AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Contribution of water-soluble and insoluble species and their hydrophobic/hydrophilic sub-fractions in the toxicological properties of ambient atmospheric aerosols
VISHAL VERMA, Neel Kotra, Laura King, Jiumeng Liu, Roberto Rico-Martinez, Terry Snell, Rodney Weber, Georgia Institute of Technology
Abstract Number: 175 Working Group: Health Related Aerosols
Abstract The present study assesses the relative contributions of water soluble and insoluble compounds and their hydrophobic/hydrophilic sub-fractions in the toxicological properties of ambient fine aerosols (D$_p<2.5 micro-meter). Toxicity of the particulate matter (PM) was measured by both chemical (dithiothreitol; DTT assay) and biological methods [acute toxicity test using aquatic organisms - Brachionus calyciflorus (rotifers)]. The particles were collected at an urban site near downtown Atlanta using a high-volume sampler and were extracted in both water and methanol. Hydrophobic and hydrophilic fractions of the PM were segregated by passing the extracts through a C-18 column. The responses of both toxicity assays (DTT and rotifers) were significantly higher for the methanol extract than water extract. A substantial fraction of aerosol toxicity was associated with the hydrophobic compounds as evident from a remarkable attenuation in DTT response (~60 % for water and ~75 % for methanol extract) after passing the PM extracts through C-18 column. The DTT activity of water and methanol extracts were correlated with WSOC (water soluble organic carbon; R = 0.86) and WIOC (water insoluble organic carbon; R = 0.94) content of the PM, respectively. Brown carbon (BrC) content of the PM, which predominantly represents the hydrophobic organic fraction, was also correlated with DTT activity of both the water (R=0.78) and the methanol extracts (R=0.83). Conversely, regression results of the rotifers assay didn’t yield any consistent association with the measured PM constituents. However, considerable reductions (>90%) were obtained in the rotifers mortality also by removing the hydrophobic PM species. These findings suggest that the hydrophobic components of both the water-soluble and the insoluble organic aerosols contribute substantially to the ambient PM toxicity and could have significant ecological impacts (e.g. on rotifers and other important animals in aquatic food webs). More research should be focused on this fraction than done in the toxicological studies conducted so far.