Morphology, molecular structure, and stable carbon isotopic composition of black carbon (BC) in urban topsoils

Abstract

Urban soils contain significant amounts of black carbon (BC) from biomass and fossil fuel combustion and regard to be a pool of BC. BC in urban soils has multiple effects on environmental processes in urban system, such as global climate change, air quality, and public health. Urban topsoil samples (0-10 cm) were collected from Anshan, Liaoning Province, northeast China, which is one of the most important old steel industrial bases in China. The BC in urban topsoils was extracted using the density method. Their chemical composition, morphology, molecular structure, and stable carbon isotopic composition were examined using elemental analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and stable carbon isotope (δC). Elemental analysis shows that carbon content in the BC of studied soils ranged from 64.5 to 78.4%, with the average more than 70%. The O/C atomic ratio of BC is on average 0.18. The BC particle displays different morphology, including porous spherical, irregular porous fragmentary, and blocky shapes. The porous spherical BC particles has atomic molar O/C ratio determined by SEM-EDS ranging from 0.04 to 0.37. XRD indicates that BC exists in mainly combining with mineral phases hematite (FeO), kaolinite (AlSiO(OH)), quartz (SiO), and calcite (CaCO). The FTIR spectra of BC particles show major bands at approximately 3400 cm (O-H), 2920 cm (C = H), 1600 cm (C = C), 1230 cm (C = O), and 1070 cm (C = O). The stable carbon isotope (δC) of BC ranges from -24.48 to -23.18‰ with the average of -23.79 ± 0.39‰. The concentration of BC in the industrial area is significantly (p < 0.05) higher than that in the roadside area. The BC of industrial area is characterized by porous spherical structure, suggesting that they are mainly derived from fossil fuel combustion. Results indicated that a combination of atomic O/C ratio, porous structure, and stable carbon isotopic (δC) of BC could reflect effectively the origin of BC in urban topsoils. It could conclude that BC in Anshan urban topsoil was mainly from fossil fuel combustion.

Stable-isotopic and metagenomic analyses reveal metabolic and microbial link of aerobic methane oxidation coupled to denitrification at different O2 levels

“…Vario MICRO cube elemental analyzer coupled to the GV Isoprime 100 isotope ratio mass spectrometer (GV Instruments, UK) as described previously (Zong et al, 2018).…”

Evaluation of the cytotoxic and genotoxic effects by melamine and cyanuric acid co-exposure in human embryonic kidney 293 cells

“…Immunofluorescent microscopy was performed as described previously (15,16). Briefly, cells were seeded into a 6-well culture plate at a density of 1 Â10 5 cells/well, with each well containing a glass coverslip.…”

“…The alkaline comet assay was conducted as described earlier with certain modifications (15,16). Briefly, fully frosted microscope slides were first covered with 150 mL of 0.65% normal melting point agarose and immediately covered with a coverslip.…”

“…The ultrastructure of calculi from kidneys of the mice were examined using a field-emission scanning electron microscope (FSEM, SIRION-100; FEI, USA) equipped with a GENESIS4000 energy dispersive X-ray spectroscope (EDS, EDAX-GENESIS4000, USA) microanalyzer operated at 25 kV and 280 mA (16). The measurements are reported in micrometers (mM).…”

Effects of Urbanization Intensity on the Distribution of Black Carbon in Urban Surface Soil in South China

“…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]. In addition, 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][8][9][10].…”