Sediments retention

Measurements of S cycling in Little Rock Lake, Wisconsin, and Lake Sempach, Switzerland, are used together with literature data to show the major factors regulating S retention and speciation in sediments. Retention of S in sediments is controlled by rates of seston (planktonic S) deposition, sulfate diffusion, and S recycling. Data from 80 lakes suggest that seston deposition is the major source of sedimentary S for approximately 50% of the lakes sulfate diffusion and subsequent reduction dominate in the remainder. Concentrations of sulfate in lake water and carbon deposition rates are important controls on diffusive fluxes. Diffusive fluxes are much lower than rates of sulfate reduction, however. Rates of sulfate reduction in many lakes appear to be limited by rates of sulfide oxidation. Much sulfide oxidation occurs anaerobically, but the pathways and electron acceptors remain unknown. The intrasediment cycle of sulfate reduction and sulfide oxidation is rapid relative to rates of S accumulation in sediments. Concentrations and speciation of sulfur in sediments are shown to be sensitive indicators of paleolimnological conditions of salinity, aeration, and eutrophication. 

Vorosmarty, C. J., Meybeck, M., Feteke, B., Sharma, K., Green, P., and Syvitski, J. P. M. (2003). Anthropogenic sediment retention major global impact from registered river impoundments. Glob. Planet. Change i9, 169—190. 

Gacia, E., and Duarte, C. M. (2001). Sediment retention by a Mediterranean Posidonia oceanica meadow The balance between deposition and resuspension. Estuar. Coast. Shelf Sd. 52, 505—514. 

Reduction plays a major role in the behavior of iron and manganese as well as in the behavior of pollutant chemicals in the environment. The solids Fe(OH)3 and Mn02 are strong adsorbents of many chemicals, especially metals. When particles of these oxides form in, or are transported into, surface waters, they can sorb metals the suspended particles may then be removed from the water column by settling, as previously discussed. Such a process may lead to either temporary or long-term deposition of the metals into the sediment. Retention in the sediment is only short term if iron reduction and manganese reduction subsequently lead to dissolution of the oxides and release of the metals back into the water column. 

Transport to passive sed = Sedimentation rate Amount in active sediments Retention rate in active sediments Benthic uptake = Benthic uptake rate Amount in active sediments... 

In aU of these functions, the geosynthetic is acting in one of two unique ways either it is actively controlling the dislodgement of soil, called erosion control, or it is intercepting and filtering the dislodged soil, called sediment, out of suspension once it has been transported by mnoff, called sediment control or sediment retention. 

Advantages of geosynthetic-enhanced erosion control products and sediment retention devices... 

The benefits of geosynthetic-enhanced erosion control products (ECPs) and sediment retention devices (SRDs) over traditional or natural systems include ... 

Erosion control product and sediment retention device performance criteria... 

Filtration efficiency and flow ASTM D5141, Standard Test Method for Determining Filtering Efficiency and Flow Rate of the Filtration Component of a Sediment Retention Device Using Site-Specific Soil ... 

Large-scale performance tests have been developed to simulate expected field conditions to report performance properties of as-instaUed ECPs and SRDs. Standardized, large-scale tests have been developed for slope and channel erosion, as well as for several sediment retention applications. Products are installed per the product manufacturer s published installation recommendations. The results of these tests indicate actual field performance and are acceptable for use in performance specifications and often in design calculations. 

ASTM D7351, Standard Test Method for Determination of Sediment Retention Device Effectiveness in Sheet Flow Applications ... 

Seepage thru BMP versus sediment retention by BMP Unpaved BMPs Paved BMPs... 

Independent erosion control blanket and sediment retention device data... 

Sprague, C.J., Lacina, B., 2010. Performance Testing of Sediment Retention Devices, Conf XXXI, International Erosion Control Association, Dallas, TX (digital proceedings). 

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