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)

?

順硝烯新煙堿殺蟲劑環(huán)氧蟲啶在水中的光降解

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)估新型殺蟲劑環(huán)氧蟲啶(CYC)的環(huán)境風(fēng)險(xiǎn),了解環(huán)氧蟲啶在水環(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)氧蟲啶的反應(yīng)活化能為21.27kJ/mol.通過測(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)(陽離子和中性粒子)與單線態(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：新煙堿類殺蟲劑；環(huán)氧蟲啶；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,新煙堿類殺蟲劑被認(rèn)為是農(nóng)業(yè)領(lǐng)域的里程碑[1].是自擬除蟲菊酯商業(yè)化后銷售量增長(zhǎng)最快的一類農(nóng)藥,其全球銷量占整個(gè)殺蟲劑市場(chǎng)的24%,約為26.32億美元[2].至今為止,已經(jīng)商業(yè)化的新煙堿類殺蟲劑包括吡蟲啉、噻蟲啉等.當(dāng)殺蟲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、水解及光解過程,在這些變化過程中往往會(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)新煙堿殺蟲劑光降解研究已有報(bào)道[1,4-5], Pe?a等[6]研究了噻蟲嗪和噻蟲啉在污水、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)吡蟲啉的抗性害蟲具有顯著活性的新煙堿殺蟲劑,環(huán)氧蟲啶(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活性,極有前景進(jìn)入市場(chǎng)成為國際上具有重要影響力的新一類殺蟲劑.因而很有必要進(jìn)行環(huán)氧蟲啶環(huán)境行為的研究,為環(huán)氧蟲啶的進(jìn)一步開發(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)氧蟲啶在淹水無氧土壤中的降解情況.然而關(guān)于環(huán)氧蟲啶在水環(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、過氧化氫及硝酸根等影響因素,以期為評(píng)價(jià)環(huán)氧蟲啶的環(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,購自Merck公司;MilliQ超純水(Milli-pore, 18M?·cm);環(huán)氧蟲啶標(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);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)氧蟲啶小分子的HOMO和LUMO值并計(jì)算軌道差,預(yù)測(cè)環(huán)氧蟲啶不同狀態(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)氧蟲啶的保留時(shí)間為4.39min.

2　結(jié)果與討論

2.1 環(huán)氧蟲啶的直接光降解

2.1.1 濃度對(duì)環(huán)氧蟲啶光降解的影響 從表1和圖1可見,濃度為5×10-5,1×10-4, 2× 10-4mol/L的環(huán)氧蟲啶光降解速率常數(shù)分別為0.0911,0.0578,0.0294min-1,環(huán)氧蟲啶初始濃度增加,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)氧蟲啶在無光照下沒有降解,說明水解或生物降解對(duì)環(huán)氧蟲啶的光降解沒有貢獻(xiàn).

2.1.2 溫度對(duì)環(huán)氧蟲啶光降解的影響 實(shí)驗(yàn)結(jié)果見表1與圖2,表明溫度對(duì)環(huán)氧蟲啶光解有重要影響.15℃,25℃,35℃下,環(huán)氧蟲啶光降解半衰期對(duì)應(yīng)為11.04,7.61,6.21min.15℃時(shí)環(huán)氧蟲啶的光降解速率僅為35℃的56.25%.可見升高環(huán)境溫度,環(huán)氧蟲啶光降解速率常數(shù)增加,反應(yīng)加快.環(huán)氧蟲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)氧蟲啶的反應(yīng)活化能為21.27KJ/mol.溫度影響環(huán)氧蟲啶的光降解,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,pH值對(duì)水中環(huán)氧蟲啶的光降解具有非常重要的影響,隨著pH值的增加,環(huán)氧蟲啶的光降解變慢.通過Sirius T3理化常數(shù)測(cè)定儀測(cè)得環(huán)氧蟲啶的pKa值為3.42,因此,水溶液中,環(huán)氧蟲啶存在中性分子和陽離子兩種狀態(tài).pH<7時(shí),隨pH值降低,環(huán)氧蟲啶在溶液中陽離子含量增加;pH>7時(shí),溶液中環(huán)氧蟲啶以中性分子形式存在.基于以上結(jié)果,猜測(cè)環(huán)氧蟲啶的陽離子光反應(yīng)活性高于環(huán)氧蟲啶中性分子.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)氧蟲啶不同粒子的LOMOHOMO值.如圖4所示,環(huán)氧蟲啶存在兩種不同的構(gòu)型,左圖為它們的中性分子狀態(tài),右圖為陽離子, 在(a)構(gòu)型下的陽離子LOMO-HOMO值為3.89eV,中性分子為4.50eV;環(huán)氧蟲啶在(b)構(gòu)型下的陽離子為3.95eV,中性分子為4.64eV.比較兩種構(gòu)型中陽離子和中性分子的LOMO-HOMO值,可知環(huán)氧蟲啶的陽離子均比中性分子所需活化能低.環(huán)氧蟲啶的陽離子更易發(fā)生光降解反應(yīng),當(dāng)溶液中環(huán)氧蟲啶陽離子的含量增多時(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)氧蟲啶的光降解速率隨著pH增加而變慢的現(xiàn)象與環(huán)氧蟲啶本身性質(zhì)無關(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)氧蟲啶的陽離子和中性分子結(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)氧蟲啶的光降解.因此,在堿性條件下,羥基自由基是環(huán)氧蟲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)氧蟲啶光降解與兩個(gè)因素有關(guān):一是環(huán)氧蟲啶本身的性質(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)氧蟲啶的間接光降解

2.2.1 過氧化氫對(duì)環(huán)氧蟲啶光降解的影響 許多研究表明,高濃度的過氧化氫對(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,存在最適宜的過氧化氫濃度[25].為確定過氧化氫對(duì)環(huán)氧蟲啶光降解的影響,實(shí)驗(yàn)研究了過氧化氫濃度為2×10-3mol/L, 5× 10-3mol/L,1×10-2mol/L和1.5×10-2mol/L時(shí)環(huán)氧蟲啶的光降解情況.由圖5和表1可以看出,過氧化氫的濃度從0mol/L增加到1×10-2mol/L時(shí),環(huán)氧蟲啶的光降解速率也隨之增加;然而當(dāng)過氧化氫的濃度增至1.5×10-2mol/L時(shí),相比于1× 10-2mol/L,降解速率反而減小.

圖5　過氧化氫對(duì)環(huán)氧蟲啶光降解的影響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濃度的過氧化氫條件下,環(huán)氧蟲啶的光降解速率常數(shù)依次變?yōu)樵瓉淼?.13,7.71和4.89倍.數(shù)據(jù)顯示,過氧化氫具有明顯的加速作用.這主要是因?yàn)榈蜐舛鹊倪^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]:

但過氧化氫加速光降解反應(yīng)存在最優(yōu)化濃度,過氧化氫濃度為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)氧蟲啶的光降解半衰期只縮短了28.9%.說明,相對(duì)于環(huán)氧蟲啶在水環(huán)境中的直接光降解,硝酸根對(duì)環(huán)氧蟲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)氧蟲啶的光降解行為.

圖6　硝酸根對(duì)環(huán)氧蟲啶光降解的影響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)氧蟲啶光降解有促進(jìn)作用,溫度升高,環(huán)氧蟲啶光降解加快,環(huán)氧蟲啶的反應(yīng)活化能(Ea)為21.27kJ/mol.

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

3.3 過氧化氫加快環(huán)氧蟲啶的光降解速率,但是光降解速率并不隨過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)氧蟲啶的光降解,但促進(jìn)作用相對(duì)較弱.

參考文獻(xiàn)：

[1] ?ernigoj U, ?tangar U L, Treb?e P. Degradation of neonicoticotinoid insecticides by different advanced oxidation processes and studying the effect of ozone on Ti O2photocatalysis [J]. Appl. Catal. B: Environ., 2007,75(3/4):229-238.

[2] Nauen R, Bretschneider T. New modes of action of insecticides [J]. Pestic. Outlook, 2002,13:241-245.

[3] Jeschke P, Nauen R, Schindler M, et al. Overview of the status and global strategy for noenicotinoids [J]. J. Agric. Food Chem. 2011,59(7):2897-2908.

[4] Dell’ Arciprete M L, Santos-Juanes L, Sanz A A, et al. Reactivity of hydroxyl radicals with neonicotinoid insecticedes: mechanism and changes in toxicity [J]. Photochem. Photobiol. Sci., 2009,8: 1016-1023.

[5] Wamhoff H, Schneider V. Photodegradation of imidacloprid [J]. J. Agric. Food Chem. 1999,47(4):1730–1734.

[6] Pe?a A, Rodríguez-Liébana J A, Mingorance M D. Persistence of two neonicotinoid insecticides in wastewater, and in aqueous solutions of surfactants and dissolved organic matter [J]. Chemosphere, 2011,84(4):464-470.

[7] Shao X S, Fu H, Xu X Y, et al. Divalent and oxabridged neonicotinoids constructed by dialdehydes and nitromethylene analogues of imidacloprid: Design, Synthesis, Crystal structure, and Insecticidal Activities [J]. J. Agric. Food Chem., 2010,58(5): 2696-2702.

[8] Liu X Q, Xu X Y, Li C, et al. Degradation of chiral neonicotinoid insecticide cycloxaprid in flooded and anoxic soil [J]. Chemosphere. 2015,119:334-341.

[9] Orellana-García F, álvarez M A, López-Ramón V, et al. Photodegradation of herbicides with different chemical natures in aqueous solution by ultraviolet radiation. Effects of operational variables and solution chemistry [J]. Chem. Eng. J. 2014,255: 307-315.

[10] Kim M K, Zoh K D. Effects of natural water constituents on the photo-decomposition of methylmercury and the role of hydroxyl radical [J]. Sci. Total Environ., 2013,449:95-101.

[11] Shephard G S, Stockenstr?m S, de Villiers D, et al. Degradation of microcystin toxins in a falling film photocatalytic reactor with immobilizied titanium dioxide catalyst [J]. Water Res., 2002,36(1): 140-146.

[12] Vione D, Maurino V, Minero C, et al. Phenol photonitration upon UV irradiation of nitrite in aqueous solution II: effects of pH and TiO2[J]. Chemosphere, 2001,45(6/7):903-910.

[13] Xu D X, Yuan F, Gao Y X, et al. Influence of pH, metal chelator, free radical scavenger and interfacial characteristics on the oxidative stability of β-carotene in conjugated whey proteinpectin stabilized emulsion [J]. Food chem., 2013,139(1-4):1098-1104.

[14] 陽 海,周碩林,尹明亮,等.克百威光催化降解動(dòng)力學(xué)的研究[J]. 中國環(huán)境科學(xué), 2013,33(1):82-87.

[15] Bagal M V, Gogate P R. Degradation of 2, 4-dinitrophenol using a combination of hydrodynamic cavitation, chemical and advanced oxidation processes [J]. Ultrason. Sonochem., 2013, 20(5):1226-1235.

[16] Zhou L, Ji YF, Zeng C, et al. Aquatic photodegradation of sunscreen agent p-aminobenzoic acid in the presence of dissolved organic matter [J]. Water Res., 2013,47(1):153-162.

[17] Benitez F J, Acero J L, Real F J, et al. Photolysis of model emerging contaminants in ultra-pure water: kinerics, by-products formation and degradation pahyways [J]. Water Res., 2013,47(2): 870-880.

[18] Buxton G V, Greenstock C L, Helman W P, et al. Critical review of rate constants for reactions of hydrated eleutrons, hydrogen atoms and hydroxyl radicals (·OH/·O-) in aqueous solution [J]. J. Phys. Chem. Ref. Data., 1988,17(2):513-886.

[19] Xu L J, Chu W, Graham N. Sonophotolytic degradation of dimethyl phthalate without catalyst: Analysis of the synergistic effect and modeling [J]. Water. Res., 2013,47(6):1996-2004.

[20] Abdullah F H, Rauf M A, Ashraf S S. Photolytic oxidation of Safranin-O with H2O2[J]. Dyes. Pigm., 2007,72(3):349-352.

[21] Devi L G, Kumar S G, Reddy K M, et al. Photodegradation of methyl orange an azo dye by advanced Fenton process using zero valent metallic iron: influence of various reaction parameters and its degradation mechanism [J]. J. Hazard. Mater., 2009,164(2/3):459-467.

[22] dos Santos W N L, Brand?o G C, Portugal L A, et al. A photo-oxidation procedure using UV radation/H2O2for decomposition of wine samples-Determination of iron and manganese content by flame atomic absorption spectrometry [J]. Spectrochim. Acta, Part B. 2009,64(6):601-604.

[23] Poulopoulos S G, Arvantitakis F, Philippopolos C J. Photochemical treatment of phenol aqueous solutions using ultraviolet radiation and hydrogen peroxide [J]. J. Hazard. Mater., 2006,129(1-3):64-68.

[24] 馬曉雁,倪夢(mèng)婷,倪永炯,等.UV體系中3種微量類固醇雌激素的競(jìng)爭(zhēng)降解及同趨轉(zhuǎn)化 [J]. 中國環(huán)境科學(xué), 2014,34(4):904-911. [25] Aleboyeh A, Moussa Y, Aleboyeh H. Kinetics of oxidative decolourisation of Acid Orange 7in water by ultraviolet radiation in the presence of hydrogen peroxide [J]. Sep. Purif. Technol., 2005,43(2):143-148.

[26] Sarla M, Pandit M, Tyagi D K, et al. Oxidation of cyanide in aqueous solution by chemical and photochemical process [J]. J. Hazard. Mater., 2004,116(1/2):49-56.

[27] Evgenidou E, Konstantinou I, Fytianos K, et al. Oxidation of two organophosphorous insecticides by the photo-assisted Fenton reaction [J]. Water Res., 2007,41(9):2015-2027.

[28] El-Sheikh M A, Ramadan M A, El-Shafie A. Photo-oxidation of rice starch. Part I: Using hydrogen peroxide [J]. Carbohydr. Polym., 2010,80(1):266-269.

[29] Zuo Y G, Wang C J, Van T. Simultaneous determination of nitrite and nitrate in dew, rain, snow and lake water samples by ion-pair high-performance liquid chromatography [J]. Talanta, 2006, 70(2):281-285.

[30] Zepp R G, Hoigne J, Bader H. Nitrate-induced photooxidation of trace organic chemicals in water [J]. Environ. Sci. Technol., 1987, 21(5):443-450.

[31] Brezonik P L, Fulkerson-Brekken J. Nitrate-induced photolysis in natural waters: controls on concentrations of hydroxyl radical photo-intermediate by natural scavenging agents [J]. Environ. Sci. Technol., 1998,32(19):3004-3010.

[32] 展漫軍,楊 曦,鮮啟鳴,等.雙酚A在硝酸根溶液中的光解研究[J]. 中國環(huán)境科學(xué), 2005,25(4):487-490.

[33] Warneck P, Wurzinger C. Product quantum yields for the 305-nm photodegradation of nitrate in aqueous solution [J]. J. Phys. Chem., 1988,92(22):6278-6283.

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,主要從事新煙堿類殺蟲劑環(huán)境光化學(xué)行為研究.

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

收稿日期：2015-09-12

中圖分類號(hào)：X703

文獻(xiàn)標(biāo)識(shí)碼：A

文章編號(hào)：1000-6923(2016)04-1112-07