Abstract
Rapid urbanization causes the accumulation of large amounts of pollutants, including heavy metals, organic pollutants, and black carbon (BC). BC is the carbonaceous residue generated from the incomplete combustion of fossil fuels and biomass. It plays an important role on the migration of heavy metals and organic pollutants, as well as soil carbon sequestration. BC accumulation due to human activities greatly affects the global carbon budget, helps to drive climate change, and damages human health. To date, few studies have examined how the intensity of urbanization affects the distribution of BC in soils in urban areas. Therefore, the objective of this study is to determine the effects of urbanization intensity on the spatial distribution and content of BC in urban surface soil. We collected samples from 55 sites in South China and used a multi-scale geographical regression model to evaluate the impact of the interference intensity of urbanization on the amount and distribution of BC. Our results showed that the BC content was significantly higher in urban areas (9.74 ± 1.18 g kg−1) than in rural areas (2.94 ± 0.89 g kg−1) and that several urban parks with a higher interference intensity were hotspots of BC accumulation, suggesting that urbanization promoted BC accumulation. Our model revealed that road density was significantly and positively correlated with BC accumulation. Because there are more cars driving in areas with high road density, vehicle emissions may be one of the causes of BC accumulation. Our results also indicated that the impact of urbanization intensity on the BC distribution was sensitive to sampling density.
Highlights
Introduction iationsBlack carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 μm in aerodynamic diameter)
The maps show that the black carbon (BC) content is higher in the urban areas, especially in several urban parks, than it is in the rural areas
The amount of BC, the BC/OC ratio, and the enrichment factor (EF) of BC in the soils were higher in the urban areas, which had a high interference intensity than that in the soils in rural areas, which had a very low interference intensity
Summary
Introduction iationsBlack carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 μm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and is one of the main types of particles in both anthropogenic and naturally occurring soot [1,2]. Human activities, such as fossil fuel combustion, vehicle emissions, and garbage incineration, significantly increase BC accumulation [3]. Most BC eventually enters the soil and becomes part of the soil carbon pool [4]. It is estimated that BC accounts for 5–45% of surface soil organic carbon (SOC) and, in some places, as much as 60% of SOC, making it an important part of the soil carbon pool [5,6]. BC accumulation caused by human activities greatly impacts the global carbon budget, helps to drive climate change, and are deleterious to human health [4,7–10]
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