中国三大粮食作物化肥施用特征及环境风险评价

基于中国三大粮食作物化肥施用强度及配方肥用量核算数据,运用化肥施用环境风险评价模型定量分析了2016年中国三大粮食作物化肥施用特征及其环境风险。结果表明:(1)2016年中国三大粮食作物普遍存在化肥施用过量现象,且不同区域之间单质肥料施用过量程度差异显著,其中,小麦和玉米种植单质肥料存在施用过量的空间范围及过量程度整体上要高于水稻。(2)中国三大粮食作物化肥施用环境风险具有显著的空间差异性,且处于相同风险等级的区域呈现出一定的空间邻近性。(3)中国三大粮食作物总化肥环境风险水平整体较低,但内蒙古、新疆和江苏的小麦种植以及内蒙古、甘肃和湖北等地的玉米种植化肥施用环境风险仍达到了中度或重度风险等级,应成为重点关注的区域。针对当前三大粮食作物化肥施用过量现象严重的问题,政府应当加快三大粮食作物配方肥的推广应用,出台政策措施鼓励企业按大配方生产配方肥,并引导企业在适宜地区进行销售,制定补贴政策以提高农民选用配方肥的积极性,开展科学指导和技术服务以提高农户科学施肥能力和认知水平。     

基于Citespace V的城市生态修复研究的可视化分析

为了清晰了解国内外城市生态修复领域的研究现状和未来发展路径,应用Citespace V信息可视化分析软件,对Web of ScienceTM数据库中2000-2017年城市生态修复领域的612篇文献进行了基础知识框架、研究热点、发展趋势的研究,并绘制了网络知识图谱.结果表明:该领域的研究可大致分为4个发展阶段;研究热点主要包括城市生物多样性、城市景观规划与设计、城市生态系统服务等,其中城市生态系统服务突显程度最高,尤其在最近两年该方面研究迅速增多,使其成为主要研究热点.在该领域中美国起步较早且影响力较大,相较而言我国还存在一定差距.今后应在继续增加相关热点问题研究的同时,增加国内与国外相关机构、国内机构间的相互交流与合作.     

利用3S技术动态监测天山草地农业产量及其成因分析

在新疆阜康县大量“天地”资料观测基础上，利用3S(RS、GIS和GPS)技术和生态系统分析方法，对新疆天山草地农业资源进行了系统的动态监测和大面积估产研究。结果表明，该县草地和森林面积1998年比1988年分别下降了17．5％和51．o％，而农业用地面积和沙漠危害面积却分别增加了57．8％和21．2％，实现了利用3s技术系统准确监测新疆阜康县草地农业资源动态变化，其大面积草地遥感估产精度达到75．8％以上。最后，建立了新型PPR估产模型，其估产精度达到81．76％以上，并给出了理论生态成因解释与定量分析结果等。     

1968～2018年洞庭湖江湖连通河道松滋口冲淤变化特征

探究江湖连通河道演变态势是评估重大人类活动事件对江湖关系变化影响的重要环节。以洞庭湖—荆江三口中松滋口河道为研究对象，通过建立其河道长期的水位—流量关系曲线分析其河道的冲淤变化特征，对其河道冲淤变化驱动因素进行分析，并采用实测河道断面资料验证其结果的可靠性。结果表明：水位—流量关系曲线法分析河道地形冲淤演变特征与实测横断面地形资料分析结果一致，松滋口河道同流量下水位下降对应于该时期河道冲刷，同流量下水位上升对应于河道淤积。不同时期松滋口东西分支河道冲淤变化主要驱动因素不同。1968～1981年间，下荆江裁弯引起的河势变化是西支新江口河道冲刷与东支沙道观河道淤积的主要诱因。1981～2003年间，其东西两支河道淤积主要是由于葛洲坝运行后引起的上荆江河道冲刷导致的。2003～2018年间，其河道冲刷主要是由于三峡大坝运行引起的河道水沙比例的大幅改变导致的。     

A fragment constant QSAR model for evaluating the EC50 values of organic chemicals to Daphnia magna.

The quantitative relationship between the median effective concentration (EC50) of organic chemicals to Daphnia magna and the number of molecular fragments was investigated based on experimental EC50 values for 217 chemicals derived from the literature. A fragment constant model was developed based on a multivariate linear regression between the number of fragments and the logarithmically transformed reciprocal values of EC50. Functional correction factors were introduced into the model. The model was verified using an independent set of randomly selected data. The mean residual of the final model was 0.4 log-units. The robustness of the model was discussed based on the results of three jackknife tests.     

三峡库区水土流失特点及其环境危害防治措施探讨

水土流失是三峡库区主要环境问题之一,也是库区产生大量泥沙的根本因素,更是造成库区人民生活贫困的根源。本文就三峡库区水土流失的特点及其环境危害作了分析,提出了相应的防治措施,为水土流失防治工程提供科学依据。     

Community-Based Integrated Watershed Management

1 INTRODUCTIONIn the past, natural resources management initiatives havefocused on large but specific sector projects such as dams,reservoirs for water supply schemes, irrigation systems,crop production, at forestation, etc. Often these projectswere treated as technical and administrative issues ratherthan as a socio-economic and political one. However, thehigh social and environmental cost of such schemes haveled to a change of paradigm since the 1980s towards small-scale community projec…     

可张孔曝气器曝气能耗试验研究

通过试验研究，总结出可张孔曝气阻力损失的影响因素，以优化产品的结构设计参数，降低产品在工程应用中的能耗，获取更好的经济效益。     

Changes in plasma thyroid hormones and cortisol levels in crucian carp (Carassius auratus) exposed to the extracted microcystins

The endocrine response of crucian carp injected intraperitoneally with extracted microcystins (MC) was investigated in this study. Fish were injected intraperitoneally either with 0.75% NaCl (control) and Microcystis extract corresponding to 150 and 600 microg microcystins per kg body weight. The plasma levels of triiodothyronine (T(3)), thyroxine (T(4)), free triiodothyronine (FT(3)), free thyroxine (FT(4)), and cortisol were determined at 0, 1, 3, 12, 24, and 48h post-administration of MC-containing extract. Treated fish displayed abnormal behaviors, such as a startle response and disoriented swimming, as well as changes in ventilation rates. Plasma cortisol concentrations of fish in both dose groups significantly increased after administration of extracted MC and remained high throughout the experiment, which suggested that MC elicited a stress response in treated fish. The profiles of cortisol changes in treated fish appeared to be dose dependent, indicating that fish in the high dose group experienced greater MC-induced disturbance. Mortality occurred after 12h in the high dose group. Plasma levels of T(4), T(3), FT(4), and FT(3) did not vary significantly between the control fish. In contrast to this, fish exposed to MC-containing extract showed significant declines in T(3), FT(4), and FT(3) levels in a dose-dependent manner throughout the experiment. Plasma T(4) levels, however, did not vary significantly in the low dose group, whereas they decreased significantly at 48h post injection in the high dose group. This study demonstrates that administration of microcystins-containing extract causes a stress response and reduces the plasma levels of thyroid hormones in crucian carp. These results illustrate that microcystins exerted potent effects on the endocrine system of crucian carp, through activating their hypothalamus-pituitary- interrenal axis and disturbing thyroid function.