森林土壤种子库研究进展

土壤种子库与物种多样性存在密切相关性,森林土壤种子库是植被天然更新的物质基础。文章阐述了森林土壤种子库的内涵、森林生态系统土壤种子库的基本特征及其主要研究方法,探讨了影响种子库的基本因素及当前极为关注的热点问题。在受损森林生态系统目标树种培养、植被群落快速恢复和生态系统科学管理等领域仍存在一些理论和实践急待解决的问题,如随着群落进展演替土壤种子库种子数量在增加而质量却在逐渐下降,面临如何解决生态系统健康稳定发育和物种多样性长期维持问题。文章认为今后应加强土壤种子库与生物多样性保护、防止外来物种入侵乡土物种利用及对全球变化的响应等领域的研究工作,以期为从事森林土壤种子库研究和退化森林植被群落恢复实践提供理论指导。     

UV-B增加与酸雨复合处理对大豆种子萌发和幼苗生长的影响

研究了UV-B辐射增加与酸雨的复合处理对大豆种子萌发和幼苗生长的影响。结果表明：UV-B辐射增加对大豆种子的萌发没有影响，酸雨处理降低了大豆种子的发芽率。UV-B辐射增加与酸雨的复合处理，降低了幼苗的株高、绿叶数、叶面积、干质量、叶绿素和蒸腾速率，复合胁迫的下降幅度明显高于单一因子胁迫，并且下降幅度受UV-B辐射强度与酸雨pH的影响。UV-B辐射增加与酸雨处理在抑制幼苗生长上具有协同作用。     

大气气溶胶研究新动向

本文概述了近年大气气溶胶研究的四个主要方面:大气气溶胶的表征、大气化学过程与气候变化、健康效应等的概况.阐明了当今大气气溶胶研究的趋向,主要着重于PM_(10)和PM_(2.5)细颗粒(可吸入颗粒物或二次颗粒物)的物理化学特性与环境行为、生态效应,更重视气溶胶的非均相化学反应过程;其研究范围,从平流层向对流层发展,并密切结合气候变化、健康影响等有关的一些实际问题,进行深层次的综合性研究.大气气溶胶化学已成为当今大气化学研究最前沿的领域.     

大气气溶胶物质来源研究进展

大气气溶胶物质来源研究是大气污染研究极为重要的内容,它对污染物质的追踪评价具有较大的意义。本文较为系统地讨论了大气气溶胶物质来源研究的现状。从气溶胶的特征上分别论述气溶胶物质来源的矿物学（ 颗粒） 、无机化学和有机化学研究的进展。     

Measurement of particulate aliphatic and polynuclear aromatic hydrocarbons in Santiago de Chile: source reconciliation and evaluation of sampling artifacts

Using a novel sampler, particulate organic compounds were collected in Santiago de Chile from June 9 to August 10, 1997. This sampler consists of a diffusion denuder to remove gas-phase organics prior to particle collection, a Teflon filter, and a PUF cartridge downstream of the filter. PAHs and n-alkanes were measured using gas chromatography/mass spectrometry analysis. Volatilization of particles collected on the Teflon filter varied from 15 to 85% for both n-alkanes and PAHs, with strong dependence on molecular weight. The relative distribution of n-alkanes and the values of molecular diagnostic ratios, such as Carbon preference index, indicated a mixed origin with strong anthropogenic input. Indeed, CPI values ranged from 0.66 to 1.96 (for the whole range of n-alkanes). The percent contribution of leaf “wax” n-alkanes (4.55–20.83%) indicated the low contribution of biogenic sources. In addition, the distribution pattern of PAHs was characteristic of anthropogenic emissions. The dominant contribution of combustion-related PAHs (CPAHs), 74–84%, indicated that vehicular emissions was the major source of PAHs.     

Reduction of sampling and analytical errors for electron microscopic analysis of atmospheric aerosols

Electron microscopy-energy dispersive spectroscopy (EM/EDS) can be used to determine the elemental composition of individual particles. However, the accuracy with which atmospheric particle compositions can be quantitatively determined is not well understood. In this work we explore sources of sampling and analytical bias and methods of reducing bias. Sulfuric acid [H₂SO₄] and ammonium sulfate [(NH₄)₂SO₄] particles were collected on beryllium, silicon, and carbon substrates with similar deposition densities. While [(NH₄)₂SO₄] particles were observed on all substrates, [H₂SO₄] and ammonia-treated [H₂SO₄] particles could not be found on beryllium substrates. Interactions between the substrate and sulfuric acid particles are implicated. When measured with EM/EDS, [H₂SO₄] particles exposed to ammonia overnight were found having lower beam damage rates (0.000 ± 0.002 fraction s⁻¹) than those without any treatment (0.023 ± 0.006 fraction s⁻¹) For laboratory-generated [C₁₀H₆(SO₃Na)₂] particles, the composition determined using the experimental k-factors evaluated from independent particle standards of similar composition and size shows an error less than 20% for all constituents, while greater than 78% errors were found when k-factors were calculated from the theory. This study suggests (1) that sulfate beam damage can be reduced by exposure of atmospheric particle samples to ammonia before analysis, (2) that beryllium is not a suitable substrate for atmospheric particle analysis, and (3) calibration (k-factor determination) using particle standards of similar size and composition to particles present in the atmosphere shows promise as a way of improving the accuracy of quantitative EM analysis.     

Size distribution of black (BC) and total carbon (TC) in Vienna and Ljubljana

During two campaigns in winter 2004, size segregated impactor samples (0.1-10 microm) and filter samples were taken in two Central European cities (Vienna, Austria and Ljubljana, Slovenia). The impactor samples were analyzed for major inorganic ions and short-chain organic acids, total carbon (TC) and black carbon (BC). Maximum concentrations of total mass were 71.6 microg m(-3) in Vienna and 73.1 microg m(-3) in Ljubljana. Minimum concentrations in Vienna were only half those in Ljubljana. The BC content of the aerosol was similar (ca. 8%), but the BC/TC ratio was higher in Vienna than in Ljubljana (0.39 vs. 0.29), reflecting the different contribution of diesel traffic emissions. The mass median diameters of the submicron size distributions of all major fractions (total mass, TC, BC and SO(4)(2-)) were smaller in Vienna (0.43 microm, 0.41 microm, 0.38 microm and 0.48 microm, respectively) than in Ljubljana (0.55 microm, 0.44 microm, 0.42 microm and 0.60 microm, respectively). Impactor/filter ratios for total mass were 0.79 in Vienna and 0.82 in Ljubljana, while the ratios for BC were 0.56 in Vienna and 0.49 in Ljubljana. An estimation of the mixing state of accumulation mode BC indicated that 33% and 37% of BC, respectively, are mixed externally to the aerosol in the accumulation size range in Vienna and Ljubljana.     

Modeling secondary organic aerosol formation from oxidation of α-pinene, β-pinene, and d-limonene

The biogenic species α-pinene, β-pinene, and d-limonene are among the most abundant monoterpenes emitted globally. They are also important precursors to secondary organic aerosol (SOA) formation in the atmosphere. This study involves the development of proposed oxidation mechanisms for these three species. Semi- and non-volatile oxidation products with the potential to lead to SOA formation are predicted explicitly. Simulation code that describes the gas-phase oxidation mechanisms including reactions that lead to ozone (O₃) formation is coupled to an equilibrium absorptive partitioning code. The coupled model is used to simulate both gas-phase chemistry and SOA formation associated with oxidation of these three species in chamber experiments involving single as well as multiple oxidants. For the partitioning model, required molecular properties of the oxidation products are taken from the literature or estimated based on structural characteristics. The predicted O₃ and SOA concentrations are typically within ±50% of measured values for most of the experiments except for the experiments with low initial hydrocarbon concentrations and the nitrate radical experiments with α-pinene. The developed model will be used to update a gas-phase chemical mechanism and a SOA formation module used in a three-dimensional air quality model.     

Source characterization and identification by real-time single particle mass spectrometry

A Real-Time Single Particle Mass Spectrometer, RSMS-3, was deployed to Wilmington, Delaware to study regional and local contributions to fine and ultra-fine urban particulate matter (PM). Approximately two-thirds of PM₁ consisted of internally mixed secondary aerosol. The remaining one-third was externally mixed including biomass burning (13%), fossil fuel combustion (7%) and various industrial sources (13%). In this last group, particle classes containing specific combinations of transition and/or heavy metals gave wind-rose plots consistent with specific point sources. For example, particles containing V and Ni were detected from different wind directions than those containing V and Fe. Samples from two industrial emission stacks, a steel manufacturing facility 10 km away and a coal-fired electrical power generation facility 5 km away, were analyzed and compared to the ambient data set. In each case, a direct correlation was found: a Pb–Zn–K–Na class for the steel manufacturing facility and an Fe–La/Ce class for the power generation facility. The ambient particle classes showed additional small signals from secondary components indicating atmospheric processing. Ambient particle classes containing only a subset of these elements, such as Zn only, Fe only and Pb–K only, were nonspecific, that is, the wind-rose plots were more diffuse and the particles could not be mapped to individual sources. The merits of stack sampling as an aid to interpreting single particle data sets are discussed.     

Historical estimation of carbonaceous aerosol emissions from biomass open burning in China for the period 1990-2005

Multi-year inventories of carbonaceous aerosol emissions from biomass open burning at a high spatial resolution of 0.5° × 0.5° have been constructed in China using GIS methodology for the period 1990-2005. Black carbon (BC) emissions have increased by 383.03% at an annual average rate of 25.54% from 14.05 Gg in 1990 to 67.87 Gg in 2005; while organic carbon (OC) emissions have increased by 365.43% from 57.37 Gg in 1990 to 267.00 Gg in 2005. Through the estimation period, OC/BC ratio for biomass burning was averagely 4.09, suggesting that it was not the preferred control source from a climatic perspective. Spatial distribution of BC and OC emissions were similar, mainly concentrated in three northeastern provinces, central provinces of Shandong, Jiangsu, Anhui and Henan, and southern provinces of Guangxi, Guangdong, Hunan and Sichuan basin, covering 24.89% of China’s territory, but were responsible for 63.38% and 67.55% of national BC and OC emissions, respectively.