Use of Semipermeable Polymeric Membrane Devices to Monitor Organic Contaminants in Lincoln Creek, Milwaukee, Wisconsin
DeVita, William M.
University of Wisconsin-Stevens Point, College of Natural Resources
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Semipermeable polymeric membrane devices (SPMDs) were evaluated as concentrators of nonpolar organic contaminants in Lincoln Creek, an urban stream in Milwaukee, WI. There were no significant levels of polychlorinated biphenyls (PCBs) or organochlorine pesticides (OCls) detected, consequently, this report focuses on polynuclear aromatic hydrocarbons (PAHs). SPMD method detection limits (MDLs) were determined for PCBs, OCls and PAHs. Values ranged from .004 μg/g for mono- and dichlorobiphenyl (PCBs) to 1.0 μg/g for benzo(g,h,i)perylene, however, most MDLs ranged from .050 to .100 μg/g. SPMD methodology demonstrates excellent reproducibility with percent coefficients of variance (%CV) less than 30 and are effective concentrators of biologically available PAHs. A pilot study initiated in October, 1993, revealed 11 of 16 targeted PAHs were detected in SPMDs deployed for 21 days. Fluoranthene, pyrene and chrysene (PAHs) were of highest concentration. Composite sediment samples collected upstream of the SPMD exposure site were also analyzed and 14 of 16 PAHs were detected. Differences in PAH concentrations occur between SPMDs and sediments. Higher concentrations of larger molecular dimension and higher Kow PAHs in sediment samples was noted. Frequency and intensity of storm events affect loading of P AHs into Lincoln Creek . An r^2 value of .9657 was obtained when comparing storm events occurring over a 30-day period to total PAHs accumulated in SPMDs. SPMDs and fathead minnows (Pimephales promelas) were simultaneously deployed during five, 30-day exposure periods between April 17 and September 19, 1993. Total SPMD accumulated PAHs ranged from 9.1 to 30.1 μg/g with fluoranthene, pyrene and chrysene accounting for an average of 72 % of this total. Fathead minnows accumulated PAHs ranging from 0.20 to 11.6 μg/g (lipid normalized). Rusty crayfish (Orconectes rusticus) were deployed during two 30-day periods and accumulated PAHs at 3.0 and 7.2 μg/g (lipid normalized). SPMDs, fathead minnows, and rusty crayfish were simultaneously exposed for 30 days between July 21 and August 20, 1993, and sampled on days 2, 4, 8, 16, 24 and 30 to record uptake of PAHs, PCBs, and OCls. Fluoranthene, pyrene, and chrysene were detected in SPMDs at levels of 5.8, 4.5, and 2.7 μg/g respectively by day 30. Four and five-ringed PAHs appear to be in the linear region of the uptake curve into SPMDs while three-ringed PAHs appear to reach equilibrium during this 30-day exposure. Fathead minnow and rusty crayfish P AH curves demonstrate metabolism and elimination of contaminants despite further inputs of PAHs into Lincoln Creek from storm water runoff. Three-ringed PAHs appear to exhibit faster rates of uptake and depuration in all three sample matrices. Hexane-filled SPMDs were exposed concurrently with lipid-filled SPMDs to compare accumulation efficiency of these two sampling devices. Retention of hexane in SPMDs was variable with up to 96% loss of the initial 100 mL hexane by the low density polyethylene (LOPE) membrane. Lipid-filled SPMDs accumulated 1.5 to 22 times PAH levels found in hexane-filled SPMDs. Hexane SPMDs produced unacceptable %CVs for the most abundant PAHs, fluoranthene, pyrene, and chrysene, at 85, 62, and 75 percent respectively. Lipid SPMDs produced %CVs of 7.3, 6.6, and 5.1 for the same compounds respectively. Reduction in uptake of contaminants into SPMDs due to biofouling of LPDE was investigated during one 30-day exposure. SPMDs which were periodically cleaned displayed an average of 41% higher concentration of PAHs than those which were not cleaned. Four additional PAHs were detected in cleaned SPMDs.