Phenanthrene Sorption by Aliphatic-Rich Natural Organic Matter

Abstract

Contaminant sorption, an important process that may limit bioavailability, hinder remediation, encourage environmental persistence, and control mobility in the environment, has been the focus of numerous studies. Despite these efforts, the fundamental understanding of sorptive processes in soil and sedimentary environments has not been resolved. For instance, many have suggested that contaminants, such as polycyclic aromatic hydrocarbons (PAHs), solely interact with aromatic domains of organic matter. Until now, studies have neglected the aliphatic components that are known to be a recalcitrant and significant part of soil and sedimentary organic matter (SOM). In this investigation, the sorption of phenanthrene to several aliphatic-rich SOM samples was measured. The samples included the following: SOM precursors (algae, degraded algae, cellulose, collagen, cuticle, and lignin), two kerogen samples, and a highly aromatic humic acid. All samples were characterized by cross polarization magic angle spinning carbon-13 (CPMAS 13C) NMR and carbon, hydrogen, and nitrogen analysis. Batch experiments demonstrated that the highest organic carbon normalized sorption coefficients (Koc values) were obtained with the Pula kerogen sample (log Koc = 4.88) that only contains 6.5% aromatic carbon. Other aliphatic-rich samples, namely the Green River kerogen, degraded algae, and collagen samples produced comparable log Koc values (4.64, 4.66, and 4.72, respectively) to that of the highly aromatic humic acid (log Koc = 4.67). Phenanthrene uptake was the least for cellulose and lignin, two major soil components. A comparison of phenanthrene Koc values and paraffinic carbon content revealed a positive correlation (Koc = 798 +/- 96.1 * paraffinic carbon (%), r2 = 0.56) and indicates that amorphous polymethylene carbon is an important consideration in phenanthrene sorption. This study establishes that aliphatic SOM domains have a strong affinity for phenanthrene and likely, other PAHs. Therefore, aliphatic structures, that are an important component of SOM, require more attention in the examination of sorption processes in terrestrial and sedimentary environments.

Phenanthrene uptake by Medicago sativa L. under the influence of an arbuscular mycorrhizal fungus

“…The 13 C NMR spectral results obtained in the present study suggest that mycorrhizal colonization changes root surface and composition characteristics and this has important implications for the uptake of phenanthrene by plant roots because the association between hydrophobic pollutants and root components determines the surface sorption and transfer of hydrophobic pollutants into plant tissues. Numerous investigations have indicated that sorption of hydrophobic pollutants is regulated mainly by aromatic domains of organic matter (Chin et al, 1997;Chiou et al, 1998) although some other studies suggest a negligible contribution of aliphatic C (Salloum et al, 2002;Lin et al, 2007). Mycorrhizal roots had higher aromatic C and therefore their affinity for phenanthrene was higher than that of non-mycorrhizal roots with lower aromatic C, which is consistent with the observation of higher adsorption and lower desorption of phenanthrene by mycorrhizal roots.…”

Phenanthrene Sorption to Soil Humic Acid and Different Humin Fractions

“…Lipids can not only serve as a diagnostic index of soil biological activity, but also act as the dominant sorption domains in forest and agricultural soils (32,33). Linear sorption was found for phenanthene on lipid-modified clay (34).…”

Biosorption of phenanthrene by pure algae and field-collected planktons and their fractions

“…It was found that sorption capacity of HOCs was positively related to aromaticity of humic and fulvic acids (Perminova et al, 1999), and was negatively correlated with certain polarity indices of NOM derived from elemental ratios (Grathwohl, 1990;Xing et al, 1994). However, other investigators (Chefetz et al, 2000;Salloum et al, 2002) revealed that aliphatic carbon of NOM could significantly contribute to sorption of HOCs. From the above investigations, it is known that a few investigations have examined relationships of composition and structure of algae with the biosorption of HOCs.…”

“…The bulk market algal species, cultured algal species, and field-collected plankton samples have H/C ratios of 1.76-1.81, 2.26-2.28 and 1.88-2.13, respectively (Table 1), exhibiting a high aliphatic nature. Zelibor et al (1988) and Salloum et al (2002) reported that the H/C ratios varied slightly, ranging from 1.6 for Dunaliella tertiolecta and Scenedesmlus obliquus to 1.7 for Chlorella pyrenosidosa and Botnyococcus brautnii. The H/C ratio of C. pyrenosidosa is 1.7, lower than 2.28 for Chlorella in this study.…”