With the increased use of the agricultural fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP), it is important that strategies to reduce emissions of these fumigant from soil to the air are assessed to protect air quality. Using an established soil column approach, the following emission reduction strategies were compared to a control: (1) spray application of ammonium thiosulfate to the soil surface; (2) deep injection at 46 cm depth; (3) high density polyethylene sealed over the soil surface; (4) virtually impermeable film sealed over the soil surface; and (5) irrigation with ammonium thiosulfate solution. Relative to the control, 1,3-D emissions were reduced by 26.1, 1.0, 0.01, 94.2, and 42.5%, for treatments 1 through 5, respectively. For CP the reductions were 41.6, 23.3, 94.6, 99.9, and 87.5% for treatments 1 through 5, respectively. Virtually impermeable film gave the greatest reductions for both fumigants, while HDPE was very effective only for CP. Despite offering less significant emission reductions, the lower cost alternatives to tarping, particularly irrigation with ATS solution, may offer substantial benefit where tarping is not economically viable.

A field experiment was conducted to measure subsurface movement and volatilization of the 1,3-dichloropropene (1,3-D) after shank injection to an agricultural soil. Aerodynamic, integrated horizontal flux and theoretical profile shape methods were used to obtain fumigant flux density and cumulative emission values. The volatilization rate was measured continuously for 16 days and the range in the daily peak volatilization rates for the three methods ranged from 18 to 60 μg m s. The total 1,3-D mass that volatilized to the atmosphere was approximately 44-68 kg ha, or 10-15% of the applied active ingredient. This represents approximately 30-50% of the total emissions observed in recent field and field-plot studies. Significant reductions in volatilization of 1,3-D are possible when repeated surface irrigations are applied to a field shortly after fumigation and continuing for several days.

A field experiment was conducted to measure subsurface movement and volatilization of the 1,3-dichloropropene (1,3-D) after shank injection to an agricultural soil. Aerodynamic, integrated horizontal flux and theoretical profile shape methods were used to obtain fumigant flux density and cumulative emission values. The volatilization rate was measured continuously for 16 days and the range in the daily peak volatilization rates for the three methods ranged from 4 to 23 μg m s. The total 1,3-D mass that volatilized to the atmosphere was approximately 15–36 kg ha, or 3–8% of the applied active ingredient. This represents approximately 10–25% of the total emissions observed in recent field and laboratory studies. Significant reductions in volatilization of 1,3-D are possible when composted municipal green-waste material is incorporated into the surface soil.

A field experiment was conducted to measure subsurface movement and volatilization of 1,3-dichloropropene (1,3-D) after shank injection to an agricultural soil. The goal of this study was to evaluate the effect of sprinkler irrigation on the emissions of 1,3-D to the atmosphere and is based on recent research that has shown that saturating the soil pore space reduces gas-phase diffusion and leads to reduced volatilization rates. Aerodynamic, integrated horizontal flux, and theoretical profile shape methods were used to estimate fumigant volatilization rates and total emission losses. These methods provide estimates of the volatilization rate based on measurements of wind speed, temperature, and 1,3-D concentration in the atmosphere. The volatilization rate was measured continuously for 16 days, and the daily peak volatilization rates for the three methods ranged from 18 to 60 microg m(-2) s(-1). The total 13-D mass entering the atmosphere was approximately 44-68 kg ha(-1), or 10-15% of the applied active ingredient This represents approximately 30-50% reduction in the total emission losses compared to conventional fumigant applications in field and field-plot studies. Significant reduction in volatilization of 1,3-D was observed when five surface irrigations were applied to the field, one immediately after fumigation followed by daily irrigations.

Introduction. The State regulatory agencies' current VOC inventories are based on assuming that 100% of the VOC portion of an applied pesticide is lost to the atmosphere. This tends to overestimate the VOC loading since pesticides are affected to some degree by irreversible sorption, and abiotic and biotic degradation that tends to reduce emissions. While assuming 100% emission may be convenient, this approach is not a suitable substitute for actual emission measurements under field-relevant conditions. As new stricter rules governing ambient ozone levels are implemented, regulations will be placed on activities that produce ozone. In regions with significant agricultural production, VOC emissions from soil fumigation will likely be considered. Therefore, research is needed to accurately determine the true level of VOC emissions from soil fumigation and to develop methods to reduce emissions to low levels. Failure to do so may cause agricultural producers to face potentially restrictive control strategies, which may cause a reduction in profit or force growers to cease food production. A field experiment was conducted to measure the volatilization rate of 1,3-dichloropropene (1,3- D) after shank injection. 1,3-D has relatively high volatility and water solubility and relatively short field half-life. After fumigation, residual 1,3-D may be detectable in soil for several weeks. There have been few published field experiments describing efforts to measure field-scale emissions of 1,3-D after shank injection or for situations where irrigation water is applied shortly after application. The experimental data reported from this study provides state regulators and the scientific community with important information on emissions from soils. Location. The field site was located in near Buttonwillow, CA. The soil type was a Milham sandy loam (fine-loamy, mixed, thermic Typic Haplargids). The field experiment began on August 31, 2005 and ended September 16, 2005. Two weeks prior to the start of the field

Propargyl bromide (3-bromopropyne, 3BP) is a potential alternative for methyl bromide. Little information is available about its efficiency in controlling pests. The purpose of this paper is to estimate the 3BP dose required for killing three pests and to compare the efficiency of water management approaches to that of fumigation. The pests, Fusarium oxysporum Schlecht (fungus), Echinochloa crus-galli (L) Beauv (grass) and Tylenchulus semipenetrans Cobb (nematode) were exposed to different 3BP concentrations in a sandy loam at 30 degrees C in a closed system. The lethal dose for killing 90% of the population (LD90) was calculated from the total applied mass, and varied from 0.3 microg g(-1) soil for the nematode, 3 microg g(-1) for the grass, and 9 microg g(-1) for the fungus. The concentration-time index for killing 90% of the population (CT90) was 11 microg g(-1) h for the nematode, 112 microg g(-1) h for the grass and 345 microg g(-1) h for the fungus. 3BP seems as efficient as other fumigant alternatives in controlling these pests. Using an open system, it was shown that the volume of soil in which the pests were controlled varied for different irrigation managements. Even 96 h after fumigation (with a concentration 10 times higher than would potentially be applied in the field), more than 20% of the soil volume had not reached the fungus and grass CT90 of the non-irrigated soil. The soil underneath the furrow and the bed reached CT90 only slowly in all irrigated treatments even though techniques for increasing efficiency were used (tarping, surface sealing with water and high application rate).

Fumigants are used for control of nematodes, fungi, weeds, and insects in high-cash-value crops. Because of their high volatility, a large fraction of the applied mass may be volatilized from the soil surface following application. Emission reduction strategies are needed to prevent adverse human or environmental health impacts. Some emission-reduction strategies, such as tarping the soil surface with impermeable plastic, increase containment of fumigants in the soil. The resulting fumigant residues could cause atmospheric contamination once the tarp is disrupted, groundwater contamination if leaching is allowed, or phytotoxicity to the crop planted following fumigation. Previous research has shown that thiosulfate compounds, including ammonium thiosulfate (ATS), abiotically react with and detoxify halogenated fumigants in soil and water. In these experiments, we investigated subsurface application of ATS to reduce fumigant concentrations in the root zone, preventing off-site transport following fumigation. Results indicated that halogenated fumigants were dissipated more rapidly in soil receiving ATS application compared to those receiving water only. First-order dissipation half-lives were less than or equal to1 day for the halogenated compounds 1,3-dichloropropene and propargyl bromide. For methyl isothiocyanate, a non-halogenated fumigant that does not undergo reaction with ATS, application of ATS had no impact on the rate of dissipation in soil. These results suggest that subsurface application of ATS may be useful for the root-zone remediation of halogenated compounds.

Propargyl bromide (3‐bromo‐propyne, 3BP) is a potential replacement for the soil fumigant methyl bromide. Since little is known about its movement in soil, a study was conducted to compare the volatilization and movement of 3BP in the soil profile for different irrigation treatments. A rectangular soil column was used to simulate a bed–furrow system. The surface of the bed was covered with high‐density polyethylene (HDPE) plastic (i.e., a tarp). The furrow was left uncovered. Multiple volatilization chambers were used to measure emissions from the furrows, the slopes of the bed, and the bed. The soil was fumigated by injecting 1.0 mL of 3BP to the center of the column. Three treatments were studied, no irrigation, a single 5‐h surface irrigation 24 h after fumigation, and a 2‐h daily surface irrigation. Volatilization was about three times greater from nonirrigated soil. Irrigation and higher initial soil moisture content were more effective in controlling 3BP volatilization than the use of a HDPE tarp. Volatilization and degradation were similar for both irrigation treatments, but the 2‐h irrigation had the advantage of requiring one‐third less water. Volatilization rates from the slopes of the bed were lower than from the bed surface. To obtain accurate total mass, volatilization chambers should cover the whole bed–furrow system. Short advective gas and liquid fluxes created by the irrigation had pronounced and prolonged effect on 3BP distribution and degradation. Henry's Law could not be used to predict the 3BP distribution pattern in the liquid phase even long after the irrigation ceased.

The gas permeability of plastic films is important in packaging, containment, and agricultural fumigation. Recently, an approach for estimating the mass transfer coefficient of vapors across a film was presented by Papiernik et al. (2001). The mass transfer coefficient is an intrinsic property of a film-chemical combination, independent of the concentration gradient maintained across the film. Here we describe an apparatus useful for obtaining permeability data; the model of Papiernik et al. (2001) may be fitted to the data to determine mass transfer coefficients. The assembled equipment provides a sealed permeability cell, where a sample of the film to be tested is sandwiched between two static half-cells. Vapor is spiked to one side of the film and the concentrations in the spiked and receiving chamber are monitored until equilibrium. A sealed system is required for this approach; the permeability cells described here were gas-tight for >40 d. This approach produces reproducible measures of mass transfer coefficients that are not dependent on the size of the experimental apparatus. Model parameters were similar when fitted simultaneously as when determined independently from the same data set.

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.

Atmospheric emission of the soil fumigant 1,3-dichloropropene (1,3-D) is of environmental concern because of its toxicity and carcinogenicity. Thiosulfate fertilizers have been found to rapidly transform 1,3-D in soil to non-volatile ions which are less toxic. We investigated the use of surface application of ammonium thiosulfate (ATS) for reducing 1,3-D volatilization. In packed soil columns, emission of 1,3-D applied by sub-surface injection decreased with increasing ATS application rate and the amount of water used far delivering ATS. When ATS was applied in 9mm water at 64g m(-2), total 1,3-D emission was reduced by 61%. The reduction was 89% when ATS was applied at 193g m(-2). Bioassays showed that ATS application did not affect the effectiveness of 1,3-D for controlling citrus nematodes. In field plots where a 1,3-D emulsified formulation was applied via sub-surface drip, surface spray of ATS reduced 1,3-D emissions by 50%, and by 71% when the surface was also covered with polyethylene film. ATS application had no effect on the efficacy of root-knot nematode control or tomato yields. These results suggest that surface application of thiosulfate fertilizers may be a feasible and effective strategy for minimizing 1,3-D emissions. (C) 2000 Society of Chemical Industry.

Chloropicrin (CP) is used in fumigation of soil-borne pests. Because of its high volatility and toxicity, atmospheric emission of CP during soil application may become a source of air pollution. We investigated degradation of CP in three different soils as a function of soil temperature and moisture conditions, and evaluated its volatilization against methyl bromide (MeBr) from packed soil columns. Chloropicrin degraded much faster than MeBr in the same soil, mainly via microbial degradation. Degradation of CP accelerated as soil temperature increased, but was relatively independent of changes in soil moisture. When the soil surface was uncovered, overall volatilization loss of CP was similar to that of MeBr. Covering the soil surface with a polyethylene or high-barrier film was much more effective in reducing volatilization of CP than MeBr. Therefore, surface covers may be used in sensitive areas to reduce human exposure to CP.

Fumigation for soilborne pest and pathogen control is under close scrutiny because of its potential hazardous effects on the environment and on human health. Therefore, reduced-risk yet effective fumigation practices are imperatively needed. We have developed a column system that allows an integrated evaluation of emission potential and efficacy of fumigants. The system consists of a large, packed soil column and a sampling chamber for measuring fumigant emissions at the soil surface. Nematodes (or of her pests) can be inoculated into the column and their survival may be assayed after the treatment. This approach was used to evaluate the emission of 1,3-dichloropropene (1,3-D) and its efficacy against the citrus nematode Tylenchulus semipenetrans when ammonium thiosulfate, a 1,3-D degrading fertilizer, was applied at the soil surface. Results closely comparable to field observations were obtained. Compared with field studies, the proposed method is rapid and inexpensive, and thus may be used for screening fumigation practices that have improved environmental safety and pest control performance.

Rapid and accurate measurement of atmospheric concentrations of highly volatile organic compounds is important in obtaining reliable information for the assessment of environmental pollution or the volatilization mechanisms of the chemicals. Nonmechanized sample collection requires intensive labor and effort, and may cause large random or systematic errors. An automated solenoid switching system has developed to assist in obtaining precise environmental concentrations of highly volatile organic compounds. The design, construction, and operation are described in the paper for potential application in similar studies Using this sampling system, two experiments were conducted to determine atmospheric volatilization flux density of three highly volatile and reactive organic compounds (methyl bromide, 1,3-dichloropropene, and propargyl bromide). The automated solenoid switching system significantly reduced the requirements for labor and time. Results from the two experiments indicate that reliable sample collection was achieved. The automated sampling system was also relatively inexpensive and can be easily modified to accommodate a variety of sources, sampling intervals, and multiple number of solenoid valves.

Emissions of fumigants can be an important source of air pollution at soil fumigation sites, and the high emission rates result partly from the use of application methods that are high in volatilization potential. In this study, we compared volatilization of fumigant 1,3-dichloropropene (1,3-D) from a sandy loam in 60 cm packed columns after applied by different methods. The most volatilization was found with injection into uncovered soil at a shallow depth (e.g., 56% loss fur the 20-cm injection) and application via surface drip irrigation (>90%). Volatilization fluxes and cumulative losses, however, rapidly decreased as the injection depth was increased, and the total loss was only 27% for the 40-cm injection. The commonly used polyethylene plastic was ineffective in reducing the volatilization because of its high permeability to 1,3-D. Water application after the 20-cm injection resulted in substantially reduced volatilization, but the least loss (22%) was obtained when an emulsifiable formulation of 1,3-D, Telone SL. Has drip-applied to the subsurface at 20 cm. Our results indicate that variables most influencing 1,3-D volatilization are injection depth and Hater management, By optimizing these variables, application methods,vith low emission potential can be developed.