Yingming Xu

Sorption of Pb2+ on mercapto functionalized sepiolite.

Mercapto functionalized sepiolite (MSEP) was prepared by nanotexturization method and applied for the sorption of Pb(2+) from aqueous solution. These samples before and after sorption were characterized through XRD, FT-IR, (29)Si and (13)C CP/MAS NMR and XPS. The sorption behaviors including thermodynamic and kinetic parameters, effect factors and mechanisms of Pb(2+) sorption on MSEP were studied. The maximum sorption amounts of 97 mg g(-1). The parameters ΔH(0) and ΔS(0) were 33.637 kJ mol(-1) and 202.697 J mol(-1) K(-1), respectively. Freundlich isotherm was proved to describe the sorption data better than other isotherms and pseudo second order kinetic model could fit the sorption kinetic processes well. The pH influenced the sorption of Pb(2+) on MSEP significantly but background electrolytes have relative weak effect. Based on hard and soft acids and bases theory and the results analyzed from XPS, the sorption mechanisms could be explained as primarily chemical adsorption and secondary physical adsorption.

Polycyclic Aromatic Hydrocarbon (PAH) Contamination in the Urban Topsoils of Shenyang, China

Polycyclic aromatic hydrocarbons (PAHs) in the surface urban soils of Shenyang in Northeastern China were investigated. The total concentration of the PAHs ranged from 0.09 to 8.35 mg kg−1, with an average value of 1.51 ± 1.64 mg kg−1. 3–5-ring PAHs accounted for 90% of total PAHs. The functional areas, such as the industrial regions (4.95 mg kg−1) and main roads (1.56 mg kg−1), as well as the administrative divisions, including the districts of Shenhe (1.49 mg kg−1), Heping (2.08 mg kg−1), and Tiexi (2.14 mg kg−1), were heavily polluted by PAHs. The diagnostic ratios and principal component analysis (PCA) for PAHs indicate that the pollutants probably originated primarily from coal combustion and petroleum sources. The Nemerow composite index, used to assess environmental quality, shows that the soil samples were heavily polluted with PAHs, and although 52.8% of the soil sampling sites were safe, 47.2% of the soil sampling sites registered different grades of PAH pollution. The PAH contamination in Shenyang emphasizes the need for controlling fossil fuel combustion and traffic exhaust.

Determination of Carbendazim and Diethofencarb in Cotton and Soil by High-Performance Liquid Chromatography

ABSTRACT A simple and reliable method was developed to determine carbendazim and diethofencarb in cotton, cotton seeds, and soil. The decomposition of carbendazim and diethofencarb in the cotton field ecosystem was also studied. The analytes were extracted and quantified by high-performance liquid chromatography. The limits of detection were 0.1 ng for carbendazim and diethofencarb. The limits of quantification of carbendazim and diethofencarb were 0.1 mg kg−1 in cotton, 0.1 mg kg−1 in cotton seeds, and 0.02 mg kg−1 in soil. The average recoveries of cotton, cotton seed, and soil were measured at three fortified concentrations and were in the range of 77.5–103.9% for carbendazim and 80.9–104.6% for diethofencarb. The relative standard deviations were less than 9.0% for both pesticides. In field experiments, the half-lives of carbendazim and diethofencarb were in the range of 2.3–9.1 days and 2.3–8.9 days in cotton at two locations in China. At harvest, cotton seeds contained carbendazim and diethofencarb well below the maximum residue limit of the Japanese “Positive List System” (3 mg kg−1) following the recommended dosage with measurement 10 and 20 days following the final application.