Article pubs.acs.org/est
Cite This: Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Spatial and Seasonal Distributions of Current Use Pesticides (CUPs) in the Atmospheric Particulate Phase in the Great Lakes Region Shaorui Wang, Amina Salamova, Ronald A. Hites, and Marta Venier* School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana 47405, United States S Supporting Information *
ABSTRACT: This study examined spatial and seasonal variations of current use pesticdes (CUPs) CUPs levels in the atmospheric particulate phase in the Great Lakes basin. Twenty-four hour air samples were collected at six sites (two urban, two rural, and two remote) in 2015. The concentrations of 15 CUPs, including nine pyrethroid insecticides, four herbicides, one organophosphate insecticide, and one fungicide, were measured. The total CUPs concentrations were higher at the urban sites (0.38−1760 pg/m3) than at the rural and remote sites (0.07−530 pg/m3). The most abundant CUPs were pyrethroid insecticides at the urban sites. The levels of the other CUPs did not vary much among the six sites, except at the most remote site at Eagle Harbor, where the levels were significantly lower. Chlorothalonil was the most frequently detected CUPs, which was detected in more than 76% of the samples. The atmospheric concentrations of total pyrethroid insecticides and total herbicides were correlated with local human population and developed land use. Significantly higher concentrations of most CUPs were observed in the warmer months than in the colder months at all sites. In addition to agricultural applications, which occur during the warmer months, the CUPs atmospheric concentrations may also be influenced by nonagricultural activities and the urban development.
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INTRODUCTION Pesticides, such as herbicides, insecticides, and fungicides, are applied in large quantities in agriculture to boost crop yields, as well as in urban areas for landscape maintenance and household pest control. Current-use pesticides (CUPs) include over 900 active ingredients, including organophosphate pesticides, pyrethroids, carbamates, neonicotinoids, and sulfonylureas. Although pesticides are designed to kill pests, they have unintended effects on the environment (for example, reduced biodiversity and toxicity to charismatic megafauna) and on humans (for example, developmental and neurological damage).1−3 Evidences of the carcinogenic, neurological, reproductive, and genotoxic effects associated with exposure to CUPs in adults have been previously reported.4,5 In the United States, pesticide use has increased over the last few decades and totaled over 500 000 metric tonnes in 2012, with herbicides accounting for 60% of this total.6 Interestingly, the use of organophosphate pesticides in the U.S. has actually decreased 71% from 2000 to 2012.6 This decrease in organophosphate pesticides use reflects a market shift to other classes of pesticides, which are marketed as safer alternatives for people and the environment. For example, pyrethroid insecticides have been widely used since the early 21st century because of their relatively low toxicity to mammals.7,8 In the U.S., atrazine, chlorothalonil, pendimethalin, chlorpyrifos, and metolachlor are now among the most commonly used CUPs in agriculture,6 whereas permethrin and other pyrethroid insecticides are among the top 10 most © XXXX American Chemical Society
commonly used CUPs in the home and garden sector. In fact, pyrethroid insecticides are widely used for landscape maintenance and mosquito control in both agricultural and nonagricultural areas.9 Herbicides, like pendimethalin and trifluralin, are used to control grass and broadleaf weeds, while chlorothalonil is used to control fungi on agricultural crops and vegetables.10 Chlorothalonil is also used as preemergent herbicide on golf courses and lawns.11 Although its use has become somewhat controversial,12 chlorpyrifos is still a widely used organophosphate pesticide with broad spectrum insecticidal activity, and it is used against insects, mites, and foliar pests.13 CUPs can enter the atmosphere during their application through droplet drift and evaporation or by way of volatilization from crops, wind erosion, and other degradation mechanisms after their application.14,15 During application, up to 50% of the amount applied can be lost to the air in the solid, vapor, or liquid phase.16,17 The partitioning of CUPs between the vapor and the particulate phase in the atmosphere is one key parameter in the understanding of their long-range transport.18 In ambient air, CUPs with vapor pressures above ∼10−2 Pa are found predominantly in the vapor phase, while CUPs with vapor pressures below ∼10−5 Pa are found predominantly in Received: January 8, 2018 Revised: April 26, 2018 Accepted: April 30, 2018
A
DOI: 10.1021/acs.est.8b00123 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology the particulate phase.19 The ability of a pesticide to travel short or long distances through the atmosphere depends on the amount of time it resides in the atmosphere, which in turn is related to the properties of the pesticide, such as its molecular size and weight, as well as meteorological factors.20 It is generally believed that CUPs are relatively more watersoluble, less persistent, and less bioaccumulative than legacy organochlorine pesticides and that using CUPs would result in reduced negative environmental impacts. However, numerous studies have demonstrated the high occurrence and abundance of CUPs in water,21−23 sediment,24−26 and biota.27,28 Only a limited number of publications report on the occurrence of CUPs in the air around the world; these studies include France,20,29 the Czech Republic,30 Italy,31 Canada,32−34 China,35,36 and the U.S.37−42 A significant knowledge gap still exists on the atmospheric distribution of CUPs, although their occurrence in remote locations certainly suggests that they can be atmospherically transported over long distances.43,44 While there have been many publications on the occurrence of organochlorine pesticides in the atmosphere of the Great Lakes,10,45,46 few studies have investigated the occurrence of CUPs in this region. In this study, we report the spatial and seasonal distributions of 15 CUPs in the atmospheric particulate in the Great Lakes basin. These CUPs include nine pyrethroid insecticides (bifenthrin, cyfluthrin, λ-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, and cis- and trans-permethrin); four herbicides (atrazine, metolachlor, pendimethrin, and trifluralin); one organophosphate insecticide (chlorpyrifos); and one fungicide (chlorothalonil). These particular CUPs were selected because of their large market share in the United States (see Supporting Information (SI) Table S1) and because they could be measured by gas chromatographic mass spectrometry (GCMS). The structures and classification of all of these compounds clustered by compound type and use are given in SI Figure S1 and their properties in SI Table S2. The concentrations of these compounds were measured in about 160 atmospheric particulate samples collected in 2015 at six sites around the North American Great Lakes as part of the Integrated Atmospheric Deposition Network (IADN). This is the first report on the occurrence of atmospheric CUPs in the particulate phase in the Great Lakes basin.
to determine if these chemicals were present in the samples and if the existing Standard Operating Procedures (SOPs) for extraction and analysis were suitable also for CUPs. An initial screening of both the vapor and the particulate phases showed that most targeted CUPs were relatively more abundant in the particulate phase (see SI Table S3). The exceptions were chlorpyrifos and trifluralin, which partition preferentially to the vapor phase. Given the scoping nature of this preliminary study, we focused on the particulate phase only because it allowed us to capture most of the target compounds. As a result, the total atmospheric concentration for these CUPs could be underestimated. Extraction. The filter samples were spiked with a known amount of surrogate recovery standards (BDE-77 and BDE166) and then Soxhlet extracted for 24 h with a hexane/acetone mixture (1:1, v:v). After rotary evaporation, the extracts were purified on a 3.5% water-deactivated silica column. The column was eluted with 25 mL of a hexane/dichloromethane mixture (1:1, v:v) and with 25 mL of a acetone/dichloromethane mixture (7:3, v:v). Atrazine and metolachlor eluted in the second fraction and other CUPs eluted in the first fraction. The two fractions were rotary evaporated, blown down to 1 mL with N2, spiked with known amounts of the internal standards (BDE-181 and d10-anthracene), and further blown down to about 100 μL with N2. Instrumental Analysis. The CUPs listed here, except atrazine and metolachlor, were quantitated on an Agilent 7890 gas chromatograph coupled to an Agilent 5975 mass spectrometer operated in the electron capture negative ionization (ECNI) mode fitted with an Rtx-1614 column (15 m long, 250 μm i.d., 0.1 μm film thickness). The GC injector was operated in the pulsed splitless mode (injection pulse 20 psi for 2 min) with the following inlet temperature program: 80 °C for 0.1 min, 500 °C/min to 280 °C, and held for a final 20 min. The GC oven temperature program was as follows: initial 80 °C for 2 min, 30 °C/min to 150 °C, 2 °C/min to 240 °C, 20 °C/min to 300 °C, and held for 5 min. The MS transfer line was held at 280 °C, and the ion source and quadrupole temperatures were both held at 150 °C. The ions monitored are given in SI Table S1. Atrazine and metolachlor were analyzed on an Agilent 6890 gas chromatograph coupled to an Agilent 5973 mass spectrometer operated in the electron impact (EI) mode. Separation was achieved with an Agilent DB-5MS Ultra Inert capillary column (30 m long, 250 μm i.d., 0.25 μm film thickness). The GC oven temperature started at 100 °C, increased to 200 °C at 8 °C/min, then increased to 212 °C at 3 °C/min, and finally increased to 280 °C at 8 °C/min. The temperatures of the ion source and the quadrupole were set at 280 and 150 °C, respectively. The ions monitored are given in SI Table S1, and presumed structures of the ions monitored are given in SI Figure S2. Quality Assurance and Quality Control. Either a procedural blank or a matrix spike recovery sample was run with every batch of 8−10 samples. The surrogate recoveries of lab blanks and matrix spike were 90% ± 5 and 108% ± 7 for BDE-77, and 82% ± 6 and 90% ± 3 for BDE-166. Since these samples were not originally intended for CUPs analyses, CUPsspecific surrogate and internal standards had not been spiked into them. Hence, because most CUPs eluted in the same fraction as polybrominated diphenyl ethers (PBDEs), PBDEs standards (both surrogate and internal) were used to quantitate CUPs. A comparison of surrogate recoveries for PBDEs and
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METHOD AND MATERIALS Air Sampling. Six IADN sites, including two urban sites (Chicago, IL, and Cleveland, OH), two remote sites (Eagle Harbor, MI, and Sleeping Bear Dunes, MI), and two rural sites (Sturgeon Point, NY, and Point Petre, Ontario) were selected as the sampling sites. Particulate air samples were collected with a high-volume air sampler (General Metal Works, model GS2310) for 24 h every 12 days from 1 January to 31 December 2015 at five IADN sites. At Point Petre, samples were collected every 36 days. The high volume air sampler used a 0.3 μm quartz fiber filter (Whatman QM-A, 20.3 × 25.4 cm) for collection of the particulate phase followed by a cartridge filled with XAD-2 resin to collect the vapor phase. All the samples were kept at −20 °C until analysis. Both particulate and vapor phase samples were collected and analyzed for legacy pollutants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbon (PAHs), and organochlorine pesticides (OCPs) as part of IADN, which is a long-term project funded by the U.S. EPA’s Great Lakes National Program Office. In 2017, we screened IADN extracts for CUPs B
DOI: 10.1021/acs.est.8b00123 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
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of 98.6 pg/m3 at Chicago to a low of 4.23 pg/m3 at Eagle Harbor. The atmospheric concentrations of ∑CUPs were significantly higher at the two urban sites (Chicago and Cleveland) than at the most remote site (Eagle Harbor). ∑CUPs concentrations at Sturgeon Point, Point Petre, and Sleeping Bear Dunes were statistically indistinguishable from one another (Figure 1). Since the major uses of these CUPs are in agriculture and some of the sampling sites are located in rural areas, we expected relatively high levels of these compounds at these rural and remote sites compared to the urban sites. Instead, we see just the opposite. Total CUPs concentrations at the remote sites of Eagle Harbor and Sleeping Bear Dunes are comparable with those observed at a background site in the European Monitoring and Evaluation Programme network (EMEP), where the concentrations ranged from a high of 323 pg/m3 (for 27 CUPs) to a low of not detected (ND).30 The atmospheric concentrations of seven CUPs in the particulate phase in the Houston metropolitan area ranged from nearly 1100 pg/m3,37 to ND; these values are comparable with our data at urban sites. Among the individual CUPs classes, the pyrethroid insecticides constituted about 50% of ∑CUPs concentration at Chicago and Cleveland, about 25% at Point Petre and Sturgeon Point, and about 35−40% at Sleeping Bear Dunes and Eagle Harbor (see Table 2 and SI Figure S3). The herbicides and the organophosphate insecticide, chlorpyrifos, made up about 30% of ∑CUPs concentrations at all sites except at Sleeping Bear Dunes, where this fraction was only about 10%. The fungicide, chlorothalonil, made up about 30% of the ∑CUPs concentrations at Chicago, Cleveland, and Eagle Harbor, about 40% at Point Petre and Sturgeon Point, and about 55% at Sleeping Bear Dunes. These differences in the spatial distributions of CUPs can be attributed to differences in use patterns for the individual pesticides and to different land use patterns around each of the six sites (Table 1). Pyrethroid Insecticides. The highest concentrations of total pyrethroid insecticides were measured at Chicago (median of 27.8 pg/m3), and the lowest such concentrations were at Eagle Harbor (median of 1.71 pg/m3). The total pyrethroid insecticides concentrations at Cleveland were statistically indistinguishable from those at Point Petre, Sturgeon Point, and Sleeping Bear Dunes, but significantly higher concentrations of these compounds were observed at Chicago compared to the four rural and remote sites (Table 2). A one-way ANOVA showed that the levels of bifenthrin, cyfluthrin, and cypermethrin at Chicago and Cleveland were significantly higher than those at Eagle Harbor (Table 2). In a previous study, bifenthrin concentrations were found in the range of 8.6−240 pg/m3 in particulate-phase atmospheric samples collected in Houston, Texas.37 These levels are higher than our measured bifenthrin concentrations at Chicago (1.0− 90 pg/m 3 ) and at Cleveland (0.39−74 pg/m 3 ). The concentration of λ-cyhalothrin in the particulate phase was in the range of 1.1 to 57 pg/m3 in Houston,37 values which are consistent with our findings at the two IADN urban sites, where the concentrations ranged from 0.11 to 51 pg/m3. In general, the median levels of most of the pyrethroid insecticides were significantly higher at Chicago and Cleveland compared to the rural and remote sites, and the levels at the latter sites were generally not distinguishable from one another. Permethrin is a common pesticide used for controlling mosquitos in the U.S.49 It is normally applied as a mixture of the cis and trans isomers, with the cis to trans-ratio being 0.3,
OCPs confirmed a positive and significant relationship. A detailed analysis of the performance of the surrogate standards and correlations among these recoveries is provided in the Supporting Information (see SI Table S4). The concentrations reported here were not corrected for surrogate recoveries. Matrix spike recoveries were within the 50−130% EPA acceptable range (see SI Table S4).47 Field blanks were collected throughout the year at each site (n = 24; see SI Table S5). Field blank levels were averaged over the entire sampling period. Sample levels below the average site-specific field blank levels on a mass basis were treated as nondetects, and the corresponding data cells were left empty. Land Use Analysis. The landscape use analysis was done using data from USDA CropScape-Cropland Data Layer48 in ESRI ArcMap 10.4.1. To identify the predominant land uses at our sampling sites, we first calculated the land cover within a 25 km radius for each site. We then grouped the 95 land cover types into three groups: agriculture, nonagriculture and developed. The group labeled Agriculture included 82 types (such as soybeans, winter wheat, and alfalfa). The Nonagriculture group comprised nine types including deciduous forest, woody wetlands, and open water. The group labeled Developed included four types including developed/high intensity and developed/open space. The percentages of land cover use around each site are provided in Table 1. Table 1. Percentages of Land Use Categories around Five Sampling Sites within a 25 km Radiusa Chicago Cleveland Sturgeon Point Sleeping Bear Dunes Eagle Harbor
agriculture
nonagriculture
developed
0.4 1.5 27 14 0.1
6.6 21 55 79 97
93 78 18 7.1 3.3
a
Land cover data was obtained from USDA CropScapeCropland Data Layer, 2015. No data were available for Point Petre, since the CropScape database covers only the United States and not Canada.
Data Analysis. Basic and descriptive statistics were calculated using Minitab 18, and Microsoft Excel 2013. Plots were generated using SigmaPlot 13 (Systat Software Inc.).
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RESULTS AND DISCUSSIONS Concentrations. Table 2 gives the median concentrations (in pg/m3) for each of the 15 individual CUPs targeted in this study, total pyrethroid insecticides and herbicides, and total CUPs (concentrations of 15 CUPs added together, ∑CUPs). In this case, it is important to remember that the median of the sum is not the sum of the medians. These data are given for each of the six sampling sites. Table 2 also gives the detection frequency (df, %) for each of the CUPs measured at the six IADN sampling sites and the results of the analysis of variance (ANOVA) comparing the logarithmically transformed concentrations among the sites. SI Table S6 gives the concentrations ranges for each compound at each site. Figure 1 shows boxplots for the particulate phase concentrations of ∑CUPs at each site. The five most frequently detected CUPs in these samples were the fungicide chlorothalonil, the pyrethroids cypermethrin and λ-cyhalothrin, and the herbicides trifluralin and pendimethalin, with average detection frequencies of more than 60%. Overall, the median ∑CUPs concentrations ranged from a high C
DOI: 10.1021/acs.est.8b00123 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
D
61
94
12.3 98.6
30 48 94 91
72.9 72.8 2.26 1.15 14.6
0.36
64 79 85 79 21 67 12 55 64
df
9.24 7.88 2.74 5.17 3.72 0.41 0.12 8.24 6.94 27.8
Med
A A
A
A A A A A
A A A AB A A A A A A
*
17
0.7
8.1 17 3.7 2.7 31
14 11 2.7 9.1 1.8 0.3 0.7 5.3 5.6 51
%
11.8 85.1
0.39
157 7.51 2.52 0.89 5.53
4.83 13.1 1.05 9.04 1.46 0.41 0.04 11.4 2.35 23.4
Med
92
65
15 15 88 85
65 65 65 65 27 73 19 31 31
df
AB AB
A
A ABC A A AB
A A A A A A A A A AB
*
Cleveland (N = 26)
23
1.0
8.9 3.3 8.4 6.8 27
13 14 2.0 9.4 3.9 0.6 1.5 2.9 2.2 49
%
3.17 18.5
100
75
75 88
1.85 0.06 2.43 0.29
25
38 38
2.95 2.76 3.72 3.35
63 50 75 63 25 100
df
0.34 0.80 0.60 0.45 2.35 0.03
Med
AB BC
AB
A BC ABC
B
A A BC
B B A BC A B
*
Point Petre (N = 8)
44
2.3
23 1.0 29
4.5
3.8 3.6 25
2.2 1.4 3.5 0.9 9.6 0.3
%
5.27 13.7
0.39
41.7 1.56 0.37 6.03
0.41 10.5 0.20 0.36 0.92 0.03 0.47 4.90 12.3 2.77
Med
96
44
41 67 44
52 30 44 63 26 37 7 22 30
df
AB B
A
AB A A AB
B AB A C A AB A A A BC
*
40
1.2
22 7.8 3.6 34
5.2 3.5 0.7 3.2 6.5 0.1 0.01 2.7 3.4 25
%
Sturgeon Point (N = 27)
33.7 25.4
0.30
0.37 1.83 0.27 1.72
1.12 1.15 1.02 0.45 2.68 0.24 0.02 1.14 1.59 3.01
Med
76
41
9 35 12
44 41 53 44 21 35 26 24 21
df
A B
A
C A AB BC
B AB A C A A A A A BC
* %
56
3.6
0.8 4.2 0.1 5.1
12 2.7 2.2 1.4 13 0.2 0.5 2.0 1.0 35
Sleeping Bear Dunes (N = 34)
1.05 4.23
0.04
1.33 7.12 1.60 0.02 2.02
0.43 0.46 0.43 0.32 1.17 0.09 0.10 1.41 1.55 1.71
Med
76
32
18 35 21 65
32 50 38 44 18 26 6 26 29
df
B C
B
AB BC A C C
B B A C A AB A A A C
*
29
0.3
5.0 18 5.1 1.1 29
6.5 9.0 2.4 3.7 10 0.1 0.1 4.4 4.6 41
%
Eagle Harbor (N = 34)
a ANOVA results using logarithmically transformed concentrations are also shown in the columns headed by asterisks; concentrations sharing the same letter are not significantly different at a P < 0.05 level. The average contribution of individual CUPs relative to ∑CUPs (%) are given. N is the number of samples at a given site.
Pyrethroid Insecticides bifenthrin cyfluthrin λ-cyhalothrin cypermethrin deltamethrin esfenvalerate fenpropathrin permethrin, cispermethrin, transTotal pyrethroid insecticides Herbicides atrazine metolachlor pendimethalin trifluralin Total herbicides Organophosphate Insecticide chlorpyrifos Fungicide chlorothalonil Total CUPs
Chicago (N = 33)
Table 2. Median Atmospheric Particulate Phase Concentrations (med, pg/m3) and Detection Frequency (df, %) of the Analyzed CUPs at the Six IADN Sampling Sitesa
Environmental Science & Technology Article
DOI: 10.1021/acs.est.8b00123 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
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at Sleeping Bear Dunes (median of 0.37 pg/m3). These concentrations are comparable with those observed in air near the city of Pace, Mississippi, in 2007 (41 pg/m3),38 but our values are much lower than those reported from the Iowa Air Monitoring Station in Iowa City, Iowa, in 2000−2002 (2300 pg/m3)33 and from St. Damase, Canada, in 2004 (3030−19 100 pg/m3).32 The concentration of atrazine, one of the most widely used herbicides worldwide, varied greatly between the urban and the rural/remote sites. The median concentrations of atrazine in Chicago and Cleveland were 72.9 and 157 pg/m3, respectively, which were much higher than the previously reported concentrations of 19 pg/m3 in the atmospheric particulatephase in Hinds county, Mississippi.56 However, atrazine was not detected at the rural site of Sturgeon Point nor at the remote site of Sleeping Bear Dunes. Atrazine concentrations at Point Petre and Eagle Harbor were 1 order of magnitude lower than those observed at Chicago and Cleveland. Although atrazine and metolachlor are among the most intensively applied CUPs in agriculture in the U.S., their detection frequencies were only around 25% in our samples. This finding may be related to the physicochemical properties of these chemicals, which have relatively high-water solubility and low persistence in air.57 The median concentrations of trifluralin at the urban and rural sites (Chicago, Cleveland, and Sturgeon Point) were generally higher than those at the remote sites. The atmospheric concentrations of trifluralin could be underestimated here because this compound tends to partition to the vapor phase, and in this study, we measured only the particulate phase. The concentrations of pendimethalin among the six sampling sites were statistically indistinguishable. Organophosphate Insecticide. No significant differences were found among the concentrations of the organophosphate insecticide chlorpyrifos measured at the different sites, except for Eagle Harbor. Generally, our measured concentrations are much lower than those observed in an agricultural region of central Washington State in 2011, where chlorpyrifos concentrations ranged from 9.2 to 200 ng/m3.42 Higher chlorpyrifos concentrations (3.2−2700 pg/m3) were also found in an agricultural area in Ontario, Canada.34 The atmospheric chlorpyrifos concentration could be significantly underestimated in this study because we analyzed the particulate phase only, and this compound tends to partition to the vapor phase. Additionally, it has been previously reported that chlorpyrifos, once in the air, can degrade within a matter of hours by reacting with photochemically produced hydroxyl radicals.58 The combination of these two factors (partitioning to the vapor and rapid photochemical degradation) may explain why we detected chlorpyrifos at such low concentrations compared to the other CUPs in this study, despite it being one of the most widely used insecticides. Fungicide. The concentrations of the fungicide chlorothalonil were not significantly different among the sampling sites. The lowest chlorothalonil median concentration was 1.05 pg/ m3 observed at Eagle Harbor. Interestingly, the highest chlorothalonil concentration (33.7 pg/m3) was measured at Sleeping Bear Dunes, our remote site. The atmospheric concentrations of chlorothalonil in the Great Lakes basin in 1999 ranged from 20 to 100 pg/m3,10 which is comparable with our measurements, despite a 20 years gap between the sampling campaigns. Chlorothalonil showed the highest detection frequency among all targeted CUPs (75−100%, see Table 2).
Figure 1. ∑CUPs concentrations in the particulate phase at the six IADN sampling sites. The boxes represent the 25th and 75th percentiles, the whiskers represent the 10th and 90th percentiles, and the black horizontal solid line inside each box represents the median. The letters represent the ANOVA results of the comparison of the logarithmically transformed concentrations among the six sites; concentrations at sites sharing the same letter are not statistically different at P < 0.05. The number of samples at a given site are given in parentheses along with the site name, which is abbreviated as follows: CH, Chicago; CL, Cleveland; PP, Point Petre; SP, Sturgeon Point; SBD, Sleeping Bear Dunes; and EH, Eagle Harbor.
0.7, or 4, depending on the particular commercial mixture.50 Cis-permethrin has been shown to be more resistant to environmental degradation than trans-permethrin.51 Interestingly, our ANOVA results show that the concentrations of cisand or trans-permethrin are statistically indistinguishable among the six sampling sites (all 12 ANOVA categories are A). The average ratio of cis- to trans-permethrin concentrations at all sites ranged from 0.94 at Eagle Harbor to 2.5 at Chicago, but these ratios were statistically indistinguishable from one another. These values are consistent with a cis- to transpermethrin ratio of 1.2 ± 0.5 in dust samples collected from carpeted flooring;52 however, because the ratio of the permethrin isomers in commercial products varies so much (from 0.3 to 4), it is not possible to attribute a shift in this ratio to use of specific product or degradation processes in the environment. Pyrethroid insecticides have replaced organophosphate pesticides, like diazinon and chlorpyrifos, for pest control in urban environments.53 Pyrethroid insecticides are now the predominant insecticide used both by household consumers and by professionals as termiticides and in landscape applications.54 There is little information in the literature on the occurrence of pyrethroid insecticides in the atmosphere of urban areas, but high levels of pyrethroid insecticides in urban water runoff suggest their widespread use in urban settings. For instance, bifenthrin was found at concentrations of up to 73 μg/L in runoff water in residential neighborhoods in Sacramento, California.53 In addition, in a laboratory study, runoff from concrete 24 h after pesticide treatment contained 82 μg/L of bifenthrin, 5100 μg/L of cis-permethrin, and 5500 μg/L of trans-permethrin.55 Herbicides. The median concentrations of total herbicides ranged from a high of 14.6 pg/m3 at Chicago to a low of 1.72 pg/m3 at Sleeping Bear Dunes. In general, the total herbicide concentrations at all six sites were not distinguishable from one another. Metolachlor was the predominant herbicide among the four targeted herbicides, with median concentrations of 72.8 pg/m3 at Chicago and 41.7 pg/m3 at Sturgeon Point. The lowest median concentration for this compound was measured E
DOI: 10.1021/acs.est.8b00123 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
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Environmental Science & Technology Indeed, chlorothalonil is one of the most frequently detected CUPs in the air globally. For example, its detection frequency reached 91% in southern Ontario, Canada,59 and 70% in Strasbourg, France.29 Chlorothalonil has a measured octanol-air coefficient (log Koa) of 8.11 (at 20 °C), and its half-life in air is about 1 week,60 implying that it has the potential for long-range atmospheric transport. As expected, chlorothalonil has been detected in Arctic air, even though there are no direct sources there.43 Spatial Distribution and Land Use Analysis. For many man-made chemicals, their environmental concentrations are directly related to the population density around the sampling sites, with the lowest concentrations to be expected at remote sites and the highest at urban sites. For example, the concentrations of PBDEs,61 PCBs,62 polychlorinated dibenzop-dioxins and dibenzofurans,63 and bromobenzenes64 have all been reported to be highly and positively correlated with the local human population. However, CUPs are thought to be mainly used in agriculture with only minor uses in urban areas for landscaping or pest control in homes. Therefore, the population effect was not expected to be particularly strong for CUPs. To evaluate this hypothesis, we calculated the population within a 25 km radius for each sampling site using a method published elsewhere.65 We functionalized the relationship of CUPs concentrations to population using the following equation:
Table 3. Results of the Regressions of the Logarithmically Transformed Mean Concentrations vs. Local Population for the Selected CUPs; See eq 1a Pyrethroid Insecticides bifenthrin cyfluthrin λ-cyhalothrin cypermethrin deltamethrin esfenvalerate fenpropathrin Permethrin, cisPermethrin, transTotal pyrethroid insecticides Herbicides atrazine metolachlor pendimethalin trifluralin Total herbicides Organophosphate Insecticide chlorpyrifos Fungicide chlorothalonil Total CUPs
N
a0
a1
P
83 86 94 95 36 80 22 52 57 141
−0.752 −0.720 −0.567 −1.11 0.038 −1.34 −0.915 −0.275 −0.165 −0.243
0.036 0.040 0.018 0.043 0.006 0.019 −0.005 0.027 0.022 0.036
0.020* 0.047* 0.024* 0.012* 0.618 0.286 0.817 0.011* 0.003* 0.002*
22 46 97 97 125
−1.94 0.242 0.226 −1.89 −0.411
0.087 0.028 0.004 0.052 0.038
0.246 0.352 0.408 0.006* 0.008*
80
−0.992
0.019
0.121
141 158
0.387 0.414
0.015 0.037
0.309 0.001*
(1)
a The probabilities (P) of the significance of all regressions are given; probabilities marked with an asterisk are significant at P < 0.05.
where a0is the intercept and a1 (unitless) describes the change of the concentration as a function of population (a surrogate for human activities). The results of these regressions are given in Table 3. Surprisingly, these regressions were statistically significant for total pyrethroid insecticides (P < 0.05) and for most individual pyrethroids, except for deltamethrin, esfenvalerate, and fenpropathrin. These findings corresponded well with a previous study where the log-transformed total pyrethroid concentrations in stream sediment were significantly correlated to the percentage of urban land use near the sampling site.66 Unlike the pyrethroid insecticides, no significant relationships with population were observed for any individual herbicide, except trifluralin. The relationship of concentration vs population was not significant for the organophosphate insecticide chlorpyrifos (P = 0.121) or for the fungicide chlorothalonil (P = 0.309). In addition to local population, another variable useful in understanding the spatial distribution of CUPs is land use. Not surprisingly, land use analysis showed that the sites near Chicago and Cleveland were mostly surrounded by developed land (developed land use was 93% for Chicago and 78% for Cleveland, see Table 1). The area around Cleveland included also 21% of land that was not developed or cultivated, but which was dedicated to forest, shrubland, wetland, or pasture. The 25 km radius area around the two remote sites of Eagle Harbor and Sleeping Bear Dunes was mostly characterized by nonagricultural land cover, although Sleeping Bear Dunes also had 15% of land dedicated to agricultural activities. Fifty-five percent of the area around Sturgeon Point was used for nonagricultural purposes, 27% for agricultural uses, and 18% was developed land. Sturgeon Point had the highest fraction of land dedicated to agriculture among the five IADN sites. A correlation between the logarithmically transformed average concentrations of CUPs and the three land use
categories (see the SI Table S8 for more details) showed that pyrethroids were significantly correlated with both nonagricultural and developed land uses (p < 0.05;) and herbicides were significantly correlated with nonagricultural uses (p < 0.05). In urban settings, pyrethroids are used for golf courses turf, ornamental plants, residential lawns, and rights of way. Herbicides, and in particular trifluralin, are used as preemergent herbicides, and they have significant uses in nonagriculture crops, such as grasses and broadleaf.67 Chlorpyrifos concentrations were not correlated with any of these parameters, which might be related to the underestimation of these concentrations as discussed above. Interestingly, chlorothalonil was not significantly correlated with any of the three land use categories, but an analysis of the correlation plot showed that the high concentration of this compound at Sleeping Bear Dunes played a major role in the results. Once this site was removed from the analysis, the correlation with nonagriculture land use became highly significant. The concentration of chlorothalonil was unusually high at Sleeping Bear Dunes, considering that it is a remote site. Because chlorothalonil is heavily used in golf courses and for lawn care, we speculate that the high levels we measured in the air at this site might be related to the elevated number of golf courses in the vicinity of the sampling site. Overall, the population and land use analysis showed that, in addition to agricultural application, these pesticides have various significant uses in nonagricultural and urban settings, and as a result, they have become ubiquitous. However, it should be noted that these sampling sites, even the remote ones, were not representative of agricultural areas, which may affect our capacity to attribute measured concentrations to different uses.
ln(C) = a0 + a1 log 2(pop)
F
DOI: 10.1021/acs.est.8b00123 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
Table 4. Median CUPs Concentrations (pg/m3) in the particulate Phase at the Six IADN Sampling Sites for the Warmer Months (April to September) and for the Colder Months (October to March)a urban sites Pyrethroid Insecticides bifenthrin cyfluthrin λ-cyhalothrin cypermethrin deltamethrin esfenvalerate fenpropathrin permethrin, cispermethrin, transTotal pyrethroid insecticides Herbicides atrazine metolachlor pendimethalin trifluralin Total herbicides Organophosphate Insecticide chlorpyrifos Fungicide chlorothalonil
rural/remote sites
warmer months
colder months
prob.
warmer months
colder months
prob.
32.5 17.1 2.69 6.14 3.20 0.42 4.35 20.0 16.6 33.2
2.83 7.95 1.88 7.34 2.08 0.41 0.01 2.51 3.15 24.3
