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D^ tai dupe thuc hidn nham xac dinh su phan bd va miic dp xSm nhi^m asen a vimg mSn, Ig va ngpt a ddng bdng song Ciiu Long ff)BSCL). Kdt qua cho thdy ham lugng asen trong trim tich a vting man va viing \q c6 gia tri trung binh Idn lugt la 10,42 ± 3,1 mg.Kg* va 10,31 ± 4,01 mg.Kg' khae bidt c6 y nghia so vdi viing ngpt la 7,5 ±1,7 mg.Kgl. D4 tai da xac dinh c6 su xSm nhi^m asen viing ciia song ven bidn DBSCL voi miic d0 tang ddn tu noi dia ra ddn cfta sdng ven bidn; tir thuong ngudn ddn ha nguon song Tidn va song Hau. Dac bidt, ham lupng asen cao ban c6 y nghia tai viing bai bdi va vimg ciia song so vdi cdc viing khae. Didu niy cdn dupe nghidn ciiu vd tinh di ddng, su tich tu asen trong dat, nuoc va cac loai thiiy san c6 gia tri trong vimg.
Til khda: () nhiim As, trim tich sdng, dSng bang sdng Cuu Long.
L DAT VAN D^
Vimg ciia sdng, ven bidn thuong la noi tich tu cac chat d nhidm cd ngudn gde tir ndi dia. Trong mdi truong tiiuy sinh, trdm tich cd vai trd quan trgng trong su hdp phu cac kim loai nang, dac bidt la asen
(As), do su Idng dgng cua cac hat la liing va cdc qua trinh cd Udn quan ddn bd mat cac v$t chdt vd ca va htru ca. Sir tich tu kim loai n?lng anh hudng ddn ddi sdng ciia cac sinh vat thiiy sinh, gay anh hudrng ddn sue khde ciia eon ngudi thdng qua chudi thue an.
Trong trdm tich vimg ciia sdng ven bidn giau sunfua va vat chat huu c a Day chinh la noi Idng dgng va luu giu cac chdt d nhidm cd ngudn gde ttr ddt lidn, nhdt la kim loai nang (Zheng etal., 1997; Tam & Wong, 2000 trich trong Defew etal., 2005).
Theo didu ti-a ciia UNICEF, As chii ydu do hoat ddng ciia eon ngudi trong ndng nghidp, cdng nghidp va sinh hoat. Tir dd, cho thdy kha nang xam nhidm As vao mdi trudng ttr nhidn rat Ion. Dae bidt, or cac viing ciia sdng, ven bidn la noi tich tu cac chdt d nhidm cd ngudn gde tii ngi dia. Da cd mdt sd nghidn ciiu As tip trung or viing dat phdn, vimg dd tiij va cac sdng rach chinh viing ven bidn tinh£a Mau (Phuong etal., 1998; Hoa etal., 2004; Nguydn Van Tho, 2007)^
Tuy nhidn, chua cd nhidu nghidn ciiu vd su phan bd va xam nhidm As trong didu kidn sinh fliai khae nhau. Do vay, dd tai "Him lupng As trong trim tich tai cic sdng chinh dSng bing sdng Cuu Long" d\K;>c tiitte hidn nhdm cung cdp dii Udu vd su phan bd As tiieo tiidi gian, khdng gian va muc dd xam nhidm As b vung m ^ , Ig^ va nggt DBSCL.
L VAT L i u VA PHUONG PHAP NGHDI GUI 1. Ndi dtmg nghidn ciiu
- xac dinh pH, EC, chdt hihi eo va As trong mdu trdm tich tai viing nghidn ciiu.
Danh gia st^ khae bidt As or vung nggt, Igr va man theo khdng gian va thdi gian thu mlu. Phan tich mdi tuong quan giiia As vdi pH, EC va chdt huu ca trong trdm tich.
2. Phuong phdp nghidn oiu a. D/a diSm thu miu trim tich
Dd tai tidn hanh thu mlu tram tich trdn cdc sdng rach chinh or vimg man, Igr va nggt vao mua mua va khd. Kdt qua khdo sdt cho thdy, b vung man vao miia khd va miia mua dd man ciia nude dao dgng trong khodng tir 23,5%o ddn 28,9%o, tiimg binh la 26,fttl,39%o CO xu huong tang ttr vimg ciia sdng ddn ciia bidn va ven bidn. 6 vimg Igr, dO m ^ ciing cd xu hudng tang tii sdng r?ich ndi dja ra ddn vimg ciia sdng, dao ddng trong hai miia tu 2%o ddn 1296a vdi tiimg binh 4,2±2,15%o. Trong khi dd, dr vung nggt dd man dao ddng tir 0,l%o ddn 0,2%o. Kdt qua nghidn oiu cho thdy su phan bd dd rtian b 3 vimg sinh thai phii hgp vdi SIX phan bd vimg sinh thai man, Igr va nggt ciia Constantinov (1967) (trich trong Chi cue Mdi trudng Tay Nam bd, 2008).
Mau trdm tich duge thu tai vimg nggt theo hudng tir thugng ngudn ddn gdn ha ngudn sdng Tidn, bao gdm doan kdnh Thap Mudi, kdnh Vinh An, nga ba sdng Ciiu Long, do^n cdu My Thuan, kdnh Bao Kd - Vihh Long; ti-dn sdng H^u d kdnh Vihh Td,
KHOA HOC C 6 N G N G H £
kdnh Ba Thd, rach O Mdn, rach Cai Khd, sdng Cai Rang - Can Tho va sdng Cai Tu b Hau Giang.
Mdu trdm tich or viing Igr (ha ngudn sdng Tidn va sdng Hau) dirge thu tir trong ndi dia ra den ciia sdng thude ha ngudn sdng Hau nhu sdng Dai Ngai, ciia Trdn De, kdnh Quan Ld or Sde Trang va ha ngudn sdng Tidn, bao gdm Rach Sdng-Vinh Kim, Rach Tan Lap-Hidp My huydn Cau Ngang, sdng Cd Chidn xa Long Hda, huydn Chau Thanh thi xa Tra Vinh.
- O vimg man, mdu duge thu theo hudrng tir ndi dia ra vimg cua sdng ven bidn nhu sdng Hd Phong, cira Ganh Hao (giap vdi Bien Ddng); va sdng Ong Trang, ciia sdng 6ng Ddc, sdng Bay Hap va khu vue Bai Boi (giap vdi Bidn Tay).
Sdng da duge tidn hanh thu mdu trong dd tai la cac sdng CO anh hudng true tidp den sinh hoat, giao thdng thuy, cac boat ddng trdng trgt, su phat tridn nghd nudi va khai thac thiiy san b DBSCL.
Hinh 1. Sa dd thu mdu tai v^ng m$n, Igr va nggt b DBSCL
Ghi chu: Dia diSm thu miu b. Phuong phap thu miu
Mdu trdm tich duge thu tai 7 dia didm trong mdi vimg man va Igr. Ridng vimg nggt dugc thu or 11 didm.
Tai mdi dia didm mau duge thu bdng gau day b tang mat (0 - 30 cm), thu 3 mau/dia didm. Mdi mdu thu khodng 3 - 5 vi tri xung quanh trong ban kinh khoang 2 - 5 km va trdn thanh mdt mau dai didn.
Mdu sau khi thu duge chira trong ede hii nhya polyetylen tranh tidp xtic voi anh sang va dugc ky hidu theo quy dinh. Mau dugc phai a nhidt dd phong ddn khi khd, sau dd duge nghidn vd qua ray cd mdt luoi 0,5 mm (Ld Trinh, 1997).
c. Phuong phip phin tich
Mau dugc phan tich tai Khoa Mdi trudng & Tai nguydn Thidn nhidn va Phong thi nghidm Chuydn
sau, truong Dai hgc Cdn Tha. Mau tram tich dugc phan tich theo giao trinh phan tich ciia Trudng Dai hgc Wageningen, HaLan (Houba et aZ,1995).
Xac dinh chat huu co trong d^t (Phuong phap Walkley-Black)
Can chinh xde 0,5 g ddt hoac tram tich sau khi nghidn va ray cho vao binh tam giae. Thdm vao binh 10 ml KzCrzOy IN. Thdm tidp 20 ml H2SO4 dam dac Ide nhe cho ddt vao hda chat trdn lan voi nhau. Dd ydn khoang 30 phiit sau dd cho vao 200 ml nude cat Thdm 10 ml H3PO4 va 1 ml chat chi thi diphenylamin.
- Chudn dd dung dich voi FeS04 IN cho ddn khi dung dich chuydn sang xanh (da trdi). Thdm khoang 0,5 ml FeS04 ddn khi dung dich chuydn sang mau xanh la cay. Thdm 0,5 ml K2Cr207 vao dung dich, tidp tuc chudn do vdi FeS04 cho ddn khi mau xanh bidn mat.
Ddi vdi mau blank, tat cd cdc budc ddu lam gidng nhu trdn nhung chi khde la khdng cd ddt
Xac dinh As trong trim tich (phuong phip AAS- AOAC 986.15)
can khodng 1 g mdu cho vao ede sii cd trang men. Tro hda trong 2 gid or nhidt do 500"C va dd ngudi. Lam udrt vdi 10 gigt nude va cdn than thdm vao 3 - 4 ml HNO3 (1:1), lam bay hoi HNO3 du h-dn hdp didn d 100 - 120"C. Vd ca hda khd tidp tuc ti-ong Id nung khoang 1 gid or 500''C. Dd ngudi, them vao 10 ml HCl (1:1), tiidm vao 0,1 ml 20% KI dd chuydn As^
xuong As^* A^ ydn khoang 2 phiit Tidn hanh mau trdng song song.
Voi dung dich trong binh dinh miic 50 ml, thdm vao 10 ml dung dich La (Lantan) va dinh miie tdi vach. B^ Idng can, gan phdn can. Cdn pha loang vdi dung dich HCl 10% dd dung dich trong mlu ndm trong viing do ciia thidt hi.
^ ° ° « * * ^ ' Vj^xC^xA Nguydn td (As), ^g/K ™
Trong dd:
- Vd^: thd tich binh dinh muc (ml).
- A: hd sd pha bang.
- C(jo: ndng do do duge trdn may AAS (pg.L'0.
- m: khoi lugng ciia mau.
d. Phuong phip xAl^sd lidu
- Six dung phdn mdm excel 2003 dd vd dd tiij.
16 NONG NGHIEP vA PHAT TRIEN N O N G THON KY 2 - T H A N G 8/2011
KHOA HQC C 6 H G N G H £
- Sii dung phdn mdm SPSS 13.0 dd xu ly sd Udu.
Kidm dinh Duncan b miic y nghia 5% dd danh gia su khae bidt ham lugng As theo vi tri thu mau. Dimg T- Test dd so sanh su khae bidt As theo thdi gian thu mau.
Phan tich tuong quan giura pH, EC va chat huu CO vdi As trong mdu trdm tich.
DI. KET QUA VA THAO LUAN
1. Asen trong trdm tich vimg man
Ham lugng As trong tram tich dao ddng trong khoang 7,10 - 12,41 mg.Kgl va cao nhat duge tim thay b ciia sdng Ong Ddc va ciia Ganh Hao (hinh 2).
Kdt qua nay chiing to As duge tich tu cao b vimg ciia sdng ven bidn; nghien ciiu cua Nguydn Van Tho (2007) vd ham lugng kim loai nang trong dat tram tich va nude tim thay kdt qua tuong tu. Theo Ld Huy Ba (2000) tram tich chii ydu la biin Idng chiia nhidu kim loai nang va cd hidn tugng keo tu tu nhidn b viing ciia sdng, nen ham lugng kim loai nang b cac viing nay kha cao. Mat khae, tram tich tai cac sdng, rach trong va lan can thanh phd la noi hap phu kim loai nang do chat thai dd thi mang lai. Kdt qua nghidn ciiu ciia dd tai phii hgp vdi nghidn ciiu ciia Spencer et al. (2003); dng cho rdng viing ciia sdng ven bidn tiiudng la noi tich tu va luu giii cac chat d nhidm nhat la kim loai nSng.
Ket qua trinh bay d hinh 2 cho thay, vao iniia khd, ham lugng As trung binh tai tat ca cac diem thu mdu la 11,05 ± 2,83 mg.Kgl; gia tri cao nhat dugc tim thay b cira sdng Ong Ddc, ciia Ganh Hao va thap nhat a Bai Bdi_2. Ham lugng As ti-ong tram tich giua cac didm thu mau trong sdng, rach ndi dia khae bidt khdng cd y nghia thdng kd. Khao sat thuc td cho thdy vimg Bai Boi cd ngudn gde tir su boi ddp phii sa tir sdng va bien va la noi ngap tridu khdng thudng xuydn (Ld Huy Ba, 2000). Day cd tiid la nguydn nhan gay ham lugng As trong dat d Bai Boi thap hon ham l u ^ g As trong trdm tich cua sdng ven bidn. Kdt qua nghidn ciiu cua dd tai phii hgp vdi nghidn ciiu ciia Preda & Cox (2002) cho rdng trong trdm tich cua sdng cd ham lugng As cao ban trong ddt cd ngudn gde tir cua sdng ven bidn.
Ham lugng As cao d cira Ganh Hao cd tiid do day la vimg cua sdng, noi tidp nhan va Idng dgng chdt d nhidm cd ngudn gde hi trong ndi dja (Ld Huy Ba, 2000). Mat khae, theo Gomez-Caminero etal. (2001) d khu vue cira sdng cQng la noi tidp nhan chat d
nhidm do tiiuy tiieu tit bien dua vao qua qua trinh tai huydn phii- lam cho As cd thd bi Idng tu xuong tram tich cira sdng. Theo Brayan & Langston (1992), As thudng di vao vimg cua sdng ven bien do qua trinh phong hda trong tu nhidn. Trong qua trinh trdn lan giira nude mSn va nude nggt lugng Idn As duge hap phu Idn su kdt tua cua cac oxy-hidro-xit sdt ddn ddn su gia tang As trong trdm tich tai vimg cira sdng. Mat khae, kdt qua phan tich ham lugng chat hiiu ca va vat chat la limg ddu cao, vat chat lo lung cd kha nSng hap phu As. Day cd thd la nguydn nhan gay ndn ham lugng As cao tai didm thu mau d cira Ganh Hao.
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Hinh 2. Ham lugng As (mg.KgO trong trdm tich b vimg m^n vao miia khd
Cac ky tu gidng nhau thi khae biit khdng cd y nghia thdng ke bing phep thu Duncan vdi miic y nghia 5%
Ghi chii: ASD: sdng Ong Ddc; AOTR sdng OngTrang; ABB_1;ABB_2: Bai Boi; AHP: sdng Hd Phdng; ABH: cua Bay Hap; AGH: cua Ganh Hao
Bang 1. Trung bmh ham lugng As (mg.Kg^) trong trdm tich dr vimg mjji
Mua Mua kho Mua mua
Trung binh 11,05* ±2,83
9,07* ±2,38
Gii tri s a i k h ^
(P) 0,24
Quy chufa QCVN 03:BTNMT
(mg.Kg') 12
Cic ky tu gidng nhau trong cung mdt cot khae bidt khdng cdy nghia thdng ke bing phep thu T-Test muc y nghia 5%.
Kdt qua trinh bay d bang 1 cho tiiay, ham lugng As trong trdm tich giira miia khd va miia mira khdng khae bidt vdi gia tri As trung binh Idn lugt la 11,05 ±2,83 mg.Kgi va 9,07 ±2,38 mg.Kg' Theo Langston (1985) trich trong Brayan & Langston
(1992) ham lugng As trong trdm tich cira sdng bidn ddng hi 5 mg.Kg' ddn ban 1000 nig.Kg\ trong cac
KHOA HOC C O N G NGHfi cOfa sdng nhu Restronguet hay Cornwall nude Anh
noi nhan nude thai tir nhidu khu vue khai thac quang md. Tir kdt qua trdn cho thdy khoang bidn ddng vd ham lugng As trong trdm tich ciia dd tai nam trong khodng bidn ddng cua cac eon sdng trdn thd gioi.
As trong trdm tich khdng tuong quan vdi pH, EC va chat hiiu ca. Didu nay cho thay rdng, cd cdc ydu td khae dnh hudng ddn su hap phti As. Cae ydu td dd cd the la kich thude hat trong dat tidm nang oxy hoa khii, cac dang khoang set trang thai oxy hoa ciia As.
Wang & Mulligan (2006) cho rdng kich tiiude ciia cac hat rdn trong dat giu vai trd quan trgng trong kidm soat su phan bd cua As. Ngoai ra, theo Matera
& Hecho (2001) chat hiru ca trong ddt cung dnh hudng den tinh di ddng cua As. O dat axit
(3<pH<5,5), cae axit hiiu ca giu As, nhimg d ddt kidm (7<pH), cac axit hiiu ca phdng thich As.
2. Asen trong trdm tich vung Igr
Vao miia khd, ham lugng As trong tram tich vimg Igr CO khoang dao ddng kha Idn tir 5,27 - 18,06 mg.Kg\ gia tang tir sdng rach trong ndi dia ra vimg cira sdng. As trong trdm tich cao nhat duge tim thay d Rach Sdng 1, trung bmh 18,06 ± 0,46 mg.Kg'* va tiidp nhat kdnh Quan Ld trung binh 5,25 ± 1,03 mg.Kg'(Hinh3).
AQL AfiN ATD ARS1 AfiS2 A H ACC Vunj i»
C=iMua kho ciDMila mua —OCVN03:20(]eyBTNMT
Hinh 3. Ham lugng As (mg JCg'O trong trdm tich t^i cdc didm thu mdu a vung Igr vdo iw^a khd vi mua mua
Cic ky tu gidng nhau thi khic bidt khdng cd y nghia thdng kd bing phep thu Duncan vdi miic y nghia 5%
Ghi chd: ACC: sdng Cd Chidn; ARS_1; ARS_2:
Rach Sdng-Vinh Kim; ATL Rach Tin Lap - Hidp My;
ATD: cua Trin Di; AQL Kdnh Quan 1.6 - Thanh Tri ADN: sdng Hau - Dai Ngai
Theo Sanders 1980 (trich trong Gomez- Caminero etal., 2001) vimg cira sdng ven bidn la noi Idng dgng, tidp nhan chat d nhidm tir ede sdng rach trong ndi dia cluu anh hudng tir boat ddng dd thi, sinh hoat va phuong tidn giao thdng thiiy. Thue td cho thay, didm thu mdu tai Rach Sdng 1 Id noi tidp gidp vdi vimg ciia sdng (sdng Cd Chidn noi nhSn ngudn nude tir thugng ngudn dd vd) va la nai n h ^ ngudn nude tii hoat ddng san xuat ndng nghidp, sinh boat trong ndi dia. Day cd thd la nguydn nhan ham lugng As d Rach Sdng 1 cao. Kdt qua thdng kd cho thdy ham lugng As d vimg ciia sdng (Rach Sdng 1) khae bidt cd y so vdi sdng rach trong ndi dia. Kdt qua dd tai phii hgp vdi nghidn ciifu ciia Cenei & Martin (2004) cho rdng d vimg cua sdng ven bidn DBSCL vat chat la lumg cd kich thude nun ban vd duge cung cap sudt mua ndng. Nhirng chat nay cd khd nang giir kim loai nang Idng dgng tai chd, dan ddn ham lugng kim loai ndng cao.
Vdo miia mua, As trong trdm tich dao ddng trong khodng 7,03 - 13,76 mg.Kg^ As cao dugc tim tiidy d cua Trdn Dd, tiimg binh 13,76±:0,73 mg.Kg-^ va fliap nhdt d Rach Sdng 2, tiimg bmh 7,03 ± 0,63 mg.Kg'^ Ham lugmg As tai ede didm thu mdu khae bidt khdng cd y nghia thdng kd giira Rach Sdng 1, Rach Sdng 2, rach Tan Lap, Dai Ngai, kdnh Quan Ld va sdng Cd Chidn (ha ngudn sdng Tidn) nhung cimg khde bidt cd y nghia thdng kd so vdi didm thu mdu tai cua Trdn Dd (ha ngudn sdng Hau). Tuong tu nhu kdt qua nghidn eiiu d vimg man, hdm lugng As tang cao theo xu hudng tir ndi dia ra vimg ciia sdng. Kdt qua duge trinh bay trong hinh 3 cho thay ham lugng As cao hon cd y nghia thdng kd tai didm thu mdu cua Trdn Dd so vdi ede sdng rach trong ndi dia. Qua khao
sdt thue td didm thu mau d ciia Trdn Dd la noi tidp nhan phdn Idn ngudn nude tir cdc sdng rach trdng ndi dia, thiiy tridu tii bidn dua vdo vd Idng dgng do qud trinh tdi huydn phii. Day cd thd Id nguydn nhan gay ndn ham lugng As cao tai didm thu mdu ciia Trdn Dd. Kdt qua nghidn ciiu ciia dd tai phii hgp vdi nghidn eiiu ciia Tanner & Clayton (1990) trich trong Patel etal., 2005; Azecue & Nriagu (1995) tiich ti-ong Yau-Fei Chan, 1999 cho rdng vimg ciia sdng thudng la noi tich tu va luu giir cac chdt d nhidm, nhdt la kim Igai nang.
Kdt qua dugc trinh bdy d bang 2 cho thdy trung binh As trong trdm tich giiia miia khd vd mua mua khae bidt khdng cd ^ nghia thdng kd, gid tri tiling 18 NONG NGHIEP vA PHAT TRIEN N O N G THON KY 2 - T H A N G 8/2011
KHOA HOC CdNG N G H £
binh Idn lugt la 10,31±4,00 mg.Kg"' va 8,98 ± 2,85 mg.Kg^'
Bdng 2. Hdm lugng trung binh As (mg.Kg^*) trong trdm tich dr vung Igr
GiAtri Mua Trung binh sai k h ^ (P) Mua kho
Miia mua
10,31»± 4,00 8,98'± 2,85 0,24
Quychufo QCVN 03:2008/BTNMT
(nig.Kg') 12
Cic ky tu gidng nhau trong cung mdt cdt khae bidt khdng cd y nghia thdng kd bing phdp thii T-Test miic y nghia 5%.
Ham lugng As trung binh ndm trong quy chudn cho phep ddt sir dung muc dich ndng nghidp, lam nghidp va vui choi giai tri la 12 mg.Kg^QCVN 03:2008/BTNMT). Tuy nhidn, d mdt vai didm tiiu mau ndm trong ngudng d nhidm cua thd gidi (10 mg.KgO- Kdt qua cua dd tai cho thdy ham lugng As dao dgng trong khoang 5,27 - 13,93 mg.Kg-* cao bom so vdi nghidn eiiu ciia Dao Manh Tidn va ctv (2005);
Nguydn Viet Ky (2009) bao cao rang As trong trdm tich d viing Igr dao ddng trong khoang 1,3 - 3,6 pg.Kg ' Su xam nhidm As cd xu hudng gia tang theo thdi gian, dac bidt ha ngudn sdng Tidn va sdng Hau.
3. Asen trong trdm tich vimg nggt
Kdt qud thd hidn trong bdng 3 cho thay As trong trdm tich vimg nggt dao ddng trong khoang 4,5 - 9,57 mg.Kg-', ndm trong quy chudn cho phdp dat su dung muc dich ndng nghidp, lam nghidp va vui choi giai tri la 12 mg.KgHQCVN 03:2008/BTNMT). Ham lugng As tai cac didm thu mau gdn ha ngudn sdng Hau nhu: rach 0 Mdn, rach Cai Khd va sdng Cdi Rang cao ban cd y nghia so vdi khu vue tiiugng ngudn. Cung tuong tu nhu vimg man va vimg Ig, d vimg nggt khu vue gdn ha ngudn cd ham lugng chat huu ca cao hon tiiugng ngudn, kha nang hap phu As cao hon. Do vay, ham lugng As tai nhirng didm tiiu mdu d noi day sd cao. Ngoai ra, su phan bd As trong trdm tich phu tiiudc vao ydu td Idng dgng tir mdi trudng nude va cd trong tdng ddt Day la 2 ydu td chinh ddn ddn su tich tij As ti-ong tiim tich. Theo Ld Huy Bd (2000) tram tich chii ydu la biin Idng chtia nhidu kim loai nang va cd hidn ti«7ng keo tu tu nhidn d viing ciia sdng ndn ham lugng kim loai nang tai cac vimg nay kha cao.
Hon nira, ti-dm tich tai cdc sdng rach tiianh phd cung la noi d nhidm kim loai nang do chdt tiidi dd tiii mang
\^. Kdt qud ciia dd tdi cho tiidy ham lugng As ti-ong trdm tich ndm ti-ong khodng gia til As dugc tim tiidy
d mdt sd sdng va ciia sdng trdn thd gidi la 7,1 - 23,2 mg.kg"^ (Wasserman etal., 2001).
Bdng 3. Ham lugng As (mg.Kg^O trong trdm tich d vung nggt vao mua khd
Vjtri thu mdu
M)T3 ADT2 M)T1 AST ABK ACDl AGP ATN ACT ACR AHG
As trdm tich 8,76'''±1,88 4,5'^ ±0,11 6,47^ ±1,39 7,83'''±1,41 6,97*'"±1,25 9,57'± 0,97 6.99"^±1,84
7,58''" ±1,81 7,68"''±0,22 6,8r'"±l,42 8,96"'" ±1,70
QCVN03:2008/BTNMT (mg-KgO
12
Cic ky tu gidng nhau trong ciing mpt cdt khae bidt khdng cd y nghia thdng kd bing phep thu T-Test miic y^ nghia 5%.
Ghi chu: ADT3: Song TiSn, doan kdnh Vihh An;
ACP: Sdng Hau, doan kdnh Ba Thd; ADT2: Sdng TiSn, nga ba sdng Cuu Long; ATN: Sdng Hiu, doan sdng 6 Mdn; ADTl: Sdng TiSn, doan kdnh Thap Mu6i;ACT: Sdng Hiu, doan Cii KhS-Tp. Cin Tho;
AST: Sdng TiSn, doan ciu My Thu$n;ACR Sdng Cii RSng-Tp. Cin Tho; ABK Song TiSn, doan kSnh Bao Kd - Vinh Long; AHG: Sdng Cii Tu • Vi Thanh-Hiu
Giang; ACDl: Sdng Hiu, doan kdnh Vihh Td- Chiu Ddc.
4. Phan bd As trong ti-dm tich d ddng bdng sdng Ciiu Long
Ham lirgng As trong trdm tich d vimg man va Igr dao ddng khdng dang kd, gid tri trung binh Idn lugt la 10,42 ± 3,1 mg.Kg'i va 10,31 ± 4,01 mg-Kg^ khae bidt cd y nghia so vdi vimg nggt la 7,5 ± 1,7 mg.Kgl (Hinh 4); ndm trong quy chudn cho phep ddt su dung muc dich ndng nghidp, 1 ^ nghidp va vui choi gidi tri Id 12 mg.Kg'^ (QCVN 03:2008/BTNM'D. Tuy nhidn, gid tri trung binh vdn trong ngudng d nhidm As ciia tiid gidi (10- 2470 mg.Kg-^. Dd tai da tim tiidy cd su xam nhidm va d nhidm As vimg cua sdng ven bidn DBSCL vdi mtic dg tang dan tir ndi dia ra ddn ciia sdng ven bidn.
Phan bd As gia tang theo thir tu vimg nggt Igr va man, trong mdi vimg ham lugng As trong tram tich tang tir song, rach trong ndi dja ra ddn cira sdng ven
KHOA HOC CdNG NGHfi bidn. Ham lugng As d khu vue ha ngudn khae bidt cd
y nghia so vdi vimg thugrng ngudn. Mdt sd didm nghidn ciiu d DBSCL mac dii ndm trong pham vi cho phep theo QCVN nhung van ndm trong ngudng bi d nhidm ciia tiid gidi. D^e bidt hdm lugrng As cd xu hudng gia tang theo thdi gian va dat gid tri cao hon cd y nghia tai cac cua sdng so vdi sdng rach trong ndi dia. Khdng tim thay tuong quan giOra As trong trdm tich vdi pH, EC va CHC. Kdt qud nay cho tiiay As trong trdm tich cd thd tuong quan vdi cac hat trong ddt cae khoang set va cdc kim loai khae.
16 00-, 14.00 • 12 00-
^ 8 00- 5 6 00•
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• Ngpt
Trl>n tich Odng Bing S6na Cuu Long
Hinh 4. Hdm lugng trung binh As (mg.Kg'^) trong trdm tich d vimg m$n, Igr vd nggt
Cic ky tu gidng nhau thi khic bidt khdng cd y nghia thdng kd bing phdp thu Duncan vdi miic y nghia 5%
IV. KET LUAN
Ham lugng As trong trdm tich vimg man trong khoang 7,10 - 12,41 mg.Kg'^ gia tii tinng binh la 10, 42±3,1 mg.Kg' ndm trong quy chudn cho phdp dat sii dung muc dich ndng nghidp, lam nghidp va vui choi giai til la 12 mg-Kg-^QCVN 03:2008/BTNMT). Mdt sd didm thu mau tai viing man (Bai boi, Hd Phdng va cOra Ganh Hao) vugt ngudng cho phdp ciia QCVN;
mdt sd didm thu mau d DBSCL mac dii ndm trong gidi ban cho phdp tiieo QCVN nhung vdn ndm trong ngudng d nhidm ciia the gidi. Khdng tim thdy mdi tuong quan giua ham lugng As vdi pH, EC va chdt huu ca trong tram tich.
As trong trdm tich d vimg Igr va nggt (thude sdng Tidn va sdng Hau) cd gid tri trung binh lan lugt la 10,31±4,01 mg.Kg' va 7,5±1,7 mg.Kg-S ndm h-ong khoang cho phep ciia QCVN (QCVN 03:2008/BTNMT Id 12 mg.Kg-^). Tuong hi nhu vimg man, d vimg Igr khdng tim thay mdi tuong quan giiia As b-ong trdm tich vdi pH, EC va chdt hiiu ca.
Dd tai tim thdy sir xam nhidm As trong trdm tich tiieo thii tu tang ddn tir viing nggt Ig', man; tii thugrng
ngudn ddn ha ngudn sdng Tidn va sdng Hau, tir sdng, rach trong ndi dia ra ddn ciia sdng ven bidn. As khdng khae bidt giiia miia mua va mita khd nhung cd khae bidt giiia cdc vi tri thu mdu.
TAIUEUIHAMKHAO
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159, pp. 293-301.
ARSENIC CONTAMINATIONS IN SEDIMENTS AT MAIN RIVERS IN TOE MEKONG DELTA, VIETNAM Pham Viet Nu, Bui Thi Nga, Le Van Muoi Summary
The study was carried out to determine arsenic distribution and contaminations in sediments at saline, brackish and fresh areas in the Mekong delta. Research results showed that arsenic in sediments fluctuated in range of 10.42 ± 3.1 mg.Kg"' and 10.31 ± 4.01 mg.Kg' at saline and brackish areas respectively' that figure differed significantiy to compare fresh areas with the value 7.5 ± 1.7 mg.Kg"' in average. The present study revealed that there were arsenic contaminations increasing from inland rivers to estuaries and from the upstream to the downstream of Tien and Hau rivers. Particularly, the arsenic concentration increased significantiy higher in coastal mudflat than in other regions. This issue should be studied on the mobility, the accumulation of arsenic in soils, water and valuable species of aquatic organisms in the region.
Keywords: As contamination, river sediments, Mekong delta.
Ngudi phdn bidn: PGS.TS. Ph^un Quang Hd
