Carbon dioxide and methane fluxes in the littoral zones of two lakes,east Antarctica

During the summertime of 2007/2008, carbon dioxide (CO₂) and methane (CH₄) fluxes across air–water interface were investigated in the littoral zones of Lake Mochou and Lake Tuanjie, east Antarctica, using a static chamber technique. The mean fluxes of CO₂ and CH₄ were ?70.8 mgCO₂ m^?2 h^?1 and 144.6 μgCH₄ m^?2 h^?1, respectively, in the littoral zone of Lake Mochou; The mean fluxes were ?36.9 mgCO₂ m^?2 h^?1 and 109.8 μgCH₄ m^?2 h^?1, respectively, in the littoral zone of Lake Tuanjie. Their fluxes showed large temporal and spatial dynamics. The CO₂ fluxes showed a significantly negative correlation with daily total radiation (DTR) and a weakly negative correlation with air temperature and water temperature, indicating that sunlight intensity controlled the magnitude of CO₂ fluxes from the open lakes. The CH₄ fluxes significantly correlated with local air temperature, water table and total dissolved solids (TDS), indicating that they were the predominant factors influencing CH₄ fluxes. Summertime CO₂ budgets in the littoral zones of Lake Mochou and Lake Tuanjie were estimated to be ?152.9 gCO₂ m^?2 and ?79.7 gCO₂ m^?2, respectively, and net CH₄ emissions were estimated to be 312.3 mgCH₄ m^?2 and 237.2 mgCH₄ m^?2, respectively. Our results show that shallow, open, alga-rich lakes might be strong summertime CO₂ absorbers and small CH₄ emitters during the open water in coastal Antarctica.     

Ground-level ozone in the Pearl River Delta region: Analysis of data from a recently established regional air quality monitoring network

The ambient air quality monitoring data of 2006 and 2007 from a recently established Pearl River Delta (PRD) regional air quality monitoring network are analyzed to investigate the characteristics of ground-level ozone in the region. Four sites covering urban, suburban, rural and coastal areas are selected as representatives for detailed analysis in this paper. The results show that there are distinct seasonal and diurnal cycles in ground-level ozone across the PRD region. Low ozone concentrations are generally observed in summer, while high O₃ levels are typically found in autumn. The O₃ diurnal variations in the urban areas are larger than those at the rural sites. The O₃ concentrations showed no statistically significant difference between weekend and weekdays in contrast to the findings in many other urban areas in the world. The average ozone concentrations are lower in urban areas compared to the sites outside urban centers. Back trajectories are used to show the major air-mass transport patterns and to examine the changes in ozone from the respective upwind sites to a site in the center of the PRD (Wanqingsha). The results show higher average ozone concentrations at the upwind sites in the continental and coastal air masses, but higher 1 h-max O₃ concentrations (by 8–16 ppbv) at the center PRD site under each of air-mass category, suggesting that the ozone pollution in the PRD region exhibits both regional and super-regional characteristics.     

秦皇岛市土壤侵蚀的特点、原因及保护对策

土壤侵蚀是一种危害严重、分布范围广的生态环境问题,影响人与自然的和谐共存,以及各业生产的可持续发展。通过分析秦皇岛市土壤侵蚀特点、原因,提出综合治理土壤侵蚀的对策和措施,以期为今后该区土壤侵蚀防治与治理提供科学依据。     

Using Si depletion in aerosol to identify the sources of crustal dust in two Chinese megacities

Depletion of Si in transported dust has been recognized for many years. It can be used to distinguish between transported and local dust in cities, although it rarely has been. Here we use the variations of the Si/Al ratio in 15 months of continuous PM_2.5 samples at Beijing (northern China) and Chongqing (southwestern China) to reveal the seasonal patterns of their dust sources. For both cities, peaks of concentration for Si and Al in PM_2.5 corresponded with minima of Si/Al, and could often be linked to pulsed air flow from deserts to the northwest. With significant depletion (up to 80%) and homogeneous distribution at urban and rural sites, Si/Al showed a clear seasonal evolution, which decreased from spring to summer, increased from fall to winter, and collapsed during Chinese Spring Festival, indicating the dominance of transported dust, local fugitive dust and firework influence, respectively. The low ratios implied that desert dust is a common source during spring at Chongqing, whereas its presence during cold season at Beijing was also more frequent than expected. Failing to recognize the depletion of Si may lead to an overestimate of desert dust by 15%–65% when using the average abundance of Al in crust (6%–8%), as in previous studies. The difference in Si/Al ratio between local and transported dust implies that >60% of the dust at Beijing came from outside the city during the springs of 2004–2006. This result can help resolve the contradictory findings on this topic that have been presented earlier.     

Emission factors and particulate matter size distribution of polycyclic aromatic hydrocarbons from residential coal combustions in rural Northern China

Coal consumption is one important contributor to energy production, and is regarded as one of the most important sources of air pollutants that have considerable impacts on human health and climate change. Emissions of polycyclic aromatic hydrocarbons (PAHs) from coal combustion were studied in a typical stove. Emission factors (EFs) of 16 EPA priority PAHs from tested coals ranged from 6.25 ± 1.16 mg kg^?1 (anthracite) to 253 ± 170 mg kg^?1 (bituminous), with NAP and PHE dominated in gaseous and particulate phases, respectively. Size distributions of particulate phase PAHs from tested coals showed that they were mostly associated with particulate matter (PM) with size either between 0.7 and 2.1 μm or less than 0.4 μm (PM_0.4). In the latter category, not only were more PAHs present in PM_0.4, but also contained higher fractions of high molecular weight PAHs. Generally, there were more than 89% of total particulate phase PAHs associated with PM_2.5. Gas-particle partitioning of freshly emitted PAHs from residential coal combustions were thought to be mainly controlled by absorption rather than adsorption, which is similar to those from other sources. Besides, the influence of fuel properties and combustion conditions was further investigated by using stepwise regression analysis, which indicated that almost 57 ± 10% of total variations in PAH EFs can be accounted for by moisture and volatile matter content of coal in residential combustion.     

Degradation kinetics of anthracene by ozone on mineral oxides

To further understand the role of substrates on the heterogeneous reactions of polycyclic aromatic hydrocarbons, the reactions of ozone with anthracene adsorbed on different mineral oxides (SiO₂, α-Al₂O₃ and α-Fe₂O₃) and on Teflon disc were investigated in dark at 20 °C. No reaction between ozone and anthracene on Teflon disc was observed when the ozone concentration was ～1.18 × 10¹⁴ molecules cm^?3. The reactions on mineral oxides exhibited pseudo-first-order kinetics for anthracene loss, and the pseudo-first-order rate constant (k_1,obs) displayed a Langmuir–Hinshelwood dependence on the gas-phase ozone concentration. The adsorption equilibrium constants for ozone (K_O3) on SiO₂-1, SiO₂-2, α-Al₂O₃ and α-Fe₂O₃ were (0.81 ± 0.26) × 10^?15 cm³, (2.83 ± 1.17) × 10^?15 cm³, (2.48 ± 0.77) × 10^?15 cm³ and (1.66 ± 0.45) × 10^?15 cm³, respectively; and the maximum pseudo-first-order rate constant (k_1,max) on these oxides were (0.385 ± 0.058) s^?1, (0.101 ± 0.0138) s^?1, (0.0676 ± 0.0086) s^?1 and (0.0457 ± 0.004) s^?1, respectively. Anthraquinone was identified as the main surface product of anthracene reacted with ozone. Comparison with previous research and the results obtained in this study suggest that the reactivity of anthracene with ozone and the lifetimes of anthracene adsorbed on mineral dust in the atmosphere are determined by the nature of the substrate.     

多孔富铁填料曝气过滤除磷机理研究

采用多孔富铁填料的曝气过滤装置具有优良的除磷性能,理论分析研究了多孔富铁填料的除磷机理,通过铁细菌测定、电镜扫描、红外光谱分析等实验对其除磷机理进行了验证。结果表明,多孔富铁填料除磷为化学除磷过程,铁的形态转化中存在铁细菌的氧化作用,沉淀物以碱式磷酸铁为主。     

废弃轮胎制备中孔炭吸附材料工艺及性能研究

为了解决废弃轮胎造成的资源浪费和环境污染的问题,对以废弃轮胎橡胶为碳的前驱体原料,制备具有高吸附性能中孔炭材料工艺进行了系统的研究。通过XRD、扫描电镜以及比表面积分析,对制备的中孔炭微观结构和性能进行表征,讨论了炭化温度、碱炭比,以及活化温度和活化时间等工艺条件对制备中孔炭的产率、结构和性能的影响。结果表明,通过改变工艺条件制备的中孔炭的孔径分布可以在2~80 nm范围内进行调控。在500℃炭化温度,碱炭比为4∶1,900℃活化1 h的工艺条件下,制备的中孔炭的比表面积为473 m2/g,对甲基橙的最大吸附量达到254 mg/g。     

利用城市污泥堆肥及建筑弃土种植麦冬研究

将污泥堆肥产品分别与建筑弃土按0%、10%、20%、30%、40%和50%(湿重)的比例配制营养土,以麦冬为例进行180 d的栽培实验,分析了营养土对麦冬生长特性、植物体内及栽培土壤中营养学指标和重金属含量的变化规律,并通过模糊综合评价方法选择营养土较佳配制方案。实验结果表明:堆肥比例在50%时麦冬生物量增加率、新生芽数及地表部分比重为最大值,在30%时纺锤体肉质数减少率为最大值;随着营养土中堆肥比例增加,麦冬体内养分含量、重金属积累量随之增加,均在50%时达到最大值;栽培土壤养分越多损失量越多,各指残留率越低,同时全磷、全氮及K含量降低率较有效磷、碱解氮小得多,Cr降低率在5.20%～8.34%之间,Zn降低率在3.27%～17.35%之间;堆肥比例在40%以上的营养土对麦冬生长效果好,但较佳配制方案为堆肥产品占20%。     

利用高炉水淬渣制作多孔吸声材料的研究

为了促进高炉炼铁水淬渣的二次利用,研究了以高炉炼铁水淬渣为原料,以硅微粉或水泥为粘结剂,采用压制成型方法制作的多孔吸声材料的吸声性能及力学性能。结果表明:用颗粒状的高炉炼铁水淬渣制作的多孔吸声材料具有良好的吸声性能,其平均吸声系数可以达到0.70以上;材料的抗压强度可以达到3.0 MPa以上。