Photodegradation of acetochlor in water and UV photoproducts identified by mass spectrometry

Jourmal 0f Ensrnmental Sriences Vol.15. Vo.6.,p.783- -790.2003出10(042.GNI1- 62AArticle D: 1001 0742(2003)06-0783-08CLC number: X131Document code: APhotodegradation of acetochlor in water and UV photoproductsidentifed by mass spectrometryZHENG He-huil ，YE Chang-ming*(I, Intitute of Envinument & Health Related Prxdue Safely, Chinese Center for Disease Control and Prevenion. Beijing 10021. (China;2. Research Center lor Eo-Envionmental Soiences, Chine Arademy of Sienee, Bejig 100850 China. E mail; yerchm @ nail. reese.ac.cn. )Abstract; The sunlight photodngodation half-lives of 20 my/L acetochlor wr 151, 154 and 169 days in de-ionized water. river waler andpuadd!v water, reperively . When exposrd to ulraviolet 《UV) lighl, acetochlor in aqueous solution was rspidly degraded. The bl-lives were7.1.10.1, and 11.5 min in de ionised water. river waler and paddy waler. rpectively. Ponoproductes of acrtochlor mre ienified by陆cthrornatogaphy/088s spectrometry( GC/MS) and found at least twelve photoproducts resulted fro dechlorination with subsrquent hydroxylationand eyelization prcse.s The chemiral structures ol ten phntproducts were presumed on the basis of mos spetum iterereatin andlitenture data. Photproducts are identified a 2-lby-6-methylaniline; N. Ndiethylaniline; 4, 8-dimethy-2-oxo-1.,2.3.4 trahydroquino-ine 2-orxu=N-( 2-ethy1-6- methylphenyl )-N-( ethorymeuhy!) aceramide; N-( ethoxymnethyl )2+thyl_6-'metbylformanilidr; I-hyroxyacetyl-2.pthoxy-7-ethylind ale; 8-tey-t1oyory-2-0x0-1,, 2, 3, 4-etrahydroquinolineie 4, 8-mltyl-.lmoyoeteyl.1.xxo-1, 2. 3, 4.trahydroquinolie 2- hydmxy.2'etbyI6'methy-N-( ethoxymethyl ) acetanilide and a corpound relatoed tn ecetochlor. The other tWOphotoprodurts were delected by GC/MS alhough their cherical strueture was unknown,Keywords: aceochlor; poloporoducts; phnodeeradation; CC/MS; betbicideIntroductionAcelochlor [2-chloro-N-( ethoxymethy)-N-(2-ethyl-.6-methylphenyl) acetamide] (Fig. 1) was a germination ~oRao^.inhibitor used widely to control competing grasses andsome broadleaf weeds in com( Capel, 1995 ). AcetochlorAcetochlorAlachiorMetolachlorwas applied preemergent to plant growth. Its solubility inwater was 223 mg/I. al 25C. lts persistence in soils when Fig.1 Chemical surucure of uceachlor, alachlor endused at the recommended rales was generally 8 to 12 mrlolachlorweeks, but the time might vary, depending on soil lype and climatic conditions. Acetochlor wasconditionally registered in March 1994 by the U. S. Environmental Protection Agency( USEPA, 1994) andhas been classified as a B-2 carcinogen .Use of acelachlor has been increasing and already is substantial. More than 10 million kg ofacelochlor( active ingredient) has been applied every year since 1997 in China( Wang, 1999). It was themost widely used agricultural herbicide in China. About 3.4 million kg was applied in 1994 ( USDA,1994). According to a survey conducted on 10 com-growing states, the fraction of com acreage treatedwith acetochlor increased from 7% in 1994 to 20% in 1995. In 1995, usage increased to about 10.8million kg (USDA, 1995). By 1996, acetochlor applications had reached 13.5 million kg, making it thethird most heavily applied com herbicide in the Midwest of USA, behind only atrazine and metolachlor(USDA，1996). Although acetochlor has been used for years in Asia, Europe and South Africa, limiteddata has been collected to determine its fate and transport in the environment(Yu，1998; Capel, 1995).Kolpin et al . ( Kolpin, 1996) reported results from sampling conducted during 1994. Acetochlor was foundin 35% of 53 midwestem streams sampled from May through July. Most of the detectable levels in rain andstreams ocured during the spring application period. Maximum concentations of acetochlor found in 1994were2.5 yug/L(rain) and 1.2 prg/L( streams). In 1995, the acetochlor concentrations in some midweststreams and in the Missppi River at Baton Rouge had increased dramatically compared with 1994concentralions( Crawford, 1997). Kalkhoff et al. ( Kalkhoff，, 1998) reported the median value of thesunmed concentrations of acetochlor, alachlor, and metochlor was less than 0.05 ug/L in groundwater and0. 13 ug/L in surface water, acetochlor degradales were delected in about 10 % of the wells sampled. The中国煤化工Foundetion item; The Nationl Natural Scienee Foundetion of China( No.29837170)YHCNMHG7847HENC He-hui p al .Val. 15oxanilic and sulfonic acid degradates of acetochlor were presented in 50% of the streams sampled. Duringthe growing season of 1997, 78% of 375 samples cllected at 32 sitr;am sites in the Misissippi River Basincontained detectable concentrations of acetochlor. Concentrations in only 2% of the samples exceeded 2pug/L(Clark,1999).Acetochlor was a :hloracetamide herbicide having chemical strueture and properties similar to those ofalachlor[ 2-chloro-N-( methoxymethyl)-N-(2, 6-diethylphenyl) acetamide ] and metolachlor [ 2-chlom-N-(2- methoxy- I-methylethyl )-N-( 2-ethyl-6 methylpheny|) acelarmide (Fig. 1). The anticipated aim ofacetochlor registration in the USA was that it will subsantially reduce the use of other corm herbicides suchas atrazine, alachlor， metolachlor, 2, 4-D and cyanazine. The USEPA( USEPA，1990) had set themaximum contarminant level of alachlor or melolachlor in drinking water at 2 1ug/I.. Chloracetamideherbicide degradation products were generally of lower molecular weight and more oxidized than the parentcompound, therefore they might be consequently more water soluble, more mobile, and have a greaterpotential to leach( Baker, 1993; Kolpin， 1994; 1995a， 1995b; Malcomber， 1992). The fate ofacetochlor in natural walers thus was of interest . One possible degradation pathway was photodegradation.Sonich el al . (Somich, 1988) reported that alachlor was dechlorinated upon UV iradiation and forms anumber of internediates that retain the aromatic ring and carbonyl carbons . Photoprnducts ineludehydroxyalachlor. norchloralachlor, 2, 6 diethylacelanilide, 2-hydroxyl-2' , 6'-diethyI-N-methylacelanilide,and a lactam. Penuela and Barcelo( Penuela, 1996) reported that alachlor gave five photoproducts after UViradiation. Three photoproducets were identifed unequivoally: 2-hydrxyl-2' ，6'-diethyl-N-methylacetanilide, 4- methyl-8-ethyl- 1- methoxymethyl-2-oxo-l，23， 4-tetra-hydroquinolinehydroxyalachlor. Mathew and Khan( Mathew，1996 ) found that hydroxylation ，dehalogenation,oxoquinoline formation， and demethylation were the main processes during the photodegradation ofmetolachlor. Kochany and Maguire( Kochany, 1994) found that sunlight photoproducts of metolachlor inwater resulted from dechlorination, bhydroxylation ，dehydrochlorination with subsequent morpholine ringformation, and N-dalkylation. Chiron et al . ( Chiron, 1995) reported that fourteen photoprducts resultedfrom alachlor decblorination with subsequent hydroxylation and cyclization processes. The two majorphotoproducts were identified as hydroxyalachlor and 4-methyl- 8 -ethyl- 1-methoxymethyl-2-0x0-1,2,3,4- .tetrahydro-quinoline. Wilson and Mabury( Wilson, 2000) found that monochloroacetic acid was a majorphotoproduct of alachlor, metolachlor， butachlor in synthetic field water. Sunlight photodegradation ofmetolachlor was found slow in aqueous solution, 6%-8% in a month( LeBaron, 1988; Chesters, 1989) .Indirect photolysis of acetochlor was sludied ，summer-time half-lives of 1-20 days for aretochlor wereestimaled for the Blue Eath River ( southem Minnesota) ( Brekken，1998). According to Potter andCarpenter( Potter, 1995), groundwater samples collected beneath a Mssachusetts com field were analyzedby GC/MS. 20 compounds were detected whose electron impact( EI) and chemical ionization(CI) MS dataindicaled that they were derived from alachlor, presumably via environmental degradation. Mangiapam etal .(Mangiapam，1997) reported that the several alachlor metabolites were identified. Nine compoundswere confirmed by comparison with synthetie standards and the formulae of other seven compounds werepresumed on the basis of spectrum interpretation and literature dala. Jacobsen( Jacobsen, 1991 ) reportedthat degradation， in particular， cleaveage o[ alachlor’ s N-methoxylmethyl group， contributed todetoxification. But other published data had indicated that at least one of the residues， 2，6-diethylaniline, is a promutagen( Kimmel, 1986). We also used to research on the photodegradation ofbutachlor( Zheng, 2001a; 2001b), 11 photoproducts were discovered .In this paper, the photodegradation of acetochlor in water was studied. We report the results ofphotoproducts analyzed by CC/MS to provide useful data for acetochlor risk asessment.1 Materials and methods1.1 Materials and apparatusAcetochlor of 99.5% ( analytical reference standard) were obtained from the Monsanto Company(St .Louis. MO, USA). Acetone ，methanol ，petroleum ether. sodium chloride, and anhydrous sodium sulfateof analytical-reagent grade were purchased from Beijing Chemical Factory. Methanol was purified byreditillation. Supplies of paddy water from Bejing Haidian rice fic'2 aningmi canalwhich imigated the rice field were filtered with a microporous fu中国煤化工r reagenTYHCNMHGNo.6Photodegradation of acctochlor in waler and UV photoproducts ientified by mass spectometrygrade from various suppliers .A LC-6A high performance liquid chromalography was equpped with Shimadzu setropotoeniedelector. The stainless steel column used(25 cm x 4.6 mm i.d. ) was packed with DuPont (DS chemicallybonded phase ，paticle sie 10 pum, and was pre-lested by the manufacturer. The detection wavelengh of215 nmn was seeted in all measurements for acetochlor. The mobile phase was mehanl-wter(80/20. v/v) al a flow rate of I .0 ml/min. The relention time of acetochlor was 6.9 rmin.GC aralysis were performed using a Finnigan trace gas chromatograph(2000 series) coupled with aFinnigan Voyager mass spectrometer detector( MSD), and Xcalibur sofware. A 1I5 mx0.25 mm i.d.RTX5 colunn(0.25 pμm film thickness) was used under the fllowing temperature conditions: initiallemperature at 50C，20 C/min at 200C，10 C/min at 280C.3 min final hold. The inlet temperaturewas 250C. The helium carrier gas flow rate was 1 ml/min. The MSD was operated in electron impactmode with delection voltage 350.0 V and a source temperature of 200C，in full scan mode from m/z 30 to500.1.2 Experimental procedureIradiations were caried out using a 100-W medium pressure : 100quartz mercury vapor lamp( produced by Beijing Elcti'e Light Source365435Institute) a8 UV iradiation source. The lamp was immersed inside a4950-| 405quartz glass immersion well through which cold tap waler flowed to 员2580keep the lamp cool . The emission spectra o[ light source is shown in曼Fig.2. The light intensity was 658 pW/cm2 (measured by ZDZ-1 UV豆3504S0 550iradiation photometer, 254 nm). We had studied the UV photolysisWavcleagth, mof acetochlor in water solution using a 100- W medium pressure quartzEnision :spectra of mediumn presuremercury vapor lamp .20 ml of sarmples of aqueous solution in a quartzquart nercuny vapor lamptest tube were imadiated with the l00-W medium pressure quartzmercury vapor lamp. Samples of 25 μ were removed every 2 min and analyzed by HPLC. The sampleswere totally iradiated for 10 min. The dark control sample was wrapped in aluminum foil and was notdegradation.In order to determine photoproducts of acetochlor, 20 ml of 20 mg/L acetochlor aquous solution in aquartz test tube was iradiated for 30 min. The whole water samples were extracted into petroleum ether andconcentrated l0 about 3 ml under reduced pressure . The concentrated extract was directly dried under agentle stream of nitrogen gas and the residue was dissolved in 1 ml of methanol, then analyzed by GC/MSto detemine photoproducts.Sunlight photodegradation experiments were done to estimate the rate constants and half-lives inBeijng( about latitude 40 degrees north, August 16, 2000 to October 14. 2000). The experiments weredone in quartz test tubes containing 20 ml of 20 mg/L acetochlor in de- ionized water, river water and paddywaler. Apropriale dark control samples were wrapped in aluminum foil. All samples were placed outdoorduring the day and night except rain days. Peridically, the samples was analyzed by HPLC-UV every 7days.2 Results and discussion2.1 Photodegradation kinetics of acetochlor in waterAcelochlor were scanned using a Shimadzu DU-650spectrophotometer. Acetochlor' s main absorbance wavelength was lessthan 280 nm(Fig. 3). It was indicated thal pholoclegradation ofacelochlor was mainly caused by absorbance of ultraviolet light less than280 nm wavelength. Since lttle solar radiation below 300 nm reachesthe earth’s surface ，sunlight photodegradation of acetochlor must be19一 250 300slow. To accelerate photolysis testing and avail to identify as manyphotoproducts as possible, a 100-W medium pressure quartz mercuryFg:.3 Acruclor aopion petogann vapor lamp was used in ourpreaks1. in the meharol sluion; 2. in the waterThe natural loganthm ve中国煤化工InentrtionsolutionTYHCNMHG86ZHENG He-hui et al.vol.ISto the concentralion al a given time(1) Vs time were plotted and the( pseud-first-order) rate c:onstants(k)were determined by calculating the slope of the line, the half-life iu2 was calculaled by ln2/k .ln(Co1Ct) = ht,(1)1 = ln2/k.Where，Co is the initial concentratin; C; is the concentration al a given time (t).70The UV photolysis of 20 mg/L acetochlor in60 twater is shown in Fig. 4. The half-lives of50 tucetoc:hlor at an initial concentration of 20 mg/L were40 t7.1, 10.1 and 11.5 rmin in de- ionized water, river。Deioaized walerwater and paddy water, respectively. For sunlightA River waterx Paddy wsterpholodegradation， the loss of all dark controlsamples was less than 3.4%， So the otherdegradation might be negative. After 49 dayssunlight iradiation, the residues of acetochlor in de-Fig.4 The UV polysis of acetochlor in waterionized water， river waler and paddy water were15.1, 15.6 and 16.0 mg/L. According to Equations(1) and (2) calculation, the hl-lies of sunlight were 15I，1I54 and 169 days photodegradation in de-ionized water. river water, and paddy water. The resulte showed that the sunlighl pholodegndaion ofacetochlor is slow in water under experimental conditions .2.2 Identification of photoproducts in waterWhen exposed to UV light, acetochlor in aqueous solution was rapidly degradation, giving at leasttwelve photpoducts Table 1). After iradiation for 30 min, lhe major photoproduets were compounds 8，9, and 10. The typical GC/MS caromalograrn of the experiments pholysis is shown in Fig 5. Compound awas the parent compound acetochlor. The mass spectrum of acetochlor is shown in Fig. 6. Cormparing withthe standard mass spectum of acetochlor, the probabiltly of the conmpound a crreponding to acetochlorwas 96.8% . Relention time of acetochlor was 7.75 min. The molecular ion peak was at m/z 269. The ionpeakat m/z 234, 223, 174，162, and 146 might corepond the molecular ion 10 loss of C], lose ofCH,OH, loss of CHOH and CH.CI, lose of CH, H and COCH,CI, loss of CH,OH and COCHCI.The base peak ion al m/z 59 was C H,OCH2.100095404.53.0556.0657.07.558.085909310.010511.011.512.0L. minig.s The typicad GCMS chroatogam of the eprimets polyis1002'5918cu146121223.140521 4174.17.0 911 12.1. .. 31 1601 |2224.2510 6s01720 1021 1s222 2542 29272 293o4.50 80 100 12016020022024026028030040Fig.6 The mass spctnumn odf co中国煤化工TYHCNMHGNo.6Pholodepradation of acetochlor in waler and UV photoproducts ienified by mass specromery787Table 1 Photoproducts of actochlorMass spertrl dataRetentionPeak MW "Bp'Secondary ionstime, minPhntoprodurt13565~913.942. ehyl-6-methylaniline1491347064.91N, Ndistylanline175751813476.754.,-dinethy1-2-oxo- .2.3.4-tetrahyroquinoline24959321474206.882-xr.N-( 2-tvyl-mebylpher )-N-( ebaxy-methy)acelamnde22116934226.99N-(ethoxyoethyI) 2-yhy-6-o-thybormenilidle46160047.15I-hydroxacelyl-2-ethoxy-7- ehylindole512127.23Acetochlor related33237.28R-.1hyl-1-.thoxymethyl-2-oxo-1, 2. 3, 4-1etrahy-droqunoline233187607.304.8-dimethyl 1-ethoxymethy-2-.xn-1, 2.3, 4-trahyruinoline1(2517.482-hydrory-2'-ethyl. 6'-methyl-N-( ethoxynethyl )acetanilideIAretochlor related887.69Noles: * MW . mlelur weigh; : BP. base peakThe CC/MS chromatogram and mass spectra of photoproducts 1-12 are shown in Fig.7--Fig.9. Thestruetures of photoproducls 7, 1I, and 12 were unknown. It should be noted that the structural assignmnentsshowed for those photoproducts were tentative: their full idenification is still under investigation and mayrequire other analytical methods such as NMR afer an isolation step. Photoproducts corresponded mairnly todechonination process o{ acetochlor. We did not find the litratures with photoproducts of acetochloridentifed by MS. Spectra of the presumed photoproducts were compared with olbher chloracelamideherbicide literature data, when available.100100p250so[、10614.0 4.5 5.0 5.5 6.0 6.50 100 130 200 250 ', minNH2身10g15.1650 9101 I04，1μ1721922 230 2390学x0200 250100 150 20025w/zig.7 The GC/MS chromatogan and mass spectra of photoprouete 1- 3Photoproduct 1, with MW 135, might correspond to 2-ethyl-6-methylaniline. Retention time was3.94 min. Observing the spectrum, molecular M' (135) could lose CH, to give the base ion peak at m/z120, CH and CH,CH, to give the ion peak at m/z 91. The main ion peaks at m/z65, 77, 91, 120. and135 of photoproduct 1 matched with the standard mass spectrum of 2-ethyl-6-methylaniline very well.Photoproduct 2, with MW 149, might correspond to N, N-diethylaniline. Retention time was 4.91min. Observing the spectrum, molecular M' (149) could lose CH3 to give the base ion peak al m/z 134,CH, and CH2CH2(one Y H rearrange) to give the ion peak at m/z 106. The main ion peaks at m/z 77.106，134, and 149 of pholoproduct 2 matched with the standard mass spectum of N, N-diethylaniline verywell.Photoproduet 3，with MW 175， might corespond中国煤化工，3，4-tetrahydroquinoline . Retention time was 6.75 min. The base peaEwIz 175. .The molecular ion could lose CH3 to give the ion peak at m/z 16MHCNMH Gk al m/z .788ZHENG He-hui e al .vol.I510010036soYoH6.86970.727374。SO 10102000 230 300i, min~on-ano 100; 750u1722411321卫。11+0000200 25000150200250 300120;510038s0503u| 101200100115000250300Fig.8 The GC/MS chromatoram and mass spectas of potoproducts4- -810311 950_ 011100877.2 73 7.4 7.5 7.6 1.2050 200 250 300100;mu12210130于20021111150 100 150 200 250 3005o 100150 200”250 300n/z10]10 91OH50]oL. 212707100 150 200 250 300mFig.9 The GC/MS cromatogam and mas secte of poproduete 9-12147, CH, and CO to give the ion peak at m/z 132.Photoproduct 4，with MW 249， might correspond to 2-0xo-N-( 2- ethyl-6- methylphenyl )-N-(ethoxymethyl) acetamide. Relention time was 6.88 min. The base peak ion at m/z 59 was Cq H2OCH2The mlecular ion could lose CH,0H, to give the ion peak al m/z 203, and CHO to give the ion peak atm/z 174. The mass spetrum of photoproduet 4 was similar to (hat of 2-0xo-N-(2. 6dithylphenyl)-N-(methoxymethyl) acetamide which was one of melabolites of alachlor( Jacobson, 1991).Photoproduet 5, with MW 221 , might correspond to N-( ethoxynethyl)-2- ethy)-6- methylformanilide .Relention time was 6.99 min. The molecular ion lost G H,OCH2 to give the base peak ion at m/z 162, andC0 to give the ion peak at m/z 134. The ion peak al m/z 59 was C2 H,OCH2 peak.Photoproduet 6，with MW 249， might correspond to 1-hyrxyacetyl-2-ethoxyl-ethylindole.Relention time was 7. 15 min. The molecular ion could lose CH,O, to give the ion peak at m/z 204, andC2HOH to give the ion peak at m/z 203. The molecular ion could lose CH,0 and COCHOH(one yHrearrange) to give the base ion peak at m/z 146. The molecular ion could lose C2 HgOCH and COCH2OH,to give the ion peak at m/z 132.Photoproduct 8，with MW 233， might corespond to 8-ethyl-1-ethoxymethyl-2-ox0-I, 2, 3, 4.lelrahydroquinoline. Retention time was 7.28 min. The molecular ion could lose CH to give the ion peakal m/z 204，CH,0 to give the ion peak at m/z 188, CHOH to give the ion peak at m/z 187. Themolecular ion could lose C2 H,0CH2 and CH2 to give the base;- reak at m/z 59中国煤化工was Cp H,0CH; peak.PYHCNMHGNo.6Pholodegradation of acetocblor in waler and UV potpnducts ienuifed by mass spetronetr89Pholoproduct 9, with MW 233 , might crespondto 4, 8-dimethyl-1-ethoxymethy)-2-0x0-1, 2, 3, 4-加,letrahydroquinoline. Relention time was 7.30 min.Pholoproduct 9 and pholoproduct 8 should be similarcompounds, since their relention lime was almostasimultaneous time, and the location of the ion peaks+HQ,was almost he same place only the relative abundanceof the ion peaks was different. The molecular ion couldlose C2H3 to give the ion peak at m/z 204，CH,O toar.ocH，ayocHygive the ion peak at m/x. 188, Cq H,OH to give the baseNofiyrOHion peak at m/z 187, C;H,0CH2 and CH2 to give theion peak at m/z 160，C2H,OCH2 and COCH2 to giveHthe ion peak at m/x 132. The molecular ion could lose anoCH;OCH2 to give the ion peak at m/z 174. Accordingto the mechanism scheme of Somich et al . ( Somich,1988). The ion al m/z 174 could lose two H l0 give theion peak al m/z 172. The ion peak at m/z 59 wasFig. 10 The mechenism of actochlor potolegrndationCz H,0CH; peak .Photoproduet 10, with MW 251, might correspond to 2-hydroxy 2'-ethyl -6'-methyl-N~( ethoxymethyl)acetanilide. Retention time was 7.48 min. The base peak ion al m/z 5 was C2 H,OCH; . The ion peak atm/z 205， 174， 146 might correspond the molecular ion to lose of C2 H,0H, C2 H,OH and CH,OH,(x HgOH and COCH20H respectively . 'The mass spectrum of pholoproduct 10 was similar to thal of 2-hydroxy-2' .6'-diethyl-N-( methoxymethyl)acelanilide which was one of photoproducts of alachlor( Penuela,1996).Dechlorination was presumably the first step in photodegradation of acetochlor in waler when iradiatedwith UV light. Absorption of a pholon by the carbonyI of acetochlor was fllowed by los of chlorine at thea-carbon, affording intermediate 13. Intermediate 13 proceeds to degrade to give various photoproducts.Photoproduct I and pholoproduct 2 might be formed by other pholoproducts proceeding to degrade. Fig. 10shows the mechanism of acetochlor photodegradation. However, according to Wilson and Mabury' s .( Wilson，2000 ) investigation, monochloroacetic acid was a major photoproduct of chloroacetanilideherbicides in synthetic field water.Monochloroacetic acid may is formed on another pathway ofphotodegradation. But monochloroacetic acid was not detected in our studies , maybe monochloroacetic acidwas neglected due to our analytical method limitation, since monochloroacetic acid is a strong polarproduct. It should be noted that photolysis rales and photoproduct formation are actually dependent on theintensily and the wavelength distribution of the light used . The photodegradation mechanism and productsof acetochlor in our study is not all the same as sunlight photodegradation on natunal environmentalconditions .3 ConclusionsTwelve photoproducts of acetochlor were identified by CC/MS after photolysis . The chenical stnucturesof ten photoproducts were presumed on the basis of mass spectrum interprelation and literature datacorresponding to 2-ethyl-6 -methylaniline; N, N-diethylaniline; 4, 8-dimethyl-2-oxo-1, 2, 3, 4-tetrahydro-quinoline; 2-0x0-N-(2-ethyI-6- methylphenyl)-N- ethoxymethy!) acetamide; N-( ethoxynethy)-2-ethy-6-methyformanilide; lI-hydroxyacetyl-2- ethoxyl-7-ethylindole; 8-ethyl-1-ethoxymethyl-2-ox0-1. 2, 3, 4-tetrahydroquinoline; 4 , 8-dimethyl-1-ethoxymethyl-2-oxo-1 ,2,3,4-tetrahydroquinoline; 2-hydroxy-2 -ethyI-6'-methyl-N-( ethoxymethy1) acetanilide and a compound related to acetochlor. The other two photoproductswere detected by GC/MS although their chemical stnucture was unknown. Photoproduct 10 [ 2-hydroxy-2'-ethy-6'-methyl-N-( ethoxymethyl ) acetanilide ]was found to be a major product in photolysis.Dechlorination was presumably the first step in photodegradati| 中国煤化dation ofacelochlor was slow in water under the experiment conditions. Tzochlor inde- ionized water, river water and paddy water were 151, 154, alMYHCNMHGxposedto90ZHENC He-hui et al.Vot. 15UV igh, acetochlor in aqueous solution was rapidly degraded, the hal-lives of 20 m/L aceochlor were7.1. 10.1, and 11.5. min in deionied water. river waler and paddy waler, epetively.Acknowledgements: The authors wish to thank Huajun Chen from Rejig Foresty UInivesity to givevaluable suggestions for CC/MS analysis .References:BakerDB. BushwayRJ，AdamsSA 《al.. 1993. Innoss scroens for slacblor in rumal wll: fale poitive and an alechlor soilmetabolielJI. Envinn Sri Technul. 27: 562- 564 .BrekkenJ F, Brezonik P L, 1998. Indiphere.Capel P D, Ma l. Schrover B R et al..1995. 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