Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intersexual plasticity in aspects of the biology of the mudskipper Periophthalmus barbarus (Gobhdae) in the mangrove swamps of IMO Estuary, Nigeria

Between April 1992 and March 1993,intersexual plasticity in aspects of the biology of the mudskipper,Periophthalmus barbarus was studied.Sec was differentiated on the basis of the genital papillae,it was broader in females than males.Sexually active females were slightly heavier than similarly-sized males.Sex ratio was strongly female-biased.Length-weight relationship of the sexes was isometric.There was no significant difference in the feeding intensity of both sexes;uniformity was also apparent in diet breadth.There was no named sex-based difference in hepatosometic index but condition index was higher in males than females.the uniformity in intersexual plasticity of P.barbarus is consequent upon homogeneity of the mangrove ecosystem,which can only be altered anthropogenically.     

资源科学研究的历史进程

资源科学研究是社会文明发展的一方重要基石。人类-资源关系的演进经历了自然崇拜时期、人本位与技术革命时期和现代协调发展时期三个阶段。真正的资源科学研究缘起于20世纪初期,作为资源科学研究三大支柱的资源地理学、资源生态学和资源经济学发展较快。近二、三十年来的资源科学研究表明,战略化、管理化和数量化是现代资源科学研究的三大趋向。     

密度泛函方法预测二英类化合物(PCDD/Fs)的正辛醇/水分配系数

在B3LYP/6-31G水平上全优化计算了多氯代二苯并一对-二(噁)英和多氯代二苯并呋喃(PCDD/Fs)系列物的分子结构;基于得到的分子结构描述符,依据修正的线性溶解能理论,分别建立了PCDDs和PCDFs的正辛醇/水分配系数的定量结构-性质关系模型(R2分别为0.985和0.966),并用交叉验证法对模型进行了验证(q2分别为0.983和0.936),用t-检验对各变量进行了检验.检验结果表明,模型的预测能力优于AM1法、单苯环氯取代指数法和拓扑量子方法得出的模型.     

Assessment of risk from long term exposure to waterborne pathogens

Disease due to waterborne pathogens, whether in outbreak or endemic form, continues to be a problem in both the developing and the developed world. Control of waterborne disease requires accurate assessment of the pathogen dose-response relation and of likely patterns of exposure. Heretofore, risk assessment of pathogen exposure has been done on the basis of several standard biologically plausible dose-response models. In this paper, the problem of estimating the long-term risk from waterborne pathogens is put into a rigorous mathematical and statistical framework. The implications of the biologic assumptions embedded in the dose-response models (e.g., heterogeneity in susceptibility) are fully considered, as are the likely patterns of long-term exposure (e.g., temporal correlations within individuals and heterogeneity of mean exposures). Two types of long-term risk are described, risk per person-time and risk per individual where the latter is the risk of infection at least once. The effects on these risks of heterogeneity in individuals susceptibilities and mean exposures and of temporal correlations of exposures are described, both theoretically and empirically using a sample of experimental data sets. Because different models with equal plausibility may give very different results in the low-dose range but fit the experimental data equally well, we apply the model uncertainty algorithm of Buckland et al. (1997) on example data sets. Finally, the computational aspects of the general problem, which are often challenging, are discussed along with the conditions under which simplifying approximations may be utilized.     

中国部分自然保护区生物物种数量与面积之间关系的研究

分析了中国部分自然保护区面积与生物物种(动物和植物)之间的关系;其次讨论了动物与植物以及动物与动物物种数量间的关系.结果表明,我国部分自然保护区的面积多数偏小,鸟类、哺乳类、种子植物、爬行类、昆虫和两栖类等与其面积的相关关系依次减弱;其植物种数与鸟类种数的作用影响最大、关系最密切;两栖类与各类动物之间以及鸟类与各类动物之间的物种数目呈显著的相关关系;两栖类与昆虫类为负作用影响;鸟类与两栖类和爬行类以及哺乳类与两栖类为最大的正作用影响.     

我国西部水资源供需关系地区性差异变化研究

利用地理信息系统技术,对我国西部12个省(市、区)按流域进行了划分,结合1980年和1990年水文资料,比较了我国西部各流域两个时段可供水量、需水量、缺水量和缺水率变化,系统分析了西部水资源供需关系变化的地区性差异及其原因,并预测了未来我国西部缺水情况,这些研究为我国西部大开发战略的实施提供了基础性依据。     

邻苯二甲酸酯的摇瓶生物降解规律研究

用好氧活性污泥对 9种邻苯二甲酸酯进行了摇瓶生物降解研究 ,结果表明 ,邻苯二甲酸酯的摇瓶降解速率符合一级动力学 ,速率常数 (kb)与化合物的分子结构之间存在相关关系 ,其表达式为lnkb=0 0 2 6 2x2 - 0 6 6 7x +2 15 2 (r =0 976 ) ;降解半衰期与烷基链之间也存在相关性 ,表达式为t1 2 =0 0 391x2 +0 0 95 3x - 0 0 2 5 9(r=0 972 ) .邻苯二甲酸二甲酯 (DMP)浓度超过 6 0mg·L-1时 ,其自身降解速率下降 ,邻苯二甲酸盐浓度超过 5 0 0mg·L-1时 ,对邻苯二甲酸二乙酯 (DEP)的降解有抑制作用     

城市客运交通系统可持续发展动力学模型

从系统论的观点出发，结合当前城市客运交通的现状，给出了城市客运交通系统所具备的动力学性质和特征。采用了协同学理论方法来分析城市客运交通大系统以及各子系统的问题。基于动力学基本原理建立了一个数学模型，探讨了城市客运交通系统资源开发利用与城市经济可持续发展之间的非线性关系及其调控策略。     

论区际环境关系及其调控

区际环境关系是环境科学理论和实践研究的重要课题，随着生产力的发展，环境作为一种烯缺资源纳入人类的经济生活和社会生活中，由于存在局部环境利益的差异，不同区域的环境利益主体在追求利益最大化的驱动下，势必把环境成本转嫁与其他区域，这就促使原始的纯粹的区际自然关系发生深刻变化，新的区际环境关系发育和建立，文章认为，区际环境关系受社会经济诸多因素的影响，应从经济，法律和行政等多方面着手调控区际环境关系，建立科学，合理，公平的区际环境协作关系，以实现环境资源的集约化使用和生态环境问题的系统整治。