Nhng vn d c bn v moi trng t nhi

N6 lien quan den h$ kinh te, sinh thai va rnoi tnrcnq vci Thien - Hue.. H$ d m pha TG - CH la moi tru'ong sinh cu, la dia ban heat d>ng kinh te quan tronq, mang lai qia tri tai nquyen cu

- ? HQI THAO KHOA HQC

sO KHOA HgG CONG NGH~ VA MOl TRUONG TRUNG TAM KHOA HOC TU NHIEN VA CONG NGH~ Qu4c SIA

SOTHU'LQI

•

•

SEMINAR ON COASTAL LAGOON

Hai Phong 07 - 08 Nov 1994

- ,

HQI THAO KHOA HQC

Co quan chu tri: PHAN VI~N HAl DUONG HOC TAl HAl PHONG

De tai cap nha ruroc KT.03-11, chuang trlnh KT-03

Co quan to chuc:

- vu PHAT TRIEN CeJNG NGH~, 80 KHOA HOC CeJNG NGH~ vA MeJl TRUONG.

- PHAN VIEN HAl DUONG HOC TAl HAl PHONG, TRUNG TAM KHOA HOC TU

- TRUONG DAI HOC THUY LOI, 80THUY LOI

Ban to chuc:

-KS Truong Trl Tan, Trl fong ban.

- PTS Nguyen Chu Hai,Uy vi f §n thl f6'ng true

-PTS.Trinh Quang Hoa, Uy vh§n

- PTS.Tran Dire Thanh, Thuky.

MVC lVC

Loin6idau

1 Truong Chi Tan

2 Nguyen Chu Hoi

Tiep can nghien Cl1USLr dl:mg hop IV tai nquyen va phat tri~n lau ben

3 Ho Nqoc rno.

Pha Tam Giang - nci h9i tu cua nhieu van de khoa h9C

4 Nguyen Dinh Hoe vannk

M9t s6 dac di~m dia d9n9 hrc n9i sinh hi$n d<;liva tac d9n9 cua chunq

d6i voi dam pha Tam Giang - Cau Haii

5 Nguyen HOu CLf

Hlnh thai, cau true va tien hoa cua h$ dam pha Tam Giang - Cau Hai

6 Tran Dinh Len va nnk

Dac diem tram tfch tang mat lagoon Tam Giang - Cau Hai

7 Nguyen Due cu va nnk

Dac diem dia hca tram tfch day h$ dam pha Tam Giang - Cau Hai

8 Phem Van Viva nnk

9 Luu Van Dieu

Mot s6 net ve dac diem rnoi trl10ng thuy hoa dam pha Tam Giang - Cau Hal

10 Doer: B9 va nnk

Nghien ClJ'Uniing suat sinh h9C so cap cua thuc v~t n6i trong h$ sinh thai

dam pha Tam Giang - Cau Haii

11 Tran Due Thenti vannk

Nhung van de co ban ve moi trl10ng tlf nhien, sinh thai va tai nguyen h$

dam pha Tam Giang - Cau Hai

12 Nguyen Nhet Thi.

M9t s6 nhan xet ve khu h$ sinh vat va tiem niing nguon IQithuy san

dam pha Tam Giang - Cau Hai

13 Nguyen Van Tien

Mot 56 dlm li$u ve rong bien va thuc vat thuy sinh bac cao

14 Trinh Quang Ho«

Mo hlnh hoa trong vi$c khai thac dam pha Tam giang - Cau Hai

15 Ng6 Dinh tos«

Mot s6 van de can xem xet trong bai toan SLr dunq khaii thac hop Iv

pha Tam Giang - Cau Hai

16 Ho Nqoc rro.

Nghien ClJ'Uve tfnh khong 6n dinh cua cira Tl1 Hien va suy nghi bi$n phap SLr Iv

17 Nguyen Mien va nnk

Nhung luat 1$bat thanh van va nhung chfnh sach quan Iy,

18 Nguyen Chu Hoi vannk

19 Ban to 'chuc h9i ttuio

Thong bao cua Hoi thao khoa hoc ve dam pha Tam Giang - Cau Hai

Trang 1 3

'7 11

16 24 29 34 39 42

46

52

64

72 75

81 85

89 94 99

Tran D(lC Thenh Nguyen Chu Hoi

MO ' D A U

He dam pha Tam Gian -Cau Hai (HOP TG -CH) c6 dien tfch 21.600 ha, keo dai 68km an ngGhau het chieu dai Tinh Thua Thien - Hue, lien quan den 31 trong 64 xa cua

4 trong so 8 huyen cu Tinh N6 lien quan den h$ kinh te, sinh thai va rnoi tnrcnq vci

Thien - Hue Dam pha TG - CH c6 quan h mat thiet va lien quan vci tren 30 van can (1/3 dan cv Thua Thien - Hue)

H$ d m pha TG - CH la moi tru'ong sinh cu, la dia ban heat d(>ng kinh te quan tronq, mang lai qia tri tai nquyen cu the va vo hlnh to Ion a mot phvong dien nao d6, c6

the n6i, su ton tal cu d m pha anh hu'ong quyet dinh den sir phat trien kinh te·- xa h(>i cua Thua Thie - Hue

Tuy nhien, nhan thuc v b n chat tu nhien va qia tri tal nguyen h$ sinh thai dam

chua hieu qua, kh6ng lau ben, da noi com len c c doi khanq IQi lch sir dunq, nguy co can kiet tai nquyen, tho i hoa rnoi truonq NhGng van de quan Iy rnoi trvong va che ngl! tai bien tro le cap bach nhu ng~p lut, nhiern ba , nhiem man, ach tac giao tho g do

chuye , lap cua VI the y u cau phai c6 mot mo hlnh Slr dunq ho Iy va lau be dam pha TG -CH De dat muc ti u nay can phai c6 nhO"n hieu biet co ban ve rnoi tnrcnq tu

nhien, sinh thai va tai nquyen dam pha Bai viet nay danh gia t6ng quan va c6 h$ thong

nhu q van de nay dua tren nhO'ng tai l$ da c6, dac biet la nhieu tai li$u dieu tra khao sat moi cua de tai KT.03.11 do Phan vien Hai duonq h9C tai Hai Phonq chu trl voi sir tham gia cua cac can b(>chuyen men cac truonq Dai hoc t6ng hop Ha N6i va Hue

V! TRi H~ SINH THAI DAM PHA TG - CH TRONG H~ THONG DAI VEN 80 ' VI~T NAM

Dam pha ven bo la m6t trong nhO'ng doi tuong dune dac bi$t quan tam tren the gioi [7,9,1 ] Duci cac g6c do khac nhau dam pha TG - CH da dune dieu tra kha sat tir lau [1,8,15] nhunq chi den gan day mci ducc ghi nhan la mot loai hlnh thuy vue co ban va tieu bieu a ven be nuoc ta [4,1 ,14] l.an d u tien trong de tai KT.03.11 n6 duoc nqhisn cuu v6i tv each la mot h$ sinh thai ven be doc lap ngang cap vci cac h$ sinh thai cira song chau th6, cua s n hln pheu va cac vinh ven be

Viec nhan thuc dung dan kie loai h$ sinh thai da ta ra nhGng din hvong dun

dan v phuc q phap dieu tra khao sat, n(>i dung nqhien ciru va muc tieu su'dung, quan

dam pha phan bo trong k o ng vi d(> 11 - 170B a mien Trung Vi$t Nam va cOng thuoc loai co Ion tren the giai N6 th 6c kieu cau true gan kin, c6 2 cira thong, theo phan loai cua Nichols [7]

2 VI tr i va tinh dia doi,

H$ d m pha TG - CH la mot lagoon nhiet dci, nuoc 19, narn d phia tay Bien Dong,

noi co hu'ong qio thinh hanh huang dong vci tan xuat 56 % thai dai trang 8 thanq Khac

8(>, Tam Giang - Cau Hai narn a'phia bac deo Hai Van thuoc mien ven bo tay vinh Bac

8(>,noi co luc;mg rnua thuoc loai Ian nhat nucc ta, tren duoi 3000mm/nam [10], Sl/ trung

khac nghiet ve thai tiet anh huang sau sac den rnoi trucnq tu nhien va sinh thai h$,

-300m, sau den 6 - 7m va co huonq dich len phia bac trong the ky qua [13] Do vao dam pha co cac con song Ia n u song Hucnq, 80, Dai Giang, Truoi Tnrcc cira song

Huonq, 80, phat trien cac cau true vi chau tho trang lagoon Cac delta trieu phat trien a

phat trie cac them, bai lag o cao 2 -4m Cau tao bang cat, cat bot

sac cac yeu to tu nhien va sinh thai h$

SU'phan bo tram tich day dU'9C phan biet theo 5 tieu khu vue phan anh tuong tac song bien

qiau rnun ba huu co

b Tieu khu Dam Sam la cat hat nho, bot Ian xarn den

c Tieu khu cua lagoon Tir Hie , Thuan An cat mau vang Ian vo sinh vat

d Tieu khu Tam Giang -Thuy T0 va cac b i ngap trieu ven dam Cau Hai tram tlch rnin

d n theo chieu sa , rn u nau vanq, xarn na

e Tieu khu Cau Hai bun bot nho xarn xanh

53

Ve dia hoa tram tfch, Iau het dam pha c6 qia trj Fe3+/Fe2+ <1, pho bien 0,3 - 0,7

the hien moi truonq khLr vu , khong xuat hi$n khf H2S trong tram tfch MCrcdo khLr cao

han ca la a khu dam Thu Tu -Cau Hai aTam Giang, hai ria bo yem khf, a true giCraco

dong chay thoano khf h n, ty s6 Fe3+/Fe2+trEm 1,6; thap nhat a Thuy T8 la 0,38

Dia diem Fe3+ (%) Fe2+ (%) Mn2+ (%) Fe3+/Fe2+

Tam Giang 0,42 0,61 0,0184 0.69

Thuy ro 0,37 0,98 0,0136 0,38

a cac cira song do VaG dam pha, IUQng Fe2+, Mn2+ luon thap va ty s6 Fe3+/Fe2+

lucri cao, thuon 0,7 - 0,83 a cira song Huang, 6 l.au, Truoi, a true lach c6 ruroc chay

ty Ie Fe3+/Fe2+ luon tren 1

3 Khihau,

Tong luang birc xa narn 120 - 140Kcal/cm2, cue dai thanq 5, cue tieu thang 12,

can bang 70 -80Kcal/cm2 Nhiet do khonq khf trung birth narn 24,5 C, bien dQ narn dat

10oC Cac thanq nonq nhat la 6, 7, 8 (tren 290C), cac thanq lanh nhat 12, 1, 2 (18

-210C) Luonq rmra 2.500 - 3.000mm/n m, tap trung VaG thang 9, 10, 11 Mua mva nr

thanq 9 den thanq 1 narn sau 8Q ~m khong khf 83,5%, rnua ~m thanq 9 -thanq 4, rnua

kho thanq 5 -thanq 8 Gi6 huang dong 56% t6c dQ vu the 1-7m/s Mua dong thvong gio

huang tay va tay b c, mua he huang dong va tay nam Bao VaG cac thanq 7 -thanq 11,

tap trung vao thanq 8, 9 Moi narn c6 1-4 can bao anh hvang, 0,5 - 1 con/nam tnrc tiep,

co narn khong co ba Bao gay rrura lon, qio rnanh Gi6 bao dat 40m/s Mva bao keo dai

c6 the den 2 -3 nqay dat toi 260mm Nucc dang trong bao c6 the dat tren 2m

4 Thuy van

Thuy Iy

Tong dien tch luu vue cac song do VaG dam pha gan 4.000km2, modun dong

chay binh quan narn tren 501/s.km2 Tong IVQng chay VaG lagoon khoang tren

6km3/n m Modun dinh 10 thuoc loai cao nhat nuoc ta 2.370 - 7.0001/s.km2 C6 3 con

s ng chfnh do vao dam pha la 6 l.au, Huang, Dai Giang Song Bo la mot nhanh quan

tronq cua son Huonq va song Truoi la mot nhanh cua Dai Giang

Song Huang gom 3 nhanh Ta Trach, HCru Trach va song Bo co tong

lu vue 3.000 m2, IU'Qngchay hang nam 5,4km3 ruroc, mat dQ 0,75km/km2, do d6c pho

bien 11 - 12% [5] Ham IUQng bun cat trung binh 150g/m3, Cl/C dai 1.830g/m3. Tong

IVQngchay Va G 1060 - 80% ca narn, thanq c6 10 Ian nhat la 10, 11 Tong IVQng 10thang

Ia nhat 25 - 30% ca narn Dong chay Ian nhat thanq 10 va 6 (10 tieu man) ki$t nhat

thane 4 LO tieu man vao thang S,6 gay hai cho vu he thu Mot narn co 3,4 - 6,7 tran 10.

Ve rnu c n xay ra han va nhiern man NU'<Jctrieu man chay nqircc den Nga Ba Tuan vuot qua Hue Dong chay song rnua can khonq du sire day man do trieu truysn sau vao trang song [S]

Song 0 l.au co luu VlJC S72km2, IUQng chay hang narn 0,Skm3. Song Dai Giang co

Che do hai van ven be phia nqcai dam pha kha phtrc tap Thuy trieu cira Thuan

b n n at bie do rat nho, chi 35 - SOcm Khu cira Tu Hian trieu ban nhat khonq deu bien do SS- 11 Ocm Song trieu truyen tu phianarn len bac, dong trieu len O,S - 0,7 nut, dong trieu xuon 1-2 nut To do dong song co the tren SOcm/s

-1,Sm Ve mua he song thinh hanh hU'ang dong nam, tan xuat 36%, d¢ cao pho bien 0,3

Mire nunc trong d m pha bien doi ro theo khonq gian, thai gian Ve rnua can rrurc nucc d m pha luon thap han dlnh trieu 2S - 3Scm 6 dam Cau Hai; S - 1Scm 6 Tam Giang Mua 10, nquoc lai, rmrc nunc dam pha luon cao hen rrurc rurcc bien 70cm 6 Cau Hai Bien do trieu d m pha nho han bien va 6 song, tai Tam Giang 30 - SOcm, Cau Hai

10 -2 cm Da don rnuc nucc narn Ian nhat dat 70cm 6 Tam Giang, 1OOcm 6 Cau Hai

Song tron dam pha khong Ian do qio tao len, do cao thucnq S -1Scm, khi qio manh va bao dat 30 - SOcm

dong qio quyet dinh Khi c mua 10, dong chay 10 tang dot ng¢t Vao rnua kho, dong tai

-10cm/s vci toe do qio S c m / s va hlnh thanh len cac hoan hru cue bo cunq hcac nquoc chisu kim dong ho tu theo hU'ang qio thoi

Thuy tio e v ache'd(J trao dot nuoc.

Do trao doi nucc yeu cac yeu to thuy hoa phan di rat r6 theo khono gian th~ng

dU'ng,doc d m pha Ch do khf hau khac nqhiet va cau true h$ tao ra nhOng bien d¢ng Ian cac yeu to thuy hoa theo mua

Do man tra g d m pha giao dong 1 - 33%0, rnua mua trung blnh duai 10%0.rnua kho trung binh la 20%0 tlnh phan tang do man Ian chua tu'ng g~p 6 ven bo Viet Nam trang vue nuoc chi sau 1 -2m, manh nhat 6 Tam Giang va cira song Huang Ve mua kho, tai Tam Giang trung binh do man tang mat 9,6%0 tang day 22,9%0 chenh I$ch

va nghich con th hien 6 tat ca ca c y u to thuy hoa

Bien doi do man theo pha trieu nqay dem rat lcn ,bien d¢ 20- 27,7%0.6 cira Thuan S,S-S,9%0 6 Tam Giang, 1-2%0 6 Xuan Vinh ( Thuy Tu) Theo mua, dao dong d¢ m~n con Ian hen nhis tai cac diem

Do pH bien doi khong tuonq dong theo do man, khoanq 7,2- 7,8 va tang can v

Giang) trang khi Tu Hien dat 7,9 Do pH phan tang manh hen ve rnua rrura ( mat 6,3 day 7,2 6 Thuan An )

khoanq O,Sml/l

55

Do duc c6 quan he den dinh duonq, do chieu sang vue nuoc va su boi lang dam

5 Cau true sinh h9C h~ sinh thai

Cau true sinh hoc dam pha TG- CH kha d ,c biet phan anh tinh chat khu h$ ven

be tay Vinh Bac Bo, dong thai th~ hi$n nhOng net dac thu cho rieng h$ dam pha

3 Ian mat )

D¢ng vat noi nqhco thanh phan loai (31 loai) [ 6 ] chu yeu nh6m Copepoda nquon

g6c nuoc ngot, 10, bi~n, nhunq sinh kh6i k a ton, blnh quan 3027 ca th~ 1 m 3 (bac song

Huonq 2 535c t i m3, nam song Huonq 3.520 cti m 3 ) Ban nqay sinh kh6i nho hen dsrn 1,5

- 1,8 Ian

Thuc vat da 4 lcai ron ta , 1 loai thirc vat bac cao [8] C6 mot vai loai thuc v~t

rnai ch o ( Valisneria spilaris )a Tam Giang dat 0,2 - 0,5 kg 1 m 2. Rong he Najas indica

a Cau Hai dat 2,5 kg 1 m 2. Dac biet c6 52 loai vi tao day, chu yeu tao si c

xac chan huyan 9 ) nhun sinh kh6i lon, trung blnh 794 ctl m 2 va 44,87 9 1 m2 nhung

bac song Huong co 513 ct v 64 9 1 m 2 a nam song Hironq ca th~ nhieu hen, nhung

sinh IU'dngkern hen 2,5 Ian

Th nh phan loai ca phong phu, 162 loai thuoc 57 ho, 15 bo [11] uu the la b¢ ca

bien di cu VaGrnua kho C6 mat loai dac hO'u nhu ca day (Ciprinus central is )

DINH DlJ6'NG VA NANG xuar sa cAp.

Ng on dinh duonq trang kh6i nuoc cua h$ n6i chung la nqheo va phan b6 khonq

deu do trao doi nunc kern, phan tang manh

mat 8,6 mg / m 3, day 9,8 rn /m-'

Nito (N02 ) l<ha thap, cOng c6 hien tuonq rnua mua (1- 4 mg/ m 3 ) gap doi rnua kho

(0,5- 1,5 mg / m3 )

Silic tan (Si03 ) ham IU'Qn c o va bie d ng rnanh 500- 4.000 mg/ m 3 , giau hen a

tang mat, nqheo nhat a Cau Hai (400 - 1 000mg / m 3 ) giau nhat a Tam Giang (1000

-4 000m g / m3 Luong silic ta cao a Tam Giang do nquon song 0 Lau cung cap, m$,

khac do sinh kh6i thuc vat phu du tai day rat thap nen kha nang tieu thu it

0,093% tuonq doi dong deu 6 cac khu Vl/C.Photpho tong so trung blnh 0,169% tvong

Giang a sat cac cia song, ham lucnq dinh dvong cao hen, trung blnh Chc 0,96%, Nts

0,102%, P205 ts 0,217%, Nht 2,03; P205 dt 1,4 Dang chuy P205 ts tang cao 6 cira

Truoi a cira song Huonq, dinh dvong co phan giam thap do ty 1$ cat trang tram tlch

cao So vci cac cua song va dam pha khac ven bign Viet nam, Iv<;mg Nito tong so xha thap va Nito hoa tan k onq cao; lu'ong photpho phong phu hen nhunq cOng khonq cao

so vOi cac cira song, dam pha kha

Ve nquon goc dinh dvong ty so Ch /N trung blnh 8,7 va dat 9,4 6 cac cira song do

vao dam ph a, cho thay Nito cung cap phan nhieu hen tV song luc dia, nguon tai cho tV sinh vat thuy vue cOng rat quan tro q Ty so Chc/P trung blnh 10,1 - 10,7 crumq to rat ro

n uon cung cap nr luc dia chiern uu the

Nquon dinh dvong tLI'th c v t noi kha nqheo do sinh khoi thap, thvong chi 6 rmrc

theo dam ph a, sinh khoi thuc vat noi nqheo nhat 6 Tam Giang noi dinh dv n giau

n at nhung phan tang khac nghiet nhat Dong vat noi co It loai nhvn sinh khoi dang kg,

co vai tro dinh duong quan tronq Sinh vat d y, k ca thirc vat va d¢ng vat, nqheo thanh

phan loai nhunq co sinh khoi Ian do dinh du'ong nen day kha giau va moi tnrcnq song

khac nghi$t khonq tao n n su canh tranh sinh hoc gay gat Thanh phan loai ca phong

phu nhung bien dong Ian theo rnua

Dinh du'ong h$ noi chung khong lc sinh khoi va nang xuat so cap thong qua thuc

n nq xuat dau ra cua he k onq thap va san lucnq thuy san kha cao Dieu dac biet, do

hoan luu ruroc kern, dinh du'ong va co k oi nucc nqheo, nhunq rang tao va co ruroc co

vai tro Ian t<,10nang xuat so cap va co so thirc an ban dau cua h$ Co rurcc co vai tro

tien phong chuyen hoa dinh du'o g va co cua he than dinh d o g hO'uco bang each

tieu thu va chuyen hoa true tiep dinh duong va co tu nen day

Buoc dau, n ng xuat so cap thuc vat noi cua d m pha da dircc danh gia qua thirc nqhiern va tnh toa o Trang dieu kien tha e 10, nhiet do nvcc trung blnh 24 oC, nguon

dinh dU'ong do song dua ra kha p ong phu, sinh Iv<;mgthu vat noi (TVN) 400 - 900,

trung blnh 687mg tvoi/m3 Nang xuat so cap TVN 7 - 1 0mgC / m 3 nqay, trung bln

130mgC/m3.ngay Trang dieu kien nhiet d¢ toi U'U28 C, nang xuat tho co thg dat 200

-250mgC/m3.ngay Nang xuat tinh dat khoang 5 - 55% Nang xuat tho cua TVN 6 cac

thuy vue ven be Viet Nam trung blnh 2 0 - 400mgC/m3.ngay Nhv v~y, rnac du sinh khoi thap, nhung nang xuat so c p cua TVN dam pha TG - CH khonq thap, thg hien 6

hieu qua tu du'ong luon tren 2 va h$ so P/B nqay luon tren 1 (1,6 - 1,7)

M ( n so HI~N TU ' O ' NG ,QuA TRINH DONG U , fC D~C THU CUA H~.

Hien tuonq phan tang rnanh, thg hien su trao doi ruroc kem la mot dac thu cua dam

pha (lagoon) Tlnh chat phan tang thg hien ro 6 rnoi digm trang dam pha vao ca hai rnua

va the hien 6 moi yeu to thuy ho (S%o, pH, TOC, cac rnuoi din dvong) va 6 ca sir

phan bo cua thuc v t noi Qua trlnh phan tang lam cho co sir khac bi$t ve cac yeu to

57

k o Phan tang tao dieu ki$n cho xarn thap man theo tang day vao sau trong song.

C ua mo Ian cue: vao narn 1989 va dong Ian cuoi van thanq 11/1994 Hien nay cira vi r a