The structural makeup of natural organic matter plays a major role in regulating its capacity to retain nonionic hydrophobic organic compounds (HOCs). We used a model HOC--phenanthrene--to investigate the correlations between sorption capacity, specifically the modified Freundlich coefficient (K'f), and compositional data of humic acids, humins, and a peat obtained from quantitative 13C solid-state NMR spectroscopy. A positive correlation between K'f and the weight fraction of amorphous poly(methylene) in the sorbents was observed. In contrast, the correlation between phenanthrene sorption capacity and aromaticity or polarity indices of the sorbents was insignificant. The nonpolar aliphatic carbon fraction, excluding poly(methylene), was only partially correlated with K'f. Detailed NMR analyses of the sorbents using 1H inversion-recovery experiments showed that 10-nm diameter domains of branched nonpolar aliphatic groups, which account for 20-50% of all nonpolar aliphatic segments and may be associated with the poly(methylene), were responsible for the partial correlation. The correlation between K'f and the amorphous nonpolar aliphatic domains including amorphous poly(methylene) was strong. The rubbery, relatively low-density, and amorphous nonpolar aliphatic domains can be expected to offer an excellent environment for the sorption of phenanthrene by partitioning. These observations suggest that the domains of amorphous poly(methylene) and branched nonpolar aliphatics, which make up 2-9 wt % of the organic fraction in our samples, may serve as good descriptors for the potential of natural organic matter to retain HOCs in the natural environments.

We extracted the acid-soluble portion of municipal biosolids, fractionated it by both molecular weight (MW) and hydrophobicity, and used various solid-state nuclear magnetic resonance (NMR) methods and diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy to characterize the fractions. Spectroscopic characterization of the MW components of the biosolids-derived organic matter fractions revealed the presence of functionally distinct groups of compounds. Quantitative 13 C NMR, CH spectral editing, and several two-dimensional NMR experiments show that the high-MW hydrophilic fraction in particular is structurally simple, consisting predominantly of N-acetylated polysaccharides, perhaps derived from bacterial peptidoglycans. In the high-MW hydrophobic fraction, aromatic compounds were present in addition to the N-acetylated polysaccharides. Infrared spectroscopy confirmed that hydrophilic fractions were dominated by carbohydrates and indicated that the lower-MW fractions lacked amide moieties. Complementary interpretations of the DRIFT and NMR spectra improved our knowledge of the components separated by this fractionation scheme, allowing better characterization of biosolids organic matter. Moreover, fractionation based on both MW and hydrophobicity may prove useful in detailed characterization of the structure of biosolids-derived organic matter and other similarly heterogeneous natural organic matter in soils and sediments.

Despite increasing interest in the short-term effects of airborne environmental contaminants, experimental findings are generated at a very slow pace. This is due in part to the expense and complexity of most environmental chambers, which are needed for quantifying effects of wholebody exposures. We lessened this obstacle by designing, constructing, and testing a single-pass, 10-m3 stainless-steel chamber. Compressed air is purified before being sent to an air dilution olfactometer, which supplies 1000 L (1 m3) per minute (referenced to STP) while maintaining 40% relative humidity (RH) and 22.6 degrees C. Precise control of all stimulus parameters is greatly simplified since air is not recirculated. Vapor-phase odorant concentrations are achieved by varying the proportion of total airflow passing through one or more saturators, and are verified in real time by an infrared (IR) spectrometer. An adjoining 5-m3 anteroom is used for introducing known intensities of more chemically complex vapor and/or particulate stimuli into the chamber. Prior to the point that air is exhausted from the chamber, all components are made of stainless steel, Teflon, or glass. A LabView program contains feedback loops that achieve document chamber conditions and document performance. Additional instrumentation and computer systems provide for the automated collection of perceptual, respiratory, eye blink, heart rate, blood pressure, psychological state, and cognitive data. These endpoints are now being recorded, using this facility, in response to ranges of concentrations of propionic acid and environmental tobacco smoke.