重慶環保監測分享地球物理方(fang)法(fa)在土(tu)壤污染調查(cha)中的(de)應用(yong)

在傳統的(de)(de)(de)場地(di)(di)調查(cha)中(zhong)往(wang)往(wang)通過鉆孔取(qu)(qu)樣或者(zhe)現場探(tan)測(ce)(ce)(薄(bo)膜界面探(tan)測(ce)(ce)器)來獲取(qu)(qu)地(di)(di)下(xia)污染物(wu)的(de)(de)(de)濃度(du)信息，并通過平(ping)面或空間插值的(de)(de)(de)方法推測(ce)(ce)污染物(wu)的(de)(de)(de)分布情(qing)況。本文介(jie)紹幾種地(di)(di)球物(wu)理(li)勘探(tan)方法在土壤(rang)污染修(xiu)復調查(cha)中(zhong)的(de)(de)(de)應用;地(di)(di)球物(wu)理(li)勘探(tan)可通過非破壞性(xing)的(de)(de)(de)方式對地(di)(di)下(xia)污染物(wu)的(de)(de)(de)分布情(qing)況進行直接測(ce)(ce)量，并獲取(qu)(qu)連續(xu)性(xing)剖面數(shu)據。一般包括探(tan)地(di)(di)雷達、高密度(du)電法、感應電磁法等(deng)。

1、探地雷達

探(tan)(tan)(tan)(tan)(tan)(tan)(tan)地(di)(di)雷(lei)達(da)是利用(yong)(yong)高(gao)頻(pin)(pin)電(dian)(dian)磁(ci)波(bo)(bo)束對地(di)(di)下目標進(jin)(jin)行(xing)探(tan)(tan)(tan)(tan)(tan)(tan)(tan)測(ce)(ce)的(de)一(yi)種方(fang)法，其(qi)使(shi)用(yong)(yong)的(de)電(dian)(dian)磁(ci)波(bo)(bo)頻(pin)(pin)率(lv)(lv)一(yi)般(ban)為0.01~1GHz，通過地(di)(di)面上布置的(de)發射(she)天(tian)線激發并傳入(ru)地(di)(di)下，當(dang)地(di)(di)下土壤介質(zhi)的(de)巖性(xing)、化學性(xing)質(zhi)等(deng)發生改變時(shi)，部分高(gao)頻(pin)(pin)電(dian)(dian)磁(ci)波(bo)(bo)能(neng)量(liang)會(hui)反射(she)回來，并被天(tian)線接收，從而探(tan)(tan)(tan)(tan)(tan)(tan)(tan)得地(di)(di)下目標情(qing)況。當(dang)有機污(wu)染物侵入(ru)到土壤環(huan)境(jing)中時(shi)，由于其(qi)介電(dian)(dian)常數的(de)差異(yi)，導致(zhi)(zhi)被污(wu)染土壤電(dian)(dian)性(xing)發生改變，在探(tan)(tan)(tan)(tan)(tan)(tan)(tan)地(di)(di)雷(lei)達(da)上即(ji)表現為電(dian)(dian)磁(ci)反射(she)信號的(de)異(yi)常，對場地(di)(di)進(jin)(jin)行(xing)掃描，通過數據(ju)分析即(ji)可獲得地(di)(di)下污(wu)染物分布情(qing)況。但是由于其(qi)電(dian)(dian)磁(ci)波(bo)(bo)頻(pin)(pin)率(lv)(lv)較高(gao)，導致(zhi)(zhi)穿透能(neng)力較低(di)，因此限制了探(tan)(tan)(tan)(tan)(tan)(tan)(tan)地(di)(di)雷(lei)達(da)對地(di)(di)下污(wu)染物探(tan)(tan)(tan)(tan)(tan)(tan)(tan)測(ce)(ce)的(de)深(shen)(shen)度(du)，探(tan)(tan)(tan)(tan)(tan)(tan)(tan)測(ce)(ce)深(shen)(shen)度(du)因土壤介質(zhi)導電(dian)(dian)率(lv)(lv)、介電(dian)(dian)常數而異(yi)，在0.1m~30m范圍內。同時(shi)探(tan)(tan)(tan)(tan)(tan)(tan)(tan)測(ce)(ce)精度(du)(分辨率(lv)(lv))及深(shen)(shen)度(du)與探(tan)(tan)(tan)(tan)(tan)(tan)(tan)地(di)(di)雷(lei)達(da)所采(cai)用(yong)(yong)的(de)電(dian)(dian)磁(ci)波(bo)(bo)頻(pin)(pin)率(lv)(lv)有關(guan)，頻(pin)(pin)率(lv)(lv)越(yue)高(gao)，分辨率(lv)(lv)越(yue)高(gao)，探(tan)(tan)(tan)(tan)(tan)(tan)(tan)測(ce)(ce)深(shen)(shen)度(du)越(yue)低(di)，頻(pin)(pin)率(lv)(lv)越(yue)低(di)，分辨率(lv)(lv)越(yue)低(di)，探(tan)(tan)(tan)(tan)(tan)(tan)(tan)測(ce)(ce)深(shen)(shen)度(du)越(yue)深(shen)(shen)。

2、高密度電法

高密度電(dian)(dian)(dian)法(fa)(fa)是(shi)根據(ju)不(bu)同(tong)介質(zhi)導(dao)電(dian)(dian)(dian)性能差異(yi)測得地(di)下(xia)(xia)目(mu)標分布情(qing)況的(de)方法(fa)(fa)，通過(guo)地(di)表(biao)布設(she)的(de)電(dian)(dian)(dian)極向(xiang)(xiang)地(di)下(xia)(xia)輸(shu)出電(dian)(dian)(dian)流，當地(di)下(xia)(xia)介質(zhi)電(dian)(dian)(dian)阻(zu)率發(fa)(fa)生改(gai)變(bian)(bian)時(shi)，電(dian)(dian)(dian)流強弱即(ji)發(fa)(fa)生改(gai)變(bian)(bian)，地(di)表(biao)布設(she)的(de)測量電(dian)(dian)(dian)極可(ke)(ke)測得相鄰電(dian)(dian)(dian)極間(jian)電(dian)(dian)(dian)勢(shi)差，進而反映地(di)下(xia)(xia)電(dian)(dian)(dian)阻(zu)率變(bian)(bian)化(hua)情(qing)況，z終(zhong)探得地(di)下(xia)(xia)目(mu)標分布情(qing)況。有機污染(ran)物(尤(you)以含油污染(ran)物為(wei)主)侵入土壤后(hou)，土壤的(de)電(dian)(dian)(dian)阻(zu)率會(hui)發(fa)(fa)生改(gai)變(bian)(bian)，通過(guo)高密度電(dian)(dian)(dian)法(fa)(fa)即(ji)可(ke)(ke)測定其(qi)分布情(qing)況，此(ci)外(wai)污染(ran)物濃度差異(yi)也會(hui)導(dao)致導(dao)電(dian)(dian)(dian)特性的(de)變(bian)(bian)化(hua)趨(qu)勢(shi)存在差異(yi)：飽和情(qing)況下(xia)(xia)，電(dian)(dian)(dian)阻(zu)率先增后(hou)去向(xiang)(xiang)穩定，不(bu)飽和情(qing)況下(xia)(xia)，電(dian)(dian)(dian)阻(zu)率先增后(hou)減(jian)，后(hou)趨(qu)向(xiang)(xiang)穩定。

3、感應電磁法

感(gan)應(ying)電(dian)(dian)磁(ci)法即利用電(dian)(dian)磁(ci)感(gan)應(ying)原理來(lai)探(tan)測(ce)(ce)地(di)(di)下目標，探(tan)測(ce)(ce)時在地(di)(di)表向(xiang)發射線(xian)圈(quan)通(tong)可變頻率交流(liu)電(dian)(dian)，從而(er)(er)產生(sheng)(sheng)原生(sheng)(sheng)磁(ci)場(chang)，原生(sheng)(sheng)磁(ci)場(chang)在地(di)(di)層中(zhong)產生(sheng)(sheng)渦(wo)電(dian)(dian)流(liu)，而(er)(er)電(dian)(dian)流(liu)密(mi)度(du)(du)取決于電(dian)(dian)阻率，由渦(wo)電(dian)(dian)流(liu)產生(sheng)(sheng)次(ci)生(sheng)(sheng)磁(ci)場(chang)，在地(di)(di)表，接受線(xian)圈(quan)即可測(ce)(ce)得(de)(de)(de)次(ci)生(sheng)(sheng)磁(ci)場(chang)強度(du)(du)，進而(er)(er)探(tan)得(de)(de)(de)地(di)(di)下目標分布情(qing)(qing)況。污染物侵入土壤(rang)造成電(dian)(dian)阻率改變，通(tong)過感(gan)應(ying)電(dian)(dian)磁(ci)法即可測(ce)(ce)定其分布情(qing)(qing)況。此外(wai)，發射線(xian)圈(quan)與接收線(xian)圈(quan)圈(quan)面角度(du)(du)不同，可做兩種方(fang)(fang)(fang)式測(ce)(ce)量，即線(xian)圈(quan)面同時平(ping)行地(di)(di)表的(de)垂直(zhi)偶(ou)極展開(kai)，與圈(quan)面沿測(ce)(ce)線(xian)方(fang)(fang)(fang)向(xiang)且(qie)垂直(zhi)地(di)(di)表的(de)水平(ping)偶(ou)極展開(kai);垂直(zhi)偶(ou)極的(de)探(tan)測(ce)(ce)深度(du)(du)較深，容(rong)易獲(huo)得(de)(de)(de)垂直(zhi)方(fang)(fang)(fang)向(xiang)的(de)電(dian)(dian)性變化情(qing)(qing)形，水平(ping)偶(ou)極的(de)探(tan)測(ce)(ce)深度(du)(du)較淺，容(rong)易獲(huo)得(de)(de)(de)側(ce)向(xiang)方(fang)(fang)(fang)向(xiang)的(de)電(dian)(dian)性變化情(qing)(qing)形。