Diandou Xu

Beyond PM2.5: The role of ultrafine particles on adverse health effects of air pollution.

BACKGROUND Air pollution constitutes the major threat to human health, whereas their adverse impacts and underlying mechanisms of different particular matters are not clearly defined. SCOPE OF REVIEW Ultrafine particles (UFPs) are high related to the anthropogenic emission sources, i.e. combustion engines and power plants. Their composition, source, typical characters, oxidative effects, potential exposure routes and health risks were thoroughly reviewed. MAJOR CONCLUSIONS UFPs play a major role in adverse impacts on human health and require further investigations in future toxicological research of air pollution. GENERAL SIGNIFICANCE Unlike PM2.5, UFPs may have much more impacts on human health considering loads of evidences emerging from particulate matters and nanotoxicology research fields. The knowledge of nanotoxicology contributes to the understanding of toxicity mechanisms of airborne UFPs in air pollution. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

Study of chemical speciation of trace elements by molecular activation analysis and other nuclear techniques

The information on the chemical speciation of trace elements in biological and environmental systems is much needed to evaluate their biological and environmental significance. Albeit a number of atomic behavior-based analytical techniques are available for the analysis of chemical speciation of trace elements, nuclear analytical techniques, especially the molecular activation analysis method, can in many cases play a unique role. This review describes the methodology, merits and limitations of nuclear analytical techniques for chemical speciation study in biological and environmental samples. The emphases are focused on the chemical species and the environmental and biological significance of rare earth elements in natural plants and human liver, selenium in a mammalian organism, mercury in rat brain and liver, chromium in rat organs and Cr-rich yeast, organohalogens in pine needles and marine organisms, and iodine in sea-water, soil, atmosphere, marine plants and the thyroid gland for demonstration of the features of nuclear analytical techniques. The future perspectives of nuclear analytical techniques for the study of chemical species of trace elements will be briefly outlined as well.

2001 survey of organochlorine pesticides in retail milk from Beijing, P R China.

A monitoring study was conducted in 2001 to determine the organochlorine pesticides and their metabolite residues in milk taken from supermarkets in Beijing, P. R. China. The average concentrations of total HCH and DDT were 0.038 and 0.046 mg kg-1, respectively, expressed on a fat basis. The aldrin residue was detected in nine milk samples, with a mean concentration of 0.035 mg kg-1. Heptachlor and its epoxides were not found in any milk samples. Of 72 milk samples analysed, three from South China contained the higher levels of DDT and HCH residues that exceeded the FAO/WHO accepted tolerance level. Although organochlorine pesticides such as DDT and HCH have been banned in China since 1983, the residues of such compounds still exist in the environment and cause food contamination, a fact likely attributed to the short prohibition period and illegal use for agricultural purposes at present.

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.

Neutron activation analysis of extractable organohalogens in milk from China

Instrumental neutron activation analysis (INAA) has been used for the determination of extractable organohalogens (EOX) in milk. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The EOX concentrations in milk samples from various regions of China were determined. Meanwhile, organochlorine pesticides residues were detected by gas chromatography. The concentrations of the EOX in the milk samples are decreasing in the order of EOCl >> EOBr > EOI, and EOCl accounts for 95% of the total EOX. The average concentration of EOCl in milk is 4.44 ·g/g expressed as fat weight basis, with the highest value of 17.6 ·g/g from South China. The mean concentrations of total HCH and DDT are 0.038 ·g/g and 0.046 ·g/g, respectively. Organochlorine pesticides account only for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the milk sample.

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%.

Determination of extractable organic halogens in pine needles by neutron activation analysis

Pine needles were collected from four different Chinese regions and measured by instrumental neutron activation analysis (INAA) combined with organic solvent extraction method for the concentrations and distribution of extractable organohalogens (EOX), including extractable organochlorinated (EOCl), organobrominated (EOBr) and extractable organoiodinated compounds (EOI). The concentrations of EOCl, EOBr and EOI are 0.5-6.0, 0.06-0.54 and 0.013-0.4 µg/g dry weight, respectively, which are increasing in the order of EOCl >> EOBr > EOI. EOCl accounts for more than 86%, while the latter two are less than 10% and 6% of total EOX. 5-38% of EOCl exist as extractable persistent organochlorinated compounds (EPOCl) after treatment with concentrated sulfuric acid. The relative proportion of the known organochlorinated pesticides (OCPs) to total EPOCl is 3.0-19.8%.