The hydrogeology and hydrogeochemistry of Volo Bog, Lake County, Illinois
Abstract
Volo Bog, Lake County, Illinois, is a 40 foot deep, 47 acre, Pleistocene kettle lake bog. It is recharged through both meteoric and groundwater input. Water level and water temperature data indicate groundwater recharge occurs at a depth of 15 to 30 feet originating in coarse sand and gravel on the eastern side of the bog. The groundwater flow in a surrounding and underlying glacial aquifer from southeast to northwest at an average hydraulic conductivity, k = 3 $\times$ 10$\sp{-2}$ cm/sec, and a flow gradient which varies from 2.2 $\times$ 10$\sp{-2}$ to 6.7 $\times$ 10$\sp{-4}$. The calcium-magnesium bicarbonate water is altered by reduction, acidification, filtration, and sorption processes. Mixing of meteoric water and biological utilization of nutrients in the shallow portions of the bog produce a pH of 4.5 to 5.0, and low TDS ($\sim$100mg/l). The increase in total dissolved solids with depth in the bog is likely due to mixing, filtration, or sorption processes occurring during groundwater recharge. Trace metals of copper, zinc and iron are concentrated near the bottom of the bog. Dissolved aluminum is found in the shallow, more acidic water of the bog. Nitrates are found (0-12 mg/l) near the peat/mineral interfaces. The isotopes of Deuterium and $\sp{18}$O become progressively enriched with increasing depth in the 40 foot deep kettle lake bog. The deuterium values range from $\delta$D = $-$59% at a depth of 5 feet to $\delta$D = $-$30.1% at 40 feet. There is a corresponding increase in the concentration of $\sp{18}$O with increasing depth, equalling $-$8.1% at a depth of 5 feet and $-$4.4% at 40 feet. The variation in the concentrations of heavier isotopes with depth changes seasonally. Six mechanisms were explored to explain these data: gravity, biogenic methanogenesis, evaporation, hyperfiltration, mixing, and adsorption. Methanogenesis and adsorption best explain the data. Methanogenesis contributes a 4% fractionation to the deuterium isotopes in addition to other fractionation, which exhibits a $\delta$D to $\delta\sp{18}$O ratio of 5:1.
Degree
Ph.D.
Advisors
West, Purdue University.
Subject Area
Geology|Geochemistry|Hydrology
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