Abstract
Terbuthylazine is commonly used as an herbicide to control weeds and prevent non-desirable grow of algae, fungi and bacteria in many agricultural applications. Despite its highly negative effects on human health, environmental modeling of this kind of pesticide in the vadose zone till reaching groundwater is still not being done on a regular basis. This work shows results obtained by two mathematical models (PESTAN and PRZM-GW) to explain terbuthylazine behavior in the non-saturated zone of a vertical soil column. One of the models use a one-dimensional analytical formulation to simulate the movement of terbuthylazine through the non-saturated soil to the phreatic surface. The second and more complex model uses a whole set of parameters to solve a modified version of the mass transport equation considering the combined effect of advection, dispersion and reactive transport processes. Both models have been applied as a case-study on a particular location in South Valencia Aquifer (Spain). A whole set of simulation scenarios have been designed to perform a parameter sensitivity analysis. Despite both models leading to terbuthylazine’s concentration values, numerical simulations show that PRZM-GW is able to reproduce concentration observations leading to much more accurately results than those obtained using PESTAN.
Highlights
Pesticides are “substances or organisms used to eliminate, incapacitate, modify, inhibit growth of or repel pests
Pesticide Analytical model (PESTAN) results analysis has been done by comparing the values of terbuthylazine concentrations
To illustrate the differences between results obtained by both models and to compare the actual observations with the predictions made by PESTAN and Pesticide Root Zone Model for GroundWater (PRZM-GW), Figure 8 shows the comparison between the results obtained by PESTAN and PRZM-GW for four different simulation scenarios: two types of soils and two terbuthylazine application patterns
Summary
Pesticides are “substances or organisms used to eliminate, incapacitate, modify, inhibit growth of or repel pests. They can be natural or synthetic chemicals, mixtures of these, or living organisms that act as biological control agents” [1]. Infiltration processes cause pesticides to infiltrate in the vadose zone. These transport processes are highly dependent on the concentration of pesticide used and its physicochemical characteristics and interaction with the environment. If recharge is high enough the transport process of this kind of organic pollutants from the surface may take a long time till reaching the aquifer. For nonionic chemicals and some other chemicals, the partitioning can be correlated to the octane partitioning coefficient [2]
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