| Abstrakt: |
Fluvial unconsolidated bottom sediments that have the potential to become part of the suspended sediment load in the Maumee River Basin, Ohio, ranged in texture from sandy loams to clays. Particle size analysis by water dispersion and electrolyte dispersion procedures revealed that an average of 34% of the total clay fraction was aggregated into the silt and sand‐sized range, indicating that the coarser fraction of bottom sediments may be physically‐chemically active. The water‐dispersible clay was lower in mica but higher in expandable 14Å (smectite) and quartz constituents than the electrolyte‐dispersible clay. The mineralogy of clay‐sized bottom sediments (mica, 65 ± 5%; chlorite‐vermiculite, 12 ± 5%; quartz, 14 ± 5%; expandable 14Å (smectite) and kaolinite, 5 ± 5%) from upstream agricultural drainage ditches, major Basin tributaries, and from the Maumee River are essentially identical. The 2‐ to 50‐µm fraction was dominated by quartz with secondary amounts of mica, kaolinite, feldspars, and carbonates. Mean calcite, dolomite, and calcium carbonate equivalent values were 4.1, 3.4, and 7.8%, respectively. Calcite dissolution in transport is probable on the basis of observed calcite‐dolomite ratios. Organic matter content of the fluvial bottom sediments (3 to 7%) was analogous to Lake Erie bottom sediments and Maumee River suspended sediments. CEC values ranged from 39 to 55 meq/100 g for the total clay fraction collected by electrolyte and water dispersion procedures. Enrichment of heavy metals of bottom sediments over surficial soil materials occurred for Cu, Ni, Zn, Ca, and Pb by factors of 1.6, 2.0, 2.3, 3.5, and 3.0, respectively. Traces of herbicides (atrazine, 2‐4‐D) and insecticides (DDT metabolites, endosulfan) were detected in the filtered stream water samples and bottom sediment materials. Downstream trends in selected physical, chemical, and mineralogical properties could not be related to increased urban influences or increased stream discharge. |
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