Tap chi Khoa hoc va Cong nghe Bien; Tap 14, So 3; 2014: 265-271 DOI: 10.15625/1859-3097/14/3/3983 http://www.vjs.ac.vn/index.php/jmst
O NHIEIVl MOI TRLTCiNG KHU NUOI CA BIEN BANG LONG BE DIEN HINH: TRLT^NG HOP NGHIEN CUtJ TAI CAT BA - HAI PHONG
Le Tu^n Son'*, Tran Quang Thir', Nguyen C6ng Thanh', Pham Hodng Giang^ Tran Van Thanh 'Vipn Nghien eiiu Hdi san-Bg Nflng nghiep vd Phdt frien Nong thon
^Tradng Dai hgc Khoa hpc Tu nhien-Dai hgc Quoc gia Hd Ngi 'Email: [email protected]
Ngdy nhdn bdi: 7-5-2014
TOM TAT: Trong nhung ndm gdn ddy, hogt dong nuoi cd biin bdng long be tgi Cdt Bd - Hdi Phong dang bt dnh hu&ng b&i 6 nhiem moi truang nu&c. Hdm lugng DO ti-ung binh vdo miio mug thdp han gdi hgn cho phep xdy ra tai Bin Beo gid tri bang 4,67 mg/l, Tiing Trang (4,71 mg/l), Vung Gid (4,89 mg/l) Ngodi ra, hdm luang N-NHf trung binh gdp 1.05 ldn so v&i QCVN W:2008/BTNMT. Cbl sd chdt lugng nuac CCME - WQI vao miia mua dao dpng 46 - 61, phdn dnh chdt lugng nuac cd bieu hien 6 nhiim, khong thugn lai cho hogt dong nuoi cd bien. Nguyin nhdn la do hdm luang cdc chdt hihi ca vd dinh duang trong nudc cao. chdt thai tir hogl dpng nuoi hdi sdn, dich vu du lich vd mpt phdn tir nguon bi 6 nhiim trong luc dia chdy ra.
Tir khda: Cdt Ba. chi sd chdt liroTig nu&c, nuoi cd bien bang long be, 6 nhiim.
DAT VAN DE
Nhung nam gan ddy, nghe nuoi ca bien bdrig I6ng be tai Cat Ba, huyen Cat Hdi, thdnh ph6 Hai Phong dang co xu the phat frien kha manh. Nam 2007^ khu vyc dao Cat Ba co 531 be gfim 7.697 6 long, ehu yeu nuoi ca long va tora, phdn bd tai vinh Cat Bara Ben Beo va vmh Lan Ha [6], Tuy nhien, do nhieu nha be phat fri6n frr phdt, khdng tudn thii edng tac bao ve moi tradng frong nuoi frong, gop phdn lam suy gidm chat lugng nudc tai Cdt Ba. Chinh vi vdy, viec ddnh gia chdt liigng mdi tradng nudc t^i viing nuoi cd bien bang long be can phdi duoc tien hanh thudng xuyen, lien tyc nham cung cdp thong tin ve diln bien ehat lugng moi tradng hay cdc nguy ca d nhiem, suy thodi cua thiiy vuc; tu dd, co bien phdp bdo ve nguon nudc va ban che thiet hai do 6 nhiem gdy ra.
Mue tieu cua bai bao la ddnh gia chat luang moi tmdng nudc d khu vyc nuoi ed bien bang long be tai Cdt Ba tiong nara 2013 thong qua
ehi so chdt lugng nudc (CCME - WQI Canadian Council of Mimsters of the Environment Water Quality Index). Qua do, gop phdn ldm co sd cho viee quy^ hoach, phdt trien ben viing hoat dgng nuoi trong thuy hdi san va cong tdc dy bao raoi tmdng tai dia phuang frong nhung nam tiep theo.
PHU'ONG PHAP NGHIEN CLfU Tai lieu, pham vi nghien cihi
Nguon so lieu dugc sir dung tir ket qua quan frde thudng nien do Vien Nghien ciru Hai sdn thyc hien vdo thang 5 vd 9 nam 2013 - dai dien cho miia kho vd miia mua. Ngoai ra, nhom nghien cim tham khao them mdt so tai lieu lien quan den moi tmdng khu vuc bien Cdt Ba - Hdi Phdng.
Tieu chuan su dyng de tinh todn vd ddnh gid chat lugng nudc la QCVN 10:2008/BTNMT dp dung d6i vdi nudc bien ven bd cho muc dich nuoi trong thiiy sdn va de
Le Tuan San, Trdn Quang Thu,...
xudt ciia du dn KT 03 -07 (vdi mot so chi tieu khong CO trong quy chuan).
Pham vi nghien ciiu g6m 5 diem (Ben Beo 1 -CBl,B6n Beo 2 - C B 2 ; Tilng Trdng-CB3;
Hdi Qudn - CB4 vd Viing Gia - CB5) d khu vyc nuoi ca bien bang long be tai Cat Ba - Hdi Phdng (hinh 1).
:r;::;;'.i:ss;j
1
, / • * ^
Hinh 1. Vi tri cdc diem nghien ciiu khu vyc nuoi cd bien bang long be
tai Cat Ba - Hai Phong Phu'cng phap nghien cuu Phuang phdp phdn tich
Nhom thdng so moi tradng nen (nhiet do, do mudi, DO, pH, dp due) cua nudc bien dugc do tai hien tradng bang cac thiet bi do nhanh:
WTW Oxi 330i, Schott Cond/pII/LF12, Turbidity HACH.
Hdm lugng muoi dinh dudng (N-NO^', N- NOj', N-NH4^ vd P-PO4'") tiong nude dugc phan tieh tai phong thi nghiem bdng phucmg phap frac quang fren mdy quang pho DREL/2010-HACH(My).
Thyc vat phii du dugc soi fren kinh hi6n vi phan tich (loai HUND - Wetzlar, NIKO - eclipse TSlOO) dya tren phuang phap so sanh hinh thai.
Vi sinh vat: Coliform bdng phuong phdp MPN (Most Possible Number) cay tiong raoi tmdng long.
Phuang phdp xir ly so lieu
Cdc so lieu do, phan tich chdt lugn^ mdi tmdng dupe xii ly bang phuang phdp thong ke
tren trinh ti?n ich Pivot Table and Pivot Chart Report cua Excel phuc vu cho vi8e ddnh gid chdt lugng moi tmdng.
Chi sd da dgng lodi H'
Ddi vdi thyc vdt phu du, sii dung chi so t6ng da dang lodi H' (theo Shannon - Wiener 1963, fricli dan bdi Trdn Luu Khanh, 2009) dh ddnh gia chdt lugng mdi tradng cung nhu muc d nhilm eho tirng thuy vuc nghien ciiu. Cach tinh chi so H' va phan mire chat lugng moi tradng nhu sau:
Cdng thiic tinh:
H'--iP,logP,
Trong do: P, = N,/N, N, Id so cd the eiia loai thir I, N la tong so lugng ca the cua cac lodi.
Chi sd chdt luang nu&c CCME- WQI Chi so chat lugng nudc (Water Quality Index - WQI) Id mpt chi so td hop dugc tinh todn tir cdc thong sd chat lugng nudc xdc dinh thong qua m6t cong thiic toan hgc. Chi so WQI dua ra cdi nhin tong the ve ehat lugng nude yd cung cdp thong tin mpt each don gidn, de hieu cho cpng ddng ma khong can kien thirc chuyen sdu.
Bai bdo sii dung 5 thong sd (N-NO2', N- NOj', N-NH4", P-P04^vd DO) de tinh CCME- WQI theo phuang phdp ciia sd tay hudng din ddnh gia CCME - Water Quality Index 1.0.
Cdch tinh chi s6 chdt lugng nude CCME - WQI cy the nhu sau:
Chi s6 CCME -WQI la ham eiia 3 ehi s6 phu khac nhau: F, (Pham vi) la phan tram cac thong s6 vugt GHCP; F2 (Tdn sudt) la phdn trdm sd mdu vugt GHCP; F3 (Do lech - Bi6n dp) la dp lech giiia cdc mdu vugt gidi hgn so vdi GHCP, CO gia tri tir 0 din 100 dilm dugc tinh bang e6ng thuc sau:
0,0lnse-l-0,01
nse la thuang cua tong dp lech chudn tuang doi so vdi tieu chuan fren tdng tdng so mdu phdn tich.
6 nhilm moi tradng khu nuoi ca biln . Gia tii cua chi s6 CCME - WQI tinh theo
c6ng thiic sau [1]: CCME WQI = 100
1,732 Bdng 1. Bang danh gid chat lugng moi tradng nude theo chi so CCME - WQI _ Chat lu-yng nipiyc Giai thich
Rat tot ^'^^' iLTpng nuo'c dupe b^o v|, thuc su khong bj de dpa hay lAm suy gram;
di^u ki$n a day cdn rat gan voi he tu nhign hay o muc nguyen thuy j ^ [ Chat lupng nuoc dupe bao ve, miic dp bi de dga hay lam giim khong Ion;
di^u kien 6 day hiem khi vupt ra khdi he \^^ nhien
Tnjna binh *^^^' ''^'^"9 nisac thuong dupe bao v? nhung ddi khi bi de dpa hay suy giam;
dieu ki#n 6 day ddi khi vupt khdi he ty nhien hay mi>c dp mong muon Bieu hien CLJa s\r 6 Chat lupng nuo'c Ihudng bi de dpa hay suy giam, dieu kien 6 day thud-ng vupl
nhi§m khoi he tu nhien hay mi>c mong muon
0 nhiem ^^^^ lupng nu&c iuon b| de dpa hay suy giam; dieu ki^n d dSy ludn vupt khoi he tl/ nhign hay muc mong muon
KET QUA NGHIEN CUtJ Bien d9ng ham lirgiig cua cac thong s6
!005 lOM 2007
Hinh 2. Ham lugng DO d frong nudc khu vyc nuoi cd bien bdng long be tai Cat Ba tir 2005 - 2013 (Giai doan 2005 - 2012 tir Trdn Quang
Thu va nnk (2013) [2]) Nhdm thdng so mdi tru&ng nen: Nhiet dp vd dp mudi cua nudc bien d khu vye Cdt Bd ndm 2013 cd sy thay doi theo mua. Nhiet dp dao dgng trong khoang 25 den Sl^C, eao vao miia mua; ngugc lai, dp muoi cua nude bien co gia tri thdp vdo mtia raua. Ndng dp oxy hoa tan trong nudc dao dgng trong khodng 3,64 5,91 mg/l; trang binh DO co gid tri thdp vao thdi diera NL (nude ldn) va vao miia mua. So sanh vdi ket qud nghien cuu ciia Tran Quang Thu, Le Tuan San va nnk [2] giai doan 2005 - 2012, ham lugng DO trang binh do dugc tiong nam 2013 giam xudng han 1,2 ldn so vdi nam 2005 va cd xu hudng gidm nhe qua cac nam.
Theo s6 lieu tir nam 2009 din nam 2012 [2], n6ng dp DO cd gid fri thdp vdo miia mua,
tuang ty idiu ket qua frong nam 2013. Nguyen nhdn cd the la: vdo raua mua, nhiet dp thudng cao, qua trinh chuyen hda N-NHi"^ sang N-NO2"
vd N-NO2' sang N-NO3" xay ra nhanh va tieu thy oxy hda tan, dan den sy suy giam oxy frong khu vuc nudi. Theo Traong Dinh Hoai (2014), nhiet do, dp man va vi dp cao (dp sudt thdp), oxy hoa tan trong nude cdng thdp. Ngodi ra, nhiet dp cao thi nhu cau oxy cua ca tang, Tinh rieng nam 2013, ham lugng DO d nhieu diem quan frac co gid tri thdp ban GHCP (5,0 mg/l) theo QCVN I0:20b8/BTNMT nhu Bin Beo 2 (vao miia mua: NL - nudc Idn - 4,25 mg/l; NR - nudc rong - 4,32 mg/l), Timg Trang (miia mua:
NL - 4,05 mg/l; NR - 4,57 mg/l). Hau hit cdc mau cho gid tn DO vugt GHCP chii ylu dugc ldy tu tang ddy. He qua cua ham lugng DO trong nudc bien thdp la qua frinh oxy hda Amoni tiong nudc dien ra chdm han. De dam bao nhu cdu oxy hoa tan cho doi tugng nuoi, nam 2012 mot so 6 long nuoi tai Ben Beo da phdi diing mdy sue khi de cdp oxy cho cae doi tupng nuoi (Trdn Quang Thu vd nnk [3]). Cdc thong so pH, dp due it bi bien dpng.
Neu nude thudng xuyen thieu oxy < 3 mg/l ca se giam dn, chdm ldn, kho phat due. Ham lugng DO tir 0,3 den 1 mg/l: ea eo the song neu nhiet do nudc thap va chet neu nhiet do cao [4].
Ngoai ra, dp sdu mye nudc be nudi dao ddng tu 4 - 6 m, bien do dao dgng thuy trieu ciia bien Cdt Ba rdt ldn, tir 3,0 - 3,5 m, trong
267
Le Tuan San, Trdn CJuang Thu, ...
khi dp sdu cua long nuoi tir 2,5 - 3,0 m. Do vdy, vdo thdi dilra thiiy frilu xuong thap, day long nudi chi each day bien khoang 0,5 - 1,0 m (hinh 3) [4], thdm ehi co khu vyc day 16ng nuoi cham sat nen day bien. Dilu nay lam tang kha nang tich luy ehdt hiru ca (thitc an thua) d tang ddy va tao dieu kien eho vi khuan yem khi boat dgng manh, gdy ra cac khi dgc, frong do co NHj. Cac hoat dgng nuoi cd ling be, tu hai, hdu ... khong diing quy trinh ky thudt, long be san sat lam han ehe dong chay, tang nguy co bung phat va lay lan dich benh.
(1) ham lugng cdc chdt huu ca frong nudc cao dac biet la thuc an thira, ddn den qua trinh tu 6 nhilm do su phdn huy chdt hiru ca la lirng trong nude, (2) ldng dpng d frdm tich frong dilu kien yim khi d cac khu vyc nudi va (3) tit nguSn thai frong luc dia chdy ra.
Hinh 3. Vi tri long nuoi d hai thdi diem thuy trieu khde nhau [4]
Nhom thdng so cdc mudi dinh duong: Hara lugng N-NO2" vd N-NO3" trung binh co gia tri thdp han GHCP theo tieu chudn de xudt cua de tdi KT 03 - 07. Vao miia kh6, toan bg diem quan trac deu eho nong dp P-P04^" nho ban GHCP (0,1 rag/1). Vdo mua mua, ham lugng P- P04^" vugt GHCP, cu the, liie NR ham lupng P- P04^" eao nhdt d Bin Beo 2 (0,23 mg/l) gap 2,30 ldn so vdi tieu chudn. So sanh vdi nam 2012 [2], ham lugng P-P04^" tmng binh tdng len 1,55 lan vd co xu hudng tang len ro ret qua edc nam (hinh 4).
Trong cac thong so dinh dudng glc Nita, hdm lupng N-NHi"" nam 2013 cao nhdt; tuong ty vdi ket qua nghien ciiu eua Tran Quang Thu va nnk [2], d viing biln Hdi Phong - Quang Ninh. Hdm lugng N-NH4^ frong nam 2013 cao nhdt la 0,146 mg/l gap 1,46 ldn so vdi QCVN 10: 2008/BTNMT. N6ng dp N-NH4^ c6 gid tri cao d edc khu vue: Bin Beo 1 (0,103 - 0,133 mg/l), Bin Beo 2 (0,093 - 0,137 mg/l) va Timg Trang (0,089 - 0,146 mg/l). Nguyen nhdn la do
Hinh 4. Bien ddng ndng dp dinh dudng hoa tan trong nude khu vye nuoi cd bien bang long be tai Cdt Bd nam 2005 - 2013 (Giai doan 2005 -
2012 tham khdo [2])
Theo Nguyen Van Nguyen (2013) [5], nong dp dinh dudng trong nudc cao la mpt frong nhirng nguyen nhdn gay ra hien tugng thiiy trieu dd tai vung bien Cat Bd - Hdi Phong.
Trong 2 nam 2011 - 2012, da ghi nhdn 5 dot bung phat thuy trilu dd fren dien rong, gdy thiet hai ldn cho nuoi trong thuy sdn.
Chi tieu Coliform 0 hdu het cdc diera nghien Cliu tiong nam 2013 deu kha cao va vugt GHCP - 1.000 MNP/100 nil tiieo QCVN 10:
2008/BTNMT. Ddc biet, vdo miia raua, liic nudc rdng tai Ben Beo, Hai Qudn vd Vung Gia, mat do Coliform cao hon GHCP 1,1 ldn.
Danh gia chat luwng mdi trirdng nirdc t^ng the dya tren chi so H '
Vao mua kho, chi so H' ldn nhdt dat 4,41 a khu Ben Beo 1: moi tradng nude khdng bi 6 nhiem. Ngugc lai, tai Timg Trang va Hai Quan, gid fri H' nhd han 1 (tuang duang 0,53 va 0,87): chat lugng moi tradng nudc bi 6 nhieni ndng. Vdo mua mua, gia fri H' dao dgng tiong khoang 2,79 - 3,70: moi tmdng nudc khong bj 6 nhiem hoac 6 nhiem loai tmng binh Beta (P - raesosaprobic). Qua do, cho thdy nudc tai khu vuc qudn dao Cdt Bd dang bi d nhilm cue bp va CO nguy ca 6 nhilm cao ban vao miia kho.
O nhiem moi trudng khu nuoi ca bien . Bdng 2. Bdng chi s6 H' d cac khu vye nghien eiiu tai Cdt Bd nam 2013
Tho-I g i a n
Miia mua
D i e m q u a n trac — CB1 CB2 CB4 CB1 CB3 CB4 CBS
T h i r c v ^ t p h u d u Mat dO (tb/m^)
167 925 460.377 13 820 755 2 283.019 33 443 396 28.773 585 3,547,170
H' 4,41 2,99 0,53 0,87 2,79 2,92 3,70
D a n h gta chat l u p n g nu'o'c N u a c t u c n g doi sgch C> nhiem tmng binh Beta
0 nhiem nang 0 n h i l m tnjng binh Beta
Khdng 6 nhiem
Chi s6 ch^t lu'gng nirdc CCME - WQI Chi s6 chdt lugng nude CCME - WQI dao ddng trong khoang 46 - 75, tmng binh 64. Gid tii CCME - WQI vdo miia khd luc NL va NR xdp xi nhau, the hien chat lugng nudc d muc trung binh. Ngugc lai, vao miia mua, CCME - WQI dao dpng trong khodng 46 - 61: chdt
lupng mdi tradng nudc tai Cat Ba dang co dau hieu eua sy 6 nhilm. Nguyen nhdn ldm gidm gia tri WQI chu yeu do: vdo raiia mua, so lugng thong sd vugt tieu chudn (Fi) vd sd mau phdn tich khdng dat yeu cdu (Fj) nhieu ban so vdi mua kho; keo theo dd la do lech ciia cac mdu vugt GHCP ldn (F3).
Tfnh WQI Gia tn chi
so phu W Q I
F, 40
Bang 3. Gia tri chi
Mua k h o N u o c Id'n
F2 F3 F, 20 2,74 40 74
sd chdt lugng nudc
Nuo'c rong F2 F3 17,24 4,58
75
CCME - WQI nam
Miia Huiyc Ion F, F: F3 60 30 5,21
61
2013
mu'a F, 80
N u a c rdnq F j 44,83
46 F3 17
So sdnh vdi ket qua CCME - WQI dugc dua ra tiong bdo cdo [2] cua Trdn Quang Thu vd nnk, chi so chdt lugng nudc nam 2006 - 2007 ldn lugt la 93 va 90: cho thdy moi tmdng nudc d miic tot nhdt, thuan lgi cho hoat ddng nuoi hai sdn. Giai doan tii nam 2008 den ndm 2013, gia tii CCME WQI < 80 va gidm ddn qua cdc nam: phan dnh chat lugng mdi tradng nude dang cd xu hudng bi 6 nhilm (hinh 5).
Hinh 5. Gia tri chi so CCME - WQI trong nudc khu vyc nuoi cd bien bang long b^ tai Cat Ba
2006 - 2013 (Giai doan 2006 - 2012 tham khao tai [3])
Nguyen nhan gay 6 nhiem
Hoat dpng nuoi thuy san: nguon thai tu NTTS chii yeu la chat dinh dudng va hiiu ea, do Iugng thiic an ehu ylu Id ed tap, duqc che bien thu cong^ mgt phdn ca an khdng het, roi xudng ddy bien tich tu d do v.i mpt phan froi sang eac khu vyc khac.
Hoat dpng du lich^ khai thdc va dich vu thiiy san: nam 2006, tong lugt khach du lich den ddo Cat Ba khoang 500 nghin ngudi, nam 2007 tang len gdp 1,5 ldn - dat 729.000 lugt khach. Udc tinh nam 2020 dan so ddo Cdt Ba tang len 20.120 ngudi, thu hiit khodng 1,9 frieu lugt khac du lich raoi ndm [6]. Keo theo do la so lugng rac thdi phdt sinh tir dan cu va khdch du lich tang len trong khi vdn de thu gom va xii ly rdc thdi chua triet de. Qua kiem fra cua Doan kiem tia lien nganh huyen Cdt Hai, 100% nha hang, be ndi deu co nha ve sinh, nhung khong CO he thdng Igc, he thong xir ly ma xd thdng xudng bien. Hoat ddng khai thdc va du lich sir dung edc tdu loai nho la mot trong nhting nguyen nhdn gay d nhiem ddu.
Le Tuan Son, Tran Quang Thu,...
Nguon gdy 6 nhiem tii luc dia: Men tai viSc quan ly, kiem sodt eac chat 6 nhiem tir nguin luc dia chua hieu qua. Hdu het cdc nguon 6 nhilm chua dugc xii ly tmdc khi xa ra moi tmdng.
Chi tinh rieng vung Cat Bd, kha nan^ tiep nhan cac chdt 6 nhiem da qua tdi vdi hau het edc thong s6 nhu BOD, COD, NH4"' vd NO2".
Ngoai ra, khd ndng dat tai doi vdi P04^" va TSS tiictng ling la 51,22% vd 73,34%.
Tai lircmg ch3t 6 nhiem
ftftrr
NOJ- poas-Hinh 6. Muc dp dat tdi vdi cdc thong sd moi tradng tai vung Cat Ba [6]
KET LUAN VA KIEN NGHI
Gid fri cdc thong so mdi tmdng nen ca bdn d vimg bien hdu het deu nam frong GHCP theo QCVN 10: 2008/BTNMT va tieu chudn dl xuat ciia dl tdi KT 03 - 07. RiSng^dm lugng DO frong nude d 1 sd diem quan trac nhu Ben Beo, Timg Trang ... nhd hem GHCP (5,0 mg/l) va co gia tri thap vao miia mua.
Nong dp cdc thong s6 dinh dudng (N-NO2', N-NO3 va P-P04^") tmng binh thap ban so vdi GHCP, rieng ham lugng P-P04^" trung binh vdp miia mua vugt tieu chuan hon 2 ldn. Thdng s6 N-NH)^ luon CO nong do cao nhat so vdi ede thong s6 dinh dudng goc Nita va co gia fri tmng binh vugt GHCP tai Bin Beo 1 vd 2, Tiing Trdng.
Chi so chat lugng moi tmdng nudc CCME - WQI vao miia mua dao dgng tii 74 - 75, miia mua (46 - 64). Chat lugng nude vao miia kho CO bieu hien 6 nhiem, khong thuan lgi cho hoat dpng nudi hai san.
Chi so H' phan dnh chdt lugng moi tmdng nudc Cat Ba bi 6 nhiem cue bp, ddc biet tai Timg Trdng (miia kho: 0,53; miia mua: 2,92).
Kiln nghi
DOi vdi boat dpng nudi cd biln bdng ling be tai Cdt Ba cdn tudn thu edc ky thudt nuoi vdrj tiing loai ddi tugng: chpn con gidng, mat dg nudi, thiic an va chi d9 cho an, cac bien phap phdng b?nh dich ..., bd tri cdc d ldng va eum be nudi hgp ly dl tang cudng kha nang liru thdng nudc;
Tilp tuc thi hdnh viec di ddi va sap xep I sd diem nuoi trong thiiy sdn khong hgp ly theo Quylt dinh 1572/Qp-UBND ngay 27/9/2010 ve Quy hoach chi tiet phat frien nuoi trong hai sdn fren viing bien Hai Phong den nam 2015, dinh hudng den nam 2020.
TAI LIEU THAM KHAO
1. Canadian Council of Ministers of the Environment, 2001. Canadian water quality guidelines for the protection of aquatic life:
CCME Water Quality Index 1.0, User's Manual, in: Canadian environmental quality guidelines (1999), Canadian Council of Ministers of Environment, Winnipeg.
2. Tran Quang Thu, Le Tuan Son, Nguyen Tien Long, Doan Thu Ha, Tran Van Luan, 2013. Assessment of Water Quality at Fish Cages in the North of Vietnam. J. Sci. &
Devel., 2013, Vol. 11, No. 7: 996-1004.
3. Trdn Quang Thu, Nguyen Tiin Long, Le Tudn San, 2013. Chat lugng moi tradng nude khu vuc nuoi ca bien bang long be tai Cat Ba - Hai Phdng, Tap chi Nong nghiep va Phdt triln Nong thon, thdng 12/2013.
Tr. 254 - 259.
4. Nguyen Due Binh, Nguyen Quang Chuang, Phgm Thi Thanh vd Vo Van Binh, 2011. Bao cdo nhi?m vu "Quan trdc, canh bdo raoi trudng vd dich benh thiiy san nuoi frdng thiiy san tai mot so tinh mien Bac Viet Nam, nam 2011 ", Bdc Ninh. Tray cap ngdy 20/4/2014 tai:
htips://sites.google.com/site/raoitmongthuy san/moi-tmong-thuy-san/nghien-cuu-danh- gia/moi -tmong-va-benh-ca-bien 5. Nguyen Van Nguyen. Le Thanh Tung, Dao
Duy Thu, Luu Xuan Hoa, Nguyen Cong Thanh, Nguyen Hoang Minh, Yasuwo Fukuyo, 2013. Recent HAB events in Ha
6 nhiem moi trudng khu nuoi ca bi6n . . . Long bay (Vietnam): Increase in frequency, 6. Cao Thi Thu Trang, Nguyin Thi Phuang harmfiil effects associated witii increased Hoa, 2009. Ddnh gia sire tdi mdi tradng eutiophication. Proceedings 15* ICHA, vimg nudc ven biln ddo Cat Ba phuc vu accepted manuscript. cho phat tiiln bin vung. Tap chi Khoa hpc va Cdng nghe biln, Phu tiirang 1 (2009), t r .
154-168.
EIWIRONIVIENTAL POLLUTION AT TYPICAL IMARINE FISH CAGE CULTURE AREAS: CASE STUDY AT CAT BA - HAI PHONG
Le Tuan S o n \ Tran Quang Thu\ Nguyen Cong Thanh\
Pham Hoang Giang\ Tran Van Than!?
'Research Institute for Marine Fisheries-MARD
^Ha Noi University of Science-VNU
ABSTRACT: In recent years, the aquaculture activity of marine fish cage at CatBa island has been affected by water pollution In wet season, the average concentration of DO was lower than Vietnamese standard (>5.0 mg/l) which happened at Ben Beo (4 67 mg/l), Tung Trang (4 71 mg/l), Vung Gia (4.89 mg/l) Moreover, the average concentration ofN-NH/ was 1.05 times higher than the Vietnamese environmental standards. Water quality index - CCME - WQI was between 46 and 61, showed that there were polluted signs of water quality in rainy season causing disadvantages to manne aquaculture. The reasons were high concentrations of organic matters and nutrient in water; waste from marine aquaculture, tourism services and partly polluted sources from mainland.
Keywords: Cat Ba, CCME - WQI, marine aquaculture, pollution