順硝烯新煙堿殺蟲(chóng)劑環(huán)氧蟲(chóng)啶在水中的光降解

鄧亞運(yùn),莊英瀅,馮 越,陸思源,程家高,徐曉勇,2*(.華東理工大學(xué)藥學(xué)院藥物化工所,上海市化學(xué)生物學(xué)重點(diǎn)實(shí)驗(yàn)室,上海 200237；2.上海生物制造技術(shù)協(xié)同創(chuàng)新中心,上海 200237)

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順硝烯新煙堿殺蟲(chóng)劑環(huán)氧蟲(chóng)啶在水中的光降解

鄧亞運(yùn)1,莊英瀅1,馮 越1,陸思源1,程家高1,徐曉勇1,2*(1.華東理工大學(xué)藥學(xué)院藥物化工所,上海市化學(xué)生物學(xué)重點(diǎn)實(shí)驗(yàn)室,上海 200237；2.上海生物制造技術(shù)協(xié)同創(chuàng)新中心,上海 200237)

摘要：為了正確評(píng)估新型殺蟲(chóng)劑環(huán)氧蟲(chóng)啶(CYC)的環(huán)境風(fēng)險(xiǎn),了解環(huán)氧蟲(chóng)啶在水環(huán)境中的光降解規(guī)律,探討了CYC初始濃度、溫度、初始pH值、過(guò)氧化氫濃度及硝酸根對(duì)CYC光降解的影響.結(jié)果表明,CYC的光降解符合一級(jí)動(dòng)力學(xué)反應(yīng).直接光降解中,隨濃度降低、溫度升高,光解速率加快,環(huán)氧蟲(chóng)啶的反應(yīng)活化能為21.27kJ/mol.通過(guò)測(cè)定CYC的pKa值為3.42以及模擬計(jì)算CYC不同粒子形式的光反應(yīng)活性,可知pH值對(duì)CYC光解的影響較為復(fù)雜:酸性條件下,CYC的降解速率取決于其形態(tài)(陽(yáng)離子和中性粒子)與單線(xiàn)態(tài)能量;堿性條件下,降解速率主要受羥基自由基數(shù)量的影響.間接光降解中,硝酸根和過(guò)氧化氫對(duì)CYC光解均表現(xiàn)為促進(jìn)作用.在評(píng)估環(huán)氧蟲(chóng)啶的環(huán)境風(fēng)險(xiǎn)時(shí),應(yīng)綜合考慮環(huán)境因素對(duì)其降解的影響.

關(guān)鍵詞：新煙堿類(lèi)殺蟲(chóng)劑；環(huán)氧蟲(chóng)啶；光降解；羥基自由基；HOMO-LUMO值

* 責(zé)任作者, 教授, xyxu@ecust.edu.cn

近年來(lái),新煙堿類(lèi)殺蟲(chóng)劑被認(rèn)為是農(nóng)業(yè)領(lǐng)域的里程碑[1].是自擬除蟲(chóng)菊酯商業(yè)化后銷(xiāo)售量增長(zhǎng)最快的一類(lèi)農(nóng)藥,其全球銷(xiāo)量占整個(gè)殺蟲(chóng)劑市場(chǎng)的24%,約為26.32億美元[2].至今為止,已經(jīng)商業(yè)化的新煙堿類(lèi)殺蟲(chóng)劑包括吡蟲(chóng)啉、噻蟲(chóng)啉等.當(dāng)殺蟲(chóng)劑在田間噴灑至土壤表面、水體和植物表面之后,它們將在自然環(huán)境中經(jīng)歷生物降解、水解及光解過(guò)程,在這些變化過(guò)程中往往會(huì)對(duì)環(huán)境產(chǎn)生負(fù)面的影響,因而必須進(jìn)行其環(huán)境行為的研究.有關(guān)新煙堿殺蟲(chóng)劑光降解研究已有報(bào)道[1,4-5], Pe?a等[6]研究了噻蟲(chóng)嗪和噻蟲(chóng)啉在污水、溶解有機(jī)質(zhì)和表面活性劑的水溶液中的光降解.

作為對(duì)吡蟲(chóng)啉的抗性害蟲(chóng)具有顯著活性的新煙堿殺蟲(chóng)劑,環(huán)氧蟲(chóng)啶(CYC)具有良好的市場(chǎng)前景,Shao等[7]在2010年首次對(duì)它進(jìn)行了報(bào)導(dǎo).該殺蟲(chóng)劑由華東理工大學(xué)李忠教授等設(shè)計(jì)合成,具有廣譜和高效的殺蟲(chóng)活性,極有前景進(jìn)入市場(chǎng)成為國(guó)際上具有重要影響力的新一類(lèi)殺蟲(chóng)劑.因而很有必要進(jìn)行環(huán)氧蟲(chóng)啶環(huán)境行為的研究,為環(huán)氧蟲(chóng)啶的進(jìn)一步開(kāi)發(fā)和安全合理使用以及最終消除可能產(chǎn)生的環(huán)境污染提供科學(xué)依據(jù). Liu 等[8]研究了環(huán)氧蟲(chóng)啶在淹水無(wú)氧土壤中的降解情況.然而關(guān)于環(huán)氧蟲(chóng)啶在水環(huán)境中的光穩(wěn)定性還缺乏研究.

本文對(duì)環(huán)氧蟲(chóng)啶在水中的光穩(wěn)定性進(jìn)行了研究,包括直接光降解和間接光降解兩部分.考察了濃度、溫度、pH值、過(guò)氧化氫及硝酸根等影響因素,以期為評(píng)價(jià)環(huán)氧蟲(chóng)啶的環(huán)境特性提供科學(xué)依據(jù).

1　材料與方法

1.1 材料

用于HPLC分析的乙腈為色譜純,購(gòu)自Merck公司;MilliQ超純水(Milli-pore, 18M?·cm);環(huán)氧蟲(chóng)啶標(biāo)準(zhǔn)品(實(shí)驗(yàn)室自制,含量≥99.0%).其它試劑均為分析純.

1.2 儀器

XPA系列走馬燈式旋轉(zhuǎn)光反應(yīng)儀(南京胥江機(jī)電廠(chǎng));Agilent 1200液相色譜儀,二極管陣列(DAD)檢測(cè)器;光電分析天平,Mettler Toledo EL204,精確到0.1mg;pH精密酸度計(jì),雷磁PHS-3C;Sirius T3理化常數(shù)儀.

1.3 實(shí)驗(yàn)方法

使用Sirius T3理化常數(shù)儀進(jìn)行空白樣實(shí)驗(yàn),測(cè)定試驗(yàn)參數(shù),測(cè)定環(huán)氧蟲(chóng)啶的pKa值.

采用Chemoffice軟件構(gòu)建小分子三維結(jié)構(gòu),采用Gaussian軟件,分別計(jì)算環(huán)氧蟲(chóng)啶小分子的HOMO和LUMO值并計(jì)算軌道差,預(yù)測(cè)環(huán)氧蟲(chóng)啶不同狀態(tài)下的反應(yīng)活性.

用超純水準(zhǔn)確配制環(huán)氧蟲(chóng)啶的溶液,同時(shí)添加不同濃度的化合物作為影響因子,取新鮮配制的溶液于50mL石英試管中,置于光化學(xué)反應(yīng)儀上,進(jìn)行光照反應(yīng),并設(shè)置鋁箔包裹的黑暗對(duì)照.燈源為300W高壓汞燈,光照時(shí)石英試管距光源10cm.間隔一定時(shí)間取樣,對(duì)樣品進(jìn)行HPLC分析.在pH對(duì)環(huán)氧蟲(chóng)啶光降解影響實(shí)驗(yàn)中,用NaOH和HCl調(diào)節(jié)超純水的pH值,并使用該pH的溶液配制環(huán)氧蟲(chóng)啶溶液.

采用一級(jí)反應(yīng)動(dòng)力學(xué)描述光解反應(yīng),并使用ln(Ct/C0)-t線(xiàn)性擬合得到一級(jí)反應(yīng)速率常數(shù)k.公式T1/2=ln2/k計(jì)算半衰期.

1.4 分析方法

CYC的定量分析采用Agilent 1200液相色譜分析.分析柱為Zobarx Extend-C18 (5μm, 250mm×4.6mm),柱溫25℃.流速為1ml/min,紫外檢測(cè)波長(zhǎng)為340nm,自動(dòng)進(jìn)樣,進(jìn)樣量為10μL.流動(dòng)相為甲醇/水=30:70(體積比),樣品運(yùn)行時(shí)間為6min.此分析條件下,環(huán)氧蟲(chóng)啶的保留時(shí)間為4.39min.

2　結(jié)果與討論

2.1 環(huán)氧蟲(chóng)啶的直接光降解

2.1.1 濃度對(duì)環(huán)氧蟲(chóng)啶光降解的影響 從表1和圖1可見(jiàn),濃度為5×10-5,1×10-4, 2× 10-4mol/L的環(huán)氧蟲(chóng)啶光降解速率常數(shù)分別為0.0911,0.0578,0.0294min-1,環(huán)氧蟲(chóng)啶初始濃度增加,光降解速率常數(shù)k減小.與Orellana-García等[9]對(duì)除草劑氨基三唑、二氯吡啶酸、氯氟吡氧乙酸、二氯苯二甲脲光解的研究結(jié)果一致.本研究中同時(shí)也進(jìn)行了對(duì)照暗反應(yīng)實(shí)驗(yàn),結(jié)果表明環(huán)氧蟲(chóng)啶在無(wú)光照下沒(méi)有降解,說(shuō)明水解或生物降解對(duì)環(huán)氧蟲(chóng)啶的光降解沒(méi)有貢獻(xiàn).

2.1.2 溫度對(duì)環(huán)氧蟲(chóng)啶光降解的影響 實(shí)驗(yàn)結(jié)果見(jiàn)表1與圖2,表明溫度對(duì)環(huán)氧蟲(chóng)啶光解有重要影響.15℃,25℃,35℃下,環(huán)氧蟲(chóng)啶光降解半衰期對(duì)應(yīng)為11.04,7.61,6.21min.15℃時(shí)環(huán)氧蟲(chóng)啶的光降解速率僅為35℃的56.25%.可見(jiàn)升高環(huán)境溫度,環(huán)氧蟲(chóng)啶光降解速率常數(shù)增加,反應(yīng)加快.環(huán)氧蟲(chóng)啶的光降解速率常數(shù)與溫度之間的關(guān)系,遵循Arrhenius-type經(jīng)驗(yàn)式:

表1　環(huán)氧蟲(chóng)啶在不同條件下的光降解動(dòng)力學(xué)常數(shù)Table 1　Cycloxaprid photodegradation kinetics constants under different conditions

圖1　不同底物濃度對(duì)環(huán)氧蟲(chóng)啶直接光降解的影響Fig.1　Effect of initial concentration on direct photolysis of CYC in Milli-Q water

式中:k是反應(yīng)速率常數(shù),min-1;T是絕對(duì)溫度,K.

環(huán)氧蟲(chóng)啶的反應(yīng)活化能為21.27KJ/mol.溫度影響環(huán)氧蟲(chóng)啶的光降解,因而在考察其他因素的影響時(shí),實(shí)驗(yàn)溫度嚴(yán)格控制為25℃.

圖2　溫度對(duì)環(huán)氧蟲(chóng)啶直接光降解的影響Fig.2　Effect of temperature on direct photolysis of CYC in Milli-Q water

2.1.3 pH值對(duì)環(huán)氧蟲(chóng)啶光降解的影響 很多研究表明,溶液的pH值能夠顯著影響有機(jī)化合物的光降解[10].Bagal等[15]研究表明pH值降低2,4-二硝基苯酚的光降解速率變慢,這是由于低pH值下,2,4-二硝基苯酚為中性粒子,比陰離子狀態(tài)對(duì)光敏感.Zhou等[16]研究對(duì)氨基苯甲酸的光解,發(fā)現(xiàn)對(duì)氨基苯甲酸的光降解速率隨著pH值的增大而加快.Benitez等[17]發(fā)現(xiàn)高pH值環(huán)境抑制苯并三唑和N,N-二乙基間甲苯甲酰胺的光降解.

初始濃度為5×10-5mol/L的環(huán)氧蟲(chóng)啶在不同pH條件下的光降解情況如圖3和表1所示.pH 3.00,4.76,7.63,9.20,10.05條件下對(duì)應(yīng)的環(huán)氧蟲(chóng)啶光降解速率常數(shù)分別為1.0622,0.0931,0.0911, 0.0501,0.0391min-1.可見(jiàn),pH值對(duì)水中環(huán)氧蟲(chóng)啶的光降解具有非常重要的影響,隨著pH值的增加,環(huán)氧蟲(chóng)啶的光降解變慢.通過(guò)Sirius T3理化常數(shù)測(cè)定儀測(cè)得環(huán)氧蟲(chóng)啶的pKa值為3.42,因此,水溶液中,環(huán)氧蟲(chóng)啶存在中性分子和陽(yáng)離子兩種狀態(tài).pH<7時(shí),隨pH值降低,環(huán)氧蟲(chóng)啶在溶液中陽(yáng)離子含量增加;pH>7時(shí),溶液中環(huán)氧蟲(chóng)啶以中性分子形式存在.基于以上結(jié)果,猜測(cè)環(huán)氧蟲(chóng)啶的陽(yáng)離子光反應(yīng)活性高于環(huán)氧蟲(chóng)啶中性分子.Zhou 等[16]利用DFT計(jì)算出對(duì)氨基苯甲酸的各粒子形態(tài)的單線(xiàn)態(tài)能量值,發(fā)現(xiàn)其光降解反應(yīng)速率與該值有關(guān).單線(xiàn)態(tài)能量值越小,粒子越易發(fā)生光反應(yīng),即光降解速率越快.為驗(yàn)證猜想,我們也利用Gaussian 03計(jì)算環(huán)氧蟲(chóng)啶不同粒子的LOMOHOMO值.如圖4所示,環(huán)氧蟲(chóng)啶存在兩種不同的構(gòu)型,左圖為它們的中性分子狀態(tài),右圖為陽(yáng)離子, 在(a)構(gòu)型下的陽(yáng)離子LOMO-HOMO值為3.89eV,中性分子為4.50eV;環(huán)氧蟲(chóng)啶在(b)構(gòu)型下的陽(yáng)離子為3.95eV,中性分子為4.64eV.比較兩種構(gòu)型中陽(yáng)離子和中性分子的LOMO-HOMO值,可知環(huán)氧蟲(chóng)啶的陽(yáng)離子均比中性分子所需活化能低.環(huán)氧蟲(chóng)啶的陽(yáng)離子更易發(fā)生光降解反應(yīng),當(dāng)溶液中環(huán)氧蟲(chóng)啶陽(yáng)離子的含量增多時(shí),光降解速率加快.以上結(jié)論合理地解釋了環(huán)氧蟲(chóng)啶處于酸性環(huán)境中光降解比堿性環(huán)境中快的現(xiàn)象.

圖3　pH值對(duì)環(huán)氧蟲(chóng)啶光降解的影響Fig.3　Effect of initial pH value on the photodegradation of cycloxaprid

堿性條件下,溶液中的環(huán)氧蟲(chóng)啶以中性分子形式存在,其含量不再隨pH值變化而改變.而由表1可知,pH 7.63,9.20,10.05條件下對(duì)應(yīng)的環(huán)氧蟲(chóng)啶光降解半衰期存在差異,分別為7.61,13.84, 17.73min.因此,堿性條件下,環(huán)氧蟲(chóng)啶的光降解速率隨著pH增加而變慢的現(xiàn)象與環(huán)氧蟲(chóng)啶本身性質(zhì)無(wú)關(guān).可能是由于: a)高pH值環(huán)境下,堿性降解產(chǎn)物的累積抑制光降解過(guò)程; b)隨著pH值的增加,羥基自由基的氧化性降低[18]; c)堿性條件下,羥基自由基迅速消亡[19].Xu等[19]研究鄰苯二甲酸二甲酯的光降解,發(fā)現(xiàn)堿性溶液中羥基自由基的含量降低導(dǎo)致鄰苯二甲酸二甲酯的光降解變慢,如式(2)、(3)所示.

圖4　兩種構(gòu)型的環(huán)氧蟲(chóng)啶的陽(yáng)離子和中性分子結(jié)構(gòu)Fig.4　The cations and neutral particles of two configuration for cycloxaprid

猜測(cè)在堿性條件下,環(huán)氧蟲(chóng)啶的光降解速率與溶液中羥基自由基的含量有關(guān).為驗(yàn)證猜測(cè),進(jìn)一步設(shè)計(jì)實(shí)驗(yàn),在不同pH值的環(huán)氧蟲(chóng)啶溶液中加入1%叔丁醇作為羥基自由基捕獲劑.結(jié)果表明pH為3.00時(shí),加入叔丁醇并未對(duì)環(huán)氧蟲(chóng)啶的光降解產(chǎn)生明顯影響.然而pH9.20時(shí),叔丁醇的加入使得環(huán)氧蟲(chóng)啶的光解速率僅為原先的55.29%.叔丁醇顯著減弱該條件下環(huán)氧蟲(chóng)啶的光降解.因此,在堿性條件下,羥基自由基是環(huán)氧蟲(chóng)啶光降解的主要因素.

結(jié)合圖表的數(shù)據(jù)及結(jié)論,發(fā)現(xiàn)環(huán)氧蟲(chóng)啶光降解與兩個(gè)因素有關(guān):一是環(huán)氧蟲(chóng)啶本身的性質(zhì),二是溶液中羥基自由基的含量.當(dāng)pH<7時(shí),環(huán)氧蟲(chóng)啶本身的性質(zhì)決定了光降解速率,羥基自由基對(duì)環(huán)氧蟲(chóng)啶光降解反應(yīng)的貢獻(xiàn)小;當(dāng)pH>7時(shí),溶液中羥基自由基的含量成為決定性因素.

2.2 環(huán)氧蟲(chóng)啶的間接光降解

2.2.1 過(guò)氧化氫對(duì)環(huán)氧蟲(chóng)啶光降解的影響 許多研究表明,高濃度的過(guò)氧化氫對(duì)于化合物的光降解具有促進(jìn)作用[20].然而,也有研究表明,光降解速率并不隨過(guò)氧化氫濃度的增加一直增加,對(duì)于不同的化合物,存在最適宜的過(guò)氧化氫濃度[25].為確定過(guò)氧化氫對(duì)環(huán)氧蟲(chóng)啶光降解的影響,實(shí)驗(yàn)研究了過(guò)氧化氫濃度為2×10-3mol/L, 5× 10-3mol/L,1×10-2mol/L和1.5×10-2mol/L時(shí)環(huán)氧蟲(chóng)啶的光降解情況.由圖5和表1可以看出,過(guò)氧化氫的濃度從0mol/L增加到1×10-2mol/L時(shí),環(huán)氧蟲(chóng)啶的光降解速率也隨之增加;然而當(dāng)過(guò)氧化氫的濃度增至1.5×10-2mol/L時(shí),相比于1× 10-2mol/L,降解速率反而減小.

圖5　過(guò)氧化氫對(duì)環(huán)氧蟲(chóng)啶光降解的影響Fig.5　Effect of initial H2O2 concentration on the photodegradation of cycloxaprid

2×10-3mol/L濃度的H2O2條件下,環(huán)氧蟲(chóng)啶光降解速率常數(shù)是超純水中光降解速率的2.93 倍. 5×10-3mol/L,1×10-2mol/L和1.5×10-2mol/L濃度的過(guò)氧化氫條件下,環(huán)氧蟲(chóng)啶的光降解速率常數(shù)依次變?yōu)樵瓉?lái)的5.13,7.71和4.89倍.數(shù)據(jù)顯示,過(guò)氧化氫具有明顯的加速作用.這主要是因?yàn)榈蜐舛鹊倪^(guò)氧化氫在光照下會(huì)生成羥基自由基,加速光降解的進(jìn)行,如下式[27]:

但過(guò)氧化氫加速光降解反應(yīng)存在最優(yōu)化濃度,過(guò)氧化氫濃度為1.5×10-2mol/L的降解速率常數(shù)比1×10-2mol/L時(shí)的降解速率常數(shù)降低36.56%.這主要是由于隨著過(guò)氧化氫濃度的增加,溶液中未被光照激發(fā)成羥基自由基的過(guò)氧化氫會(huì)與生成的羥基自由基反應(yīng),反而降低了溶液中羥基自由基的含量,可由式(5)～(7)表述[28].

2.2.2 硝酸根對(duì)環(huán)氧蟲(chóng)啶光降解的影響 硝酸根離子普遍存在于自然水體中,其濃度因地理位置的差異而略有不同,水環(huán)境濃度一般為1× 10-5～1×10-3mol/L[29].硝酸根在光照下產(chǎn)生成·NO2和·OH等活性自由基,從而促進(jìn)化合物的間接光降解[30],如(8)～(9)所示[33]:

圖6和表1顯示,硝酸根濃度為0,1×10-4,1× 10-3和2×10-3mol/L時(shí),環(huán)氧蟲(chóng)啶光降解的半衰期分別為7.61,7.18,6.29,5.41min,半衰期隨著硝酸根濃度的增加而縮短.這是由于光敏態(tài)的NO3-促進(jìn)羥基自由基的產(chǎn)生,從而加快環(huán)氧蟲(chóng)啶的光降解.然而,相對(duì)于不加硝酸根,加入2×10-3mol/L硝酸根,環(huán)氧蟲(chóng)啶的光降解半衰期只縮短了28.9%.說(shuō)明,相對(duì)于環(huán)氧蟲(chóng)啶在水環(huán)境中的直接光降解,硝酸根對(duì)環(huán)氧蟲(chóng)啶的間接光降解作用為次要的.光敏劑硝酸根的存在并不能顯著影響水環(huán)境中環(huán)氧蟲(chóng)啶的光降解行為.

圖6　硝酸根對(duì)環(huán)氧蟲(chóng)啶光降解的影響Fig.6　Effect of initial nitrate concentration on the photodegradation of cycloxaprid

3　結(jié)論

3.1 環(huán)氧蟲(chóng)啶的光降解反應(yīng)可用一級(jí)動(dòng)力學(xué)方程模擬.環(huán)氧蟲(chóng)啶初始濃度增加,光降解速率常數(shù)k減小;溫度對(duì)環(huán)氧蟲(chóng)啶光降解有促進(jìn)作用,溫度升高,環(huán)氧蟲(chóng)啶光降解加快,環(huán)氧蟲(chóng)啶的反應(yīng)活化能(Ea)為21.27kJ/mol.

3.2 溶液pH值影響環(huán)氧蟲(chóng)啶的光降解速率.通過(guò)測(cè)定環(huán)氧蟲(chóng)啶的pKa值為3.42,確定環(huán)氧蟲(chóng)啶在不同pH值溶液中的主要存在形式.當(dāng)pH值小于7時(shí),隨著pH值的減小,環(huán)氧蟲(chóng)啶在水溶液中的陽(yáng)離子含量增多.通過(guò)高斯計(jì)算,確定了環(huán)氧蟲(chóng)啶陽(yáng)離子的光反應(yīng)活性高于中性分子.在酸性環(huán)境下,環(huán)氧蟲(chóng)啶的光降解由環(huán)氧蟲(chóng)啶本身性質(zhì)即在水中陽(yáng)離子的含量決定;當(dāng)pH值大于7時(shí),環(huán)氧蟲(chóng)啶在水溶液中以中性分子形式存在,羥基自由基對(duì)環(huán)氧蟲(chóng)啶的光降解起決定性作用.

3.3 過(guò)氧化氫加快環(huán)氧蟲(chóng)啶的光降解速率,但是光降解速率并不隨過(guò)氧化氫濃度增加而一直增加,存在最適宜濃度;硝酸根也能促進(jìn)環(huán)氧蟲(chóng)啶的光降解,但促進(jìn)作用相對(duì)較弱.

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Photodegradation of cis-configuration neonicotinoid cycloxaprid in water.

DENG Ya-yun1, ZHUANG Ying-ying1, FENG Yue1, LU Si-yuan1, CHENG Jia-gao1, XU Xiao-yong1,2*(1.Shanghai Key Lab of Chemistry Biology, Institute of Pesticides and Pharmaceuticals, East China University of Science and Technology, Shanghai 200237, China；2.Shanghai Collaborative Innovation Center for Biomanufacturing Technology, Shanghai 200237, China). China Environmental Science, 2016,36(4)：1112～1118

Abstract：In order to correctly evaluate the environmental risk of the new insecticide CYC, the influence of the CYC initial concentration, temperature, initial pH, concentration of hydrogen peroxide and nitrate on the CYC photodegradation in water were studied. The results show that the photodegradation of cycloxaprid was fitted to pseudo-first-order kinetics reaction. For direct photodegradation, cycloxaprid photolysis rate was accelerated with the decreasing of CYC concentration and the increase of temperature. The activation energy of photochemical reaction was 21.27kJ/mol. By measuring the CYC pKa value of 3.42 and simulation CYC reactivity of different forms of light particles, known the complicated influence of pH value on CYC photolysis: In the acidic conditions, the degradation rate of cycloxaprid depended on the different cycloxaprid forms (cations and neutral particles) and their singlet energy values. While, in the alkaline condition, the photodegradation rate was mainly affected by the number of hydroxyl radicals in the solution. For CYC indirect photodegradation, nitrate and hydrogen peroxide were confirmed to promote the role. When evaluating the environmental risk of CYC should comprehensively consider the effect of environmental factors on its degradation.

Key words：insecticide；cycloxaprid；photodegradation；hydroxyl radical；HOMO-LUMO gap

作者簡(jiǎn)介：鄧亞運(yùn)(1990-),女,湖北咸寧人,華東理工大學(xué)藥學(xué)院碩士研究生,主要從事新煙堿類(lèi)殺蟲(chóng)劑環(huán)境光化學(xué)行為研究.

基金項(xiàng)目：國(guó)家”863”項(xiàng)目(2011AA10A207,2013AA065202);國(guó)家自然科學(xué)基金(21272071);公益性行業(yè)(農(nóng)業(yè))科研專(zhuān)項(xiàng)經(jīng)費(fèi)(201103007)

收稿日期：2015-09-12

中圖分類(lèi)號(hào)：X703

文獻(xiàn)標(biāo)識(shí)碼：A

文章編號(hào)：1000-6923(2016)04-1112-07