Search

Purpose: Lead contamination is a prevalent issue affecting cities worldwide. Traditional fieldwork and laboratory analysis techniques can be time-consuming and costly. The purpose of this study was to evaluate the performance of ordinary cokriging (CK) when volume magnetic susceptibility (κ) is used as a co-variable for spatial interpolation of Pb in contaminated urban soils. Materials and methods: The study was conducted in contaminated urban soils of a former unregulated landfill site. A total of 76 surface samples (0–10 cm) were collected using a systematic sampling grid separated by 20-m intervals. Magnetic susceptibility measurements were taken at a higher density of 10-m intervals with 288 measurements. Thus, it was used as an auxiliary variable to predict Pb concentrations by the CK procedure with an aim to improve spatial interpolation of Pb. To determine the effectiveness of CK over the ordinary kriging (OK) procedure, the spatial density of samples was reduced prior to interpolation. A total of ~ 15%, 25%, 35%, and 50% of the Pb samples were randomly selected and reserved for validation. Omnidirectional semivariograms and covariograms were fitted using log-transformed data prior to interpolation. Results and discussion: Measurements of κ shared a significant relationship with Pb concentrations by the Spearman's Rho correlation analysis (rs = 0.676, p < 0.01). The effectiveness of the CK procedure over OK was determined using validation datasets. Statistically, the results showed that lnPb when its auxiliary relations with lnκ were used in CK had overall lower "root mean square error" (RMSE) and predicted lnPb values from the CK procedure had a higher r2 value with measured lnPb than OK. A model produced by the CK procedure with a reduced spatial density of 49 Pb points provided the more accurate map with a RMSE of 0.550 and an r2 value of 0.730, p < 0.01 level. Conclusions: This technique can potentially reduce fieldwork and soil analysis costs considerably. Measurements of Pb and κ must share a substantial level of spatial continuity to implement CK effectively. Where applicable, it can be used in the site-specific evaluation of hazard posed by Pb exposure to ecosystems, human health or water bodies in urban green spaces, roadside soils, allotments or brownfield sites. [ABSTRACT FROM AUTHOR]

Potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) harm the ecosystem and human health, especially in urban areas. Identifying and understanding their potential sources and underlying interactions in urban soils are critical for informed management and risk assessment. This study investigated the potential sources and the spatially varying relationships between 9 PTEs and PAHs in the topsoil of Dublin by combining positive matrix factorisation (PMF) and geographically weighted regression (GWR). The PMF model allocated four possible sources based on species concentrations and uncertainties. The factor profiles indicated the associations with high-temperature combustion (PAHs), natural lithologic factors (As, Cd, Co, Cr, Ni), mineralisation and mining (Zn), as well as anthropogenic inputs (Cu, Hg, Pb), respectively. In addition, selected representative elements Cr, Zn, and Pb showed distinct spatial interactions with PAHs in the GWR model. Negative relationships between PAHs and Cr were observed in all samples, suggesting the control of Cr concentrations by natural factors. Negative relationships between PAHs and Zn in the eastern and north-eastern regions were related to mineralisation and anthropogenic Zn–Pb mining. In contrast, the surrounding regions exhibited a natural relationship between these two variables with positive coefficients. Increasing positive coefficients from west to east were observed between PAHs and Pb in the study area. This special pattern was consistent with prevailing south-westerly wind direction in Dublin, highlighting the predominant influences on PAHs and Pb concentrations from vehicle and coal combustion through atmospheric deposition. Our results provided a better understanding of geochemical features for PTEs and PAHs in the topsoil of Dublin, demonstrating the efficiency of combined approaches of receptor models and spatial analysis in environmental studies. [Display omitted] • PMF and GWR identified potential sources and spatial interactions for PTEs and PAHs. • Relationships between PAHs and PTEs were spatially varying in the topsoil of Dublin. • Negative relationships between PAHs and Cr-group were attributed to geogenic factors. • Increased positive relationships between PAHs and Pb-group occurred from west to east. • Prevailing wind direction contributed to spreading contamination for PAHs and Pb. [ABSTRACT FROM AUTHOR]

Pollution hotspots in urban soils need to be identified for better environmental management. It is important to know if there are hotspots and if the hotspots are statistically significant. In this study identification of pollution hotspots was investigated using Pb concentrations in urban soils of Galway City in Ireland as an example, and the influencing factors on results of hotspot identification were investigated. The index of local Moran's I is a useful tool for identifying pollution hotspots of Pb pollution in urban soils, and for classifying them into spatial clusters and spatial outliers. The results were affected by the definition of weight function, data transformation and existence of extreme values. Compared with the results for the positively skewed raw data, the transformed data and data with extreme values excluded revealed a larger area for the high value spatial clusters in the city centre. While it is hard to decide the best way of using this index, it is suggested that all these influencing factors should be considered until reasonable and reliable results are obtained. GIS mapping can be applied to help evaluate the results via visualization of the spatial patterns. Meanwhile, selected pollution hotspots (extreme values) in this study were confirmed by re-analyses and re-sampling. [Copyright &y& Elsevier]

Heavy metals in urban soils continue to attract attention because of their potential long-term effects on human health. During a previous investigation of urban soils in Galway City, Ireland, a pollution hotspot of Pb, Cu, Zn and As was identified in the sports ground of South Park in the Claddagh. The sports ground was formerly a rubbish dumping site for both municipal and industrial wastes. In the present study, a portable X-ray fluorescence (PXRF) analyser was used to obtain rapid in-situ elemental analyses of the topsoil (depth: about 5–10 cm) at 200 locations on a 20 × 20-m grid in South Park. Extremely high values of the pollutants were found, with maximum values of Pb, Zn, Cu and As of 10,297, 24,716, 2224 and 744 mg/kg soil, respectively. High values occur particularly where the topsoil cover is thin, whereas lower values were found in areas where imported topsoil covers the polluted substrate. Geographic Information Systems (GIS) techniques were applied to the dataset to create elemental spatial distribution maps, three-dimensional images and interpretive hazard maps of the pollutants in the study area. Immediate action to remediate the contaminated topsoil is recommended to safeguard the health of children who play at the sports ground. [ABSTRACT FROM AUTHOR]

Abstract: Galway is a small but rapidly growing tourism city in western Ireland. To evaluate its environmental quality, a total of 166 surface soil samples (0–10cm depth) were collected from parks and grasslands at the density of 1 sample per 0.25km2 at the end of 2004. All samples were analysed using ICP-AES for the near-total concentrations of 26 chemical elements. Multivariate statistics and GIS techniques were applied to classify the elements and to identify elements influenced by human activities. Cluster analysis (CA) and principal component analysis (PCA) classified the elements into two groups: the first group predominantly derived from natural sources, the second being influenced by human activities. GIS mapping is a powerful tool in identifying the possible sources of pollutants. Relatively high concentrations of Cu, Pb and Zn were found in the city centre, old residential areas, and along major traffic routes, showing significant effects of traffic pollution. The element As is enriched in soils of the old built-up areas, which can be attributed to coal and peat combustion for home heating. Such significant spatial patterns of pollutants displayed by urban soils may imply potential health threat to residents of the contaminated areas of the city. [Copyright &y& Elsevier]

Soils are the main sink of pollutants in the terrestrial environment, reflecting the historical fingerprint of urban development. To provide scientifically grounded urban management and reclamation strategies for polluted sites, the spatial patterns of pollutants should be studied first by drawing a special focus on the identification of pollution hot spots. In this paper, Pb, Mo and Ti contents in Yerevan urban soils determined by the combination of X-ray fluorescence and atomic absorption spectrometry were studied using the Local Moran's I index (LMI). These elements (Pb, Mo and Ti) have different sources and a number of distance bands (650, 800, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10,000 m and 15,000 m) were tested. This allows to reveal the optimal distance used for the identification of statistically significant spatial clusters and spatial outliers. According to the results the use of the raw data had to be excluded for elements that demonstrated highly skewed distribution whereas transformed data allowed to identify larger areas of high and low value spatial clusters. Moreover, the results of the different distance bands showed that the high and low spatial clusters became stable near the optimal distance band of 7000 m in the study area. The latter constituted the 1/3 of the maximum distance between all sample pairs. At this distance, Ti LMI results reflected the natural local geology composition whereas Mo distribution was in line with the known sources of industrial pollution ("Plant of Pure Iron"). In the case of Pb, the high-value spatial clusters were in line with the built-up urban areas and spatially correlated with the prevailing northeast winds. This study confirmed the applicability of LMI in the identification of spatial clusters and outliers at the optimal distance band which might be considered also as a break point of spatial clusters expansion and a guidance for spatial boundary of possible remediation and pollution reduction applications. Image 1 • Hot spot analysis is effective in revealing patterns of chemicals in soils. • Optimal distance for LMI is the 1/3 of the maximum length among all sampling sites. • Ti spatial clusters reflect the natural geology composition. • Mo spatial clusters were in line with the known sources of Mo emissions. • Pb spatial clusters were in line with the built-up urban areas. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) in urban soils are receiving more attention because of their increased use in modern technology. Up to now, there is little information about the spatial patterns of REEs and their influencing factors in urban soils. In this study, based on the British Geological Survey “London Earth” geochemical survey data containing a total of 6467 soil samples collected from the urban area of London, the spatial distributions of Ce, La, Nd, Sc, Sm, Yb and Y, and their influencing factors were investigated. The element Sc is included in this study as related element. Urban samples were collected at a depth of (0–20 cm), and total concentrations of 48 chemical elements were determined in the <2 mm size fraction of the topsoils using X-ray Fluorescence Spectrometry (XRFS). Spatial clusters and spatial outliers were identified using the index of local Moran's I, showing elevated concentrations of REEs in the northwest, northeast and southern parts of the study areas while all the 7 REEs exhibited generally similar spatial patterns: high values were mainly located in soils over Alluvium, Glacial till and Clay-with-flints deposits, demonstrating the close relationships between REEs and the lithology. Meanwhile, hotspot analysis revealed high values of REEs in public parks, private golf clubs, wetlands and agricultural lands especially in Hillingdon, Enfield, Brent, Harrow, Croydon and Bromley. Soil parent material was identified as the primary source for larger spatial patterns of natural origin, while smaller spatial patterns were associated with anthropogenic sources including agricultural practices, industrial activities, vehicular emission and urbanization. The REE hotspots revealed in urban soils may imply potential contamination requiring further attention. [ABSTRACT FROM AUTHOR]

Abstract: Soils are recipients of contaminants from the burning of metal-containing materials in bonfires. In order to obtain a better understanding of the impacts of bonfires on soils, a total of 218 surface soil samples were collected from a traditional bonfire site in Galway City, Ireland. Concentrations of 14 elements including Al, Ca, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sc, Ti and Zn in 30 selected samples were determined using ICP-OES. Strong variations were observed for these elements. Concentrations of Zn, Cu and Pb were elevated, indicating that these metals may be influenced by human activities. Therefore, concentrations of these three metals were further measured using a portable X-ray fluorescence (P-XRF) analyser (n =218) and their spatial distribution was investigated using a Geographical Information System (GIS). Soils with elevated metal concentrations, as evident from the spatial distribution maps, coincided with the locations of traditional festival bonfires. The results of this study provide useful information for the management of bonfire sites including the enforcement of a control policy regarding the burning of materials in bonfires. [Copyright &y& Elsevier]

Abstract: Characterization of spatial variation of urban soil geochemistry especially heavy metal pollution is essential for a better understanding of pollution sources and potential risks. A total of 294 surface soil samples were collected from a roadside sports ground in Galway, Ireland, and were analysed by ICP-OES for 23 chemical elements (Al, Ca, Ce, Co, Cu, Fe, K, La, Li, Mg, Mn, Na, Ni, P, Pb, S, Sc, Sr, Th, Ti, V, Y and Zn). Strong variations in soil geochemistry were observed and most elements, with the exception of Cu, Pb, P, S and Zn, showed multi-modal features, indicating the existence of mixed populations which proved difficult to separate. To evaluate the pollution level of the study area, the pollution index (PI) values were calculated based on a comparison with the Dutch target and intervention values. None of the concentrations of metal pollutants exceeded their intervention values, indicating the absence of serious contaminated soil, and the ratios to target values were therefore employed to produce the hazard maps. The spatial distribution and hazard maps for Cu, Pb and Zn indicated relatively high levels of pollution along the southern roadside extending almost 30m into the sports ground, revealing the strong influence of pollution from local traffic. However, heavy metal pollution was alleviated along the eastern roadside of the study area by the presence of a belt of shrubs. Therefore, in order to prevent further contamination from traffic emissions, the planting of hedging or erection of low walls should be considered as shields against traffic pollution for roadside parks. The results in this study are useful for management practices in sports and parks in urban areas. [Copyright &y& Elsevier]

Quantifying variation of metals in urban soils is crucial for efficient environmental and public health management. Prior to the interferences of human activities, regional topsoil geochemical distributions were generally primarily controlled by the underlying parent materials (PMs). With the rapid urbanisation, urban topsoil geochemical distributions have been modified with different levels. Three metals, aluminium (Al), calcium (Ca) and lead (Pb), were chosen to investigate the different levels of geogenic and anthropogenic controls in urban topsoil of Greater London Authority (GLA) area. These three metal elements clearly demonstrated the different spatial distribution affected by human activities using analysis of variance (ANOVA) and GIS-based spatial analysis. The high values of Al were in the clay which is located in the north and south GLA area; Pb accumulated in built-up areas and near traffic roads, which was likely associated with leaded paints and leaded petrol, respectively; the high Ca concentrations were in the Chalk bedrock of the southern GLA area and historical deconstruction and reconstruction sites in the city centre. Based on spatial interpolation and hot spot analysis (local Moran's I), this study reveals the different levels of geogenic and anthropogenic controls on different chemicals in urban soils: while the spatial distribution of Pb, which is more easily affected by human activities, can be significantly changed, the inert element Al may still be able to maintain its natural spatial distribution even in the heavily urbanized GLA area, and Ca demonstrates the mixed spatial distribution affected by both natural factors and human activities. • Spatial analyses were useful in identifying spatial patterns of urban geochemistry. • Different levels of geogenic and anthropogenic controls found on different chemicals. • Al was mainly controlled by geology, elevated in clay areas. • Pb was mostly under anthropogenic control, elevated in built-up area and near road. • Ca was impacted by both geogenic and anthropogenic controls. [ABSTRACT FROM AUTHOR]

• Relationships between Pb and Al in urban soils of London was spatially varying. • Positive and negative relationships were found in south and north areas, respectively. • Anthropogenic factors weakened the relationships in central London. • Large parks and greenspaces reserved the positive relationships between Pb and Al. • GWR is effective in revealing spatially varying relationships in urban soils. In this study, geographically weighted regression (GWR) was applied to reveal the spatially varying relationships between Pb and Al in urban soils of London based on 6467 samples collected by British Geological Survey. Results showed that the relationships between Pb and Al were spatially varying in urban soils of London, with different relationships in different areas. The strong negative relationships between Pb and Al were found in the northeast and north areas and weak relationships were located in central areas, implying the links with the impact of anthropogenic activities on Pb concentration, while road traffic, industry activities and construction in centre of London may be linked to the weakened or changed direction of the relationship. However, positive relationships between Pb and Al were found in large parklands and greenspaces in the southeast and southwest as well as a small area in central London, due to less influences from human activities where the natural geochemical signatures were preserved. This study suggests that GWR is an effective tool to reveal spatially varying relationships in environmental variables, providing improved understanding of the complicated relationships in environmental parameters from the spatial aspect, which could be hardly achieved using conventional statistical analysis. [ABSTRACT FROM AUTHOR]