Electronic Theses and Dissertations


Open Access Thesis


Wetlands--Iowa--Black Hawk County; Water--Pollution--Environmental aspects--Iowa--Black Hawk County;


Beaver Valley Wetland in north-east Iowa was studied to determine its functionality in filtering incoming contaminants from the surrounding agricultural fields. The study was conducted from May through November of 2011. Altogether 78 water samples (from 13 sites), 84 soil samples (from 14 sites), and some sediment samples were collected for chemical analysis. Heavy metals in three different soil categories, such as surface, 6” deep, and sediments were found to be at or below the acceptable concentrations, indicating no immediate concern for metal toxicity in the wetland environment. The chemical tracers that were used to study the sub-surface flow regime could not confirm the hypothesized flow regime in the shallow sub-surface. The possible scenarios are as follows; (1) the tracers may have entered the sand lenses and became immobilized, (2) the tracers may have moved in a curved flow path deeper than the injection holes, and (3) the tracers may have been lost to deep infiltration. The analysis of water samples for various physical, chemical, and biological parameters focused on both spatial and temporal changes in water quality. The changes were significant during mid-summer compared to early and late summer. The probable causes for this could be the rainfall, algae growth and high organic load that were observed during the mid-summer. Most contaminants that were flushed from the surrounding areas into the wetland showed significant decrease in their concentrations going from the inlet to the outlet. High turbidity, high loads of TSS, and low DO were commonly observed at the inlet sites. The primary reason for the poor water quality condition at these sites was high organic loads and erodible agricultural soils in the surrounding areas. The wetland shows a much better quality of water at the outlet sites, indicating that the unit has been functioning well in filtering various contaminants. Considerably high DO levels (21.3 mg/L at site W7), low turbidity (2.5 NTU at site W9), and low TSS (1.5 mg/L at site W8) values clearly prove this observation. The wetland being in proximity to the agricultural fields, some of the chemical parameters like nitrate, phosphorus, and chloride are of major concern. Interestingly, none of the sites showed dissolved nitrate in the water and the chloride level was well below the levels of concern. Absence of nitrate in the water could mean that nitrogen was consumed by microorganisms to extract oxygen and decompose the organic matter. On the other hand, the wetland is showing evidence of reducing phosphorus in the system by removing them from the water column. In Water Quality Index (WQI) analysis, the system varied from “medium” to “good” categories. Out of 75 water samples, 25 (33%) showed “medium” WQI values (50-70) and 50 samples (67%) were “good” (70-90). From this short term study, it is concluded that the wetland has been performing well in filtering environmental contaminants. However, a long term water quality monitoring plan should be established to get a complete picture on the ecological functions of the wetland.

Date of Award


Degree Name

Master of Science

First Advisor

Mohammad Z. Iqbal

Date Original


Object Description

1 PDF file (xii, 173 pages)



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