----- Forwarded Message -----
From: Ed Hopkins <[log in to unmask]>
To: Charles Winterwood <[log in to unmask]> 
Sent: Tuesday, October 2, 2012 8:54 AM
Subject: Fwd: New NAWQA-ACT Publication


Thought this might be of interest because of the Iowa River(AND Herbicides).


---------- Forwarded message ----------
From: Jason L Roth <[log in to unmask]>
Date: Mon, Oct 1, 2012 at 6:06 PM
Subject: New NAWQA-ACT Publication
To: Paul D Capel <[log in to unmask]>, Stephen J Kalkhoff <[log in to unmask]>, Michael T Meyer <[log in to unmask]>, Skip V Vecchia <[log in to unmask]>


All, 

The following NAWQA-ACT associated report has just been published:

Kalkhoff, Stephen J., Aldo V. Vecchia, Paul D. Capel, and Michael T. Meyer. 2012. “Eleven-Year Trend in Acetanilide Pesticide Degradates in the Iowa River, Iowa.” Journal of Environment Quality 41 (5): 1566. doi:10.2134/jeq2011.0426.

The URL for this publication is: https://www.agronomy.org/publications/jeq/abstracts/41/5/1566

Abstract:

Trends in concentration and loads of acetochlor, alachlor, and metolachlor and their ethanasulfonic (ESA) and oxanilic (OXA) acid degradates were studied from 1996 through 2006 in the main stem of the Iowa River, Iowa and in the South Fork Iowa River, a small tributary near the headwaters of the Iowa River. Concentration trends were determined using the parametric regression model SEAWAVE-Q, which accounts for seasonal and flow-related variability. Daily estimated concentrations generated from the model were used with daily streamflow to calculate daily and yearly loads. Acetochlor, alachlor, metolachlor, and their ESA and OXA degradates were generally present in >50% of the samples collected from both sites throughout the study. Their concentrations generally decreased from 1996 through 2006, although the rate of decrease was slower after 2001. Concentrations of the ESA and OXA degradates decreased from 3 to about 23% yr−1. The concentration trend was
 related to the decreasing use of these compounds during the study period. Decreasing concentrations and constant runoff resulted in an average reduction of 10 to >3000 kg per year of alachlor and metolachlor ESA and OXA degradates being transported out of the Iowa River watershed. Transport of acetochlor and metolachlor parent compounds and their degradates from the Iowa River watershed ranged from <1% to about 6% of the annual application. These trends were related to the decreasing use of these compounds during the study period, but the year-to-year variability cannot explain changes in loads based on herbicide use alone. The trends were also affected by the timing and amount of precipitation. As expected, increased amounts of water moving through the watershed moved a greater percentage of the applied herbicides, especially the relatively soluble degradates, from the soils into the rivers through surface runoff, shallow groundwater inflow, and
 subsurface drainage.


---------------------------------------------
Jay Roth
Hydrologist, EIT
USGS Minnesota Water Science Center
Voice - 612-626-9537
Email - [log in to unmask]



-- 
Ed Hopkins
Sierra Club
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202-547-6009 fax
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