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281.
The impact of reducing industrial emissions of volatile organic compounds (VOCs) on ozone (O3) pollution is of wide concern particularly in highly industrialized megacities. In this study, O3, nitrogen oxides (NOx) and VOCs were measured at an urban site in the Pearl River Delta region during the 2018 Chinese National Day Holidays and two after-holiday periods (one with ozone pollution and another without). O3 pollution occurred throughout the 7-day holidays even industrial emissions of VOCs were passively reduced due to temporary factory shutdowns, and the toluene to benzene ratios dropped from ∼10 during non-holidays to ∼5 during the holidays. Box model (AtChem2-MCM) simulations with the input of observation data revealed that O3 formation was all VOC-limited, and alkenes had the highest relative incremental reactivity (RIR) during the holiday and non-holiday O3 episodes while aromatics had the highest RIR during the non-pollution period. Box model also demonstrated that even aromatics decreased proportionally to levels with near-zero contributions of industrial aromatic solvents, O3 concentrations would only decrease by less than 20% during the holiday and non-holiday O3 episodes and ozone pollution in the periods could not be eliminated. The results imply that controlling emissions of industrial aromatic solvents might be not enough to eliminate O3 pollution in the region, and more attention should be paid to anthropogenic reactive alkenes. Isoprene and formaldehyde were among the top 3 species by RIRs in all the three pollution and non-pollution periods, suggesting substantial contribution to O3 formation from biogenic VOCs. 相似文献
282.
对焙烧炉筒体结构进行有限元建模仿真,考虑热应力、压力和重力对筒体结构受力的影响,计算了焙烧炉关键部位的蠕变疲劳寿命,同时探究进气温度、保温层及对流系数等参数的影响。结果表明:热应力是影响结构强度的关键因素;焙烧炉筒体在许用蠕变变形量为5%的情况下,其使用寿命超过设计寿命;在筒体加热过渡段铺设保温层,降低与外界空气对流和提高进气温度,有利于降低筒体应力。 相似文献
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Jong-Chan Lee Tae-Hyeob Song Sae-Hyun Lee 《Journal of Material Cycles and Waste Management》2012,14(3):193-201
In this study, according to two kinds of test methods, the waste official test (WOT) method and the soil contamination official test (SCOT) method applied to domestic harmful substance analysis by Korean regulation, ten kinds of harmful substance values for two kinds of natural aggregates (crushed stone and sea sand) and three kinds of recycled aggregates (road use aggregate, coarse aggregate and fine aggregate) were analyzed, as well as their alkalinity levels. Through this analysis, it was found that recycled aggregates had a higher harmful substance value than natural aggregates, but were still within the standard values and were safe. The pH levels of natural aggregates and recycled aggregates were measured by grinding the specimens according to the testing methods, and the results indicated that the natural aggregate was below pH 9, while the recycled aggregates were found to have a strong alkalinity of pH 11. The pH measurement of recycled aggregates according to grain size and eluting time indicated that a small grain size yielded an initially high pH value that changed little over eluting time, while aggregates with a large grain size had a relatively low initial pH value, but increased with eluting time. In addition, the pH of recycled aggregates was higher for smaller grain sizes, and the WOT method yielded higher pH levels than the SCOT method. 相似文献
286.
Xiaoping Zhou Xiaoke Wang Lei Tong Hongxing Zhang Fei Lu Feixiang Zheng Peiqiang Hou Wenzhi Song Zhiyun Ouyang 《环境科学学报(英文版)》2012,24(12):2104-2112
The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback of urban lawn in warmed environment. Soil warming effect on net ecosystem exchange (NEE) of carbon dioxide during the transition period from winter to spring was investigated in a temperate urban lawn in Beijing, China. The NEE (negative for uptake) under soil warming treatment (temperature was about 5℃ higher than the ambient treatment as a control) was -0.71 μmol/(m2.sec), the ecosytem was a CO2 sink under soil warming treatment, the lawn ecosystem under the control was a CO2 source (0.13 μmol/(m2.sec)), indicating that the lawn ecosystem would provide a negative feedback to global warming. There was no significant effect of soil warming on nocturnal NEE (i.e., ecosystem respiration), although the soil temperature sensitivity (Q10) of ecosystem respiration under soil warming treatment was 3.86, much lower than that in the control (7.03). The CO2 uptake was significantly increased by soil warming treatment that was attributed to about 100% increase of α (apparent quantum yield) and Amax (maximum rate of photosynthesis). Our results indicated that the response of photosynthesis in urban lawn is much more sensitive to global warming than respiration in the transition period. 相似文献
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建立了大气细粒子中类腐殖质(HULIS)表面活性的动态表征方法,并以华北平原乡村站点冬季大气PM2.5样品为例,对PM2.5中HULIS的表面活性进行表征.HULIS碳质组分(HULIS-C)浓度为2.0~4.6μg C/m3,占水溶性有机碳和总有机碳的比例分别为31%~40%和20%~26%.浓度为88~200mg C/L的HULIS水溶液,其表面张力相对于纯水降低了18%~22%.HULIS-C浓度在低于70mg C/L时表面张力降低显著,在88~320mg C/L之间降低相对缓慢.动态表面张力随着时间变化逐渐降低,在液滴形成后200s以内表面张力下降迅速,之后趋于平缓,说明表面活性分子在液滴中扩散趋于稳定需要一定的时间,该特征时间可能影响表面活性物质在云凝结核活化时的作用.证实了在污染地区的大气PM2.5中含有一定量的表面活性物质,这些物质可能对颗粒物活化为云滴、雾滴过程产生显著影响;表面活性物质的存在可能在外界湿度变化过程中导致颗粒物发生液-液相分离现象,在颗粒物表面形成有机膜,影响活性分子摄取以及半挥发性物质的气-粒分配过程,从而影响大气非均相反应过程. 相似文献
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Noninvasive prenatal diagnosis for Duchenne muscular dystrophy based on the direct haplotype phasing