Spatial Analysis of PAHs in Soils along an Urban–Suburban–Rural Gradient: scale effect, distribution patterns, diffusion and influencing factors

Abstract

Spatial statistical methods including Cokriging interpolation, Morans I analysis, and geographically weighted regression (GWR) were used for studying the spatial characteristics of polycyclic aromatic hydrocarbon (PAH) accumulation in urban, suburban, and rural soils of Beijing. The concentrations of PAHs decreased spatially as the level of urbanization decreased. Generally, PAHs in soil showed two spatial patterns on the regional scale: (1) regional baseline depositions with a radius of 16.5 km related to the level of urbanization and (2) isolated pockets of soil contaminated with PAHs were found up to around 3.5 km from industrial point sources. In the urban areas, soil PAHs showed high spatial heterogeneity on the block scale, which was probably related to vegetation cover, land use, and physical soil disturbance. The distribution of total PAHs in urban blocks was unrelated to the indicators of the intensity of anthropogenic activity, namely population density, light intensity at night, and road density, but was significantly related to the same indicators in the suburban and rural areas. The moving averages of molecular ratios suggested that PAHs in the suburban and rural soils were a mix of local emissions and diffusion from urban areas.

Assessing the Spatial Distribution of Soil PAHs and their Relationship with Anthropogenic Activities at a National Scale

“…Soil contamination with PAHs has been one of the most important environmental problems worldwide and requires an urgent solution [13][14][15]. At present, many places have been polluted with PAHs, such as Miami in the USA [16], Delhi in India [17], Beijing in China [18], Esbjerg in Denmark [19], Tyumen Oblast in Russia [20], and Ulsan in Korea [21,22], which, among others, have been studied by international researchers [23][24][25]. Nam et al [26] found that the average background PAH concentration in different soils worldwide followed the order Europe > North America > Asia >Oceania > Africa > South America.…”

Indigenous14C-phenanthrene biodegradation in “pristine” woodland and grassland soils from Norway and the United Kingdom

“…Concerns over their chronic toxicity (mutagenicity and carcinogenicity), environmental persistence and ubiquitous presence in the environment have driven research interest into their sources and processing in the environment. 1,2 Most spatial distributions of PAHs in soils vary in scale and occur through diffuse pollution, [3][4][5][6] owing to the degree of remote economic development, population density, landscape, vegetation and land use. 7,8 This results in the contamination of large areas with hotspots having high PAH concentrations and is characterised by the absence of identiable point sources.…”

A new risk probability calculation method for urban ecological risk assessment

“…The land use types of the marginal areas of the city are mainly forest, grassland, and farmland. Such land use spatial pattern indicates that the areas within the Sixth Ring Road exhibit an obvious urbansuburban gradient (Peng et al 2016), and thus it is an ideal area for urbanization research.…”