Application of adaptive cluster sampling to low-density populations of freshwater mussels

Freshwater mussels appear to be promising candidates for adaptive cluster sampling because they are benthic macroinvertebrates that cluster spatially and are frequently found at low densities. We applied adaptive cluster sampling to estimate density of freshwater mussels at 24 sites along the Cacapon River, WV, where a preliminary timed search indicated that mussels were present at low density. Adaptive cluster sampling increased yield of individual mussels and detection of uncommon species; however, it did not improve precision of density estimates. Because finding uncommon species, collecting individuals of those species, and estimating their densities are important conservation activities, additional research is warranted on application of adaptive cluster sampling to freshwater mussels. However, at this time we do not recommend routine application of adaptive cluster sampling to freshwater mussel populations. The ultimate, and currently unanswered, question is how to tell when adaptive cluster sampling should be used, i.e., when is a population sufficiently rare and clustered for adaptive cluster sampling to be efficient and practical? A cost-effective procedure needs to be developed to identify biological populations for which adaptive cluster sampling is appropriate.     

模拟酸雨对土柱中稀土元素迁移的影响

模拟研究酸雨对土柱中稀土元素迁移的影响.结果表明,在雨水、酸雨淋溶下,对照组红壤土柱中所含稀土元素有向下迁移的趋势,并且随淋溶液pH值的降低,稀土元素向下迁移的能力增加.外源稀土迁移量的大小顺序为;Ce>La>Nd>Pr,其顺序与各稀土元素在稀土微肥中含量大小的顺序相同.表明外源稀土的迁移性与外源稀土的总量密切相关.外源稀土在土柱中的含量随着红壤深度的增加而减少,稀土元素主要在土柱中第一、二层持留;随着淋溶液酸度的下降,稀土元素向下迁移的能力增加.     

Toxic metals status in human blood and breast milk samples in an integrated steel plant environment in Central India

Owing to its unique nutritional and immunological characteristics, human milk is the most important food source for infants. Breast milk can, however, also be a pathway of maternal excretion of toxic elements. Selected toxic elements (As, Pb, Mn,a Hg and Cd) were determined in human breast milk and blood samples obtained from 120 subjects related to an integrated steel plant environment located in central India. Samples of breast milk and blood from subjects living outside the steel plant environment were also analyzed for comparative study. Higher levels of these toxic elements were found in blood samples as compared to breast milk samples. Plant workers showed the higher presence of these metals in their breast milk and blood samples compared to the residents of the area and the subjects living outside the industrial environment, respectively. Mn, Pb and Hg have shown a higher tendency to associate with blood and breast milk than As and Cd. The order of occurrence of these metals in blood and milk samples thus found is Mn > Pb > Hg > As > Cd.     

人地协同论：可持续发展模型构建的基础

人地协同论是在陆地系统科学、非线性系统理论基础上建立起来的关于可持续发展的一个数理模型,它以社会与自然的交互作用、交界面性质及其演化规律为研究对象。本文根据系统生态学理论,提出了关于可持续生存的数学定义。     

复合螯合剂/活性碳分离富集和ICP—AES同时测定水样中痕量元素

本文提出将复合螯合剂（NaDDTC／8—Oxin）饱和吸附于活性碳上作为吸附材料．分离富集和ICP—AES同时测定水中痕量金属元素的方法。用ICP—AES研究了该吸附材料对某些痕量元素的吸附和解吸性能；考察了共存元素的影响。方法应用于湖水中Fe、Cu、Mn、Y和Sc的测定，检出限为ng／ml级，RSD为1．9％～4．4％，加入回收率81％～101％间，试样分析结果满意。     

藏北高原自然资源的利用与保护

藏北高原面积约60万km²,海拔在4500m以上,为青藏高原的主体。其气候寒冷干燥,人迹稀少,以高寒草原为主的生态系统基本保存完好,其天然草地辽阔,各类可利用草地面积占土地总面积53％,为西藏最大牧区,适宜发展地毯毛羊--藏绵羊。这里栖居着许多青藏高原特有的国家一、二类保护动物及有一定经济价值动物资源。高原上湖泊众多,湖泊面积占全国湖泊总面积的1/4以上。其中许多盐湖盛产有工业开采价值的食盐、天然碱及硼、锂、钾等重要稀有元素,为我国主要矿盐产地和远景开发区。目前因草地生态脆弱和利用不当,已有4％草地退化,沙地面积扩大,野生动物栖居范围也趋缩小;少数盐矿产地环境有所污染,盐湖资源浪费较大。所以适度利用天然草地、保护野生动物和综合开发盐湖资源,防止自然生态环境的恶化乃是开发藏北高原生物矿产资源的重要战略措施。     

施灰田土壤及所产蔬菜铀、钍和钾、钼、镁、锌含量变化及影响评价

U和Th是放射性元素,K、Fe、Mo、Mg和Zn是植物生长需要的必要营养元素。粉煤灰中U、Th、Fe和Mo的含量略高于空白土壤中Fe和Mo的含量,K、Mg和Zn的含量低于空白土壤中K、Mg和Zn的含量。掺施粉煤灰并没有引起施灰土壤及所产蔬菜中各元素含量的明显变化。与国家土壤环境质量标准及食品、卫生标准的限值相比,施灰土壤及所产蔬菜的U、Th、K、Fe、Mo、Mg和Zn的含量均在正常范围内波动。     

La2O3-CeO2/γ-Al2O3催化剂还原脱硫耐氧特性及其反应机理研究

用浸渍法制备了一系列稀土催化剂,研究了其催化CO还原SO2为单质硫的耐氧特性及影响其耐氧性能的主要因素,运用XRD技术分析了催化剂物相的变化及脱硫产物成分.结果表明,12% La2O3-8% CeO2/γ-Al2O3复组分催化剂比其他La2O3-CeO2/γ-Al2O3催化剂具有更好的耐氧性能;脱硫温度、催化剂用量、SO2与CO的摩尔比等对催化剂的耐氧性能均有明显的影响.最后,探讨了稀土催化剂脱硫机理,并分析在有O2条件下,引起脱硫率下降的原因是反应过程中O2与CO、S发生了竞争性反应.     

负载氧化镧的活性炭还原NO的研究

稀土金属具有一些特殊的性能,这使得其对碳质材料还原NO的反应可能表现出特殊的催化效果,而此方面的研究没有报道.为了研究稀土金属对活性炭还原NO反应的催化效果,采用浸渍法制备了负载氧化镧的活性炭颗粒(La/C),并在无氧的固定床反应器中进行了程序升温反应和等温反应,考察了气体流量、NO的入口浓度、反应温度和氧化镧负载量对反应活性的影响,同时对反应机理和动力学进行了初步探讨.研究结果表明负载氧化镧的活性炭还原NO的反应是一级反应.由于炭表面3%(质量分数)的氧化镧的存在,C-NO反应的起始反应温度从500 ℃降低到300 ℃,反应活性大大提高,反应活化能从88.95 kJ/mol降低到51.05 kJ/mol.氧化镧的负载量对反应活性有重要影响,但负载量的大量增加对反应活性的提高效果甚微,最佳负载量为1.5%.La/C体系在反应中较稳定,而反应温度的升高对其稳定性不利.     

Trace elements, organochlorines, polycyclic aromatic hydrocarbons, dioxins, and furans in lesser scaup wintering on the Indiana Harbor Canal

During the winter of 1993-94, male lesser scaup (Aythya affinis) were collected on the heavily polluted Indiana Harbor Canal (IHC), East Chicago, IN, USA, and examined for tissue contaminant levels. Lesser scaup collected on the IHC had higher concentrations of cadmium (Cd), mercury (Hg), selenium (Se), polychlorinated biphenyls (PCBs), selected organchlorine pesticides, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polycyclic aromatic hydrocarbons, and aliphatic hydrocarbons than reference birds. Of the scaup collected on the IHC, 44% had Cd concentrations in the liver considered above background for freshwater waterfowl (>3 microg/g dry wt.), 50% had Se concentrations in the liver above a level possibly harmful to the health of young and adult birds (>33 microg/g dry wt.), and 88% of the scaup carcasses exceeded the PCB human consumption guidelines for edible poultry in the USA (>3.0 microg/g lipid wt.). The ratio of pristane:n-heptadecane concentrations in 47% of lesser scaup collected on IHC was elevated above 1.0, which is indicative of chronic exposure to petroleum hydrocarbons.