Quaternary ammonium compounds (QACs) in marine sediments: Detection, occurrence, and application as geochemical tracer

Quaternary ammonium compounds (QACs) are a major class of cationic surfactants and have been wildly used in commercial products. However, there is very little knowledge of their environmental sources and fates. This thesis mainly focused on developing robust methods to detect QACs in marine sediments, then studying their occurrence, fate, and application as wastewater-specific tracers of other contaminants in estuarine systems. The study area included large regions of the lower Hudson Basin, especially the highly urbanized and sewage affected New York/New Jersey Harbor complex.;A robust analytical method was developed using HPLC-MS detection with electrospray (ESI) and Time-of Flight (ToF) detection. Analytical methods were developed with superior extraction efficiency, analyte recoveries and sensitivity than prior approaches. The HPLC-ESI-ToF-MS method was sensitive for all targeted QACs, which included dialkyldimethylammonium compounds (DADMACs), benzalkonium compounds (BACs), and alkyltrimethylammonium compounds (ATMACs). A number of QACs were detected for the first time in environmental samples (e.g., DADMAC C8:C8 and C8:C10), and other high concentration QACs that have not been reported in the scientific literature to date (ATMAC 20 and 22). The specificity of alkylammonium ion detection proved to be surprisingly great. A unique positive mass defect of quaternary ammonium ions was discovered and provides significant resolving power when utilizing ToF or other higher resolution mass spectrometers.;This thesis provides the first extensive study of major QACs in any sedimentary environments. QACs are found to be ubiquitous in the NY/NJ Harbor complex with extraordinary high level in the sediments impacted mainly by the wastewater from municipal wastewater treatment plants (WWTP) and combined sewer overflows (CSO). Ditallowdimethylammonium compounds (DTDMAC) are DADMACs with longer alkylchains (C14-C18), and are consistently seen to be the most important QACs in sediments of the lower Hudson Basin. However, more soluble QACs are found to be more abundant in the samples impacted by less treated wastewaters coming from CSOs. Further evidence shows that the extent of biodegradation of QACs during treatment in WWTP positively correlates with the solubility of the compounds, but multiple lines of evidence suggest that all of the QACs studied are preserved well in muddy sediments after they are discharged into the environment.;The geochronology of QACs was determined in dated sediment cores and time series surface sediments collected from WWTP-affected areas of the Harbor complex.