Tác động của con người tới môi trường địa chất hệ đầm phá tam giang cầu hai (thừa thiên huế) tuyển tập tài nguyên và môi trường biển, tập 9

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NHA XUAT BAN KHOA HOC V A KY THUA-T

PGS., TS Nguyen Van Tien

TS Luu Van Dieu

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Trang

D inh W in H uy, Trtin D ue Th(;m h,

D 6 D inh C hien, B ui V an V lifJng

2.ponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBAAp dung mo hinh Sbeach tinh toan bien dang dia hinh day khu vue phia 23

nam dao Cat Hai

Trdn A nh t» ,D 6 D inh C hien, N guy€nThQ Stio

IUQngnude vinh Ha long

D 6 T rong B inh

bien moi truong vung bo tay vinh Blle Be)

Trdn D inh Ltin, Trtin V an D ien,

N guy€n V an Thao, D 6 Th? Thu edcbaZYXWVUTSRQPONMLKJIHGFEDCBA H u a n g

tir tai lieu vi~n tharn

Trdn V an D ien, N g u y e n V an Thao

seawifs va sv dung nghien cuu phan bo chlorophyll-a d vung bi~n Vi~t

Nam

Trtiti V an D ien, D anLing Tang, H iroshi K aw am ura

Phong

C ao Thu Trang, Luu van o u « P h< ;t:nV an L u o n g ,

V ii Th? Llju, N guy€n M ai A nh,

D u o n g Thanh N gh?, N guy€n x c a « Tuyeti

Cllu Hai (Thua Thien - Hue)

N guy€n nau ce. Trtin D ue Th(;m h,

N guy€n V ii Turin, N guy€n Th? K im A nh

bd

Trdn D ue Thanh, D 6 D inh C hien

N guy€n Th? P h u a n g H oa

308

T u yln t~ p T a i n g u yen ,va M 6 i tru a n g b ien T ~ p IX

TAC DQNG CUA CON NGUOI Tal MOl TRUONG

1 M dDAU

H~ dftm pha Tam Giang - Cau Hai (TG - CH)' d tinh Thua Thien - Hue la

mot lagun ven bo nude 1<;1 IOn nhat trong s6 12 lagun tieu bi~u d ven bd rnien

Trung Viet Nam trong khoang 11° - 16°vy bac, vdi dien tich mat nude trung binh

vao khoang 216 km2 va cung thuoc loai IOn cua the gidi [3 - 6] Tai nguyen vung

bd bien, d~c biet la tai nguyen sinh v~t,t~p trung chu yeu d cac loai hinh thuy

vue ven bd trong do co lagun That vay, h~ dftm pha TG - CH chua dung ngudn

tai nguyen da dang va giau ti~m nang phat tri~n, co lich si'i khai thac lau d~i va

gift vi tri quan trong trong t6 chuc lanh th6 kinh te tinh Thua Thien - Hue, lien

quan true tiep tdi 5 huyen (Phong Dien, Quang Dien, Huong 'I'ra, Phu Vang va

Phu LQC)trong t6ng s6 8 huyen cua tinh

H~ dftm pha TG - CH Ia mot th~ dia chat hien dai tuong ung vdi mot ki~u

moi truong dia chat ddi bo, nhay earn bien dQng v~ tai nguyen va moi truong va

gay hau qua kinh te - xii hoi nang n~ nhu dii tung xay ra nhieu Iftn do tac dQng

cua cac qua trinh tv nhien cfmg nhu tac dong cua con nguoi dudi nhieu hinh thuc

khac nhau va quy mo khac nhau Tren cd songhien cuu cac d~c trung moi truong

dia chat h~ dftm pha TG - CH, bai viet nay nharn danh gia tac dQng cua con ngiroi

tdi h~ dftm pha thong qua cac hanh dQng ph at tri~n kinh te - xii hQi khu vue va

duoc hoan thanh vdi su h6 tro cua HQi d6ng Khoa h9C tv nhien nam 2002

Co sd tai lieu chu yeu xay dung bai viet nay la ket qua nghien cuu cua cac d~

tai khac nhau do Phan vien Hai duong h9C tai Hal Phong C;hu tri thuc hien trong

nhfmg narn 90 cua the ky truce ma tac giatruc tiep tham gia [5, 13, 14, 16]

T u yin tifp edcbaZYXWVUTSRQPONMLKJIHGFEDCBA T a i n g u yen v a M 6 i t.ruim g b ie n T ifp IXzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Bai viet nay duoc thuc hien tren co sd phuong phap luan tiep can h~ thong

dong luc rnoi truong dia chat, trong d6 c6 dong luc nhan sinh, va phuong phap

phan tich logic tac dong' cua 'con nguoi tdi cac yeu to ~oi truong dia chat va d§.n

suat hai: qua cua n6 [7, 10]

•.•• ",? ",'" "',, ,,'" ,

3 DAC DIEM MOl TRUONG DIA CHAT HE DAM PHATAM GIANG

8 1 1 C ii'u tru e th & n g d itn g

Cac thanh t9-0 m6ng cung cua moi truong dia chat khu vue d<lm pha TG

-CH trong a toa dQ van khoang 16°14' - 16°42' vy b~c va 107°22' - 107°57' kinh

dong bao g 6 m cac da filit, quaczit, cuoi ket, da hoa, da phien mica, da phien set,

da phien luc va porfiroid thuoc h~ t<lng A Vuong (E - Olav), lQ ra d phia nam va

tay nam; cac thanh t9-0 vu n luc nguyen, phun trao thuoc h~ tang Long Dai (0 -S

ld), lQ ra chu yeu d phia tay; da phien set, da voi, bot ket va cat ket thuoc he t~ng

Tan Lam (D1 ~'2 tl), lQ ra d phia tay va phia narn ; da voi thuoc h~ t<lng Co Bai (D2.3

cb), lQ han che' d phia tay; cac d~ granit dang gnai, gr anodiorit thuoc phuc h~ D9-i

LQc (y2 dl), lQ ra d phia tay; gabro - olivin va gabronorit thuoc phuc h~ Nui Chua

(v3nc), lQ ra d phia tay d<lm Cau Hai; granit biotit va granit hai mica thuoc phuc

h~ Hai Van (y34 hv), lQ ra d phia nam d<lm Cau Hai; gabro - diorit, granodiorit va

granit thuoc phuc h~ Ban Giang - Que Sdn(8l

'l - y14 bq), lQ ra d phia tay; cac dagranosienit, sienit va granit, thuoc phuc h~ Ban Chieng (yc3" be), lQ ra d phia tay.

Phan m6ng g~n ket yeu gom cac da set ket, cat ket va cuoi - S9-n ket thui)c h~

t<lng'Dong Hdi (N dh) va mot phan khong dang k~ cac tram tich song, song - bi~n

tu6i Plioxen sdm

Cac thanh t9 - 0 bb rdi cua moi truong dia chat h~ d<lm pha TG - CH gom cac

tr<lm tich song, song - bi~n tuoiPleixtoxen giira - muon (a, am QIl Ill), 19 han che

d ria phia tay dong bang; tram tich song - bi~n, bien tu6i Pleixtoxen muon (am m

QIll); tr arn tich bien, song - bi~n tu6i Ho1oxen sc.n - gifia (m , am QI/·2) va tram

tich song - bien, bi~n - gi6 va bi~n tu6i Holoxene mudn (am, mv, m Q[/)

Cac thanh t9-0 dia chat g~n ket va bd roi n6i tren aa t9-0 nen h~ d<lm pha

TG - CH voi bon don vi cau true nhu hinh 1 [5] I!o m : vue nude, de cat chan, cua

va bd sau

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ti~ h t~ h~ ?n dqi icing ti.9119 iriim (tC n song-bfen. vabl~n.

B D c c o t chon: 2 _H ~ th O n g coirot!n V a b a t b ie n h iin s a ) ,

2 0 ' g o m lra m fic n ail m du vcing nhal , tra n g o l.:lc (m vG ,v 3 ).

c _(?ta : 3 D enio tri;u iin giim cot !rung- t ile , w ing nhat din

xci,;""(m Q N 3),4 _D erua triw xuonq, gem c a t truno.Ln»,

V lin g nhal ( m Q / v 3 ) ,

-( ) B o - sau, 5.B a ; b iiith ilp 9 o m col , b o l, (am Q ,,3 ) 6.S a i

b o 'j C C L O v a d o n g b a n g IItn b iJ ,g o m ca::t,.Q J n tiCJ: c a t, bdt

} t [ (a ab.am T nQ J, 7.C O n ou ven hi" o o m ail n h o , ,rlt

lr:.lng.m ciu ~{ng m u o L ( m ( v ) G ''I '· 'J 8 : C oe lh t in r Lao

Cau true ngang rnoi truong dia chat khu vue d~m pha TG - CH phan ddi doc

theo bo bi~n dinh huang tay bac dong nam, phan biet thanh 3 he: h~ moi trucng

dia chat (MTDC) bi~n, he MTDC bo bi~n va h~ MTDC luc dia (hinh 2)

H~ MTDC bo bien g6m hai kieu: ki~u MTDC c6n - dun va bai bi~n va ki~u

MTDC lagun ven bo Kj~u MTDC c6n - dun va bai bi~n tuong ling vdi de cat chan

lagun, phu ki~u bai b6i lagun, phu ki~u long chao lagun va phu kiJu cua song

chau th6 lagun Phu kiJu MTDC cua lagun di[tctrung bci dong luc dong chay, c6

Phu kiJu MTDC bai b6i lagun g6m hai dang: bai b6i cao dang them lagun, dac

T uyin tiJp T ai nguyen va M 6i t edcbaZYXWVUTSRQPONMLKJIHGFEDCBA r u a n g bie'n T iip IXzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

nho, bai boi thap dang bai trieu vdi che' dQ tich tu tr~m tich nho heat dQng cua

quy mo ldn nhat, chiern phan ldn khong gian MTDC pha Tam Giang, d~m Sam

-An Truyen, Thuy Tu va darn C~u Hai Dac trung cho phu ki~u nay la qua trinh

lang dong tr arn tich hat min dQ uct cao tuong lagun thuc thu va min dan theo dQ

sau Tram tich hat min d day c6 dQ udt rat cao, dat tdi 81,8% d pha Tam Giang,

song Huong va cua song Truoi - D9-i Giang, dac trung bdi uu fhe' dong' luc song,

tri6n qua trinh Jliy h6a vdi vai tro dang k~ cua thuc vat thuy sinh

o 2 8 10

'''''~

IBIEN80N G _

H 2 6 He MTOC 00 bi~n: 2 - Ki~u MTOC

Iacun yen t-O J - Phy kiell cita iagun.

~ - ~hu kle:J b5, b6 iJ'-:lun, 5 - Phu kieu

lonq c:dlo laqun 6 - 0hu kleu ora song

7 - }\lcu f\\TPC 06ng h~ng 'lien bien,

S - Kieu MTDC dc":: va nut "tr'lap.

T u yin tijp T a i n g u yen va M 6 i t ru irn g b ii'n T ijp IXzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Lagun venponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBAbo, mot ki@u moi trucng larig dong tram tich hien dai (Evans et

al, 1973, Reineck and Singh, 1975[5]), phat tri@n phan di thanh cac phu ki~u

tuong ling vdi cac phu ki@u MTDC (bang 1)

tram tich

Cira s6ng Huong Phu kieu chau th6 lagun vat chat hiruca d¢ Hat cao (>60%) rnoi

Cira s6ng Trudi - Dai Giang twang tram tich khir yell

Phu kieu cira lagun vo sinh vat d¢ uot rhap, m6i twang tram richCira Thuan An oxy h6a, phat trien delta trieu len 0 cira TII

Hien delta trieu xuong 6 cira Thuan An Lang dong tram tich hat vira (cat nho, bot), H¢ thong bai boi yen bo Phil kieu bai boi lagun d¢ 1I0t thap, tao thanh biii boi cao dang them

ngap IG ve mua mira, bai boi thap dang bai trieu, m6i tnrong tram tich khir trung blnh

Dam Thuy 'ru Phil kieu long chao lagun (>60%), phan di co h9C min dan theo do sau,

N g u o n : Nguyen Hii'u ce. 1996 [5] c6 b6 sung.

H~ MTDC luc dia g6m hai ki@u: ki@u MTDC d6ng bang ven bi@n va ki@u

MTDC d6i va mii thap Ki@u MTDC dong bang ven bi@n dac trung bdi Illng dong

tram tich aluvi lap d~y cac dang dia hinh trung thap t6n tai tU truce Holoxen

muon, trong d6 c6 h~ thong cac lagun c6, trong pha ~ theo nguyen ly phat tri@n

d6ng bang ven bien cua Strickland (1926) [5] d noi giau b6i tich cat va cac dang

tich tu cat Qua trinh nay vAn con tiep tuc boi heat dong dia chat cua cac song d6

VaG dam pha Ki~u MTDC d6i va nui thap phat tri~n dac trung qua trinh xarn

thuc b6c men va r-lia troi be mat cac thanh tao dia chat truce D~ tu, mot mat

hinh thanh ph6 bien cac th@ tich tu deluvi, proluvi, bib b6i ven song nhirng mat

khac cung cap mot lucng IOn b6i tich cho d~m pha va bi@n

3 2 1 D ( m g iu c n 9 i sin h

Moi truong dia chat he d~m pha TG - CH chiu a nh huong cua che' d9 nang

ke" thua va nang phan di phuc tap Ki@u MTDC c6n - dun va bai bi@n, lagun ven

T uyln tij,p T eii n g u yen vei M 6i t ru irn g bien T ij,p IXzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

bd va d6ng bang yen bi~n phat tri~n tren ddi sut ha tuong doi trong D~ tU vdi toe

d9 nang trung binh 0,12 - 0,15mm/nam (Le Due An va Ma Kong CQ, 1979 [5]) ben

canh khoi nang tay Hue' (toe d9 van dorig 0,3mm/nam) va khoi nang Bach Ma (toe

d9 van d9ng 0,5mm/nam).ponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBAd phia nam H~ MTDC bi~n phia ngoai phat tri~n tren

ddi cang gian (Le Nhu Lai, 1995 [5]) chuyen tiep vdi ddi rift song H6ng Toan b9

cac thanh tao dia chat khu vue bi pha huy manh bdi cac h~ dirt gay hien dai ph at

sinh tU h~ dirt gay sau A Ludi, cac dut gay phat sinh cue b9 va cac dirt gay thuoc

h~ dut gay Hili Vap - Son Tr a [12] Phat sinh tU h~ dirt gay sau A Ludi, e6 cac h~

dut gay Pho Trach, h~ dirt gay Hue', h~ dirt gay Rao Trang, Day la cac h~ dut gay

truot phai, dinh huang a vy tuyen (hinh 3),

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I.edcbaZYXWVUTSRQPONMLKJIHGFEDCBA V d i 1'1ong U in H i;; f? D /d d i s ,II h 9 tU d n g d o i

Iron9 D ' I e i',2.B iflg a y phim nh anh: Iii'h ~ dtit

gay ,au -H lid; va h u d n g D icn I l'r ld l, x a c c in h /

d L /d o a lJ ,3 D !ilg o y phalsi";' cueba va htJdng

djch I r u d i X I ic G inn /D L /d o c in 4 _ B w t hij.nvan

d { m g n a n g c u C bg d a n g vom 5_ T rungL ivnruitdli/ d g 1'/' \

vtihddngciW daow akh< niIl,6.cnanlizm 1!ong ao rra \

o u a th w N D H < IJ H tfU e V v O T D L im 1995. ,'LO \/

Tam Giang - Cllu HaiTrong cac dirt gay phat sinh cue b9, di~n hinh la h~ dirt gay song Ta Trach,

truot phai va dinh huang a kinh tuyen (BTB - NDN) e~t qua pha Tam Giang, h~

dut gay song Hiru Tr ach bieu hien truot trai, dinh huang DB - TN e~t qua d~m

Thuy Tu Thuoc he dut gay Hili Van - Son 'I'ra, cac dirt gay chinh e6 bi~u hien

108

T u yln tg p T a i n g u yen va M 6 i tr edcbaZYXWVUTSRQPONMLKJIHGFEDCBA u a n g b iin T g p IXzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

truot phai, dinh huang TB - DN chia cat khci Bach Mil va d§.m Cau Hai Van

dong nang va heat dong cua cac h~ dut gay pha huy hien dai dil lam xuat hien

d§.m pha, nhu vorn nang Phu Yang, vorn nang Thuy Thanh

3 2 2 D i}n g 1 1 /cn g o a i sin h

H~ darn pha TG - CH la b6n hQi luu cua h§.u het cac h~ thong song 'I'hira

Thien : Hue (tru h~ thong song Xe Xap d mien tay), hang narn tiep nhan t6ng

trao ' d6i voi bien Qua trmh san bang dia hinh dong b~ng ven bi~n va lip d§.y

lagun ven bo di~n ra lien tuc thong qua cac co che: tich tu bai b6i chau th6 lagun

pha vdi t6c dQ van khoang 2, 17 n~m/nam [14] nho hoan luu noi tai va trao d6i

nude giira bi~n va d§.m pha, va co che' san bang bo cua bien vdi luong xuat chuyen

b6i tich doc bo do s6ng van khoang 3,5 trieu ta'n/nam, trong d6 uu the ve phia

nam 0,5 tr'ieu ta'n/nam, d~n den trang thai va vi tri cua d§.m pha khong 6n dinh

[5, 14, 15, 17]

Trai qua lich s~ phat trien dia chat khu vue lau dai trudc Holoxen (giai

dean tien lagun) va Holoxen (giai dean thanh tao lagun) tren ddi sut ha tuong d6i

su kien md cua thu hai tai lang Hoa Duan van nam 1404, va h~d§.m pha TG

-CH dang phat tri~n d giai doan trucng' thanh [5] Tu khi mo cua Hoa Duan, cua

trd nen khong 6n dinh, moi truong lang dong tram tich lagun ph an di manh giira

Luc mdi hinh thanh, h~ d§.m pha TG - CH rong hon Qay gid nhieu (Le Quy

Don, 1976 [5]) va trong su6t giai doan phat tri~n tre, chi t.6n tai mot.cua Tu Hien

tdi Ha Trung Ngoai bai b6i dang them, can xuat hien hili b6i dang dao d cu6i

darn Thuy 'I'u c6 ca'u true hinh thai delta rfft di~n hinh (khu Ba C6n) Phat tri~n

Tu Hien chiu anh huong cua thuy trieu c6 bien dQ cao hdn' thiiy trieu d cira

Thuan An nguon nuoi b6i tich cho bai b6i ven bd d§.m Thuy Tu va bai b6idljlng

T u yin t~ p T a i n g u yen va M 6 i tr edcbaZYXWVUTSRQPONMLKJIHGFEDCBA u a n g b iin T ~ p IXponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

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•zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

dao d phia cuoi khong con dang k~ Thay VaG d6 la su IOn nhanh cua bai b6i chau

th6 song Huong Iffn tien vg phia cua Thuan An Cac dac trirng ly h6a khoi nude

d~m pha cang giarn nhanh tinh chat d6ng nhat gifta cac ti~u vung cua song chau

th6 lagun, gifia cac cua va th~m chi giira cac bQ phan khac nhau (Tam Giang,

Thuy Tu, C~u Hai) cua long chao lagun

Lagun ven bo, mot b6n tich tu hien dai, tfft yeu trai qua cac giai dean phat

tri~n tre, trucng thanh va suy tan d~ hoan thien cau true hinh thai d6ng bang

ven bi~n nhu da tung xay ra trong lich stt phat tri~n dia chat d6ng bang ven bi~n

mien Trung Vi~t Nam [3] Ngoai cac qua trinh dQng luc tu nhien, cac lagun ven

bd hien nay n6i chung va h~ d~m pha TG - CH n6i rieng con chiu tac dQng manh

cua con nguoi ngay cang gia tang (dQng luc nhan sinh) dudi nhieu hinh thuc khac

nhau Vi vay, khorig th~ du bao khoang thoi gian suy tan cua h~ d~m pha TG

-CH khi chi udc dinh toc dQ bing dong tram tich nhu hien nay ngoai viec cho rang

h~ d~m pha TG - CH tiep tuc phat tri~n phan di manh trong thoi gian du dai

trong digu kien dang cao muc nude dai duong the gioi

Tam Giang - ciiu Hai

3 3 1 T iL i n g tiyen

Tai nguyen MTDC khuvuc d~m pha TG - CH duoc dg cap tdi trong pham vi

ki~u MTDC c6n - dun va bai bien, ki~u MTDC lagun ven bo va ki~u MTDC d6ng

bang' ven bien Theo quy luat chung, tiern nang tai nguyen vung be bi~n tap

trung chu yeu d cac loai hinh thuy vue ven bo, trong d6 c6 lagun, va uu the tiem

nang tai nguyen sinh vat Doi vdi vung bo bi~n mien trung Viet Nam, noi c6 dieu

kien tu nhien khac nghiet va tai nguyen thien nhien ngheo kiet, tiern riang tai

nguyen va gia tri stt dung cua cac thuy vue ven bo, trong d6 c6 h~ thong d:1m pha,

cang c6 y nghia va c6 vai tro quan trong trong quy hoach phat tri~n kinh te - xa

hQi khu vue [6] C6 th~ khai quat cac dang tai nguyen thien nhien lien quan tdi

cac don vi cau true MTDC khu vue d:1m pha tren bang 2 vdi gia trj tai nguyen ldn

nhat, ca tai nguyen sinh vat va phi sinh vat, thuoc vg ki~u MTDC lagun ven bo

Mac du gia tri stt dung ldn nhung tiern nang khai thac chi c6 han dinh d~ duy tri

su 6n dinh co cau tai nguyen va phat tri~n cac gia trj tai nguyen, d~ han che' nay

sinh cac van dg dia chat moi truong

3 3 2 T a i b itn

Tai bien MTDC vung bo bi~n luon la van dg dia chat moi truong' birc xuc,

anh hudng toan dien toi su phat tri~n kinh te - xa hoi vung bo bien Tai bien

MTDC vung bo bi~n Thua Thien - Hue chu yeu la cac dang tai bien dia chat

ngoai sinh, duoc trinh bay khai quat tren bang 3 theo each phan tich logic d~n

110