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Estimation of partition coefficients for five trace metals in sandy sediments and application to sediment quality criteria
Author(s) -
Hassan S.M.,
Garrison A.W.,
Allen H.E.,
Di Toro D.M.,
Ankley G.T.
Publication year - 1996
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620151214
Subject(s) - partition coefficient , adsorption , sediment , ionic strength , chemistry , zinc , environmental chemistry , cadmium , metal , copper , limiting , water quality , mineralogy , chromatography , geology , ecology , mechanical engineering , paleontology , organic chemistry , aqueous solution , engineering , biology
Six low‐capacity natural adsorbents‐were identified for the five metal cations (cadmium, copper, nickel, lead, and zinc) for which the U.S. Environmental Protection Agency is developing sediment quality criteria (SQC). The adsorbents were commercial sea sand and chromatographic sand (both from natural sources) and four sandy sediments collected from different parts of the continental United States. Batch adsorption experiments were conducted for each sediment with a mixture of the five cations at low concentrations (from about 15 to 700 μg/L) using a 48‐h equilibration time. The distribution coefficients (K d s) were calculated using the initial linear segment of the plotted adsorption isotherms; selection of the linear segment involved repetitive regression analysis of selected data points. Chromatographic sand at pH 3.7 showed the lowest adsorption capacity for all the metal cations. An increase in pH of the medium generally resulted in a higher K d , whereas an increase in ionic strength resulted in a lower K d Chromatographic sand, especially at low natural pH levels, may serve as a limiting adsorbent or a benchmark for maximum pore‐water concentrations for these five metal cations because its associated pore water would contain higher levels of the cations than other sediments. These measured K d s, which are expected to be minimum values for natural sediments, were applied to screen sediment samples for SQC. An equation that can predict the K d for each of the five metals for sandy sediments at neutral and lower pH levels was derived from the regression of the measured K d s against the pH of the six sediments used in this study. This equation was tested with a data set from Lake Michigan sediment samples. Porewater metal concentrations calculated from the predicted K d values were used to predict whether a sediment would pass SQC in terms of predicted interstitial water criteria toxic units; 16 of 38 of these sediments were predicted not to exceed proposed SQC for metals.