Tuyin Tap Nghien Ciru Biin, 2010, XVII: 53-63 CHAT LUONG MOI TRl/OTVG NlTOG DAM NHA PHU - VINH BINH CANG VA MOI LIEN QUAN vOl CAC HOAT D0NG KINH TE Pham Huu Tam, Le Thi Vinh, Duong Trong
Trang 1Tuyin Tap Nghien Ciru Biin, 2010, XVII: 53-63
CHAT LUONG MOI TRl/OTVG NlTOG DAM NHA PHU - VINH BINH CANG
VA MOI LIEN QUAN vOl CAC HOAT D0NG KINH TE
Pham Huu Tam, Le Thi Vinh, Duong Trong Kiem, Nguyen Hong Thu, Pham Hong Ngoc
Vien Hdi duong hoc
Tom tat Ket qua nghien cuu cho thay, vai thong so trong moi truong nuoc tai khu
vuc dam Nha Phu (chu yeu d vung dinh dam) co gia tri nam ngoai gia tri gidi han (GTGH) ciia tieu chuan nude nuoi trong thiiy san Viet Nam, 5943: 1995
va ciia cac nude Asean, the hien rat ro vao miia mua: oxy hoa tan (4,75mg/l) vat lo lirng (83,3mg/l), nitrate (71 u.g/1), ammonia (73ug/l), ham luong hydrocarbon trong nude d tat ca cac tram khao sat deu vuot GTGH Chat luong moi trudng khu vuc vinh Binh Cang it 6 nhiem hon so vdi khu vuc dam Nha Phu, hau het cac thong so trong moi trudng nude d vinh Binh Cang deu nam trong GTGH, chi co ham luong hydrocarbon vuot GTGH (he so 6 nhiem la 2,14 vao miia kho va 1,64 vao miia mua)
Ket qua phan tich cac mau nude thai cho thay nhieu thong so moi trudng cd gia tri nam ngoai GTGH duoc quy dinh trong TCVN 6772: 2000 (muc 1): ham luong ciia BOD5 (Tan Thiiy 1: 69,7mg/l; Tan Thiiy 2: 38,2mg/l), N03-N (Tan Thiiy 3: 57.893ug), TSS (Tan Thiiy 2: 2.970,8mg/l) Dac biet ham luong coliform vuot GTGH nhieu lan (he sd d nhiem: 24 x 103 - 75 x 106)
ENVIRONMENTAL QUALITY OF NHA PHU LAGOON - BINH CANG BAY
WITH RELATION TO THE ECONOMIC ACTIVITIES
Pham Huu Tam Le Thi Vinh Duong Trong Kiem, Nguyen Hong Thu, Pham Hong Ngoc
Institute of Oceanography
Abstract The studied results show that concentration of environmental parameters in
Nha Phu lagoon (such as dissolved oxygen, total suspended solids, nitrate, ammonia) exceeds the limit values, expressed very clearly in the rainy season, hydrocarbon content in water at all stations is over the limit values Environmental quality in Binh Cang bay is better than Nha Phu lagoon, most
of the parameters of the water environment in Binh Cang bay are in the limit values, only the hydrocarbon content exceeds the limit values
The analysis of wastewater samples shows that the concentration of environmental parameters such as BOD5, NO3-N, TSS exceeds the limit values Specially, concentration of coliform exceeds the limit values several times (with pollution coefficients: 24 x 103 - 75 x 105)
I GIOI THIEU
Dam Nha Phu - vinh Binh Cang la
vinh bien nua kin ven bd Mien Trung, nam
each thanh phd Nha Trang 20km ve phia
bac cd vi tri dia ly tir 109°09' - 109°17'
kinh do ddng va 12°18'-12°27' vT do bac
Viing dinh dam Nha Phu cd mot sd song sudi dd vao, tren luu vuc cac song nay hoat ddng san xuat ndng nghiep va nuoi trong thiiy san dien ra kha sdi ddng Tir nam
1995 den nam 2007 gia tri san xuat ndng nghiep toan huyen lien tuc tang: Nam 1995 dat khoang 255,4 ty ddng, nam 2000 dat
53
Trang 2275 ty ddng va den nam 2006 tang nhanh
den 346 ty dong San luong thuy san nuoi
trdng toan huyen trong nam 2007 la 4.618
tan, bang 115,39% so vdi cung ky nam
2006, nang suat torn nuoi binh quan dat
1,09 tin/ha, san lugng torn toan huyen nam
2007 la 2.000 tin, bang 116,41% va tang
282 tin so vdi cirng ky nam 2006 (Phong
Th6ng ke huyen Ninh Hoa, 2007) Nhirng
hoat dong kinh te dien ra trong khu vuc
nghien cuu co kha nang tao ra nhung nguy
co ve suy thoai chat luong mdi trudng, din
den suy giam nguon loi thiiy san, de dga
true tiep cudc song ciia cu din song quanh
dam ddng thoi giy d nhiem cho dim Nha
Phu - vinh Binh Cang
Trudc diy, nhdm de tai chiing tdi
ciing nhu mot sd tic gii da quan tim
nghien ciiu mdi trudng khu vuc niy, nhu
Bui Hong Long (1996), Le Thi Vinh va cs
(1996), Pham Van Thom va cs (1998,
2005), Lai Van Hiing (2004) thu dugc
mgt sd din lieu tham khao tdt Tuy nhien,
sau mgt thoi gian tuong ddi dai, mdi
trudng d diy da cd nhieu bien ddi do cac
hoat ddng kinh te va din sinh phit trien,
nen dat vin de nghien ciiu lai mot each
toan dien chit lugng mdi trudng dim Nha
Phu, vinh Binh Cang trong mdi lien quan
vdi cic hoat ddng kinh te la mot vide lam
cin thiet rit cd y nghia khoa hgc va thuc
tien lam co sd khoa hgc phuc vu quan ly,
bio ve mdi trudng, phat trien kinh te ben
vung
II PHlTONG PHAP
1 Thu mau:
+Thuc hien 2 dot khao sat vao thing 5/2008 (mua khd) va thing 10/2008 (miia mua) dd thu mau nude (Hinh 1) Mau dugc thu vao luc trieu thap, tdng cdng cd tat ca
40 miu nude da dugc thu
Cdc chi tieu phan tich bao gdm: V|t
lo lirng, do muoi, DO, BOD5, cac mudi dinh duong (NH3,4-N, N02-N, N03-N, PO4-P, Si03-Si), chit huu co (N huu co, P huu co), coliform, hydrocarbon
+Thu mau nude ao nuoi torn va nude thii khu din cu (Hinh 1) Cd 16 mau nude
ao nuoi torn va 6 miu nude thii da dugc thu va phan tich
Cic chi tieu phan tich: pH, vat lo lirng, DO, BOD5, mudi dinh dudng (NH3,4
-N, NO2 N, N03-N, P04-P, Si03-Si), N huu
co, P huu co), coliform
2 Phuong phap phan tich:
Cic miu nude duoc xir ly, bio quan
va phin tich theo cic phuong phap tieu chuan hien hanh (APHA, 2005)
He sd d nhiem duoc tinh theo cdng thirc:
He sd d nhiem = (Gia tri thuc) : (gia tri gidi han)
Cac sd lieu lien quan den hoat ddng kinh te-xa hdi cua vung nghien cuu dugc thu thap tai phong Ndng nghiep huyen Ninh Hda
Xu dung phin mem thdng dung Microsoft Excel de ve cic do thj
Trang 3Hinh 1 Vi tri cac tram thu mau tai khu vuc nghien ciru Fig 1 Location of sampling stations
Chu thich: A: khu vuc ao nuoi xa Ninh Phii, B:
Ninh Loc, D: khu vuc ao nuoi xa Ninh Ich
III KET QUA
1 Hien trang moi truong khu vuc dam
Nha Phu - vjnh Binh Cang:
Cac so lieu thu duoc trong 2 chuyen
khao sat miia kho (thang 5/2008) va miia
mua (thang 10/2008) duoc trinh bay d hinh
2 3 Tu cac dan lieu phan tich tren co the
thay ham luong cac yeu to moi trudng cd
su bien ddi theo khong gian va thai gian rat
ro ret Tai khu vuc dam Nha Phu, dac biet
la viing dinh dam (gdm cac tram 1, 2, 3)
nai tiep giap vdi cac con song, vao mua
mua gia tri do mudi, ham luong dxy hda
tan thudng thap han so vdi miia khd (tuong
ling vdi cac gia tri trung binh la: 21%o so
vdi 25%o va 5.28mg/l so vdi 6.38mg/l), con
ham luong vat la limg cac mudi dinh
dudng nhu: N02-N, N03-N, NH3.4-N,
SiOvSi P huu ca ldn han so vdi miia khd
(cac gia tri trung binh tuong ung la:
31.68mg/l so vdi 70,68mg/l; 6,13ug/l so
vdi l,52ug/l; 59,83ug/l so vdi 43,83ug/l;
58,30ug/l so vdi 52,00ug/l: 1.504ug/l so
vdi 934ug/l va 90,78ug/l so vdi 34.77ug/l)
khu vuc ao nuoi xa Ninh Ha, C: khu vuc ao nuoi xa
Mot vai thdng sd mdi trudng nude tai khu vuc nay vuot gia tri gidi han (GTGH), ham luong dxy hda tan thap hon GTGH duoc ghi nhan tai cac tram viing dinh dam (4,75mg/l, tram 2), ham luong ciia vat la limg (83,3mg/l, tram 2), NO3-N (71,1 ug/1, tram 1 va 3), ammonia (73pg/l, tram 1), hydrocarbon (d tat ca cac tram khao sat) cao hon GTGH Tai vinh Binh Cang, ham luong BOD5 vao miia mua luon thap hon
so vdi miia khd d ca 2 tang nude (tang mat 0,64mg/l so vdi l,09mg/l va tang day 0,84mg/l so vdi l,45mg/l) Ham luong ciia vat la limg, cac mudi dinh dudng (NO2-N,
NH3 4-N, PO4-P, Si03-Si) vao miia mua cd pham vi dao ddng ldn va gia tri cao hon so vdi miia khd (cac gia tri trung binh tuong img la: 47,48mg/l so vdi 25,18mg/l; l,94pg/l so vdi 0,28pg/l; 2pg/l so vdi lug/1: 5,72 ug/1 so vdi 3,10 ug/1 va461 ug/1
so vdi 333ug/l) Tom lai, tai khu vuc dim Nha Phu ham luong ciia cac thdng sd mdi trudng nude (dxy hda tan, vat la limg NO3-N, ammonia, hydrocarbon) deu nam ngoai GTGH the hien rat ro vao miia mua
55
Trang 4Trong luc do, d vuc nude vinh Binh Cang
khi so sanh vdi cac tieu chuan chat lugng
nude hien hanh thi con tuong doi tot, phan
ldn cac thong so moi truong nude khao sat
DO muoi
deu nam trong GTGH, ngoai trir ham lugng ciia hydrocarbon vuot qua GTGH (he s6 6 nhiem la 2.14 vao miia kho va 1,64 vao miia mua)
4
3.5
3
2 5
2
0 5
0
mg/1 Vat lo lung
M9/I
n o
N024M
3 4 5
van NO 3 -N
2 3 4 5
NH34-N
3000
2500
2000
1500
1000
500
0
van Si03-Si
9m
Chii thich:B (10/08) 0(5/08) Hinh 2 Bien thien ham lugng ciia mot so thong so moi truong (tang mat) tai khu vuc dam Nha Phu Fig 2 The concentration variation of environmental parameters (surface) in Nha Phu lagoon
Trang 5ng/l P hOu cc (tang m$t) ug/1 Hydrocarbon (tang m$t)
700
-600 I I
i 11
n l J n l
2 3
• (5/08) I (10/08) 5 6 • (5/08)
1 Ting mit (5/08)
-ting mSt (10/08)
10 11
I Tang day (5/08) -Ting day (10/08)
] TJng mat (5/08) -Tang mat (10/08) I Tang day (5/08) -Ting day (10/08) ng/i N02-N
7 8 9
Ting mSt (5/08)
— Tang m|t (10/08)
I Tang day (5/08) -Tang day (10/08) ] Tang mat (5/08) -Tang mat (10/08) I Tang day (5/08) -Tang day (10/08)
Si03-Si
] T3ng mSt(5/08)
-Tang mat (10/08) I Tang day (5/08) -Tang day (10/08)
7 8 9
i 1 Tang mat (5/08) -•— Ting mat (10/08)
10 11 T r ? m
Ting day (5/08) Ting day (10/08) Hinh 3 Bien thien ham luong ciia mot so thong so moi truong tai khu vuc vinh Binh Cang Fig 3 The concentration variation of environmental parameters in Binh Cang bay
5"
Trang 62 Moi lien quan cua cac hoat dong kinh
te va dan sinh vdi chat luong moi truong
khu vuc nghien cuu
Cac hoat dong kinh te, dan sinh da va
dang dien ra xung quanh deu xa nude thai
true tiep vao vuc nude khu vuc nghien
cuu Tuy theo thanh phan khac nhau ciia
tung loai nude thai ma co nhung anh
hudng nhat dinh den chat luong nude ciia
thiiy vuc nghien ciiu
2.1 Dac diem cac nguon thai xung
quanh khu vuc dam Nha Phu - vjnh
Binh Cang:
Cac nguon nude thai chu yeu la:
nude thai tir cac hoat ddng dan sinh, nuoi
trong thiiy san va nguon nude dd ra tir cac
song sudi d viing dinh dam Nha Phu
2.1.1 Nguon thai tic hoat dong khu dan cu:
Xung quanh khu vuc nghien ciiu cd 4
xa bao gdm 10 thdn, cac xa Ninh Phu,
Ninh Ha cd mat dd dan cu thua that Con 2
xa Ninh Ich va Ninh Loc cd mat do tuong
ddi cao, trong do ndi bat nhat la 2 thdn Tan
Thiiy (Ninh Loc), Tan Thanh (Ninh Ich)
vdi tdng sd dan khoang 8.026 nhan khau,
trong do cd khoang 20% cu dan d day tap
trung chii yeu viing gan mep nude ciia dam
vdi dieu kien ve sinh mdi trudng kern va
thai true tiep nude thai vao dam
Dua theo each tinh toan ciia To chirc
Y te The Gidi (World Health Organization)
vao nam 1993 ap dung cho nhieu quoc gia
dang phat trien khdi luong chat d nhiem
do dan cu 2 thdn Tan Thiiy va Tan Thanh
hang ngay dua vao mdi trudng (Bang 1) la
khong nhd
Sd lieu phan tich (Bang 2) cho thay
thanh phan nude thai cd chira ham luong
cao ciia cac chat va vuot xa GTGH dugc
quy djnh trong TCVN 6772: 2000 (miic 1):
gia tri ciia BODs d cac cdng phan ldn deu
vugt GTGH, d cdng Tan Thiiy 1 gia tri cua BOD5 la 69,7mg/l, cdng Tan Thiiy 2 gia tri ciia BOD5 la 38.2mg/l; mudi dinh duong NO3-N (57.893ug/1, cdng Tan Thuy 3), ham lugng TSS (2.970,8mg/l, cdng Tan Thiiy 2) va dac biet coliform vuot GTGH rat nhieu lan (vdi he sd d nhiem tir 24 x 10
- 75 x 106
lan)
2.1.2 Nguon thai tic cdc hoat ddng nudi trong thuy san (NTTS):
Xung quanh viing nghien ciru la nai tap trung nghe nudi torn dia kha phat trien cua cu dan 4 xa Ninh Phii, Ninh Ha, Ninh Ldc va Ninh Ich Dien tich va san luong nudi trong dugc the hien trong bang 3
Sd lieu thdng ke thanh phan nude cac
ao nudi thu dugc tai cac khu vuc nudi torn dia dugc trinh bay d bang 4, 5 Nhung dan lieu d cac bang nay cho thay, do lugng thuc an du thira trong qua trinh nudi tha torn nen nude trong cac ao nudi cd ham lugng vat la limg, ham lugng nitrate, phosphate, P hifu ca, N hifu ca thudng cao hon so vdi nude trong khu vuc dam (cac gia tri trung binh tuong img la : 45,2mg/l; 50,1 ug/1; 4,26ug/l; 44,6 Ug/1 va 586ug/l), the hien ro nhat d nhirng ao nudi torn the chan trang, nhung ao nudi d vao thai diem sap thu hoach
2.1.3 Vat chat tie song sudi 0 vung dinh dam Nha Phu:
Ket qua phan tich thanh phan nude tai dap Ben Bap (thudc song Dinh) va cau Cay Gang (hop luu ciia 2 con song Nga Hau va song Nga Da) dugc trinh bay d bang 6 Cac dan lieu cho thay tat ca cac gia trj va ham lugng cua cac yeu to nhu: mudi dinh dudng, chat hiru ca, kim loai nang, hydrocarbon deu ldn hon rat nhidu so vdi nude trong dam Nha Phu - vjnh Binh Cang
Trang 7Bang 1 Ucrc tinh lugng nuac thai do dan cir 2 thon Tan Thiiy, Tan Thanh do vao vung nghien ciiu
Table 1 Estimated amount of wastewater from residential areas flowing into the study area
Chat 6 nhiem Gia trj trung binh khoi lur/ng Tai luong chat 6 nhiem
Bang 2 Ham lugng cac thong so moi truong ciia nuac thai tai mot so cong thai
tu khu dan cu Tan Thiiy Table 2 The concentration of environmental parameters of wastewater in
residential area (Tan Thiiy) Thang 5 - 2008 Thang 7 - 2008 Thong
Thong
so Thuy 1 Thuy 2 Thuy 3 Thuy 1 Thiiy 2 Thuy 3 (*)
TSS mg/l 123,4 119,2 107,8 2714,7 2.970,8 3.413,3 50
BOD5 mg/l 20,7 38,2 31.1 69,7 29,9 11,4 30
N02-N ug/1 60,3 90,3 42,0 47,2 26,5 342,0
-NO3-N ug/1 4024,0 4.851,0 3.111,0 901 898,0 57.893,0 30.000
NH,.4-N ug/1 680,0 780,0 248.0 164 104,0 236,0
-P04-P Ug/1 2.984,0 764,0 2.840,0 6912 3.696,0 1.091,0 6.000
N huu co ug/i 9.240,0 9.525,0 8.590,0 57790 63.910 146.120,0
-Phuuco ug/1 3.771,0 3.750,0 3.560,0 27520 29.050 50.480,0
-Coliform MPN/lOOml 61xl07 24x10" 75x10" - - - 1.000
(*): TCVN 6772:2000, (muc 1): dung cho nuoc thai sinh hoat ct khu vuc cdng cong
Bang 3 Dien tich va san lugng nuoi trong thiiy san ciia cac xa tai khu vuc nghien ciiu nam 2007 Table 3 Area and aquaculture production of the communes in the study area in 2007
STT Ten xa Dien tich ao nuoi (ha) San luffing (tan)
(Theo phong Nong nghiep huyen Ninh Hoa, 2007)
59
Trang 8Bang 4 Ham lirgng cac thong sd moi truong cua nude ao nuoi torn (thang 5 - 2008) Table 4 The concentration of environmental parameters of water in shrimp pond (5 - 2008)
a Cac thong so ca ban va muoi dinh duong
Vj tri Loai torn Thoi gian Mat do TSS BOD, NOz-N N03-N
ao nudi nudi tha(ngay) (con/m2) (mg/l) (mg/l) (Hg/D (ug/1)
Ninh Loc 1 Chan trang 30 100 208 7,4 3,9 97
Ninh Ich 2 Chan trang 60 110 250 14.9 16,1 97
b Cac mudi dinh dudng va coliform
Vi tri
ao nuoi tha (ngay) Thoi gian NH3.4-N (Ug/1)
PO 4 -P
(ug/D
Si03-Si (ug/D (ug/D N he (Ug/1) P he (MPN/lOOml) Coliform
Ninh Phii 2 105 268 7,5 427 1.525 255,2 2.400
Bang 5 Ham luong cac thdng so mdi trudng ciia nude ao nudi torn (thang 7 - 2008) Table 5 The concentration of environmental parameters of water in shrimp pond (7 - 2008)
a Cac thdng sd ca ban va mudi dinh duong
Vj tri Loai torn Thoi gian Mat do TSS BOD, N02-N NO3-N
ao nuoi nuoi tha (ngay) (con/m2) (mg/l) mg/l) (Ug/D (ug/1)
Ninh Phu 1 Chan trang 45 90 264,7 21,0 25,7 228 Ninh Phu 2 Chan trang 60 100 282,7 20,2 21,6 217 Ninh Loc 1 Chan trang 80 - 222,0 19,5 15,5 138
Ninh Ich 1 Chan trang 45 100 336,0 19,5 33,5 122 Ninh Ich 2 Chan trang - 100 485,0 19,6 20,2 154
b Cac mudi dinh duong
Vi tri Thoi gian NH3.4-N PO 4 -P SiOj-Si N he P he
ao nuoi tha (ngay) (ug/1) (ug/1) (ug/1) (ng/i) (ug/D
Trang 9Bang 6 Ham lugng cua cac thong s6 moi truong tai dap Ben Bap (song Dinh) va cau Cay Gang Table 6 The concentration of the environmental parameters in water of Ben Bap dam
and Cay Gang bridge Yeu to Dun vi Dap Ben Bap (song Dinh) Cau Cay Gang Yeu to Dun vi 5/2008 10/2008 5/2008 10/2008
2.2 Kha nang gay anh huong cua cac
nguon thai doi voi chat lugng moi
truong khu vuc nghien cuu:
Nhirng dan lieu trinh bay d cac bang
1, 2, 3, 4, 5, 6 cho thay cac nguon thai (sinh
hoat khu dan cu, nuoi trong thiiy san, vat
chat tir song suoi, ) do vao thiiy vuc
nghien ciru deu co dac diem chung la chira
nhieu chat dinh dudng, huu ca, dau ma,
coliform Ngoai ra, cac hoat dong nuoi torn
dia da do vao vuc nude nghien cuu mot
lugng bun rat ldn, bun ao nuoi torn chira
mot lugng ldn chat huu ca khong chi a tang
mat ma con den ldp biin 30cm do tich luy
trong suot qua trinh nuoi Lugng biin day
nao vet tir cac ao nuoi torn co the dat den
20m3/1.000m2 (Lai Van Hirng, 2004) Mat
khac tir lugng biin chira nhieu vat chat la
limg, giau chat huu ca nay trong tinh trang
yem khi thi thudng hinh thanh nhieu khi
doc hai nhu ammonia, nitrite va dac biet la
cac khi chira luu huynh ciing dugc phong
thich trd lai moi truong nude, gay nen
Bang 7 Luang vat chat do song Dinh do ra thiiy vuc nghien cuu trong miia mua (10/1997) Table 7 The amount of material by Dinh river flowing into study area in rainy season (10/1997)
nhung tac hai cho ddi song ciia sinh vat Viing dinh dam Nha Phu la nai nhan true tiep nguon vat chat tir cac song suoi do vao va lugng vat chat nay gia tang rat ldn vao miia mua lu Lugng vat chat do song Dinh do vao thiiy vuc nghien ciiu trong miia mua do Pham Van Thom va cs (1998) udc tinh dugc mo ta d bang 7 va thanh phan nude tai dap Ben Bap vao miia mua nam 1997 va nam 2008 dugc mo ta d bang 8 Cac dan lieu tir bang 7, 8 cho thay lugng vat chat tir song Dinh do vao dam Nha Phu trong miia mua nam 2008 ldn han
so vdi miia mua nam 1997 Khoi lugng vat chat tir cac song suoi con lai nam xung quanh dam, cho den nay van chua co nhirng nghien ciiu va thong ke chi tiet, tuy nhien qua so lieu phan tich d bang 6 tai tram cau Cay Gang (nai giao nhau ciia 2 con song Nga Hau va Nga Da) cho thay lugng vat chat do vao thiiy vuc tir he thong song suoi nay la dang ke
61
Trang 10Bang 8 Ham luong ciia cac thong so moi trudng nude tai dap Ben Bap (song Dinh)
trong cac nam 1997 va 2008 Table 8 The concentration of the environmental parameters in the water of
Ben Bap dam in 1997 and 2008
(*): Pham Van Tham va cs (1998)
IV THAO LUAN
Khu vuc nghien ciiu tiep nhan nguon
nuac ciia mot so song, suoi, trong do song
Dinh co luu luong Ion nhat, tren luu vuc
song Dinh la viing hoat dpng nong nghiep
ciia huyen Ninh Hoa Tiep dudi la vung
dan cu tap trung vdi nguon thai sinh hoat
do true tiep vao dam Nha Phu, xung quanh
khu vuc nay ngudi dan con phai chiu su 6
nhiem ciia miii hoi thoi boc len tir nude
thai sinh hoat va dac biet gay gat vao
nhirng ngay nang nong Hoat dpng nuoi
torn sii va torn the chan trang phat trien kha
soi noi cung la nguon 6 nhiem dang ke
Nhu vay lugng chat thai dang ke ma
nghe nuoi torn thai ra cong vdi luong nude
thai sinh hoat, lupng vat chat tir song suoi
(chira nhieu chat gay 6 nhiem nhu huu ca,
dau md, coliform) do vao thiiy vuc nghien
ciru ngay cang gia tang se gay nen nhung
tac dong tieu cue den thiiy vuc tiep nhan
(dac biet la viing dinh dam) Co the noi
rang, chinh nhirng nguon thai tren da lam
gia tang miic dinh dudng, chat huu co va
hydrocarbon tai vuc nude nghien ciiu, lam
anh hudng den chat lupng mdi trudng dam
Nha Phu - vinh Binh Cang
Tuy nhien, do dac thii ciia thiiy vuc
nghien ciiu dd la kha nang trao ddi nude
manh lam cho khdi nude trong dam luon
dupe thay ddi, nude dd ra tir cac song sudi
a viing dinh dam nhanh chong dupe dua ra
bien (mot lupng ldn chat thai ciing dupe thoat ra bien), con khdi nude bien ngugc lai di vao trong dam, qua trinh nay lam dieu hda khdi nude trong dam va tao nen ddng chay dac trung (Bui Hong Long, 1996) Nude trong dam chay hai chieu theo hudng tay bac - ddng nam, nhd ddng chay
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