薛南冬，劉寒冰，楊兵，蘇獻(xiàn)偉，王冬琦

毒死蜱（chlorpyrifos），化學(xué)名稱(chēng)O，O-二乙基-O-（3，5，6-三氯-2-吡啶基）硫代磷酸酯，是一種廣譜、高效有機(jī)磷殺蟲(chóng)劑。毒死蜱通過(guò)抑制乙酰膽堿酯酶的活性影響神經(jīng)系統(tǒng)，導(dǎo)致生物死亡[1]，因此，對(duì)非靶標(biāo)生物甚至人類(lèi)存在潛在毒性[2-3]。調(diào)查顯示，施用的毒死蜱只有不到1%能作用于靶標(biāo)生物[4]，大部分將進(jìn)入大氣、土壤、水體環(huán)境[5-8]。土壤是毒死蜱在環(huán)境中的主要?dú)w宿，毒死蜱在土壤環(huán)境中的殘留可能帶來(lái)潛在生態(tài)風(fēng)險(xiǎn)[9-10]。毒死蜱在土壤介質(zhì)中的環(huán)境影響和環(huán)境行為日益受到關(guān)注[11-13]，本文綜述了毒死蜱在土壤環(huán)境中的賦存和歸趨的研究進(jìn)展。

1 毒死蜱在土壤環(huán)境中的賦存

近年來(lái)，毒死蜱的廣泛應(yīng)用，導(dǎo)致在許多國(guó)家和地區(qū)的土壤、河流、地下水、城市污水系統(tǒng)、雨水、空氣等環(huán)境中均檢測(cè)到其殘留。在一些國(guó)家，毒死蜱是環(huán)境中殘留檢出頻率最高的農(nóng)藥品種之一[14]，甚至在農(nóng)作物中也檢測(cè)到其殘留[15]。在對(duì)水稻、玉米和大豆3種農(nóng)產(chǎn)品共計(jì)144個(gè)樣品的調(diào)查中發(fā)現(xiàn)，毒死蜱的檢出率分別為64.6%、18.8%和2.08%，在谷物類(lèi)農(nóng)產(chǎn)品中的檢出率較高[16]。

曾阿瑩等[17]對(duì)中國(guó)福州某蔬菜基地43個(gè)土壤樣品有機(jī)磷類(lèi)農(nóng)藥殘留的檢測(cè)結(jié)果顯示，毒死蜱的最大殘留量為9.77 mg/kg，其檢出率高達(dá)97.7%。調(diào)查發(fā)現(xiàn)，在美洲附近的海洋沉積物[18]，甚至在北極圈土壤樣品中都有毒死蜱的檢出[14]。

1.1 毒死蜱在土壤環(huán)境中的半衰期

在土壤環(huán)境中，毒死蜱經(jīng)物理、化學(xué)和生物作用不斷消解，其消解速度與土壤pH值和環(huán)境溫度有關(guān)[19-20]。在堿性土壤中，溫度越低，毒死蜱半衰期越長(zhǎng)；在同一溫度下，堿性土壤中毒死蜱半衰期較短，說(shuō)明堿性土壤可能有利于毒死蜱的降解[21]。在不同土壤pH值和溫度條件下毒死蜱的半衰期如表1所示。除此之外，土壤中毒死蜱的消解還與農(nóng)作物的種類(lèi)有關(guān)[22]。在種植蕹菜（Ipomoea aquatica Forsk.）的土壤中毒死蜱半衰期為25 d，在水稻田土壤中毒死蜱半衰期為6.7～16 d[23]。ZHANG等[24]報(bào)道了毒死蜱在春季種植卷心菜（Brassica oleracea L.var.capitata）和秋季種植小白菜（Brassica chinensis L.）土壤中的半衰期分別是2.0和4.7 d。不同作物類(lèi)型對(duì)毒死蜱半衰期的影響可能與其根系分泌物對(duì)土壤微環(huán)境的影響有關(guān)，因此，研究不同類(lèi)型作物，特別是其根際微環(huán)境對(duì)毒死蜱的消解機(jī)制，對(duì)探明毒死蜱在土壤中的遷移轉(zhuǎn)化驅(qū)動(dòng)機(jī)制具有重要意義。

表1 不同環(huán)境條件下土壤中毒死蜱的半衰期Table 1 Chlorpyrifos half-life in soils under different environment conditions

1.2 毒死蜱在土壤環(huán)境中的歸趨

土壤是毒死蜱在農(nóng)田系統(tǒng)中遷移轉(zhuǎn)化的主要源和匯，毒死蜱在土壤中的環(huán)境行為，不僅與毒死蜱自身物理化學(xué)性質(zhì)有關(guān)，也與土壤特點(diǎn)有關(guān)。毒死蜱與土壤顆粒、植物及沉積物產(chǎn)生不同作用，通過(guò)揮發(fā)、吸附解吸、非生物降解和生物降解等途徑在土壤環(huán)境中實(shí)現(xiàn)遷移轉(zhuǎn)化[28]，如圖1所示。

2 毒死蜱在土壤中的吸附/解吸

2.1 吸附/解吸模型

毒死蜱通過(guò)土壤顆粒的吸附作用，一方面降低了在土壤中的生物活性和遷移性，另一方面增加了農(nóng)藥在土壤中的殘留。毒死蜱在土壤中的吸附/解吸行為通常用弗倫德利希（Freundlich）吸附模型和線性吸附模型擬合[29-33]。

Freundlich 吸附模型：Qe=Kf×Ce1/n；線性吸附模型：Qe=Kd×Ce。其中：Qe為平衡時(shí)的吸附量；Ce為平衡時(shí)的濃度；Kf、Kd為吸附平衡常數(shù)；n為吸附過(guò)程中支持力的經(jīng)驗(yàn)常數(shù)。

Kf（Kd）是定量判斷毒死蜱在環(huán)境中遷移能力的重要因子。Kf（Kd）值越大，土壤對(duì)毒死蜱的吸附固定能力越強(qiáng)，毒死蜱在土壤環(huán)境中遷移能力較弱；Kf（Kd）值越小，毒死蜱在土壤中的遷移能力越大。在不同土壤環(huán)境中毒死蜱Kf（Kd）值的變化，說(shuō)明不同土壤性質(zhì)對(duì)毒死蜱的吸附解吸能力產(chǎn)生了不同程度的影響。研究表明，毒死蜱在土壤中的吸附行為符合疏水有機(jī)物吸附理論：在低濃度下，毒死蜱在土壤中的吸附行為符合線性吸附模型，在高濃度下符合Freundlich吸附模型[28]。

2.2 毒死蜱在土壤中的吸附/解吸

自20世紀(jì)70年代以來(lái)，研究者針對(duì)數(shù)十種不同區(qū)域、不同用途的土壤（pH 4.8～8.9，有機(jī)質(zhì)0.31%～75%）對(duì)毒死蜱的吸附行為開(kāi)展了研究[34-36]。毒死蜱在不同類(lèi)型土壤中的吸附/解吸特征見(jiàn)表2和表3。

對(duì)毒死蜱在土壤中的吸附/解吸研究分別采用Freundlich吸附模型和線性吸附模型。對(duì)于同一地區(qū)的土壤，其有機(jī)質(zhì)含量越高，吸附模型常數(shù)Kd（Kf）越大，如美國(guó)愛(ài)荷華州土壤有機(jī)質(zhì)從0.88%升高到4.56%，Kf從28.4升高到162；然而不同地區(qū)由于區(qū)域環(huán)境條件不同，即使土壤理化性質(zhì)相似，Kd（Kf）也可能產(chǎn)生較大差異，如荷蘭砂質(zhì)土對(duì)毒死蜱的Kd為110，而希臘砂質(zhì)土對(duì)毒死蜱的Kd為17。對(duì)比研究結(jié)果說(shuō)明，毒死蜱在土壤中的吸附/解吸行為的時(shí)空變化與土壤性質(zhì)顯著相關(guān)，進(jìn)一步研究各個(gè)因素對(duì)其吸附解吸驅(qū)動(dòng)影響對(duì)掌握毒死蜱的環(huán)境行為規(guī)律具有重要意義。

2.3 吸附/解吸的影響因素

2.3.1 土壤有機(jī)質(zhì)

土壤有機(jī)質(zhì)含量是影響土壤對(duì)毒死蜱吸附解吸的重要因素，一般采用土壤有機(jī)碳-水分離常數(shù)（Koc）作為量化因子，計(jì)算土壤中有機(jī)質(zhì)對(duì)毒死蜱的吸附能力大小[37-38]。

Kd=Koc×Foc，其中Foc為土壤有機(jī)質(zhì)含量。

從表2中可以看出，在不同地域、不同類(lèi)型土壤中，毒死蜱的吸附能力都不相同。毒死蜱在土壤中的吸附行為不僅與自身理化性質(zhì)有關(guān)，而且與土壤環(huán)境條件有關(guān)[20]；土壤對(duì)毒死蜱的吸附平衡常數(shù)與有機(jī)質(zhì)含量呈顯著正相關(guān)（圖2），有機(jī)質(zhì)含量越高，吸附常數(shù)值越大。

圖1 毒死蜱在土壤環(huán)境中的遷移轉(zhuǎn)化Fig.1 Migration and transformation of chlorpyrifos in soil environment

圖2 有機(jī)質(zhì)含量與Kd值關(guān)系圖(n=47)Fig.2 Relationship between organic matter content and Kd

在含較低有機(jī)質(zhì)（質(zhì)量分?jǐn)?shù)為1.35%）的土壤（日本）中，毒死蜱的吸附常數(shù)值僅為13.4，而在含較高有機(jī)質(zhì)（質(zhì)量分?jǐn)?shù)為3.41%）的土壤（美國(guó)俄亥俄州）中，毒死蜱的吸附常數(shù)達(dá)1 036（表2）?？梢?jiàn)，土壤有機(jī)質(zhì)含量較高時(shí)可以吸附土壤水中大部分毒死蜱[34]，從而有效降低毒死蜱的施用給土壤帶來(lái)的潛在生態(tài)威脅[36,39]。土壤有機(jī)質(zhì)包括水溶性和非水溶性有機(jī)質(zhì)2大類(lèi)。雖然有機(jī)質(zhì)類(lèi)型對(duì)土壤吸附能力的影響差異不顯著[40]，但是當(dāng)土壤含水率較高

時(shí)，毒死蜱能夠與土壤中的水溶性有機(jī)質(zhì)發(fā)生相互作用，進(jìn)入土壤液相介質(zhì)中[50]。普遍認(rèn)為毒死蜱在土壤中的吸附是土壤有機(jī)質(zhì)與液相部分相互競(jìng)爭(zhēng)作用的結(jié)果，土壤有機(jī)質(zhì)對(duì)毒死蜱的吸附作用減少了其在地下水中的遷移能力[51]。另外，共存有機(jī)物對(duì)毒死蜱在沉積物上的吸附也有影響，十二烷基硫酸鈉能明顯降低吸附量，而非離子型表面活性劑則能增加吸附量[52]。這一現(xiàn)象說(shuō)明土壤對(duì)毒死蜱的吸附主要是通過(guò)土壤顆粒中的疏水性位點(diǎn)對(duì)毒死蜱的物理吸附作用[53]。

表2 不同土壤對(duì)毒死蜱的吸附特征Table 2 Adsorption characteristics of chlorpyrifos in various kinds of soils

毒死蜱在土壤顆粒的解吸過(guò)程也與土壤有機(jī)質(zhì)含量顯著相關(guān)，土壤有機(jī)質(zhì)含量越高，解吸常數(shù)越大，解吸量越少[54]。毒死蜱在土壤顆粒上的解吸過(guò)程是與表面吸附位點(diǎn)相關(guān)的物理解吸過(guò)程，與表面化學(xué)性質(zhì)無(wú)關(guān)。研究表明，被吸附的毒死蜱難以全部解吸，且解吸常數(shù)隨著解吸次數(shù)的增多而增大[55]。對(duì)于有機(jī)質(zhì)含量不同的土壤，毒死蜱在土壤顆粒中的解吸量均小于吸附量，使得毒死蜱在土壤中的遷移能力降低。

表3 不同類(lèi)型土壤對(duì)毒死蜱的解吸特征Table 3 Desorption characteristics of chlorpyrifos in various kinds of soils

2.3.2 土壤pH及土壤黏粒組分

土壤pH對(duì)毒死蜱Kd變化有影響，其關(guān)系如圖3A所示。對(duì)于大多數(shù)土壤而言，pH值在4～9之間，對(duì)Kd值變化影響不大；對(duì)少數(shù)土壤而言，pH值越大，Kd值越小，說(shuō)明酸性土壤在一定程度上有利于土壤對(duì)毒死蜱的吸附。這可能是因?yàn)橥寥纏H一方面會(huì)影響毒死蜱這類(lèi)非離子型化合物的氫鍵作用，另一方面pH還能改變土壤顆粒表面官能團(tuán)的存在狀態(tài)，從而影響土壤對(duì)毒死蜱的吸附[39]。此外，土壤黏粒組分對(duì)Kd值變化也有一定影響（圖3B）。黏土與壤土和砂土相比具有較大的比表面積，解吸能力較弱，使得毒死蜱在黏土中較不易遷移[43,56]。黏粒組分占比越高，Kd值越小，可能是因?yàn)槠渲械牡V物含量高，有機(jī)質(zhì)含量少，導(dǎo)致土壤對(duì)毒死蜱吸附能力降低。

圖3 土壤pH(A)、土壤黏粒含量(B)與Kd的關(guān)系圖(n=47)Fig.3 Relationship between soil pH(A),clay fraction(B)and Kd

土壤理化性質(zhì)對(duì)毒死蜱吸附/解吸的影響并不是單一的，而是多因素的共同作用。將土壤有機(jī)質(zhì)含量、pH與吸附常數(shù)Kf（Kd）進(jìn)行數(shù)理統(tǒng)計(jì)，發(fā)現(xiàn)Kf（Kd）與有機(jī)質(zhì)含量呈線性關(guān)系。而對(duì)Kf（Kd）、有機(jī)質(zhì)含量與pH進(jìn)行多元回歸分析發(fā)現(xiàn)，在pH的影響下，Kf（Kd）與有機(jī)質(zhì)含量呈非線性關(guān)系[57]。這是由于pH的變化不僅改變了土壤組分特性，同時(shí)也對(duì)毒死蜱的分子形態(tài)產(chǎn)生一定影響，二者共同作用使得吸附發(fā)生改變。目前對(duì)多因素影響土壤吸附毒死蜱的研究還鮮有報(bào)道，因此，考慮多重因素對(duì)土壤吸附毒死蜱的綜合影響，建立多因素吸附模型對(duì)于探索毒死蜱環(huán)境行為具有重要意義。

目前我國(guó)高等職業(yè)教育規(guī)模大，培養(yǎng)的學(xué)生人數(shù)眾多。但是，目前我國(guó)絕大多數(shù)的高等職業(yè)院校還是采用傳統(tǒng)的教學(xué)模式，這個(gè)在一定程度上制約著高素質(zhì)應(yīng)用技術(shù)人才的培養(yǎng)。一方面我們培養(yǎng)的高等職業(yè)教育人才就業(yè)難，另一方面在社會(huì)上企業(yè)招收不到合格的員工，導(dǎo)致企業(yè)效益難以提高,出現(xiàn)這種情況的最主要原因是學(xué)生沒(méi)有熟練掌握專(zhuān)業(yè)技能，不能夠在企業(yè)一線進(jìn)行熟練的生產(chǎn)，并不是所謂的“勞動(dòng)力過(guò)剩”或者“員工荒”。要解決這個(gè)矛盾，就必須在我國(guó)高等職業(yè)教育中采用雙元制教學(xué)模式培養(yǎng)一批高素質(zhì)應(yīng)用技術(shù)人才。

3 毒死蜱在土壤中的降解

3.1 毒死蜱在土壤中的降解途徑

毒死蜱進(jìn)入土壤后，主要通過(guò)非生物降解（光解）和生物降解（微生物降解、植物降解）作用來(lái)進(jìn)行轉(zhuǎn)化和消解[58-59]。表層土壤中毒死蜱以光解、水解為主；深層土壤中毒死蜱以微生物降解為主。其中，土壤微生物對(duì)毒死蜱的降解起到主要作用，約78%～95%的毒死蜱在土壤中被微生物降解[60-61]，表層土壤中僅少量毒死蜱發(fā)生光解[62]。

3.1.1 毒死蜱的光解

當(dāng)毒死蜱接受光輻射能后，光能轉(zhuǎn)化到分子鍵上導(dǎo)致相應(yīng)化學(xué)鍵斷裂而發(fā)生分解。毒死蜱在土壤中光解是C-C、C-H、C-O、C-N等化學(xué)鍵受光能作用而發(fā)生斷裂的內(nèi)部反應(yīng)過(guò)程。毒死蜱在自然光照下的半衰期一般為3～4周，但受土壤環(huán)境中光敏劑及土壤pH等因素的影響可以加速其在土壤中的光解。研究表明，在含有光敏劑（TiO2、ZnO）的土壤中，光照可以在20～40 min內(nèi)實(shí)現(xiàn)對(duì)毒死蜱100%的降解[63-64]。

此外，毒死蜱的光解效率還受到與其他農(nóng)藥在土壤環(huán)境中發(fā)生拮抗或協(xié)同作用的影響。如抗蚜威、丙烯菊酯等農(nóng)藥的存在對(duì)毒死蜱的光解有顯著的加速作用，而林丹、氟氯菊酯、殺螟松對(duì)毒死蜱有顯著的延緩光解作用[65]?？傊?，雖然光解是農(nóng)藥在環(huán)境中消解的主要途徑之一，但因受到光照的限制，一般只發(fā)生在表層土壤中，對(duì)深層土壤中毒死蜱的作用較弱。

3.1.2 毒死蜱的生物降解

普遍認(rèn)為，毒死蜱主要通過(guò)共代謝和礦化作用進(jìn)行生物降解。共代謝降解是單一毒死蜱不能為微生物提供碳源，需與土壤中其他有機(jī)質(zhì)（如糖類(lèi)、醇類(lèi)等）共同為微生物提供碳源，使微生物降解毒死蜱。共代謝作用只是部分改變了毒死蜱母體結(jié)構(gòu)，產(chǎn)生與母體近似的中間產(chǎn)物，并不能使毒死蜱徹底降解[66]，早期從環(huán)境中篩選出的毒死蜱降解菌多通過(guò)共代謝途徑降解毒死蜱。礦化作用是微生物以毒死蜱為唯一碳源，將毒死蜱分解為CO2和H2O等無(wú)機(jī)物的過(guò)程。礦化作用能夠使毒死蜱消除其毒性，并且避免產(chǎn)生對(duì)環(huán)境具有潛在威脅的中間產(chǎn)物。

無(wú)論是共代謝作用還是礦化作用，毒死蜱降解的第一步都屬于水解反應(yīng)。水解反應(yīng)有2種途徑：中性水解和堿性水解。中性水解是由H2O分子中孤對(duì)電子的親核攻擊導(dǎo)致烴基斷裂；堿性水解是由-OH中的電子在磷原子處的親核攻擊導(dǎo)致醇基或酚基鍵斷裂。目前普遍認(rèn)為，毒死蜱在土壤中的降解途徑以堿性水解為主[67]。毒死蜱在土壤中的生物降解途徑如圖4所示。

3.2 毒死蜱在土壤中的降解動(dòng)力學(xué)

無(wú)論是非生物降解（如光解）還是生物降解，毒死蜱在土壤中的主要降解產(chǎn)物均是O，O-二乙基硫代磷酸酯（dicethylthiophospshate,DETP）和3，5，6-三氯吡啶-2-酚（3,5,6-trichloro-2-pyridinol,TCP），其中DETP可以直接被生物利用生成硫代磷酸和乙醇[68]，因此毒死蜱降解產(chǎn)物在土壤中主要以TCP為主。TCP在土壤中降解難度大，降解周期長(zhǎng)，其半衰期一般為65～360 d。有研究表明，在粉砂壤中TCP的降解周期是毒死蜱降解周期的4倍[69]，對(duì)微生物群落的毒性是毒死蜱的2.5倍[42]，且和毒死蜱可能存在協(xié)同效應(yīng)，產(chǎn)生更大的生物毒性[70-71]。

其次，TCP水溶性大，在水中溶解度為80.9 mg/L（20℃），被美國(guó)環(huán)境保護(hù)署列為移動(dòng)性較強(qiáng)的農(nóng)藥，能夠進(jìn)入深層土壤及水體環(huán)境造成污染[72]。TCP由于其化學(xué)結(jié)構(gòu)穩(wěn)定，具有環(huán)境持久性。TCP對(duì)土壤中微生物群落生長(zhǎng)具有抑制作用，當(dāng)TCP濃度較高時(shí)可以抑制毒死蜱降解微生物的生長(zhǎng)，降低毒死蜱的生物降解速率[73]。因此，TCP在土壤中甲基化而進(jìn)一步降解，最終完全礦化為CO2，被認(rèn)為是毒死蜱完全脫毒的關(guān)鍵[74]。

土壤微生物是TCP降解礦化的主要驅(qū)動(dòng)力，在不同環(huán)境條件下微生物對(duì)TCP的礦化途徑不同。在有氧條件下，好氧微生物將TCP氧化生成3，5，6-三氯-2-甲氧基-吡啶酚（3,5,6-trichloro-2-methpxy-pyridinone,TCMP）或 3，5，6-三氯-2-甲基吡啶（3,5,6-trichloro-2-methpxy-methylpyridine,TMP），最終礦化為CO2被完全降解[75]（圖5A）。在缺氧/厭氧條件下，厭氧微生物可以脫掉TCP環(huán)結(jié)構(gòu)上的2個(gè)氯原子，生成吡啶酚，最終礦化生成CO2；或者直接脫掉環(huán)結(jié)構(gòu)上的3個(gè)氯原子，生成3，6-羥基吡啶-2，5-二酮[76]（圖5B）。

圖4 毒死蜱在土壤中的生物降解途徑Fig.4 Degradation pathway of chlorpyrifos in soils

圖5 TCP在土壤中的降解途徑Fig.5 Degradation pathway of TCP in soils

3.3 毒死蜱降解菌

早期對(duì)微生物降解菌的研究，主要集中在細(xì)菌方面。黃桿菌（Flaobacterium sp.）是最早報(bào)道的毒死蜱降解菌[77]。SINGH等[78]繼2003年首次報(bào)道了在澳大利亞土壤中富集分離出了毒死蜱強(qiáng)化降解菌后，將這種菌的強(qiáng)化降解功能應(yīng)用到英國(guó)5種不同的毒死蜱污染場(chǎng)地中，發(fā)現(xiàn)在土壤pH＞6.7條件下可保持降解菌90 d的降解時(shí)效；且研究發(fā)現(xiàn)，分離出的這種降解菌的16S rRNA序列與假單胞菌相同，這種RNA序列可能是使該菌降解土壤中毒死蜱的主導(dǎo)基因。MOHAN等[79]將生物反應(yīng)器作為研究介質(zhì)，分離出一種細(xì)菌，72 h內(nèi)可將土壤中3 000 μg/g的毒死蜱降解91%。KULSHRESTHA等[8]研究發(fā)現(xiàn)，復(fù)合菌落30 d內(nèi)可以降解土壤中85%的毒死蜱，而單一菌種在相同時(shí)間內(nèi)只能降解土壤中77%的毒死蜱，復(fù)合微生物菌落（GCC134）更有利于降解土壤中的毒死蜱。

研究發(fā)現(xiàn)，土壤中某些真菌同樣可以顯著提高對(duì)毒死蜱的降解速率[80-84]。FANG等[84]從土壤中分離出了一種輪枝菌（Verticillium），并用這種菌修復(fù)毒死蜱污染場(chǎng)地，發(fā)現(xiàn)添加這種菌后能顯著提高土壤中毒死蜱的降解效率，是對(duì)照土壤降解速率的1.10～3.61倍。

目前，對(duì)毒死蜱微生物降解研究多集中于不同菌種（包含細(xì)菌和真菌）對(duì)土壤中毒死蜱的降解，主要降解菌種及降解效果見(jiàn)表4。

土著微生物群落不僅能夠降解毒死蜱，還能進(jìn)一步降解毒死蜱的代謝產(chǎn)物TCP，徹底消除毒死蜱的毒性。MASSIHA等[85]利用野外實(shí)驗(yàn)研究了土壤土著降解菌對(duì)毒死蜱的降解作用，發(fā)現(xiàn)了土壤中細(xì)菌、真菌和放線菌的存在，可以在25 d內(nèi)將50 mg/kg毒死蜱降解為T(mén)CP，而殘留的TCP和相關(guān)副產(chǎn)物在6 d內(nèi)全部礦化為CO2和H2O。相反，毒死蜱的存在也會(huì)影響土壤中微生物菌落的活性。GILANI等[86]研究發(fā)現(xiàn)，農(nóng)田表層土壤（毒死蜱質(zhì)量分?jǐn)?shù)為100～1 000 mg/kg）在1年內(nèi)沒(méi)有發(fā)生生物降解，且毒死蜱的存在對(duì)毒死蜱降解菌——芽孢桿菌（Bacillus sp.）的活性產(chǎn)生了一定的抑制作用。為了提高Bacillus sp.對(duì)毒死蜱的耐性，ZHANG等[87]引入了一種質(zhì)粒介導(dǎo)的生物添加技術(shù)，這種技術(shù)將pDOC質(zhì)粒編碼的毒死蜱降解基因?qū)隑acillus sp.內(nèi)，使降解菌在5 d內(nèi)通過(guò)pDOC編碼基因強(qiáng)化毒死蜱降解能力。因此，通過(guò)基因技術(shù)向土壤微生物中導(dǎo)入相應(yīng)編碼基因，可以顯著提高微生物在不同土壤中的毒死蜱降解效率。

4 總結(jié)與展望

毒死蜱是使用廣泛的有機(jī)磷農(nóng)藥，毒死蜱的環(huán)

境行為、歸趨和環(huán)境影響受到持續(xù)的關(guān)注。

表4 土壤中常見(jiàn)毒死蜱降解菌Table 4 Degradation bacteria of chlorpyrifos in soil

1）毒死蜱在土壤中的吸附/解吸與土壤有機(jī)質(zhì)含量顯著相關(guān)，同時(shí)受土壤pH、環(huán)境溫度等多因素影響。考慮多重因素對(duì)土壤吸附毒死蜱的綜合影響，建立多因素吸附模型，對(duì)探索毒死蜱環(huán)境行為有重要意義。

2）微生物降解和光降解是土壤中毒死蜱降解的主要途徑。研究毒死蜱在土壤環(huán)境中不同途徑（光解、微生物降解）的降解機(jī)制，可以進(jìn)一步理解土壤中毒死蜱環(huán)境行為的驅(qū)動(dòng)機(jī)制。

3）通過(guò)基因?qū)爰夹g(shù)，強(qiáng)化土壤微生物菌落的降解能力，通過(guò)細(xì)菌、真菌等土壤微生物的作用可以將毒死蜱主要降解產(chǎn)物TCP完全礦化。同時(shí)，考慮到作物種植以及農(nóng)藥施用主要發(fā)生在土壤表層，強(qiáng)化光敏劑介導(dǎo)的毒死蜱光解，實(shí)現(xiàn)對(duì)土壤表層毒死蜱的快速降解。

表4 (續(xù)) Continuation of Table 4

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