Sediment runoff

The continental footstep of the Black Sea occupies an intermediate position between the continental slope and the floor of the central depression at depths from 1100-1200 to 1800-2000 m. Morphologically, it is represented by a slightly inclined plain that borders the base of the continental slope. It is a kind of accumulative tail formed owing to the merging of numerous alluvial fans near the mouths of underwater canyons and to the sedimentation matter supplied from the shelf and continental slope due to the sediment runoff and landslide processes. 

The human-induced increase in the sediment runoff caused by enhanced erosion that resulted from extensive deforestation and land ploughing in the river basins of Europe. Two main such periods are distinguished the 5th century B.C.-the 5th century A.D. and the 16th-19th centuries. 

The river sediment in the project mainly comes from basins. According to the statistical analysis of Datong Station in the upper reaches during 1951-2011, the maximum sediment concentration is 3.24 kg/m, the minimum sediment concentration is 0.016 kg/m, and the mean sediment concentration is 0.428 kg/m. After the Three Georges Reservoir started to reserve water in 2003, the mean sediment runoff over the years has reduced from 0.14 billion tons before water reserving to 0.14 bilhon tons after water reserving. Before and after water reserving, the sediment concentration has reduced by about 50%. The bed load is fine sand, with 0.10-0.25 mm median particle diameter the median particle diameter of suspended sediment is about 0.01 nun. 

The second case (Table 2) illustrates a hypothetic urban stream receiving both metals and nutrients mainly via urban runoff. Since urban runoff is directly linked with rainfall episodes, metal inputs and exposure will be variable under base-flow during a rainy period and very low under a situation of water scarcity (low rain and low-flow). In this case, a sudden flow increase after strong rains may cause contrasting effects on water metal transport depending on the previous situation. If previous rains have already washed the metals retained in land and sediments, the... 

Pesticide immunoassays have been developed for a variety of pesticides and, more recently, GMOs, and have been used for matrices such as surface water, groundwater, runoff water, soil, sediment, crops, milk, meat, eggs, grain, urine and blood. ° Table 9 is a partial list of immunoassays for chemical pesticides developed since 1995 and includes notations on the matrices studied. A fairly comprehensive list of pesticide immunoassays developed prior to 1994 was provided by Gee et al2 ... 

RICEWQ was the first model developed for agrochemical runoff from paddy fields, incorporating aircraft application, dissipation by drift, adhesion on leaf surfaces, and dissipation from the leaf surface in addition to the processes affecting degradation and transport in sediment and paddy water. An important parameter, desorption from sediment to paddy water, is not considered, although this is not as important as other parameters in paddy fields such as sedimentation rate, behavior of SS, etc. 

Sedimentation basins can be used to collect and store surface water flow and to settle suspended solid particles. Seepage basins and ditches can be used to discharge uncontaminated or treated water downgradient of the site. It is important to separate clean surface runoff from contaminated water and store and treat them separately. Table 16.4 summarizes the surface water control methods. 

In the area of transport-type models, soil/water systems have been a primary area of development. The Hydrologic Simulation Program (18) described in the paper by Johanson simulates chemical movement and transformation in runoff, groundwater and surface water in contact with soil or sediments. 

The Agricultural Runoff Management (ARM) Model, developed by Hydrocomp Inc. for the U.S.EPA (2 ). It simulates the hydrology, sediment yield, and nutrient and pesticide behavior of the land phase of the hydrological cycle. The same organizations also developed the Non-Point Source (NPS) Model (3) which handles the washoff of miscellaneous pollutants from land surfaces. 

Transport rates for dissolved material are based on the internal and external fluxes (flows) computed in the hydrology section of the module. Soluble chemicals are transported down through the soil profile and are washed out into streams with surface runoff, interflow and groundwater flow. Sediment... 

The pesticide component of SWRRB takes into account the fate of the chemical applied under field conditions For example, the amount of pesticide actually reaching the ground after application over a plant canopy is calculated. Further, field dissipation of the chemical by photolysis on leaf surfaces as well as degradation in the soil is accounted for with the pesticide component of SWRRB. Leaching of the pesticide below the top 1cm of soil is also computed and runoff corrected for such losses. Further, adsorption of the pesticide to soil surfaces and sediment is taken into account by SWRRB. 

The data in Table V indicate that runoff of CGA-72662 from 12 applications would result in extremely low concentrations of CGA-72662 in ponds and lakes. The water column in all cases would contain all of the chemical, the sediment little or no CGA-72662. It follows from these data that exposure of CGA-72662 to aquatic organisms would be low. The data in Table V also shows that CGA-72662 would be persistent only in eutrophic lake environments. After the load is removed, the half-life of CGA-72662 in ponds, eutrophic lakes and oligotrophic lakes was 13, 62, and 5 days respectively. Self purification times were 9, 12, and 3 months respectively. 

Sources of lead in surface water or sediment include deposits of lead-containing dust from the atmosphere, waste water from industries that handle lead (primarily iron and steel industries and lead producers), urban runoff, and mining piles. 

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