Documenting the pesticide processes module of the ARS RZWQM agroecosystem model

Abstract

We describe the theory and current development state of the pesticide process module of the USDA‐Agricultural Research Service Root Zone Water Quality Model, or RZWQM. Several processes which are significant in determining the fate of a pesticide application are included together in this module for the first time, including application technique, root uptake, ionic dissociation, soil depth dependence of persistence, volatilization, wicking upward in soil and aging of residues. The pesticide module requires a large number of parameters to run (as does the RZWQM model as a whole) and it is becoming clear that RZWQM will find most interest and use as part of a ‘scenario’ in which all data requirements are supplied and the predictions of the system compared with a real (usually partial) data set. Such a scenario may then be modified to examine the response of the system to changes in inputs. It also has significant potential as a technology transfer or teaching tool, providing detailed understanding of a specific agronomic system and its potential impacts on the environment. Published in 2004 for SCI by John Wiley & Sons, Ltd.

Uncalibrated modelling of conservative tracer and pesticide leaching to groundwater: comparison of potential Tier II exposure assessment models

“…The model uses a non‐uniform mixing approach to model chemical transfer to overland flow 14. Chemical transport in the matrix is modelled using a partial piston displacement, partial mixing approach.…”

Agronomic and environmental implications of enhanceds-triazine degradation

“…Two one‐dimensional leaching estimation and chemistry models (LEACHMs) were constructed to compare the potential for atrazine and its metabolites to leach through s ‐triazine‐adapted and non‐adapted soils 7, 8. For the non‐adapted simulation, the half‐lives for atrazine (60 days), desethylatrazine (DEA) (52 days), deisopropylatrazine (DIA) (36 days) and hydroxyatrazine (HA) (60 days) were assumed to be constant for 0–30 cm depth 9, 10. Persistence estimates increased linearly from 30 to 100 cm depth, with maximum half‐life values at the bottom of the root zone threefold higher than that in the upper horizon: 180 days for atrazine, 156 days for DEA, 108 days for DIA and 180 days for HA 10–12.…”

“…For the non‐adapted simulation, the half‐lives for atrazine (60 days), desethylatrazine (DEA) (52 days), deisopropylatrazine (DIA) (36 days) and hydroxyatrazine (HA) (60 days) were assumed to be constant for 0–30 cm depth 9, 10. Persistence estimates increased linearly from 30 to 100 cm depth, with maximum half‐life values at the bottom of the root zone threefold higher than that in the upper horizon: 180 days for atrazine, 156 days for DEA, 108 days for DIA and 180 days for HA 10–12. The percentage of atrazine converted to DEA, DIA and HA was set to reflect historic trends, that is, 72% for DEA, 18% for DIA and 10% for HA 12.…”

“…The percentage of atrazine converted to DEA, DIA and HA was set to reflect historic trends, that is, 72% for DEA, 18% for DIA and 10% for HA 12. For adapted soils, the half‐life for atrazine (6 days), DEA (10 days), DIA (8 days) and HA (6 days) was reduced relative to non‐adapted soils and assumed to be constant for 0–30 cm depth 9–11. Again, persistence estimates increased linearly from 30 to 100 cm depth, but the maximum half‐life value at the bottom of the root zone was 11‐fold higher than that in the upper horizon: 66 days for atrazine, 110 days for DEA, 88 days for DIA and 66 days for HA 9–10, 13.…”

Software for pest‐management science: computer models and databases from the United States Department of Agriculture—Agricultural Research Service

“…The model utilizes time steps from minutes to days depending on the process to be described, and may be used to estimate long‐term (decades) effects 12, 13. Applications of the model to a variety of pesticide problems is being reviewed and presented in a series of papers for this Journal 14–19. RZWQM is quite complex, but a full Windows™‐based user interface has greatly improved its friendliness over the original version.…”