PAH standards (purities ≥ 99%) were obtained from ChemService, Inc. (West Chester, PA, USA). Target analytes included naphthalene (NAP), acenaphthene (ACE), acenaphthylene (ACY), fluorene (FLO), anthracene (ANT), phenanthrene (PHE), fluoranthene (FLA), pyrene (PYR), chrysene (CHR), benz(a)anthracene (BAA), benzo(b)fluoranthene (BBF), benzo(k)fluoranthene (BKF), benzo(a)pyrene (BAP), benzo(ghi)perylene (BPL), and indeno123(cd)pyrene (IPY). Cleanup and extraction solvents were pesticide or Optima® grade from Fisher Scientific (Fairlawn, NJ, USA).
Water quality data included temperature, pH, dissolved oxygen, specific conductivity, oxidative-reductive potential (ORP) and nitrate and ammonium concentrations, and were collected at each site during sampler deployment and retrieval using a YSI
® sonde. Additionally, grab samples were also taken at sampler deployment and retrieval at certain sites for analysis of total and dissolved organic carbon (TOC and DOC), as well as total suspended and total dissolved solids (TSS and TDS). The two measurements were averaged for each sampling event and results are summarized in
Supporting Information.
SPMD field cleanup and laboratory extraction were performed as previously described (20 (
link)) and in accordance with standard operating procedures and standard analytical methods. Quality control consisted of field blanks, trip blanks and field cleanup blanks. Laboratory quality control included reagent blanks, high and low concentration fortifications, and unexposed fortified SPMDs. Quality control resulted in duplicate sites average RSD equaling 15%, and target compounds in blanks were either non-detect or below levels of quantitation.
After extraction, samples were solvent exchanged into acetonitrile and analyzed by HPLC with diode-array and fluorescence detectors. DAD signals were 230 and 254 nm and FLD excitation and emissions were 230 and 332, 405, 460, respectively. Flow was 2.0 mL/min beginning with 40/60% acetonitrile and water and steadily ramping to 100% acetonitrile over a 28 minute run per column maker recommendations. Because the low molecular weight volatile compounds were impacted by the method solvent evaporation steps, SPMD concentrations were recovery corrected with method recovery averages ranging from 35% for NAP to 95% for BPL (
Supporting Information Table S1).
The equation established for converting SPMD concentrations (
CSPMD) to water concentrations (
Cwater) using laboratory sampling rates (
Rs) in L/day is:
where
VSPMD is the volume of the sampler and
t is the time in days. Laboratory sampling rates from the literature were used and temperature corrected using a trendline based on rates at three temperatures: 10, 18, and 26° C (9 , 21 (
link)). Loads were calculated from the concentrations using USGS flow estimates at the Portland station. Data analysis was performed using Microsoft Excel® 2003, SigmaStat® for t-tests and rank sum tests, S+® for principal component analysis and SigmaPlot® for graphing.
Sower G, & Anderson K.A. (2008). Spatial and temporal variation of freely dissolved PAHs in an urban river undergoing Superfund remediation. Environmental science & technology, 42(24), 9065-9071.