PARENT SESSION

MP7 Global Fate of POPs
Room 18C/D, Level 4
2:10 PM - 5:30 PM, Monday, 10 November 2003
Chair: Lohmann, Rainer ,
Co-chair: Dachs, Jordi ,

(142) Does adsorption to black carbon dominate the partitioning of persistent organic pollutants?

Lohmann, R^{1, 2, 3}, Eisenreich, S², Jones, K¹, MacFarlane, J³, Gschwend, P³, ¹ Lancaster University, Lancaster, UK² Rutgers University, New Brunswick, NJ, USA³ MIT, Cambridge, MA, USA

ABSTRACT- The distribution of organic contaminants between dissolved/gaseous and particulate phases was determined in ambient samples from the New Jersey region and sediment suspensions from Boston and New York Harbor. Measured distribution coefficients of ambient PCDD/Fs exceeded predictions based on absorption into the organic carbon (OC) fraction in aerosols by to 1 order of magnitude. In the sediments, observed solid-water distributions exceeded predictions based on f_ocK_oc products by 1-2 orders of magnitude for PAHs, PCBs and PCDDs. It is suggested that adsorption to black carbon (BC) dominated the sorption processes in atmosphere and sediments. A combined OC-absorption and BC-adsorption model was used to explain the observed data. The gas-particle partitioning of PCDD/Fs was calculated as K_p = f_om K_oa / (10¹² _oct) + f_BCK_BC-air / (10¹² _BC) and improved predictions to within a factor of 2 (0.3 log units) of the measured values. In the sediments, the overall partitioning was parameterized including a non-linear BC-adsorption model: Kd = f_ocK_oc + f_BCK_BCC_w^n-1, with n set to 0.7 and dissolved concentration C_w in g/L. Adsorption to BC emerged as the dominating matrix during atmospheric transport, and even more so in urban sediments.

Key words: gas-particle partitioning, sediment-water partitioning, black carbon, organic carbon