Centrifugal model test on a riverine landslide in the Three Gorges Reservoir induced by rainfall and water level fluctuation

Frequent soil landslide events are recorded in the Three Gorges Reservoir area,China,making it necessary to investigate the failure mode of such riverside landslides.Geotechnical centrifugal test is considered to be the most realistic laboratory model,which can reconstruct the required geo-stress.In this study,the Liangshuijing landslide in the Three Gorgers Reservoir area is selected for a scaled centrifugal model experiment,and a water pump system is employed to retain the rainfall condition.Using the techniques of digital photography and pore water pressure transducers,water level fluctuation is controlled,and multi-physical data are thus obtained,including the pore water pressure,earth pressure,surface displacement and deep displacement.The analysis results indicate that:Three stages were set in the test(waterflooding stage,rainfall stage and drainage stage).Seven transverse cracks with wide of 1–5 mm appeared during the model test,of which 3 cracks at the toe landslide were caused by reservoir water fluctuation,and the cracks at the middle and rear part were caused by rainfall.During rainfall process,the maximum displacement of landslide model reaches 3 cm.And the maximum deformation of the model exceeds 12 cm at the drainage stage.The failure process of the slope model can be divided into four stages:microcracks appearance and propagation stage,thrust-type failure stage,retrogressive failure stage,and holistic failure stage.When the thrust-type zone caused by rainfall was connected or even overlapped with the retrogressive failure zone caused by the drainage,the landslide would start,which displayed a typical composite failure pattern.The failure mode and deformation mechanism under the coupling actions of water level fluctuation and rainfall are revealed in the model test,which could appropriately guide for the analysis and evaluation of riverside landslides.

Fractal characterization of sediment particle-size distribution in the water-level fluctuation zone of the Three Gorges Reservoir, China

The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landscape. Siltation, eutrophication, enrichment of heavy metals, and methane emissions in the WLFZ have been widely associated with sediment and soil particles generated from the upstream catchment or upland slopes. However, little attention has been paid to the complexity of sediment particle-size distributions in the WLFZ. In the present study, core samples(from a 345 cm thick sediment core from the base of the WLFZ), slope transect surface samples(across/up a WLFZ slope), and along-river/longitudinal surface samples(from the reservoir reaches) were collected. Laser granulometry and a volume-based fractal model were used to reveal the characteristics of sediment particle-size distributions. Results indicate that the alternation of coarse and fine particles in the sedimentary core profile is represented as a fluctuation of low and high values of fractal dimension(D), ranging from 2.59 to 2.77. On the WLFZ slope transect, surface sediment particles coarsen with increasing elevation, sand content increases from 3.3% to 78.5%, and D decreases from 2.76 to 2.53. Longitudinally, surface sediments demonstrate a downstream-fining trend, and D increases gradually downstream. D is significantly positively correlated with the fine particle content. We conclude that D is a useful measure for evaluating sediment particle-size distribution.

Analysis of the relationship between water level fluctuation and seismicity in the Three Gorges Reservoir(China)

The Three Gorges Reservoir is a good site for the further researches on reservoir induced seismicity due to decades＇ seismic monitoring. After the first water impounding in 2003, seismic activity becomes more frequent than that before water impoundment. In order to quantitatively study, the relationship between the water level fluctuation and earthquakes in TGR, we introduced statistical methods to attain the goal. First of all, we relocated the earthquakes in TGR region with double difference method and divided the earthquakes into 5 clusters with clustering analysis method. Secondly, to examine the impacts of water level fluctuation in different water filling stages on the seismic activity in the 5 clusters, a series of statistical analyses are applied. Pearson correlation results show that only the 175 m water level fluc- tuation has significantly positive impacts on the seismic activity in clusters I, II, III and V with correlation coefficients of 0.44, 0.38, 0.66 and 0.63. Cross-correlation analysis demonstrates that 0, ], 0 and 0 month time delay separately for the clusters I, II, III and V exists. It illustrated the influences of the water loading and pore pressure diffusion on induced earthquakes. Cointegration tests and impulse response analysis denoted that the 175 m water level only had long term and significant effects just on the seismic events in the intersection region of the Fairy Mount Fault and Nine-brook Fault. One standard deviation shock to 175 m water level increased the seismic activity in cluster V for the first 3 months, and then the negative influence was shown. After 7 months, the negative impulse response becomes stable. The long-term effect of the 175 m water impoundment also proved the important role of pore pressure diffusion in RIS with time.

Protection and Ecological Restoration of Water Level Fluctuation Zone in the Three Gorges Reservoir

Water level fluctuation zone(hereinafter referred to as "WLFZ") is a transitional ecosystem between terrestrial ecosystem and aquatic ecosystem,and also a key area to control its neighboring terrestrial and aquatic ecosystem. After the Three Gorges Reservoir was put into use,ecological environment of its WLFZ has aroused wide concern from domestic and foreign experts. On the basis of introducing characteristics of WLFZ of the Three Gorges Reservoir,current ecological environment and main problems of this area were analyzed,plant selection and configuration was elaborated as well as the implementation effect of many WLFZ protection and ecological restoration modes. In view of the actual conditions,pertinent suggestions were proposed for WLFZ of the Three Gorges Reservoir,namely classified protection and ecological restoration,enhancing monitoring and assessment of current situation and change tendency,carrying out technical researches and demonstration of WLFZ wetland ecological restoration.

Comparison of the rise of water level in the typical catchments,Three Gorges Reservoir area

Water level is an important index for studying hydrologic processes. Water level rise processes were studied in three catchments(catchment I, II, III in Chen Jiagou watershed in the Three Gorge Reservoir Area) with different areas to provide useful information to inform data extension from a gauged-catchment to an ungauged catchment. The results showed that there are seasonal changes in the dominant driving mode of the rise of the water level. The rise of the water level in March is likely mainly driven by the mode of stored-full runoff, and in September or October, it is mainly driven by Horton-flow. The correlation coefficients of all indexes were significant among the three catchments, suggesting that these catchments have similarities and that water level data extension is likely to be completed successfully between the large catchment(III-Catchment) and the small catchment(ICatchment). It was confirmed that there is good similarity between the 0.6 km^2 and 6 km^2 catchments, and the data correlation is good between the catchments with the area differences in the Three Gorges Reservoir Area. In addition, the rise processes of the water level in the catchments were not only different under the same rain conditions, but this difference could also change with the rain condition.

Filling of the Three Gorges Reservoir to the 135-m Level: Instant Effects on the Yangtze Discharge and Suspended Sediment Concentration Entering the Estuary

Via the valuable opportunity of the Three Gorges Reservoir (TGR) 135-m filling in June 2003, the Yangtze discharge and suspended sediment concentration (SSC) entering the estuary during the period from 15 May to 15 July 2003 were analyzed to examine the instant effects of the filling on them. The Yangtze discharge and SSC entering the estuary in the periods before, during and after the filling clearly indicated three phases: 1) the pre-storage phase characterized by natural conditions, in which the SSC increased with increasing water discharge; 2) the storage phase, during which the SSC decreased dramatically with decreasing water discharge; and 3) the post-storage phase, during which both the SSC and water discharge remained at relatively low levels first until the end of June, then the SSC increased gradually with increasing water discharge. It seems that the times for the instant effects of the decreasing discharge downstream from the upper Yangtze on the Yangtze discharge and SSC entering the estuary due to the TGR 135-m filling to take place were about 5 d and 1 d respectively, while both were about 18 d for those of the increasing discharge. This probably reflects the buffering and resultantly hysteresis of the 1800-km stretch from the upper Yangtze to the estuary. The results are helpful for scientific and hydrological investigation of the Yangtze mainstream downstream from the TGR Dam and of the estuarine and adjacent coastal waters.

Reservoir-induced landslides and risk control in Three Gorges Project on Yangtze River,China

The Three Gorges region in China was basically a geohazard-prone area prior to construction of the Three Gorges Reservoir （TGR）. After construction of the TGR, the water level was raised from 70 m to 175 m above sea level （ASL）, and annual reservoir regulation has caused a 30-m water level difference after impoundment of the TGR since September 2008. This paper first presents the spatiotemporal distribution of landslides in six periods of 175 m ASL trial impoundments from 2008 to 2014. The results show that the number of landslides sharply decreased from 273 at the initial stage to less than ten at the second stage of impoundment. Based on this, the reservoir-induced landslides in the TGR region can be roughly classified into five failure patterns, i.e. accumulation landslide, dip-slope landslide, reversed bedding landslide, rockfall, and karst breccia landslide. The accumulation landslides and dip-slope landslides account for more than 90%. Taking the Shuping accumulation landslide （a sliding mass volume of 20.7 × 106 m^3） in Zigui County and the Outang dip-slope landslide （a sliding mass volume of about 90 × 106 m^3） in Fengjie County as two typical cases, the mechanisms of reactivation of the two landslides are analyzed. The monitoring data and factor of safety （FOS） calculation show that the accumulation landslide is dominated by water level variation in the reservoir as most part of the mass body is under 175 m ASL, and the dip-slope landslide is controlled by the coupling effect of reservoir water level variation and precipitation as an extensive recharge area of rainfall from the rear and the front mass is below 175 m ASL. The characteristics of landslide-induced impulsive wave hazards after and before reservoir impoundment are studied, and the probability of occurrence of a landslide-induced impulsive wave hazard has increased in the reservoir region. Simulation results of the Ganjingzi landslide in Wushan County indicate the strong relationship between landslide-induced surge and water variation with high potential risk to shipping and residential areas. Regarding reservoir regulation in TGR when using a single index, i.e. 1-d water level variation, water resources are not well utilized, and there is also potential risk of disasters since 2008. In addition, various indices such as 1-d, 5-d, and 10-d water level variations are proposed for reservoir regulation. Finally, taking reservoir-induced landslides in June 2015 for example, the feasibility of the optimizing indices of water level variations is verified.

Soil anti-scourability enhanced by herbaceous species roots in a reservoir water level fluctuation zone

Revegetation is one of the successful approaches to soil consolidation and streambank protection in reservoir water level fluctuation zones(WLFZs).However,little research has been conducted to explore the impact of herbaceous species roots on soil anti-scourability during different growth stages and under different degrees of inundation in this zone.This study sampled two typical grasslands(Hemarthria compressa grassland and Xanthium sibiricum grassland)at two elevations(172 and 165 m a.s.l.)in the water level fluctuation zone(WLFZ)in the Three Gorges Reservoir(TGR)of China to quantify the changes in soil and root properties and their effects on soil anti-scourability.A simulated scouring experiment was conducted to test the soil anti-scourability in April and August of 2018.The results showed that the discrepancy in inundation duration and predominant herbaceous species was associated with a difference in root biomass between the two grasslands.The root weight density(RWD)values in the topsoil(0-10 cm)ranged from 7.31 to 13 mg cm^(-3) for the Hemarthria compressa grassland,while smaller values ranging from 0.48 to 8.61 mg cm^(-3) were observed for the Xanthium sibiricum grassland.In addition,the root biomass of the two herbs was significantly greater at 172 m a.s.l.than that at 165 m a.s.l.in the early recovery growth period(April).Both herbs can effectively improve the soil properties;the organic matter contents of the grasslands were 128.06%to 191.99%higher than that in the bare land(CK),while the increase in the water-stable aggregate ranged from 8.21%to 18.56%.Similarly,the topsoil antiscourability indices in both the herbaceous grasslands were larger than those in the CK.The correlation coefficients between the root length density(RLD),root surface area density(RSAD)and root volume density(RVD)of fine roots and the soil antiscourability index were 0.501,0.776 and 0.936,respectively.Moreover,the change in the soil antiscourability index was more sensitive to alternations in the RLD with diameters less than 0.5 mm.Overall,the present study showed that the perennial herbaceous(H.compressa)has great potential as a countermeasure to reduce or mitigate the impact of erosion in the WLFZ of the Three Gorges Reservoir.

Application of Vegetation Geosynthetic Technique to Slope Stability in the Three Gorges Reservoir

The vegetation geosynthetic reinforced slope is one of the new composite structures in civil engineering. It has a series of characteristics, such as low cost, convenient construction, optimal land utilization and flexible structure, and it has been widely used in hydraulic engineering, road, railway and harbor construction. The Three Gorges reservoir bank protection system is a challenging work. As the background, the interaction mechanism of soil and reinforced material has been studied. The test engineering is simulated by the numerical methods. The failure mechanism of the reinforced slope in the process is studied through analyzing the variation of the displacement, stress, plastic failure fields and factor of safety in the changing process of the water level. The reasonable evaluation of the protecting effect and bank slope stability is carried out. The research results could be used in the protective design and construction in the high slope in the Three Gorges reservoir region, and it also could provide reference to other protective engineerings in the littoral area.

三峡水库小江回水区水华暴发期浮游植物群落结构及其与环境因子的关系

三峡水库蓄水以来,支流水华频发,尤以小江情况最为严重,给三峡库区的生态安全带来较大隐患。为探究支流水华暴发特征和主控因素,于20142021年小江水华暴发期间在小江高阳江段进行浮游植物及环境因子调查,并使用单因素方差分析、聚类分析、百分比相似性分析以及基于距离的线性模型等方法,对小江水华暴发期间浮游植物和环境因子在不同年份不同水层间的差异以及二者的关系进行研究。结果表明:小江水华暴发期内,浮游植物的种类数在43~70种之间,其中2015年蓝藻种类数明显减少,2018年以后硅藻种类数明显减少;采样期间浮游植物平均细胞密度在0.66×10^(6)~61.28×10^(6)cells/L之间,同期表层细胞密度明显高于中层和底层;各层水体间水华微囊藻、铜绿微囊藻、不定微囊藻等10种藻的密度存在明显差异,是主要差异种;显著影响表层、中层和底层浮游植物群落结构变动的环境因子是水位的日平均变幅;水位的日平均变幅与藻类优势种拟合关系显示,当日水位下降幅度在0.5 m以上时,浮游植物平均密度会呈指数级减少。研究结果可为三峡库区支流水华的防控提供数据支持。

周期性水位波动对三峡水库消落带土壤有机碳含量和密度的影响

为探究水位波动对三峡水库消落带土壤有机碳的影响,在三峡水库消落带采集和测定了受不同水淹强度影响的石灰土、紫色土、黄壤及其植物样品,并运用Kruskal-Wallis非参数检验和基于冗余分析的典范分析等方法进行了研究。结果表明:周期性水淹增加了石灰土和紫色土的有机碳含量和密度,但降低了黄壤的有机碳含量和密度。此外,石灰土的有机碳分布还受地上生物量、土壤pH和土层深度的影响,紫色土的有机碳分布还受土层深度和地上生物量的影响,而黄壤的有机碳含量和密度则与地上生物量、土层深度和地下生物量有关。总之,周期性水位波动对消落带土壤有机碳影响深刻,但土壤类型分异了有机碳对水位波动的响应。

面向新时期新需求的三峡水库运行方案研究

本文回顾三峡水库设计洪水、特征水位、运行方案变化调整过程,综述三峡水库运行调度关键技术研究进展和分析来水来沙变化情况。分别采用最可能洪水地区组成法和非一致性洪水频率分析两种途径,推求考虑上游水库群调蓄影响的三峡水库运行期设计洪水及特征水位。结果表明:近10年三峡入库泥沙量比初设成果减少了84.4%,宜昌站水文情势IHA-RVA综合指标为74%、发生了重度改变,三峡水库运行期1000年一遇7~15 d洪量减少了约81.5亿~142.8亿m^(3),初设确定汛限水位的主要制约因素(防洪、泥沙)发生了很大的变化。原单站设计洪水及确定的三峡水库175-155-145 m运行方案,已无法满足新时期水资源高效利用和生态环境保护的新需求。建议把三峡水库运行方案调整为175-160-155 m,主汛期水位在155~160 m区间动态控制运行,长江中下游梅雨结束后应考虑提前蓄水,8月底蓄至163 m左右,9月底蓄至165 m,10月底蓄满。该方案在保证大坝和下游防洪安全的前提下,汛期减少弃水并增加枯水期补水量,预计可增发10%左右的发电量;抬高运行水位也有利于库区航运和减少消落带;9月份尽量不蓄水或少蓄水,可减少蓄水期对下游河道及两湖生态环境的不利影响,具有巨大的经济、社会和生态环境等综合利用效益。当预测预报长江流域可能发生流域性大洪水时,尽快将库水位消落至汛限水位145 m,确保大坝和下游防洪安全。

Water level fluctuations influence microbial communities and mercury methylation in soils in the Three Gorges Reservoir,China

Reservoirs tend to have enhanced methylmercury（MeHg） concentrations compared to natural lakes and rivers, and water level fluctuations can promote MeHg production. Until now, little research has been conducted on the effects of microorganisms in soils for the formation of MeHg during different drying and flooding alternating conditions in the Three Gorges Reservoir（TGR）. This study aimed to understand how water level fluctuations affect soil microbial composition and mercury concentrations, and if such microbial variations are related to Hg methylation. The results showed that MeHg concentrations and the ratios of MeHg to THg（MeHg%） in soils were higher in the seasonally drying and flooding alternating areas（DFAs, 175–155 m） than those in the non-inundated（NIAs, 〉 175 m） and inundated areas（IAs, 〈 145 m）. However, MeHg% in all samples was less than 1%, indicating that the Hg methylation activity in the soils of the TGR was under a low level. 454 highthroughput sequencing of 16 S rRNA gene amplicons showed that soil bacterial abundance and diversity were relatively higher in DFA compared to those in NIA and IA, and microbial community composition varied in these three areas. At the family level, those groups in Deltaproteobacteria and Methanomicrobia that might have many Hg methylators were also showed a higher relative abundance in DFA, which might be the reason for the higher MeHg production in these areas. Overall, our results suggested that seasonally water level fluctuations can enhance the microbial abundance and diversity, as well as MeHg production in the TGR.

三峡水库消落带土壤反硝化及DOM的影响

在重庆主城与涪陵选取了3个典型点位采集土壤样品,并对土壤的理化性质、原位反硝化速率、溶解性有机质(DOM)驱动的反硝化以及库区土壤的微生物进行了考察与分析.结果显示在海拔145~155m区间,淹水期镇安镇、涪陵区和鱼嘴镇最高氨氮(NH_(4)^(+)-N)平均浓度分别为31.32,28.63和19.23mg/kg,均高于落干期.在淹水期,与高海拔区域土壤中硝酸盐氮(NO_(3)^(-)-N)平均浓度相比,低海拔土壤中NO_(3)^(-)-N平均浓度分别增大了46.91%(镇安镇)、37.89%(涪陵区)和29.69%(鱼嘴镇).在淹水期,土壤有机质(SOM)平均浓度随着海拔高程的降低而降低,镇安镇、涪陵区和鱼嘴镇分别从109.16,80.93和82.61mg/kg降至65.63,64.53,53.41mg/kg.土壤中NH_(4)^(+)-N和NO_(3)^(-)-N的含量与现场反硝化速率呈显著正相关(P<0.05),在提供充足的碳(C)和氮(N)营养元素后,土壤潜在反硝化速率表现出较大的时间和空间差异性.在由DOM驱动的反硝化实验中,DOM降解符合一级动力学模型(R^(2)>0.93),N2O累积量符合Logistic模型(R^(2)>0.97).在三峡水库消落带土壤中,反硝化功能微生物主要是Bacillus和Comamonadaceae,其丰度变化与土壤潜在反硝化速率呈现显著的正相关性(P<0.05).

高洪水期运行水位对三峡水库泥沙淤积的影响

三峡水库泥沙问题直接关系到水库库容的长效保持。选取典型高洪水期,基于数值模型探究入库水沙量级、水沙异步及运行水位对三峡库区沙峰输移和淤积排沙的影响。结果表明:入库洪峰的增大抑制了涪陵沙峰比的衰减,并导致更多泥沙输运至坝前,使得坝前沙峰降幅受运行水位的抬升更为显著;变动回水区较常年回水区更易受到入库水沙异步影响,且随着来沙系数的增大,由低水位抬升时淤积占比更高;水库排沙比受入库水沙异步影响有限,且随着入库洪峰、沙峰的增大,排沙比增加的同时对运行水位抬升导致的衰减更为敏感。研究成果初步揭示了入库水沙异步及运行水位对库区沙峰运动与淤积的影响,可为三峡水库汛期优化沙峰排沙调度提供参考。

三峡水库消落带狗牙根根系对紫色土抗剪性能的影响

植物根系对提高土壤抗侵蚀能力起着最主要的作用。为探究根系对三峡水库消落带土壤抗剪性能的影响,以典型草本植物狗牙根及其根土复合体为研究对象,利用原状土和重塑土、采用直剪试验和三轴试验2种方法,揭示根系形态特征、含根量以及布根方式对土壤抗剪性能的影响。结果表明:1)内摩擦角、黏聚力与根系形态特征呈对数正相关;各形态指标对土壤抗剪性能的影响程度依次为:根表面积密度>根体积密度>根长密度>根质量密度>根径。2)根系含量与土壤抗剪性能呈正相关。含根量分别为0.9、0.6和0.3 mg/cm^(3)的根土复合体抗剪强度依次比素土提高14.54%~49.56%、9.09%~35.82%和3.80%~17.58%;内摩擦角依次提高13.95%、13.07%和1.98%;黏聚力依次提高29.37%、24.48%和15.34%。3)交叉布根下土壤抗剪性能最强,与垂直布根、水平布根相比,交叉布根的抗剪强度依次提高4.22%~16.95%和11.45%~32.61%;黏聚力依次提高15.61%和16.09%;最大应力值依次提高3.78%~34.18%和36.86%~41.44%。研究结果可为三峡水库消落带固土护岸的物种筛选、水土保持生态建设以及水库岸线管理等提供参考。

汛期洪水资源化利用对三峡水库淤积影响研究

作为三峡水库诸多优化调度方式中的一种,洪水资源化利用对水库淤积的影响受到持续关注,开展针对场次洪水的相关研究有助于进一步深化对水库淤积科学问题的认识,有望为调度工作提供一定的技术支撑。通过2013年以来的历史水文资料分析与水沙运动数值模拟,探究了入库洪水的输沙过程以及洪水资源化利用对库区淤积与水库排沙的影响。结果表明:洪峰流量介于30000~55000 m 3/s的中小洪水是近年三峡入库洪水的主要形式,随着入库洪峰流量的增加,洪水的地区组成逐渐趋向于金沙江下游、嘉陵江共同主导;常年回水区淤积、水库排沙是“消化”入库泥沙的两种主要途径,且以前者的作用为主;针对Ⅰ-3类入库洪水,坝前起调水位Z 0的抬升或洪水资源化利用对水库淤积的影响主要在于造成了库区淤积的重分布,次要在于改变了水库的排沙作用,在Z 0≤150 m条件下,洪水资源化利用对水库淤积的影响相对较小;针对典型洪水,当武隆洪峰流量Q′WL与入库洪峰流量Q′RK的比值小于1/5(即Q′WL/Q′RK<1/5)且朱沱洪峰流量Q′ZT与北碚洪峰流量Q′BB的比值介于3/2和3之间(即3/2<Q′ZT/Q′BB≤3)时,在Z 0=145 m情景下,洪水量级的提高增加了约50%的入库沙量,而水库调度抬升的库水位不足坝前水深的5%,导致前者较后者产生了更加严峻的变动回水区淤积和水库排沙情势;随着嘉陵江的洪水输沙作用逐渐显著,变动回水区,尤其是嘉陵江与长江干流交汇口下游河道的淤积情势愈发明显,应当予以重视。

三峡水库对城陵矶防洪补偿控制水位研究Ⅰ——需求分析与优化条件

城陵矶地区是长江中下游洪灾最频发的区域之一,是长江水库群防洪的重点保护对象。金沙江下游乌东德、白鹤滩、溪洛渡、向家坝4座梯级水库与三峡水库组成的巨型水库群防洪能力巨大,显著改变了流域防洪调度格局。在概括分析城陵矶地区防洪需求,回顾三峡水库对城陵矶地区防洪补偿控制水位不同阶段成果的基础上,剖析了优化防洪补偿控制水位的研究要点,研究了金沙江下游梯级防洪库容投入情况,进而明确了提高防洪补偿控制水位的有利条件。研究结果表明:在三峡水库水位达到城陵矶防洪补偿控制水位158.00 m后,金沙江下游梯级水库在预留40.93亿m^(3)防洪库容的基础上,尚有30亿~60亿m^(3)富余防洪库容可配合运用,为进一步提高三峡水库对城陵矶防洪补偿控制水位创造了良好条件。

适应水位变化的三峡库区消落带碳汇提升设计及效益评估

【目的】三峡库区消落带受周期性的水位涨落及冬季长时间深水淹没影响,碳汇能力遭受严重破坏。如何恢复并充分发挥消落带生态系统的碳汇潜力,成为三峡库区生态治理的关键议题。【方法】针对复杂水位变化挑战,提出以林塘模式修复消落带生态系统并提升碳汇能力的技术框架,选取位于三峡库区腹心的大浪坝消落带开展实证研究。运用CASA模型测算修复前后大浪坝消落带的净初级生产力(net primary productivity,NPP),基于植被生物量数据计算修复后大浪坝消落带与未修复对照组内不同高程带的碳汇能力,评估林塘碳汇系统的可持续效益。【结果】修复后大浪坝消落带的碳汇能力随时间推移明显提升,NPP由2012年的154.4 g C·m^(2)·a^(-1)增长至2016年的182.5 g C·m^(2)·a^(-1);各高程带的碳汇能力均显著高于对照组,并呈现出随海拔降低而减弱的趋势,170~175 m高程带碳汇能力达到1.827 kg C/m^(2),160~165 m高程带碳汇能力仅为0.830 kg C/m^(2)。林塘系统增强了生态系统的适应性和复原力,形成了适应水位变化的立体固碳模式并有效提升了碳汇效率。【结论】林塘碳汇系统是应对三峡库区复杂水位变化和长时间深水淹没挑战的适应性探索,显示出景观优化、生物多样性、经济效益与碳汇协同耦合的关键特征。研究成果能够为中国大型工程型水库消落带的治理及碳增汇提供科学依据与可复制推广的创新技术模式。

水位变动对三峡水库消落带典型雌激素效应物质及活性的影响

以三峡库区消落带为研究对象,将化学分析与生物测试相结合,研究水位变动对消落带土壤(落干期)和沉积物(淹水期)雌激素效应物质种类和含量及雌激素活性的影响,探讨典型雌激素与雌激素效应的关联程度,以期为水库消落带生态安全和环境健康管理提供重要的数据支撑。借助超高效液相色谱-质谱(UPLC-MS)对8种典型雌激素的赋存与质量浓度进行靶向分析,并使用重组基因酵母筛选(YES)体系检测环境样品雌激素活性,通过相关性分析和浓度加和计算建立化学物质与生物效应间的相关联系。8种典型雌激素仅有雌酮(E1)和乙炔基雌二醇(EE2)被检出,含量在0.025~2.667 ng/g范围内。淹水期的沉积物具有明显的雌激素活性,其雌二醇当量(EEQ)值为0.637~6.987 ng/g。相关性分析结果显示,靶向分析的雌激素效应物质与雌激素效应间无明显相关性,仅能解释29.46%的雌激素活性。水位变动影响消落带雌激素效应物质的种类和质量浓度,淹水提高了沉积物雌激素活性。典型雌激素物质与库区消落带雌激素效应无显著关联。因此,需要开发新的方法与技术,以便更为精确地指导消落带雌激素效应的风险识别与管控。