The Pest Detection/Emergency Projects (PD/EP) branch of the California Department of Food and Agriculture (CDFA) uses diazinon as a ground treatment to kill pre-pupal to adult emergent stages of Mediterranean and Oriental fruit fly in soil. Diazinon AG500® is applied at a rate of 5 lb ai/acre (5.6 kg/ha) on the ground under the host tree canopy from the trunk out towards the drip line. Water is applied to a point just before puddling or runoff occurs. Diazinon soil treatment consists of two or three applications made at intervals of at least 14 days apart.
Potential exposure of children exists via dermal contact and/or oral ingestion of diazinon-treated soil and turf. Diazinon residues from soil applications using mostly a granular formulation were previously monitored in Sacramento County during the Japanese beetle eradication program (Segawa and Powell, 1989). The highest diazinon residues were found one day after application in the turf-thatch at 21 to 1700 mg/m2 and upper soil layers at 12 to 610 mg/m2. Diazinon was not detected after 21 days. Investigations on the fate of chlorpyrifos and dichlorvos applied to soil-turf showed that these insecticides dissipated to "estimated safe re-entry level" within 2-6 hours after application on various types of turf (Goh et. al., 1986 a and b).
The objectives of this study are: 1) to determine diazinon and diazoxon residues in the top one cm of surface soil and to determine dislodgeable and total residues (the sum of dislodgeable and internal residues) in turf-thatch after each diazinon application and; 2) to determine dissipation curves for diazinon and diazoxon for both media using values obtained from the first and third applications. The study will be conducted under controlled field conditions in Sacramento County, California.
This study will be conducted by the Environmental Hazards Assessment Program (EHAP) under the general direction of Roger Sava, Senior Environmental Research Scientist. Key personnel are listed below:
Project Leader: Blanca Rodriguez
Field Coordinator: Clarice Ando
Senior Staff Scientist: John Troiano
Laboratory Liaison: Nancy Miller
Chemical Analysis: Paul Lee
Soil Characterization: Cindy Garretson
Experimental Design/Data Analysis: Rosie Gallavan
Public and Agency Information: Dr. Kean Goh
Questions concerning this monitoring program should be directed to Dr. Kean Goh at (916) 654-1141 and FAX (916) 654-0539.
IV. EXPERIMENTAL DESIGN / SAMPLING METHODS
Two residences will be selected for monitoring; one site will serve as the soil site and the other residence as the turf site. Each site will be divided equally into four subsites and pesticide application and sample collection will be confined to these areas. Diazinon AG500® (Platte Chemical Co.) and water will be mixed at each site using the same ratio as that used in the PD/EP program to eradicate the Medfly. At each site, two gallons (7.7 L) of de-ionized water will be buffered to a pH of 6.5 using Knapp® buffer and will be mixed with 2.46 fl oz (72.75 ml) of diazinon concentrate. A constant pressurized backpack sprayer with a .76-meter length boom will be calibrated to deliver diazinon at a rate of 5 lb ai/acre (5.6 kg/ha). Three separate diazinon applications will be made to the soil and turf sites at 14-day intervals and shortly following each pesticide application, water will be uniformly applied. The sampling schedule for both media is as follows:
Application 1: Background, immediately after application (prewatering),
1 hour after watering, and days 1, 2, 4 and 8.
Application 2: Background, immediately after application, 1hour after watering.
Application 3: Background, immediately after application, 1hour after watering, and days 1, 2, 4, 8, 12, 16 and 32.
On each application day, the diazinon deposition rate for soil and turf will also be measured and compared to the theoretical deposition rate of 5 lb ai/ac. At both sites, twelve half pint canning jars will be randomly set at ground level and will be collected immediately after application (prewatering). Samples will be sealed with a Teflon®-lined lid and transported to the laboratory on dry ice (-70°C). In addition, one tank mix will be collected on each application day for each site to determine diazinon and diazoxon concentrations.
All irrigation and light rainfall events will be reported. In the anticipation of heavy rainfall events which may result in runoff water, sites will be covered with plastic sheeting.
At the soil site, a single composite soil sample will be collected at each of the four subsites. Samples will be collected by inserting a 6.3-cm internal diameter (i.d.), stainless steel cylinder into the soil to a depth of one cm. The soil cores will be placed into a glass jar and sealed with an aluminum foil lined lid. The number of soil cores collected and corresponding soil weight will be recorded on each sample's chain of custody (COC). In the field, samples will be stored on dry ice and maintained at -70°C until extraction. Quality control (QC) soil samples will be collected on 14 of the 20 sampling periods and will be split for diazinon analysis with CDFA, the primary laboratory, and a second laboratory.
Before the first diazinon application, approximately 200 g of soil will be collected at the soil site for the determination of texture, pH, and organic carbon content.
At the turf site, a single composite turf-thatch sample will be collected at each of the four subsites. Samples will be collected using a rubber mallet to drive a 6.3-cm (i.d.), stainless steel cylinder approximately 10 cm into the soil. The cylinder containing the soil/turf plug is removed from the earth, and then the core is removed from the cylinder using an extruder. The soil portion will be cut off using clean steel scissors. The turf-thatch will be placed into a wide-mouth, glass jar and sealed with an aluminum foil lined lid. Each composite turf-thatch sample will weigh a minimum of 25 g. The number of turf-thatch cores collected and the corresponding turf-thatch weight will be recorded on each sample's COC.
V. CHEMICAL ANALYSIS / QUALITY CONTROL
CDFA Laboratory will analyze soil samples for diazinon and diazoxon residues The CDFA method detection limit (mdl) for both compounds in soil is 0.25 µg/sample. The soil moisture content will also be reported by CDFA Laboratory. Soil texture will be determined by using the hydrometer method (Bouyoucos 1962) and soil organic matter will be determined using dichromate reduction with silver sulfate (Rauschkolb 1980). Soil pH will also be reported.
Turf-thatch samples will be analyzed for dislodgeable and internal residues of diazinon and diazoxon by CDFA Laboratory with and mdl of 0.25 µg/sample. The moisture content of the turf-thatch will also be reported.
VI. DATA ANALYSIS
For both media, residues will be expressed as weight of chemical/weight of sample and weight of chemical/surface area on both a dry and a wet-weight basis. Dissipation curves for soil and turf-thatch will be estimated for both diazinon and diazoxon for the first and third applications.
Sample Collection September to December, 1993.
Chemical Analysis September to December, 1993.
Data Analysis November to December, 1993.
Draft Report February, 1994.
Final Report March, 1994.
Bouyoucos, G.J. 1962. Hydrometer method improved for making particle size analyses of soils. Agronomy J., 54:464-465.
Goh, K.S., S. Edmiston, K.T. Maddy, D.D. Meinders, S. Margetich. 1986a. Dissipation of dislodgeable foliar residue of chlorpyrifos and dichlorvos on turf. Bull. Environ. Contam. Toxicol. 37:27-32.
Goh, K.S., S. Edmiston, K.T. Maddy, S. Margetich. 1986b. Dissipation of dislodgeable foliar residue for chlorpyrifos and dichlorvos treated lawn: implication for safe entry. Bull. Environ. Contam. Toxicol. 37:33-40.
Rauschkolb, R.S. 1980. Soil analysis method S:18.0, Organic matter dichomate reduction. In California Fertilizer Association, California Soil Testing Procedures Manual.
Segawa, R.T., S. J. Powell. 1989. Monitoring the pesticide treatments of the Japanese beetle project, Sacramento County, California, 1983-1986. Vol. III: Diazinon. California Environmental Protection Agency, Department of Pesticide Regulation (Formerly California Department of Food and Agriculture), Sacramento, CA, EH89-5, 44pp.
Soil Samples (20 sampling periods x 4 subites) = 80
Turf Samples (20 sampling periods x 4 subsites) = 80
QC Soil Split Samples (14 sampling periods x 4 subsites) = 56
Mass Deposition Samples..(3 applications x 2 media x 12 samples) = 72
Tank Samples (3 applications x 2 media x 1 sample) = 6
Soil Physical-Chemical Samples (2 samples) = 2
Total Samples 296