My Account: Log In | Join | Renew
Search
Author
Title
Vol.
Issue
Year
1st Page

Abstract

 

This article in JEQ

  1. Vol. 39 No. 4, p. 1416-1428
     
    Received: Oct 13, 2009
    Published: July, 2010


    * Corresponding author(s): kathorn@usgs.gov
 View
 Download
 Alerts
 Permissions
 Share

doi:10.2134/jeq2009.0408

Order of Functionality Loss during Photodegradation of Aquatic Humic Substances

  1. Kevin A. Thorn *,
  2. Steven J. Younger and
  3. Larry G. Cox
  1. U.S. Geological Survey, Denver Federal Center, MS 408, Denver, CO 80225-0046. Assigned to Associate Editor Robert Cook. The use of trade names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey

Abstract

The time course photodegradation of the Nordic aquatic fulvic and humic acids and Suwannee River XAD-4 acids subjected to UV irradiation with an unfiltered medium pressure mercury lamp was studied by liquid-state 13C nuclear magnetic resonance. Photodecarboxylation was a significant pathway in all cases. Decreases in ketone, aromatic, and O-alkyl carbons were observed throughout the course of the irradiations, whereas C-alkyl carbons resisted photodegradation. Peaks attributable to the low-molecular-weight photodegradation products bicarbonate, formate, acetate, and succinate grew in intensity with irradiation time. The final products of the irradiations were decarboxylated, hydrophobic, predominantly C-alkyl and O-alkyl materials that were resistant to further photodegradation. The total amount of carbon susceptible to loss appeared to be related mainly to the total concentration of carbonyl and aromatic carbons and partly to the concentration of O-alkyl carbons in the fulvic, humic, and XAD-4 acids. The carbon losses for Nordic fulvic, Nordic Humic, Suwannee fulvic, and Suwannee XAD-4 acids were estimated to be 75, 63, 56, and 17%, respectively. More detailed analyses of the effects of irradiation on the carbonyl functionality in Nordic humic acid and Laurentian soil fulvic acid through reaction with hydroxylamine in conjunction with 15N nuclear magnetic resonance analysis confirmed preferential photodegradation of the quinone/hydroquinone functionality over ketone groups and the loss of ester groups in Laurentian fulvic acid.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © 2010. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America