Heavy suspended sediment

Lee, S., Moon, J. W., and Moon, H. S. (2003). Heavy metals in the bed and suspended sediments of Anyang River, Korea Implications for water quality. Environ. Geochem. Health 25, 433—452. 

Turbidity currents—Local, rapid-moving currents that result from water heavy with suspended sediment mixing with lighter, clearer water. Causes of turbidity currents are earthquakes or when too much sediment piles up on a steep underwater slope. They can move like avalanches. 

Water samples were taken from the recreational lakes using polypropylene sample containers which had been acid soaked. The water was filtered over 0.22 pm Millipore filters, and the suspended sediment collected for metal analyses. Heavy metal analyses were also done in the meat portion of the most common fish found in the recreational lakes, i.e. Tilapia nilotica. The fish were caught without baits to avoid contact contaminating their internal organs. 

Tab.5. Heavy metals in fish meat (Tilapia nilotica) and suspended sediments taken from 2 recreational lakes within Kuala Lumpur City ()rgg )...

The natural radionuclides Th and Be are good tracers for the transport and sources of particles in the suspended sediment reservoir. In the Hudson River estuary, Th is produced from the decay of dissolved which varies linearly with salinity, while Be is added directly to the estuary from the atmosphere (Fengetal. 1999). Samples in the Hudson under conditions of low and high river flow show that Th/ Be activity ratio in suspended sediment increases from low salinity to higher salinity waters. The distribution of heavy metals in the suspended sediment reservoir can be compared with that of Th/ Be activity ratio by normalizing the metals to Fe, and therefore iron and aluminum in suspended sediments of the Hudson can be used to normalize grain-size effects on specific concentrations of metals. 

Flocculation and sedimentation arc two processes used to separate waste streams that contain both a liquid and a solid phase. Both are well-developed, highly competitive processes, which arc oflcii used in the complete treatment of waste streams. They may also be used instead of, or in addition to, filtration. Some applications include the removal of suspended solid particles and soluble heavy metals from aqueous streams. Many industries use both processes in the rcmowal of pollutants from their wastewaters. These processes work best when the waste stream contains a low concentration of the contaminating solids. Although they are applicable to a wide variety of aqueous waste streams, these processes arc not generally used to treat nonaqueous or semisolid waste streams such as sludges and slurries. 

It is seen from the contents of heavy metals in stream sediments, soils and suspended matters for the main basins of the Anhui section of the Yangtze River that the contents of heavy metals in suspended matters are obviously higher than those in stream sediments and soils, indicating that the suspended matters are the main carriers for long distance migrations of heavy metals in the Yangtze River basin. 

The process of diffusion of heavy metals in seawater depends on their state. The dissolved fraction of heavy metals (ip) takes part in the biogeochemical processes more intensively than suspended particles (e). But unlike suspended particles, the heavy metals fall out more rapidly to the sediment. A description of the entire spectrum of these processes in the framework of this study is impossible. Therefore, block MMT describes processes that can be estimated. The transport of heavy metals in seawater includes absorption of the dissolved fraction ip by plankton (11%) and by nekton (H%), sedimentation of the solid fraction (//) ), deposition with detritus (11%), adsorption by detritophages from bottom sediments (Iff), and release from bottom sediments owing to diffusion (Hef). As a result, the dynamic equations for heavy metals become ... 

In rivers and streams heavy metals are distributed between the water, colloidal material, suspended matter, and the sedimented phases. The assessment of the mechanisms of deposition and remobilization of heavy metals into and from the sediment is one task for research on the behavior of metals in river systems [IRGOLIC and MARTELL, 1985]. It was hitherto, usual to calculate enrichment factors, for instance the geoaccumulation index for sediments [MULLER, 1979 1981], to compare the properties of elements. Distribution coefficients of the metal in water and in sediment fractions were calculated for some rivers to find general aspects of the enrichment behavior of metals [FOR-STNER and MULLER, 1974]. In-situ analyses or laboratory experiments with natural material in combination with speciation techniques are another means of investigation [LANDNER, 1987 CALMANO et al., 1992], Such experiments manifest univariate dependencies for the metals and other components, for instance between different metals and nitrilotriacetic acid [FORSTNER and SALOMONS, 1991], but the interactions in natural systems are often more complex. 

Fig. 8-21. PLS modeling of the consequences of changes in pH, phosphate concentration, and suspended material content on the concentrations of heavy metals in the system river water/ river sediment...

Bottom sediments in the coastal zone of the sea may be polluted with copper, zinc, nickel and cadmium. The highest levels of toxic heavy metals are found in the mouths of rivers. The bottom sediments in the Black Sea have a high mercury level—from 0.28 to 0.40 pg/1. In the coastal waters of the Krasnodar Territory the mercury level is 0.15-1.55 pg/1, while its maximum concentrations are registered in the Danube and Dnieper mouth areas. The Danube alone brings annually up to 50-60 tons of mercury, while the Dnieper brings up to 5 tons. The distribution of heavy metals in bottom sediments in the Russian shelf of the Black Sea is not uniform. Their greatest quantities are accumulated in sediments in the deepest part of the shelf where their concentration is 3-5 times higher than in sediments in the shallower part. Toxic metals contained in sea water in the dissolved and suspended forms are ac-... 

Experimental. The sediment used in this study was obtained from Colma Creek, at Serramonte Boulevard between El Camino Real and Junipero Serra Boulevard, in the city of Colma, San Mateo County, California. Colma Creek was chosen because its entire course occurs within an area of urbanization, and the sediments are therefore of the type which normally come in contact with lead and other heavy metals. The main sources of lead, atmospheric fallout and rainfall runoff contain particulate matter from automobile exhaust emissions. Several shovels full of the bottom material were placed in a plastic container. In the laboratory, several kilograms of the material were wet-sieved, and the fraction passing through a 200-mesh sieve (particle diameter less than 74 ym) was placed in a 1-liter graduated cylinder containing a 1 M sodium phosphate solution. The silt fraction settles in this medium while the finer clay particles remain suspended. After several hours, this clay suspension was then decanted and a portion of the material saved for X-ray diffraction, as were portions of the sand and silt fractions. 

The catalyst is keyed to most of the hydrodesulfurization processes and tailored for a speciflc oil. Some catalysts can tolerate deposition of large quantities of heavy metals while maintaining high desulfurization activities. Other catalysts need plugging protection against suspended salts and particulates in the feedstock. To protect flxed-bed catalysts these sediments are removed before they enter the desulfurization reactor. 

In aquatic environments, the heavier and less vola-tile/soluble compounds in crude oil will adsorb to suspended solids and subsequently settle in the sediments. Some heavy fractions with high density may sink into the sediment. This happens after the initial removal of the smaller and more volatile chemicals by either dissolution or volatilization. This is followed by biodegradation of those crude oil constituents that can serve as a food source for bacteria. Biodegradation is a significant mechanism for removal of hydrocarbons released into the environment. However, this generally occurs on the order of months and years. It is not believed that there is significant bioaccumulation of petroleum hydrocarbons in aquatic organisms. 

From a geochemical point of view, there are several options to investigate the present state and the development of, for example, the distribution and concentration of contaminants in the water column, suspended particulate matter, biota, and sedimentary deposits. Commonly, for most of the environmentally relevant substances (heavy metals, persistent organic pollutants, and nutrients) sediments are considered the final sinks following partly complicated pathways of transport, transformation, enrichment in the food chains, deposition, and burial. 

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