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71.
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Fangfang Sun Dazhi Wen Yuanwen Kuang Jiong Li Jianli Li Weidong Zuo 《环境科学学报(英文版)》2010,22(7):1006-1013
Emissions from industrial activities pose a serious threat to human health and impose the need for monitoring both inorganic and
organic pollutants in industrial areas.We selected Masson pine (Pinus massoniana L.) as potential biomonitor and collected the current
(C) and previous year (C+1) needles from three industrial sites dominated by petrochemical, ceramics manufacturing, and iron and steel
smelting plants and one remote site to determine heavy metals (Cu, Cd, Pb, Zn, Cr, Ni and Co) and polycyclic aromatic hydrocarbons
(PAHs) in unwashed and water-washed needles. Both unwashed and washed C+1 needles showed generally higher concentrations of
heavy metals and PAHs than C needles, although the washed needles more clearly spotlighted the accumulation e ect of PAHs over
exposure time. Water-washing resulted in a significant decrease in needle PAH concentrations with more significant e ects shown in
C needles. By contrast, needle heavy metal concentrations were much less a ected by washing. Although heavy metals and PAHs
might di er in adsorption and uptake strategies, their higher concentrations in the needles at the industrial sites indicated conspicuous
contamination due to industrial emissions there. The PAH distribution patterns in pine needles accorded with the real types of energy
consumption in the study sites and were e ciently used for pinpointing local pollutant sources. 相似文献
74.
两级SBR工艺去除磷、氮及有机物效能分析 总被引:1,自引:0,他引:1
以模拟生活污水为处理对象,在常温条件下,采用对比试验与机制分析方法,研究了两级SBR工艺分级除磷、去除有机物及脱氮的特性,分析了工艺的效能优势.结果表明,通过控制泥龄(除磷级5~7 d,脱氮级约50 d),可以将异养的PAOs与硝化菌分别控制在2个反应器中优势生长,在出水水质更优的情况下,系统的处理效率可比单级SBR提高1倍以上;两级SBR系统可以有效地缓解有机负荷对硝化过程的冲击影响,在进水COD浓度较高的情况下,能够保持其脱氮级(SBS2)具有稳定的硝化速率,且系统的最终出水可以容易并稳定地达到TP≤0.5 mg.L-1的国家标准;另外,两级SBR的脱氮级(SBS2)除具有优势的硝化菌种外,还能培养出适合降解难降解有机物的异养菌,使其好氧硝化结束时COD浓度较单级SBR系统更低. 相似文献
75.
Unraveling the impact of workforce age diversity on labor productivity: The moderating role of firm size and job security 下载免费PDF全文
Previous literature has suggested both positive and negative effects of age diversity on labor productivity: positive because of the potential knowledge complementarities between employees of different ages and negative because of the age‐related value differences that might reduce cohesion and cooperation, hampering firm performance. Using a Belgian sample of 5892 organizational observations (2008–2011), we unraveled these countervailing effects in two ways. First, we built on prior studies to suggest that the effect of age diversity depends on the particular shape of the age distribution: positive when it is heterogeneous (i.e., variety) and negative when it is polarized (i.e., polarization). This was supported by our findings. Second, we explored the moderating impact of two contextual contingencies, firm size and job security. As expected, the positive effect of age variety is reinforced in large firms and in firms where job security is high. Although firm size also emphasizes the negative effect of age polarization on productivity, job security, unexpectedly, does not moderate this relationship. Our study offers a valuable contribution to the literature as it reveals the boundary conditions of the competing implications of age diversity and, thus, allows one to account for the inconclusive findings reported in previous literature. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
76.
卫生填埋是常用的固体废弃物处置方法。部分填埋场对已经封场和暂时不填埋垃圾的区域覆盖高密度聚乙烯膜(HDPE),便于雨水分流、减少垃圾渗滤液产生量。通过在华北地区某城市生活垃圾卫生填埋场设置采样点,监测分析了HDPE覆膜内积聚的甲烷及恶臭物质的浓度和成分,研究在不同季节、填埋时间产生的甲烷及恶臭物质特征。结果表明:填埋场覆膜内甲烷的平均浓度为15.6%;硫化物、胺类以及恶臭浓度分别为153.9 mg/m3,16.0 mg/m3以及4 322 OU。主要的恶臭物质为硫化氢和氨。总挥发性有机物的浓度为0~147.2 mg/m3,苯系物、烷烃和烯烃是挥发性有机物的主要成分。恶臭浓度与硫化物、胺类浓度具有明显的相关性。环境温度、垃圾填埋龄和填埋量对甲烷及恶臭物质的产生与释放有明显影响。夏季甲烷及恶臭浓度分别达到81.2%和20 943 OU,明显高于其他季节。随着垃圾填埋龄和填埋量的增加,恶臭物质的浓度和成分均发生显著变化。 相似文献
77.
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79.
用萃取火焰AAS法测定汽车道旁树叶中的铅含量 总被引:4,自引:0,他引:4
主要介绍了用碘化钾-甲基异丁基甲酮(KI-MIBK)萃取汽车道旁植物叶片中的微量铅,然后用原子吸收分光光度法(AAS)测定,该方法的精密度和准确度均有较满意的结果 相似文献
80.
Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary
metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and
statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and
not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having
higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher
in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the
leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age,
leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing
within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving
this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns
of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual
resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness.
Received 19 February 1999; accepted 28 April 1999. 相似文献