Assessment of Heavy Metal Contamination of Wetland Soils from a Typical Aquatic–Terrestrial Ecotone in Haihe River Basin,North China

Surface soils were collected in the aquatic–terrestrial ecotone (ATE) of Yongnianwa wetland, downstream of Haihe River basin of North China in June of 2007. Samples were subjected to a total digestion technique before they were analyzed for total concentrations of Cr, Cu, Ni, Pb, and Zn to investigate their pollution levels in the ATE. The contamination index, integrated contamination index, geoaccumulation index, toxic units, and sum of toxic units were adopted to assess the heavy metal contamination levels and ecotoxicity, respectively. The results showed all the selected element concentrations in upland soils of the ecotone were relatively higher than those in the lowland soils. No Cr pollution was observed in all soil samples, but almost all samples were slightly polluted by Cu, Ni, Pb, and Zn except for Site 1. The contamination indexes and geoaccumulation indexes consistently presented no contamination for Site 1 and slight contamination for other sites. The ΣTUs increased from lowland to upland, but the whole level of toxicity in this ecotone was relatively low.     

Effect of flying altitude and pulse repetition frequency on laser scanner penetration rate for digital elevation model generation in a tropical forest

In tropical forests, the penetration ability of airborne laser scanning (ALS) may be limited because of highly dense vegetation cover. However, in the typical planning of ALS surveys, the ability of laser pulses to penetrate forests is not considered. Nine round-trip flight lines covering the area of a tropical forest on the northeast side of the Tsengwen Reservoir in Taiwan were designed in this study. Five flight lines flew at altitudes of 1.525, 1.830, 2.135, 2.440, and 2.745 km, and the other four had pulse repetition frequencies (PRFs) of 100, 150, 200, and 250 kHz. The laser penetration index (LPI) is a quantitative index measuring the penetration ability of the ALS and consists of the ratio of the number of laser pulses reaching the forest floor to the total number of laser pulses. The LPI was used to represent the laser penetration rate and investigate the influence of flying altitude and PRF on the LPI. The results showed that as the flying altitude decreased by 1 km, the average LPI increased by 10%, and as the PRF decreased by 50 kHz, the average LPI increased by 2%. The effect of the LPI on digital elevation models (DEMs) was confirmed by visual images obtained by DEMs at five altitudes. The DEM obtained at an altitude of 2.745 km was coarsely textured, whereas that obtained at an altitude of 1.525 km was finely textured. The in-situ height data obtained from the electronic Global Navigation Satellite System (eGNSS) were compared with the data of the ALS-generated DEMs. The results indicated that when the LPI ≥60%, the height difference between the in situ data and DEM data was not prominent. However, when the LPI <60%, the ALS-derived DEM could be higher or lower than the in-situ height; the largest difference between the two was 1.7 m. The LPI of a forest should be considered for ALS survey planning, especially when consistent DEM precision for large tropical forest areas is paramount.     

Environmental Assessments of Trace Metals in Sediments from Dongting Lake, Central China

INTRODUCTIONFresh water lakes are one of the planet’s mosti mportant freshwater resources.They support life invarious forms,develop tourism and provide uniquerecreational opportunities.It is also a good source ofthe provision of drinking-water for local communi-ties.Studies on trace elements in rivers,lakes,andsedi ments(Zhou et al.,2004;Gray et al.,2000;Grosheva et al.,2000;Klavins et al.,2000;Aucoinet al.,1999;Bortoli et al.,1998;Elbaz-Poulichet etal.,1996;Johansson et al.,1995;F r…     

地理市情普查统计分析评价的研究与实现——以台州市救灾避灾资源配置为例

根据台州市地理市情普查生产实践,基于普查成果内容,设计满足区域经济社会发展需求的统计分析评价主题及指标体系;以城市救灾避灾场所资源配置为案例,结合相关数据,利用叠加分析、可达性分析等模型深度挖掘国情信息,统计分析救灾避灾场所的步行可达性与服务范围,对社会民生工程救灾避灾场所的资源配置提出优化的建议。     

白洋淀浮游植物群落及其与环境因子的典范对应分析

在对湖泊生态系统健康评价研究的基础上,提出用营养状态-综合指数法（TSI-CI）对西湖进行生态系统健康评价．首先选用Chl．a、SD、TP和TN四个指标用相关加权指数法进行营养状态评价,再选择物化和生物指标无量纲化处理后计算综合指数进行综合评价．结果表明：西湖生态系统健康状况与营养状态水平的变化趋势是一致的,1—3月健康状况相对较好,7-9月相对较差．该结果客观反映了西湖的实际情况,为西湖水质管理提供科学依据。     

三峡库区特大滑坡灾害防治工程评价方法初探

以三峡库区特大滑坡灾害为研究对象,汇总、分析了库区72处特大滑坡灾害的防治工程措施,总结了三峡库区特大滑坡灾害防治技术的特点。通过对三峡库区特大滑坡灾害防治工程的基本类型与防灾特点的分析,建立了特大滑坡灾害防治措施的评价指标体系,并依照评价指标和标准对滑坡灾害防治工程效果进行分级。     

Assessing effects of “source-sink” landscape on non-point source pollution based on cell units of a small agricultural catchment

Ascertaining the relationship between \"source-sink\" landscape and non-point source(NPS) pollution is crucial for reducing NPS pollution, however, it is not easy to realize this target on cell unit scale. To reveal the relationships between \"sourcesink\" landscape and NPS pollution based on cell units of a small catchment in the Three Gorges Reservoir Region(TGRR), the runoff and nutrient yields were simulated first by rainfall events on a cell unit scale based on the Annualized AGricultural Non-Point Source Pollution Model(AnnAGNPS). Landscape structure and pattern were quantified with \"sourcesink\" landscape indicators based on cell units including landscape area indices and locationweighted landscape indices. The results showed that:the study case of small Wangjiagou catchment highlighted a good prediction capability of runoff and nutrient export by the AnnAGNPS model. Throughout the catchment, the spatial distribution trends of four location-weighted landscape indices were similar to the trends of simulated total nitrogen(TN) and total phosphorus(TP), which highlighted the importance of spatial arrangement of \"source\" and \"sink\" landscape types in a catchment when estimating pollutant loads. Results by Pearson correlation analysis indicated that the location-weighted landscape index provided a more comprehensive account of multiple factors, and can better reflect NPS-related nutrient loss than other landscape indices applied in single-factor analysis. This study provides new findings for applying the \"source-sink\" landscape indices based on cell units in small catchments to explain the effect of \"source-sink\" landscape on nutrient export based on cell unit, and helps improve the understanding of the correlation between \"source-sink\" landscape and NPS pollution.     

基于国内试验数据的钢筋混凝土构件性能指标研究

钢筋混凝土构件的性能指标在性能化抗震设计中具有广泛应用。现有研究成果大多采用国外试验数据库,在国内实际工程结构的应用中面临挑战。因此,文中收集了国内公开发表的132组钢筋混凝土柱和24组钢筋混凝土梁的低周往复荷载试验数据,分析了《建筑抗震韧性评价标准》(GB/T 38591-2020)的转角性能指标与试验转角之间的相对误差。研究发现,《建筑抗震韧性评价标准》部分转角性能指标忽略了关键参数的影响,相对误差较高,各性能指标之间的安全冗余度相差较大。文中对此提出了修正的钢筋混凝土构件转角性能指标,更好地考虑了关键参数的影响,既降低了相对误差,又保证了安全冗余度的一致性,能够更合理地判断构件的损伤状态。