三个苜蓿品种对镉污染的生理生态反应及抗性比较

研究了镉对苜蓿(3个品种)发芽势、发芽率、根长、芽长、根鲜重等形态指标和SOD活性等生理指标的影响,以及镉污染期细胞膜透性的变化情况。探讨了镉胁迫下3个苜蓿品种抗性的差异,结果表明:30mg.L-1 Cd处理,严重抑制胚根、胚芽的增长,且鲜重急剧下降,随Cd处理质量浓度加大,3个品种SOD活性都呈上升趋势,其中多叶苜蓿升幅最大。高Cd处理(50 mg.L-1),3个品种SOD活性均有所下降。重度胁迫下,3个品种相对电导率和地上部Cd含量都增大,且品种间差异显著,相对电导率以多叶苜蓿最小,准格尔苜蓿最大,Cd含量的顺序为准格尔苜蓿>肇东苜蓿>多叶苜蓿。综合评价多叶苜蓿抗性较强,肇东苜蓿次之,准格尔苜蓿抗性较弱。     

Formation of resistance in the Chironomus plumosus to four pesticides over 45 generations

A study was conducted on the Chironomus plumosus larvae to determine initiation of resistance to four pesticides – chlorfenvinphos, chlorpyrifos, chlorpyrifos-methyl, and malathion. First generational LC₅₀ values were well within the threshold value for chironomids based upon the literature. Subsequent LC₅₀ values were observed to increase, indicating a lessening of the toxicity of the pesticides to the chironomid. In the case of chlorfenvinphos, the 96 h LC₅₀ for generations 1–23 was 6 µg L^?1, in generations 3–7 was 8.57 µg L^?1 and 11.14 µg L^?1 for generations 8–9. Generations 10–12 had an LC₅₀ value of 22.58 µg L^?1 and generation 13 had an LC₅₀ value of 35.08 µg L^?1. Generation 14 had an LC₅₀ value of 47.58 µg L^?1. Generations 15–19 and 20–24 had 96 h LC₅₀ values of 60.68 µg L^?1, 72.58 µg L^?1, 85.08 µg L^?1, 97.58 µg L^?1 and 110.08 µg L^?1, respectively. Generations 25, 26 to 30, 31 to 38 and 39 to 45 had 96 h LC₅₀ values of 160.42 µg L^?1, 210.7 µg L^?1, 262.24 µg L^?1 and 274.36 µg L^?1, respectively. The variation between LC₅₀ values was found to be statistically significant. This was observed for most pesticides tested. Larval size and life cycle duration was observed to change from generation to generation with the body size decreasing markedly from 1 to 0.3 cm with life cycle increasing from 7 to 39 days.     

紫花苜蓿对铅污染土壤修复能力及其机理的研究

以10 mmol/L Pb(NO3)2处理紫花苜蓿幼苗10 d,分析了Pb在紫花苜蓿幼苗根、茎、叶中的积累情况,Pb在根表皮细胞中的亚细胞区域化特点,以及Pb在紫花苜蓿体内的主要存在形式。结果表明,Pb在紫花苜蓿幼苗中积累量(M)特点为:M根 >M茎 >M叶。同时X-ray微区分析显示,胞间隙是紫花苜蓿积累Pb浓度最高的部位,细胞壁和液泡次之,胞质中最低。Pb的存在形式分析表明Pb在紫花苜蓿体内主要以难溶的形式存在,另外BSO能够加剧Pb污染对紫花苜蓿幼苗Pn和生长的抑制作用,显示了紫花苜蓿对Pb的耐受与植物络和素的形成有关。这些都表明紫花苜蓿对Pb具有一定的耐受机制,避免其对胞质代谢的毒性。同时紫花苜蓿具有很高的生物量和对Pb较高的富集作用,因此是一种很有利用价值的土壤铅污染修复植物。     

Learning abatement costs: On the dynamics of the optimal regulation of experience goods

We study the introduction of new technologies when their costs are subject to idiosyncratic uncertainty and can only be fully learned through individual experience. We set up a dynamic model of clean experience goods that replace old polluting consumption options and show how optimal regulation evolves over time. In our base setting where social and private learning incentives coincide, the optimal tax on the polluting consumption is increasing over time. We show, however, that if social and private learning incentives diverge because the private discount rate exceeds the social discount rate, it may be optimal to temporarily increase the tax rate beyond net marginal external damages to induce more learning before reducing the tax rate to the steady state level. Alternatively, one could complement the tax with subsidies for first-time users which can be phased out over time. Similar results apply if consumers have biased expectations. We therefore give a rationale for introductory subsidies on new, clean technologies and non-monotonic tax paths from a perspective of consumer learning.     

Determining the optimal mix of federal and contract fire crews: A case study from the Pacific Northwest

Federal land management agencies in the United States are increasingly relying on contract crews as opposed to agency fire crews. Despite this increasing reliance on contractors, there have been no studies to determine what the optimal mix of contract and agency fire crews should be. A mathematical model is presented to address this question and is applied to a case study from the Pacific Northwest. Results show that the optimal number of agency crews is sensitive to assumptions about fire season severity and the availability of alternative work for agency crews on nonsuppression days.     

水功能区划在流域排污权初始分配中的应用——以沙颖河流域为例

排污权交易是治理环境污染问题的有效手段,排污权初始分配则是排污权交易制度实施的基础,在流域水功能区划基础上研究排污权初始分配问题,将有助于流域排污权交易制度的有效实施.结合我国现行行政特征和流域水功能区划成果,以行政单元作为排污权初始分配主体开展排污权初始分配研究.选取沙颍河流域为例,根据淮河水利委员会制定的沙颍河流域水功能区划及COD、氨氮限排总量要求,以COD、氨氮作为排污权初始分配的客体,通过等比例削减方法对沙颍河流域内的行政单元进行了排污权初始分配,得到了流域内各行政单元的COD、氨氮初始排放权,并将分配结果与区域社会经济发展水平等进行了比较研究,研究认为将水功能区划应用于排污权初始分配研究是一种有效的尝试.在此基础上探讨了关于排污权初始分配的政策可行性、初始分配的方法及地方政府定位等几方面问题,目的在于为将来的排污权分配研究工作提供一些思考和建议.     

The optimal use of non-renewable resources: The theory of extraction

The traditional theory of exhaustion is revised to allow for long run capital mobility. This model is extended to include the impact of cumulative environmental damages on the optimal path of resource use. Models and optimal markets are then analyzed for cases where minerals are available over a continuum of quality and where recycling ameliorates inevitable exhaustion of non-renewable resources. Finally, the impact of technological change on long run trends in mineral prices is examined.     

On marketable air-pollution permits: The case for a system of pollution offsets

After examining the properties of several alternative forms of marketable permit systems for the control of air pollution, this paper proposes a system of pollution offsets as the most promising approach. Under the pollution-offset scheme, sources of emissions are free to trade emissions permits subject to the constraint of no violations of the predetermined air-quality standard at any receptor point. The paper shows that the pollution-offset system has the capacity to achieve the predetermined standards of air quality at the minimum aggregate abatement cost, while making comparatively modest demands both on the sources and on the administering agency.     

玉米-苜蓿间作的生态效应

研究地区位于东北农牧交错带东段。在农牧交错地区，粮食生产与饲草生产同等重要，因此将玉米与苜蓿间作，研究了这种间作的生态效应。发现玉米与苜蓿间作，对土壤理化性质有明显改善，表现在土壤有机质质量分数上升，体积质量下降．土壤全氮、全磷、全钾质量分数升高。因此玉米与苜蓿问作在农牧交错地区具有可行性。     

The role of conjugation in the gene-individual-population relationships in increasing eco-exergy

The genotypic and phenotypic processes were incorporated into one system in the gene-individual-population relationships under the framework of Individual based models (IBMs). The gene types addressing different degrees of metabolic efficiency and toxin susceptibility were provided as attributes in the individuals. Subsequently ecological processes such as food competition and movement were allowed concurrently on the 2-D space to determine the suitable species adapted to the system. The integrative gene-individual-population model accordingly responded to gene exchanges between the neighboring individuals through conjugation. At a substantially low level of gene exchange, system heterogeneity increased to produce high levels of eco-exergy, being presented by species diversity and total population size in the system. The issues related to genetic and ecological effects in the integrative gene-individual-population relationships were further discussed.     

Models for the sterile insect release method with the concurrent release of pesticides

Four different models of pest populations under control by the release of sterile individuals are examined to determine whether or not the release of pesticides in conjunction with steriles would further reduce the pest population equilibrium. It is found that single species without interactions with other species would generally have their equilibria reduced more with the release of both sterile individuals and pesticides than with the release of only steriles. As biotic interactions become more important, however, the feasibility of releasing pesticides in a sterile release programme becomes less sure and more dependent on the nature of the population regulation of the species involved. In particular, when predation on the pest species is heavy, the sterile release programme is likely to be hindered by the release of pesticides as well.     

珠江三角洲典型区域蔬菜地土壤中有机氯农药的污染特征——以东莞市为例

近年来珠江三角洲经济迅速发展的同时所带来的土壤有机氯农药污染问题备受关注,着重调查研究了东莞蔬菜地土壤中17种有机氯农药的污染特征.2002年10-12月采集蔬菜地土壤样品37个,利用气相色谱分析有机氯农药的含量.研究结果表明,东莞蔬菜地土壤样品中均检出有机氯,其中DDE与艾氏剂的检出率为100.0%;17种有机氯农药总含量(∑17OCPs)范围为2.47～82.23 ng·g-1,均值为22.53 ng·g-1.含有7个Cl取代基的有机氯农药即七氯与环氧七氯的含量均显著低于其他有机氯农药的含量;尽管东莞市蔬菜地土壤中DDTs的含量明显低于省内外其他地区蔬菜地土壤DDTs含量,但东莞蔬菜地土壤中有机氯农药主要以毒性较强的六氯代有机化合物为主,因此东莞蔬菜地土壤中有机氯农药污染状况不容忽视.     

珠江三角洲土壤中的有机氯农药的分布特征

为确定珠江三角洲土壤中有机氯农药的含量、来源以及组成特点,对珠江三角洲中心地带广州、佛山、东莞城市群的土壤进行了采样、处理以及气象色谱分析,测定了其中有机氯农药的含量:其中,三地土壤中HCHs的含量范围是0.19～42.3,均值4.42 ng·g-1,而且在四种HCHs的单体中β-HCH的含量在三地的土壤中分布最高;三地土壤中DDTs的含量范围是3.58～831,均值82.1 ng·g-1,而DDT/(DDD+DDE)的比值在一些样品中大于2甚至更高,说明近期内仍然存在着DDTs的使用和排放.广州东莞佛山三地土壤中有机氯农药的总量分别为205、46和105 t,构成了一个潜在的南海有机氯农药污染源.     

Exploring the diversity of neem bioactives as eco-benign pesticides: a reappraisal

Biological activity of neem seeds, leaves and bark is well-established as feeding deterrent and growth disrupter against insects and other arthropods. Neem is a valuable natural pesticide with low toxicity for vertebrates. However, it has not yet achieved a prominent place among pesticides due to its unstability. Recent studies have focused on newer formulations like microencapsulation, inclusion complexes, microemulsion, and granular formulations to enhance efficacy shelf life. Several studies have been undertaken on the effects of neem on predator, parasitoids, and other beneficial organisms as well as impact on the environment. Biotechnological interventions have been carried out for mass production of the active molecule. Once stable formulations of the active molecules are developed, the farming community will benefit the most due to the low toxicity and marked efficacy of neem insecticides.     

The mating system of Hanuman langurs: a problem in optimal foraging

Using data from 23 populations of Indian langurs (Presbytis entellus), we show that the proportion of one-male groups is a function of the males’ ability to defend groups of females, as predicted by the monopolisation model of Emlen and Oring (1977). However, we show that in addition to the number of females in the group and their reproductive synchrony, home range size is also a factor, probably because it affects a male’s willingness to search for other groups. These variables in turn are shown to be functions of environmental parameters (rainfall volume and seasonality, and mean ambient temperature) which probably act via the density of resources and refuges in habitats. Received: 3 March 1994 / Accepted after revision: 24 June 1996     

The economics of mutualisms: optimal utilization of mycorrhizal mutualistic partners by plants

Can choice of mutualistic partners and the degree of their utilization determine (1) mutualistic partner coexistence, (2) relative abundance of mutualistic partners, and (3) environment-dependent changes in relative abundance? We investigate these questions in the context of the plant-mycorrhizal fungal mutualism by building a biological market model potentially applicable to other mutualisms as well. We examine the situation where a single plant selectively utilizes member(s) of a group of ectomycorrhizal potential trading partners. Under biologically realistic circumstances, the plant may simultaneously utilize multiple partners, its degree of utilization determining the community structure of the fungi. If utilization of multiple partners is optimal, the marginal cost of acquiring additional nitrogen from every trading partner must be equal while the marginal cost of acquiring it from any unutilized partner must be larger. Because the plant's nitrogen demand is light dependent, the composition of the fungal species among its trading partners changes along light-availability gradients. We discuss the design of an experiment to test the key prediction of our model, the equalization of marginal cost.     

The existence of optimal strategy in the exploitation of limited biocenoses

Optimal strategy in the control of multicomponent biocenoses that are described adequately by an autonomous discrete model has been investigated. It is shown that for any such biocenosis there exists at least one stationary optimal strategy in terms of discounted reward. The optimal strategy is described for communities of competing species, together with the method of its derivation.     

The optimal harvest and management in the models of animal populations

We extended zero-cost optimization model for population of domestic animals. Also the model of hiring of labor in cattle-breeding farm is constructed and investigated.     

Oligopoly meets oligopsony: The case of permits

This paper derives market equilibria (in demand functions and in bidding strategies) between oligopolists and oligopsonists in a market with intermediates and no competition in final markets. To the best of my knowledge, this theme has not been explored, despite two observations: Firstly, the commonly applied framework of non-competitive and competitive fringe firms has implausible properties for the limit of purely strategic players. Secondly, real world cases correspond at least potentially to such strategic interactions, e.g., non-competitive players selling and buying permits (CO₂ and SO₂). The major implications are that these non-competitive markets are characterized by a kind of double marginalization (on the demand and the supply side) resulting in too little trade and wrong price signals.     

The transition from dirty to clean industries: optimal fiscal policy and the environmental Kuznets curve

This paper investigates privately and socially optimal patterns of economic development in a two-sector endogenous growth model with clean and dirty goods. We consider a second-best fiscal policy framework in which distortionary taxes jointly influence economic growth and environmental quality. In this policy setting, three conditions produce an Environmental Kuznets Curve (EKC): (i) dirty output is bounded; (ii) clean output grows endogenously; and (iii) growth in the dirty sector reduces growth in the clean sector. These conditions do not arise with a consumption externality, but can emerge with a production externality. Endogenous labor supply implications are also investigated. Although not necessary for producing an EKC, endogenous labor supply provides additional linkages that produce an EKC under circumstances in which it would otherwise not appear.