Lingling Ma

Levels and speciation of arsenic in the atmosphere in Beijing, China.

Arsenic levels and speciation in the total suspended particles (TSPs) were quantitatively determined by high performance liquid chromatography on-line coupled with hydride generation atomic fluorescence spectrometry in Beijing, China from February 2009 to March 2011. The high TSP levels fluctuated between 0.07 and 0.79 mg m(-3), with a mean level of 0.32 ± 0.17 mg m(-3). The total arsenic concentrations ranged from 0.03 to 0.31 μg m(-3) (mean: 0.13 ± 0.06 μg m(-3)) in Beijings air. The concentrations of As(III) and As(V) ranged from 0.73 to 20 ng m(-3) (mean: 4.7 ± 3.6 ng m(-3)) and from 14 to 2.5 × 10(2) ng m(-3) (mean: 67 ± 35 ng m(-3)), respectively. As levels and speciation demonstrated relative higher levels in spring and autumn and lower values in summer and winter. As(V) accounted for 81-99% of the extractable species in the TSP samples which showed that As(V) was the major fraction of the extractable As. Organoarsenic species, monomethylarsonate (MMA) and dimethylarsinate (DMA) were not found in all samples. Higher values of enrichment factors demonstrated that arsenic in TSP mainly come from anthropogenic sources. High As and its species levels in air and respiratory exposure (0.30-0.84 μg d(-1)) attributed to higher excess cancer risk ((4.2 ± 2.0) × 10(-4)) for people in Beijing.

A review of measurement methodologies and their applications to environmental 90Sr

The high fission yield product 90Sr has been released into the environment in large amounts due to nuclear weapon tests, nuclear power plant accidents, and nuclear fuel reprocessing industries. It is a long half-life radionuclide (28.9 y), with serious consequences to human health; hence, it is desirable to perform routine monitoring of 90Sr in environmental samples. Many 90Sr radiometric methods have been developed in the past decades, which generally require complicated separation and purification steps with a relatively long analytical time. Moreover, some nominally rapid methods usually have high method detection limits, making them unsuitable for the environmental samples with ultra-low 90Sr levels. In this review, some rapid and practical methods for 90Sr routine monitoring are summarized. Different sample pretreatments and major purification procedures for 90Sr developed in recent years, such as variable digestion methods and extraction chromatography using Sr resin or DGA resin, are especially described. Additionally, four conventional and widely used β spectrometric and mass spectrometric methods are demonstrated. Finally, 90Sr evaluations focusing on contaminated soil and seawater samples collected after the Fukushima Daiichi Nuclear Power Plant accident, and 90Sr application as tracers for environmental behavior are also reviewed.

Vertical distribution of heavy metals and its response to organic carbon in red soil profile

The vertical distribution patterns, the source and correlation of heavy metals were characterized in the bulk soil and different soil aggregates of arable red soil profile (0-100 cm) in Hunan province. Their response to organic carbons in proflie was explored as well. Principal component analysis (PCA) suggested that elements could be divided into two principal components, the metals of the first group were Zn,Cu,Pb,As,Cd, and the second group metals were Cr, Ni. Priniciple component elements had similar sources. In 0-30 cm, The first group metals decreased with increasing depth, the second group metals increased with increasing depth. The concentrations of typical heavy metals were in the order of Zn >Cr >Cu >Pb >Ni >As >Cd. Cd in each soil layer was severely polluted, Zn was at level of light pollution, while other metals were at clean levels. In terms of different size of soil aggregate, it was found that colloids played an important role in facilitating transport of heavy metals, such as As, Cu, Zn, Cd, Cr, Ni. While Pb was still mainly enriched in clay component (<53 μm). Infrared spectrum analysis showed that the main functional groups of organic carbon were polysaccharide (22.07%-47.13%), aromatic (13.88%-34.37%) and alcohol (21.04%-59.49%). Correlation analysis showed that stable organic carbon such as polysaccharide and aromatic organic carbon could stablize the metals of first group in profiles, which would delay the migration of heavy metals to deeper soil. However, the active alcohol carbon would enhance the migration.

Molecular modification of proanthocyanidins

ABSTRACT Regioselective enzymatic acylation of proanthocyanidin is proposed and investigated as a method by which to improve the solubility of proanthocyanidins in the oil phase and maintain its oxidation resistance. Experimental results indicate that butanol functions as the best solvent in the studied reaction, in which Lipase Novozym435 is used as biological catalyst enzyme and the molar ratio of lauric acid to proanthocyanidins is 4:1. To increase the esterification conversion, we propose the addition of molecular sieve at 5 h. The product was separated by TLC, and results indicate an optimal solvent ratio of ethyl acetate: petroleum ether: acetic acid = 2:3:0.5. This condition can effectively separate the ester and proanthocyanidins, achieving an esterification yield of 60.9%.