flats. The boundaries of the sampling zones were chosen based upon major physiographic features, 

 such as points of land and the dimensions of individual waterways. Because of these possible sources 

 of bias in the data, the estimates of the spatial extent of toxicity prepared during Phase 1 must be 

 interpreted as rough estimates, and not as absolutes. 



During Phase 2 of this survey, the probabalistic, random-stratified sampling design used by the EMAP 

 (Schimmel et al., 1994) was used within the boundaries of the Phase 2 survey area (Figure 5). During 

 the design phase, the area was subdivided into strata roughly equal in size. The dimensions of these 

 strata were outlined on a navigation chart, the chart was digitized, and the coordinates for the indi- 

 vidual stations were selected randomly with the aid of a computer program. One station (one sample) 

 was sampled within each stratum. The toxicity results were weighted to the size of each stratum, the 

 cumulative distribution function prepared, and using <80% of controls as the critical value, the size 

 (and percent) of the area that was toxic was determined. 



Chemical Analyses: Phase 1. Sediment samples were chosen for chemical analyses based upon an 

 examination of the toxicity test results. Samples were chosen that represented gradients in the toxicity 

 results and that also represented contiguous geographic strings of stations. Sediments were extracted 

 by Battelle Ocean Sciences in two batches containing approximately 19 field samples each. One pro- 

 cedural blank, one standard reference material, a matrix spike sample, and a matrix spike duplicate 

 sample were extracted with each batch. Each field sample contained 30 g to 50 g of sediment. Sedi- 

 ment dry weight was determined using approximately 5 g of sample material. Analyses were per- 

 formed for total trace metals, simultaneously extracted metals (SEM), acid-volatile sulfides (AVS), 

 PCB congeners, pesticides, and polynuclear aromatic hydrocarbons (PAHs). Also, analyses were per- 

 formed for total organic carbon (TOC) and sediment grain size. 



Extraction and analytical methods followed those of Peven and Uhler (1993). Sediment was weighed 

 into pre-weighed Teflon jars; surrogate internal standards (to monitor extraction efficiency), sodium 

 sulfate, and 1:1 methylene chloride (DCM):acetone were added to each jar. Samples were extracted 

 with the solvent mixture three times using shaker table techniques. After each extraction, the jar was 

 centrifuged, and the overlying solvent decanted into a labelled Erlenmeyer flask. Solvent from each of 

 the three extractions was combined in the flask. The combined extract was chromatographed through 

 a 20 g alumina column eluted with dichloro-methane (DCM). After column cleanup, the sample ex- 

 tract was concentrated to approximately 900 wL and further processed using a size-exclusion high 

 performance liquid chromatography (HPLC) procedure. Six hundred microliters of the extract were 

 fractionated in this procedure, and the remaining 300 uL archived. After HPLC cleanup, the sample 

 extract was concentrated to approximately 1,000 uL and recovery internal standards were added to 

 quantify surrogate recovery. The final sample was split in half by volume; one half was dedicated to 

 GC/MS analysis of PAHs and the other half was solvent-exchanged with isooctane and analyzed by 

 GC/ECD for PCBs and pesticides. 



The analytical methods for the trace metals followed those of Crecelius et al. (1993). Samples were 

 completely digested with 4: 1 HNO3/HCIO4 and heated. The digestates were analyzed either by graph- 

 ite furnace atomic absorption (Ag, Cd, Se), or cold vapor atomic absorption (Hg), or x-ray fluorescence 

 (Al, As, Cr, Cu, Fe, Mn, Ni, Zn), or inductively coupled plasma mass spectrometry (Sb, Sn). Two 

 reagent blanks and three standard reference materials were analyzed in each analytical string of 50 

 samples. 



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