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591.
Rufeng LI Chenghong FENG Dongxin WANG Baohua LI Zhenyao SHEN 《Frontiers of Environmental Science & Engineering》2016,10(2):381-389
Successive sediment suspensions often happen in estuary, yet little research has probed into the difference in the release behaviors of organic compounds among different suspensions. This study took polycyclic aromatic hydrocarbons (PAHs) as typical organic contaminants and investigated the release behaviors between two successive suspensions with a particle entrainment simulator (PES). Results showed that successive sediment suspensions lowered the concentration of dissolved PAHs in the overlying water via facilitating the re-adsorption of dissolved PAHs onto the suspended particles. Fast-release and slow-release periods of PAHs were successively observed in the both suspensions. The concentration changes of dissolved PAHs in the second suspension were generally similar with but hysteretic to those in the first suspension. More vigorous desorption and re-absorption of PAHs were induced in the second suspension. Successive sediment suspensions obviously decreased the concentrations of mineral composition and organic matters in the overlying water, which significantly affects multiphase distribution of PAHs. 相似文献
592.
Xiaojing SHEN Junying SUN Xiaoye ZHANG Yangmei ZHANG Lu ZHANG Ruxia FAN 《Frontiers of Environmental Science & Engineering》2016,10(5):5
New particle formation (NPF) event at multi rural sites in China Identifying the characteristics of NPF event Comparing NPF event between clean and polluted conditions Quantifying contribution to the cloud condensation nuclei Implication of climate and air quality Long-term continuous measurements of particle number size distributions with mobility diameter sizes ranging from 3 to 800 nm were performed to study new particle formation (NPF) events at Shangdianzi (SDZ), Mt. Tai (TS), and Lin’an (LAN) stations representing the background atmospheric conditions in the North China Plain (NCP), Central East China (CEC), and Yangtze River Delta (YRD) regions, respectively. The mean formation rate of 3-nm particles was 6.3, 3.7, and 5.8 cm−3·s−1, and the mean particle growth rate was 3.6, 6.0, and 6.2 nm·h−1 at SDZ, TS, and LAN, respectively. The NPF event characteristics at the three sites indicate that there may be a stronger source of low volatile vapors and higher condensational sink of pre-existing particles in the YRD region. The formation rate of NPF events at these sites, as well as the condensation sink, is approximately 10 times higher than some results reported at rural/urban sites in western countries. However, the growth rates appear to be 1–2 times higher. Approximately 12%–17% of all NPF events with nucleated particles grow to a climate-relevant size (>50 nm). These kinds of NPF events were normally observed with higher growth rate than the other NPF cases. Generally, the cloud condensation nuclei (CCN) number concentration can be enhanced by approximately a factor of 2–6 on these event days. The mean value of the enhancement factor is lowest at LAN (2–3) and highest at SDZ (~4). NPF events have also been found to have greater impact on CCN production in China at the regional scale than in the other background sites worldwide. 相似文献
593.
静水条件下,研究了Mn2+与Mn7+对刺参幼参行为和存活的影响,并分析了其在幼参体内的富集状况。结果表明,幼参在0.8 ~ 16 mg/L浓度范围内的Mn2+暴露96 h后死亡率均为0.0%,Mn2+在此浓度范围内无明显的急性毒性作用;但暴露于0.1 ~ 6.5 mg/L Mn7+中时,幼参的死亡率随浓度和暴露时间增加而升高。暴露48 h时,幼参的死亡率与Mn7+的浓度呈极显著正相关(P 0.01),Mn7+浓度高于0.5 mg/L时即对幼参表现出明显的急性毒性作用,其安全浓度(SC)为0.31 mg/L,Mn7+对幼参的急性毒性作用强于Mn2+。随着水体中Mn2+与Mn7+浓度的增加,幼参体内Mn元素含量和累积速率均逐渐升高,但富集系数变化存在较大差异。Mn7+在幼参体内的富集作用强于Mn2+。 相似文献
594.
古夫河着生藻类优势种体积与水质因子的相关性研究 总被引:3,自引:0,他引:3
通过研究长江三峡库区古夫河着生藻类优势种体积的变化,探索影响其体积的主要水质因子,为河流水质评价提供依据.于2010年12月至2012年2月,对古夫河着生藻类和地表水采样11次,共鉴定着生藻类197种,检测水质指标10项.选取Mcnaughton优势度指数(Y)>0.02的着生藻类(共30种)作为优势种并计算体积;利用主成分分析(PCA)分析优势种藻类在不同月份的体积变化.结果显示,硅藻门对冷暖季的变化较为敏感.将水质因子与优势种藻类体积进行典范对应分析(CCA),结果显示水质因子与藻类体积相关性大小为:溶解氧>氨氮>叶绿素a>酸碱度>硝态氮>总磷>水温>总氮>总有机碳>化学需氧量.Monte Carlo显著性检验结果为溶解氧和氨氮对着生藻类体积的影响最大,其次为叶绿素a、酸碱度和硝态氮.硅藻门藻类体积的变化可以判断古夫河水体中溶解氧、氨氮、叶绿素a、酸碱度、硝态氮的含量与变化. 相似文献
595.
本文通过对锅炉的整个运行过程的检验,方面普遍存在的问题,在分析大量文献资料的基础上,术。针对各个环节进行分析,总结了工业锅炉在节能减排结合实际工作经验,提出了一些节能减排的方法和技术。 相似文献
596.
597.
There is growing appreciation of the use of concentrated rural settlement as an effective means of implementing infrastructure projects and helping to achieve sustainable development in rural areas. This occurs in China through the exchange of rural residential land for urban construction. However, this policy has not been effective under normal circumstances (called development‐driven conditions) as frequently farmers are reluctant to accept such an exchange. By contrast, in a time of disaster, such as after the 2008 earthquake in Sichuan Province, China, rural victims have accepted this policy of rural residential land exchange. Employing game theory, this paper identifies the reasons for the different outcomes and it contends that the implementation of concentrated rural settlement practice under disaster‐induced conditions is more effective than its introduction under development‐driven conditions. The results of the analysis indicate that, in China, concentrated rural settlement is feasible in a context of post‐disaster reconstruction. 相似文献
598.
以低温域(0~15 ℃)下黄菖蒲(Iris pseudacorus)、菖蒲(Acorus calamus)和香蒲(Typha orientalis)3种湿地植物为研究对象,分别取其根际土壤测定硝化强度,并采用FISH(荧光原位杂交)技术,考察植物根际AOB(氨氧化细菌)、AOA(氨氧化古菌)的数量变化规律. 结果表明:低温条件下,香蒲根际土壤的硝化强度最高,平均值为1.40 mg/(kg·h),黄菖蒲和菖蒲的平均值均为0.96 mg/(kg·h). 湿地植物根际土壤中的细菌数量(数量级为1010)远高于古菌(数量级为108),其中AOB为优势菌种,3种湿地植物的AOA数量分别约占总古菌数量的46.0%、47.9%和49.7%. 3种湿地植物根际AOB的数量(以湿土计,下同)排序为香蒲(2.57×109 g-1)>黄菖蒲(1.23×109 g-1)≈菖蒲(1.14×109 g-1),AOA的数量(以湿土计)排序为黄菖蒲(2.78×108 g-1)>香蒲(2.57×108 g-1)>菖蒲(1.15×108 g-1). 微生物分布特性和硝化作用效果均表明,不同植物根际氨氧化过程的主要作用微生物具有一定差异,AOA和AOB对于湿地土壤氮转化均具有不可忽视的作用,并与植物本体、土壤硝化过程微环境之间有一定的耦合关系. 相似文献
599.
Ros Gloag Vanina D. Fiorini Juan Carlos Reboreda Alex Kacelnik 《Behavioral ecology and sociobiology》2014,68(4):681-689
Obligate brood parasitic birds, such as cowbirds, evade parental care duties by laying their eggs in the nests of other species. Cowbirds are assumed to avoid laying repeatedly in the same nest so as to prevent intrabrood competition between their offspring. However, because searching for host nests requires time and energy, laying more than one egg per nest might be favoured where hosts are large and can readily rear multiple parasites per brood. Such ‘repeat parasitism’ by females would have important consequences for parasite evolution because young parasites would then incur indirect fitness costs from behaving selfishly. We investigated shiny cowbird (Molothrus bonariensis) parasitism of a large host, the chalk-browed mockingbird (Mimus saturninus), in a population where over 70 % of the parasitized mockingbird nests receive multiple cowbird eggs. We assessed egg maternity directly, using cameras at nests to film the laying of individually-marked females. We also supplemented video data with evidence from egg morphology, after confirming that each female lays eggs of a consistent appearance. From 133 eggs laid, we found that less than 5 % were followed by the same female visiting the nest to lay again or to puncture eggs. Multiple eggs in mockingbird nests were instead the result of different females, with up to eight individuals parasitizing a single brood. Thus, while cowbird chicks regularly share mockingbird nests with conspecifics, these are unlikely to be their maternal siblings. Our results are consistent with shiny cowbird females following a one-egg-per-nest rule, even where hosts can rear multiple parasitic young. 相似文献
600.
Laura Serra Marc Saez Jorge Mateu Diego Varga Pablo Juan Carlos Díaz-Ávalos Håvard Rue 《Environmental and Ecological Statistics》2014,21(3):531-563
Wildfires have become one of the principal environmental problems in the Mediterranean basin. While fire plays an important role in most terrestrial plant ecosystems, the potential hazard that it represents for human lives and property has led to the application of fire exclusion policies that, in the long term, have caused severe damage, mainly due to the increase of fuel loadings in forested areas, in some forest systems. The lack of an easy solution to forest fire management highlights the importance of preventive tasks. The observed spatio-temporal pattern of wildfire occurrences may be idealized as a realization of some stochastic process. In particular, we may use a space–time point pattern approach for the analysis and inference process. We studied wildfires in Catalonia, a region in the north-east of the Iberian Peninsula, and we analyzed the spatio-temporal patterns produced by those wildfire incidences by considering the influence of covariates on trends in the intensity of wildfire locations. A total of 3,166 wildfires from 1994–2008 have been recorded. We specified spatio-temporal log-Gaussian Cox process models. Models were estimated using Bayesian inference for Gaussian Markov Random Field through the integrated nested Laplace approximation algorithm. The results of our analysis have provided statistical evidence that areas closer to humans have more human induced wildfires, areas farther have more naturally occurring wildfires. We believe the methods presented in this paper may contribute to the prevention and management of those wildfires which are not random in space or time. 相似文献