Characteristics of water–sediment processes in Xinping River, a tributary of the Pinglu Canal

Geochemical characteristics of pore water in shallow sediments from north continental slope of South China Sea and their significance for natural gas hydrate occurrence

Water flow and sedimentation processes have been significantly erratic at the Chókwè Irrigation Scheme (CIS) and have affected its hydraulic performance. Given its expansion there is need to understand these processes taking place on-site and along the channels of the scheme. CIS being the biggest project of its kind in Mozambique requires proper management of water flow and sedimentation processes. Therefore, the effect of water flow, sediment transport and deposition parameters on the performance of the CIS is needed. In order to determine the effect of spatial and temporal water flow and sediment distribution trends along the irrigation canals, there is need to establish a correlation between these parameters. Determining the influence of water flow velocity on sediment settling rate at different depths along the canal reaches is important in managing the CIS. In addition, a developed decision-support tool to predict sediment deposition is required. For this reason, it is therefore crucial to carry out a timely assessment of water flow and sedimentation processes in CIS in a review concept. From the current review, some gaps that exist for more focused research on Chókwè Irrigation Scheme have been identified. In this regard therefore, there is need to develop an effective support tool for managing water flow and sediment deposition along the canal reaches with a view to increasing crop production in CIS.

In aquatic ecosystems, invertebrate bioturbation significantly influences microbial activities and biogeochemical processes in sediments by modifying water and sediment fluxes at the water-sediment interface. We apply the concept of ecosystem engineering to develop a qualitative general understanding of the role of bioturbation on microbial processes in different benthic environments. We hypothesized that the effects of the bioturbation mode (sediment reworking, biogenic structure building, bioirrigation) on microbial processes vary between diffusion- and advection-dominated benthic environments because bioturbation does not have the same influences on hydrological exchanges (and the flux of resources for micro-organisms living in sediments) at the water-sediment interface of the two systems. To test this hypothesis, we experimentally compared the influence of three bioturbation modes (fine-sediment reworking, U-shaped structure burrowing, and gallery-network burrowing) in a diffusion-dominated system (fine sediments/low interstitial flow rates) and an advectiondominated system (coarse sediments/advection of water in sediments). Our analysis demonstrated that bioturbation modes in the two systems had different impacts on microbial activities. For instance, U-shaped tube burrowing by animals increased O2 consumption in the diffusion- dominated system but produced the opposite effect in the advection-dominated system. The influence of bioturbation was also negatively related to interstitial flow rate, the bioturbation having a higher influence on O2 consumption in the diffusion-dominated system than in the advection-dominated system. According to our hypothesis, bioturbation modified microbial processes in sediments depend on the hydrological characteristics of the system. In the diffusion-dominated system, invertebrate bioturbation can produce water fluxes at the watersediment interface that may strongly influence microbial processes in sediments. In contrast, in the advectiondominated system, invertebrate bioturbation can only modify the water circulation patterns in sediments, moderately affecting microbial processes. Consequently, it is necessary to use a conceptual framework which takes into account the features of sediment habitats in order to allow a better prediction of bioturbation effects on sediment biogeochemistry. With this aim, the conceptual scheme of ecosystem engineers can be an organizing principle to integrate the complex relationships among physical habitat, bioturbation mode and microbial activity.

Summary1. Our objective was to measure the effects of bioturbation and predation on the physical characteristics and biogeochemical processes in river sediments.2. We investigated the impacts of tubificid worms tested separately and together with an omnivore (Gammarus pulex), which does feed on tubificids, on sediment distribution, water flux, sediment organic carbon, biofilm biomass and microbial activities, and the concentrations of dissolved oxygen, dissolved organic carbon, PO, NO, NO and NH in slow filtration sand–gravel columns. We hypothesised that gammarids, which exploit the top 2–3 cm of the sediment, would modify the impact of worms at the sediment surface.3. In experiments both with and without gammarids, bioturbation by the tubificids modified both the distribution of surface particles in the sediment column and water flux. In addition, microbial aerobic (oxygen consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) processes in the sediment were stimulated in the presence of tubificid worms. However, G. pulex did not affect either the density or bioturbation activity of the tubificid worms.4. Bioturbation by the benthos can be a major process in river habitats, contributing to the retention of organic matter in sediment dynamics. The presence of at least one predator had no effect on bioturbation in sediments. In such systems, physical heterogeneity may be sufficient for tubificids to escape from generalist predators, though more specialised ones might have more effect.

The process of sedimentation has been studied in a small, steep laboratory flume with a dam, which causes the hydraulic jump in the reservoir. The two-dimensional and three-dimensional bed profiles were observed in experiments with coarse and fine sediment, respectively. The profiles of water surface and sediment deposition are simulated numerically with the application of one-dimensional continuity flow equation and sediment transport. The simulated results coincide well with the observed ones except undulation bed profiles.

The research dealt with the geomorphological development of Al-Numaniyah Ox-bow Lake's, which was a former turning point and separated from the course of the Tigris River near the city of Al-Numaniyah in central Iraq. It became clear from the research the role of natural characteristics in the formation and geomorphic development of the lake, and it was estimated that the lake was cut off from the Tigris naturally in 1884, and since that time the lake was subjected to atrophy and its area shrunk due to the impact of water and wind sedimentation, but human intervention contributed to changing the direction of development towards the expansion of its area in the period until it reached its current area (1.42) km 2, through its previous use as a quarry for the extraction of table salt, and its current use as a pool for draining water from neighboring agricultural lands. The interruption of the torsion from the river and its transformation into a lake had effects (geomorphic, hydrological, environmental, pedological) in terms of weathering, erosion and sedimentation processes, in addition to the variation in the characteristics of the lake water between summer and winter due to the effect of the variation of climate elements, agricultural seasons, quantities of drainage water and the percentage of groundwater recharge, and in general The high salinity of the water affected the salinity of the banks of the lake and the neighboring areas to the extent that it was known as (salt river) or (Al-Numaniyah Salt). The land uses of the lake and the surrounding land have changed as a quarry for salts or an agricultural wasteland, with the land cover changing towards an increasing number of land uses at the present time, and the research ended with some targeted suggestions.

Coarse-grained DEM study of solids sedimentation in water

There is a close relationship between geochemistry and agriculture. The soil, water and atmosphere provide nutrients for plant growth, so the growth and development of plants are affected by the geochemical characteristics of soil, water, and atmospheric sediments. There is a Chinese proverb that a plant grows orange on south of the Huaihe River and fen on north of the Huai River. Therefore, it is not only sunshine, temperature, air, water, but also soil fertility that affects the growth of plants. Soil fertility includes trace elements and rare earth elements. There are also some elements in the soil that have a special role in human health[2]. Similarly, the lack and excess of elements in the soil can cause corresponding endemic diseases. In recent years, fertilization and spraying of pesticides in agricultural activities and the discharge of waste water, slag and exhaust gas from industry have had a great impact on the soil. The rapid increase in the content of organic chemicals and heavy metals in the soil will be absorbed by plants into the food chain, which will affect human health. It is very meaningful for land and resources management, agricultural industrial restructuring, and high-quality agricultural planning to investigate the geochemical characteristics of soil, water and atmosphere. Because the absorption of chemical elements in plant growth comes not only from the soil, but also from the supply of irrigation water and atmospheric dust, land quality geochemical survey collects soil, irrigation water, atmospheric dry and wet sediments and agricultural products. The investigation contains elements that affect plant growth and elements that affect life and health. By analyzing the elements in soil, irrigation water, and atmospheric sediments, the relationship between them and the growth of crops and the content of elements in agricultural products is obtained. Then carry out land quality geochemical evaluation, and divide areas suitable for crop growth and areas not suitable for plant growth which contaminated with heavy metals, excessive pesticide residues, organic chemicals, etc. The geochemical classification of land quality is obtained. According to grading investigate the geological factors, environmental factors and human factors that affect land quality, grasp the geochemical reality and ecological problems caused by human activities, and predict the trend of development. Based on the understanding of planting structure, land use status, etc., the we looks for suitable planning suggestions for local development. (1)In terms of land and resources management[3], it includes providing evidence for the classification and grading of arable land, land planning, basic farmland demarcation, land consolidation, land stripping, and balance of arable land. Through the land quality geochemistry investigation, according to the distribution of land quality geochemistry, combined with soil type and land use, the cultivated land classification. To guide the layout of construction land and basic farmland in the light of the current land use situation and recent planning. In terms of land consolidation, it can provide basis for land consolidation and improve ecological conditions according to the land quality geochemistry level. (2) In the adjustment of agricultural industry structure, it provides scientific basis for the development and utilization of high-quality land resources and then helps local economic development. Through investigation, it is found that the land resources such as selenium, strontium, zinc and other special land resources and pollution-free land[4], on which we can develop special agricultural products and green agricultural products, thereby increasing the additional economic value of agricultural products and improving market competitiveness.

Effect of soil and water conservation measures on hydrological processes and sediment yield in the highlands of North-Western Ethiopia

Mobilisation of toxic trace elements under various beach nourishments

Numerical simulation on the water - sediment characteristics and foreshore evolution of the linding estuary

Excessive sedimentation of fine particles on stream beds has been recognized as a major threat to running-water ecosystems. Deposition of fine sediments often affects hyporheic zone (HZ) functioning by (1) reducing hydrological exchanges at the water–sediment interface and by (2) increasing the organic matter (OM) content of surface sediments. These two factors usually occur concurrently to control biogeochemical processes in sediments. In the present study, experimental and modelling approaches were coupled to evaluate the contribution of these factors on the biogeochemical functioning of the HZ. We used a one-dimensional (1D) vertical model taking into account the hydrodynamic properties, the vertical distribution of the OM and the main microbial processes involved in OM processing (aerobic respiration, denitrification, nitrification and sulphate reduction). This Mobile-Immobile Model for Organic Matter (MIM-OM) model was calibrated and validated using experimental data (conservative tracer, dissolved oxygen and nitrate concentrations) obtained in filtration columns filled with a porous sedimentary matrix. Simulations showed that organic carbon content and Darcy velocity acted in concert to shape biogeochemical processes in stream sediments. The use of the MIM-OM model on data obtained in filtration columns impacted by fine sediment deposition indicated that the biodegradability of the OM (modified through the degradation parameter kPOC) also played a key role on biogeochemical processes occurring in sediments. In conclusion, the MIM-OM model appears as an efficient simulation tool to evaluate biogeochemical functioning in river sediments under different conditions (granulometry, quality of surface water and clogging).

The purpose of the study is to identify the possibilities of mathematical modeling in solving problems of quantitative assessment and prediction of hydrothermodynamic characteristics of lakes of different origins in the permafrost zone based on available information about their morphometry. The object of the study is 420 of morphometrically studied lakes in Yakutia of different genetic origin. The choice of an adequate hydrothermodynamic model of processes in the “atmosphere – lake – bottom sediments” system, as well as sources of information on the atmospheric impact on lakes (reanalysis and climate prediction) for the studied region was substantiated. Simulation calculations were carried out to assess the retrospective interannual and intraannual dynamics of abiotic processes in water and bottom sediments of lakes located in the permafrost zone of different climatic regions of Yakutia. To assess the interannual dynamics of the studied processes in water and bottom sediments of thermokarst lakes located in permafrost zones and being the most widespread in the region, forecast calculations were carried out. In this case, two RCP scenarios for the evolution of anthropogenic greenhouse gas emissions into the atmosphere in the future were used – “best” and “worst” in terms of environmental impact. The prospects for further use of modeling methods in the creation of a system of remote monitoring of unstudied and poorly studied lakes in the Arctic regions of the Russian Federation was assessed.

Forest roads are a common land use feature with a significant impact on sediment yield and the water sediment transport processes within a watershed, seriously disrupting the safety and stability of the watershed. Previous studies have focused on the sediment production processes within the road prism. However, there has been limited attention given to the transport processes of road-eroded sediment at various scales, which is crucial for understanding the off-site effects of road erosion. This paper reviews research conducted on forest road erosion over the past two decades. It summarizes the mechanisms of sediment production from road erosion and provides a detailed analysis of the transport mechanisms of eroded sediments from roads to streams at the watershed scale. The paper also examines the ecological and hydrological effects, research methods, and control measures related to sediment transport caused by forest road erosion. It identifies current research limitations and outlines future research directions. The findings of this review highlight several key points: (1) Most research on forest road erosion tends to be specific and unilateral, often neglecting the broader interaction between roads and the watershed in terms of water–sediment dynamics. (2) Various research methods are employed in the study of forest road erosion, including field monitoring, artificial simulation experiments, and road erosion prediction models. Each method has its advantages and disadvantages, but the integration of emerging technologies like laser scanning and fingerprint recognition remains underutilized, hindering the simultaneous achievement of convenience and accuracy. (3) The transport processes of forest road-eroded sediment, particularly on road–stream slopes, are influenced by numerous factors, including terrain, soil, and vegetation. These processes exhibit significant spatial and temporal variability, and the precise quantification of sediment transport efficiency to the stream remains challenging due to a lack of long-term and stable investigation and monitoring methods. The establishment and operation of runoff plots and sedimentation basins may help offer a solution to this challenge. (4) Both biological and engineering measures have proven effective in reducing and limiting sediment erosion and transport. However, the costs and economic benefits associated with these regulation measures require further investigation. This review provides a comprehensive summary of relevant research on sediment erosion and transport processes on unpaved forest roads, enhancing our understanding of sediment yield in watersheds and offering valuable insights for reducing sediment production and transport to streams.

Lag response of groundwater to changes in water and sediment characteristics in the lower Yellow River, China