Simulating Nonequilibrium Transport of Atrazine Through Saturated Soil

Abstract

Atrazine, an herbicide widely used for selective control of grassy weeds in the fields where maize is grown, is a potential ground water contaminant in China and, consequently, there is interest in predicting its mobility in agricultural soils. In this study, we determined the nonequilibrium transport characteristics of atrazine in Shahe soil (Beijing sandy loam) using the advection-dispersion equation, and using a sensitivity analysis, we evaluated the contribution of the uncertainty in a given input parameter to the overall uncertainty in model results. The asymmetrical shape and tailing of the atrazine breakthrough curve (BTC) showed that atrazine was subject to nonequilibrium transport. The observed atrazine BTC was best fitted by the chemical nonequilibrium model with a nonlinear least-squares optimization approach. Results from the sensitivity analysis indicated that the retardation factor was the most sensitive parameter. Considering the reliability of the estimated parameters, the best fit to the atrazine BTC was obtained by fixing the retardation factor based on the linear distribution coefficient, and by calculating the dispersion coefficient from the bromide BTC and the average pore water velocity from the measured data; nonequilibrium parameters were the only unknown parameters that were optimized. Model verification procedures were based on best-fit parameters optimized from one soil column experiment and applied to simulate the transport of atrazine in the duplicate experiment. The results showed there was good agreement between measured and simulated concentrations for atrazine leaching in the soil column.

A finite element solution for the fractional advection–dispersion equation

“…More than 98% of the atrazine was recovered during the experiment. The isotherm batch experiment [24] showed that the retardation factor (R) of the atrazine in sandy loamy soil is 1.825.…”

“…A series of experiments have been conducted by Mao and Ren [24] to investigate the adsorption property and transport process of atrazine in homogenous sandy loamy soil column. The soil column is 20 cm in length and 5.0 cm in diameter.…”

Adsorption of Atrazine and Alachlor to Aquifer Material and Soil

“…Adsorption of atrazine governs its fate in soil and groundwater (Mao and Ren, 2004). Atrazine can be adsorbed by clay minerals (Cruz-Guzman et al, 2004), amorphous iron and aluminum oxides (Huang et al, 1984) and organic matter (Godskesen et al, 2005;Chefetz et al, 2004;Weber et al, 2004).…”

Desorption of Heavy Petroleum Oils and Heavy Metals from Soils by Flushing Agents

“…분배계수는 soil flushing에서 탈리 된 오염물질의 mass transport를 모델링할 때 이송매개인 자인 지연계수(retardation factor)를 도출하는 상수로 사용 된다 (Mackay et al, 1996). 또한 분배계수는 이송매개인 자 중 타 인자에 비해 민감도가 크게 달라지기 때문에 오염물질과 세정제 사이의 기초 연구는 매우 중요하다 (Mao and Ren, 2004). 기존의 연구에서는 유·무기 오염 물질에 대하여 물과 토양 사이에서의 흡착에 따른 분배계 수의 결정, 흡·탈착 반응에 따른 비가역적인 이력현상 (hysteresis)을 고찰하는 연구가 다수 진행되었다 (Arias et al, 2006;Camargo et al, 2007;Santana-Casiano and Gonzalez-Davila, 1992 and Yong, 2006).…”