Sorption processes suspended solids

In most natural water, phosphine is very unstable and oxidizes even under anoxic conditions. Depending upon the redox potential of water, the oxidation products are diphosphine (P2H4), phosphorus, hypophosphorus acid, phosphorus acid, and phosphoric acid (Kumar et al. 1985). Based on soil studies (Berck and Gunther 1970 Hilton and Robison 1972), small amounts of phosphine may also be adsorbed (reversible sorption) or chemisorbed (irreversible sorption) to suspended solid and sediments in water. However, based on the estimated Henry s law constant (H) of 0.09 atm-m3/mol (see Table 3-3) and the expected volatility associated with various ranges of H, volatilization is expected to be the most important loss process for phosphine in water. 

The presence of suspended solid materials increases the extent of LAS biodegradation [13,28], but the rate of the process remains invariable. The influence of the particulate material is due specifically to the increased density of the microbiota associated with sediments. However, suspended solids may also reduce the bioavailability of IAS as a result of its sorption onto preferential sites (e.g. clays, humic acids), although this is a secondary effect due to the reversibility of the sorption process. Salinity does not affect IAS degradation directly, but could also reduce LAS bioavailability by reducing the solubility of this molecule [5], Another relevant factor to be taken into account is that biodegradation processes in the marine environment could be limited by the concentration of nutrients, especially of phosphorus and nitrogen [34],... 

Uptake is the process by which chemicals (either dissolved in water or sorbed onto sediment and/or suspended solids) are transferred into and onto an organism. For surfactants, this generally occurs in a series of steps a rapid initial step controlled by sorption, where the surface phenomenon is especially relevant then a diffusion step, when the chemical crosses biological barriers, and later steps when it is transported and distributed among the tissues and organs. 

Adsorption to particulate matter will transport disulfoton from water to suspended solids and sediment in water. The estimated organic carbon-adjusted soil sorption coefficient (K°<=) for disulfoton varies between 600 and 1,603 (Jury et al. 1987a Rao and Davidson 1982 Wauchope et al. 1992). This, range of K°= values suggests that disulfoton in water absorbs moderately to suspended solids and sediments (Swann et al. 1983), and this process may transport considerable amounts of disulfoton from water to particulate matter. 

Many processes are operative in the environment that contribute to the regional elimination of a contaminant by altering its distribution. Contaminants with sufficiently high vapor pressure can evaporate from contaminated terrestrial or aquatic compartments and be transferred through the atmosphere to new locations. Such processes of global distillation are considered largely responsible for the worldwide distribution of relatively volatile organochlorine pesticides such as lindane and hexachlorobenzene. Entrainment by wind and upper atmospheric currents of contaminant particles or dust onto which the contaminants are sorbed also contribute to contaminant redistribution. Sorption of contaminant to suspended solids in an aquatic environment with commensurate sedimentation can result with the removal of contaminants from the water... 

PROBABLE FATE photolysis photolysis to quinones is rapid, but is greatly hindered by adsorption, atmospheric and aqueous photolytic half-life 1-3 hrs, in the unadsorbed state, will degrade by photolysis from hours to days oxidation oxidation by alkyl peroxy radicals could compete with photolysis dissolved benzo (a) anthracene, photooxidation half-life in water 3.2-160 days photooxidation oxidation half-life in air 0.801-8.01 hrs hydrolysis not an important process volatilization to slow to compete with sorption as a transport process sorption very strong adsorption by suspended solids is the principal transport process, when released to water, will quickly adsorb to sediment or particulate matter biological processes short-term bioaccumulation is accompanied by metabolization, biodegradation is the principal fate, but occurs slowly... 

PROBABLE FATE photolysis dissolved portion should undergo rapid photolysis to quinones, when released to air, may undergo direct photolysis, although adsorption can slow this process, direct photolysis is important near surface of waters half-life for reaction with photo-chemically produced hydroxyl radicals 21.49 hr oxidation oxidation by chlorine and/or ozone could account for a small portion of the dissolved compound hydrolysis not an important process volatilization probably too slow to compete with adsorption as a transport process, evaporation may be important, but limited by adsorption, half-life 43 days sorption very strong adsorption onto suspended solids is the dominant transport process, adsorption in estuarine water 3 pg/L, 71% adsorbed on particles after 3 hr, after 3hr incubation in natural seawater, 75% of 2 pg/L adsorbed to suspended aggregates of dead photoplankton cells and bacteria biological processes bioaccumulation is short-term metabolization and microbial degradation are principal fates... 

PROBABLE FATE photolysis very little specific data, but photolysis may claim some of the dissolved compound, atmospheric and aquatic photolytic half-life 4.4-13 hrs, subject to near surface, direct photolysis with a half-life of 4.4 hrs, if released to air, it will be subject to direct photolysis, although adsorption may affect the rate, reaction with photochemically produced hydroxyl radicals gives an estimated half-life of gas phase crysene of 1.25 hrs oxidation chlonne and/or ozone in sufficient quantities may oxidize chrysene, photooxidation half-life in air 0.802-8.02 hrs hydrolysis not an important process volatilization probably too slow to compete with adsorption as a transport process, will not appreciably evaporate sorption adsorption onto suspended solids and sediment is the dominant transport process if released to soil or to water, expected to adsorb very strongly to the soil biological processes short-term bioaccumulation, metabolization and biodegradation are the principal fates... 

PROBABLE FATE photolysis the dissolved portion of the compound may undergo rapid photolysis to quinones, atmospheric and aqueous photolytic half-lives 6 hrs-32.6 days, may be subject to direct photolysis in the atmosphere, reaction with photochemically produced hydroxyl radicals has a half-life of 1.00 days oxidation rapid oxidation by chlorine and/or ozone may compete for dissolved DBA, photooxidation half-life in air 0.428-4.28 hrs hydrolysis not an important process volatilization probably too slow to be important, rate uncertain sorption strong adsorption by suspended solids, especially organic particulates, should be the principal transport process biological processes bioaccumulation is short-term, metabolization and microbial biodegradation are the principal fates... 

PROBABLE FATE photolysis insufficient data, but photolysis may be very important, atmospheric and aqueous photolytic half-lives 21 hrs-2.6 days, in the unadsorbed state, it will degrade by photolysis with a half-life of a few days to a week oxidation chlorine and/or ozone in sufficient quantities may oxidize fluoranthene, photooxidation half-life in air 2.02-20.2 hrs hydrolysis not an important process volatilization not an important transport process sorption adsorption onto suspended solids and sediments is probably the dominant transport process, when released to water, it will quickly adsorb to sediment and particulate matter in the water... 

PROBABLE FATE photolysis, photodissociation in stratosphere may be important, not important in aquatic environment, photooxidation half-life in air >7.3->73 yrs photooxidation by U.V. in aqueous medium 90-95 C time for the formation of C02 (% theoretical) 25% 25.2 hr, 50% 93.7 hr, 75% 172.0 hr oxidation not an important process hydrolysis probably unimportant volatilization some volatilization occurs, importance as a fate mechanism is unknown, measured half-life for evaporation from 1 ppm aqueous solution 25 C, still air, and an average depth of 6.5 cm 40.7 min, should volatilize slowly from dry soil surfaces, if released to water, volatilization appears to be the most dominant removal mechanism (half-life 15 hrs from a model river) sorption no data available, moderate to slight adsorption to suspended solids and sediments may occur biological processes high Log Kow indicates possibility of bioaccumulation... 

The concentration, behavior, and eventual fate of an organic compound in the aquatic environment are determined by a number of physico-chemical and biological processes. These processes include sorption-desorption, volatilization, and chemical and biological transformation. Solubility, vapor pressure, and the partition coefficient of a compound determine its concentration and residence time in water and hence the subsequent processes in that phase. The movement of an organic compound is largely dependent upon the physico-chemical interactions with other components of the aquatic environment. Such components include suspended solids, sediments, and biota. 

The clay fraction, which has long been considered as a very important and chemically active component of most solid surfaces (i.e., soil, sediment, and suspended matter) has both textural and mineral definitions [22]. In its textural definition, clay generally is the mineral fraction of the solids which is smaller than about 0.002 mm in diameter. The small size of clay particles imparts a large surface area for a given mass of material. This large surface area of the clay textural fraction in the solids defines its importance in processes involving interfacial phenomena such as sorption/desorption or surface catalysis [ 17,23]. In its mineral definition, clay is composed of secondary minerals such as layered silicates with various oxides. Layer silicates are perhaps the most important component of the clay mineral fraction. Figure 2 shows structural examples of the common clay solid phase minerals. 

Precipitation refers to dissolved species (such as As(V) oxyanions) in water or other liquids reacting with other dissolved species (such as Ca2+, Fe3+, or manganese cations) to form solid insoluble reaction products. Precipitation may result from evaporation, oxidation, reduction, changes in pH, or the mixing of chemicals into an aqueous solution. For example, As(V) oxyanions in acid mine drainage could flow into a nearby pond and react with Ca2+ to precipitate calcium arsenates. The resulting precipitates may settle out of the host liquid, remain suspended, or possibly form colloids. Like sorption, precipitation is an important process that affects the movement of arsenic in natural environments and in removing arsenic from contaminated water (Chapters 3 and 7). 

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