CVv269S152017028.pdf

Nghien diu - Trao doi

Nghien cuii van dpng niTdfc ngam Karst khu Vlfc tpuiig tam thf tran Dong Van

va n/leo Vac b^ng phifofng phap dja chat thuy van dong v[

O ThS. PHAM BA QUYEN, ThS. HOANG DAI PHUC

Udn doin Quy hogch vi Diiu tra Tii nguyin nudc miin Bic

ThS. TRIEU Biic HUY

Trung tim Quy hogch vi Diiu tra tii nguyin nudc Quoc gia TS. BAC DLJfC NHAN

Hdi Dia chit thuy vin Viet Nam

Tdm tat: Ky thuit thuy vin ding vi sd dung ding

w phdng xg thti vi nong dd ion Ca2+ iim chit chl thi da dugc ap dyng di nghiin cdu hudng vin ddng cua nudc ngim karst khu vtfc thi trin Ding Vin vi Meo Vac, thh Hi Giang. Mudi biy (17) miu nudc ngim karst d cac gieng khoan, mgch Id vi nUdc mUa cd cao dd khic nhau di dugc liy vio mOa khd vi mua mUa nim 2016 di phin tich hogt do triti vi nong dd ion Ca2*- cung nhU bicacbonat trong cic mau nghien cdu. Kit qua cho thiy, vio mua mUa nUdc trong tit ci cic giing khoan diu cd hogt dd triti nhu nhau va ngang tiing hogt dd triti trong nUdc mUa tai thi trin Dong Vin. Vi mda khd, hogt di triti tmng nUdc ngim karst cd giim di vi cd stf sai khic so vdi hogt do triti trang ntfdc mua. Nhu viy, vio mua khd do lugng nUdc bo cip thip nen nUdc karst cd tic dd van ddng chim han so vdi tic do van dgng vio mOa mua. Tuy nhidn, htfdng v$n ddng ntfdc ngam karst trdn khu vtfc nghien cdu khdng thi xie djnh dugc mgt each chfnh xac do ciu true karst li rit khic nhau ngay ci trdn mit diin tich hgp. Kit hgp vdi chl thj Cag^ trong nudc cung khdng thiy rd hUdng van ddng cCia nudc karst tren khu vtfc nghidn ctfu.

Nguyen \'j' cua phUdng phap

Nufle ngam karst cfl the efl hai nguon bo elp, dfl Id nguin ngay tal dja phUdng vd nguin di chuyin tQ dia phUdng khac qua cae kdnh hang-dgng trong Iflng nui. Bit k l Id nguin dja phUdng hay ngufln tQ xa den, nUflc vdn dflng diu theo quy ludt Id tU diem efl dfl eao cao hdn d i n dilm cfl do eao thap hdn

2 8 Tdl nguyen vd Mdi tru'dng | Ky 1 - Thdng 8/2017

(djnh ludt Darcy). Thfli gian van dflng efla nufle trong vflng karst efl the duge xac djnh nlu bilt hogt do phflng xg efla ding vj triti trong nuflc tgi dilm bo cap va dilm xult Ifl. Neu tgi vung b l cap nufle efl hogt dfl triti Id AO thi tgi diem xuat 16 hogt dfl triti trong nuflc se Id At vd At < AO vi trong thfli gian vdn dgng triti se bj phdn rd. Nlu giQa hai dilm b l elp va xult lp cfl mli lidn hd true tiep thi thfli gian vdn dflng (t) tQ diem b l cap den dilm xuat 16 duge ufle tfnh theo cong thflc:

n^5. = i7 75,iji_^ (1)

Trong dfl: T1/2 Id chu ky bdn phan ra cfla dong vj triti vaT1/2 = 12,3 ndm.

Nguydn ly nhan didn huflng van dflng cCia nUflc ngam Karst theo phUdng phap dong vj phflng xa phdi bdo dam cae dilu kien sau. Vflng karst cfl cau trfle tUdng dol ding nhat: Hodc ehl efl eae khe nflt trong da, hoae chl cfl dong chdy theo hang; thdnh phan khodng thach khu vge karst phdi tUdng doi ding nhit de cfl t h l kit hgp dUde vfli ch? thj dja hfla Id ning dp Ion eatxi hoac bicacbonat trong nuflc.

Phin thge nghigm

M^u nuflc tQ 17 vj trf khu vgc trung tdm thj trin

Dong Vdn vd Meo Vge duge lly vao mua khfl (thang

4/2016) va mfla mUa (thang 9/2016) d l phdn tich

hoat dd phong xa cfla triti. Nuflc mua dugc lly tgi thj

tran Ding Van de xac dinh hogt do triti cfla nUfle b6

d p . Kit qud nghien cQu dd xde dinh duge nUflc

Bdng 1; Hogt dd triti vi ion Ca2+ vi HC03- (meq/L) trong cic miu nUdc ngam karst trdn khu vtfc tht trin Ding Vin vi Mdo Vac via mCia mUa vi mOa khd nim 2016

TT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

KHM NMDV NLOV D V I T L I icrsN OV2 DV4 CT4 CTS MVS 0 7 CT2 NLTD NHPL NHPVT NHTD NSNQ

0\a danh Nt/6c mira Dong Vin Ngufin 1$ sau UBND h u y f n Dong Van

L& khoan D V I , {}8ng Vdn L6 khoan T L I , D6ng v3n L6 Idroan khai thdc nh^ hdng Sdng NOi, f } & n g v a n Lo khoan 0V2, OSng v a n Lo khoan DV4, D6ng VSn LS khoan C T 4 , M 6 o V f c Lo Wioan CTS, M6o Vac Ld khoan MVS, Meo Vac L6 khoan CT7, M e o Vac Lo khoan CT2, Mfeo V?c Nguon I9 To Dli, TT M e o Vgc Nu^5>c h& P^i LAng, M^o Vgc N u ^ hS Pa Vi t h i / g n g , M^o Vgc

N u ^ ho To Dli, Meo Vgc N i / o ^ song Nho Que, chSn cau Trang Ht/cng

Cao d o ( m )

1081 1081 1057 1063 1061 1105 1098 935 941 281 952 936 1087 834 945 98S 434

A(^H) ± l a , TU Miia khd 1,73 ± 0 , 2 1 1,74 ± 0 , 1 5 1,53 ± 0,19 1,48 ± 0,20 1 , 3 7 * 0 , 1 6 1,39 + 0,19 1,45 ± 0,18 1,62 + 0,12 1,50 ± 0 , 1 5 1,28 ± 0 , 1 3 1,38 ± 0 , 1 9 1,36 + 0,21 1,67 ± 0 , 1 6 2,98 ± 0 , 2 8 2,72 ± 0 , 3 5 2,75 ± 0,18 1,72 ± 0 , 1 2

Miia mt/a 2,26 ± 0,22 2,28 ± 0 , 3 7 2,45 ± 0 , 3 6 2,17 + 0,33 2,19 ± 0 , 2 3 2,15 ± 0 , 2 1 2,25 ± 0,20 2,43 + 0,15 2,34 ± 0 , 1 6 1,98 ± 0 , 1 6 2,16 ± 0 , 1 7 2,11 ± 0 , 1 9 2,35 + 0,15 3,15 ± 0 , 1 8 2,28 ± 0,28 2,34 ± 0 , 2 0 2,38 ± 0,37

Miia mira Ca^*

2,00 2,15 0,66 2,80 1,80 1,70 1,40 1,83 1,45 1,40 i.m 2,10 1,40 0,60 0,63 1,80 2,40

HCO3 2,80 2,80 1,40 3,60 4,15 3,00 2,10 3,00 2,40 3,00 2,50 3,10 2,20 1,40 1,00 2,80 2,40

Miia khfi C a ^ 1,63 1,80 1,55 1,80 2,20 1,52 1,71 2,00 1,85 1,65 1,50 1,91 1,84 0,68 0,85 1,68 1,65

HCOa- 2,22 3,50 2,80 3,25 4,55 2,71 2,47 3,25 2,85 2,88 2,39 2,71 2,47 1,30 1,20 2,71 2,65

nglm karst vung nghien cUu la nuflc mua dja phUdng trong eac mUatUdng Qng [Phgm Bd Quyln, 2017] vi vdy, eo the coi hogt do triti trong nuflc mua tgi thj tran Dong Van Id dai didn cho mQe triti trong nuflc bo cap cua hai khu vgc nay.

Ket qua va thdo luan Bdng 1 trinh bdy kit qud do hoat dfl triti (cung vfli sai so Is) trong 17 mau nufle karst thu gom tren dja ban thj trin Dong Vdn va Meo Vac vdo hai mua, mua mua va mijakho nam 2016.

Kit qua Bang 2 cho thiy, vdo mua mua hoat dfl phflng xg efla triti trong tat ca ede mdu nUde tuy lly 6 cac dp cao khac nhau nhung hlu nhU diu nhU nhau trong khodng sai so cfla phdp phdn tfeh va ngang bang vfli gia trj hoat dfl triti trong nuflc mua. Cfl t h l thay, da vol 6 vung ndy da bj karst hfla manh nen thdi gian van dflng cua nude mdt xuing ting da sdu cung nhu thfli gian van

Bdng 2: Kit qui xd ly thdng kd so sanh gii tri hoat di tmng binh ciia triti trong cac miu nUdc karst vio mua khd vi mua mUa khu vtfC thi trin

Ddng Van vi Meo Vgc theo phUdng f^ip Mann-Whitney v& a =0,01

z-Test: T w o Sample f o r Means

M e a n Known Variance Observations

Hypothesized Mean Difference z

P(Z<-z) one-tail z Critical one-tail P{Z<=z) t w o - t a i l z Critical t w o - t a i l

Variable 1 1.5158

0.17 12 0 -4.5694 2.445E-06 2.3263479 4.889E-06 2.5758

Variable 2 2.2383

0.13 12

dgng din cac vi tri gieng khoan la khd nhanh ndn hau nhu triti chua kjp phan ra. Vao mfla kho sfl khac bidt ve gid trj hogt do triti trong eac mau nuflc karst fl eac do eao khac nhau cfl sg khdc biet nhung mUc dfl khong Ifln va cung rit khfl de efl the danh gia huflng vdn dgng efla chflng.

Van dflng trong karst, nUfle se khulch tan theo cde khe nQt, hang ngam nen se efl qua trinh hfla tan ealeit ldm tang nong dfl

calxi hoac bicabonat. Do vdy Ca2+/HC03- CO thl sfl dgng nhQ ch? thj d l ddnh gia huflng vdn dpng efla nuflc. Trong truflng hdp nay nuflc se di ehuyin tfl diem co ning dp Ca2+/HG03- thap din vj tri efl nong dfl calxi va bicacbonat eao va phdi tfl cao dfl cao xuong cao dfl thap. Bhng 1 ndu 6 tren trinh bay gia tri ning dp Ca2+ va HCO3- trong ede mdu nUde va cao dfl eac vi trf lly mdu. Nlu theo dieu kidn la nUdc chdy tQ cao dp

Tdi nguydn vd Mdi tru-dng | Kyi-Tiling 0/2017 2 9

Hinh 1 : Stf phy thudc gitfa nong di Ca2+ trang ntfdc ngim karst khu vtfc thi trin Ding Vin vi Meo Vgc vi cao dd cOa cac vi tri liy miu

1 2 0 0 - lOOO •

"S 8 0 0 • E S ! 6 0 0 • 3 400 •

200

0,00

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0,50 1,00 [ C a

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A ^ A \

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• Ca vs. H (B&ng VSn-mOa mua)

• Ca vs. H (M6o V9C-m0a mua) A SNQ-mCia mi/a

O Ca vs. H ( O ^ van-mila khd) O CJ vs. H (M#o Vac-mCia khd) A SNQ-miia khd

cao d i n eao dp t h i p thi ket qud trinh b i y trong Bdng 1 eung khflng the eho phep dua ra nhdn dinh ve huflng van dflng cCia nuflc karst vijng nghien cflu vi nong dp Ca2+ trong nufle khflng tudn theo quy ludt tang tfl d i l m eo cao dp eao d i n d i l m efl eao do t h i p , dge biet la 6 khu vuc thj t r i n D i n g Van. Hinh 1 trinh b i y s g phy thugc glQa nong dfl Ca2+ trong nufle va do eao efla hai khu vgc thj t r i n Dong Van vd Meo Vgc vao mua mua vd mfla kho de minh hga cho k i t ludn trdn.

TQ hinh 1 co t h l nhdn djnh rang, khu vgc Dong Van nuflc ngam karst khflng vdn dflng tap trung theo mpt huflng ma toan bp khu vQc nay la vung bo cap, toan bfl nUflc mUa chay theo cac khe nUt hoac cac ong dSn (conduit) xuong sau va phan tan di cde ngd khdc nhau. V l mfla mua cfl khd nang nuflc n g l m karst tfl ed hai khu vge D i n g Van vd Meo Vge d l ra song Nho Que (theo hQflng mui tdn tren hinh 1) vi nflng dp ion calxi trong nufle sflng cao hdn so vfli nuflc karst, nhung v l mua khfl khflng nhan thay ro nUflc karst IQ hai khu vge trdn do ra song vi nong dd ion calxi ngang b i n g vfli nUfle karst. Tuy nhidn, nhan djnh nuflc karst tQ Dong Van vd Meo Vge vdo

mua mQa d l ra sflng Nho Que eung ehua efl ed sfl bdo ddm ehae ehan vi he thong hang karst phat t r i l n r i t phflc tap, phu thugc nhieu vao thanh phan khoang thach cal- xit, dolomit..., vdo d i l u kidn moi truflng tren khu vuc nghien cUu.

Thanh p h i n khodng thgch thuflng id phflc tgp va khong d i n g nhat ngay ca trong phgm vi didn tfeh hep. Rat efl the nudc ngam karst tU khu vuc thj t r i n D i n g Vdn vd Meo Vge xuat 16 fl nhQng d i l m ngoai khu vuc nghidn cUu theo ede hang n g l m trong long nui nhung khong lien hd vfli sflng Nho Que ngay tgi dja phuong.

K i t ludn

TU cac k i t qud nghien cUu sii dgng chl thj la dong vi phflng xa triti k i t hgp vdi thanh p h i n thuy dia hfla d l xdc djnh huflng vdn dflng vd toe dfl vdn dpng cfla nuflc n g l m karst khu vge thj tran Dong Van vd Meo Vac mflt s l k i t luan da dugc rflt ra nhu sau:

Ky thudt danh d i u k l ca pham nhuflm eijng nhu d i n g vi rat khfl efl t h l xdc djnh ehfnh xac hudng van dflng cua nufle ngam karst vi e l u true duflng v d n ehuyen nufle trong nfli da voi la rat phflc tgp. Thdnh p h i n khodng khflng d i n g n h i t , e l u trflc khe n f l t v d dudng dflng trong nui ngay

cd tren mgt khu vgc hgp la rit khae nhau ldm cho hudng vdn dpng cua nude khong dong nhat.

Day la nhQng can trfl Ifln nhat chua the khae phuc de cfl ttil dUa ky thuat danh dau vao nghien cflu efl hidu qua hQflng van dpng cua nuflc karst 6 Viet Nam.

Truflc khi phat trien cac nghien cQu ve huflng van dflng, t i c do van dgng eua nUflc ngam karst efl le cac ky thuat nhU vidn t h a m , dia vat ly... c i n phdi tien hdnh truflc de xac djnh cau true dja chat thuy van lam co sfl dg dodn duflng vdn dflng cfla nUflc khi CO bo cap.

TAI LIEU THAM KHAO 1. Bang DUc Nhan vd nnk, 2009. (Ing dung ky thuat vit trong nghidn cdu nUdc karst viing Dong- Bac Vidt Nam: Budc diu ip dn^r\g tgi Yen Minh, Hi Giang. Bdo cao chuyen de thugc de tal KC.08- 19/6-10: Nghien cflu sQ hinh thanti, phdn bo vd de xud't hd phUdng phdp ddnh gid vd sfl dgng TNN n g l m fl vung D6ng-Blc Viet Nam.

Hd Nfli, 2010.

2. ThS. Pham Bd Q u y l n vd nnk, 2015-2017. "Nghiin cdu giii phip khai thic, sd dyng bin vOng nguon nUdc tgi cic vOng nii cao karst Ddng Bic Viit Nam. Ap dung thd nghiim tgi ving cao nguyin di Ding Van", ma so 2015.02.06. D 4 tdi KHCN cd'p B g . "

3 0 Tdl n g u y e n v d Mdi t r u d n g | Kyi-Ttiang 8/2017