1 引言

土壤重金屬污染問(wen)題是當(dang)今主要(yao)的(de)(de)環境(jing)問(wen)題。重金屬難(nan)降解、易積累、毒性大(da)，對作物(wu)的(de)(de)生(sheng)長、產(chan)量(liang)和品質都有影響，尤(you)其(qi)是它還有被作物(wu)吸收進人食物(wu)鏈，從(cong)而危害人體健康的(de)(de)潛(qian)在威脅。近年來，伴隨著(zhu)礦產(chan)資源的(de)(de)大(da)量(liang)開發(fa)利用，工業生(sheng)產(chan)的(de)(de)迅猛發(fa)展(zhan)和各種化(hua)學產(chan)品、農藥及化(hua)肥(fei)的(de)(de)廣泛使用，我國面臨的(de)(de)土壤環境(jing)安全問(wen)題日益突(tu)出。

2 我國(guo)土壤重金屬污(wu)染現狀

據(ju)國(guo)(guo)(guo)家(jia)(jia)環(huan)保總局的(de)(de)(de)調查，目前(qian)我(wo)國(guo)(guo)(guo)一些(xie)地(di)(di)區(qu)(qu)土壤(rang)(rang)(rang)污(wu)(wu)染(ran)(ran)嚴重(zhong)(zhong)(zhong)(zhong)(zhong)，對(dui)生(sheng)態(tai)環(huan)境(jing)、食(shi)品安全和農業發展都(dou)構成(cheng)威脅。據(ju)不完(wan)全統(tong)計，目前(qian)全同受污(wu)(wu)染(ran)(ran)的(de)(de)(de)耕地(di)(di)已(yi)達(da)1000萬(wan)hm²，約(yue)占耕地(di)(di)總面積(ji)20 以上，每年(nian)因為土壤(rang)(rang)(rang)污(wu)(wu)染(ran)(ran)造成(cheng)的(de)(de)(de)經(jing)濟(ji)損失達(da)200億元，其中每年(nian)因重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染(ran)(ran)的(de)(de)(de)糧食(shi)達(da)1200萬(wan)t。而目前(qian)我(wo)國(guo)(guo)(guo)受Cd、As、Cr、Pb等(deng)(deng)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染(ran)(ran)的(de)(de)(de)耕地(di)(di)面積(ji)近(jin)2000萬(wan)hm²，約(yue)占總耕地(di)(di)面積(ji)的(de)(de)(de)1／5。據(ju)資料顯示我(wo)國(guo)(guo)(guo)的(de)(de)(de)耕地(di)(di)和大多數城市(shi)近(jin)郊農田都(dou)受到了不同程(cheng)度(du)的(de)(de)(de)污(wu)(wu)染(ran)(ran)，如(ru)北(bei)京市(shi)通惠河(he)(he)灌(guan)區(qu)(qu)土壤(rang)(rang)(rang)鉛含量(liang)近(jin)年(nian)來有(you)所升高，涼水(shui)河(he)(he)灌(guan)區(qu)(qu)的(de)(de)(de)鋅、鎘(ge)、汞(gong)也(ye)有(you)明顯上升；一些(xie)位(wei)點的(de)(de)(de)汞(gong)、鋅已(yi)超(chao)過國(guo)(guo)(guo)家(jia)(jia)土壤(rang)(rang)(rang)環(huan)境(jing)質量(liang)標準(GB15618—1995)的(de)(de)(de)極限值。長期的(de)(de)(de)污(wu)(wu)水(shui)灌(guan)溉已(yi)經(jing)引起了土壤(rang)(rang)(rang)以及稻(dao)米、小麥(mai)等(deng)(deng)糧食(shi)作物中鎘(ge)等(deng)(deng)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)元素的(de)(de)(de)積(ji)累，局部地(di)(di)區(qu)(qu)蔬菜(cai)(cai)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)的(de)(de)(de)含量(liang)已(yi)超(chao)標。天津市(shi)土壤(rang)(rang)(rang)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染(ran)(ran)已(yi)經(jing)形(xing)成(cheng)環(huan)境(jing)問(wen)題，東(dong)麗、西青和津南菜(cai)(cai)田土壤(rang)(rang)(rang)的(de)(de)(de)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染(ran)(ran)均為3級，屬(shu)(shu)于(yu)輕度(du)污(wu)(wu)染(ran)(ran)，北(bei)辰(chen)菜(cai)(cai)田土壤(rang)(rang)(rang)的(de)(de)(de)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染(ran)(ran)，達(da)到了中度(du)污(wu)(wu)染(ran)(ran)。此外，在重(zhong)(zhong)(zhong)(zhong)(zhong)慶、香港、貴州、福建、河(he)(he)北(bei)、廣西、汀(ting)西、海南、珠汀(ting)三角洲、北(bei)方河(he)(he)套地(di)(di)區(qu)(qu)等(deng)(deng)許多省市(shi)地(di)(di)區(qu)(qu)都(dou)發現了不同程(cheng)度(du)Hg、C；d、Pb、Cr、AS、Cu、Zn、Ni污(wu)(wu)染(ran)(ran)。我(wo)國(guo)(guo)(guo)的(de)(de)(de)一些(xie)主要水(shui)域如(ru)淮河(he)(he)、長江(jiang)流(liu)域、太湖流(liu)域、膠州灣等(deng)(deng)也(ye)發現了重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染(ran)(ran)。

2.1隨污(wu)(wu)(wu)水進(jin)入土(tu)(tu)壤(rang)的重(zhong)金屬污(wu)(wu)(wu)水灌(guan)(guan)溉一(yi)(yi)般是指經(jing)過一(yi)(yi)定處理的城(cheng)市(shi)污(wu)(wu)(wu)水灌(guan)(guan)溉農(nong)(nong)田(tian)、森(sen)林和(he)(he)草地。城(cheng)市(shi)污(wu)(wu)(wu)水包括生活污(wu)(wu)(wu)水、商業(ye)污(wu)(wu)(wu)水和(he)(he)工業(ye)污(wu)(wu)(wu)水。隨著(zhu)污(wu)(wu)(wu)水灌(guan)(guan)溉而(er)進(jin)入土(tu)(tu)壤(rang)的重(zhong)金屬，以不同的方(fang)式被(bei)土(tu)(tu)壤(rang)截留，固(gu)定的重(zhong)金屬被(bei)土(tu)(tu)壤(rang)礦質膠體和(he)(he)有機質迅(xun)速吸附，一(yi)(yi)般累積存土(tu)(tu)壤(rang)表層，白上而(er)下遞減(jian)。污(wu)(wu)(wu)灌(guan)(guan)區(qu)的累積分(fen)布(bu)特點是離污(wu)(wu)(wu)染源(yuan)近土(tu)(tu)壤(rang)含(han)(han)量高，距離遠則土(tu)(tu)壤(rang)含(han)(han)量低。中(zhong)國白20世紀6O年(nian)代至(zhi)今，污(wu)(wu)(wu)灌(guan)(guan)面積迅(xun)速擴大，以北(bei)方(fang)干旱地區(qu)污(wu)(wu)(wu)灌(guan)(guan)最(zui)為嚴(yan)重(zhong)。南(nan)方(fang)地區(qu)污(wu)(wu)(wu)灌(guan)(guan)面積僅占6%，其余(yu)在西(xi)北(bei)和(he)(he)青(qing)藏。污(wu)(wu)(wu)灌(guan)(guan)導致農(nong)(nong)田(tian)重(zhong)金屬Hg、Cd、Cr、As、Cu、Zn、Pb等含(han)(han)量的增加。

2.2 隨(sui)著(zhu)大氣(qi)沉降進入(ru)土壤的(de)重金屬

大(da)(da)氣(qi)(qi)中(zhong)的(de)(de)(de)(de)重金屬(shu)(shu)污染有(you)自(zi)然來(lai)(lai)源(yuan)和人(ren)為來(lai)(lai)源(yuan)兩(liang)種，由于(yu)宇宙天體(ti)作用及地球上(shang)各種地質作用而使某些重金屬(shu)(shu)元素(su)進(jin)入大(da)(da)氣(qi)(qi)中(zhong)屬(shu)(shu)于(yu)自(zi)然來(lai)(lai)源(yuan)，人(ren)為來(lai)(lai)源(yuan)主(zhu)要(yao)(yao)為工(gong)業(ye)(ye)生(sheng)產、汽(qi)車尾氣(qi)(qi)排放及汽(qi)車輪胎磨損產生(sheng)的(de)(de)(de)(de)大(da)(da)量含重金屬(shu)(shu)的(de)(de)(de)(de)有(you)害氣(qi)(qi)體(ti)和粉塵等，他(ta)們主(zhu)要(yao)(yao)分布在工(gong)礦的(de)(de)(de)(de)周同和公路(lu)、鐵路(lu)的(de)(de)(de)(de)兩(liang)側(ce)。經自(zi)然沉(chen)降和雨淋沉(chen)降進(jin)人(ren)土(tu)壤的(de)(de)(de)(de)重金屬(shu)(shu)污染，主(zhu)要(yao)(yao)以丁礦煙囪(cong)、廢(fei)物堆和公路(lu)為中(zhong)心(xin)，向四周及兩(liang)側(ce)擴散與重工(gong)業(ye)(ye)發達(da)程度、城(cheng)市(shi)(shi)的(de)(de)(de)(de)人(ren)口密度、土(tu)地利用率、交通發達(da)程度有(you)直接關(guan)系，距城(cheng)市(shi)(shi)越近污染的(de)(de)(de)(de)程度就(jiu)越重，污染強弱順序(xu)為城(cheng)市(shi)(shi)、郊(jiao)區、農村，隨(sui)離(li)城(cheng)市(shi)(shi)的(de)(de)(de)(de)距離(li)加大(da)(da)而降低，特別是城(cheng)市(shi)(shi)的(de)(de)(de)(de)郊(jiao)區污染較為嚴重。此外，還(huan)與城(cheng)市(shi)(shi)的(de)(de)(de)(de)人(ren)口密度、城(cheng)市(shi)(shi)土(tu)地利用率、機動車密度成正相(xiang)關(guan)，重工(gong)業(ye)(ye)越發達(da)，污染相(xiang)對就(jiu)越嚴重。

2.3 隨固體廢棄物進(jin)入土壤的重(zhong)金(jin)屬

固(gu)(gu)體(ti)(ti)廢(fei)(fei)棄(qi)(qi)物種(zhong)類(lei)繁(fan)多(duo)，成(cheng)分復雜，不同(tong)(tong)種(zhong)類(lei)其(qi)危(wei)害方(fang)式和(he)污(wu)染程度(du)不同(tong)(tong)。其(qi)中(zhong)(zhong)礦業(ye)和(he)工(gong)業(ye)固(gu)(gu)體(ti)(ti)廢(fei)(fei)棄(qi)(qi)物污(wu)染最為(wei)嚴重(zhong)。這(zhe)類(lei)廢(fei)(fei)棄(qi)(qi)物在堆放或(huo)處理(li)過程中(zhong)(zhong)，由(you)(you)于(yu)(yu)(yu)日曬、雨淋等影響(xiang)導致重(zhong)金(jin)(jin)屬(shu)極易(yi)移(yi)動，以輻(fu)射(she)狀、漏斗狀向周圍土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)、水體(ti)(ti)擴散(san)。有(you)(you)(you)一些固(gu)(gu)體(ti)(ti)廢(fei)(fei)棄(qi)(qi)物被直接或(huo)通過加(jia)(jia)工(gong)作(zuo)為(wei)肥料(liao)施(shi)人(ren)(ren)土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)，造成(cheng)土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)重(zhong)金(jin)(jin)屬(shu)污(wu)染。如隨著我國畜(chu)牧生產的(de)(de)發展，產生大量(liang)(liang)的(de)(de)家畜(chu)糞便及(ji)動物加(jia)(jia)工(gong)產生的(de)(de)廢(fei)(fei)棄(qi)(qi)物，這(zhe)類(lei)農(nong)業(ye)固(gu)(gu)體(ti)(ti)廢(fei)(fei)棄(qi)(qi)物中(zhong)(zhong)含(han)有(you)(you)(you)植物所(suo)需N、P、K 和(he)有(you)(you)(you)機質，同(tong)(tong)時由(you)(you)于(yu)(yu)(yu)飼料(liao)中(zhong)(zhong)添(tian)加(jia)(jia)了一定量(liang)(liang)的(de)(de)重(zhong)金(jin)(jin)屬(shu)鹽類(lei)，因此作(zuo)為(wei)肥料(liao)施(shi)人(ren)(ren)土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)增加(jia)(jia)了土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)Zn、Mn等重(zhong)金(jin)(jin)屬(shu)元素的(de)(de)含(han)量(liang)(liang)。磷(lin)石(shi)膏屬(shu)于(yu)(yu)(yu)化(hua)肥 業(ye)廢(fei)(fei)物，由(you)(you)于(yu)(yu)(yu)其(qi)有(you)(you)(you)一定量(liang)(liang)的(de)(de)正磷(lin)酸以及(ji)不同(tong)(tong)形態的(de)(de)含(han)磷(lin)化(hua)合物，并可(ke)以改(gai)良酸性(xing)土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)，從而被大量(liang)(liang)施(shi)入土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)，造成(cheng)了土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)中(zhong)(zhong)Cr、Pb、Mn、As含(han)量(liang)(liang)增加(jia)(jia)。磷(lin)鋼渣作(zuo)為(wei)磷(lin)源(yuan)施(shi)人(ren)(ren)土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)時，土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)中(zhong)(zhong)發現有(you)(you)(you)Cr的(de)(de)累積(ji)。污(wu)水處理(li)產生的(de)(de)污(wu)泥(ni)含(han)有(you)(you)(you)較高的(de)(de)有(you)(you)(you)機質和(he)氮、磷(lin)養分，因此土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)成(cheng)為(wei)污(wu)泥(ni)處理(li)的(de)(de)主要(yao)場所(suo)。一般來說，污(wu)泥(ni)中(zhong)(zhong)Cr、Pb、Cu、Zn、As極易(yi)超過控制(zhi)標準，污(wu)泥(ni)的(de)(de)施(shi)用可(ke)使土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)重(zhong)金(jin)(jin)屬(shu)含(han)量(liang)(liang)有(you)(you)(you)不同(tong)(tong)程度(du)的(de)(de)增加(jia)(jia)。其(qi)增加(jia)(jia)的(de)(de)幅(fu)度(du)與污(wu)泥(ni)中(zhong)(zhong)的(de)(de)重(zhong)金(jin)(jin)屬(shu)含(han)量(liang)(liang)、污(wu)泥(ni)的(de)(de)施(shi)用量(liang)(liang)及(ji)土(tu)(tu)(tu)(tu)壤(rang)(rang)(rang)管理(li)有(you)(you)(you)關(guan)。

2.4 隨農(nong)用(yong)物(wu)資進入(ru)土壤(rang)的(de)重金屬

農(nong)藥(yao)、化(hua)肥(fei)(fei)(fei)(fei)和地(di)膜是重(zhong)(zhong)(zhong)(zhong)(zhong)要的(de)(de)農(nong)用物(wu)資，對農(nong)業生產(chan)的(de)(de)發展起著(zhu)重(zhong)(zhong)(zhong)(zhong)(zhong)大的(de)(de)推動作(zuo)用。但(dan)長期不合(he)(he)理(li)施用，也(ye)易導致土壤(rang)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染。絕大多(duo)數的(de)(de)農(nong)藥(yao)為有(you)機(ji)化(hua)合(he)(he)物(wu)，少數為有(you)機(ji)—無機(ji)化(hua)合(he)(he)物(wu)或純礦物(wu)質，個別農(nong)藥(yao)在其組(zu)成中含有(you)Hg、As、Cu、Zn等重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)。重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)元(yuan)素是肥(fei)(fei)(fei)(fei)料(liao)中報道最多(duo)的(de)(de)污(wu)(wu)染物(wu)質。肥(fei)(fei)(fei)(fei)料(liao)中重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)含量(liang)一般(ban)是磷(lin)(lin)肥(fei)(fei)(fei)(fei)>復合(he)(he)肥(fei)(fei)(fei)(fei)>鉀肥(fei)(fei)(fei)(fei)>氮(dan)肥(fei)(fei)(fei)(fei)。氮(dan)、鉀肥(fei)(fei)(fei)(fei)料(liao)中重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)含量(liang)較低(di)，磷(lin)(lin)肥(fei)(fei)(fei)(fei)中含有(you)較多(duo)的(de)(de)有(you)害重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)，復合(he)(he)肥(fei)(fei)(fei)(fei)的(de)(de)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)主要來源于母料(liao)及加(jia)(jia)工流(liu)程所帶(dai)入。隨著(zhu)磷(lin)(lin)肥(fei)(fei)(fei)(fei)及復合(he)(he)肥(fei)(fei)(fei)(fei)的(de)(de)大量(liang)施用，土壤(rang)有(you)效(xiao)態Cd的(de)(de)含量(liang)不斷增(zeng)(zeng)加(jia)(jia)，作(zuo)物(wu)吸收Cd量(liang)也(ye)相(xiang)應增(zeng)(zeng)加(jia)(jia)。近(jin)年來，地(di)膜的(de)(de)大面積推廣使(shi)用，造成了(le)(le)土壤(rang)的(de)(de)白色污(wu)(wu)染。由于地(di)膜生產(chan)過程中加(jia)(jia)入了(le)(le)含有(you)Cd、Pb的(de)(de)熱穩定劑，同(tong)時也(ye)增(zeng)(zeng)加(jia)(jia)了(le)(le)土壤(rang)重(zhong)(zhong)(zhong)(zhong)(zhong)金(jin)屬(shu)(shu)污(wu)(wu)染。

3 土壤重金屬污染(ran)修復技(ji)術

土(tu)壤(rang)重(zhong)(zhong)金屬(shu)(shu)(shu)污染(ran)在一(yi)定(ding)時期(qi)內不表現(xian)出(chu)對(dui)環(huan)境的(de)(de)(de)危(wei)(wei)害(hai)性，當(dang)其含(han)量(liang)超過土(tu)壤(rang)承受(shou)力或(huo)限度(du)，或(huo)土(tu)壤(rang)環(huan)境條件變化(hua)時，重(zhong)(zhong)金屬(shu)(shu)(shu)有可(ke)能突然(ran)活(huo)化(hua)，引起(qi)嚴(yan)重(zhong)(zhong)的(de)(de)(de)生(sheng)(sheng)(sheng)態(tai)危(wei)(wei)害(hai)，被稱為(wei)“化(hua)學定(ding)時炸彈”。通常情(qing)況下，重(zhong)(zhong)金屬(shu)(shu)(shu)首(shou)先(xian)(xian)危(wei)(wei)害(hai)到土(tu)壤(rang)微生(sheng)(sheng)(sheng)物(wu)(wu)(wu)，不適應重(zhong)(zhong)金屬(shu)(shu)(shu)的(de)(de)(de)微生(sheng)(sheng)(sheng)物(wu)(wu)(wu)數(shu)量(liang)會劇烈降(jiang)低(di)，甚至(zhi)滅絕(jue)，適應重(zhong)(zhong)金屬(shu)(shu)(shu)的(de)(de)(de)微生(sheng)(sheng)(sheng)物(wu)(wu)(wu)存活(huo)下來，逐漸成為(wei)土(tu)壤(rang)優勢菌(jun)。重(zhong)(zhong)金屬(shu)(shu)(shu)對(dui)土(tu)壤(rang)中生(sheng)(sheng)(sheng)長(chang)的(de)(de)(de)農作(zuo)物(wu)(wu)(wu)也有很強的(de)(de)(de)毒(du)害(hai)作(zuo)用，其影響在于：一(yi)方面重(zhong)(zhong)金屬(shu)(shu)(shu)能破壞(huai)植(zhi)物(wu)(wu)(wu)的(de)(de)(de)一(yi)些組織和功能，從(cong)而降(jiang)低(di)植(zhi)物(wu)(wu)(wu)的(de)(de)(de)產量(liang)和品(pin)質，如(ru)土(tu)壤(rang)鎘含(han)量(liang)過高會破壞(huai)植(zhi)物(wu)(wu)(wu)葉片(pian)的(de)(de)(de)葉綠素結構并最終導(dao)致植(zhi)物(wu)(wu)(wu)衰亡(wang)，土(tu)壤(rang)中銅、鋅含(han)量(liang)超過一(yi)定(ding)限度(du)時，作(zuo)物(wu)(wu)(wu)根部會受(shou)到嚴(yan)重(zhong)(zhong)損(sun)害(hai)。治(zhi)(zhi)標當(dang)先(xian)(xian)治(zhi)(zhi)本，如(ru)果要改善蔬菜及作(zuo)物(wu)(wu)(wu)的(de)(de)(de)品(pin)質，土(tu)壤(rang)的(de)(de)(de)重(zhong)(zhong)金屬(shu)(shu)(shu)污染(ran)應當(dang)先(xian)(xian)治(zhi)(zhi)理(li)。

3.1 工程措施

通過客(ke)土(tu)(tu)(tu)、換土(tu)(tu)(tu)和(he)深耕(geng)翻土(tu)(tu)(tu)等措(cuo)施(shi)，可(ke)以降低土(tu)(tu)(tu)壤(rang)中重(zhong)金屬的(de)(de)(de)含量，減(jian)少重(zhong)金屬對(dui)土(tu)(tu)(tu)壤(rang)及(ji)植物(wu)系統產生(sheng)的(de)(de)(de)毒(du)害，從而使(shi)農產品達到食品衛生(sheng)標準。深耕(geng)翻土(tu)(tu)(tu)用(yong)(yong)于輕(qing)度污染的(de)(de)(de)土(tu)(tu)(tu)壤(rang)，而客(ke)土(tu)(tu)(tu)和(he)換土(tu)(tu)(tu)則實用(yong)(yong)于重(zhong)污染區(qu)。工程措(cuo)施(shi)是比較(jiao)經典的(de)(de)(de)土(tu)(tu)(tu)壤(rang)重(zhong)金屬污染治理措(cuo)施(shi)，它(ta)具(ju)有徹底、穩(wen)定的(de)(de)(de)優(you)點，但(dan)實施(shi)工程量大(da)、投資費用(yong)(yong)高，破壞土(tu)(tu)(tu)體結構，引起土(tu)(tu)(tu)壤(rang)肥力下降，并且還要對(dui)換出的(de)(de)(de)污土(tu)(tu)(tu)進(jin)行堆(dui)放或處理。

3.2 物理修(xiu)復

(1)電動修(xiu)復(fu)是(shi)通過，在(zai)(zai)電場的(de)作用(yong)下，土(tu)(tu)壤(rang)中的(de)重金(jin)屬(shu)離(li)子(如Pb，Cd，Cr，Zn等)和無機離(li)子以(yi)(yi)電透滲和電遷移的(de)方式向電極(ji)運(yun)輸，然后進(jin)行(xing)集中收集處理。研究(jiu)發現，土(tu)(tu)壤(rang)pH、緩沖性能、土(tu)(tu)壤(rang)組分及污(wu)染金(jin)屬(shu)種類會影響修(xiu)復(fu)的(de)效果。該方法(fa)特別適合(he)于低滲透的(de)粘土(tu)(tu)和淤泥(ni)土(tu)(tu)，可(ke)以(yi)(yi)控制(zhi)污(wu)染物的(de)流(liu)動方向。在(zai)(zai)沙土(tu)(tu)上的(de)實驗(yan)結果表明，土(tu)(tu)壤(rang)中Pb2+，Cr6+。 等重金(jin)屬(shu)離(li)子的(de)除去率(lv)也可(ke)達90%以(yi)(yi)上。電動修(xiu)復(fu)是(shi)一種原位(wei)修(xiu)復(fu)技(ji)術，不攪動土(tu)(tu)層，并可(ke)以(yi)(yi)縮短(duan)修(xiu)復(fu)時(shi)間，是(shi)一種經濟可(ke)行(xing)的(de)修(xiu)復(fu)技(ji)術。

(2)電(dian)熱修復(fu)是(shi)利用高頻電(dian)壓產(chan)生電(dian)磁波，產(chan)生熱能(neng)，對(dui)土(tu)壤(rang)(rang)(rang)進行加熱，使污染(ran)物從土(tu)壤(rang)(rang)(rang)顆粒內(nei)解吸出來，加快一些易(yi)揮發(fa)性重(zhong)(zhong)金(jin)(jin)屬從土(tu)壤(rang)(rang)(rang)中(zhong)分離(li)，從而達到(dao)修復(fu)的(de)目(mu)的(de)。該技術可以修復(fu)被Hg和(he)Se等重(zhong)(zhong)金(jin)(jin)屬污染(ran)的(de)土(tu)壤(rang)(rang)(rang)。另(ling)外把(ba)重(zhong)(zhong)金(jin)(jin)屬污染(ran)區土(tu)壤(rang)(rang)(rang)置于高溫高壓下，形成(cheng)玻璃(li)態物質，從而達到(dao)從根本上消除土(tu)壤(rang)(rang)(rang)重(zhong)(zhong)金(jin)(jin)屬污染(ran)的(de)目(mu)的(de)。

3.3 化學(xue)修復

化(hua)學(xue)(xue)修復(fu)是(shi)利用(yong)化(hua)學(xue)(xue)試(shi)劑(ji)(ji)、化(hua)學(xue)(xue)反應(ying)或(huo)化(hua)學(xue)(xue)原理來(lai)降低(di)土(tu)(tu)壤(rang)中重金屬(shu)的(de)(de)遷移性(xing)、生物(wu)可利用(yong)率(lv)，減少(shao)甚至去(qu)除(chu)土(tu)(tu)壤(rang)中的(de)(de)重金屬(shu)，從而達到(dao)土(tu)(tu)壤(rang)的(de)(de)治理和(he)修復(fu)。化(hua)學(xue)(xue)修復(fu)主(zhu)要(yao)包括淋(lin)洗(xi)、淋(lin)洗(xi)—提取法(fa)(fa)(fa)(fa)(fa)、固化(hua)法(fa)(fa)(fa)(fa)(fa)、電化(hua)學(xue)(xue)方(fang)法(fa)(fa)(fa)(fa)(fa)和(he)施用(yong)改良劑(ji)(ji)法(fa)(fa)(fa)(fa)(fa)等。淋(lin)洗(xi)法(fa)(fa)(fa)(fa)(fa)是(shi)用(yong)清水(shui)淋(lin)洗(xi)液或(huo)含有(you)化(hua)學(xue)(xue)助劑(ji)(ji)的(de)(de)水(shui)溶(rong)液淋(lin)洗(xi)被污染的(de)(de)土(tu)(tu)壤(rang)，又稱洗(xi)土(tu)(tu)法(fa)(fa)(fa)(fa)(fa)或(huo)萃取法(fa)(fa)(fa)(fa)(fa) 。在多數(shu)情況(kuang)下，為提高淋(lin)洗(xi)液的(de)(de)洗(xi)脫效率(lv)，需要(yao)在淋(lin)洗(xi)液中加入一些能增大重金屬(shu)水(shui)溶(rong)性(xing)和(he)遷移性(xing)的(de)(de)化(hua)學(xue)(xue)助劑(ji)(ji)；最常用(yong)的(de)(de)化(hua)學(xue)(xue)助劑(ji)(ji)是(shi)酸和(he)鰲合劑(ji)(ji)，而后者對土(tu)(tu)壤(rang)的(de)(de)就地淋(lin)洗(xi)更(geng)適用(yong)，因(yin)為它們(men)對環(huan)境的(de)(de)危害(hai)更(geng)小。淋(lin)洗(xi)土(tu)(tu)壤(rang)所用(yong)的(de)(de)主(zhu)要(yao)的(de)(de)化(hua)學(xue)(xue)試(shi)劑(ji)(ji)有(you)乙二胺四乙酸二鈉鹽(yan)(EDTA)、酸、弱酸鹽(yan)等。

向土(tu)壤(rang)(rang)投入改良(liang)劑，通過(guo)對重(zhong)金(jin)(jin)屬的(de)(de)(de)吸(xi)附、氧化(hua)(hua)還(huan)原、拮抗(kang)或沉淀作用(yong)，以(yi)降(jiang)低(di)重(zhong)金(jin)(jin)屬的(de)(de)(de)生物有效(xiao)性(xing)。該技(ji)術(shu)關鍵(jian)在(zai)(zai)(zai)于選擇經濟有效(xiao)的(de)(de)(de)改良(liang)劑，常用(yong)的(de)(de)(de)改良(liang)劑有石灰、沸(fei)石、碳酸鈣、磷酸鹽(yan)(yan)、硅酸鹽(yan)(yan)和促進還(huan)原作用(yong)的(de)(de)(de)有機物質，不(bu)(bu)同改良(liang)劑對重(zhong)金(jin)(jin)屬的(de)(de)(de)作用(yong)機理(li)不(bu)(bu)同。施用(yong)石灰或碳酸鈣主要是提高(gao)土(tu)壤(rang)(rang)pM值，促使(shi)土(tu)壤(rang)(rang)中Cd、Cu、Hg、Zn等元素(su)形成(cheng)氫(qing)氧化(hua)(hua)物或碳酸鹽(yan)(yan)結合態鹽(yan)(yan)類沉淀。如當土(tu)壤(rang)(rang)pH>6.5時，Hg就能形成(cheng)氫(qing)氧化(hua)(hua)物或碳酸鹽(yan)(yan)沉淀。化(hua)(hua)學修復是在(zai)(zai)(zai)土(tu)壤(rang)(rang)原位(wei)上進行(xing)的(de)(de)(de)，簡(jian)單易(yi)行(xing)。但并不(bu)(bu)是一種(zhong)永(yong)久(jiu)的(de)(de)(de)修復措施，因為它只改變了重(zhong)金(jin)(jin)屬在(zai)(zai)(zai)土(tu)壤(rang)(rang)中存在(zai)(zai)(zai)的(de)(de)(de)形態，金(jin)(jin)屬元素(su)仍保留在(zai)(zai)(zai)土(tu)壤(rang)(rang)中，容易(yi)再度活化(hua)(hua)危害植物。

3.4 生物(wu)修復

生(sheng)(sheng)(sheng)物(wu)修(xiu)復(fu)是(shi)利用(yong)生(sheng)(sheng)(sheng)物(wu)技(ji)術治理污(wu)(wu)染(ran)土(tu)(tu)壤(rang)的一種新方(fang)(fang)法(fa)。利用(yong)生(sheng)(sheng)(sheng)物(wu)削減、凈化土(tu)(tu)壤(rang)中的重金(jin)屬(shu)或降低重金(jin)屬(shu)毒性。由于該方(fang)(fang)法(fa)效果好，易(yi)于操作，日(ri)益受到人們(men)的重視(shi)，成為污(wu)(wu)染(ran)土(tu)(tu)壤(rang)修(xiu)復(fu)研(yan)(yan)究(jiu)的熱點。目前(qian)生(sheng)(sheng)(sheng)物(wu)修(xiu)復(fu)技(ji)術主(zhu)要集中在植(zhi)物(wu)和微生(sheng)(sheng)(sheng)物(wu)兩方(fang)(fang)面，國內對土(tu)(tu)壤(rang)重金(jin)屬(shu)的植(zhi)物(wu)修(xiu)復(fu)方(fang)(fang)面研(yan)(yan)究(jiu)較多，動物(wu)修(xiu)復(fu)方(fang)(fang)面也有涉及在微生(sheng)(sheng)(sheng)物(wu)修(xiu)復(fu)方(fang)(fang)面國外研(yan)(yan)究(jiu)較多。

3.4.1 植(zhi)物修復

植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)修復(fu)技術是(shi)一(yi)(yi)種(zhong)利(li)用自然生長或(huo)(huo)遺傳培育(yu)植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)修復(fu)重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)污(wu)染(ran)土(tu)壤(rang)的(de)技術。根(gen)(gen)據(ju)其(qi)作用過程和機(ji)(ji)理，重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)污(wu)染(ran)土(tu)壤(rang)的(de)植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)修復(fu)技術可分(fen)為植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)提取(qu)、植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)揮發和植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)穩(wen)定(ding)3種(zhong)類型。植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)提取(qu)，即利(li)用重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)超(chao)積(ji)累植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)從(cong)土(tu)壤(rang)中(zhong)(zhong)吸取(qu)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)污(wu)染(ran)物(wu)(wu)(wu)(wu)(wu)，隨(sui)后收割(ge)地(di)上(shang)部分(fen)并進行集中(zhong)(zhong)處理，連續(xu)種(zhong)植(zhi)(zhi)(zhi)該植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)，達到(dao)降(jiang)低(di)或(huo)(huo)去除(chu)土(tu)壤(rang)重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)污(wu)染(ran)的(de)目(mu)的(de)。另外，加入一(yi)(yi)些有機(ji)(ji)絡合劑來增(zeng)加土(tu)壤(rang)中(zhong)(zhong)重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)的(de)生物(wu)(wu)(wu)(wu)(wu)有效性(xing)(xing)也可提高(gao)植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)對重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)的(de)吸收。植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)揮發，其(qi)機(ji)(ji)理是(shi)利(li)用植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)根(gen)(gen)系(xi)吸收金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)，將其(qi)轉(zhuan)化為氣(qi)態物(wu)(wu)(wu)(wu)(wu)質(zhi)揮發到(dao)大氣(qi)中(zhong)(zhong)，以(yi)降(jiang)低(di)土(tu)壤(rang)污(wu)染(ran)。目(mu)前這方面研究最多的(de)是(shi)類金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)元素Hg和非金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)元素Se。植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)穩(wen)定(ding)，利(li)用耐(nai)重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)或(huo)(huo)超(chao)累積(ji)植(zhi)(zhi)(zhi)物(wu)(wu)(wu)(wu)(wu)降(jiang)低(di)重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)的(de)活性(xing)(xing)，從(cong)而減少重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)被(bei)淋洗到(dao)地(di)下水或(huo)(huo)通(tong)過空氣(qi)擴散進一(yi)(yi)步污(wu)染(ran)環境的(de)可能性(xing)(xing)。其(qi)機(ji)(ji)理主(zhu)要是(shi)通(tong)過金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)在根(gen)(gen)部的(de)積(ji)累、沉淀(dian)或(huo)(huo)根(gen)(gen)表吸收來加強土(tu)壤(rang)中(zhong)(zhong)重(zhong)(zhong)(zhong)金(jin)(jin)(jin)(jin)(jin)(jin)屬(shu)(shu)(shu)(shu)(shu)(shu)的(de)固化。

3.4.2 微生(sheng)物修復

微生物(wu)(wu)(wu)(wu)(wu)修復技術在(zai)修復重(zhong)金(jin)屬(shu)污染的(de)土(tu)壤(rang)方面(mian)具有(you)獨特的(de)作用(yong)(yong)。其(qi)(qi)主(zhu)要作用(yong)(yong)原理有(you)：微生物(wu)(wu)(wu)(wu)(wu)通(tong)過各種(zhong)代謝活(huo)動產(chan)生多種(zhong)低(di)(di)分子有(you)機(ji)酸直接(jie)或(huo)(huo)間接(jie)溶(rong)解重(zhong)金(jin)屬(shu)或(huo)(huo)重(zhong)金(jin)屬(shu)礦(kuang)物(wu)(wu)(wu)(wu)(wu)，可(ke)(ke)(ke)以降低(di)(di)土(tu)壤(rang)中(zhong)重(zhong)金(jin)屬(shu)的(de)毒性(xing)：微生物(wu)(wu)(wu)(wu)(wu)的(de)代謝活(huo)動可(ke)(ke)(ke)以通(tong)過其(qi)(qi)氧化還原作用(yong)(yong)改變變價金(jin)屬(shu)的(de)存在(zai)狀(zhuang)態，降低(di)(di)這(zhe)些重(zhong)金(jin)屬(shu)元(yuan)素(su)的(de)活(huo)性(xing)；微生物(wu)(wu)(wu)(wu)(wu)可(ke)(ke)(ke)以通(tong)過胞(bao)外(wai)絡合作用(yong)(yong)，胞(bao)外(wai)沉淀(dian)作用(yong)(yong)以及胞(bao)內積累來實現對(dui)重(zhong)金(jin)屬(shu)的(de)固(gu)定(ding)作用(yong)(yong)；此外(wai)，細胞(bao)壁具有(you)活(huo)性(xing)，可(ke)(ke)(ke)以將(jiang)金(jin)屬(shu)螯合在(zai)細胞(bao)表面(mian)；微生物(wu)(wu)(wu)(wu)(wu)可(ke)(ke)(ke)以改變根系微環境，從(cong)而提高植(zhi)物(wu)(wu)(wu)(wu)(wu)對(dui)重(zhong)金(jin)屬(shu)的(de)吸收，揮發或(huo)(huo)固(gu)定(ding)效(xiao)率。

4 結語

目前，我國農(nong)田土(tu)(tu)壤(rang)重(zhong)金(jin)屬(shu)污染情況(kuang)相當嚴峻。由于重(zhong)金(jin)屬(shu)的(de)(de)(de)不可逆轉(zhuan)性，及其(qi)在(zai)食(shi)物(wu)鏈中(zhong)的(de)(de)(de)累積已引(yin)起(qi)廣泛關注，重(zhong)金(jin)屬(shu)已被列入優先控(kong)制的(de)(de)(de)污染物(wu)之(zhi)一。土(tu)(tu)壤(rang)污染導致其(qi)他(ta)環境問題(ti)。土(tu)(tu)地受到(dao)(dao)污染后，含重(zhong)金(jin)屬(shu)濃度較高的(de)(de)(de)污染表層土(tu)(tu)容易在(zai)風力(li)和(he)水(shui)力(li)的(de)(de)(de)作用(yong)下(xia)分別進入到(dao)(dao)大(da)氣和(he)水(shui)體中(zhong)，導致大(da)氣污染、地表水(shui)污染、地下(xia)水(shui)污染和(he)生態(tai)系統退化等其(qi)他(ta)次(ci)生生態(tai)環境問題(ti)。因此土(tu)(tu)壤(rang)污染防治極為重(zhong)要(yao)(yao)，應(ying)以源(yuan)頭(tou)控(kong)制，即有(you)效地降低污染物(wu)的(de)(de)(de)排放，這主要(yao)(yao)有(you)賴于國家(jia)環境政策(ce)與法規的(de)(de)(de)不斷完善和(he)工礦企(qi)業技術(shu)革新的(de)(de)(de)落實；在(zai)土(tu)(tu)壤(rang)污染防治的(de)(de)(de)技術(shu)層面，即污染土(tu)(tu)壤(rang)的(de)(de)(de)修(xiu)復(fu)。將(jiang)物(wu)理、化學、生物(wu)等修(xiu)復(fu)手段綜合起(qi)來處(chu)理污染問題(ti)將(jiang)是重(zhong)金(jin)屬(shu)污染修(xiu)復(fu)技術(shu)的(de)(de)(de)發展方(fang)向之(zhi)。

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