Water Drawdown Research Articles

Features of the winter hydrochemical regime of the upper Volga Reservoirs

This article presents the results of a study of the winter hydrochemical regime of the reservoirs of the Upper Volga basin. It has been found that in winter, when there is water drawdown and a decrease in the volume of water, the concentrations of the main ions, nutrients, heavy metals, and oil products increase in comparison with other seasons of the year. Water masses of the Upper Volga reservoirs are characterized by low hardness, neutral pH and low chromaticity. Also noted was an increasing concentration of hydrocarbonates towards the bottom.

Performance of a Hydraulically Linked and Physically Decoupled Stormwater Control Measure (SCM) System with Potentially Heterogeneous Native Soil

This study shows that a physically decoupled but hydraulically linked design focusing on surface infiltration components (i.e., excluding underdrain and infiltration bed systems) can be the preferred way to have a low-cost and robust stormwater control measure (SCM) system. The SCM under investigation in Philadelphia, PA, is a green infrastructure (GI) and has a mirrored design of two sets of hydraulically linked planters. Each planter has an overflow pipe connected to an underground infiltration bed. The system showed excellent overall performance as no overflow/bypass entering the combined sewer. A large variation of saturated hydraulic conductivity was found for the planter soil, and the planter with lower saturated hydraulic conductivity created surface runoff that overflows to the next planter in line. Due to the linked design, the unexpected deviation of performance of a single planter did not affect overall system performance. The infiltration bed showed great variation in water drawdown rate at different water depth, which could be caused by the possible high heterogeneity of the native soil. The study argued that overflow systems, which handled only about 18% of runoff in this study, can be replaced by slightly larger surface area for lower building cost, lower maintenance cost, and more reliable performance.

Fish assemblages in a Mississippi reservoir mudflat with low structural complexity

In shallow reservoirs, seasonal water drawdowns expose littoral areas and over time produce barren mudflats. When flooded, mudflats provide homogeneous substrates, turbid water, and eroding shorelines of limited ecological value. We hypothesized that in mudflats structurally complex habitats are occupied by more fish, smaller fish of a larger range in sizes, more species, and fish assemblages that are different from those in simpler habitats. We tested these hypotheses over two consecutive years with fish collections made in sites with varying structural complexity. Results indicated that structural complexity harbors more fish in transects and enclosures. Structural complexity did not influence median length, but length range increased with structural complexity. Average species richness increased with structural complexity. Fish assemblage composition changed as structural complexity increased. The ability of cover to provide survival, growth, and carrying capacity benefits is fundamental to programs aimed at increasing structural complexity. Results suggest observed effects on fish assemblages can lead to such benefits. Considering mudflats are a major component of reservoirs, expand as reservoirs age, and there is a potential to exert meaningful change on fish assemblages of impounded rivers by managing mudflats, we suggest additional attention is needed to develop practical habitat restoration options.

Stability analysis for nonhomogeneous slopes subjected to water drawdown

Comparing with the homogeneous slope, the nonhomogeneous slope has more significance in practice. The main purpose of the present study is to provide a preliminary idea that how the nonhomogeneity influences the stability of slopes under four different water drawdown regimes. Two typical categories of nonhomogeneity, identified as layered profile and strength increasing with depth profile, are included in the paper, and a nonhomogeneity coefficient is defined to quantify the degree of soil properties nonhomogeneity. With a modified discretization technique, the safety factors of nonhomogeneous slopes are calculated. On this basis, the variation of safety factor with the nonhomogeneity coefficient of friction angle and the water table level are investigated. In the present example, safety factor correlates linearly with friction angle nonhomogeneity coefficient from a whole view and the influences of the water table level on safety factor is basically similar with that in homogeneous condition.

Activity law and hydraulics mechanism of landslides with different sliding surface and permeability in the Three Gorges Reservoir Area, China

The Three Gorges Hydropower Station is the largest hydropower station worldwide and the largest project ever built in China. There are about 2619 ancient landslides affected by reservoir level fluctuation in the Three Gorges Reservoir (TGR) area. More than 670 landslides have been reactivated and eight landslides have failed since the impoundment of the reservoir in June 2003, which seriously threatens people's safety and property. In this study, taking a large number of re-active and failed landslides as statistical samples, the activity and displacements of the reservoir landslide with special regard to different sliding surface and permeability are analyzed and discussed. It is noted that a significant correlation between the landslide movement and the reservoir filling process. The re-active landslides are mainly concentrated in the initial stage of water storage, and the frequency of activation as well as the degree of deformation decrease gradually after the third phase of water storage (175 m). Then the four dominant combinations of the inducing factors of re-active landslide are presented: (a) drawdown of water level, straight line sliding surface, 20–40% degree of immersion, and weak permeability; (b) drawdown of water level, arc sliding surface, 40–60% degree of immersion, and medium permeability; (c) raising of water level, fold line sliding surface, 20–40% degree of immersion, and good permeability; (d) raising of water level, chair shaped sliding surface, 0–20% degree of immersion, and good permeability. Furthermore, when the rate of the reservoir level fluctuation is greater than the permeability coefficient, the shape of sliding surface is from the straight line - the arc - the fold line - the chair shaped, and the hydraulics effect of reservoir water on landslide shifts from the seepage pressure effect to the buoyant effect. Meanwhile, the impact of the reservoir water filling on the landslide reactivation changes from favorable to worse, and the impact of the reservoir water drawdown on the landslide reactivation changes from worse to favorable.

OPTIMIZATION OF GROUND WATER CUTOFF WITH A SIPHON INTAKE FROM THE DRAIN WELLS (AS IN THE CASE OF KAMYANKA-DNIPROVSKA GROUND WATER CUT-OFF)

Relevance of research.To increase the efficiency and reliability of the territory protection against flooding with the infiltration water of the Kakhovsky Reservoir, it is proposed to replace the low-performance ground water cutoff with an airlift water intake system for the protection of the Kamensky Pod’s area with a groundwater cutoff with a siphon intake system from wells. That will enable to increasesignificantly the efficiency and reliability of the ground water cutoff and greatly reduce the specific costs of water pumping. The reliability of the ground water cutoff with a siphon intake system is achieved by ensuring the reliable sealing of the entire siphon collecting conduit. In case of a slightest damage, there is a loss of sealing of the pipes and the water stops flowing into a drain well.
 The purpose of the research. To determine the best parameters of ground water cutoff with a siphon intake system from the well, in particular: - the optimal number of wells, the distance between them; - estimated depths of each wells connected to the siphon collecting conduit; - estimated water flows from each well and the decrease in the static water table in them taking into account the hydro-geological interaction between them during their collaboration; - optimal pipe diameters on each section of the siphon collecting conduit to ensure the reliability of its operation.
 The research methods. The research involves the use of analytical and mathematical methods, in particular: calculations, iterations, forecasting.
 The research results. New approaches enabling to find an optimal variant of uniform water drawdown in the aquifer along the whole length of the siphon water conduit by reducing the depths of the intake wells towards the intake well. To optimize the ground water cutoff with the siphon intake system from the wells, it is proposed to drill drain wells of different depths and place them at different distances from each other along the entire length of the collecting conduit, determining the required depth of the well depending on its diameters and vacuum value.
 The conducted studies as in the case of calculating the Kamyanka-Dniprovskaground water cutoff showed that the minimum depth of drainage wells depends on the diameter of the well and the vacuum value in it, and the most efficient option of all possible ones is the option when there are drain wells with different depths and they are located at different distances from each other that provides a minimum specific cost for the construction of wells and siphon collecting water conduit.

The Hejiapingzi landslide in Weining County, Guizhou Province, Southwest China: a recent slow-moving landslide triggered by reservoir drawdown

The Hejiapingzi landslide is a slow-moving landslide along the shore of the reservoir created by the Xiangbiling hydropower dam in Weining County, Guizhou Province, Southwest China. Movement caused cracks in the land surface and residential buildings of Heping village on 20 August 2017 and was triggered after an 8-day continuous drawdown of the reservoir water by 2.2 m. Field investigations and borehole and landslide surface monitoring were carried out to determine the landslide features and deformation characteristics. Based on analysis of the monitoring data, the behavior of the landslide was neither spatially nor temporally uniform. In general, it could not move quickly due to the gentle sliding surface. The possible reasons for landslide occurrence were the drawdown of the reservoir water, the increase in seepage force, and the loss of strength in a soft mudstone layer to form the landslide slip surface. Although mitigation measures, including engineering control or resident relocation to a safe place, have not yet been finally determined, some interim measures including covering landslide cracks, subsurface monitoring, decreasing the reservoir drawdown velocity, and setting velocity thresholds of landslide displacement for warnings are advised to reduce the landslide risk caused by planned reservoir drawdown in 2019.

Participatory Effect of Water Drawdown on Initiation and Propagation of the Ground Cracks South of Lake Burdur (Turkey)

Ground cracks occur in many parts of the globe due to various causes. In Burdur (Turkey), they have been observed on an old alluvial fan encompassing 9 km by 7 km in an area south of Lake Burdur. This 3 m deep crack system continues along a line extending to 850 m, with the largest segment being about 170 m long. Because the cracks are close to a populated area, where damaging earthquakes had occurred in the past, further anxiety is created among the general population as to their source mechanism(s)—particularly if they are related to an imminent earthquake. An accurate mechanism for their occurrence requires resolution of multitude of issues. One aspect not considered to date is the drop in the lake’s water level of about 15 m in the last 25 years. This study focuses on the role of this drop in the lake’s water level. Satellite remote sensing and slope stability analysis methods are used. The results demonstrate significant influence of rapid drop in water level on the occurrence of cracks. The results are also significant for general understanding of the mechanism of occurrence of ground cracks elsewhere in the world.

State of Play on the Physicochemical Quality of Waters Stored in Concrete Tank Buried Under Wet and Polluted Soil: The Case of the City of Pointe-Noire (CONGO)

The problem of water supply from the public distribution network is still very acute in many cities in developing countries. The intermittent supply of water is forcing some households to build underground tanks of reinforced concrete to store domestic water. This work shows the problem of sustainability of water storage tanks made of concrete, in an aggressive environment but also especially the physicochemical quality of water stored in. The methodological approach chosen is based first of all on the physicochemical analysis of the water stored in these tanks. Indeed, the reliability of tanks, which reflected in their impermeability overlooked external environment, has a direct impact on the quality of stored water and therefore the use that is made daily. In this context, the results of the physicochemical measurements carried out, the comparison of the water coming out of the treatment plant of the National Water Distribution Company (SNDE), made it possible to highlight indices of pollution in the stored waters contained in the buried tanks.. Some samples of stored water, about 42.10%; which poses a public health problem. These results have clearly demonstrated the porous nature of the concrete chosen as the base material used for the construction of said tanks. Thus, anthropogenic pollution is evoked, which is confirmed by the high levels of physicochemical parameters measured in samples RE01, RE02, RE03, RE04, RE04, RE05, RE10, RE11 and RE12. In addition, 57.9% of these stored waters have low mineralization. These are acceptable as drinking water (RE06, RE07, RE08, RE09, RE13, RE14, RE15, RE16, RE17, RE18 and RE19). These waters identified as such must be subject to specific treatment and time monitoring. These results were obtained during dry season. During this period, there is drawdown of ground water. In rainy season, ground water is enhanced and exchanges are more important.

Slope Stability of an Earth Dam during Drawdown Conditions (KHASA-CHAI Dam) as a Case Study

Aiming in this research was to have a clear view about the behavior of Khasa-Chai Dam during the draw down action taking into consideration the newly built of this dam which was filling during the time of this article, the upstream slope was investigated by taking drawdown of the water from the reservoir. This dam is consists of the zoned embankment with a total length of (2.36 km) with an upstream slope (1v:3h) and downstream slope (1v:2h). Slope stability was investigated during the drawdown of the water from the reservoir by considering the water in the reservoir to be at maximum water level and by taking two cases during the rapid and slow drawdown. SLOPE/W which is a sub program from Geo-Slope software was used in association with SEEP/W software to find the factor of safety of the upstream slip surface during the drawdown conditions. It was noticed from the drawdown conditions that the phreatic line falls almost at the same position for both cases. Also for both cases the factor of safety of the upstream slip surface falls above the value of (1.0) and that is mean the upstream slope is in a safe condition when the water drawdown. The exit gradient and the rate of flow at the downstream face decrease with time as the water in the reservoir drawdown which means the factor of safety against boiling increases with time. Â

Landslide deformation behavior influenced by water level fluctuations of the Three Gorges Reservoir (China)

Water level fluctuations that occurs during filling-drawdown operations in man-made reservoirs can result in accelerations or reactivations (or even catastrophic failure) of large landslides. For disaster mitigation, a monitoring system comprising manual and automatic GPS systems, borehole inclinometers, and groundwater piezometers was installed to investigate the slope deformation behavior of a large reactivated landslide known as the Shuping landslide at the Three Gorges Reservoir, China. The long-term monitoring data (2003–2015) focused on the landslide deformation, which was triggered by water level fluctuations, is presented in this study. The cumulative displacement curves showed a step-like behavior, suggesting a lower base activity superimposed by phases of acceleration, which appeared during reservoir drawdown periods and rainy seasons. Based on statistical Pearson correlation analysis, the increase in landslide activity is dominated by reservoir water drawdown, rather than rainfall. The durations of the slide acceleration phases are much shorter than the reservoir water drawdown durations. Based on in-site piezometer monitoring data and numerical simulation, the potential causes are the hydraulic processes in the slope with much smaller groundwater drawdown velocities and hydraulic gradients in the initial stage of the reservoir water drawdown period.

Highly Dynamic Methane Emission from the West Siberian Boreal Floodplains

The West Siberia Lowland (WSL) is one of the biggest wetland areas in high latitudes; however, measurements of gas fluxes from WSL floodplain wetlands were absent. During 2015–2016, we made first effort to estimate methane emission from floodplain using chamber method. Obtained fluxes varied greatly with medians from zero to 17.5 mgC·m−2·h−1. We found that observed heterogeneity could be addressed for further upscaling by grouping the flux observations using a set of environmental parameters: i) floodplain width (wide/narrow), ii) microtopography (elevated/depressed), iii) inundation during the measurements («wet»/«dry»). We found that several classes could be easily merged basing on CH4 emission rates: i) flux median from both «wet» and «dry» depressions of wide floodplains reached 4.21 mgC·m−2·h−1, ii) «wet» elevations within wide floodplains and all small «wet» floodplains had lower flux of 1.47 mgC·m−2·h−1, iii) «dry» elevations within wide floodplains and all small «dry» floodplains had the lowest median of 0.07 mgC·m−2·h−1. Besides the common factors which influence the methane fluxes, we also found extreme methane emission during ten days after main water subsiding in Ob’ floodplain with further gradual decreasing of fluxes and dispersions. We suggested that methane release could be triggered by abrupt hydrostatic pressure decrease induced by water drawdown.

Influences of reservoir water level drawdown on slope stability and reliability analysis

ABSTRACTTo investigate the influences of reservoir water level drawdown on slope stability, a series of numerical simulations were carried out to examine the impacts of slope angle, slope permeability and water drawdown speed on the pore water pressure (PWP) change during seepage, as well as the factor of safety (Fs) of the slope. Based on the numerical results, an estimation model relating the factor of safety to the influential factors mentioned above was developed. The model expression indicates that there are interaction effects between the slope angle, the drawdown speed and the slope permeability, with regard to the influences on slope stability. Furthermore, in view of the uncertainty characteristics of the slope permeability, reliability assessment was performed to examine the influences of those key parameters mentioned above on the probability of slope failure.

Seismic stability of a rock slope with discontinuities under rapid water drawdown and earthquakes in large-scale shaking table tests

A series of large-scale shaking table tests was performed to clarify the dynamic stability of a rock slope with discontinuous structural surfaces under rapid water drawdown. A wave absorber consisting of a porous sponge and iron gauze was used to eliminate the adverse effects of water waves in the tests. The results show that the slope surface, elevation, surface microtopography, and bedding structural surface have an impact on the amplification effect of the slope. MPGA (the acceleration amplification coefficient) has a positive correlation with the peak acceleration of the input wave. The damage evolution process of the slope during earthquakes can be identified and includes three stages: formation of tiny cracks (0.074–0.148 g), crack propagation in the surface slope (0.148–0.297 g), and sliding failure (0.297–0.446 g). According to the acceleration vectors of the blocks, the differences in the acceleration vectors between adjacent blocks were the main trigger of the slope deformation during earthquakes. P- and S-waves mainly induced the uneven settlement deformation and horizontal sliding movement of the surface slope under the horizontal and vertical seismic loads, respectively. According to the analysis of ΔMPGA (the increment of MPGA) after rapid drawdown occurred, rapid drawdown mainly has a considerable impact on the surface slope between the high and low water levels during earthquakes, particularly from 0.148 to 0.297 g; however, its impact began to decrease after the occurrence of failure deformation from 0.297 to 0.446 g. Moreover, the relationship between the structural surface and the dynamic failure mode was identified.

Can water-level management reduce malaria mosquito abundance around large dams in sub-Saharan Africa?

BackgroundWater level management has been suggested as a potential tool to reduce malaria around large reservoirs. However, no field-based test has been conducted to assess the effect of water level management on mosquito larval abundance in African settings. The objective of the present study is to evaluate the effects of water level drawdown rates on mosquito larval abundance.MethodsTwelve experimental dams were constructed on the foreshore of the Koka Dam in Ethiopia. These were grouped into four daily water drawdown treatments, each with three replicates: no water-level drawdown (Group 1; Control), 10 mm.d-1 (Group 2), 15 mm.d-1 (Group 3) and 20 mm.d-1 (Group 4). Larval sampling was conducted weekly for a period of 6 weeks each in the main malaria transmission season (October to November 2013) and subsequent dry season (February to March 2014). Larval densities were compared among treatments over time using repeated measures Analysis of Variance (ANOVA).ResultsA total of 284 Anopheles mosquito larvae were collected from the experimental dams during the study period. Most (63.4%; n = 180) were collected during the main malaria transmission season while the remaining (36.6%; n = 104) were collected during the dry season. Larvae comprised four Anopheles species, dominated by Anopheles arabiensis (48.1% of total larval samples; n = 136) and An. pharoensis (33.2%; n = 94). Mean larval density was highest in control treatment dams with stable water levels throughout the study, and decreased significantly (P < 0.05) with increasing water drawdown rates in both seasons. During the main transmission season, anopheline larval density was generally lower by 30%, 70% and 84% in Groups 2, Group 3 and Group 4, respectively, compared with the control dams (Group 1). In the dry season, larval density was reduced by 45%, 70% and 84% in Groups 2, Group 3 and Group 4, respectively, when compared to the control dams.ConclusionIncreased water drawdown rates were associated with lower mosquito larval abundance. Water level management could thus serve as a potential control measure for malaria vectors around reservoirs by regulating the persistence of shallow shoreline breeding habitats. Dam operators and water resource managers should consider incorporating water level management as a malaria control mechanism into routine dam operations to manage the risk of malaria transmission to human populations around reservoirs.

Three-dimensional stability analysis of slope in unsaturated soils considering strength nonlinearity under water drawdown

In slope stability analyses, the soil has been frequently considered dry or saturated, whereas the soil is in fact unsaturated in many cases. Owing to the existence of matric suction, the strength properties of unsaturated soils are greatly different from dry or saturated soil, and thereby leading to diverse stability conditions of the slope. Based on the kinematical approach of limit analysis, in this study, a three-dimensional (3D) stability analysis was conducted for slopes in unsaturated soils. The effects of matric suction distribution patterns, the nonlinearity of the strength under soil-water characteristic curves and the water drawdown were investigated to explore the shear strength and stability of a slope in unsaturated soil. It was found that, when the matric suction is uniformly distributed, the stability factors of the slope increase linearly along with the matric suction. In addition, when the matric suction increases linearly with the depth, the enhancing effect of the matric suction on the slope stability intensifies as the variation magnitude of the matric suction increases, especially for a gentle slope with a narrower width. For nonlinear patterns, different soil-water characteristic curve (SWCC) models will lead to diverse shear strengths and stability conditions of the slope. The water drawdown has significant effects on the functions of the matric suction as well as slope stability.

Variations in hydro-chemical properties and source insights of coalbed methane produced water of Raniganj Coalfield, Jharkhand, India

The production of coalbed methane is increasing rapidly in Raniganj coalfield of India. The present statistics of methane gas production and produced water is about 1.7 mmscmd (million metric standard cubic meter per day) and 12160 m3/day respectively from 560 CBM wells. The major concerns are challenges related to CBM produced water treatment, it's handling, uses for various purposes and its proper disposal is yet to be resolved, considering physico-chemical parameters, socio-economic, environmental and techno-commercial aspects. In view of this, a detailed study of CBM produced water of Raniganj coalfield has been carried out to evaluate hydro-chemical variations, quantity, quality, related aquifer characteristics, options of treatment, suitable beneficial uses and disposal. The large amount of TDS is the major concern contributed by cations and anions like Na+, Ca2+ and HCO3−. The trace metal content obtained through Inductively Coupled Plasma Mass Spectrometry (ICPMS) analyses such as Fe2+, Mn2+, Zn2+, Sr2+ and Al3+ varies from 0.12 to 0.94, 0.002 to 0.651, 0.001 to 0.041, 0.005 to 0.801 and 0.002–0.092 mg/l respectively. Atomic absorption spectroscopy (AAS) was used for cations (Na+, K+, Mg2+ and Ca2+) distribution found ranged from 289 to 1136, 0.00 to 0.94, 0.18 to 1.82 and 10.2–21.2 mg/l respectively, whereas, anions (SO42−, F−, Cl−, NO3− and HCO3−) were determined using Ion Chromatography (IC), found varying from 0.14 to 1.62, 1.042 to 4.862, 114.42 to 565.21, 7.41 to 70.4 and 1923.4–3129.4 mg/l respectively. The CBM produced water is classified as Na+–K+–CO32-–HCO3- and Na+–HCO3- type attributed to different rock formations of aquifers and deeper coal seams. TDS and trace metals concentrations are controlled by depositional environment, local marine transgression occurred during the Sakmarian - Artinskian geological period and inherited from groundwater mineral interactions. The results of proposed model for quality parameter prediction signifies TDS content is observed to be low during the initial five years of production and gradually increases with time. The similar trend is shown by HCO3−, Na+, SO42−, F−, Cl− and NO3− signifying the rock interaction and alterations is the only source of minerals and ions. Initially, the shallow aquifer water having interaction with fresh water recharge dilutes the concentrations of different water quality parameters, but as production continues, the concentration of constituents directly controlled by formation rocks and may increase until it reaches the saturation point. The continuous drawdown of water from a large number of CBM wells changing the regional static hydrological balance including a drainage system and it may take long spells to recuperate its original levels. This study can be utilized in designing treatment processes, beneficial uses and exploring the new water resources in Raniganj coalfield.

Dynamic response characteristics of a rock slope with discontinuous joints under the combined action of earthquakes and rapid water drawdown

In order to study the dynamic response characteristics of a rock slope with discontinuities under the combined action of earthquakes and rapid water drawdown, a large-scale shaking table test was performed on a rock slope with discontinuous joints. Wenchuan earthquake (WE) seismic records were performed to investigate the horizontal and vertical acceleration response and displacement response. In particular, three-dimensional optical measurement techniques was used to obtain the slope surface displacements. A comparison was made on the seismic response according to the analysis of PGD (peak ground displacement) and M PGA (acceleration amplification coefficient) of the modeled slope. The results show that the experimental slope mainly underwent settlement and horizontal deformation when the WE records were applied in the z and x directions, respectively. The slope was first shaken by the P wave, which caused the differential settlement to occur at the surface slope; then, the slope was shaken more severely by the S wave, which led to a greater horizontal deformation. Moreover, analysis of the ΔPGD (increment of PGD) and ΔM PGA (increment of M PGA) under rapid drawdown suggests that the rapid water drawdown mainly impacts the deformation of the surface slope, particularly between the high and low water levels. The water infiltration through the cracks softened the material of the surface slope, and the rapid drawdown also enhanced the slope deformation. In addition, the damage evolution process of the slope can be identified, mainly including three stages: an elastic stage ( 0.336 g).

Effects of bioirrigation on the spatial and temporal dynamics of oxygen above the sediment–water interface

AbstractBurrow ventilation by tube-dwelling benthic animals affects solute exchange between sediments and water by 2 means. Drawing of O2-rich water into the burrow increases O2 availability in the sediment and stimulates biogeochemical and microbial processes, whereas flushing of the burrow creates a 3-dimensional flow field above the burrow, which induces mixing. Previous studies have revealed the role of the diffusive boundary layer (DBL) thickness on the exchange of solutes between the sediment and overlying water. Mapping the O2 gradient within the DBL is a challenging task in the presence of benthic faunal activities. We used a novel lifetime-based laser induced fluorescence (τLIF) technique that enables unobstructed observations of spatial and temporal O2 dynamics above burrows inhabited by midge larvae (Chironomus plumosus). We observed instantaneous plumes of O2-depleted water released from the outlet of the burrows and drawdown of O2-rich water above the inlet caused by peristaltic pumping of C....

Distribution and sources of polycyclic aromatic hydrocarbons and phthalic acid esters in water and surface sediment from the Three Gorges Reservoir

After the impoundment of the Three Gorges Reservoir (TGR), the hydrological situation of the reservoir has changed greatly. The concentration and distribution of typical persistent organic pollutants in water and sediment have also changed accordingly. In this study, the concentration, distribution and potential sources of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 phthalic acid esters (PAEs) during the water drawdown and impoundment periods were investigated in water and sediment from the TGR. According to our results, PAHs and PAEs showed temporal and spatial variations. The mean ΣPAH and ΣPAE concentrations in water and sediment were both higher during the water impoundment period than during the water drawdown period. The water samples from the main stream showed larger ΣPAH concentration fluctuations than those from tributaries. Both the PAH and PAE concentrations meet the Chinese national water environmental quality standard (GB 3838-2002). PAH monomers with 2–3 rings and 4 rings were dominant in water, and 4-ring and 5–6-ring PAHs were dominant in sediment. Di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) were the dominant PAE pollutants in the TGR. DBP and DEHP had the highest concentrations in water and sediment, respectively. The main source of PAHs in water from the TGR was petroleum and emissions from coal and biomass combustion, whereas the main sources of PAHs in sediments included coal and biomass combustion, petroleum, and petroleum combustion. The main source of PAEs in water was domestic waste, and the plastics and heavy chemical industries were the main sources of PAEs in sediment.