粤北韶关市冬季大气颗粒物中多环芳烃的粒径分布特征

2012年12月4日—11日,使用微孔均匀撞击式采样器(MOUDI)连续7 d采集广东省韶关市3个环境空气监测点气溶胶样品,采用GC/MS测定包括美国国家环保局(USEPA)优控多环芳烃(Σ16PAHs)在内的17种PAHs的浓度水平,并分析Σ16PAHs的粒径分布特征和来源。结果表明:韶关市冬季气溶胶颗粒中Σ16PAHs的质量浓度为17.29 ng/m3~23.97 ng/m3;Σ16PAHs集中在1.0μm~3.2μm的积聚态和粗颗粒中,呈单峰分布特征;比值参数分析显示,韶关市大气颗粒物中PAHs主要来自燃煤和汽车尾气的排放。     

Distribution and seasonal variability of trace elements in atmospheric particulate in the Venice Lagoon

Size distribution and selected element concentrations of atmospheric particulate matter (PM) were investigated in the Venice Lagoon, at three sites characterised by different anthropogenic influence. The PM₁₀ samples were collected in six size fractions (10-7.2, 7.2-3.0, 3.0-1.5, 1.5-0.95; 0.95-0.49 and <0.49 μm) with high volume cascade impactors, and the concentration of 17 elements (Al, As, Ca, Cd, Co, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, V, Zn) was determined by inductively coupled plasma quadrupole mass spectroscopy. More than 1 year of sampling activities allowed the examination of seasonal variability in size distribution of atmospheric particulates and element contents for each site.At all the stations, particles with an aerodynamic diameter <3 μm were predominant, thus accounting for more than 78% of the total aerosol mass concentration. The highest PM₁₀ concentrations for almost all elements were found at the site which is more influenced by industrial and urban emissions. Similarity in size distribution of elements at all sites allowed the identification of three main behavioural types: (a) elements found mainly within coarse particles (Ca, Mg, Na, Sr); (b) elements found mainly within fine particles (As, Cd, Ni, Pb, V) and (c) elements with several modes spread throughout the entire size range (Co, Cu, Fe, K, Zn, Mn).Factor Analysis was performed on aerosol data separately identified as fine and coarse types in order to examine the relationships between the inorganic elements and to identify their origin. Multivariate statistical analysis and assessment of similarity in the size distribution led to similar conclusions on the sources.     

Sorption of 17α-ethinyl estradiol, bisphenol A and phenanthrene to different size fractions of soil and sediment

The potential for negative effects caused by endocrine disrupting chemicals (EDCs) release into the environment is a prominent concern and numerous research projects have investigated possible environmental fate and toxicity. However, their sorption behavior by size fractions of soil and sediment has not been systematically represented. The sorption of bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and phenanthrene (Phen) by different size fractions of soil and sediment were investigated. Sorption isotherms of EE2, BPA, and Phen by size fractions of soil (SL) and sediment (ST) were well fitted to the Freundlich model. The positive correlation between EE2, BPA and Phen sorption capacity (log K_d) of size fractions and their organic carbon (OC) content suggests that OC of size fractions in SL and ST should regulate sorption, while the surface area (SA) of size fractions may not account for sorption of EE2, BPA and Phen. Each size fraction of ST had higher sorption capacity (K_d or K_OC) of EE2 and BPA than that of SL due to their difference in the polarity of organic matter (OM) between terrestrial and aquatic sources. Sorption capacity logK_d for size fractions of SL and ST did not follow the order: clay > silt > sand due to the difference in OM abundance and composition between the size fractions. Large particle fractions of ST contributed about 80% to the overall sorption for any EE2, BPA, and Phen. This study was significant to evaluate size fractions of soil and sediment as well as their associated OM affecting EE2 and BPA sorption processes.     

我国西北典型大城市大气可吸入颗粒物浓度分布特征

我国西北地区冬季寒冷、春季多风沙天气,空气中的可吸入颗粒物(PM10)浓度较高,利用兰州、西宁、乌鲁木齐、银川、呼和浩特等城市2000年6月～2007年12月每日浓度最高的大气主要污染物(SO2,NO2,PM10)浓度资料,研究了5个省会城市PM10分布特征。结果表明,五个城市PM10污染都较严重,PM10为主要污染物的日数每月平均超过20天。五个城市的季节分布特征类似,冬春季浓度较高,平均值都达到了国家二级污染标准,夏秋季相对低一些。其中,兰州和乌鲁木齐冬季浓度值远高于其他城市。五个城市均属煤烟沙尘型污染,但煤烟和沙尘的影响程度有所不同。     

Polycyclic aromatic hydrocarbons in bulk PM2.5 and size-segregated aerosol particle samples measured in an urban environment

To analyze polycyclic aromatic hydrocarbons (PAHs) at an urban site in Seoul, South Korea, 24-hr ambient air PM_2.5 samples were collected during five intensive sampling periods between November 1998 and December 1999. To determine the PAH size distribution, 3-day size-segregated aerosol samples were also collected in December 1999. Concentrations of the 16 PAHs in the PM_2.5 particles ranged from 3.9 to 119.9 ng m⁻³ with a mean of 24.3 ng m⁻³.An exceptionally high concentration of PAHs(∼120 ng m⁻³) observed during a haze event in December 1999 was likely influenced more by diesel vehicle exhaust than by gasoline exhaust, as well as air stagnation, as evidenced by the low carbon monoxide/elemental carbon (CO/EC) ratio of 205 found in this study and results reported by previous studies. The total PAHs associated with the size-segregated particles showed unimodal distributions. Compared to the unimodal size distributions of PAHs with modal peaks at < 0.12 μm measured in highway tunnels in Los Angeles (Venkataraman and Friedlander, 1994), four- to six-ring PAHs in our study had unimodal size distributions, peaking at the larger size range of 0.28–0.53 μm, suggesting the coagulation of freshly emitted ultrafine particles during transport to the sampling site. Further, the fraction of PAHs associated with coarse particles(> 1.8 μm) increased as the molecular weight of the PAHs decreased due to volatilization of fine particles followed by condensation onto coarse particles.     

Characteristics of the water-soluble components of aerosol particles in Hefei, China

Size-classified daily aerosol mass concentrations and concentrations of water-soluble inorganic ions were measured in Hefei,China,in four representative months between September 2012 and August 2013.An annual average mass concentration of 169.09μg/m~3 for total suspended particulate(TSP)was measured using an Andersen Mark-II cascade impactor.The seasonal average mass concentration was highest in winter(234.73μg/m~3)and lowest in summer(91.71μg/m~3).Water-soluble ions accounted for 59.49%,32.90%,48.62%and 37.08%of the aerosol mass concentration in winter,spring,summer,and fall,respectively,which indicated that ionic species were the primary constituents of the atmospheric aerosols.The four most abundant ions were NO_3~-,SO_4~(2-),Ca~(2+) and NH_4~+.With the exception of Ca~(2+),the mass concentrations of water-soluble ions were in an intermediate range compared with the levels for other Chinese cities.Sulfate,nitrate,and ammonium were the dominant fine-particle species,which were bimodally distributed in spring,summer and fall;however,the size distribution became unimodal in winter,with a peak at 1.1–2.1μm.The Ca~(2+) peak occurred at approximately 4.7–5.8μm in all seasons.The cation to anion ratio was close to 1.4,which suggested that the aerosol particles were alkalescent in Hefei.The average NO_3~-/SO_4~(2-)mass ratio was 1.10 in Hefei,which indicated that mobile source emissions were predominant.Significant positive correlation coefficients between the concentrations of NH_4~+ and SO_4~(2-),NH_4~+ and NO_3~-,SO_4~(2-)and NO_3~-,and Mg~(2+) and Ca~(2+) were also indicated,suggesting that aerosol particles may be present as(NH_4)_2SO_4,NH_4HSO_4,and NH_4NO_3.     

Water chemistry influences on long-term dissolution kinetics of CdSe/ZnS quantum dots

Widespread usage of engineered metallic quantum dots(QDs) within consumer products has evoked a need to assess their fate within environmental systems.QDs are mixed-metal nanocrystals that often include Cd~(2+)which poses a health risk as a nanocrystal or when leached into water.The goal of this work is to study the long-term metal cation leaching behavior and the factors affecting the dissolution processes of mercaptopropionic acid(MPA) capped CdSe/ZnS QDs in aphotic conditions.QD suspensions were prepared in different water conditions,and release of Zn2+and Cd~(2+) cations were monitored over time by size exclusion chromatography-inductively coupled plasm a-mass spectrometry.In most conditions with dissolved 02 present,the ZnS shell degraded fairly rapidly over～1 week,while some of the CdSe core remained up to 80 days.Additional MPA,Zn~(2+),and Cd2+temporarily delayed dissolution,indicating a moderate role for capping agent detachment and mineral solubility.The presence of H_2 O_2 and the ligand ethylenediaminetetraacetate accelerated dissolution,while NOM had no kinetic effect.No dissolution of CdSe core was observed when 02 was absent or when QDs formed aggregates at higher concentrations with 02 present.The shrinking particle model with product layer diffusion control best describes Zn2+and Cd~(2+) dissolution kinetics.The longevity of QDs in their nanocrystal form appears to be partly controlled by environmental conditions,with anoxic,aphotic environments preserving the core mineral phase,and oxidants or complexing ligands promoting shell and core mineral dissolution.     

Size distribution and source of heavy metals in particulate matter on the lead and zinc smelting affected area

In order to understand the size distribution and the main kind of heavy metals in particulate matter on the lead and zinc smelting affected area, particulate matter(PM) and the source samples were collected in Zhuzhou, Hunan Province from December 2011 to January 2012 and the results were discussed and interpreted. Atmospheric particles were collected with different sizes by a cascade impactor. The concentrations of heavy metals in atmospheric particles of different sizes, collected from the air and from factories, were measured using an inductively coupled plasma mass spectrometry(ICP-MS). The results indicated that the average concentration of PM, chromium(Cr), arsenic(As), cadmium(Cd) and lead(Pb) in PM was177.3 ± 33.2 μg/m~3, 37.3 ± 8.8 ng/m~3, 17.3 ± 8.1 ng/m~3, 4.8 ± 3.1 ng/m~3 and 141.6 ± 49.1 ng/m~3,respectively. The size distribution of PM displayed a bimodal distribution; the maximum PM size distribution was at 1.1–2.1 μm, followed by 9–10 μm. The size distribution of As, Cd and Pb in PM was similar to the distribution of the PM mass, with peaks observed at the range of1.1–2.1 μm and 9–10 μm ranges while for Cr, only a single-mode at 4.7–5.8 μm was observed. PM(64.7%), As(72.5%), Cd(72.2%) and Pb(75.8%) were associated with the fine mode below 2.1 μm,respectively, while Cr(46.6%) was associated with the coarse mode. The size distribution characteristics, enrichment factor, correlation coefficient values, source information and the analysis of source samples showed that As, Cd and Pb in PM were the typical heavy metal in lead and zinc smelting affected areas, which originated mainly from lead and zinc smelting sources.     

Science and values in risk assessment: The case of deliberate release of genetically engineered organisms

To make more responsible decisions regarding risk and to understand disagreements and controversies in risk assessments, it is important to know how and where values are infused into risk assessment and how they are embedded in the conclusions. In this article an attempt is made to disentangle the relationship of science and values in decision-making concerning the deliberate release of genetically modified organisms (GMOs) into the environment. This exercise in applied philosophy of science is based on Helen Longino's contextual empiricism which attempts to reconcile the objectivity of science with its social and cultural construction. Longino distinguishes different levels of research on which values apparently contextual with respect to a given research program can shape the knowledge emerging from that program. Her scheme is applied for locating and identifying the values that affect environment risk assessments of the field experiments with GMOs. The article concludes with some provisional suggestions for the decision process and the role of scientists in it.