重庆三峡库区农村生活污水排放特征及影响因素分析

为了解重庆三峡库区农村生活污水排放特征,正确评价农村生活污染状况,选取重庆三峡库区3个行政区中不同经济收入水平、有无下水设施的18户典型农户为监测对象,对其生活污水日产生量、pH、COD、TP、TN、TAN等6项指标进行了连续12月的跟踪监测。结果表明,18户对象农户生活污水人均日产生量、pH、COD、TP、TN、TAN等指标的平均水平分别为：15.22 L·cap-1·d-1、6.67、838.93 mg·L-1、4.19 mg·L-1、53.60 mg·L-1、13.39 mg·L-1,具有人均污水日产生量明显低于而各特征指标的浓度明显高于城镇生活污水的特点;COD、TP、TN、TAN浓度随季节的变化表现出夏季浓度较低,冬季浓度较高的规律,且COD、TP、TN、TAN浓度之间具有显著的正相关性。此外,利用SPSS软件对影响农村生活污水排放特性的地域、季节、农户收入水平和有无下水设施等因素进行了分析,其结果显示：农村生活污水人均日产生量的主要影响因素为地域,COD的主要影响因素为地域、收入水平和季节,TP的主要影响因素为地域、有无下水, TN和TAN的主要影响因素为季节。     

三峡库区传统耕作措施水土保持机理研究

通过大量野外勘查、测量数据,说明了传统耕作措施的规律性及其坡长与坡度特征参数,同时将物理过程侵蚀模型(WEPP)模拟结果与实测数据进行对比分析,主要从坡长因子的角度阐明了传统耕作措施的水土保持作用机理。研究结果表明,实测的5°~10°、10°~15°、15°~20°、20°~25°、25°~30°坡面对应的坡长分别为7~10 m、5~7 m、4~6m、3~5 m、3~4 m,与同一坡度条件下WEPP模拟的坡面侵蚀发生的突增拐点值比较接近;传统耕作措施通过缩短坡长来分散坡面径流,阻止细股流的形成,从而有效防止了坡耕地中主要的侵蚀类型——细沟侵蚀。     

三峡库区典型小流域非点源氮磷污染的来源与负荷

选择三峡库区典型小流域——忠县石宝镇石盘丘小流域,通过对其2007—2009年主要土地利用类型降雨径流中氮磷流失形态与含量进行连续监测,研究三峡库区非点源氮磷污染的来源与负荷。结果表明,三峡库区非点源氮磷污染的来源主要是居民点、柑橘果园和坡耕地,三者累计贡献了76%以上的小流域氮磷污染负荷,因此非点源污染控制的关键是拦截居民点、柑橘果园和坡耕地的暴雨径流。水稻田作为三峡库区主要的农耕地,对径流、泥沙和养分具有显著的截留和净化作用,对来自居民点的氮磷去除效率都在56%~98%之间,因此水稻田合理管理与化肥高效利用是三峡库区非点源污染负荷减控的重要途径。     

小流域水土流失治理优先度的评价与应用

中国水土流失防治任务仍然繁重,有计划分批次实施水土流失治理是现阶段条件下的必然选择,优先治理小流域识别是其首要解决的一项基础工作,然而目前相关成果较为缺乏,难以支撑小流域水土流失治理智能决策和精准施策。在当前大力推进智慧水土保持背景下,积极探索优先治理小流域识别方法非常迫切,对于科学、合理、高效促进水土流失治理工作具有重要意义。该研究立足于小流域自然禀赋条件,以中国水土流失重点区域——三峡库区秭归县为例,坚持科学性和可操作性相结合原则,以水土流失“减量和降级”双重目标和治理效益最大化需求为导向,综合水土流失面积和土壤侵蚀强度两个维度,提出小流域水土流失治理优先度定义及定量评价方法,为识别优先治理小流域提供科学依据和技术支撑。结果显示,秭归县2021年现状水土保持率为69.12%,远期（2050年）水土保持率为81.74%,总体提升12.62个百分点。秭归县2021年全域土壤侵蚀模数现状为758.50 t/(km²·a),最小可能土壤侵蚀模数为408.71 t/(km²·a),总体下降比例达46%。秭归县大部分区域均具有较大的水土保持率提升潜力和土壤侵蚀控制度,可完全治理和可降级的水土流失地块分布较为广泛,尤其在县域中西部的小流域存在较大的水土流失面积消减和土壤侵蚀强度降级空间。秭归县各小流域水土流失治理优先度的空间分布总体呈现中部高,东部和南部相对较低的分布格局,全县治理优先度大于0.6的小流域占总全县小流域的11.76%。通过典型县应用,该研究提出的小流域治理优先度涵盖了水土流失面积和土壤侵蚀强度两个维度,能更为全面满足小流域水土流失“减量和降级”双重目标和和治理效益最大化需求,直观反映了水土流失面积消减空间和土壤侵蚀强度降级空间的目标和相对大小,对支撑小流域治理决策更加准确、科学,治理优先度评价方法不仅可行,且易操作。     

三峡库区生态空间脆弱性时空演变特征

探讨生态空间脆弱性时空分异特征,有助于客观识别区域生态环境的敏感程度和自我恢复能力,并为国土空间规划提供依据。基于VSD模型构建三峡库区生态空间脆弱性分析框架,从空间暴露度、空间敏感性和空间适应力分析2005—2018年三峡库区生态空间脆弱性的时空分异特征及规律。结果表明：(1)三峡库区生态空间脆弱性的3个维度均具有显著的空间分布特征和时间演变规律。生态空间暴露度呈现以重庆的主城区(平均为0.355)和渝东北的万州区(0.416)为双核心向四周逐渐减弱的分布特征;由2005年的0.235 6持续增至2018年的0.269 1。生态空间敏感性呈现“东北高西南低”的分布特征,渝东北的巫溪县敏感性最强为0.691,渝西南的北碚区最低为0.296;由2005年的0.360 7持续增至2018年的0.437 4。生态空间适应力呈现“两端高,中间低”的分布特征,以重庆主城区(平均为0.634)和湖北夷陵区(0.613)为双核心向四周增强;由2005年的0.518 4减至2010年0.457 4后增至2018年的0.571。(2)三峡库区生态空间极度脆弱区主要分布在库区西南地区的重庆市主城区域(平均...     

The influencing factors of N2O emission and denitrification in the soil of water-level-fluctuation zone in the Three Gorges Reservoir area

In order to study the influences of water filled pore space (WFPS), temperature, the addition of nitrate (NO -3) and carbon source on N2O emission and denitrification in the soil of water-level-fluctuation zone in the Three Gorges Reservoir area, C2H2 in hibition incubation experiments are applied. Results from experiments in laboratory and in situ field are analyzed. Results show that the WFPS is a main factor determining N2O emission and denitrification. Denitrification rate increases while the WFPS increases, and the maximum denitrification rate and the maximum N2O emission rate appear when the WFPS is 100% and 60%, respectively. In addition, while the temperature is between 10 ℃ and 40 ℃, the increase of temperature contributes to the increase of the N2O emission and denitrification rates. Furthermore, it is found that the N2O emission and denitrification rates are significantly and positively correlated with temperature. The addition of carbon source could increase denitrification performance in soil. However, the addition of nitrate has a negative impact on the denitrification performance, because nitrogen source is not the main factor determining denitrification performance and excessive nitrate could inhibit the denitrification in these experiments. The addition of glucose, which is a carbon source easily be utilized by denitrifying bacteria, could significantly increase the denitrification rate in soil, and the maximum denitrification rate takes place while the carbon content in per kilogram soil is 240 mg.     

桃源水库生态环境保护利用建议

通过对广西南宁桃源水库生态环境的现状的分析,提出了有针对性的生态保护和利用的措施与建议。     

Life Histories of Frogs in the Namib Desert

Four anuran taxa inhabit the central Namib: Xenopus laevis, Tomopterna delalandei cryptotis, Phrynomerus annectens and Bufo vertebrate hoeschi. Xenopus is confined to permanent pools in the Kuiseb river canyon. Tomopterna extends further into the Namib, but is restricted to the Kuiseb river bed. The Kuiseb is normally dry, receiving water only briefly (as floods) during the rainy season. These floods are responsible for moving adults and larvae. Phrynomerus and Bufo occur on granite inselbergs. The inselbergs provide shelter mainly in the form of cracks under granite exfoliations. Large runoff surfaces collect the low rainfall (25 mm per year) in depressions in which the frogs breed. Phrynomerus is only active at night; males are aggressive towards one another; oviposition takes place in deep pools and development takes at least eight weeks. Bufo is active during the heat of the day; oviposition takes place in warm shallow pools; development takes about three weeks.     

基于LUCC的生态服务价值变化研究

土地利用/覆盖变化(Land-Use and Land-Cover Change, LUCC)是影响土地生态系统服务价值的重要因素.该研究以三峡库区腹心地带的万州区1990,1995,2000,2005,2010和2015年6期TM影像为基础,通过图像解译,分析了万州区各地类变化,估算了研究期间各地类生态系统服务价值.结果表明, 1) 1990-2015年间,万州区耕地和草地面积分别减少了9 389.7 hm~2和3 695.85 hm~2;林地、水域和建设用地的面积分别增加了4 063.14,2 716.83和6 304.86 hm~2; 2) 1990-2015年万州区生态服务价值由18.82亿元增至19.41亿元,增加了3.10%;林地与万州区生态总价值呈相同的"上升—下降—上升—下降"趋势,耕地生态服务价值下降,草地先增后减,水域则相反; 3)万州区生态服务价值区域差异有统计学意义,空间上以长江为界呈现东多西少的分布格局; 4) 1990-2015年间,万州区各地类各年份生态系统服务价值敏感性指数均小于1,表明万州区生态服务价值对其系数缺乏弹性.     

Contamination history of suspended river sediments accumulated in oxbow lakes over the last 25 years

Background, aims, and scope  Embankment of meandering river systems in many industrial areas results in the formation of artificial oxbow lakes that may act as perennial or intermittent traps for river sediments. Their deposits can be dated using a combination of historical and stratigraphic data, providing a good means to study historical records of contamination transported by rivers. Contamination history over the last few decades is of special significance for Central and Eastern Europe as it can reflect high pollutant levels in the second half of the twentieth century and the subsequent improvement after the fall of the Iron Curtain. The purpose of this study was to investigate recent sediments of an oxbow lake of the Morava River, Czech Republic, their stratigraphic records, sediment architecture, and history of contamination. Materials and methods  Seven ground-penetrating radar (GPR) profiles and three sediment cores up to 4 m deep were studied. The stratigraphy of the cores was inferred from visible-light spectrophotometry, X-ray radiography, grain size analysis, and semiquantitative modal analysis of sandy fractions. The sediments were dated using the ¹³⁷Cs mass activity and combinations of stratigraphic and historical data. The cores were sampled for concentrations of heavy metals and persistent organic pollutants. Wet sampled, lyophilized, and sieved sediments were extracted and analyzed for heavy metals by inductively coupled plasma mass spectrometry (ICP-MS) of aqua regia leachate and for persistent organic pollutants by gas chromatography (GC-ECD and GC-MS). Results  Three distinct sedimentary sequences (S1, S2, and S3) were identified. The basal sequence S1 represents river channel sediments deposited before the formation of the oxbow lake, most likely before the 1930s. The boundary between the S1 and S2 sequence correlates with the level of sediment dredging from 1981 evidenced from historical data. The overlying sequences S2 and S3 represent a postdredging sediment wedge, which progrades into the lake. ¹³⁷Cs dating revealed a distinct Chernobyl 1986 peak at ∼150 cm depth inferring sedimentation rates up to 7.7 cm/year. Sediment contamination abruptly increased from the pre-1930s deposits to the post-1981 deposits. The concentration levels increased two to five times for Pb, As, Zn, and Cu, about 10 to 15 times for Cr, Sb, and Hg, up to 34 times for Cd, and 25 to 67 times for DDTs, PCBs, and PAHs. The concentrations of most contaminants remained approximately constant until the late 1980s when they started to decrease slowly. The decreasing trends were most prominent for heavy metals and anthracene, less prominent for DDTs, and almost absent for PCBs and most PAHs. Discussion  Different temporal and spatial patterns for various contaminants make it possible to distinguish between anthropogenic point sources from local industry (anthracene, Cr, Cd), possible diffuse sources (most PAHs), and geological background (V, Co, Ni, and Mo). The observed recent trends in heavy metal and persistent organic pollutant contamination are generally consistent with data from other Central European rivers. The roughly balanced contamination levels in sediments from the lake and the adjacent river channel suggest that the oxbow lake deposits reflect immediate levels of the contamination bound to suspended particulate matter passing through the river. Conclusions  The investigated oxbow lake accumulated suspended sediment from Morava River, developing a thick sedimentary body. The sediments offer a good time framework to study historical contamination of the river on a decade time scale. Continuous contamination trends can be traced back to the early 1980s. The results show that stratigraphic analysis of cores has a good potential for identification of uninterrupted historical trends and unconformities, e.g., due to dredging. Recommendations and perspectives  Oxbow lakes may provide an alternative to floodplains and reservoir deposits when studying river contamination history. High sedimentation rates of up to 7.7 cm/year offer a very good stratigraphic resolution, making it possible to study contamination patterns on annual or even seasonal time scales. On the other hand, oxbow lakes may represent long-term contamination stores, which are unlikely to be redistributed by river erosion and, hence, may possess significant environmental risks for the farther future.