Effect of aging on the bioavailability of toluene sorbed to municipal solid waste components

The bioavailability of toluene sorbed to individual municipal solid waste (MSW) component [office paper, newsprint, model food and yard waste, high density polyethylene (HDPE) and poly(vinyl chloride) (PVC)] was evaluated. Effects of sorbent decomposition on toluene bioavailability were studied by evaluating biodegradable sorbents in both fresh and anaerobically decomposed form. To determine the effect of aging on toluene bioavailability, bioavailability tests were performed for MSW components that were in contact with toluene for 1, 30, and 180 days. At the termination of bioavailability test, sequential organic solvent extraction, alkali extraction, and combustion were used to determine the fate of toluene that was not available to bacteria. Lignocellulosic waste (fresh and degraded office paper, newsprint) was subjected to enzymatic hydrolysis and acid hydrolysis to determine the effect of individual biopolymers in paper on the sorption and bioavailability of toluene.; The bioavailability of toluene sorbed to MSW components was highest in HDPE, a rubbery polymer, followed by the biopolymers and finally PVC, a glassy polymer. Except for HDPE, aging significantly reduced the bioavailability of toluene sorbed to MSW components. Relative to the 1-day aging time, the bioavailability of toluene sorbed to biopolymers was reduced by 11–22% and 12–29% after 30 and 180 days of aging, respectively. For fresh and degraded office paper, the reduced bioavailability was a combination effect of aging and pH increase. Analysis of solid phase at the termination of bioavailability tests indicated that the remaining 14C in sorbents was sequestered within and/or covalently bound to sorbent organic matter. Stronger association between sorbent organic matter and 14C was observed during aging as less 14C was recovered by organic solvent extraction and more 14C was detected in the humic substances when aging time increased. Large molecular weight substances in the humic matter may form covalent binding with toluene and/or intermediates of toluene biodegradation. Humic acid had 3.7–24.3 times higher affinity for toluene than fulvic acid.; Enzymatic hydrolysis and bioavailability tests were conducted to identify the effect of individual biopolymers in paper on toluene sorption. Toluene release from cellulose and hemicellulose was not enhanced after enzyme addition, indicating that cellulose and hemicellulose exhibited limited sorptive capacity for toluene. Lignin controlled toluene sorption and bioavailability for both fresh and degraded newsprint. Bioavailability tests showed no significant difference between toluene sorbed to biopolymer composite (fresh and degraded newsprint) and their isolated lignins. However, the presence of lignin could explain only 54% of the sorption capacity of degraded office paper. Bioavailability of toluene sorbed to degraded office paper lignin showed a higher initial biodegradation rate and mineralization extent than toluene sorbed to degraded office paper composite. Crude protein and lipophilic extractives were likely to contribute to the higher sorptive capacity of biopolymer composite. Lipophilic extractives provided highly hydrophobic environment for toluene uptake and caused the declined toluene bioavailability.