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721.
Yutong Liang Qiaozhi Zha Weihao Wang Long Cui Ka Hei Lui Kin Fai Ho 《Journal of the Air & Waste Management Association (1995)》2017,67(7):797-805
Nitrous acid (HONO) is an important precursor of OH radicals in the atmosphere. In urban areas, emissions from vehicles are the main source of air pollutants, including reactive nitrogen. Previously reported emission ratios of HONO (HONO/NOx) from vehicles were measured in the late 1990s and need to be updated due to the significant changes in emission control technologies. We measured the emission ratio of a fleet of vehicles (38% diesel on average) from March 11 to 21, 2015, in a road tunnel in Hong Kong. The emission ratio of 1.24% (±0.35%) obtained is greater than the commonly adopted 0.8% or 0.3%. The elevated emission ratio is found to be related to the presence of vehicles equipped with diesel particle filters (DPFs). Positive correlation between HONO and black carbon (BC) shows that HONO and BC were emitted together, while the lack of correlation or even anticorrelation between HONO/NOx and BC indicates that the BC-mediated conversion of NO2 to HONO in the dark was insignificant in the immediate vicinity of the emission sources.
Implications: Vehicular emission is a key source for HONO in the urban atmosphere. However, the most commonly used emission ratio HONO/NOx in modeling studies was measured more than 15 years ago. Our tunnel study suggests that a mixed fleet nowadays has a higher emission ratio, possibly because of the diesel particle filter (DPF) retrofit program and the growing share of Euro IV or more advanced diesel vehicles. Our study also provides new insight into the role of black carbon in HONO formation from vehicles. 相似文献
722.
氟虫双酰胺对蚯蚓的生化毒性与细胞毒性研究 总被引:1,自引:0,他引:1
双酰胺类杀虫剂已成为全世界第4大类最常用的杀虫剂,具有非常广阔的应用前景。然而,目前关于双酰胺类杀虫剂生态毒性评估方面的研究还比较少。为探究双酰胺类杀虫剂对非靶标生物的毒性作用,选取赤子爱胜蚓(Eisenia fetida)为受试生物,研究了典型双酰胺类杀虫剂氟虫双酰胺对非靶标动物蚯蚓的生化毒性和细胞毒性以及其在人工土和蚯蚓体内的浓度变化情况。结果表明,氟虫双酰胺在人工土壤中十分稳定,在整个暴露期间氟虫双酰胺的浓度变化不超过20%。氟虫双酰胺在蚯蚓体内的含量随染毒浓度的升高和暴露时间的推移而增加,呈明显的时间和剂量-效应关系;在染毒浓度为0.1和1.0 mg·kg-1的处理组中,氟虫双酰胺未对蚯蚓产生明显的氧化胁迫效应。在染毒浓度为5.0和10.0 mg·kg-1的处理组中,蚯蚓体内活性氧(ROS)含量显著高于其他处理组,过量的ROS诱导蚯蚓体内各种抗氧化酶活性发生异常变化,并在蚯蚓体内造成了脂质过氧化、蛋白质羰基化和DNA损伤。研究表明,当土壤中氟虫双酰胺的浓度为5.0和10.0 mg·kg-1时可能会对蚯蚓产生很高的风险。此外,彗星实验对氟虫双酰胺诱导的氧化胁迫较为敏感,可以作为敏感生物标志物对氟虫双酰胺造成的土壤污染进行预警。 相似文献
723.
Body size variation across environmental gradients has received considerable attention in evolutionary ecology in recent years. In this study, we investigated body sizes and age structure using skeletochronology in male Polypedates megacephalus from five sites with the attitude ranging from 449 to 1300 m. The results showed age at sexual maturity in males was 2 years old, and the longevity was 5 years old except for Changning population of 3 years. Body size was significantly correlated with age within each population except for Changning population. Average age did not differ significantly among populations. Body size of individuals also did not differ across populations when removing the effect of age, which did not follow Bergmann’s rule. 相似文献
724.
介绍了变电站直流系统接地故障产生原因、对设备影响,以及直流接地故障传统查找方法的优缺点,提出一种直流接地故障的新型查找方法。通过采用新型直流接地故障定位仪,可以有效消除故障,确保变电站直流系统安全、可靠运行。 相似文献
725.
Wang Fang Yu Lean Long Junhong Bu Haoyue He Changhua Wu Aiping 《Journal of Material Cycles and Waste Management》2023,25(1):221-234
Journal of Material Cycles and Waste Management - Based on the medical waste quantity and patient data during the corona virus disease 2019 (COVID-19) outbreak in China, this study used... 相似文献
726.
727.
采用LGR-密闭式动态通量箱法对城市绿地生态系统温室气体(CO2、CH4)通量的日变化、季节变化特征及其影响因子等进行了较为系统的研究。城市绿地花草CO2通量有明显的日变化和季节变化特征,白天通量值为负,是CO2的净吸收汇;夜晚为正值,是CO2的净释放源;7:00左右由源转为汇,17:00左右由汇转为源,不同花卉24 h总通量有正负2种结果。冬季草坪作为源的时间延长,而作为汇的时间缩短。光强和温度是影响CO2通量日变化和季节变化的主要因素。城市绿地CH4通量较小,不足以对温室气体总量产生显著影响。从减少温室气体排放的角度对城市绿地花草的选择提出了建议。 相似文献
728.
We compared naturally alkaline streams with limestone lithology to freestone streams with and without acid mine drainage (AMD) to predict benthic macroinvertebrate community recovery from AMD in limestone-treated watersheds. Surrogate-recovered (limestone) and, in many cases, freestone systems had significantly higher macroinvertebrate densities; diversity; taxa richness; Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa; EPT/chironomid ratios; scraper/collector-gatherer ratios; herbivores; collector-filterers; and scrapers. AMD-influenced systems had significantly greater numbers of Diptera and collector-gatherers. An entire trophic level (herbivores) was "restored" in surrogate-recovered streams, which also showed greater trophic specialization. Indicator analysis identified seven taxa (within Crustacea, Diptera, Nematoda, Trichoptera, and Ephemeroptera) as significant indicators of limestone systems and six taxa (within Ephemeroptera, Plecoptera, Tricoptera, Coleoptera, and Mollusca) as significant freestone indicators, all useful as biological indicators of recovery from AMD. 相似文献
729.
Edward R. Long R. Scott Carr James M. Biedenbach Sandra Weakland Valerie Partridge Margaret Dutch 《Environmental monitoring and assessment》2013,185(1):755-775
Data from toxicity tests of the pore water extracted from Puget Sound sediments were compiled from surveys conducted from 1997 to 2009. Tests were performed on 664 samples collected throughout all of the eight monitoring regions in the Sound, an area encompassing 2,294.1 km2. Tests were performed with the gametes of the Pacific purple sea urchin, Strongylocentrotus purpuratus, to measure percent fertilization success as an indicator of relative sediment quality. Data were evaluated to determine the incidence, degree of response, geographic patterns, spatial extent, and temporal changes in toxicity. This is the first survey of this kind and magnitude in Puget Sound. In the initial round of surveys of the eight regions, 40 of 381 samples were toxic for an incidence of 10.5 %. Stations classified as toxic represented an estimated total of 107.1 km2, equivalent to 4.7 % of the total area. Percent sea urchin fertilization ranged from >100 % of the nontoxic, negative controls to 0 %. Toxicity was most prevalent and pervasive in the industrialized harbors and lowest in the deep basins. Conditions were intermediate in deep-water passages, urban bays, and rural bays. A second round of testing in four regions and three selected urban bays was completed 5–10 years following the first round. The incidence and spatial extent of toxicity decreased in two of the regions and two of the bays and increased in the other two regions and the third bay; however, only the latter change was statistically significant. Both the incidence and spatial extent of toxicity were lower in the Sound than in most other US estuaries and marine bays. 相似文献
730.