Summary of Previous Experimental Studies
The sources of the sediment samples used in this study are described in previous publications (2,12−17) and the references cited therein. Sediment characteristics are summarized in Table 1. Triplicate sediment samples from Lake Hartwell and Hunters Point were characterized for PCBs following USEPA methods 3550B (hexane:acetone sonication), 3630B (activated granular copper to remove elemental sulfur), 3630C (silica gel column cleanup), and 8082 (PCB congener analysis). Duplicate sediment samples from Grasse River, Milwaukee River, and Niagara River were characterized following USEPA methods 3660B (sulfur cleanup), 3665A (sulfuric acid clean up), 3630C, and 8082. Triplicate sediment samples from Crab Orchard Lake were characterized using a sulfuric acid and copper cleanup followed by PCB congener analysis.
Table 1  Sediment Physicochemical Properties for Lake Hartwell (LH), Hunters Point (HP), Grasse River (GR), Milwaukee River Location 1 (MR 1), Milwaukee River Location 2 (MR 2), Niagara River (NR)a, and Crab Orchard Lakeb Sediments Contaminated with PCBs
physicochemical property  LH  HP  GR  MR 1  MR 2
TOC %  2.8 ± 0.5c  1.7d  5.17 ± 0.31e  3.22 ± 0.07e  3.70 ± 0.00e
black carbon %  no data  0.29f  0.365 ± 0.035e  0.640 ± 0.065e  0.616 ± 0.013e
petrographic information or microscopy observation  a very small amount of fine coal like fragments  presence of charcoal, coal and coke particles  mostly vegetative debris  presence of some coal-derived particles  presence of some coal-derived particles
sediment mass less than 63 μm %  96  19  70  74  76
sediment mass in light sediment fraction %  1.2  4  12.4  7.1  11.6
PCB concentration (μg/kg)  1250  9900  6820  45160  87400
PCB mass in light sediment fraction %  18  68  64.5  40.3  43.5
mass fraction of PCBs associated with Dapp,fast/R2  75  43  76  59  62
mass fraction of PCBs desorbed in 1 month  78  35  91  80  85
a  TOC = 0.83 ± 0.03%; black carbon = 0.258 ± 0.056%; arochlor 1254 PCB concentration = 330 (μg/kg). Data taken from ref (14).
b  Crab Orchard Lake sediment: TOC = 0.59%; the sediment comprised 16% clay, 70% silt, 14% sand; arochlor 1254 PCB concentration = 29153 (μg/kg); PCB congener mass fractions desorbed within 14 days ranged from 40 to 80%; black carbon % was not determined. Data taken from ref (12).
c  Data taken from ref (13).
d  Data taken from ref (2).
e  Data taken from ref (14).
f  Black carbon was taken as 29% of TOC which was estimated based on the average BC/TOC ratio for 6 samples described by Cho et al. (18) taken from an adjacent location in the same mudflat where the original HP sediment was sampled. Free aqueous phase PCB concentrations in Lake Hartwell, Hunters Point, Grasse River, and Milwaukee River sediments were determined using an alum (Al2(SO4)3·18H2O) flocculation centrifugation method. Differences between these experimental conditions are highlighted in the Supporting Information (SI). Free aqueous concentrations were determined in Niagara River sediment using a polyoxymethylene solid phase extraction owing to very low concentrations, and for Crab Orchard Lake sediment free aqueous concentrations were determined using a matrix SPME method (additional details are provided in the SI). Free aqueous PCB concentrations were reported based on duplicate or triplicate analyses. Pollutant desorption from all sediments was measured following a multiple step Tenax bead method. Individual experimental batch conditions and sampling times are provided in the SI. Total organic carbon (TOC) was measured in all cases by combustion in an elemental carbon analyzer following treatment with acid to remove carbonates. Black carbon (BC) was analyzed using a wet chemical oxidation method after pretreatment to remove non-BC materials (200).
Biouptake experiments were carried out on the marine species Neanthes arenaceodentata and Leptocheirus plumulosus and the freshwater oligochaete Lumbriculus variegatus using 28-day sediment toxicity protocols as outlined in the SI. Tissues and digestive fluids were sonicated according to USEPA method 3550B and the lipid content of organisms was measured by spectrophotometric analysis. PCB concentrations in biolipids were reported based on duplicate or triplicate analysis.