The Need for Passive In Situ Samplers

To aid in assessing the risks associated with large numbers of environmental contaminants, quantitative-structure-activity relationships (QSARs) have been developed covering nearly all biological effects or other endpoints in both aquatic and terrestrial species (Connell, 1990). QSARs relate chemical structural 

Although QSARs, QSPRs, and MMMs generate screening data, which provide a much-improved focus on the risks associated with environmental contaminants, organism exposure must be confirmed by direct determination of contaminant identities and measurement of concentrations in water or air or estimated 

In cases where water is turbid, samples are generally filtered through glass fiber Alters (GEE) prior to percolation through sorbents. This step recovers waterborne particulates and microorganisms with average diameters 0.7 pm, which are analyzed separately. However, chemicals associated with colloid-sized particulates and DOC are not removed by GFFs. 

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. 

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