低温等离子体降解哈隆类物质中的竞争反应

利用低温等离子体技术对哈隆类物质 CF₂ClBr和 CF₃Br进行了降解反应研究 ,发现无氧条件下某些降解产物的量随放电时间不同而出现波动 ,表明降解过程中存在竞争反应 ;而氧气过量条件下不存在竞争反应 ,其主要产物为 CF₂O等 .对低气压下 CF₂ClBr和 CF₃Br在低温等离子体空间中的气相反应机理进行讨论 ,为实现低温等离子体降解污染物提供了理论依据 .     

O(1D)与CF3Cl的反应研究

研究ＣＦ₃Ｃｌ－Ｏ₃体系在２５３．７ｎｍ 紫外光照射下所引发的Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应．Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应最终产物为ＣＦ₂Ｏ、Ｆ₂、Ｃｌ₂,并讨论了Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应机理．研究表明,在本实验条件的２５３．７ｎｍ 紫外光作用下,ＣＦ₃Ｃｌ自身不发生解离,同时Ｏ（³Ｐ）不与ＣＦ₃Ｃｌ发生反应．此外外加气体（氮气、氧气）对Ｏ（¹Ｄ）与ＣＦ₃Ｃｌ的反应有较强的淬灭作用     

Assessing the effect of long-term crop cultivation on distribution of Cd in the root zone

Trace elements such as cadmium (Cd) may be inadvertently added to cropland soils through application of fertilizers, irrigation water, and other amendments. These toxic trace elements pose a potentially threat to soil quality and, through the food chain transfer, to human health. A generalized soil trace element mass balance model that accounts for the interactive processes governing the reactions of trace elements in soils, and consequently removed with crop harvest and leaching out of the soil profile with irrigation water was developed in this research. The model conceptually approximates the mechanisms and kinetics of a real field cropland system. The model was used to evaluate the long-term cultivation on distribution of Cd in California croplands. Under typical California cropping practices, Cd added into the soils accumulated primarily in the plow layer while the Cd content below the plow layer was barely affected. After 100 years of continuous cultivation, the soil Cd content of the plow layer increases from the background level 0.22 mg kg⁻¹ to 0.40 mg kg⁻¹. The accumulation of Cd in the plow layer is in proportion to the external inputs and is affected by the soil and plant characteristics, and management practices. The model can be used to evaluate the environmental fates of other toxic element in soils with case specific parameters.     

夏季城市大气O3浓度影响因素及其相关关系

利用2003年夏季济南市区近地面大气O₃、相关前体物和气象因素等观测数据,研究了O₃浓度的分布特征及时间变化规律,分析了7月份O₃与NO、NO₂和CO等前体物及太阳辐射和气温气象条件的相关性.结果表明,济南市区夏季O₃污染比较严重,观测期间各污染物O₃、NO、NO₂、NO_x和CO浓度都相对较高,昼间O₃与各前体物的浓度呈较好的负相关关系,与太阳辐射具有非常明显的相关性,而与气温的相关性不明显.根据以上分析结果,利用回归分析方法,建立了昼间O₃浓度与前体物、气象因子之间的相关模式,结果表明O₃浓度的计算值与观测值符合性较好.     

机床采购中人机系统安全的层次分析评价

人机系统安全评价是企业机床采购过程中非常重要的一方面.本文对影响机床的人机系统安全的因素进行了分析归类,建立了人机系统安全性评价指标体系,并应用AHP法对人机系统安全性进行了评价.结合企业对各个供应商产品的单个指标的评价得分,得到供应商产品的综合得分,从而辅助企业作出科学合理的采购决策.     

微囊藻毒素在银鲫肠道中的累积及其病理学影响

银鲫(Carassius auratus),杂食性鱼类,是我国淡水主养品种之一。在富营养化湖泊中,它能以有毒微囊藻为主要食物,导致微囊藻毒素(MCs)在其组织中大量累积。为研究MCs在肠道内累积和代谢特征及其对肠道的毒性影响,分别以50和200μg MC-LReq·kg-1剂量的MCs粗提液(主要含MC-RR和MC-LR)对银鲫进行腹腔注射,并在注射后1、3、12、24、48和168 h后取样。MCs的含量用LC-MS和HPLC进行定性和定量测定,结果发现,高低两剂量组银鲫肠中MCs的含量均在注射后1 h达最大值(分别为2.8和181.4 ng·g-1DW),然后随暴露时间的延长迅速下降。相对于毒素的累积,MCs诱导的银鲫肠组织损伤具滞后性,注射后48 h内,高低两剂量组肠道的病理变化呈时间-剂量依赖性的增长,病理特征表现为肠上皮细胞排列紊乱,甚至出现坏死、溶解和脱落,杯状细胞数目显著增多,微绒毛结构破坏并伴随淋巴细胞浸润。实验结果表明,单次染毒后MCs在鲫肠道中迅速累积后降解,并造成时间-剂量依赖性组织损伤,且低剂量组的损伤是可逆的。     

Three-dimensional barricading of a predatory trap reduces predation and enhances prey capture

Animal structures come at material, energetic, time, and expression costs. Some orb-web spiders add three-dimensional barrier structures to their webs, but many do not. Predator protection is considered to be the principal benefit of adding these structures. Accordingly, it remains paradoxical why some orb-web spiders might construct the barriers while others do not. Here, we experimentally determined whether the barrier structure added to the horizontal orb web of the spider Cyrtophora moluccensis deters predators at the cost of reducing the amount of prey captured in the field. We conducted experiments by day and night to assess whether the effects vary with the time of day. We found that the three-dimensional barriers not only offered protection from predatory wasps by day but also enhanced the amount of prey captured by day and night. Moreover, the barrier structure appears particularly useful at catching moths, the largest and most energetically profitable prey that it encounters. We, therefore, concluded that reducing the energetic and time costs associated with producing and depositing extra silk threads is the principal reason why barrier structures are used intermittently among orb-web spiders.     

Study of county-level low-carbon standards in China based on carbon emissions per capita

ABSTRACT

Low-carbon development is an essential measure to combat climate change, and the establishment of low-carbon standards is an important means to achieve low-carbon development. Due to the differences in size and development level among counties of China, the applicability and fairness of county-level low-carbon standards are very important in this country. This study analyzed the trends of county-level carbon emissions in China, defined the peak value of carbon emissions per capita, summarized the characteristics of existing low-carbon standards, and proposed a fair county-level low-carbon standard based on carbon emissions per capita. The results of our analysis suggest that, under the constraints of carbon emissions reduction policies, China’s carbon emissions per capita will tend towards a stable range. Additionally, by referring to predictions results of the peak value of China’s carbon emissions per capita, it was determined that, in low-carbon development targets, China’s county-level carbon emissions per capita should be set within the range of 2–4 tons. Besides setting low-carbon standards, the Chinese government and private enterprises should develop low-carbon technologies as soon as possible and innovate management models to achieve the win–win situation of simultaneous economic growth and carbon emissions reduction.     

镉在北京褐潮土中对玉米幼苗及其根际微生物的毒性效应

通过温室盆栽实验,研究了镉在北京褐潮土中对玉米(品种郑单958)幼苗的毒性效应及其生物富集特性,并通过聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)技术,探讨了镉对玉米根际微生物群落结构的影响。结果表明,高浓度(>100mg·kg-1)镉对玉米幼苗的生长发育有明显的抑制作用,北京褐潮土中镉引起玉米幼苗株高下降1/2的效应浓度(EC50)为654.6mg·kg-1,引起玉米根部和地上部干质量下降1/2的EC50分别为323.6和110.2mg·kg-1,玉米幼苗地上部生物量(干质量)可作为评价重金属生态毒性的适宜终点。玉米幼苗对镉有一定的吸收累积效应,镉在玉米幼苗各组织中的浓度分布为根>茎>叶,其中根部对镉有一定的富集作用(生物富集系数BAF>1)。镉污染可引起玉米根际微生物群落结构发生改变,高浓度(1000mg·kg-1)镉可导致部分微生物种群数量减少甚至完全消失,表明镉污染可对植物幼苗、植物根际微生物以及植物-微生物之间的相互作用造成重要的干扰和威胁。     

Synergistic degradation of pyrene and volatilization of arsenic by cocultures of bacteria and a fungus

The combination of two bacteria (Bacillus sp. PY1 and Sphingomonas sp. PY2) and a fungus (Fusarium sp. PY3), isolated from contaminated soils near a coking plant, were investigated with respect to their capability to degrade pyrene and volatilize arsenic. The results showed that all strains could use pyrene and arsenic as carbon and energy sources in a basal salts medium (BSM), with the combined potential to degrade pyrene and volatilize arsenic. Bacillus sp. PY1, Sphingomonas sp. PY2 and Fusarium sp. PY3 were isolated from the consortium and were shown to degrade pyrene and volatilize arsenic independently and in combination. Fungal-bacterial coculture has shown that the most effective removal of pyrene was 96.0% and volatilized arsenic was 84.1% after incubation in liquid medium after 9 days culture, while bioremediation ability was 87.2% in contaminated soil with 100 mg·kg^-1 pyrene. The highest level of arsenic volatilization amounted to 13.9% of the initial As concentration in contaminated soil after 63 days. Therefore, a synergistic degradation system is the most effective approach to degrade pyrene and remove arsenic in contaminated soil. These findings highlight the role of these strains in the bioremediation of environments contaminated with pyrene and arsenic.