Tag chi phdn tich Hog Ly vd Sinh hgc - Tap 19, Sd 3/2014
DANH GIA Mirc DO 6 NHIEM ASEN TRONG CAC VUNG 6 NHIEM C H A T DA CAM/ DIOXIN VA PHU CAN TAI SAN BAY BIEN HOA
Din toa sogn 21 - 3 - 2013
Pham Thi Ngoc Mai
Khoa Hda hgc, Dgi hgc Khoa hgc Tu nhiin, Dgi hgc Qudc Gia Hd Ndi Nguyin Hiing Minh, NguySn Van Thu*ng
Phdng thi nghiim Dioxin, Cue mdi tru&ng Viet Nam
SUMMARY
EVALUATION OF ERSENIC CONTAMINATION AT AGENT ORANGE/DIOXIN CONTAMINATED AREAS AND VICINITY AT BIEN HOA AKBASE Soil, sediment, surface water and ground water samples were collected at dioxin contaminated areas and vicinity at Bien Hoa airbase and analyzed by HVG-AAS method to evaluate the arsenic contamination level. Results show that among 25 soil and sediment samples, 13 samples have As concentrations from 1.1 to 21 times higher than allowance level. Most of them are sediment samples or soil samples taken from dioxin contaminated areas. The concentration of As in surface water and ground water were found to lie below the allowance level for groundwater (0.05 mg/L) but some samples exceed the allowance level for drinking or domestic water (0.01 mg/L).
The distribution of As concentration in water and sediment has a correlation: areas having low As concentrgtion in sediment samples also have low As concentration in water. The contamination of As in soil, sediment and water might be originated from the Blue agent that American army used during Vietnam War, next to the natural origin and domestic activity.
This study has pointed out the possible risk of As contamination to areas and residence in the vicinity of Bien Hoa airbase, and might form a base to select a suitable dioxin remediation technology that also can remediate As In those places.
1. Gidi THIEU CHUNG chit Da cam chilm khoang 50% cdn lai Trong giai doan chien tranh tir 1961- la cac chat khac vi dy nhu chit Tring 1971, quan dpi My sir dung khoang 80 24%, chit Xanh 6,5%. Trong dd, thanh trieu lit chit ddc gay trui la. Trong dd, phan chinh cua chit Xanh la
Dimethylarsinic acid (Vilt tit la DMA - Cdng thiic hda hgc la (CH3)2AsOOH), chat Xanh dugc bilt tdi vdi tac dung diet cd manh. Khi su dyng vdi lilu lugng cao, chit nay cd tac dyng vdi ca lua va cac loai cay hoa mau khac. Mac dil As d dang hiru co it ddc han so vdi dang vd co nhung frong ty nhien, dang hiru CO cua asen cd the b] chuyen thanh dang vd co khi cac cau oxy va cacbon bi phan buy va cd ddc tinh cao hon nhieu lin [1].
Theo mdt nghien ciiu gin day, khi phan tich dioxin trong mdt sd miu ily tai cac khu vuc d nhiem dioxin tai cac san bay Bien Hoa, Da Nang va Phil Cat, ciing ddng thdi phat hien thiy ham lugng Asen kha cao, vugt qua quy chuan Viet Nam cho cac loai dat thdng thudng (12 mg/kg) [2]. Mdt trong nhGng gia thiet cd eg sd ve ngudn gdc d nhiem As tai cac viing ndng la do viec sir dung chat diet cd cd thanh phan la Cacodylic axit (hay cdn gpi la Dimethylarsinic axit) frong "Chit Xanh" [2]. As cd the b] hda tan dl dang ban la dioxin va do dd lan truyin d nhilm trong pham vi rpng ban.
v l cdng tac xu ly, nlu cac cdng nghe chi loai trir dugc dioxin thi sau khi xii ly dit cd thi vin chua dupc coi la da sach vi cdn ham lugng As cao. Ben canh dd cdn tdn tai nguy co gay phat thai d nhilm As thir cap do qua frinh ddt ndng cd thi lam As hda hoi va thoat
ra khdng khi. Chinh vi vay, viec trien khai nghien cuu mirc dp d nhiem As lai cac vimg ndng la hit su:c cin thiet ca ve mat khoa hpc va y nghia thuc tien.
2. THU'C NGHIEM 2.1. Hoa chat va thiet hi
Cac hda chat loai tinh khilt phan tich (p.a): Axit nifric dac (65%), Axit hydrochloric, Axit H2S04,NaOH, NaBH4, KI, Dung dich asen chuan gdc (1000 mg/l) (Merck), nudc cit hai lin.
May quang phd hap thu nguyen tu Analyst 800 cua hang Perkin Elmer, Thiet bi sinh khi hydrua FIAS 100 cila hang Perkin Elmer va cac dung cu thuy tinh khac.
2.2. Lay mau vii bao quan mau Tien hanh lay mau dat va nudc d mgt sd khu vuc xung quanh san bay Bien Hda (xem ban do lay mau trong Hinh 1).
Mau dat bao gdm ca dat bS mat va theo chieu sau. Viec trdn man d cac dp sau khac nhau (0-200cm) dugc tien hanh d hien trudng. Mau sau khi trdn deu dugc chia lam 2 phan (mdi phan khoang 300- 500g). Man nudc bao gdm ca nudc be mat va nudc ngam, Trong mdt so truimg hgp mau nudc dugc lay d gilng khoan cua nha dan, Cac man nudc duoc axit hda ngay tai hien trudng bing HNO3 (1:1) dl dua pH ciia miu <2. Cac miu dugc bag quan lanh d 4°C, frong thdi gian 30 ngay kl tir ngay liy miu.
Hinh 1. Bdn do khu vuc lay mdu tgi sdn bay Bien Hoa 2.3. Phircmg phap phan tich
Tien hanh xac dinh ham lugng Asen trong cac mau dat/ tr4m tich va nuoc bang phuong phap quang pho hap thu
nguyen ti> (HVG-AAS). Qui trinh phan tich mau nuoc va mau d^t dugc torn tit trong hinh 2.
50 ml nuac
- 7inl H2S04 + 5 HN03 diic - dun soi nhe
Mau
20 ml
-nghien nho, Ipt silng 0^5 m - dong nh^ mlu
1,0 g mau
•^ 25 ml H20 cat - dun soi den xudt hien khi tring
10 ml
+ 6 ml HCI 37%
+ 2ml65%HN03 + ChiSlvis6ng/20.30' + to ph6ng + loc
- to phong
- mo cit 50 ml
Dung djch Can tan
10 ml 50 ml
-1.6mIHCIdac+lmIKI - Day chat nip + dun each thii)/25' -10 phong
10 ml
HVG-AAS
+ 4ml37%HClHmireKl 4-600010'
HVG-AAS
(a) (b)
Hinh 2 So dd qui trinh phdn tich As trong (af mdu nu&c; (b) mdu ddt
2.4. Phirong phap do HVG-AAS As(V) trong raau phan tich dugc khu ve As(III) bang KI va dugc dua vao bo FIAS de hydrua hoa va ket noi vol may quang pho hap thu nguyen tu Analyst 800. Xay dung duong chuan a cac dieu kien phan tich g6m: Den: EDL; Dong den: 380 mA; Buoc song: 197,3 nm;
Khe sang: 0,7 mn; Bg nguyen tii hoa mlu: Cuvet thach anh; Ngon liia: C2H2 - Khong khi
Giai han phat hien cua phuong phap la 1,2 jig/L. Gioi han dinh Iugng cua phuong phap la 3,8 ^xg/L.
2.5. Dam bao chat Ivoug va Idem soat chat Iirang
Viec dam bao chit lugng va kilm soat chat lugng dugc thuc hien bang each su dung mlu lap hien truong, hai mau trSng trang nia dung cu, mgt mlu liy vao ngay dau tien va mgt mau Ifiy vao ngay cuoi ciing trong qua trinh lay mlu.
Cac miu trang nia dugc phan tich de
xac dinh miic do nhiem cheo giua cac diem lay mau voi nhau va giua tat ca cac mau vdfi nhau. Mgt mau trang van chuyen se dugc thu thap tir liic bat dau lay mau va dugc sap xep chung voi cac mau khac, sau do giri den phong thi nghiem de phan tich.
3. KET QUA VA THAO LUAN 3.1. Ham lirgng As trong cac miu bun, d i t va tram tich
25 mau dat, bun va tram tich lay tai cac dia diem thugc khu vuc san bay Bien Hoa da dugc tien hanh phan tich ham lugng As. Ket qua cho thay ham lugng As dao dgng trong khoang tu 1,12 mg/kg den 117 rag/kg tuy theo vi tri lay mau. Cac ket qua nay dugc bieu di^n tren Hinh 3 va so sanh voi gidi han cho phep ve ham lugng asen theo QCVN 03:2008/BTNMT- Quy chuin ky thuat quoc gia ve giai han cho phep ciia kim loai nang trong dat la 12 mg/kg dat kho.
^ 3 0 0 JC 250 D)
O) S2OO
< 150 Ol
t
ioo— 50
L
12 mg/kgHinh 3. Biiu dd hdm lugng asen trong cdc mdu biin. ddt, trdm tich tgi khu vuc sdn bay Bien Hod
Tit cac kit qua thu duoc nhan tha)-. ham bin, dat va tram tich ily tai cac dia luong As frong 13 tren tdng sd 25 mau diem thuoc san bay Bien Hda vugt tir
1,11-21 lan ngudng cho phep. Hiu hit trong sd nay la mau fram tich va mau dit ily tai khu vuc cd lien quan den d nhilm dioxin trade day. Dieu nay cho thay cac mau dit tai khu vuc hen quan din d nhiem dioxin trudc day ddng thdi hi d nhilm asen kha cao va da cd hien tuong nia frdi, lan truyen d nhiem sang ngudn nudc va fram tich tai cac khu vuc lan can.
3.2. Hiim lu'ong Asen trong cac mau nirdc be mat va nirdc ngam tai cac
dia diem thuoc khu vyx: san bay Bien Hda
• Mdu nu&c be mat
Cac ket qua ve ham lugng asen frong cac mau nudc be mat lay tai mgt sd dja diem thudc khu vuc san bay Bieu Hda dugc bieu dien fren dd thi Hinh 4 va so sanh vdi gidi han cho phep ve ham lugng asen cho nudc bl mat va nudc an udng ciia Viet Nam tuong iing la 0,02 va 0,01 mg/L.
_ 0.025
» 0.02
= 0,015
t, "<"
& 0,005
0,02 m g / l
I
0,01 m g / l c*''Ten mau
c* . ^ . ^
Hinh 4; Bieu do hdm lugng asen trong cdc mdu nu&c bi mat tgi khu vuc sdn bay Biin Hda
Ket qua cho thay, ham lugng As frong cac mau nudc be mat tai cac dia diem thudc san bay Bien Hda tuy da sd cac mlu phan tich cd ham lugng Asen xlp xi xung quanh gia fri ngudng cho phep theo QCVN 08:2008/ BTNMT la 0,02 mg/L nhung neu so vdi ngudng gidi han ve nudc an udng (frong trudng hgp ngudn nudc nay dugc su dung true tilp cho an udng hoac lam ngudn nudc cho cac nha may san xuat nudc sach diing
cho an udng) theo QCVN 01:2009/BYT la 0,01 mg/l thi miic do nil ro d nhiem asen tai cac khu vuc nay la cd.
• Mdu nu&c ngdm
Cac ket qua ve ham lugng asen frong 17 mau nudc ngam ily tai mgt sd dia diem thudc khu vuc san bay Bien Hda dugc bieu dien tren Hinh 5 so sanh vdi ham lugng cho phep ve As ddi vdi nudc ngam va nudc an udng tucmg ling la 0,05 va 0,01 mg/l.
^ 0 . 0 6
J , 0.04
< 0,03 - g'o.Oi
^ 0.01
S^^^^^^^^^^^^^^^^^^A^
Hinh 5: Hdm lugng As trong mdu nu&c ngdm tgi cdc dia diim thupc khu vuc sdn bay Bien Hda
Chi cd 02 frong sd 17 mau nudc ngam lay tai khu vuc san bay Bien Hda vugt ngudng gidi han ve ham lugng As trong nudc to udng (0,01 mg/l) va 01 mlu cd ham lugng As xap xi ngudng gidi ban ve ham lugng As trong nudc nglm (0,05 mg/l). Ket qua nay cho thiy hien trang nudc ngam tai khu vyc nay chua hi anh hudng nhieu bdi su lan truyen d nhiem As tir cac vimg ndng d nhiem dioxin va ngudn thai cac thudc diet cd do My sii: dung frong chien franh d Viet Nam trade day. Tuy nhien, can cd ngay cac bien phap xii ly va ngan ngua kha nang lan truyen d nhiSm nay nham dam bao an toan cho khu vyc san bay va dan cu xung quanh.
Nguon gdc cua asen frong cac mau nudc bao gdm d nhiem asen tryc tiep tit ngudn phat thai chat d nhiem (asen cd frong thanh phan ciia thudc diet cd ma quan dpi My sii dung frong chiln franh d Viet Nam trade day) tai cac khu vyc d nhiem dioxin va xam nhiem tir dat (asen v6n la thanh phin ty nhien cua Idp fram tich vd frai dat nen nd thudng cd mat trong cac tang nudc ngam va nudc mat tuv chi d ham lugng thap khotog vai Mg/I). Su phan huy cua chit hiru co
dudi tac dung cua vi sinh vat yem khi.
Cling la mdt frong cac nguyen nhan giai phdng As tir dat vao nudc [3,4].
Da sd cac kit qua cho thiy ham lugng As frong nudc be mat va nudc ngam nhd ban so vdi ham lugng As xac djnh dugc frong cac mau dat va fram tich tai cac dia diem thudc khu vuc san bay Bien Hda. Dieu nay hoan toan hgp ly bdi ham lugng As trong dit/ fram tich da dugc tich luy trong mdt thdi gian dai. Sy phan bd ham lugng Asen frong nudc va trong fram tich ciing cd mdi tuong quan vdi nhau: tai cac khu vyc ham lugng As thap thi trong mau tram tich ciing thap hon so vdi cac khu vyc khac. Tdn du As trong d§t cd thi din tdi viec chiing bi hda tan va lan truyin vao nudc mat, nudc ngam va gay nen d nhiem cho ngudn nudc.
4. KET LUAN
Cac ket qua khao sat ham lugng Asen frong cac mau dit/ tram tich (mlu dit be mat va mau dat theo do sau) va nudc (nudc be mat va nudc ngam) tai cac dia diem tai vung d nhilm dioxin tai san bay Bien Hda cho thiy mgt sd dja dilm d nhiem Asen, vugt qua gidi han cho phep theo quy chuln Viet Nam (12 mg/kg). Ham lugng Asen trong cac mlu
nuoc mat va mlu nuoc ngam tai cac dia diem quanh san bay Bien Hoa xac dinh dugc la duoi gioi han cho phep doi vcri tieu chuan nuoc ngam (0,05 mg/l). Tuy nhien, neu so vai tieu chuan cho nuoc uong va sinh hoat cua Viet Nam (0,01 mg/l) thi lai tiem an ngu>' ca rui ro voi con ngucri do mgt so hg dan 6 day co thoi quen su dung nguon nuoc ngam cho muc dich an uong va/hoac sinh hoat.
Su phan b6 ham lugng Asen trong nuac va trong tram tich ciing co moi tucmg quan voi nhau: tai cac khu vuc ham Iugng As thap thi trong mau tram tich ciing thap hon so vcri cac khu vuc khac do su hoa tan va lan truyen cua Iugng ton du As trong dat vao nuac ngam, nuoc mat va gay nen 6 nhiem cho nguon nuac. O nhiem As trong cac mau dat, tram tich va nuoc co the bat nguon true tiep tu thuoc diet co do quan dgi My su dung trong chien tranh Viet Nam, ben canh nguon goc tu nhien va cac hoat dgng kinh te dan sinh. Nghien Cliu nay buac diu da chi ra nguy co rui ro 6 nhiem As doi vai khu \irc va dan cu song xung quanh san bay Bien Hoa.
Tir do cho thay viec can thiet phai co nhutig nghien cuu sau va rgng hon nua ve miic do 6 nhiem As, cOng nhu giai phap lira chgn cong nghe xur ly dioxin phai di kem de d6ng thai xu ly As tai hai khu virc nay noi rieng va cac khu vuc lien quan den 6 nhiem dioxin noi chung hoac 6 nhiem As thii cap do lan truyen tir cac viing nong tai cac khu vuc Ian can.
Ldi cam on
Nghien ciiu nay dugc thuc hien boi Du an Phong thi nghiem Dioxin (Tong cue moi truang Viet Nam) va Khoa Hoa hgc, Truang Dai hgc Khoa hgc tir
nhien, Dai hgc Quoc gia Ha Ngi. Kk qua nghien ciiu nay la mgt phan trong de tai nghien cuu khoa hgc KHCN- 33.01/11-15 thugc Chuong trinh KH&CN trgng diem cap Nha nuoc giai doan 2011-2015 ve nghien ciiu khac phuc hau lau dai chat dgc da cam/
dioxin do My sii dung trong chien tranh doi vdi moi trucmg va sue khoe con nguoi Viet Nam. Tac ^ a bai bao ciing xin tran trgng cam on ThS. Biii Hong Nhat va ThS. Nguyen Nhu Tiing (Trung tam Quan trac Moi tnrong, Tong cue Moi trucmg) ve nhtrng hd trg ki thuat qui gia.
TAI LIEU THAM KHAO 1. Shahida Q, Dibyendu S, Rupali D, Changes in arsenic fractionation, bioaccessibility and speciation inorgano-arsenical pesticide amended soils as a fimction of soil aging, Chemosphere, Vol. 84, pp. 1563- 1571(2011).
2. Hang N M, Saito M, Truong N X, Minh N H, Son L K, Co-Contamination of soil with dioxin and asenic at former military airbases in Vietnam, The 3T^
Dioxin Symposium, 26-31 August, Cairns, Australia; (2012).
3. Kumud C. Saikia and Susmita Gupta, Assessment of surface water quality in an arsenic contaminated village, American Joumal of Environmental Science, Vol. 8 (5), pp. 523- 527(2012).
4. Pauline L. Smedley and David G.
Kimiiburgh,United Nations Synthesis Report on Arsenic in Drinking- Water,BriYts/i Geological Survey, WaUingford, Oxon OXIO 8BB, U.K(2013).
