Structure of pathways in ecological networks: relationships between length and number

In ecosystems network, structure determines adjacent (direct) and non-adjacent (indirect) pathways over which energy, matter, and information can flow. The more pathways, the more possible ways the conservative substance can move in zero-sum transactions between network nodes that the pathways interconnect, and the more possible non-conservative, nonzero-sum relations can be secondarily derived from these. Structural analysis is a tool we employ, from a family of input–output methods for exploring zero- and nonzero-sum attributes of environmental networks, to count pathways of varying length between network nodes. In this paper, we examine the relationship between pathway length (k) and number (P_k) as determined by system size (n, number of nodes) and extent and pattern of connectance (C). We develop a measure (m_a) of pathway growth in numbers with increasing length, and then normalize this to the maximum rate possible (m_a/m_c) for a given system size. These measures apply to two pathway types—paths, m_a(0) and m_a(0)/m_c(0), which forbid adjacent node repetitions, and walks, m_a(1) and m_a(1)/m_c(1), which allow them. We find that network size has a curvilinear effect on the pathway number versus length relationship, and extent and pattern of connectance are convolved. Values computed for the paths and walks of three ecosystem models (oyster reef, freshwater marsh, and reservoir cove) are used to compare their pathway structure.     

乌江干流中上游水电梯级开发水温累积效应

以乌江流域洪家渡库尾至乌江渡坝下的水电工程干扰典型段为研究区域，利用建坝前后的水温实测资料，采用建坝前天然水温和建坝后下泄水温比较法，对乌江干流梯级水库水温时空分布特征进行分析。研究结果表明：对天然水温改变最大的电站为洪家渡和乌江渡，前者是受水库水温结构自身影响，后者是梯级联合运行的结果；梯级联合运行使库区水温分层有所减弱，随着时间的推移或上游梯级电站的建成，电站下泄水温年变化过程趋于均化，与天然水温的延迟也越加明显；不同的水库水温结构对水温累积效应的影响也各不相同，稳定分层型水库对水温累积具有正效应，混合型水库具有负效应，过渡型水库处于两者之间，体现了梯级电站的水温累积影响，为研究减缓下泄低温水的对策措施提供依据和参考。     

Planning for Biodiversity: the Role of Ecological Impact Assessment

Abstract:  Environmental impact assessment (EIA) is the process of identifying potential environmental effects of proposed development and the required mitigation measures. It is one of the most widely used planning tools today, but its ability to promote biodiversity conservation is largely unexplored. We studied the ecological component of the Israeli EIA system by reviewing a representative sample of 52 environmental impact statements (EISs) produced since 1995 and their corresponding guidelines issued by the Ministry of the Environment. Quality of both EISs and guidelines was determined using a simple scoring approach. Lack of quantitative data, meaningful analyses, and ecosystem perspective was apparent throughout. Many EISs failed to perform field surveys and their qualitative nature hampered meaningful impact prediction. Most EISs concentrated on aesthetic mitigation measures and did not assess their feasibility and likely success. Most of these flaws reflect poor standards rather than true scientific limitations. Guideline quality scores were the most important factor determining the quality of EISs; second was the involvement of an ecological consultant in preparing the EIS. We found a decreasing trend of EIS quality scores over time. Improvements in EIA procedures, particularly in ecological guidelines and the incorporation of ecological consultation, are important for upgrading ecological impact assessment so that the potential of EIA to advance biodiversity conservation can be realized.     

车内空气污染及控制

近年来，人们越来越关注车内空气污染。但人们对车内空气污染的了解甚少。本文就车内空气污染的污染源、污染物、健康影响、治理措施，相关标准等一系列问题，作系统论述。     

Spillover of functionally important organisms between managed and natural habitats

Land-use intensification has led to a landscape mosaic that juxtaposes human-managed and natural areas. In such human-dominated and heterogeneous landscapes, spillover across habitat types, especially in systems that differ in resource availability, may be an important ecological process structuring communities. While there is much evidence for spillover from natural habitats to managed areas, little attention has been given to flow in the opposite direction. This paper synthesizes studies published to date from five functionally important trophic groups, herbivores, pathogens, pollinators, predators, and seed dispersers, and discusses evidence for spillover from managed to natural systems in all five groups. For each of the five focal groups, studies in the natural to managed direction are common, often with multiple review articles on each subject which document dozens of examples. In contrast, the number of studies which examine movement in the managed to natural direction is generally less than five studies per trophic group. These findings suggest that spillover in the managed to natural direction has been largely underestimated. As habitat modification continues, resulting in increasingly fragmented landscapes, the likelihood and size of any spillover effect will only increase.     

北方地区潜流人工湿地冬季保温措施的研究

人工湿地作为一种造价较省,运行成本低的污水处理技术,目前已经得到了广泛的应用.但是在北方地区,人工湿地受到冬季气候影响,无法正常运行,降低了它的使用效率.试验针对北方冬季低温环境下,人工湿地无法正常运行的问题,对3种不同的保温措施进行历时两年的对比试验,通过对TP、TN、NH₄⁺-N和COD等4种主要污染物和人工湿地出水水温的跟踪监测,检验了不同保温措施的效果.试验结果表明:在冬季,使用薄膜法保温措施的处理系统中, COD、TN和NH₄⁺-N的去除率分别为30%~45%、40%~60%和35%~60%,比温棚法和冰封法的出水中污染物去除率高10%~20%.TP在出水中含量波动较大,去除率为19%~70%,伴有磷释放现象,但是在薄膜保温下TP的去除效果也要好于温棚和冰封.经过SPSS 16.0分析,薄膜保温的人工湿地出水水质与冰封和温棚法相比具有显著性差异.在对人工湿地曝气槽和出水口的污水水温进行监测发现,利用薄膜保温的人工湿地出水口水温高于冰封和温棚的水温,进一步证明薄膜保温可以有效提高人工湿地内的温度,为人工湿地正常运行提供了保证.而且薄膜保温措施的操作简便、造价低,适合推广应用.     

大气细颗粒物(PM_(2.5))在环境科学中的研究简述

细颗粒物作为一种重要的大气污染物,其形态与组成非常复杂,本身所具有的毒性和对环境的有害性已日益受到重视。文章对细颗粒物PM2.5在环境科学中的研究进行了概括,提出了自己的一些见解。     

藻华聚集的环境效应:对漂浮植物水葫芦光合作用的影响

利用适应性强、生物量大的水生植物来净化污染水体,已成为目前水体生态修复的一种快捷有效的方法.然而,在夏季蓝藻水华严重聚集的水体,藻华聚集后对水生植物的生理生态影响及其环境效应,尚缺乏系统研究.本研究以水葫芦为代表,模拟在高温阶段(水温WT25℃)、水华严重聚集时,对水葫芦的光合作用的影响进行研究,以揭示蓝藻水华聚集后造成的浅水生态系统中水生植物消亡的深层机制,并为减轻藻华聚集对水生植物的不良影响、充分发挥水生植物的水体净化功能提供理论依据.结果表明,藻华聚集会很快消耗掉水生植物根区内的溶氧,呈现缺氧状态(DO0.2 mg·L-1);植物根区内ORP出现明显下降现象,实验进行1 d后低于-100 m V,实验结束时达-200 m V,水体呈现强还原环境.与对照相比,根区内p H值低0.7个单位.藻华细胞在死亡、分解后释放大量的无机营养盐于水体中,植物根区内的NH+4-N含量比对照实验中高102倍;较高的NH+4-N含量(平均为45.6 mg·L-1)加之缺氧的协迫作用,导致植物机体受到破坏,植物的光合作用能力严重下降.叶片的平均净光合速率仅为对照的0.6倍,实验结束时其光合速率Pn为3.96μmol·(m2·s)-1,而同期对照实验的叶片净光合速率Pn为22.0μmol·(m2·s)-1;叶片蒸腾速率仅为对照的0.55倍,至实验结束时其蒸腾速率为1.38 mmol·(m2·s)-1,同期对照实验的叶片蒸腾速率为7.61 mmol·(m2·s)-1,表明藻华长期的聚集对植物产生了不可逆的伤害作用.在实际生产中,要避免蓝藻的严重堆积和快速消亡,以减轻藻华暴发对植物的伤害,充分发挥植物的水体净化功能.     

电子商务能改善农业生产的环境负效应吗?-来自上海青浦的证据

电子商务在农村农业领域的快速发展带动了农民收入的增加,但是其作用路径和环境效应有待检验.以上海市青浦区为典型案例,利用264份新型农业经营主体的问卷调查数据,采用IV-ordered Probit模型和夏普利值分解法,研究了"电子商务+农业"模式的经济效应和环境效应.结果表明：电子商务的引入具有显著的农民增收效应,但主要以产量扩大型传导机制为主,反而加剧了农业生产的环境负效应.电子商务并非农民增收的关键因素,其贡献率仅为12%;发挥决定性作用的是新技术、新方法的应用带来的效率提升,以及生产规模扩大带来的规模经济效应,相应的夏普利分解贡献了达到31%和25%.这表明当前的"电子商务+农业"模式仍处于初级发展阶段,需要加强相应的规制和引导,实现从产量驱动阶段向质量驱动阶段转型.     

人群的自然和社会属性分类下PM2.5对心血管疾病的影响

为了研究人群在自然属性和社会属性分类下的效应修饰作用,利用2005~2011年北京市大气PM_2.5日均浓度、气象要素及循环系统疾病每日死亡人数数据,根据不同年龄、性别及学历将人群分组,采用时间序列的半参数广义相加模型（GAM）,定量评价大气PM_2.5对居民循环系统疾病死亡人数的影响.单污染物模型和多污染物模型结果表明,PM_2.5为影响循环系统疾病每日死亡人数的主要大气污染物.北京市空气中PM_2.5的浓度每增加10μg/m³,循环系统疾病总死亡人数增加0.50%（95% CI：0.36,0.63）.不同人群的易感程度不同,各人群死亡人数的增加范围为0.23~0.71%,女性、60~74岁人群、文盲人群的健康风险相对较高.在文盲人群中,老年（60+）女性占比为66.2%,为了分离社会属性人群分类中可能存在的自然属性因素干扰,本文去除其中老年、女性这两个混杂因素的影响,文盲人群健康风险仍然大于较高学历的人群.年龄和性别因素叠加在学历因素上,可能加大低学历人群的健康风险,对于这部分叠加了自然因素和社会因素双重敏感性的人群应给与重点关注.