Suspended sediment/water partition coefficient

The suspended sediment/water partition coefficients have been measured for 19 chlorinated organics in 25 samples from the St. Clair, Detroit and Niagara Rivers. An excellent linear correlation (r = 0.87) between the organic-carbon corrected partition coefficient (Kqq) and the octanol/water partition coefficient (Kq, ) was found (log = 0.76 log + 1.66). Using this equation plus another equation developed in this paper it is shown that the percentage of chemical in the dissolved and particulate phases in the study rivers could be estimated from a chemical s to within a factor of two. The paper also discusses the time required for equilibrium to be achieved between the dissolved and particulate phases, and the potential importance of biota such as algae in the partitioning process. 

Partitioning, suspended sediment/water partition coefficient, Kp, organic-carbon corrected partition coefficient, Kq(, octanol/water partition coefficient, chlorinated hydrocarbons, Kq /Kq, correlations, St. Clair River, Detroit River, Niagara River. 

PBDEs adsorb strongly onto suspended solids and sediments in the water column. Volatilization of PBDEs from water surfaces will be attenuated by adsorption, and thus is notan important fate process. Sediment-water partition coefficients (K,) have been measured for several components of commercial... 

It is also assumed that hydrophobic organic chemicals partition only into the organic matter in soils, sediment, and suspended sediment. Further, the organic matter in soils and sediment is not as well represented by octanol as is the lipids in biota. Empirically it has been found that the organic carbon (in soils and sediment)-water partition coefficient, Kocy/ u defined as... 

The BUSES model provides an estimate of the organic carbon/water partition coefficient (Koc) based on the octanol/water partition coefficient (Kow)- From these data, it is evident that the methyltins are less likely to partition onto organic carbon (in sediments, soils, biota) than are the butyl- and octyltin compormds due to then-lower partition coefficients and higher water solubilities. The 7/oc value can then be used to derive sohds/water partition coefficients in suspended matter, in sediment, and in soil using values of 10%, 5%, and 2% for organie carbon, representing typical organic carbon contents of suspended matter, sediment, and soil, respeetively. 

Winters and Lee134 describe a physically based model for adsorption kinetics for hydrophobic organic chemicals to and from suspended sediment and soil particles. The model requires determination of a single effective dififusivity parameter, which is predictable from compound solution diffusivity, the octanol-water partition coefficient, and the adsorbent organic content, density, and porosity. 

The SPs have been shown to be highly toxic to fish and aquatic invertebrates, particularly arthropods, with toxicities as low as the nanogram per liter range in laboratory studies (see Sect. 3). However, due to their high lipophilicity and octanol water partition coefficient (Koc) values, they are rapidly adsorbed to suspended and bottom sediments [1], effectively limiting the exposure of water column organisms. 

The partitioning of 1,3-DNB in water between water and the suspended solid and sediment has been estimated. Simulation studies based on the octanol-water partition coefficient predict that >99% of... 

DNB will remain in the water column and <1% will be adsorbed to suspended solid and sediment (ERA 1991b). 1,3,5-TNB with an octanol-water partition coefficient value lower than 1,3-DNB (see Table 3-2), is expected to exist almost exclusively in the water column. 

Servos, M.R., Muir, D.C.G. (1989b) Effect of suspended sediment concentration on the sediment to water partition coefficient for... 

Any of these solution products can react with chemical species already present in the water, such as humic substances, metals, and metal complexes. As for the rest of the dissolved ammonia, while some will bind to sediments, suspended partieles, and organic matter available in the water, most will undergo nitrification by the Nitrosomonas and Nitrobacter bacteria species to yield nitrates that can be uptaken by aquatic plants and organisms. Many algae and phytoplankton have been found to utilize ammonia direetly as their source of nitrogen. Because of its low octanol/water partition coefficient, ammonia is not expected to adsorb strongly to sediments. 

PCDDs and PCDFs have very little solubility in water and exhibit a strong lipophilic character, as shown in Table 21.1 by the high values of n-octanol-water partition coefficients Kow). Therefore, these compounds display strong affinity for sediment, and, consequently, their presence as solute in water is always even lower than solubility in fact, they are associated with the sediment, both suspended and settled. PCDDs and PCDFs are considered semivolatile substances the chemicophysical properties of the seventeen toxic congeners are reported in Table 21.1. 

Because PAHs exhibit a range in lipophilic affinity, elimination that relies solely on passive diffusion loss should be slower for the more hydro-phobic PAHs. Such a correlation has been shown for the freshwater amphi-pod [Diporeia spp. (Pontoporeia hoyi)], which does not metabolize PAHs to any appreciable extent (Landrum 1988). This author found that for a series of PAHs with increasing octanol-water partition coefficients, the elimination constant decreased, which led to longer half-lives. The more water-soluble PAHs phenanthrene, anthracene, and fluoranthene showed nearly identical rapid elimination patterns (/./, 2 d) in mussels (Mytilus edulis) exposed to contaminated suspended sediments for 28 d, while the more hydrophobic PAHs produced half-lives in the range of 4-6 d (Fig. 8 see Table 2) (Lake et al. 1985). The most hydrophobic of the group, pery-lene, displayed the slowest elimination. 

The observed concentration ranges of TBT in sediment or SPM in Dutch open waters and 19 Dutch harbours are shown in Table 2. The highest observed TBT-Sn concentration in Dutch harbours was a factor 30 higher than the highest TBT-Sn concentrations in open waters. The lowest TBT concentrations were more or less in the same range. In order to normalise the sediment and suspended matter concentrations to water concentrations a value for the (organic carbon partition coefficient) needs to be estimated. From the distribution of measured sediment and... 

Adsorption refers to the collection of organic compounds on the surfaces of particles, such as soil or suspended sediment. Most of these particles are covered with a layer of organic material thus, the adsorption results from the attraction of two organic materials for one another. Adsorption is measured by a partition coefficient, which is the ratio of the concentration of the compound on the solid to its concentration in the water surrounding the solid ... 

HHCB/AHTN ratios in Lippe river sediments are significantly lower (average 1.2) than in Lippe river water samples (average 2.9). Accordingly, AHTN is enriched in the sediments. Winkler et al. (1998) investigated musk concentrations in water and suspended particulate matter (SPM) from the Elbe river. They found a HHCB/AHTN ratio of about 1 in SPM, whereas river water analysis showed a HHCB/AHTN ratio of about 2 (which is also illustrated by the higher partition coefficient... 

The second Important process to consider Is physical loss of a transient by partitioning into sediments on the bottom or suspended particles In the water column. The potential significance of this loss term Is demonstrated In Figure 5, a plot of the log of the partition coefficients between octanol and water (log F) for almost 20,000 industrial compounds. The narrow distribution of these coefficients Is striking, the more so In the context of Figure 6. 

The role of water column particles in capturing dissolved trace elements has been known for a long time (e.g., Schindler, 1975). The practical significance of this was demonstrated by Santschi (1984), who showed how the water column residence times of trace elements could be predicted from the particle flux. The simplest model which links fluxes of particles, supply of trace elements, and capture by sediments, is that of Schindler (1975). At the heart of the model is the distribution coefficient, (sometimes referred to as the partition coefficient), which quantifies the relationship between the dissolved and particulate concentrations. Most subsequent formulations of the model are built around this concept (e.g., Imboden et al, 1980 Diamond etal., 1990 Hilton et al. 1995 Appleby, 1997). These models all assume reversible sorption of dissolved elements to particle surfaces. This simplistic view is broadly supported by recent studies of suspended particles in rivers (Findlay et al., 1996 Ferriera et al., 1997) and more rigorous chemical models of binding (e.g.. Lofts Tipping, 1998). 

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. 

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