Influence of nearshore dynamics on the distribution of organic wastewater-associated chemicals in Lake Ontario determined using passive samplers

Abstract

Passive samplers (SPMDs, semi-permeable membrane devices; POCIS, polar organic chemical integrative samplers) were deployed in Lake Ontario near Pickering, Ajax, and Port Hope, Ontario in 2008 and complemented with detailed water quality indicator and water current measurements. The intent was to examine the influences of source inputs and limnological features on the distribution and dilution patterns of several organic wastewater-associated chemicals (OWCs) in dynamic nearshore waters. Generally, concentrations ranged from 0.1 to 11ng/L for most pharmaceuticals and up to 25ng/L for gemfibrozil and 28ng/L for caffeine based on previously determined POCIS sampling rates. Musk (HHCB and AHTN) and triclosan (TCS) concentrations were estimated using laboratory-derived sampling rates as part of this study (4.3–7.9L/d) and ranged up to 10ng/L for musks and 1.5ng/L for TCS near Pickering–Ajax. Nitrate and conductivity maps indicated that alongshore currents were primary drivers of distribution and transport for tributary discharges and wastewater treatment plant (WWTP) effluents parallel to shore. Organic wastewater chemicals like HHCB, AHTN, TCS, gemfibrozil, and venlafaxine were greatest in the vicinity of the Pickering–Ajax WWTP and then dramatically declined. Ibuprofen, carbamazepine, and especially caffeine concentrations exhibited more uniform distributions both within and between the Pickering–Ajax and Port Hope study areas suggesting that transport via alongshore currents may contribute to a regional background of the relatively more persistent OWCs that may not be captured in onshore–offshore gradient studies.