عنوان

A study of the infiltration processes responsible for contamination of groundwater by fertilizer-derived nitrate and other chemical compounds in the karst aquifers of Orange and Washington counties, Indiana

TLpq304114330

انگلیسی

A study of the infiltration processes responsible for contamination of groundwater by fertilizer-derived nitrate and other chemical compounds in the karst aquifers of Orange and Washington counties, Indiana

[Thesis]

M. Z. Iqbal

Indiana University

1994

192

Ph.D.

Indiana University

1994

A hydrogeological study, during the period from June, 1991 to June, 1992, in the clay-soil mantled portion of a limestone terrain in southern Indiana showed a major movement of nitrate in quick pulses through the unsaturated zone immediately after a major storm event on April 15, 1992. The asymmetric profiles of nitrate concentration vs depth suggest soil water transport through large openings, termed macropores, in the clay-soil mantle above the bedrock. A KBr salt spray experiment showed recovery of percolated bromide at a depth of 10 ft within 24 hours after the storm event suggesting quick transport of bromide through macropores bypassing the soil matrix. Additionally, segregation of cations from anions during transport was observed. The reactive cation potassium showed significant retardation compared to bromide which is attributed to the strong affinity of potassium to adsorption on the surfaces of clay particles. On the other hand, an easy transport of anions is attributed to the process of anionic exclusion which drives more anions out of clay matrix. There are two end members of nitrate-sources in soil water and groundwater in the study area, the inorganic fertilizers and animal wastes. In most areas, isotopic analysis of NO3\sp--N suggests a mixed source of nitrate with a predominance of one of the end members. However, the animal waste appears to be the background nitrate-source because of numerous grazing animals in the area throughout the year. The del N of NO3-N is less than +10% in soil water and groundwater beneath cropped areas where commercial fertilizers are applied each year. A higher del N value occurs beneath lands where both fertilizers and animal wastes are the predominant sources of nitrate on the surface. In other non-agricultural areas, the groundwater samples have del N values higher than +10% where nitrate is predominantly from the excretion of grazing cattle.

Earth sciences

fertilizer

Geology

Hydrology

Orange County

Washington County

M. Z. Iqbal

p

[Thesis]

276903

a

Y