Mobility of Organic Contaminants in Soils Irrigated with Treated Wastewater

Project Number:

02R-07

Project Duration:

24 months

Dates:

May 1, 2002 to April 30, 2004

Institution of Principle Investigator while on this project:

University of Arizona

Investigators (most current known information)

Chorover, Jon (PI)

Associate Professor, Environmental Chemistry, Department of Soil, Water and Environmental Science, The University of Arizona, Shantz 429, Bldg 38, Tucson AZ 85721

TEL: +1-520-626-8220, FAX: +1-520-621-1647, Email: chorover@ag.arizona.edu

Chefetz, Benyamin

Lecturer of Environmental Chemistry, Department of Soil & Water Science, Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel

TEL: +972-8-948-9384, FAX: +972-8-947-5181, Email: chefetz@agri.huji.ac.il

Proposal Abstract

Population growth in arid and semi-arid regions of the world places increasing pressure on diminishing supplies of fresh water for human consumption and irrigation. As a result, there is a trend toward reutilization of treated wastewater, particularly for crop land irrigation, in both the southwestern US and Israel. Treated wastewater contains higher concentrations of dissolved organic matter (DOM), which can exhibit a high affinity for hydrophobic organic pollutants, particularly agricultural pesticides. The overall goal of this project was to study the influence of irrigation with treated wastewater on the interactions of key hydrophobic pollutants in soils. Batch and column sorption experiments were conducted to study the molecular-scale characteristics of DOM that affect its interaction with hydrophobic pollutants and elucidate the implications for contaminant transport in soils. The research supported by the IALC has involved isolation and characterization of wastewater DOM. Wastewater DOM deriving from various sources was isolated from the aqueous phase and separated into fractions on the basis of solubility. We focused on isolation and characterization of bulk DOM as well as the important fractions thereof comprising hydrophobic acids and neutrals. We then examined the interaction of these constituent DOM pools with two common hydrophobic pesticides, atrazine and ametryn.

The hydrophobic neutral (HoN) fraction showed significant sorptive capacity toward organic pollutants. Although this fraction makes up a relatively small portion of the total DOM pool (<10%), and it is mainly composed from aliphatic moieties, it is a dominant sorbent, especially in DOM which is characterized by low hydrophobicity. Our column studies indicate that, based on its higher hydrophobicity, the HoN fraction is expected to significantly interact with the soil matrix, thereby reducing the mobility of DOM-adsorbed hydrophobic organic compounds. It was also found that the chemical composition of DOM is a more important predictor of contaminant uptake than is the concentration of dissolved organic carbon. Hence, the evaluation of the mobility of organic pollutants by wastewater irrigation requires not only the assessment of the total DOC concentration but also, more importantly, the contents of the hydrophobic fractions.