Nguy cơ ô nhiễm Asen (thạch tín) trong nước giếng khoan tại một số vùng thuộc đồng bằng Bắc Bộ

O NHlfiM ASEN TRONG NV6C GifiNG KHOAN 0 nhiem asen trong nUdc ngam da diidc phat hien tai nhieu quo'c gia tren the gidi, nang n h a t la 6 Bangladet va vung Tay Bengal ciia An Do, theo

NGUY cop NHIEM ASEN (THACH TIN) TRONG

NJOC GIENG KHOAN TAI MOT SO VUNG THUOC DONG B A N G BAG B O

P h a m Thi K i m T r a n g , N g u y e n V a n Mui

Khoa Sinh hoc, TrUdng DHKHTN, DHQGHN

V i T h i M a i L a n , N g u y § n T h i M i n h H u e ,

B u i H o n g N h a t , T r a n T h i H a o , P h a m '

T h i D a u , V u T h i M a i , P h a m H u n g V i e t

Trung tdm NC Cong nghe Moi trudng vd * Phdt trim Ben vUng, TrUdng DHKHTN, DHQGHN

M i c h a e l B e r g , J a n R V a n D e r M e e r

Vien Khoa hoc vd Cong nghe Moi triCdng, Lien bang Thuy Si

1 O NHlfiM ASEN TRONG NV6C GifiNG KHOAN

0 nhiem asen trong nUdc ngam da diidc phat hien tai nhieu quo'c gia tren the gidi, nang n h a t la 6 Bangladet va vung Tay Bengal ciia

An Do, theo Udc tinh cua Tien si Chakraborti (An Dp) vao nam 2001 d

do CO khoang 150 trieu ngUdi dan dang phai doi mat vdi nguy cd bi nhiem doc man tinh asen do suf dung nguon nUdc ngam c6 chiia lifdng asen cao hdn 50|lg/l (tieu chuan ve asen trong nUdc uohg cua cac quo'c gia nay) So benh n h a n m i c cac benh lien quan tdi n h i i m doc asen difdc p h a t hien ngay cang nhieu tai cac nUdc noi tren (1,2,3,4,5) Nam

1996 To chiic Y te the gidi da de nghi giam m\ic asen cho phep trong

nxidc uong tii 50|^g/l xu6ngl0|lg/l do doc t m h gay ung t h u cua nguyen

to' hoa hoc nay

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Arsenic (MQ^U

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O 50-150

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Hi/i/i / O nhi^m asen tai Ha Noi (1999)

Nhieu quo'c gia tren the gidi da hudng ling de xuat tren trong do

CO Viet Nam Theo quyet dinh so 1329/2002 cua Bo trUcing Bo Y te ve viec ban hanh Tieu chuan ve sinh niidc an uohg, tieu chuan ham liidng asen trong nitdc cap cho cac khu vUc do thi la lOjO-gA Tuy nhien trong

thdc tien gan 80 % dan so' nUdc ta lai song b cac khu vUc nong thon

chiia CO niidc cap tuf cac nha may loc nifdc chinh quy, nifdc sinh boat chu yeu van dUa vao nguon nU6c ngam thong qua cac gieng khoan do UNICEF ho trd hoac tu xay lap Chat liiOng niidc gieng khoan hien nay van chUa diidc danh gia tren dien rong, nhat la ve cac chi so hoa hoc trong do c6 asen do ban che ve dieu kien phan tich (9)

Xuat phat tu! yeu cau thUc te va hiidng ling noi dung cua chifdng trinh cap nU6c va ve sinh nong thon trong chien lUdc bao ve moi trudng Quo'c gia (2001-2010), Trung tam Nghien ciiu Cong nghe Moi tradng

va Phat trien ben vGng thupc TrUdng Dai hoc Khoa hoc Tu nhien, Dai hoc Quoc gia Ha Noi ket hdp vdi cac nha khoa hoc thuoc Vien Khoa hoc

va Cong nghe Moi trUdng Lien bang Thuy Si tii nam 1999 da tien hanh nghien cvLn khao sat chat lUdng niidc gieng khoan tai mot so' dia

diem thuoc dong bang Bac bo va sU tich luy sinh hoc cua asen trong mau toe cua ngUdi dan song tai khu vUc 6 nhiem cao

Ket qua khao sat ngSu nhien 68 mau nUdc gieng thuoc khu vUc

Ha Noi vdi m a t do lay m i u khoang 10 km / diem dUdc trinh bay trong hinh 1 Ham lUdng asen trung binh do dUdc trong ddt nay la 159 |lg/l,

72% so' mau c6 ham lUdng asen cao hdn 10 |J.g/l N\idc tho chufa loc lay

tuf tang nUdc nong tai ba nha may nUdc cung c6 ham lUdng asen cao den gan 200 |lg/l, tuy nhien qua trinh phun va loc nUdc da loai bo r a t nhieu asen nen h a u het cac nha may nUdc trong noi t h an h da cung cap midc sach dat tieu chuan quo'c gia giai doan do vdi ham lUdng asen nho hdn 50 |lg/l (2,7,8) Cac so lieu thu dUdc ciing cho thay khu vUc ngoai thanh phia Nam Ha Noi c6 bieu hien 6 nhiem cao hdn Trong cac nam 2002-2003 chung toi tiep tuc tien h a n h khao sat ky mot so' dia diem

nhim tim hieu cac yeu to' lien quan tdi qua trinh giai phong asen tii

tram tich ra nvfdc ngam d tang Holocen M^u nifdc gieng khoan dUdc la'y tai xa ThUdng Cat, huyen TCf Liem (phia b^c Ha Noi), xa Hoang Liet va Van Phiic, huyen Thanh Tri (phia nam Ha Noi), doc hai bd song Hong (doan chay qua dia phan Ha Noi), xa Sdn Dong, huyen Hoai Diic (phia tay Ha Noi), mat do lay m i u khoang 0.25 km / diem Ket qua p h a n tich h a m liidng asen b t o g phUdng phap Quang pho hap thu nguyen tuf c6 t u a n thu chat che cac yeu cau ve chat lUdng phan tich dUdc trinh bay trong bang sau:

1 Dia d i e m

ThUdng

Cat

Hoang Liet

Doc hai bd

song Hong

(40km)

Van Phuc

Sdn Dong

N o n g d o

As

t r u n g

b i n h (^lgA)

9

56

82

117

/yh.-ii.Qil'.f ;

Tong so

m a u

20

19

76

21

53

Stf p h a n bo a s e n t r o n g ni:fdc

n g a m (so m a u , p h a n tram)

< 10

l^g/l

18(90%)

4(21%)

32(42%)

6(28%)

0

1 0 - 5 0

|Llg/l 1(5%)

5(26%)

18(24%)

2(10%) 2(4%)

5 0 - 2 0 0

^g/1

1(5%)

10(53%)

15(20%)

8(38%)

20(38%)

> 200

l^g/l

0

0

11(14%)

5(24%) 31(58%)

Cac so' li§u thu diidc cho th§'y miic do asen c6 mat trong nifdc gieng khoan la rat khac nhau giiia cac xa va ke ca trong mot xa, gia

tri do dUdc bien thien tii < 1 |J.g/l den gan 500 ^Xg/l, vi du 90% so m l u

tai xa ThUdng Cat c6 ham lUdng asen nho hdn 10 j^g/l con ci Sdn Dong

la 0% Trong so' cac xa c6 bieu hien 6 nhiem asen thi Sdn Dong bi 6 nhiim nang ne nhat vdi ti le 100% so' mau khao sat c6 lUdng asen cao hdn tieu chuan cho phep la 10 |ag/l, dac biet c6 tdi 58%;s6'mSu cao hdn

200 |ig/l, do la mtfc rat nguy hiem neu ngufdi dan sii dung trUc tiep

nUdc nay khong qua loc de an uong Theo cac ket qua tong ket cua To chute Y te The gidi, h^u het cac benh n h a n c6 bieu hien lam sang nhiem

doc asen ro cl An Do va Bang Ladet da s\i dung nUdc c6 asen tu: 200

|ig/l trcl len trong khoang thdi gian tii 7-15 nam Tuy nhien n§'u miic

phdi nhiim nho hdn thi thdi gian u benh se dai hdn chti khong phai la khong hi anh huSng Van Phuc ciing la xa c6 tdi 62% so" m^u c6 asen

cao hdn 50 |lg/l, d Hoang Liet la 53%

500

400

300

200

100

<r

Vanphuc Hoangliet Thuongcat Sondong

Diem lay m i u

Hinh 2 Sir phan bo ciia nong do asen trong nude gieng tai tiimg xa (2002- 2003)

Khi xet su phan bo cua asen trong nUdc nggtm tai titng xa ta cung thay sU bien dong rat khac nhau (hinh 2), Tai Hoang Liet, ludng asen

nam trong khoang tii 50 den 130 [igA (trung binh 56 |J.gA), tai Van Phiic

tijf <1 den 350|lg/l (trung b i n h l l 7 |ig/l), con Sdn Dong tiif 30- 450 |ig/l

(trung binh 251 |ig/l) Cac mau nxidc ng§m doc song Hong c6 ham

lUdng asen dao dong tilt <1 den 500 |J.g/l (trung binh 82 |J.g/l), hau het cac mau c6 liidng asen cao nam d ca 2 bd phia nam Ha Noi Su phan

bo' khong dong n h a t nhxi kieu nay ciing da dUdc phat hien d nhieu ndi

khac tren the gidi (6,10)

Tom lai ket qua dieu tra trong 5 nam qua ciia chung toi cho thay

sU 6 nhiem asen trong nUdc gieng khoan la c6 thuc, d mot so' khu vUc rat dang bao dong, nguy cd 6 nhiem asen da ro ret tai nhieu khu vUc

thuoc dong bang chau tho song Hong Tuy nhien, s\i phan bo' cua asen

trong nu!dc gieng khoan la khong dong deu, tai cac khu vUc nhin chung

CO nong do asen thap vkn xuat hien nhiing cum gieng c6 mtjfc 6 nhiim

cao va ngiTdc lai Bien do dao dong cua ham lUdng asen trong mot xa ciing CO the r a t Idn nhu d Sdn Dong va Van Phuc Dieu do chi ra r^ng, viec dieu tra chi tiet toan bo vung nong thon dang dung nUdc gieng khoan la r a t c^n thiet de c6 mot biic tranh phan anh dung thUc trang

6 nhiim asen tai tufng khu vile cu the Kho'i lufdng cong viec doi hoi sU

dau til, quan tam xiing dang cua nha n\i6c, cac bo nganh lien quan

ciing nhu sU dong g6p tich cUc cua cac to chiic nhan dao, cac trUdng Dai hoc va Vien nghien ciiu n h i m ciing nhau hoan thien biic t r a n h

tong the quo'c gia ve 6 n h i i n asen trong nifdc ngkm, gop phan dua ra

nhOng giai phap giam thieu tich cue va phu hdp vdi thUc t i i n

2 M t r c DO TICH LUY ASEN TRONG M A U T O C

Sau khi xac dinh dUdc mot so diem c6 nguy cd 6 n h i i m asen trong nguon nUdc sinh boat, chung toi da pho'i hdp vdi cac can bo Y te cua Trung tam Y te d a phong Ha Noi va cac dia phUdng noi tren tien hanh thu thap m i u toe de danh gia miic do tich luy asen trong cd the, d6 la

chi thi sinh hoc thUdng ditdc sii dung trong nghien cxiu n h i i m doc asen

man tinh Cac ket qua thu dUdc se la bang chiSng khoa hoc gdp ph^n vao cong tac giao due truyen thong, nang cao n h a n thiic cua toan xa hoi ve van de cham soc si5c khoe ban dau va an toan ve sinh niidc sinh

boat Chung toi da lay 46 m l u cf xa Van Phuc, 207 m i u d xa Sdn Dong,

45 m&u d xa ThUdng Cat

300

200

100

\s trong nUdc (|ig/l)

• Thugfng <

S V a n B i u

D Sofn Don

-•

Cat

c

g

1 1

As trong toe * 100 (pg/l)

Hinh 3: Ham lifong asen trung binh trong nude gieng khoan va toe (2003)

Cac mau toe dUdc xii ly bang ky thuat 16 vi song va p h a n tich b^ng

quang pho hap thu nguyen tii theo phUdng phap ma so 3052 cua Cd

quan bao ve moi trUdng Hoa Ky (EPA) So' lieu p h a n tich tai ThUdng

Cat (diem doi chiing), Van Phuc va Sdn Dong (diem nghien ciiu) dUdc

trinh bay trong hinh 3.^ Nhin vao gia tri trung binh ta thay c6 mot sU

tUdng quan rat ro gifla ham lUdng asen trong nUdc gieng va trong toe

ngUdi O ThUdng Cat la diem do'i chiing, ham iUdng asen trong nU6c

ngam h^u het deu dat tieu chuan cho phep (trung binh nho hdnlO

|ig/L), ham lUdng asen trong m l u toe la 0,27 mg/kg (0,04-0,84 mg/kg),

so sanh gia tri cua TCYTTG la tu: 0,02-0,2 mg/kg d nhiing ngUdi khong

toe tUdng ling la 0,79 mg/kg (0,01-3,3 mg/kg) va 1,61 mg/kg (0,16-10,36

mg/kg) Tai Sdn dong, 70% so' m^u c6 nong do asen trong tdc Idn hdn

1 mg/kg, dac biet c6 nhiing m l u len den 10 mg/kg Ket qua nay c6 the

so sanh vdi nhfing nghien cUu d Tay Bengan, An Do la ndi bi nhiim

asen nang ne vdi nong do asen trong toe ngUdi dan d khoang 3-10

mg/kg (1,3) Theo TCYTTG, miic asen trong toe cao hdn 1 mgAcg dm

chuan doan la da bi nhiim doc asen man tinh va d nhufng ngUdi khong

bi phdi nhiem asen thi nong do asen trong toe thudng la 0,2 mg/kg

Nhu vay cac so lieu thu dUdc da cung cap nhijfng b4ng chiing rat ro

rang ve mot sU phdi nhiem lau dai vdi asen trong nUdc ciia ngUdi dan

tai mot so'khu vUc nong thon Chung toi r a t mong muo'n cac cd quan

y teed trach nhiem tien h a n h dieu tra phat hien nhutng benh nhan c6 bie'u hien lam sang nhiem doc asen va cung cap bien phap chufa tri kip thdi

0 nhiem asen trong nUdc gieng khoan va nhiing tac hai cua no tdi SLtc khoe ba con nong dan dung nguon nUdc nay la mot hien thUc Su c6' nay da xay ra va kho tranh khoi vi 6 njiiem asen trong nUdc ngam

CO nguon goc tU nhien, ngUdi dan nong thon can nUdc sach de dung hang ngay va can y thiic dUdc moi hiem hoa tdi siic khoe tu! asen de c6 cac bien phap phong tranh Dieu tra tinh trang 6 nhiem asen tren pham vi toan quo'c va cung cap nhufng giai phap giam thieu la nhiing viec lam cap bach hien nay De thUc hien c6 hieu qua nhiem vu dieu tra dien rgng, cac dia phUdng c^n dUdc cung cap can bo ki^m tra nhanh ngoai hien trUdng va dao tao can bo thUc hien Ho trd kinh phi cho nong dan xay be loc cat, be chufa nUdc mUa, tram cap nUdc sach tap trung la nhiing giai phap giam thieu kip thdi va hieu qua trong tinh hinh hien nay

Ldi cdm On: Bdi bdo ndy dMc thitc hien vdi sit ho tr<3 cua de tdi ''Tdng citdng nang lUc trong Nghien ciCu vd Bdo tao ve Khoa hgc vd Cong nghe Moi trUdng d miin Bac Viet nam do Ca quan phdt trien vd hdp tdc Thuy Si (SDC) tdi tra

TAI LIEU THAM KHAO

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Chakraborti "Groundwater Arsenic Co n ta m i na t i o n in Bangladesh and West Bengal, India ", Environmental Health Perspectives, 2000

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1997

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7 Pham HungViet, Tran Hong Con, Nguyen thi Chuyen Budc

dau khao sat nhdm ddnh gia hdm litOng Asen trong nitdc ngam va nUdc cap khu vitc Hd Noi Hoi thao quo'c te ve O nhiem Asen: Hien

trang, tac dong den siic khoe cong dong va cac bien phap phong ngiia Ha noi thang 12-2000

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(2002) Bitac ddu nghien ci2u sit 6 nhiem asen trong nitde ngdm

ngoai thanh Hd Noi Tuyen tap bao cao khoa hoc Tieu ban KH

hen nganh KHCN moi trUdng, TrUdng DHKHTN, DHQG Ha Noi (65-71)

9 UNICEF Vietnam (2002) Arsenic contamination: Vietnam's

pathway to alleviation

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source, behavior and distribution of arsenic in natural waters" Applied Geochemistry, 2002