基于气象分型的大气环境允许排放量测算方法

本文提出一种基于气象条件分型的城市大气环境允许排放量测算方法,该方法基于环境空气质量和颗粒物组分数据,对气象条件进行分污染天气类型的二次转化规律研究,并确定不同天气类型下的迁移扩散系数.基于扩散理论,建立了污染物排放强度、不同天气类型迁移扩散系数和目标控制浓度之间的关系,在特定区域排放布局和排放方式基本不变的前提下,测算不同天气类型达空气质量标准下的一次PM_2.5,PM₁₀,NO_x和SO₂的允许排放量.以沧州市为例,结合空气质量从优到严重污染程度将对应气象要素依次划分为7种天气类型,测算7种天气类型达空气质量目标下的主要污染物允许排放量.基于2018年基准年的排放量,在天气类型7最不利气象条件下,沧州市一次PM_2.5,PM₁₀,NO_x和SO₂排放量削减率应分别在82.62%,81.17%,75.05%和74.54%以上,才能达到空气质量标准.结果表明,不利气象条件下大气环境允许排放量很小,需要更大力度减少污染物排放,才能避免发生重污染天气.     

Forest Taxation and Rotation Age under Private Amenity Valuation: New Results

This paper studies the impact of harvesting, property, and profit taxes on private rotation age in an ongoing rotations model, where the private landowner is interested not only in the present value of harvest revenue, but also in the private amenity services provided by the forest stand. The main finding of the paper is that conventional wisdom about the rotation effects of forest taxes, distilled from the Faustmann model, predominantly ceases to hold. This is because forest taxes distort the relative profitability of timber and amenity production in a way that is sensitive to the precise nature of amenity valuation. Therefore, the design of forest tax policy necessitates good knowledge of the landowner's objective function concerning the type of amenity services.     

碳酸盐岩风化和成土过程的重金属迁移富集机理初探及环境风险评价

为了探究碳酸盐岩在风化和成土过程中重金属元素迁移规律及重金属的富集机理,本次研究以贵州省都匀市及其周边地区寒武纪地层出露的碳酸盐岩风化剖面为研究对象,采用碳酸盐岩酸不溶物的提取试验研究重金属在基岩中的赋存特征,并结合质量平衡法探索重金属的迁移特征,初步讨论了土壤中重金属的富集机制及其环境影响。研究结果表明：碳酸盐岩风化过程中Ca、Mg元素大量淋失所导致的体积和质量的巨大损失,是造成风化土壤重金属相对富集的主要原因;而部分碳酸盐岩风化过程中释放的重金属以多种形式滞留于残积土中,导致土壤中重金属富集程度增加。研究区部分碳酸盐岩风化剖面重金属含量严重超标,其中以Cd和As超标程度最为严重。重金属元素在碳酸盐岩风化剖面中的迁移规律受气候、剖面发育程度、元素地球化学性质和重金属在碳酸盐岩不同矿物相中的分配特征等多重因素控制。综合分析认为碳酸盐岩风化和成土过程中重金属显著富集的特征很可能是喀斯特地区土壤重金属超标的重要驱动机制,建议地方政府及相关部门在规划和发展农业产业时,要高度重视Cd和As超标的风险,加大对喀斯特地区地表径流和地下水重金属污染的监控力度。     

铅锌矿渣中汞的渗滤特性及其在稻田土壤中的迁移转化特征

关于雨水淋溶作用下铅锌矿渣中汞的渗滤特性及其在稻田土壤中的迁移转化特征并不清楚,本研究利用铅锌矿渣和未受污染的稻田土壤构建微宇宙环境系统,探究其相关特性/征。结果表明,渗滤液中汞的浓度随降雨量的增加而逐渐上升,不同降雨量条件下渗滤液中汞的浓度存在显著差异(p<0.05);一级动力学方程和DoseResp模型均能较好地拟合汞的渗滤过程;在矿渣影响下,不同深度稻田土壤中汞的浓度均显著增加,且随时间的推移呈逐渐升高的规律,0～8、8～15和15～20 cm土壤中汞的垂向迁移速率分别为8.8×10^-4～2.2×10^-3、2.3×10^-4～4.1×10^-4和3.0×10^-7～8.1×10^-5 mg/(kg·cm·d);在矿渣影响下,土壤中残渣态汞的比例下降,其余形态汞的比例均出现不同程度上升,说明在铅锌矿渣影响下稻田土壤汞的生态风险升高。研究结果可为铅锌矿区生态环境保护提供研究基础。     

Migration and biological effect of natural heavy radionuclides on plants

A complex radioecological study of technogenic landscapes of southern Yakutia showed that the main factor responsible for their contamination with uranium and radium is radionuclide dispersal by air with products of rock weathering. Coefficients of biological absorption by plants decrease with an increase in the contamination level, which is explained by the fact that strongly fixed forms of uranium and radium prevail in the contaminated areas. In addition, the root barrier plays an important role. Radiation load is mainly determined by background gamma-radiation. The contribution of internal irradiation accounted for by incorporated radionuclides does not exceed 16% and decreases with an increase in the level of soil contamination. Manchurian alder seeds produced under conditions of enhanced background radiation are more viable than those from the control area. It is shown that seed generations of plants growing under conditions of chronic irradiation are highly resistant to the radiation factor.     

劳动力转移、性别差异与农地流转及合约选择

通过构建“劳动力转移-性别差异-农地流转及合约选择”分析框架,分析劳动力转移性别差异背后的行为经济学含义,进而探讨不同性别的劳动力转移对农户农地流转供给决策与合约选择的差异化影响机制。理论研究表明,女性在家庭中起粘结家庭成员的作用,女性劳动力非农就业更能体现家庭的“离农”,因而女性劳动力的非农就业行为对农户农地流转供给决策具有更明显的促进作用;男性是农户家庭在村庄中排他能力的标志,具有不可忽视的农地流转风险规避功能,因而男性劳动力的外出就业距离对农户农地流转的合约选择起决定性作用。利用全国9省(区)4772个农户样本数据进行实证分析,计量结果表明:①女性劳动力非农就业比例每增加10%,农户转出农地面积占承包地面积比例增加1.06%;②男性劳动力县外就业比例每增加10%,农户转出农地时签订关系型合约的可能性增加1.11%;③男性劳动力县外就业比例每增加10%,意愿合约形式为无合同的可能性增加0.63%,意愿合约形式为口头合同的可能性增加0.29%,意愿合约形式为书面合同的可能性减少0.91%。这意味着,为了劳动力流转市场与农地流转市场更流畅地互动,应为农村女性劳动力营造一个更加合适、有利和公平的非农就业环境,这可成为未来农村劳动力就业扶持政策的重要方向。另一方面,促进正式契约与关系型合约的有机衔接,有利于农地流转合约的正式化与规范化,从而为农地流转市场的健康发育提供有力保障。     

A network approach to prioritize conservation efforts for migratory birds

Habitat loss can trigger migration network collapse by isolating migratory bird breeding grounds from nonbreeding grounds. Theoretically, habitat loss can have vastly different impacts depending on the site's importance within the migratory corridor. However, migration-network connectivity and the impacts of site loss are not completely understood. We used GPS tracking data on 4 bird species in the Asian flyways to construct migration networks and proposed a framework for assessing network connectivity for migratory species. We used a node-removal process to identify stopover sites with the highest impact on connectivity. In general, migration networks with fewer stopover sites were more vulnerable to habitat loss. Node removal in order from the highest to lowest degree of habitat loss yielded an increase of network resistance similar to random removal. In contrast, resistance increased more rapidly when removing nodes in order from the highest to lowest betweenness value (quantified by the number of shortest paths passing through the specific node). We quantified the risk of migration network collapse and identified crucial sites by first selecting sites with large contributions to network connectivity and then identifying which of those sites were likely to be removed from the network (i.e., sites with habitat loss). Among these crucial sites, 42% were not designated as protected areas. Setting priorities for site protection should account for a site's position in the migration network, rather than only site-specific characteristics. Our framework for assessing migration-network connectivity enables site prioritization for conservation of migratory species.     

人口年龄结构、人口迁移与东北经济增长

近些年来,中国东北地区经济增速的迅速下滑引发了广泛关注,与此同时,东北地区的人口老龄化与人口流失局面也在加速发展,为探究二者间的联系,本文在梳理文献的基础上,选择从人口年龄结构和人口迁移的视角切入,利用扩展的索洛模型推导了各变量与人均资本、人均产出间的关系。并通过对地级市面板数据的一阶系统广义矩估计研究了人口年龄结构,人口迁移等变量对东北经济增长的影响及经济增长对人口迁移的反作用,利用交叉项分析探讨了人口因素对东北不同经济发展水平地区的差异化影响。实证发现:1劳动年龄人口占比与东北经济增长成正相关,而人口老龄化与人口净迁出均对东北经济增长产生了不利影响;2相较于一般性的人口流动,户籍人口的净迁出对经济增长的不利影响更突出;3人口年龄结构与人口迁移对发达地区和落后地区产生的影响会有所差异;4东北经济增长存在惯性且符合区域增长收敛理论;5投资率与劳动力参与率这两个变量则未能通过显著性检验。6经济增长也对人口迁移产生了一定的反作用。在此基础上,本文针对性地提出了一些建议:1东北地区应及时科学综合地应对人口老龄化,开发老龄人力资源,调整人口政策,平衡地区间养老压力,发展老龄产业;2东北地区应控制人口流失局面,放宽户籍限制,加快国企改革,形成合理的产业结构与制度环境,留住人才。     

三峡水库香溪河库湾拟多甲藻的昼夜垂直迁移特性

2008年4月3日08:00—4日08:00在三峡水库香溪河库湾5个监测点对拟多甲藻(Peridiniopsis sp.)进行了24 h连续监测,以研究拟多甲藻的昼夜垂直迁移特性,并解释拟多甲藻水华表层水体表观颜色昼夜变化的原因. 结果表明:拟多甲藻在12 m水深以上水柱中存在明显的周期性昼夜垂直迁移特性,00:00—16:00拟多甲藻向表层水体迁移并聚集,最大上移速度约为2 m/h;16:00—00:00拟多甲藻向下部水体迁移,最大下移速度约为4 m/h;拟多甲藻的昼夜垂直迁移是导致拟多甲藻水华表层水体表观颜色不断变化的主要原因. 水体中各层叶绿素a质量浓度〔ρ(Chla)〕昼夜变化较大,用单层ρ(Chla)不足以评价藻类水华暴发程度;均深叶绿素a质量浓度〔ρ(A.D. Chla)〕的昼夜变化不大,能够综合表征藻类迁移水柱中藻类的现存量,可以作为河道型水库拟多甲藻水华暴发程度的评价指标.      

The effect of humic substances on Cu migration in the soil profile

Humic substances (HS) are widely used for diverse purposes. The effect of HS on the metal’s status in contaminated soils is contradictory. The aim of this work was to investigate the Cu migration in soils treated with HS. A model field experiment with the addition of Cu (1.243?mg?Cu/kg) and HS Extra® (potassium humate) was performed. The Cu addition resulted in acidification (by 0.7 pH) after 3 months. The major part of the added Cu remained in the upper 7-cm-thick soil layer; 4% reached the lower soil layer, while only 0.1% were removed beyond the profile. The addition of HS mitigated soil acidification increased the content of Cu bound to solid-phase organic substances and abruptly reduced the Cu activity in the soil liquid phase. Simultaneously, the HS addition increased the water-soluble organic substances (WSOS) by four times, including those in the hydrophilic and hydrophobic fractions, resulting in a twofold increase in the content of soluble Cu. Copper complexes with hydrophilic WSOS mainly reached lysimeters, and hydrophobic organic substances were absorbed by the soil. The HS addition to a slightly acidic soil can accelerate the migration of Cu to adjacent environments.