Importance of Sporopollenin Structure and Accessibility in the Sorption of Phenanthrene by Biota Spores and Pollens

Abstract

Although spores/pollens are so abundant and ubiquitous in the environment, the role of these natural organic matter concerning fate and transport of organic pollutants in the environment is neglected. Lipid-free fractions and sporopollenins were isolated from seven spores/pollens collected from lower and higher biota species and were characterized by elemental analysis, CO2 adsorption techniques, and advanced solid-state 13C nuclear magnetic resonance spectroscopy. Then, the sorption isotherms of phenanthrene (Phen) on all the samples were investigated by a batch technique. The sporopollenins were a highly cross-linked polymer including alkyl carbon, poly(methylene) carbon, and aromatic carbon as well as oxygen functionalities; additionally, their sorption capacities (Koc) for Phen reached up to 1 170 000 mL/g, suggesting that some of the sporopollenins were good biopolymeric sorbents for the removal of hydrophobic organic contaminants in aquatic media. A highly significant and positive correlation between the sorption capacity of Phen and the aliphaticity of the sporopollenins suggested that their structure was critical to Phen sorption. Meanwhile, the (O + N)/C atomic ratios and polar groups were significantly and negatively correlated with the sorption capacity of Phen, indicating that accessibility also played a significant role in the sorption process. Moreover, variable correlations between the sorption capacities (Koc) and the micropore volumes of the spore/pollen fractions were observed. This study sheds light on the importance of the polarity, microporosity, and structure of sporopollenins in the sorption process of Phen.