐size distribution within the water content range considered. The DP(ϵ) model requires knowledge of the soil's air‐filled and total porosities and a minimum of two points on the SWC curve, including a measurement at −100 cm H2O. When tested against independent gas diffusivity data for 21 differently textured and undisturbed soils, the SWC‐dependent DP(ϵ) model accurately predicted measured data and gave a reduction in root mean square error of prediction between 58 and 83% compared to the classical, soil type‐independent Penman and Millington‐Quirk models. To further test the new DP(ϵ) model, gas diffusivity and SWC measurements on undisturbed soil cores from three 0.4‐m soil horizons (sandy clay loam, sandy loam, and loamy sand) within the 4 to 7 m depth below an industrially polluted soil site were carried out. For these deep subsurface soils the SWC‐dependent model best predicted the measured gas diffusivities.

Exposure scenarios and guidance values for urban soil pollutants.

In general, risk assessments of urban soil pollution are prepared by comparing the levels of pollutants with soil quality criteria. However, large urban areas are contaminated with concentrations of pollutants far exceeding the existing soil quality criteria and would consequently be considered to be of potential risk to humans. This is, however, a rather rigid approach, and for risk management purposes it would be desirable to have more than just one level of soil quality criteria. Therefore, a generic risk assessment model was developed for five different use scenarios: child-care centers, kitchen gardens, ornamental gardens, parks, and sports grounds. In each of the scenarios, three different types of expected behavior are described for children and adults, respectively, resulting in different levels of exposure to the pollutants. For risk management purposes, various guidance values can then be derived for each use scenario. Below a lower guidance value, a free use of the area according to the defined use is possible without an unacceptable risk to the public. Above an upper value, a cutoff of the exposure is necessary. In between, the use may be regulated by different types of advice. The model is still preliminary but was, however, used for derivation of guidance values for five commonly found soil pollutants, of which the results for benzo[a]pyrene and lead are presented.

A preliminary study on the effect of Cu, Pb and Zn contamination of soils on community structure and certain life-history traits of oribatids from urban areas

The effect of pollution of urban soils by traffic exhausts on oribatid mites was studied along a traffic gradient of the city of Thessaloniki. Although the population density of the main orbatid species appeared increased in polluted areas, the total orbatid numbers were reduced due to the reduction in species richness. The highest species diversity was recorded in moderately polluted areas. The morphometric characteristics as well as certain life-history traits did no correlate with the level of traffic influence. Nevertheless, these characteristics were considered important for the understanding of the pollution impact on life in soils. Moderate body size, sexual reproduction, increased reproductive effort and wide habitat preferences characterize species in urban sites. Scheloribates latipes and Tectocepheus sarekensis can be used as bioindicators for Pb and Zn pollution of soils, respectively.

Urban soil contamination in Australia

The current knowledge of the pollution of Australian urban soils was reviewed with special reference to heavy metals. Increased community concern in recent years has resulted m a major upsurge in the investigation and rehabilitation of contaminated soils. This has led to a concomitant reassessment and development of regulatory procedures, and the establishment of some new environmental agencies. This review considers sources and extent of contamination, and approaches to the establishment of reference background levels in urban and rural areas. Assessment of contaminated sites has been largely based on overseas experience but site specific approaches relevant to Australian soils and climates are needed and are being developed by State authorities in collaboration with the Australian and New Zealand Environmental and Conservation Council and the National Health and Medical Research Council. The need for soil-based research and for standardized soil sampling procedures for site evaluation and action is stressed. Many opportunities exist for soil scientists in solving problems of soil contamination and rehabilitation.