竇琦瑋,段佳奇,唐新宇,姚慶禎,蘇榮國(guó)

磺胺氯噠嗪在海水中的間接光降解

竇琦瑋,段佳奇,唐新宇,姚慶禎,蘇榮國(guó)*

(中國(guó)海洋大學(xué)化學(xué)化工學(xué)院,山東 青島 266100)

以有色溶解有機(jī)物(CDOM)作為主要光敏劑研究磺胺氯噠嗪(SCP)間接光降解行為和機(jī)理,分析CDOM組成、鹽度和pH值對(duì)SCP間接光降解的影響.SCP間接光降解速率隨CDOM濃度升高而逐漸加快.CDOM產(chǎn)生的光化學(xué)反應(yīng)活性中間體對(duì)SCP間接光降解的貢獻(xiàn)率不同,其中3CDOM*起主要作用,對(duì)SCP間接光降解的貢獻(xiàn)率高達(dá)77.94%.所用CDOM由4種熒光組分組成,包含3種外源腐殖質(zhì)(C1,C2,C3)和1種內(nèi)源腐殖質(zhì)(C4), SCP間接光降解去除率和3CDOM*濃度分別與熒光組分的相關(guān)性大小順序均為C3>C2>C4>C1.其中C3和C2與[3CDOM*]具有較高線性相關(guān)性(R2>0.97),是3CDOM*的主要貢獻(xiàn)者.鹽度和pH值對(duì)SCP間接光降解的影響作用顯著.在鹽度為15‰時(shí),SCP的間接光降解速率最大.在低鹽度范圍(0～15‰)內(nèi),離子強(qiáng)度效應(yīng)對(duì)間接光降解的促進(jìn)作用大于無(wú)機(jī)陰離子帶來(lái)的抑制作用,使得間接光降解速率隨著鹽度的升高而加快.溶液pH=(5.00±0.10)時(shí),SCP的間接光降解速率最大.SCP的間接光降解速率隨著溶液pH值的升高而減慢,中性和堿性環(huán)境不利于SCP的間接光降解.

磺胺氯噠嗪；間接光降解；CDOM熒光組成；環(huán)境因素

抗生素磺胺氯噠嗪(SCP)大量用于畜牧業(yè)和水產(chǎn)養(yǎng)殖業(yè)中的疾病治療,未被利用的SCP隨著污水進(jìn)入污水處理廠,經(jīng)處理后入海.但是常用的污水處理方法難以完全去除水體中的SCP,導(dǎo)致SCP在近岸海域的檢出率和濃度較高[1].間接光降解是大多數(shù)磺胺類抗生素的主要降解途徑[2-5].有色溶解有機(jī)物(CDOM)是自然水體中主要的光敏劑,其在吸收太陽(yáng)光后會(huì)形成光化學(xué)反應(yīng)活性中間體,主要包括單線態(tài)氧(1O2)、羥基自由基(HO·)以及三線態(tài)CDOM(3CDOM*)等[6],是促進(jìn)抗生素降解的重要物質(zhì)[7].研究[8]指出CDOM的來(lái)源會(huì)影響其光降解性,同時(shí)環(huán)境因素如鹽度和pH值也會(huì)影響水體中部分磺胺類抗生素的光降解[9-11].

目前對(duì)于CDOM組成對(duì)磺胺類抗生素間接光降解的研究較少,同時(shí)海水鹽度、pH值等環(huán)境因素對(duì)于磺胺類抗生素間接光降解的影響尚未可知.因此,本研究選取SCP作為研究對(duì)象,以CDOM在SCP間接光降解的作用作為研究重點(diǎn),考察CDOM產(chǎn)生的活性中間體、不同種類CDOM濃度以及鹽度和pH值對(duì)于SCP間接光降解的作用.采用激發(fā)-發(fā)射矩陣光譜(EEMs)與并行因子分析(PARAFAC)結(jié)合技術(shù)分析CDOM組成和來(lái)源, 考察其對(duì)SCP間接光降解的影響.以期為準(zhǔn)確、有效地預(yù)測(cè)近海海水中SCP的光化學(xué)降解過(guò)程和評(píng)價(jià)SCP帶來(lái)的生態(tài)風(fēng)險(xiǎn)提供科學(xué)依據(jù).

1 材料與方法

1.1 材料

磺胺氯噠嗪(SCP):純度>99%,購(gòu)于Ark Pharm.稱取0.1000g的SCP加入超純水配制成濃度為1g/L的母液,用0.1mol/L的鹽酸和氫氧化鈉溶液將母液pH值調(diào)節(jié)至pH=(8.00±0.10).

CDOM:河腐殖酸(SRHA)(2S101H,國(guó)際腐殖酸協(xié)會(huì)),河富里酸(SRFA)(2S101N,國(guó)際腐殖酸協(xié)會(huì)),河天然有機(jī)物(SRNOM)(2S101F,國(guó)際腐殖酸協(xié)會(huì)),腐殖酸(JKHA)(百靈威有限公司).分別稱取0.0190g的SRHA、0.0191g的SRFA、0.0195g的SRN-OM和0.0250g的JKHA加入超純水配成100mgC/L CDOM母液,將所有溶液用0.1mol/L的鹽酸和氫氧化鈉溶液調(diào)節(jié)至pH=(8.00±0.10).配制好的溶液均轉(zhuǎn)移到100mL棕色瓶中,避光置于冰箱中4℃冷藏保存.

1.2 光降解實(shí)驗(yàn)

1.2.1 不同種類和濃度CDOM影響實(shí)驗(yàn) 取13支50mL石英管,按照順序依次向石英管中加入800.0μL、2.00mL和4.00mL的0.1gC/L的不同種類的CDOM母液(對(duì)照管不加CDOM),每一支石英管再分別加入400.0μL的SCP母液并加超純水定容到40mL,使得配制后的溶液中CDOM濃度分別為2,5,10mgC/L(對(duì)照管CDOM濃度為0mgC/L),SCP初始濃度為10mg/L,將所有溶液用0.1mol/L的鹽酸和氫氧化鈉溶液調(diào)節(jié)至pH=(8.00±0.10).光降解實(shí)驗(yàn)在XPA-7光化學(xué)反應(yīng)儀中進(jìn)行,光化學(xué)反應(yīng)儀以1000W的氙燈作為模擬自然光源,使用320nm透光膜濾光,反應(yīng)溫度25℃,光照24h,每4h取一次樣品,用帶有孔徑為0.22μm的聚醚砜(PES)膜的注射器過(guò)濾后進(jìn)入1.5mL棕色進(jìn)樣瓶冷藏待測(cè).每組實(shí)驗(yàn)均設(shè)置3組平行樣.

1.2.2 活性中間體影響實(shí)驗(yàn) 取4支石英管,分別加入一定量的異丙醇、四氫呋喃、苯酚(1mmol/L,現(xiàn)配現(xiàn)用)儲(chǔ)備液和等量的超純水作為對(duì)照,向這4支石英管加入40.00mL的10mgC/L的JKHA儲(chǔ)備液以及400.0μL的SCP母液.將光解液溶液用0.1mol/L的鹽酸和氫氧化鈉溶液調(diào)節(jié)至pH=(8.00± 0.10).然后將石英管放入光化學(xué)反應(yīng)儀中按1.2.1中的條件進(jìn)行光解,取樣.

1.2.3 鹽度影響實(shí)驗(yàn) 取5支石英管加入40.00mL的10mgC/L的JKHA儲(chǔ)備液以及400.0μL的SCP母液,然后分別加入一定量的標(biāo)準(zhǔn)海水和超純水(作為對(duì)照),使最終配制的40.00mL反應(yīng)液的鹽度分別是5‰、15‰、25‰、35‰,CDOM濃度為10mgC/L,SCP初始濃度為10mg/L,將光解液用0.1mol/L的鹽酸和氫氧化鈉溶液調(diào)節(jié)至pH=(8.00± 0.10).然后將石英管放入光化學(xué)反應(yīng)儀中按1.2.1中的條件進(jìn)行光解,取樣.

1.2.4 pH值的影響實(shí)驗(yàn) 取4支石英管加入40.00mL的10mgC/L的JKHA儲(chǔ)備液以及400.0μL的SCP母液,加超純水使CDOM濃度為10mgC/L、SCP濃度為10mg/L.然后用0.1mol/L的稀鹽酸或氫氧化鈉溶液將反應(yīng)液調(diào)節(jié)pH值至pH=(5.00±0.10)、pH=(7.00±0.10)、pH=(8.00±0.10)、pH=(9.00±0.10)和pH=(11.00±0.10),用IAPSO標(biāo)準(zhǔn)海水將光解液鹽度調(diào)節(jié)為30‰.然后將石英管放入光化學(xué)反應(yīng)儀中按1.2.1中的條件進(jìn)行光解,取樣.

1.3 光譜分析

待測(cè)溶液經(jīng)孔徑為0.22μm的聚醚砜(PES)膜過(guò)濾后用熒光分光光度計(jì)(Fluorolog3-11)進(jìn)行熒光測(cè)定:激發(fā)波長(zhǎng)范圍240～480nm、發(fā)射波長(zhǎng)范圍250～ 580nm,掃描步長(zhǎng)5nm.狹縫寬度5nm,積分時(shí)間為0.05s,熒光強(qiáng)度用濃度為10mg/L的硫酸奎寧稀硫酸溶液進(jìn)行校正定標(biāo).

待測(cè)溶液經(jīng)孔徑為0.22μm的聚醚砜(PES)膜過(guò)濾后用紫外可見分光光度計(jì)(UV-2500)進(jìn)行測(cè)定,波長(zhǎng)范圍為200～800nm,參比液為超純水.

1.4 液相色譜條件

色譜柱為Agilent PLRP-S(5μm,150×4.60mm) C18液相色譜柱,進(jìn)樣量20μL.流動(dòng)相為甲酸(0.1%):乙腈=60:40,檢測(cè)波長(zhǎng)為270nm.

2 結(jié)果與討論

2.1 SCP在CDOM溶液中的間接光降解

SCP的最大吸收峰在320nm以下(圖1),使用320nm濾光膜過(guò)濾掉320nm以下的紫外光,可以有效屏蔽SCP直接光降解.

通過(guò)HPLC測(cè)定光降解過(guò)程中的SCP濃度,以一級(jí)反應(yīng)動(dòng)力學(xué)函數(shù)獲得間接光降解速率常數(shù)obs,2>0.97.

在pH=(8.00±0.10)的條件下,10mg/L的SCP在不同濃度不同來(lái)源CDOM溶液中的光降解情況如圖2所示.

在添加CDOM后,SCP的間接光降解速率都有不同程度的提高,且隨著CDOM濃度的升高,SCP的間接光降解速率均明顯加快.其中,JKHA濃度變化的影響最為顯著,對(duì)于SCP間接光降解的促進(jìn)作用最強(qiáng),而SRNOM、SRHA和SRFA對(duì)于SCP間接光降解的促進(jìn)作用基本相等.從4種CDOM的光吸收曲線(圖1)可以看出,JKHA的吸光度遠(yuǎn)高其他3種,對(duì)光具有較強(qiáng)吸收作用是JKHA顯著促進(jìn)SCP光降解的主要原因之一.

圖2 SCP在CDOM溶液中的間接光降解

CDOM在光化學(xué)反應(yīng)過(guò)程中會(huì)產(chǎn)生活性中間體,這些活性中間體與有機(jī)污染物反應(yīng)實(shí)現(xiàn)有機(jī)污染物的間接光降解.常見的活性中間體有3CDOM*、HO·、1O2等,其中3CDOM*除了可以直接降解抗生素以外,還可以通過(guò)電子、能量和氫原子轉(zhuǎn)移與水及溶解氧生成HO·、1O2等促進(jìn)有機(jī)污染物光降解[8,12]. Tang等[13]測(cè)定了本研究所用4種CDOM溶液中活性中間體的穩(wěn)態(tài)濃度(表1),表明活性中間體的穩(wěn)態(tài)濃度隨CDOM濃度的增加而增加.

表1 不同濃度的4種CDOM產(chǎn)生的活性中間體的穩(wěn)態(tài)濃度

2.2 活性中間體影響實(shí)驗(yàn)

異丙醇(IPA)通常作為HO·的猝滅劑[14];四氫呋喃(THF)為1O2的猝滅劑[15];苯酚既可以猝滅HO·又可以抑制由3CDOM*引導(dǎo)的光轉(zhuǎn)化過(guò)程.本研究采用異丙醇、四氫呋喃、苯酚分別作為HO·、1O2以及3CDOM*的猝滅劑研究SCP的間接光降解機(jī)理(圖 3).添加苯酚后,SCP的間接光降解速率顯著減慢,3CDOM*被猝滅后SCP間接光降解過(guò)程受到了明顯抑制,說(shuō)明3CDOM*在CDOM參與的SCP間接光降解中起主要作用[16];在添加四氫呋喃和異丙醇后,SCP的間接光降解速率變化較小,說(shuō)明1O2和HO·對(duì)SCP間接光降解的作用并不顯著.

圖3 SCP在猝滅劑溶液中的間接光降解

將添加了自由基猝滅劑的obs降低率作為各活性自由基的貢獻(xiàn)率(表2),可以看出3CDOM*對(duì)SCP間接光降解的貢獻(xiàn)率最大,達(dá)到77.94%,HO·的貢獻(xiàn)率次之,為11.62%,1O2在SCP間接光降解中的作用最小.

表2 各活性中間體對(duì)SCP間接光降解的貢獻(xiàn)率

2.3 CDOM熒光組成對(duì)SCP間接光降解的影響

2.3.1 CDOM熒光組成 CDOM是天然水體中最主要的光敏劑,不同來(lái)源的CDOM其組成和化學(xué)性質(zhì)不同,對(duì)SCP間接光降解的作用也不同.利用EEMs-PARAFAC解析獲得4種CDOM樣品的熒光組分C1,C2,C3和C4(圖4,表3).

C1的最大激發(fā)波長(zhǎng)和最大發(fā)射波長(zhǎng)分別為355和460nm,這與Singh等[17]報(bào)道的最大激發(fā)/發(fā)射波長(zhǎng)為370/460nm的陸地源類腐殖質(zhì)熒光組分相似,也與Coble等[18]報(bào)道的激發(fā)和發(fā)射波長(zhǎng)在 350nm/ 420～480nm 的組分峰以及Yamashita等[19]在利物浦灣發(fā)現(xiàn)的來(lái)自陸地水生環(huán)境的微生物衍生的類腐殖質(zhì)成分(xmax/mmax=(265)370/464nm)相似.因此,C1被認(rèn)為是一種外源類腐殖質(zhì)熒光組分.

表3 CDOM 4種組分的熒光強(qiáng)度

C2在300和405nm處出現(xiàn)激發(fā)峰值,其中405nm為最大激發(fā)波長(zhǎng),最大發(fā)射波長(zhǎng)為495nm.這與之前報(bào)道的最大激發(fā)波長(zhǎng)和最大發(fā)射波長(zhǎng)為350～455/492～520nm的來(lái)源于土壤的富里酸熒光組分類似[20],也與Yamashita等[21]報(bào)道的外源類腐殖質(zhì)熒光組分(xmax/mmax=390(275)479nm)類似.

C3的兩個(gè)峰值激發(fā)波長(zhǎng)分別在335和460nm,其中最大激發(fā)波長(zhǎng)為460nm,最大發(fā)射波長(zhǎng)為525nm.這與Singh等[17]報(bào)道的組分4(xmax/mmax= 240(410)/520nm)和Lochmuller等[20]報(bào)道的“Contech FA”(Exmax/Emmax=390/509nm)相似.該成分被認(rèn)為是源自農(nóng)業(yè)集水區(qū)以及微生物降解等過(guò)程中產(chǎn)生的.

C4的最大激發(fā)波長(zhǎng)和最大發(fā)射波長(zhǎng)分別為315和425nm,這與之前報(bào)道[22]的組分4(xmax/mmax= 325(250)/416nm)和代表海洋類腐殖質(zhì)的峰值M[23](xmax/mmax=312/380～420nm)相似.該組分被認(rèn)為是一種內(nèi)源類腐殖質(zhì)組分,通常在微生物降解過(guò)程中產(chǎn)生.

表4 CDOM熒光組分

在相同的DOC濃度下,CDOM總熒光強(qiáng)度的大小排序?yàn)镴KHA>SRFA>SRNOM>SRHA(表3),其中JKHA熒光強(qiáng)度明顯高于其他3種CDOM,且C2和C3組分占比較高,JKHA中C2和C3熒光強(qiáng)度分別約占總熒光強(qiáng)度的39%和35%.

2.3.2 CDOM熒光組成對(duì)SCP間接光降解的影響 C2和C3組分與1O2、HO·和3CDOM*的穩(wěn)態(tài)濃度之間存在較強(qiáng)的相關(guān)性(2>0.659)(表5).研究表明外源CDOM的分子量和芳香性均高于內(nèi)源CDOM[24], C2和C3具有較長(zhǎng)的激發(fā)和發(fā)射波長(zhǎng),分子量大,芳香程度高[25].芳香度高、分子量大的CDOM具有較高的活性中間體產(chǎn)率[26].

4個(gè)熒光組分與SCP去除率的相關(guān)性及4個(gè)熒光組分與3CDOM*濃度的相關(guān)性大小順序均為C3> C2>C4>C1.C2和C3與3CDOM*濃度的相關(guān)性較高(2>0.97),表明C2與C3組分是3CDOM*的主要來(lái)源.而JKHA中C2與C3組分含量較高,對(duì)SCP間接光降解表現(xiàn)出較強(qiáng)的促進(jìn)作用,這也是JKHA能顯著促進(jìn)SCP間接光降解的原因之一.

表5 SCP間接光降解速率、CDOM組分熒光強(qiáng)度與活性中間體穩(wěn)態(tài)濃度之間的相關(guān)性

* 在0.05級(jí)別(雙尾),相關(guān)性顯著;** 在0.01級(jí)別(雙尾),相關(guān)性顯著.

2.3 鹽度對(duì)SCP間接光降解的影響

有研究[9-11]表明鹽度會(huì)抑制水體中抗生素的光降解作用.光解液中JKHA濃度為10mgC/L,光解結(jié)果如圖5.在實(shí)驗(yàn)設(shè)置的鹽度范圍內(nèi)(0～35‰),隨著鹽度的升高,SCP的間接光降解速率先加快后減慢,在鹽度為15‰時(shí)SCP的間接光降解最快.低鹽度范圍內(nèi)(0～15‰),鹽度的升高對(duì)于SCP間接光降解的促進(jìn)作用逐漸增強(qiáng),而在高鹽度范圍內(nèi)(15‰～35‰),隨鹽度升高SCP的間接光降解速率越來(lái)越慢.

鹽度的提高使得離子強(qiáng)度增強(qiáng),離子強(qiáng)度效應(yīng)使得海水中3CDOM*穩(wěn)態(tài)濃度顯著增加[27],3CDOM*穩(wěn)態(tài)濃度的升高促進(jìn)了水中SCP的間接光降解.然而,海水中還存在各種無(wú)機(jī)陰離子,如氯離子和溴離子,無(wú)機(jī)陰離子可以清除HO·[28-29],從而降低了SCP的間接光降解速率,抑制SCP的間接光降解.所以,在低鹽度范圍內(nèi)(0～15‰),離子強(qiáng)度效應(yīng)對(duì)SCP間接光降解的促進(jìn)作用要大于無(wú)機(jī)陰離子帶來(lái)的抑制作用,使得SCP間接光降解速率隨著鹽度的升高而加快;而在高鹽度范圍內(nèi)(15‰～35‰),離子強(qiáng)度效應(yīng)帶來(lái)的對(duì)SCP間接光降解的促進(jìn)作用要小于無(wú)機(jī)陰離子帶來(lái)的抑制作用,這就導(dǎo)致SCP在高鹽度范圍內(nèi)(15‰～35‰)的間接光降解速率隨著鹽度的升高而減慢.

圖5 SCP在不同鹽度溶液中的間接光降解

2.4 海水環(huán)境下水體pH值對(duì)SCP間接光降解的影響

pH值不僅可以影響水體中離子、CDOM以及有機(jī)污染物的存在形態(tài),還可以影響活性中間體的生成速率[30],是水體中有機(jī)污染物間接光降解的重要影響因素.光解液中JKHA濃度為10mgC/L,光解結(jié)果如圖6.

SCP的間接光降解速率隨著溶液pH值的升高而減慢,在pH=(5.00±0.10)時(shí),SCP的間接光降解速率最大,表明中性和堿性環(huán)境抑制了SCP的間接光降解.

改變pH值可以導(dǎo)致可電離化合物的質(zhì)子化/去質(zhì)子化,改變化合物的存在形態(tài)和吸附性能.SCP的解離常數(shù)分別為pKa1=(2.0±0.8)和pKa2=(5.9±0.3),在低pH值條件下,SCP分子發(fā)生質(zhì)子化作用,質(zhì)子化后的SCP分子可與CDOM產(chǎn)生靜電吸附作用,而在中性和堿性條件下,去質(zhì)子化后的SCP-吸附系數(shù)明顯低于酸性條件下的SCP+吸附系數(shù),具有更強(qiáng)的靜電排斥作用[31],與CDOM的吸附作用變?nèi)?減少了SCP與活性中間體的接觸, SCP的間接光降解速率隨之減小.

圖6 SCP在不同pH溶液中的間接光降解

3 結(jié)論

3.1 本文所用4種CDOM對(duì)SCP的間接光降解均起促進(jìn)作用.當(dāng)CDOM濃度達(dá)到10mgC/L時(shí), JKHA對(duì)SCP間接光降解的作用遠(yuǎn)大于其他3種.不同CDOM對(duì)SCP間接光降解作用的不同主要是CDOM組成不同和活性中間體產(chǎn)生效率導(dǎo)致的.

3.2 CDOM光解產(chǎn)生的活性中間體如3CDOM*、HO·和1O2等參與SCP間接光降解.其中3CDOM*是SCP間接光降解的主要參與者,其貢獻(xiàn)率高達(dá)77.94%.

3.3 鹽度對(duì)SCP間接光降解的影響主要是離子強(qiáng)度效應(yīng)和鹵素離子效應(yīng)共同作用的結(jié)果.在鹽度為15‰時(shí),SCP的間接光降解最快.低鹽度范圍內(nèi)(0～15‰),鹽度的升高對(duì)于SCP間接光降解起促進(jìn)作用.

3.4 水體pH值影響SCP的存在形態(tài),當(dāng)pH= (5.00± 0.10)時(shí),SCP的間接光降解速率最大,pH值降低,不利于SCP的間接光降解.

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The indirect photodegradation of sulfapyridazine in seawater.

DOU Qi-wei, DUAN Jia-qi, TANG Xin-yu, YAO Qing-zhen, SU Rong-guo*

(College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China)., 2023,43(1)：190～196

The indirect photodegradation behavior and mechanism of SCP were studied by using CDOM that as the main photosensitizer. The effects of CDOM composition, salinity and pH on indirect photodegradation of SCP were analyzed. When CDOM concentration increased, the indirect photodegradation rate of SCP accelerated obviously. Upon irradiation, CDOM produced a variety of active substances, and the different active substances had different contribution rates to the indirect photodegradation of SCP, especially the3CDOM*played a major role in the indirect photodegradation of SCP and its contribution rate was up to 77.94%. The CDOM used in the experiment was composed of four components, including three terrestrial humus (C1, C2, C3) and the marine humus (C4). The order of the correlation between the SCP removal rates and the four fluorescence components was C3>C2>C4>C1. The correlation between four fluorescence components and [3CDOM*] were also ranked as the former. C3 and C2 components had a significant correlation with [3CDOM*] (2>0.97), that demonstrated the C3 and C2 components made great contributions to the production of [3CDOM*]. Salinity and pH value had significant effects on indirect photodegradation of SCP. When the salinity of the solution was equal to 15‰, the SCP indirect photodegradation rate reached a maximum. In the low salinity range (0～15‰), the promotion effect of ionic strength was greater than the inhibition effect of inorganic anions that made the indirect photodegradation rate greater with the increase of salinity. When the pH of the solution was equal to (5.00±0.10), the SCP indirect photodegradation rate reached a maximum. The indirect photodegradation rate of SCP slowed down with the increase of pH value of the solution, and the neutral and alkaline environments had negative effects on the indirect photodegradation of SCP.

sulfachloropyridazine；indirect photodegradation；CDOM composition；environmental factor

X703,X55

A

1000-6923(2023)01-0190-07

竇琦瑋(1998-),女,山東濰坊人,中國(guó)海洋大學(xué)碩士研究生,主要研究方向?yàn)楹Ｑ笪廴旧鷳B(tài)化學(xué).

2022-06-02

NSFC-山東聯(lián)合基金資助項(xiàng)目(U1906210);國(guó)家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2016YFC1402101)

*責(zé)任作者, 教授, surongguo@ouc.edu.cn