Environ. Sei. Technol. 1993, 27,2236-2243
Air and Fog Deposition Residues of Four Organophosphate Insecticides Used on Dormant Orchards in the San Joaquin Valley, California James N. Selber,’ Barry W. Wllson, and Michael M. McChesney
Department of Environmental Toxicology, University of California, Davis, California 95616 Sampling was conducted a t a station near Parlier, CA, in the winter, 1989, to assess the airborne concentrations of organophosphorus (OP) insecticides used as dormant sprays on deciduous fruit and nut orchards in the general region. For 24-h air samples, concentrations ranged to above 100ng/m3for parathion, chlorpyrifos, and diazinon, and somewhat less (maximum ca. 30 ng/m3) for methidathion. Nighttime air residues were generallyhigher than daytime residues, perhaps reflecting a lowered inversion boundary layer and calmer wind conditions at night. Oxons of the four OPs tended to be in higher amounts relative to the parent thions in day vs night samples, suggesting photochemical oxidant involvement in their formation. Fogwater sampled during the same general period contained residues of all four OPs and their oxons whether sampled with a Teflon-brand strand fog collector or by collecting tree drip moisture. Oxons tended to be higher in the tree drip, suggesting involvement of the tree surface in their formation. Potted parsley plants set out during the period contained measurable OP residues, suggesting deposition by wet processes or dry vapor exchange. The reported residue content of red-tailed hawks collected in the general vicinity suggested that deposition to a nontarget wildlife organism also may have occurred. Introduction
Sprays containing a mixture of a highly refined petroleum oil of low volatility, an organophosphate (OP) insecticide, and often a fungicidal copper salt are used in dormant applications to control a host of pest organisms, including San Jose scale (Quadraspidiotusperniciousus) and peach twig borer (Anarsia lineatella), in deciduous fruit and nut trees in California. The OPs employed include chlorpyrifos, diazinon, methidathion, and parathion, although the latter pesticide was banned for this use in 1991arid will no longer be available. The principal application areas include the extensive almond, peach, nectarine, and other fruit orchards in the San Joaquin and Sacramento Valleys. From reported use data ( I ) , parathion has been the chemical in highest use, and almond orchards have received the greatest number of applications (Table I). We previously showed that pesticide use on an extensively grown crop-rice-could result in areawide air contamination in California’sSacramento Valley (2).Also, from prior sampling of the atmospheres of the wintertime high-inversion fogs which predominate in the Central Valley (3))we found residues of a number of pesticides and, most frequently, the same OPs used in the dormant spraying of orchards (4-6). The same group of chemicals has been among the pesticides that appear irregularly as
* Address correspondence to this author at his present address: Center for Environmental Sciences and Engineering, University of Nevada, Reno, Reno, NV 89557. 2236
Enrlron. Scl. Technol., Vol. 27,
No. 10, 1993
Table I. Reported Applications of Organophosphate Dormant Spray Chemicals (kg) in 1986, 1987, 1988, and Jan-June 1990 in California. orchard
1986
almonds peaches nectarines
16 177 874 528
almonds peaches nectarines
21011 733 665
almonds peaches nectarines
17945 7669 1271
almonds peaches nectarines
139 155 31 187 26 787
a
1987
1988
1990 (Jan-June)
Chlorpyrifos 17442 17520 624 860 577 484 Diazinon 32270 49886 684 2529 544 579 Methidathion 37627 22719 6437 4721 1544 1700 Parathion 174 119 300 949 27311 32319 22 596 27 863
41 077 4419 11 594 102 935 9651 5928 21 240 5198 1790 136 064 53 384 24 417
Taken from ref 1. 1989 data are not available.
residues on wintertime row crops grown in the Central Valley, suggesting inadvertent contamination either from wet deposition or from vapor exchange and/or particle settling (7). Measurements of cholinesterase depression among orchard-dwelling red-tail hawks (Buteo jamaicensis, RT) suggested contact with OPs, which has now been confirmed by several lines of evidence (8). Finally, air and wet deposition samples collected in the winter months in California’s Sierra Nevada show traces of the same group of chemicals, again pointing toward orchard use as a source (9). In order to provide more concrete evidence for a connection between air residues and orchard use, quantitative data were collected on airborne levels of these chemicals during a month of primary use by sampling at the University of California’s Kearney Agricultural Research and Extension Center (Kearney Center), located in the San Joaquin Valley in a predominate vineyardorchard agroecosystem. No significant OP dormant sprays were made at the Center itself until the latter stages of our sampling period, so the airborne residues measured at the Center must have moved there by air transfer from orchards no closer than 1 km and perhaps up to 100 km or more away. We also collected fogwater deposition samples and analyzed parsley sentinel plants to further study the deposition potential for the OPs. We are not aware of any other major uses of these OPs in the Central Valley, outside of dormant orchards, during the wintertime sampling period, so the assumption has been made that the origin of OP residues is primarily from orchard use. Methods
Site Selection. The UC Kearney Agricultural Research and Extension Center, located near Parlier, CA, comprises 134 ha of primarily experimental fields, vineyards, and 0013-936X/93/0927-2236$04.00/0
0 1993 Amerlcan Chemlcal Soclety
ORCHARDS
+200m
ORCHARDS
Flgure 1. Diagram of sampling sites at the Kearney Center and the relationship between the Center and its adjacent agricultural fields.
orchards within the larger confines of a predominately orchard-vineyard agroecosystem in southern Fresno County. At a ca. 100- X 100-m section of the Center, which is set aside for weather [California Irrigation Management Information System (CIMIS)] and air pollution [Fresno County Air Pollution Control District] data collection, ambient air sampling stations were established, ambient fog samples were collected, and potted parsley plants were located (Figure 1). Tree drip samples were taken during fog events from near the Center’s headquarters (an area with buildings, lawn, and driveways) ca. 300 m northwest of the CIMIS site. A map indicating the location of these sampling sites within the Center and in relation to the commercial agricultural land adjacent to the Center is shown in Figure 1. Sampling. Air sampling was conducted through duplicate XAD-4 resin-charged Teflon (du Pont) cups held on a sampling mast described in detail elsewhere (2). Each sampling cup contained 70 cm3of XAD-4 resin precleaned by washing continuously with deionized water to remove fines, by washing with 0.25 N hydrochloric acid followed by rinsing with several bed volumes of distilled water until the pH of the rinse was about 5, and by successive 24-h Soxhlet extractions withmethanol (2X), ethylacetate, and methylene chloride. The resin was then dried for 48 h in a vacuum oven at room temperature. Once the sample was charged in the sampling cups, air flow was adjusted to ca. 70 L/min through each cup. Flow rates were read and recorded, and other protocol was ccjnducted as previously described in ref 2. One sampling mast was dedicated to obtaining 24-h ambient samples; a second was used for day/night sampling, for which the day component was collected from ca. 0700-1700 (10 h) and the night component from ca. 1700-0700 of the following
day; and a third was used to collect samples for irregular intervals during an event of special interest (fog episodes us clear day, sunny us overcast period, etc.). These three sampling masts were located at the CIMIS site (Figure 1). Fogwater sampling was done using a truck-mounted, fan-powered Teflon strand collector (10,11),described in detail elsewhere (12). This sampler draws air at the rate of 4400 m3/h and results in collection of up to 1 L/h of fogwater in a dense fog. Interstitial air was sampled at a rate of 45-50 m3/h using a high-volume dichotomous air sampler (12) with an XAD-4 resin trap in the air sample diversion segment. The truck was parked, and the engine was not running. Fogwater was also collected by placing a 1-m X 1-m galvanized sheet metal collection basin below tree drip lines. Samples were collected during moderate to heavy fog events from below deciduous shade trees near the west end of the Center’s main office building, below pine trees east of the office complex,and below eucalyptus trees north of the CIMIS station. Gallon-size glass bottles equipped with stainless steel funnels were placed below the drop collectors. Parsley plants (Capitol Nursery, Sacramento, CA) were kept in a greenhouse until they were deployed at the CIMIS site by being placed on a table 0.5 m above the ground. The plants were left in this open condition until they were retrieved for analysis. The plants used were determined to have an average external water holding capacity of ca. 20 g. Plants were sampled by cutting at the root, and only the aerial part was placed in a glass sample jar and then frozen for subsequent analysis. Sample Preparation. Air XAD-4 resin samples (70 cm3) were extracted by swirling with ethyl acetate, using two portions of 80,50, and 40 mL, and then filtered through Whatman No. 1filter paper and concentrated to approximately 4 mL by rotary evaporation, essentially as described previously (2). Water samples (fogwater, tree drip, and rain) were filtered through a nitrogen-pressurized Millipore system containing a preweighed glass fiber filter backed with a 0.2-hm Teflon filter. Extraction was according to the method of Seiber et al. (13). To an aliquot of the sample was added 20 g/L of sodium sulfate. The water was extracted three times with volumes of methylene chloride corresponding to one tenth of the water volume. Extracts were then combined and concentrated to 4 mL by rotary evaporation and then exchanged into ethyl acetate solvent for GC analysis. For each set of water samples, a glassware and reagent blank (1L of distilled water run through the same extraction) and a system blank (1L of distilled water run through the nitrogen filter system and extracted the same way as for the samples and glassware blank) were run. The fogwater collected by the truck-mounted sampler and that collected beneath the tree drip lines were prepared similarly, except that tree drips from the pine and eucalyptus trees gave emulsions during solvent extraction which required centrifugation. Weighed parsley plant samples were blended with 200 mL of benzene using a Tissuemizer at hi,gh speed for 1 min. Extracts were filtered through anhydrous sodium sulfate, the volume was recorded, and the solvent was concentrated to 5 mL. Cleanup on a prewashed 5.5-g Florisil column, eluted with 50 mL of 8% ethyl ether in benzene, then followed. Eluent was concentrated just to Envlron. Sci. Technol., Vol. 27, No. I O , 1993 2237
-__-__
-^__(__
Table 11. Trapping Efficiencies (%) for OPs Introduced to XAD-4 Resin through the Inlet Air8
100-pug spike
:i
av
SD
av
SB
chlorpyrifos diazinon diazinon oxon methidathion parathion
79.0 79.7
4.9 3.1
80.6 61.4
20.0 6.6
80.9 76.5 47.7 82.7 72.2
5.2 7.1 3.0 4.4 7.1
50 Limin flow rate, 24-h duration. --__
Table 111. Residues (ng/m3) of Four Organophosphate Pesticides and Their Oxons in XAD-4 Resin Air Samplers Operated for 24 h, Jan 11-29, 1989, at the Kearney Center
16
Response
Flgure 2. Gas chromatogram of standards of four OPs and their respective oxons on DB-210 column.
dryness and exchanged to ethyl acetate, and the volume was adjusted for GC analysis. GC Analysis. Samples were analyzing using a HewlettPackard Model 5710A GC equipped with an NP-TSD detector, a 30-m megabore (0.53 mm) DB-210 column, and a glass injector liner (J&W Scientific, Folsom, CA). Flow rates were 1 2 (helium carrier), 20 (helium makup), 3 (hydrogen), and 60 mL/min (air). Column temperature was held at 193 "C for 4 min and then programmed to 220 "C at 2 "Clmin. Injector and detector temperatures were both 250 "C. A five-point standard curve was constructed from constant volume (2.4 pL) injections of standards using peak areas read from a Hewlett-Packard Model 3390A integrator. Figure 2 provides a representative chromatogram of standards. Confirmation of some samples was conducted using a Hewlett-Packard 5890A GC with a 5970C mass selective detector in the selective ion monitoring (SIM) mode. The column was an HP-1,11 m X 0.2 mm. Carrier gas (helium) flow rate was 0.68mLlmin. Column temperature was held for 2.5 min at 50 "C and then programmed to 180 "C at 30 "Clmin, and then to 195 "C at 5 "Clmin, and then to 260 "Cat 15"Clmin. The retention times and ions selected were as follows: diazinon, 10.63 min, 304, 139, 137 mlz; paraoxon, 11.65min, 275,139,109 mlz;chlorpyrifos oxon, 12.39 min, 270, 242 mlz; parathion, 12.48 min, 291, 145 mlz; chlorpyrifos, 12.58 min, 199,197 mlz;methidathion, 13.73min, 302,145,85 mlz;methidathion oxon, 13.1min, 145 mlz.
Results We collected 24-h ambient air samples for 17 days in January, during the most intensive period of dormant orchard spraying. Samples were collected in duplicate on XAD-4 resin traps capable of simultaneously trapping the four OPs and their corresponding oxons. Recoveries were good for the parent OPs when spiked to the inlet air of the sampler at levels corresponding to 1.3and 7.0pg/m3(Table 11). The recovery of diazinon oxon was less than that for the thions, but it was still reproducible. We did not conduct recoveries for the oxons of chlorpyrifos, methidathion, and parathion, but, from previous studies of some of these same compounds (14),we anticipated recoveries similar to those for diazinon oxon. 2238
500-pg spike
compound
Envlron. Scl. Technol., Vol. 27, No. 10, 1993
chlorpyrifos diazinon methidathion parathion parent oxon parent oxon parent oxon parent oxon I_____
dates Jan 11-12 Jan 12-13 Jan 13-14 Jan 14-15 Jan 15-16 Jan 16-17 Jan17-18 Jan 18-19 Jan 19-20 Jm21-22 Jm22-23 Jan23-24 Jan 24-25 Jm25-26 Jan 26-27 Jan 27-28 Jan28-29 averagea sd
95rc confidence interval
41.5 diazinon > parathion > paraoxon > methidathion, in agreement with that published previously for Central Valley fog ( 4 , 5 ) . However, the magnitude of the 2240
3.0 1.5
