Neutron activation method in the analysis of environmental objects

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Soil and water loss in the Lancang River-Mekong River watershed (in Yunnan section, China) and its control measures

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水泥土桩复合地基桩土应力参数研究

本文首先通过理论分析，认为桩土应力比、桩土荷载分担比等是反映水泥土桩复合地基工作性状的重要参数。然后通过现场试验，研究桩土应力比、桩土荷载分担比随荷载变化的规律。结果认为：随着荷载增加，桩土应力比逐渐减小，当比值达到某一特征值后，不再发生明显变化；桩土应力比、桩土荷载分担比不为常数，其变化是桩土变形协调的结果。最后得出有一定参考价值的结论。     

First-trimester prenatal diagnosis of Sanfilippo C disease

At 10 weeks' gestation, chorionic villus biopsy was obtained from a woman at risk for Sanfilippo type C disease. Acetyl-CoA: α-glucosaminide N-acetyltransferase activity was markedly deficient. The pregnancy was terminated at 12 weeks' gestation and follow-up study on fetal fibroblasts confirmed the diagnosis.     

Enhanced activity of ZnS(111) by N/Cu co-doping:Accelerated degradation of organic pollutants under visible light

High-efficiency photocatalysts are of great significance for the application of photocatalytic technology in water treatment.In this study,N/Cu co-doped ZnS nanosphere photocatalys(N/Cu-ZnS) is synthesized by a hydrothermal method for the first time.After doping,the tex ture of nanosphere becomes loose,the nanometer diameter is reduced,making the specific surface area of catalyst increased from 34.73 to 101.59 m²/g.The characterization results show that more ZnS (111) crystal planes a...     

不同种类有机肥施用对稻田CH4和N2O排放的综合影响

以麦茬稻田为对象,研究基肥施用不同有机肥对稻田CH4和N2O排放的综合影响.结果表明:有机肥施用对稻田CH4和N2O排放的季节变化模式无明显影响,但影响其排放量.与施用化肥(化肥处理)相比,施用菜饼+化肥(菜饼处理)促进CH4和N2O的排放,其季节排放总量分别增加了252%和22%;施用小麦秸秆+化肥(秸秆处理)和牛厩肥+化肥(牛厩肥处理)明显增加CH4排放,增加量分别为250%和45%,同时却减少N2O排放,分别减少18%和21%;施用猪厩肥+化肥(猪厩肥处理)降低CH4和N2O的排放,分别降低4%和18%.对CH4和N2O排放的综合温室效应分析表明,菜饼和秸秆处理的全球增温潜势(GWP)约为化肥处理的2.5倍,牛厩肥和化肥处理基本持平,但施用猪厩肥可减少10%～15%.各处理的GWP从高到低依次为菜饼、秸秆、牛厩肥、化肥和猪厩肥.单位产量的GWP以秸秆处理最高,菜饼次之,牛厩肥比化肥处理略高,猪厩肥处理最低.从本生长季来看,猪厩肥的施用对于实现环境效益与生产效益的协调发展具有一定作用.     

沼泽湿地孔隙水中溶解有机碳、氮浓度季节动态及与甲烷排放的关系

选择三江平原典型的毛果苔草沼泽湿地为研究对象,测定了沼泽湿地孔隙水中水溶性碳、氮浓度、CH4浓度和CH4排放通量,以及相关环境因子;研究了沼泽水中水溶性有机碳、氮浓度变化特征,探讨了沼泽湿地孔隙水中CH4浓度和排放通量季节性变化及发生原因.结果表明,三江平原沼泽湿地土壤孔隙水中DOC浓度有明显的季节变化(p＜0.01).最高值(剖面平均值为95.1 mg·L-1)出现在6月份,9和10月份出现最低值(剖面平均值均为79.3 mg·L-1),剖面上浓集中心位于15～30 cm.孔隙水中NH4 -N和NO-3-N浓度也有明显的季节变化,而DON变化不明显.孔隙水中CH4浓度在剖面上的分布特征与DOC一致,高浓度中心位于20～30 cm.除6月份外,孔隙水甲烷浓度与土壤温度和DOC浓度有显著的正相关关系,与NH4 -N和NO3-N均没有显著相关性.土壤温度和孔隙水中DOC浓度是影响沼泽湿地产CH4能力的重要因素.CH4排放通量与土壤温度和积水深度呈很好的指数关系,与剖面CH4浓度和孔隙水NH4 -N浓度有显著的正相关关系.CH4排放通量与孔隙水DOC浓度相关性不显著.     

应用δ~(13)C值探讨土壤中有机碳的迁移规律

C3 植物与C4 植物具明显的δ13C值差异 ,利用这种特性 ,选取荔波茂兰喀斯特森林边缘处这个C3植物—C4 植物转换生长的地点 ,分别采集森林与农田各三个剖面的土壤样品 ,根据测定其土壤总有机碳、不同粒径及不同比重组分的δ13C值间的相互关系来推导土壤有机碳的若干迁移规律     

Carbon isotope ratios in logged and unlogged boreal forests: Examination of the potential for determining wildlife habitat use

Due to assimilation of recycled CO₂ from litter decomposition and photosynthetic changes in carbon fractionation at low light levels, the foliage at the base of a forest is often more depleted in¹³C compared to that exposed to the atmosphere in either the canopy or in open clearings. This is referred to as the canopy effect. African research has indicated that these habitat differences in foliar ¹³C can be substantial enough to affect the carbon isotope ratios of resident fauna. Previous work documenting a 30-year chronology on moose teeth from Isle Royale National Park indicated a progressive depletion in¹³C and suggested that this could be due to forest regrowth following extensive burning. The present study examined the assumption implicit in this hypothesis that foliar ¹³C varies between open and closed boreal forest sites. I found a marginal canopy effect of 2 ¹³C difference between upper canopy and ground flora for a forest in northwestern Ontario and an average difference of 1.2 in under- and mid-story vegetation between closed forests and open clear-cuts. Because of these small differences, the utility of carbon isotope analysis in quantifying temporally integrated exploitation of deforested habitats will be low for northern boreal locations. In denser forests, such as those in the tropics or western North American where the canopy effect can be expected to be much greater, ¹³C analysis may still offer some promise for determining selection by wildlife of disturbed habitats.     

Environmental aftermath of the radiation accident at Tomsk-7

An analysis is presented of the environmental effects of the most serious radiation accident recorded after Chernobyl, which occurred in the formerly secret town of Tomsk-7 in Siberia, Russia, on 6, April 1993. Fortunately, it appears not to have become a major industrial crisis or disaster. The causes of the accident are described. It is argued that a mixture of both objective and subjective prerequisites, including specific human, organizational, and technological factors, were responsible for the explosion or directly facilitated it. The Tomsk-7 accident's ecological, medical, social, and psychological consequences are discussed.