1. bookVolume 72 (2021): Issue 4 (December 2021)
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1848-6312
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26 Mar 2007
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Open Access

Seasonal distribution of multiclass pesticide residues in the surface waters of northwest Croatia

Published Online: 30 Dec 2021
Volume & Issue: Volume 72 (2021) - Issue 4 (December 2021)
Page range: 280 - 288
Received: 01 Oct 2021
Accepted: 01 Nov 2021
Journal Details
License
Format
Journal
eISSN
1848-6312
First Published
26 Mar 2007
Publication timeframe
4 times per year
Languages
English

According to European Directive 2013/39/EU (1), nearly a half of the 45 compounds classified as priority water pollutants are legacy or currently used pesticides. In the environment, especially in watercourses flowing through agricultural areas, these pesticides are present in complex mixtures (2, 3), whose toxic effects are still insufficiently explored (4, 5). Some, such as atrazine, acetochlor, trifluraline, and chlorfenvinphos, have gradually been phased out and eventually banned in many European countries, but their residues and degradation products in water resources have remained a serious issue in different parts of the world (612). New pesticide classes that have replaced them have also been contributing to water pollution (7, 8).

The aim of this study was to evaluate and compare the burden of selected legacy and current-use pesticides on river/stream waters in urban and rural areas of northwest Croatia as part of the OPENTOX project (2014–2018) investigating pesticide pollution and impact on the environment and human health in a densely populated area of the most developed northwest part of Croatia. Furthermore, we wanted to compare our findings with earlier reports from this area to get a better insight into any trend that may have taken place over the years (9, 13).

MATERIALS AND METHODS

River/stream water samples were collected in 2015 with a telescopic pole for grab sampling from the bank at a depth of about 0.5 m as described earlier (9). Figure 1 shows the sampling locations: two at the Sava River a few kilometres upstream and downstream of the Zagreb city centre, two at the mouths of its tributaries Krapina (in Jablanovec) and Sutla (in Harmica), one at the Drava River in the city of Varaždin, two at its tributaries Bednja (in Stažnjevec) and Plitvica (in Greda), and one at the Bednja tributary stream Bistrica (in Ivanec). Of the two major rivers, the Sava springs in Slovenia and flows through rural and urban areas for about 200 km before it reaches the Croatian capital Zagreb, and the Drava springs in Italy to flow through rural and urban regions in Italy, Austria, and Slovenia for about 420 km before it reaches Varaždin. The minor rivers Krapina, Sutla, Bednja, Plitvica, and the Bistrica stream flow through semirural/semiurban areas of northwest Croatia dominated by corn fields, orchards, and vineyards.

Figure 1

Sampling locations of river/stream waters in northwest Croatia (https://www.google.com/maps/@45.6943072,16.0121326,9z)

Sampling was organised around seasonal pesticide application to coincide with its beginning (March), mid-season (June), and end (August). The only exception was the Sava 2 location, where we did not collect the August sample.

The samples were stored in 2.5-L tinted glass bottles at 4 °C until analysis. Water pH ranged from 6.7 to 7.3. Samples were analysed for 23 pesticides (16 herbicides and seven insecticides) (Table 1), eight of which are listed as priority pollutants (1): alachlor, atrazine, chlorfenvinphos, chlorpyrifos-ethyl, diuron, isoproturon, trifluralin, and cypermethrin. Some of the remaining 15 compounds are allowed for use and are common environmental contaminants in Croatia.

Pesticides and pesticide degradation products analysed in this study

Class/PesticideChemical nameSa (mg/L)log KowapKaa
Dinitroaniline herbicide
Trifluralin2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)aniline0.2215.27ND
s-Triazines and metabolites
Atrazine6-chloro-N2-ethyl-N4-(1-isopropyl)-1,3,5-triazine-2,4-diamine352.71.7
Deethylatrazine (DEA)6-chloro-N4-isopropyl-1,3,5-triazine-2,4-diamine27001.511.3b
Deisopropylatrazine (DIA)6-chloro-N2-ethyl-1,3,5-triazine-2,4-diamine9801.151.2b
Terbuthylazine6-chloro-N2-tert-buthyl-N4-ethyl-1,3,5-triazine-2,4-diamine6.63.41.9
Deethylterbuthylazine (DET)6-chloro-N2- tert-buthyl -1,3,5-triazine-2,4-diamine327.12.31.35c
Phenylurea herbicides
Diuron3-(3,4-dichlorophenyl)-1,1-dimethylurea35.62.87ND
Linuron3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea63.83.0ND
Chlortoluron3-(3-chloro-4-methylphenyl)-1,1-dimethylurea762.5ND
Isoproturon3-(4-isopropylphenyl)-1,1-dimethylurea70.22.5ND
Chloroacetanilide herbicides
Acetochlor2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetamide2824.14ND
Alachlor2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide2403.090.62
Metolachlor(RS)-2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(1-methoxypropan-2-yl)acetamide5303.4ND
Triketone herbicides and metabolite AMBA
Mesotrione2-[4-(methylsulfonyl)-2-nitrobenzoyl]cyclohexane-1,3-dione15000.113.12
2-Amino-4-(methylsulfonyl) benzoic acid (AMBA)2-amino-4-(methylsulfonyl)benzoic acidNA0.38d4.24d
Tembotrione2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoroethoxymethyl) benzoyl]cyclohexane-1,3-dione71000-1.093.18
Organophosphorous insecticides and oxo- metabolite
Chlorpyrifos-methylO,O-dimethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate2.744.00ND
Chlorpyrifos-ethylO,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate1.054.7ND
Chlorpyrifos-methyl-oxonDimethyl (3,5,6-trichloropyridin-2-yl) phosphateNA1.91eNA
MalathionDiethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate1482.75ND
Chlorfenvinphos[(EZ)-2-chloro-1-(2,4-dichlorophenyl)ethenyl] diethyl phosphate1453.8ND
Pyrethroid insecticide
α-CypermethrinRacemate comprising (R) and (S) α-cyano-3-phenoxybenzyl- (1R,3R)-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropane- carboxylate0.0045.8ND
Neonicotinoid insecticide
ImidaclopridN-{1-[(6-chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl}nitramide6100.57ND

Kown-octanol-water partition coefficient; pKa – dissociation constant; NA – not available; ND – no dissociation; S – solubility in water (14);

(8),

(15),

(16),

(17)

Chemicals

Atrazine, deethylatrazine (DEA), deisopropylatrazine (DIA), terbuthylazine, deethylterbuthylazine (DET), linuron, diuron, isoproturon, alachlor, trifluralin, chlorpyrifos-ethyl, and chlorfenvinphos were purchased from Riedel de Haën (Seelze, Germany), chlortoluron, mesotrione, tembotrione, 2-amino-4-(methylsulfonyl) benzoic acid (AMBA), and malathion from Sigma Aldrich (Steinheim, Germany), acetochlor from Nitrokémia Environmental Protection Consulting and Ministering Incorporated Company (Fűzfőgyártelep, Hungary), metolachlor from Fluka A.G. (Buchs, Switzerland), and α-cypermethrin, chlorpyrifos-methyl, chlorpyrifos-methyl-oxon, and imidacloprid from Dr. Ehrenstorfer (Augsburg, Germany). All these pesticide standards were of 95–100 % purity.

Methanol, acetonitrile, and ethyl acetate for HPLC, LiChrosolv®, Suprasolv®, and acetone for organic trace analysis were purchased from Merck (Darmstadt, Germany), and orthophosphoric acid (85 %, analytical grade) from Kemika (Zagreb, Croatia). LC-grade water was prepared by purifying deionised water with a Milli-Q water purification system (Millipore, Bedford, MA, USA).

Methods

Table 2 details five methods used in this study to meet diverse analytical requirements for each compound. For each method we used appropriate single-use solid-phase extraction (SPE) cartridges: 200 mg OASIS HLB (Method 1) and 360 mg Sep-Pak C18 (Methods 2 and 4) were obtained from Water Associates (Milford, MA, USA) and 200 mg Bakerbond speTM SDB-1 (Method 3) and 100 mg C18 Polar plus/SDB-1 (Method 5) from JT Baker (Deventer, the Netherlands). The extracts were analysed using high-performance liquid chromatography with UV diode array detection [HPLC-UV(DAD)] and/or by gas chromatography – mass spectrometry using ion trap detection [GC-MS(ITD)].

Methods for determination of pesticides and their degradation products in natural waters by SPE and HPLC-UV(DAD) or GC-MS(ITD) analysis

Method of analysisHPLC-UV(DAD)GC-MS(ITD)
Method 1λ (nm)Method 2λ (nm)Method 3aλ (nm)Method 4a m/zMethod 5m/z
PesticideMesotrione – 220Terbuthylazine – 222Atrazine – 222Trifluralin – 264Terbuthylazine – 214
AMBA – 220DET – 214DEA – 214Atrazine – 200Chlorpyrifosmethyl – 286
Tembotrione – 205Malathion – 205DIA – 214Terbuthylazine – 214Chlorpyrifosethyl – 314
Chlorfenvinphos – 205Terbuthylazine – 222Acetochlor – 223Malathion – 173
Chlorpyrifos-methyloxon – 205DET – 214Alachlor – 188Chlorfenvinphos – 267
Imidacloprid – 270Diuron – 210, 245Metolachlor – 162α-Cypermethrin – 163
Linuron – 210, 245
Chlortoluron – 210, 245
Isoproturon – 202, 245
SPEOASIS HLBC18SDB-1C18C18 Polar plus/ SDB-1
ActivationMeOH+H2OACN+H2OMeOH+H2OMeOH+H2OMeOH+H2O
Solvent volume (mL)2+25+52+52+52+5
Sample volume (mL)5005005001000500
EluentMeOHACN+Et.acAcEt.acEt.ac
Eluent volume (mL)1010+52210

Ac-acetone; ACN – acetonitrile; Et.ac – ethyl acetate; MeOH – methanol; m/z – significant MS fragment ion selected for quantitation; a as described in (9)

Water extracts were evaporated to dryness under a gentle stream of nitrogen. For HPLC-UV(DAD) analysis, the dry residue was redissolved in 0.5 mL or 1.0 mL of deionised water or in a mixture of acetonitrile and deionised water (pH 3) in the 1:9 ratio. For GC-MS(ITD) analysis, the dry residue was redissolved in 0.5 mL or 1.0 mL ethyl acetate. Prior to HPLC-UV(DAD) or GC-MS(ITD) analysis, the extracts were filtered through 0.2 μm pore size syringe filters.

HPLC-UV(DAD) analysis was performed on a Varian liquid chromatograph equipped with a Varian ProStar 230 SDM pump, Varian ProStar 410 autosampler employing a 100-μL sample loop, and a Varian ProStar 330 photodiode-array detector (Varian, Walnut Creek, CA, USA). The chromatographic column was Gemini C18, 250x4.6 mm i.d., of 5-μm particle size with a 4.0x3.0 mm i.d. guard column of 5-μm particle size (Phenomenex, Torrence, CA, USA). The mobile phase for the analysis of triketone herbicides and their metabolites (Method 1) as well as for the analysis of terbuthylazine, DET, malathion, chlorfenvinphos, imidacloprid, and chlorpyrifos-methyl-oxon (Method 2) consisted of acetonitrile and deionised water acidified with H3PO4 to pH 2.2. The compounds were eluted using linear gradient elution mode from 10 % to 80 % acetonitrile over 17 min (Method 1) and from 20 % to 75 % acetonitrile over 27 min (Method 2). The mobile phase solvents for the analysis of a mixture of s-triazines and their metabolites and phenylurea herbicides were acetonitrile and deionised water (Method 3). Herbicides were eluted with a linear gradient from 30 % to 40 % acetonitrile over 22 min and then from 40 % to 90 % acetonitrile over 8 min as described elsewhere (9). The mobile phase flow-rate for all methods was 1 mL/min. The sample volume injected was 100 μL. The UV-spectra of all analytes were recorded at 200 nm to 400 nm (Table 2).

GC-MS(ITD) analysis was performed on a Varian Saturn 2200 GC/MS/MS system consisting of a CP-3800 gas chromatograph with 1079 on-column injector, CP-8410 autoinjector, and ion trap detector. The GC column was an HP-5MS fused silica column, 30 m x 0.25 mm i.d., film thickness 0.25 μm (Agilent Technologies, Santa Clara, CA, USA). Pesticide compounds were separated and detected under GC-MS(ITD) operating conditions described earlier (9). Their mass spectra were recorded in the full scan acquisition mode (mass range 50–550 m/z) and scan rate of three scans per second. Table 2 lists the most intensive fragment ions (m/z) selected for the quantitation of specific analytes (Methods 4 and 5).

Standard solutions for HPLC-UV(DAD) analysis were prepared in deionised water and for GC-MS(ITD) analysis in ethyl acetate. Mass concentrations of single pesticides in final HPLC standards ranged from 19 to 536 ng/mL and in standards for GC analysis from 13 ng/mL to 929 ng/mL.

For recovery experiments, river water samples were spiked with pesticide standards in aqueous or acetone solutions. Mass concentrations in spiked water samples ranged from 19 to 1429 ng/L for HPLC-UV(DAD) and from 3 to 1034 ng/L for GC-MS(ITD). The precision of the methods was determined by calculating the relative standard deviations (RSD) of recoveries obtained by repeated analysis of spiked water samples. In the investigated concentration ranges, pesticide recoveries were almost quantitative for most compounds and ranged from 90 to 107 %. The only exceptions were the slightly lower but still satisfactory recoveries of chlorfenvinphos (78 %) and imidacloprid (87 %) analysed by Method 2 and of atrazine (82 %), terbuthylazine (87 %), linuron (84 %), and isoproturon (88 %) analysed by Method 3. Low relative standard deviations of recoveries (<1–13 %) confirmed good precision of all methods.

Pesticides in river/stream water samples were quantified by external calibration with multipoint calibration lines generated daily for each compound by linear regression of its standard concentrations and the corresponding peak areas. Solvent and reagent blanks were prepared with each set of five water samples and analysed in the same manner as water extracts.

All analyses were run in duplicate. The target analytes were identified by comparing their chromatographic retention times and the corresponding UV or MS spectra with those of the known standards.

The limit of detection (LOD), defined as the average blank value plus three standard deviations (average + 3σ), was also used as the limit of quantitation (LOQ). The LOD of the GC-MS(ITD) method ranged from 5 to 30 ng/L, while the LOD of HPLC ranged from 10 to 15 ng/L.

RESULTS AND DISCUSSION

Of the 23 analysed pesticide pollutants, eight were not detected in any water samples, namely trifluralin, alachlor, malathion, chlortoluron, linuron, chlorpyrifos-ethyl, chlorfenvinphos, and α-cypermethrin. Negative findings for the first three pesticides are in line with their ban in Croatia since 2009, but the other five were still legal to use back in 2015 (18).

Among the 15 pesticide compounds detected in our river/stream water samples, 12 were herbicides and their degradation products and only three were insecticides. The number of positive water samples in all three sampling rounds and mass concentrations of detected pesticide residues are shown in Table 3. Six pesticide compounds were detected in more than half of the analysed samples: metolachlor in 91 %, DEA and terbuthylazine in 70 %, atrazine in 65 %, DIA in 57 %, and chlorpyrifos-methyl-oxon in 52 %.

Mass concentrations of pesticide pollutants in river/stream water samples collected in the northwest part of Croatia across application season

Pesticide compoundMarch 2015 (N=8)June 2015 (N=8)August 2015 (N=7)
γ (ng/L)γ (ng/L)γ (ng/L)
nRangeaMedianbnRangeaMedianbnRangeaMedianb
Mesotrione0 336–10700
Tembotrione0 751–216770
AMBA0 654–44474161<LOD
Terbuthylazine39–13<LOD820–41942510–2613
DET19<LOD438–20019214–45<LOD
Atrazine510–1611512–341359–2414
DIA55–326617–12328219–24<LOD
DEA48–11477–241156–3210
Isoproturon1146<LOD0 0
Diuron0 222–30<LOD0
Acetochlor0 128<LOD0
Metolachlor79–119811–3015147610–6311
Chlorpyrifos-methyl0 126<LOD0
Chlorpyrifos-methyl-oxon121<LOD823–14564334–198<LOD
Imidacloprid173<LOD812 – 34260

N – number of samples; n – number of positive samples; LOD – limit of detection; a Range applies to positive samples, b Median applies to all samples

Atrazine and acetochlor were also found, although their use has been banned in Croatia since 2009 and 2014, respectively. While the possibility of illegal leftover use cannot be completely ruled out, as may be the case with acetochlor found in only one sample in June (see Table 3), a more likely explanation for the relatively high incidence of atrazine and its degradation products DEA and DIA is their persistence in treated agricultural soils resulting in prolonged water pollution in agricultural catchments (8, 19, 20).

Most pesticides were identified in the height of the application season (14 in June as opposed to nine in March and eight in August) (Table 3).

Of the priority water pollutants, we found only atrazine, isoproturon, and diuron, and their peak mass concentrations were one to two orders of magnitude lower than the maximum allowable concentrations defined by the Directive as Environmental Quality Standards for surface waters (1). As there are no limits for pesticide compounds not considered priority pollutants, their mass concentrations in surface waters are often considered in terms of maximum permissible mass concentrations in water intended for human consumption of 100 ng/L for single pesticides and 500 ng/L for total pesticides (21). In this regard, Figure 2 shows that the 100 ng/L limit was mostly exceeded in the middle of the application season.

Figure 2

Mass concentrations of individual pesticides determined in river/stream water samples collected at the beginning (March), peak (June), and end (August) of the 2015 pesticide application season. AMBA – 2-amino-4-(methylsulfonyl)benzoic acid; DEA – deethylatrazine; DET – deethylterbuthylazine; DIA – deisopropylatrazine

Table 4 also clearly illustrates seasonal variations in pesticide load by sampling locations. The sum of mass concentrations of detected pesticides was the lowest at the beginning (March) and the highest in the peak of the pesticide application season (June). As expected, the lowest sums of pesticide mass concentrations were measured in the Drava River sampled in the urban area and the highest in the Krapina and Sutla rivers sampled in rural areas with intensive agricultural production. In the peak of the pesticide season, it exceeded the 500 ng/L limit for drinking water (21) in the samples taken from the Sutla, Krapina, Sava, and Bednja and the Bistrica stream. Metolachlor and terbuthylazine accounted for the largest shares in total mass concentrations in the Krapina and Sutla, metolachlor with 76 % and 74 % and terbuthylazine with 10 % and 12 %, respectively (see Figure 2, June). In the Sava, the highest shares were those of metolachlor and AMBA, ranging between the two sampling locations with 26–30 % and 20–24 %, respectively. The same pollutants were also dominant in the Bednja, where AMBA and metolachlor accounted for 51 % and 17 %, respectively. The high shares of AMBA point to recent application and subsequent degradation of a triketone herbicide mesotrione, which is less stable in soil and water than its degradation product (8, 22). As for the Bistrica stream, the highest shares in the sum of pesticide mass concentrations were those of tembotrione and mesotrione with 37 % and 15 %, respectively. All these findings point to the prevalence of herbicides metolachlor, terbuthylazine, tembotrione, and mesotrione in pesticide application in northwest Croatia.

Number (N) of individual pesticide compounds, their mass concentration range, and the sum of pesticides mass concentrations (Σ) by river/stream across application season

River/StreamMarch 2015June 2015August 2015
Nγ (ng/L)Nγ (ng/L)Nγ (ng/L)
MinMaxΣMinMaxΣMinMaxΣ
Sutla38224199256434553106399
Krapina7914621910223015399256198248
Sava 12973811110242947494577
Sava 2461135117149498– not analysed –
Drava251015622863232111425
Plitvica21016257161153314103276
Bistrica393252101121658251361147
Bednja571656101244486761166161

Bolded values exceed the EU Directive 2020/2184 limits for total pesticide concentrations in water intended for human consumption (21)

The prevalence of metolachlor and terbuthylazine and their degradation products has already been noted in our earlier study of the Sava samples taken the year before (9) and earlier studies across Europe (2, 2325).

As for insecticides analysed herein, all water samples collected in the height of the pesticide application season (June) contained trace concentrations of imidacloprid and chlorpyrifos-methyl-oxon (Table 3 and Figure 2). The finding of the latter points to a recent use of its parent compound chloropyrifos-methyl. Not only is it more persistent than the parent pesticide [over four weeks, according to Lacorte and Barceló (26)] but it is also more toxic to aquatic organisms and the environment (4) and should be regarded as pollutant of concern. As for the low imidacloprid concentrations, they are likely the consequence of restricted use in Croatia since 2013.

CONCLUSION

The limitation of our study is that our current data are limited to the measurements taken in 2015, while further data from the OPENTOX project (concluded with 2018) are still pending. Despite this limitation, the study has confirmed the persistence of atrazine in water environment and the domination of herbicide over insecticide use in urban and agricultural areas of northwest Croatia. Our findings further emphasise the need to extend regular monitoring of pesticides in surface waters to herbicide and insecticide compounds that are not considered priority water pollutants at the moment but are frequently used in larger amounts in regions with intensive agriculture. A systematic and regular monitoring of frequently used pesticides in surface waters can inform pesticide users and authorities and help to prevent or at least reduce their adverse effects on aquatic organisms and environment in a timely manner.

Figure 1

Sampling locations of river/stream waters in northwest Croatia (https://www.google.com/maps/@45.6943072,16.0121326,9z)
Sampling locations of river/stream waters in northwest Croatia (https://www.google.com/maps/@45.6943072,16.0121326,9z)

Figure 2

Mass concentrations of individual pesticides determined in river/stream water samples collected at the beginning (March), peak (June), and end (August) of the 2015 pesticide application season. AMBA – 2-amino-4-(methylsulfonyl)benzoic acid; DEA – deethylatrazine; DET – deethylterbuthylazine; DIA – deisopropylatrazine
Mass concentrations of individual pesticides determined in river/stream water samples collected at the beginning (March), peak (June), and end (August) of the 2015 pesticide application season. AMBA – 2-amino-4-(methylsulfonyl)benzoic acid; DEA – deethylatrazine; DET – deethylterbuthylazine; DIA – deisopropylatrazine

Mass concentrations of pesticide pollutants in river/stream water samples collected in the northwest part of Croatia across application season

Pesticide compound March 2015 (N=8) June 2015 (N=8) August 2015 (N=7)
γ (ng/L) γ (ng/L) γ (ng/L)
n Rangea Medianb n Rangea Medianb n Rangea Medianb
Mesotrione 0 3 36–107 0 0
Tembotrione 0 7 51–216 77 0
AMBA 0 6 54–444 74 1 61 <LOD
Terbuthylazine 3 9–13 <LOD 8 20–419 42 5 10–26 13
DET 1 9 <LOD 4 38–200 19 2 14–45 <LOD
Atrazine 5 10–16 11 5 12–34 13 5 9–24 14
DIA 5 5–32 6 6 17–123 28 2 19–24 <LOD
DEA 4 8–11 4 7 7–24 11 5 6–32 10
Isoproturon 1 146 <LOD 0 0
Diuron 0 2 22–30 <LOD 0
Acetochlor 0 1 28 <LOD 0
Metolachlor 7 9–11 9 8 11–3015 147 6 10–63 11
Chlorpyrifos-methyl 0 1 26 <LOD 0
Chlorpyrifos-methyl-oxon 1 21 <LOD 8 23–145 64 3 34–198 <LOD
Imidacloprid 1 73 <LOD 8 12 – 34 26 0

Methods for determination of pesticides and their degradation products in natural waters by SPE and HPLC-UV(DAD) or GC-MS(ITD) analysis

Method of analysis HPLC-UV(DAD) GC-MS(ITD)
Method 1λ (nm) Method 2λ (nm) Method 3aλ (nm) Method 4a m/z Method 5m/z
Pesticide Mesotrione – 220 Terbuthylazine – 222 Atrazine – 222 Trifluralin – 264 Terbuthylazine – 214
AMBA – 220 DET – 214 DEA – 214 Atrazine – 200 Chlorpyrifosmethyl – 286
Tembotrione – 205 Malathion – 205 DIA – 214 Terbuthylazine – 214 Chlorpyrifosethyl – 314
Chlorfenvinphos – 205 Terbuthylazine – 222 Acetochlor – 223 Malathion – 173
Chlorpyrifos-methyloxon – 205 DET – 214 Alachlor – 188 Chlorfenvinphos – 267
Imidacloprid – 270 Diuron – 210, 245 Metolachlor – 162 α-Cypermethrin – 163
Linuron – 210, 245
Chlortoluron – 210, 245
Isoproturon – 202, 245
SPE OASIS HLB C18 SDB-1 C18 C18 Polar plus/ SDB-1
Activation MeOH+H2O ACN+H2O MeOH+H2O MeOH+H2O MeOH+H2O
Solvent volume (mL) 2+2 5+5 2+5 2+5 2+5
Sample volume (mL) 500 500 500 1000 500
Eluent MeOH ACN+Et.ac Ac Et.ac Et.ac
Eluent volume (mL) 10 10+5 2 2 10

Number (N) of individual pesticide compounds, their mass concentration range, and the sum of pesticides mass concentrations (Σ) by river/stream across application season

River/Stream March 2015 June 2015 August 2015
N γ (ng/L) N γ (ng/L) N γ (ng/L)
Min Max Σ Min Max Σ Min Max Σ
Sutla 3 8 22 41 9 9 2564 3455 3 10 63 99
Krapina 7 9 146 219 10 22 3015 3992 5 6 198 248
Sava 1 2 9 73 81 11 10 242 947 4 9 45 77
Sava 2 4 6 11 35 11 7 149 498 – not analysed –
Drava 2 5 10 15 6 22 86 323 2 11 14 25
Plitvica 2 10 16 25 7 16 115 331 4 10 32 76
Bistrica 3 9 32 52 10 11 216 582 5 13 61 147
Bednja 5 7 16 56 10 12 444 867 6 11 66 161

Pesticides and pesticide degradation products analysed in this study

Class/Pesticide Chemical name Sa (mg/L) log Kowa pKaa
Dinitroaniline herbicide
Trifluralin 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)aniline 0.221 5.27 ND
s-Triazines and metabolites
Atrazine 6-chloro-N2-ethyl-N4-(1-isopropyl)-1,3,5-triazine-2,4-diamine 35 2.7 1.7
Deethylatrazine (DEA) 6-chloro-N4-isopropyl-1,3,5-triazine-2,4-diamine 2700 1.51 1.3b
Deisopropylatrazine (DIA) 6-chloro-N2-ethyl-1,3,5-triazine-2,4-diamine 980 1.15 1.2b
Terbuthylazine 6-chloro-N2-tert-buthyl-N4-ethyl-1,3,5-triazine-2,4-diamine 6.6 3.4 1.9
Deethylterbuthylazine (DET) 6-chloro-N2- tert-buthyl -1,3,5-triazine-2,4-diamine 327.1 2.3 1.35c
Phenylurea herbicides
Diuron 3-(3,4-dichlorophenyl)-1,1-dimethylurea 35.6 2.87 ND
Linuron 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea 63.8 3.0 ND
Chlortoluron 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea 76 2.5 ND
Isoproturon 3-(4-isopropylphenyl)-1,1-dimethylurea 70.2 2.5 ND
Chloroacetanilide herbicides
Acetochlor 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetamide 282 4.14 ND
Alachlor 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide 240 3.09 0.62
Metolachlor (RS)-2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(1-methoxypropan-2-yl)acetamide 530 3.4 ND
Triketone herbicides and metabolite AMBA
Mesotrione 2-[4-(methylsulfonyl)-2-nitrobenzoyl]cyclohexane-1,3-dione 1500 0.11 3.12
2-Amino-4-(methylsulfonyl) benzoic acid (AMBA) 2-amino-4-(methylsulfonyl)benzoic acid NA 0.38d 4.24d
Tembotrione 2-[2-chloro-4-methylsulfonyl-3-(2,2,2-trifluoroethoxymethyl) benzoyl]cyclohexane-1,3-dione 71000 -1.09 3.18
Organophosphorous insecticides and oxo- metabolite
Chlorpyrifos-methyl O,O-dimethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate 2.74 4.00 ND
Chlorpyrifos-ethyl O,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate 1.05 4.7 ND
Chlorpyrifos-methyl-oxon Dimethyl (3,5,6-trichloropyridin-2-yl) phosphate NA 1.91e NA
Malathion Diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate 148 2.75 ND
Chlorfenvinphos [(EZ)-2-chloro-1-(2,4-dichlorophenyl)ethenyl] diethyl phosphate 145 3.8 ND
Pyrethroid insecticide
α-Cypermethrin Racemate comprising (R) and (S) α-cyano-3-phenoxybenzyl- (1R,3R)-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropane- carboxylate 0.004 5.8 ND
Neonicotinoid insecticide
Imidacloprid N-{1-[(6-chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl}nitramide 610 0.57 ND

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