Atrazine Transport Within a Coastal Zone in Southeastern Puerto Rico: a Sensitivity Analysis of an Agricultural Field Model and Riparian Zone Management Model

Authors

Candiss O. Williams, Charles E. Kellogg National Soil Survey and Research LaboratoryFollow
Richard Lowrance, National Risk Management Research Laboratory
Thomas Potter, Southeast Watershed Research Laboratory
David D. Bosch, Southeast Watershed Research Laboratory
Timothy Strickland, Southeast Watershed Research Laboratory

ORCID IDs

Candiss O.Williams

Date of this Version

2016

Citation

Environ Model Assess (2016) 21:751–761

Comments

© Springer International Publishing Switzerland 2016

DOI 10.1007/s10666-016-9508-4

Abstract

Agrichemical runoff from farmland may adversely impact coastal water quality. Two models, the Agricultural Policy/Environmental eXtender (APEX) and the Riparian Ecosystem Management Model (REMM), were used to evaluate the movement of the herbicide atrazine to the Jobos Bay National Estuarine Research Reserve from adjacent fields. The reserve is located on Puerto Rico’s southeast coast. Edge-of-field atrazine outputs simulated with the APEX were routed through a grass-forest buffer using the REMM. Atrazine DT₅₀ (half-life) values measured in both field and buffer soils indicated that accelerated degradation conditions had developed in the field soil due to repeated atrazine application. APEX simulations examined both the measured field and buffer soil atrazine DT₅₀ and the model’s default value. The use of the measured field soil atrazine degradation rate in the APEX resulted in 33 % lower atrazine transport from the field. REMMsimulations indicated that the buffer system had the potential to reduce dissolved atrazine transport in surface runoff by 77%during non-tropical stormevents by increasing infiltration, slowing transport, and increasing time for pesticide degradation. During a large runoff event due to a tropical stormthat occurred close to the time of an atrazine application, the REMM simulated only a 37 % reduction in atrazine transport. The results indicate that large storm events soon after herbicide application likely dominate herbicide transport to coastal waters in the region. These results agree with water quality measurements in the reserve. This study demonstrated the sensitivity of these models to variations in DT₅₀ values in evaluating atrazine fate and transport in the region and emphasizes that the use of measured DT₅₀ values can improve model accuracy.