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A New Device for Collection of Interstitial Water
from Wetland Sediments

Results and Discussion

Water samples for analysis of redox potential, electrical conductivity and other parameters affected by atmospheric gases should be evacuated with an inert gas such as N2 and analyzed as soon as they are collected. Samples analyzed for stable parameters can be handled according to conventional guidelines.

This device collects samples that provide good documentation of sediment dynamics in wetlands and can be used to illustrate the different characteristics of specific sediment profiles (Table 1). Abiotic parameters differ among profiles in sediments and in the water column. Organic acids released from decomposing bottom materials lower the pH values in sediments, especially near the water-sediment interface, as do concentrations of various ions and other parameters. The unique chemical properties of upper sediment profiles are important because these profiles determine the direction of diffusion fluxes that maintain steady state between sediments and overlying waters. Further, many benthic invertebrates used as indicators of environmental contaminants are restricted to specific sediment profiles in wetlands. Analyses of the unique chemical environments in interstitial water in which invertebrates live may provide a better understanding of microhabitat selection and its relationship to bioaccumulation of contaminants in wetlands.

Table 1.  Abiotic data from a wetland on the Sacramento National Wildlife Refuge, California. Standard errors are in parentheses. N = 25.
Parameter Water Columna Sedimentb
Upper Mid Lower 2.5 cm 11.25 cm
Temp (C) 21.7 (.3)  21.5 (.4)  21.6 (.4)  23.1 (.9)    23.1 (.9)    
ECc 370 (15) 374 (12) 374 (12) 836 (293) 1477 (496) 
pH 8.6 (.6)  8.4 (.4)  8.3 (.5)  6.8 (.4)    7.2 (.6)    
Redox (mv) 172 (69) 181 (61) 182 (60) 72 (138) 77 (72)   
Calciumd 3.1 (.6)  3.1 (.5)  3.4 (.6)  6.2 (2.4)  17.3 (N=1)
a Samples from the water column were collected from specific depth strata with a hand pump.
b Samples from the sediment were collected with the sampling device described in this paper.
c (uS/cm)
d (moles/1 × 10-5)

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