Date of Award
Master of Science
Humans influence soil properties through agriculture, urbanization, and many other activities. This study investigated the degree to which humans influence dynamic soil properties (including bulk density, organic carbon, and heavy metal concentrations) in a suburban landscape and assesses the variability of these soil properties with respect to the length of time that has passed since disturbance or construction activities. Aerial photos were used to delineate residential areas from different years and nine time periods of development were established. Ten homes from each time period of development were randomly selected and soil samples were collected from the center of the front yard of each home. Soil cores were divided into 0-5, 5-10, and 10-20 cm increments with a composite of five cores. The soils were analyzed for bulk density, total carbon, inorganic carbon, heavy metal concentrations (Cd, Co, Cr, Cu, Ni, Pb, Zn), pH, and particle size distribution. Organic carbon content was determined by subtracting the inorganic carbon from the total carbon. Soils adjacent to older homes could be recovering from disturbance that occurred during construction. It was found that bulk density ranged from 0.68 to 1.88 g/cm3 for the entire study area with a mean of 1.13 g/cm 3 at depth 0-5 cm, 1.34 g/cm3 at 5-10 cm, and 1.44 g/cm3 at 10-20 cm. The mean soil bulk density for the time periods ranged from a low of 1.23 g/cm3 for soil adjacent to homes built prior to 1939 to 1.70 g/cm3 for soil adjacent to homes built from 2003-2005. The bulk density was positively correlated with the sand content the latter of which contributed to the higher bulk density in soils from the most recent time periods of development. The higher bulk density values of these soils could also be due to compaction during construction or an accumulation of organic matter. The organic carbon ranged from 0.01 to 8.41% for the entire study area with a mean of 3.11% at depth 0-5 cm, 1.92% at depth 5-10 cm, and 1.38% at depth 10-20 cm. The mean organic carbon for the time periods of development ranged from 4.49% from soils around houses developed prior to 1939 to 0.49% for soils from time period of development 2003-2005. Concentrations of Cu and Pb were higher in soils from older residential areas. The mean Cu concentration for the Pre 1939 time period of development was a high of 20.8 mg kg-1 and for time period 2003-2005 was a low of 14.9 mg kg-1. Nickel concentrations increased with depth with a mean of 20.1 mg kg-1 at depth 0-5 cm, 21.0 mg kg-1 at depth 5-10 cm, and 22.2 at depth 10-20 cm. Organic carbon was positively correlated with concentrations of Pb, Cu, and Cr. All the heavy metals were positively correlated with one another except Zn. The data suggests that all the metals except Zn have a common origin, which is most likely parent material. Higher concentrations of Cu and Pb could be due anthropogenic inputs or due to the higher organic matter content in soils adjacent to older homes. There may be a source that causes an increase in Cd, Cr, Co, Cu, Pb, and Ni concentrations in soil adjacent to homes built from 1983-1990.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Amy Elizabeth Norton
Norton, Amy Elizabeth, "Dynamic soil properties across a suburban landscape, Ankeny, Iowa" (2007). Retrospective Theses and Dissertations. 15032.