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ABSTRACT: Atmospheric emission of volatilepesticides can be a significant source of airpollution. A field study was conducted to reduce1,3-dichloropropene (1,3-D) emission by applying thechemical via subsurface drip irrigation with a reduceddosage (4.7 g m-2 or 47 kg ha-1). Comparisons were made between ashallow drip application with the plot covered with apolyethylene film, a deep drip application and aconventional shank injection (at 11.2 g m-2) withthe plots left as bare soil surface. For eachtreatment, seven replicated active flux chambers wereused continuously to measure 1,3-D loss until nomeasurable emission was found. Results indicated thattotal 1,3-D emission loss was over 90% for the shankinjection, and 66 and 57% for the shallow and deepdrip plots, respectively. The emission loss wasextremely high for shank injection since about 80%were lost from the bed furrows where the slantedshanks left uncompacted fractures. On mass basis, theshank plot lost 10.4 g m-2, whereas the shallow-and deep-drip plots lost 3.1 and 2.7 g m-2,respectively. Applying 1,3-D using subsurface dripirrigation with reduced dosage has a great potentialfor emission reduction.
Water Air and Soil Pollution 03/2001; 127(1):109-123. · 1.63 Impact Factor
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Environmental Science and Technology 07/1995; 29(7):1816-21. · 5.23 Impact Factor
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ABSTRACT: A Windows-based graphical user interface program (DripFume) was developed in MS Visual Basic (VB) to utilize a two-dimensional multi-phase finite element pesticide transport model to simulate distribution and emission of volatile fumigant chemicals when applied through drip irrigation or shank injection. The program provides an intuitive user interface by linking databases with default soil and chemical properties to predict subsurface distribution patterns and surface volatilization losses of soil fumigants under selected field configurations and application regimes. The interface program was configured to simulate up to three chemicals simultaneously to accommodate the need of fumigation with multiple chemicals. Physical and chemical properties of cis- and trans-isomers of 1,3-dichloropropene and chloropicrin for a typical medium-textured soil were given as default values in the model input. Properties of other soil fumigants can be easily substituted as input options during program initialization. A database containing transport properties of 12 soil groups (from clay to sand) were created in DripFume as selectable sets of input values. Substitution is also allowed if properties of an individual soil are known. The VB output includes a normalized run-time volatilization flux display and selections in post-processing using MS Excel linked by VB. Output options from the post-processing VB/Excel program include data and graphs of cumulative volatilization loss, volatilization flux density, concentration profile by time for a selected location or by location for selected lapsed times after fumigant application. Although there are still limitations in selectable field configurations, the program should be useful in helping pesticide specialists, farm managers, or policy makers to optimize the depth, rate, and duration of fumigant application to achieve the highest possible distribution uniformity and the lowest volatilization loss.
Computers and Electronics in Agriculture.
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ABSTRACT: Best management decisions in soil fumigation require informed management selections of soil type, field geometry, application dosage, and depth to maximize fumigant distribution for efficacy and minimize off-site transport for environmental safety. An efficacy- or exposure-based concentration-time exposure index (CTEI) was used to serve as a continuous quantitative efficacy assessment for soil fumigation by subsurface drip irrigation using numerical model simulations. The CTEI was defined as the ratio between the soil volume where concentration-time (CT) exceeded a threshold value for a particular pest-fumigant combination and the total soil volume required for fumigation treatment. Applications of CTEI as a simple efficacy index were demonstrated by simulating combinations of three soil types (loam, sandy loam, sand); three field configurations consisting of 102- and 203-cm-wide bed systems and a flat surface system; three application depths (15, 30, 45 cm); and two application rates (82 and 327 kg ha(-1)) for 1,3-dichloropropene against citrus nematode (Tylenchulus semipenetrans) using a threshold air-phase CT value of 12 microg h cm(-3) obtained from a separate field study. For soil fumigation by subsurface drip irrigation, the order of importance in optimizing CTEI was soil type, depth of application and depth of treatment, dosage, and field configuration. Model simulation using CTEI as a numeric efficacy index can be an effective alternative to assist in the planning of field trials for making final management decisions concerning soil fumigation or other pesticide applications.
Journal of Environmental Quality 33(2):685-94. · 2.32 Impact Factor
