Contaminants particle-bound

Terrestrial BMOs have also been widely used for monitoring environmental contaminants. In particular, the lipid-like waxy cuticle layer of various types of plant leaves has been used to monitor residues of HOCs in the atmosphere. However, some of the problems associated with aquatic BMOs apply to terrestrial BMOs as well. For example, Bohme et al. (1999) found that the concentrations of HOCs with log KoaS < 9 (i.e., those compounds that should have attained equilibrium) varied by as much as 37-fold in plant species, after normalization of residue concentrations to levels in ryegrass (Lolium spp.). These authors suggested that differences in cuticular wax composition (quality) were responsible for this deviation from equilibrium partition theory. Other characteristics of plant leaves may affect the amount of kinetically-limited and particle-bound HOCs sampled by plant leaves but to a lesser extent (i.e., <4-fold), these include age, surface area, topography of the surface, and leaf orientation. 

Because of the similarity of transport in biotilms and in stagnant sediments, information on the parameters that control the conductivity of the biofilm can be obtained from diagenetic models for contaminant diffusion in pore waters. Assuming that molecular diffusion is the dominant transport mechanism, and that instantaneous sorption equilibrium exists between dissolved and particle-bound solutes, the vertical flux ( ) through a stagnant sediment is given by (Berner, 1980)... 

Although Rs values of high Ks compounds derived from Eq. 3.68 may have been partly influenced by particle sampling, it is unlikely that the equation can accurately predict the summed vapor plus particulate phase concentrations, because transport rates through the boundary layer and through the membrane are different for the vapor-phase fraction and the particle-bound fraction, due to differences in effective diffusion coefficients between molecules and small particles. In addition, it will be difficult to define universally applicable calibration curves for the sampling rate of total (particle -I- vapor) atmospheric contaminants. At this stage of development, results obtained with SPMDs for particle-associated compounds provides valuable information on source identification and temporal... 

An additional comphcating factor with respect to air samphng rate calibration is the uncertainty associated with determinations of vapor-phase and particle sorbed concentrations of analytes by HiVol sampling. These systems suffer from artifacts such as the volatilization of particle-bound contaminants, insufficient retention of small particles, and adsorption of vapor-phase contaminants on the GFFs (Ockenden et al., 1998 Lohman et al., 2001). These artifacts may cause concentrations in the vapor-phase to be overestimated or underestimated, which results in sampling rates that are too low or too high. 

Due to their low solubility and hydrophobic nature, PAHs tend to be associated with particulate matter and accumulate in sediment. The contamination of PAHs in water is a complex phenomenon that involves various factors, such as water, suspended particulate matter (SPM) and sediment. Heemken et al. (2000) verified that 80-90% of the PAHs in the total water body is adsorbed to SPM, which emphasizes the importance of measuring particle-bound PAHs. However, the partition equilibrium between water and SPM is not usually available for wild situations due to weather, human activity and other impacts. 

Several studies have identified house dust as an important route of exposure for many chemical contaminants (Butte Heinzow, 2002 USEPA, 2004b). House dust is a sink for semivolatile organic compounds and particle-bound matter (Butte Heinzow, 2002). House dust and compounds adsorbed to it may enter the body by inhalation of suspended and resuspended particles, through non-... 

Atmospheric deposition of PCDD/Fs can be divided into three different forms dry gaseous deposition, dry particle-bound deposition and wet deposition (see Figure 1). Dry gaseous deposition is the diffusion of gaseous chemicals from the atmosphere to the plant surface. Dry particle-bound deposition occurs when particulate matter that contains the contaminant is deposited on the plant surface. Wet deposition can transport chemicals either in dissolved form, in particles trapped in the precipitation, or sorbed to the surface of water droplets or ice crystals. There are a multitude of forms of wet deposition, ranging from hail through rain to fog and dew fall. 

As described above, wet and dry particle-bound deposition are likely important for the accumulation of the higher chlorinated PCDD/Fs in aerial vegetation. The accumulation of particle-bound PCDD/Fs in plants is a function of a myriad of factors. The deposition rate itself is influenced by the particle size spectrum in the atmosphere and the distribution of the PCDD/Fs on the different particle size fractions, and further by the atmospheric turbulence, the canopy and plant properties, and the frequency and intensity of precipitation. The retention of the contaminants on the plant surface depends on the degree to which the particles are permanently retained on the plant and, for those particles which are not retained, the degree of transfer of PCDD/Fs from the particles to the plant cuticle. This is a very complex system that is not yet well understood. One approach that... 

The aim of our study was to complete our knowledge on the historical development of pollutant deposition in major basins of the central and southwestern Baltic Sea. The presented data are based on the analyses of selected heavy metals and organic contaminants in dated sediment cores. In detail, we want to supply information about namral backgrounds (heavy metals), time trends of concentrations, and comparisons of inventories of particle-bound pollutants for the whole period of anthropogenic impact (industrial time). 

House dust is a sink and reservoir for sernivolatile and particle-bound pesticides. Thus, it is a measure for the average contamination of an indoor environment. Pesticides found in house dust are those that are (1) stable in the indoor environment and (2) regularly applied in formulations to fight pests indoors. In contrast to an outdoor environment, where modern pesticides are degraded rather quickly by microorganisms, hydrolysis and UV hght, pesticides used indoors tend to be persistent [85]. Thus, they are a reservoir for chronic exposure. 

Contradictory results for associations between pesticide levels indoors (air, dust) and results form human biomonitoring may be due to different volatilities of the pesticides and may be determined by the magnitude in contamination levels. For semivolatile pesticides it may be easier to detect an association, as indoor air and house dust may serve for exposure in contrast to particle-bound pesticides with house dust as the only exposure path. Furthermore high contamination levels make it easier to detect an association, as with low indoor contamination levels associations may be hidden by the ubiquitous presence of pesticides in indoor environments and by nonindoor exposure pathways like dietary intake. 

In groundwater a vertical flux in the water unsaturated zone as well as a horizontal flux in the water saturated zone has to be stated and, consequently, an associated transport of dissolved and particle bound contaminants can be observed. Concurrently, corresponding aerobic and anaerobic zones have to be differentiated with respect to the microbial degradation processes. 

The assessment of the environmental impact of particle-bound contaminants, i.e. the development of sediment quality criteria (Chapter 6). 

Mobilization", in a wide sense, comprises changes in the chemical environment which usually are affecting lower rates of precipitation or adsorption - compared to "natural" conditions - rather than active releases of contaminants from solid materials. With respect to particle-bound metals, their solubility, mobility and bioavailability can be increased by five major factors in terrestrial and aquatic environments ... 

In case of hydrophobic compounds, which strongly adsorb to particles, e.g. pentabro-modiphenylether or 5 and 6 ring polycyclic aromatic hydrocarbons, special care is required to ensure complete extraction of the particle bound fraction. Separate analysis of SPM and of the liquid would be a good option. If it can be justified, for example, by consideration of contaminant partitioning, analysis of the SPM fraction as surrogate for whole water might be appropriate. Nevertheless, in water bodies with extremely low SPM content (<3mg/L) the dissolved fraction of those contaminants contributes significantly to the total concentration, and hence, has to be taken into account. 

A three-step approach was followed in the Rhine study (Heise et al., 2004), in which the hazards of substances of concern and of areas of concern could be determined with higher certainty than the areas which posed environmental risks to downstream sites. Description of the latter required the combined information from critical erosion thresholds, indications that resuspension took place and the extent by which particle bound contaminant concentrations exceeded risk thresholds. Addressing... 

Any calculations of such combinations of data with high variabilities, such as particle-bound contaminant loads in rivers, should consider these variabilities, which express themselves as uncertainties of specific data. 

Biocides are either semivolatile or non-volatile organic compounds. Since vapor pressures of non-volatile biocides, e.g. pyrethroids, are small, these biocides are mainly particle-bound. Their analysis in air might not be appropriate for the detection of indoor contamination, and the investigation of household dust may be used alternatively. Other biocides are semivolatile, e.g. chlorpyrifos, lindane (y-HCH) and penta-chlorophenol indoor contamination may be detected by analyzing either air or dust. 

As mentioned above, non-volatile biocides are mainly particle bound. Analysis of these compounds in dust seems to be superior to air analysis if indoor contamination is to be detected. 

Particles dropping out of the water column is a distinct process from burial of contaminants in the bed. Burial describes the removal rate of particle-bound toxic organics to deeper sediment layers from where they can no longer diffuse back into the water column. Burial is an important assimilation process for removing contaminants from biologically active zones. 

Electrokinetics stimulates microbial activity by electromigration of charged species, the electrophoretic translocation of particle-bound chemicals, and/or electroosmotic transport of uncharged molecules to active cells. Successful electroosmotic flushing has been applied to subsurfaces contaminated with, e.g., phenolic... 

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