Đánh giá mức độ nhiễm bẩn và tích lũy các chất hữu cơ khó phân hủy (DDTs PCBs) trong môi trường trầm tích vịnh nha trang

^g Hgi nghi Khoa hgc vd Cong nghe biin loan quoc ldnj!ni_ DANH GIA MtrC DO NHIEM BAN VA TICH LUY CAC CHAT HUtJ CO KHO PHAN HUY (DDTs va PCBs) TRONG MOI TRU'ONG T R A M TICH VINH NHA TRANG Hoang Trung Du Vi^n Hai duang hpc 01 ciu B4, Nha Trang, Khanh Hoa Email: Mnineduiadnp.vnn.vn Tdm tit Dua vda kit qua ciia nghien cuu vdo ndm 2010 yd so sanh vcri cdc ket qud nhimg ndm gdn day (2007-2009) vi ham lucmg thuoc trir sau (TTS) Clo hiru ca thdy ring su dao dgng ciia ham lugn^ TTS hg Clo hiru ca trdm tich tgi vjnh Nha Trang la rdt lan vd lan han nhiiu so vai nhOng ndm gdn day Ket qua da cha thdy CO su tich IBy cao cdc chdt hihi ca dgc hgi moi trudng trdm tich cira song (tgi mat cdt phia song Cai): co diim Id C3 (tdng ham lugng DDTs Id 2ai09pg/kg) vd C6 (ting ham lugng DDTs la 15.206 pg/kg): vd mire nhiem bdn hdm luong nhom DDT trdm tich da vugt muc co kha nang dnh huong (PEL) tu din Idn (tieu chuin huong ddn ciia CCME EPC-98 EC).Su tich luy ciia cdc nhom TTS Idio phan hiiy dugc thi hien kha ro cgt trim vai ham lugng khd cao, vd xu thi vdn dang dip dien trgng viing mgc dii cdc nhom chdt tren dd bi nghiem cdm vd han che su dung dd nhieu ndm Trong do, PCBs trdm tich cha thdy hdu hit cdc vi tri khdo sdt deu CO hdm lugng rit thdp Dieu nay, chung to rang vinh Nha Trang hdu nhu it chiu dnh hudng hay nhiem bdn bai cdc nguon phat thdi ve PCBs so v&i mgt so vimg cua song vd ven bien ciia Viet Nam Chinh vi vay, cdn co nhiing canh bao doi vdi moi trudng bien vinh Nha Trang doi vdi cdc chdt hiru ca kho phdn huy nay, bai chung co khd ndng gdy mgt so nguy ca sinh thdi vd dnh huong doi vdi sic khoe cua ngudi ASESSMENT OF THE CONTAMINATION AND ACCUMULATION OF DDTs AND PCBs IN SEDIMENTARY ENVIRONMENT OF NHA TRANG BAY Based on the studied results in 2010, and the comparison with the recent studies (2007-2009), it showed that the contaminations by the DDTs compounds in sediment substrate of Nha Trang Bay is a huge and much larger than in recent years It also showed that the toxicants highly accumulated at the sediment bottom in river mouths (especially in Cai river transect) such as: at C3 station (YflDTs concentration was 20.109pg/kg) and C6 station (ZDDTs concentration was 15.206fig/kg) The DDT contaminations were higher than the level of limitation of the PEL about to times (evaluation Tiiu ba)i Sinh thdi, Mdi tnr&ng vd qudn ly Bien ^ = ^ based on the standard guidelines of CCME EPC-98 EC) The accumulation of DDTs compounds were clearly present in the sediment cores with the high concentration in top layers, and accumulation trends were continuously occurred in the areas, in spite of the organ-chlorine pesticides is strictly prohibited and reduced in many application for many years ago Meanwhile, the PCBs in sediment substrate in most of surveyed location were very low It was demonstrated that the Nha Trang Bay is not affected or contaminated by the sources emission of PCBs to compare with estuaries and other coastal areas of Vietnam Therefore, it should be a warning of these organic pollution for the marine environment of Nha Trang Bay, because of organic pollutants were caused ecological risks and harmful for human health I Modiu Cac chat hiru co dpc hai, khd phan huy (POPs) la tap hgp cac chit hda hoc tdn tai lau dai moi trudng, van chuyen va tich luy thdng qua chudi thuc an, tao nhimg nguy CO anh hudng xau den sure khoe ngudi, sinh v^t va moi trudng Do dd, cong udc Stockholm (ky 22/5/2001 tai Stocldiolm - Thuy Di§n) vl cac chit d nhiem huu ca kho phan hiiy d^t muc tieu bao v? siic khoe ngudi va mdi trudng trudc cac chat d nhiem POPs Theo k6t qua cua nhieu nghien cuu tren the gidi, cac chit huu co dpc hai khd phan huy cd thi tim thay ck nhiJng vung chua bao gid sir dung cac chit Su hien dien cua chat hiru co doc hai cd d rat nhieu noi cac qua trinh phat tan va van chuyen [24,1,19] Ddi vdi mdi trudng cac vung ven bien, vat chat lo lung sdng chuyin tai cac vung ven bd cdn luon gan kem theo nhieu chat nhiem ban va cd kha nang lang dong, tich luy vao mdi trudng tram tich, tir dd trd ngudn d nhilm v^ anh hudng den chat lugng moi trudng sdng [17,4,23] Dao dong chat nhilm ban tram tich (su phan bo theo khong gian - thdi gian) ph\i thugc nhieu vao ngudn d nhiem dua vao mdi trudng Tuy nhien, muc dO anh hudng ve dgc tinh se cdn phu thugc rat nhieu vao dang phan cua cac chat nhiem ban, nhat la cac phan huu co tdn tai mdi trudng tram tich (dac bi?t la tram tich d khu vuc cua sdng va vung ven bd) Nhieu nghien cuu ghi nhan rang, tai cac khu vuc cira sdng va vimg ven bd, cac chat dgc hai dugc tich luy nhieu tram tich nhu cac thudc trir sau, PCBs, PAHs, kim lo^i nang, dau thai , [2,22] Sir nhiem ban trim tich cd tac dgng mang tinh lau dai, cac sinh vat sdng moi trudng se dan thich nghi va cd kha nang tich luy vao co the va cd the gay nhung anh hudng trim trgng, tdn thuong he than kinh, rdi loan he thdng mien dich va ngi tiet, va nhQ-ng bieu hi?n benh ly khac [6,11,18,20,10] Nghiem trgng hon, su tich luy se gia tang theo bac cua chudi thirc an he sinh thai (dac biet nhu DDTs, PAHs, PCBs) [14] Cac nghien cuu gin day cdn cdn phat hien su tich luy kha cao ham lugng chat DDE va DDT ca sinh vat bidn va co the ngudi [9,12,14,5,3] Bao cao la ket qua nghien curu su phan bd va muc dg nhiem bSn cua cac chat huu co dgc hai va khd phan hiiy d mdi trudng viing biln ven bd vinh Nha Trang Hgi nghi Khoa hgc vd Cong nghe bien toan quoc lan thiV 50 Phmmg phap nghiSn cvn Zl Khao s4t thu mau Da tiln hanh mpt dot khao sat (thdng 8/2010) thu mlu trim tich bl mSt (trong I6p trim tich khoang 2cm a phia tren bl mat) vinh Nlia Trang, voi mat cat chinh to cua sdng Cai va song Tic (cira Be) dira ngoai vinh (hinh 1), voi 13 diemlayiniu(neng v i t n B l bo vj tri vu6ng gjp cac r4o dang ca, khdng tiep c|in dugc) Ngoii Iva chpn diem gan ciia song va giua vjnh dl tiln hdnh liy cot mSu tram tich 2.2 Phmmg phap thu tn&u vaph&n tich Phuong obia thu mlu.- Thu mlu trim tich bl mat (tu 0-2cm) bing cuoc trim tich (kich thudc 20cm x 15cm) (hinh 2a), mlu trim tich sau thu se dupe bao quin ^ va dua vS phong thi nghipm phan tich D6i vdi thu cot mlu trim tich, chung tdi su dung thiet bj 6ng phong trpng Ivtc (Diirc) Cpt trim tich thu dugc c6 dp dai tir Ichodng 35 din 40cm C0t HIIB sau thu dugc se dugc phan chia cSt Idp tir 0-5cm, 5-lOcm, 10-20cm rdi dem plito tich Phucmg phap plian tich: Mau trim tich dugc gin ve phdng Dia chat Bign ciia Vi^n Hai dirong hpc plian tich cac phin (%) ca hpc trim tich theo Qay pliam tam thai dilu tra UBKHKT Nha Nude ban iiinh 1983 Su d\mg phuong phap dot chay or nhipt dp cao vdi 16 nung Lindberg/BIue tji 500°C thcri gian gid dl phan tich tfing hiiu eg trim tich PhSn tich du lugng thulc tni sau hp chlo hiru eg va PCBs trim tich theo phucmg phap mo ta tai liSu US EPA, SW-846 (nam 2007) [21] Phin dung dich sau chift thu dugc sau cot dugc lam giau (the tich cuoi eiing Id 300|il) truoc chay phan tich tren hp thong may sic ky ghep khoi Shimadzu GC 17A vdi bp bom n^u t\r dpng Shimadzu AOC 20S, cpt mao din SLB-5MS va n6i ghep kh6i MS QP 5050A Phuong phip dinh lugng dugc dilng la phucmg phap npi chiian (Chat noi chuin sii dung cho nhom OCP li "Cp.p '-DDE: Ngi chuan sii dung cho nhom PCB la "CPCB US) Hinh 1: Vi tri thu mau trdm tich vinh Nha Trang, Khanh Hoa Tieu ban Sinh thdi, Moi tru&ng vd qudn ly Biin Xu Iv so lieu phan tich: So lieu, cac thj dugc thdng ke, phan tich va bieu diln tren phin mim Microsoft Excel Ngoai ra, phin mem SPSS dugc su dung dl so sanh su sai khac gifia cac vj tri thu mau (t-test) K^t qua va thao lu^n 2.1 Phdn b6 iidmlugfng TTS hiru cff cua tram tich vinh Nha Trang Tir ket qua phan tich cac phan thudc trir sau clo huu cd tram tich cho thay, t6ng du lugng DDT bien d^ng Idn giGa cac vi tri tai mat cit ciia sdng Cai va cua Be (thuoc sdng Tic) Tai mat cit sdng Cai, cac vi tri cd gia tri ham lugng nhom DDT cao tap trung phia ngoM cira sdng va lan can (C3, C5, C6) va giim din phia ngoai xa cura sdng (C4, C7) Dac biSt, tai vj tri C3 va C6 cd ham lugng tdng DDT kha Idn, gip nhieu lan so vdi vi tri khac (hinh 2a), Trong dd, t^i mat cat ciia Be, ham lugng nhom DDT nhd hon rat nhieu so vdi cac vi tri mat cat sdng Cai Gia tri tai vi tri B2 va B4 (cijra sdng va ISn c?Ln viing cua sdng) cd gia tri cao hon cac vi tri khac (hinh 2b) C^c phin TTS hg clo hiju CO khac cung khong phat hien thay tram tich d mat cat cua sdng Theo ket qua phan tich v§ phan (%) co hgc tram tich tai cac diem khao sat mat cat Xix song Cai ra, cho thay t^i cac vi tri C3 va C6 co dSc diem trim tich la bun va biin set (theo phan chia Wentworth Scale) Trong tai dilm C4 va C7 trim tich cd phan chu yeu la cat va manh vun san ho Dieu cho thay cd s\r tap trung cao nhom phan DDT d nhurng nai cd phan tram tich la biin va bun set khu vuc cua sdng Cai Trong dd, ddi vdi cac phan TTS ho Clo hiru co khac deu khong phat hien hoac dudi ngudng ^hat hien cua thiet bj phan tich Nhu chung ta dugc biet, nhung chat d nhiem deu cd the lang dgng va tich lUy xuong be mat tram tich day theo theo thdi gian Ddi vdi cac chat dgc hai va khd phan hiiy nhu DDT se tdn Xax lau dai tram tich va anh hudng xa tuong Iai Qua xem xet ket qua phan tich dugc cac Idp khac cua tram tich da cho thay cd sir khac dang ke (hinh 3), va cd s\r khac biet kha Idn giiia cac cot tram tich C3 (phia cua sdng Cai) ddi vdi B2 (ciia Be) Dieu chiing td, su nhiem ban tai khu vuc sdng Cai boi cac nhom DDTs Idn han rat nhieu so vdi tai cira Be [| Hinh 2a: Phdn bo cua DDT trin mgt cdt tic cua song Cdi ngoai vfnh Nha Trang Hinh 2b: Phdn bo cua DDT tren mat cdt tic cua Be ngoai vfnh Nha Trang 52 quk]injhuV_ HAi nalii Khoo hpc vd Cong nghe biin loan Hmh Phdn bdJia hdm lugng IDDTtheo tirng lap trdm tich theo cot trdm tich Ngoai so sanh gia trj trung binh t6ng hiiu co dit cua cac lap uim tich cua cac cpt khac cOng cho thiy co su khac bi?t thong ke giira cac cpt C3 va B2 (paired t-test, p=0.007); C3 va C6 (paired t-test, p=0.029 tram^ tich be mat, cp trim tich (0-5cm) co chiia ham luong nhom DDT cao han rat nhieu so voi cac lorptram tich phia dudi cpt Dilu mpt lin niJa khing djnh ring, lap tram tich tang mat van da va dang chju su nliilm bin cua nguIn thai c6 chua phin nhom DDT Tir kit qua ciia nghien cuu, va so sanh vdi cac kit qua nhimg nam gin day (tir 2007-2009) ve ham lucmg TTS clo huu CO, thiy ring su dao dpng cua vl hdm lugng TTS hp Clo hiru co tram tich tai vjnh Nha Trang la rit Idn nhieu Dilu cdn cho thiy cd su nhiem ban thudng xuyen cac phin nhom DDT trim tich vjnh Nha Trang, mac du cac chat da bj cim su dung, nhien vifc su dung cac loai TTS hp Clo hiiu ca la vin cdn (hoac khong cong khai), ddng thdi nhGng chit hiru co cdn ton tai kha lau moi trudng (dac biet la dat ndng nghiep) CJ day sir dung tieu chuin hudng din danh gia chat lugng tram tich va nude bien ven bd tam thdi duoc CCME (Canadian Council of Ministers of the Environment) xay dung vao nam 1998 [25] Ket hop vdi ket qua phan tich ve ham lugng TTS ho Clo huu co d tren, xem xet va danh gia sir nhiem ban chat hihi co dpc hai ddi vdi mdi trudng tram tich, da chi tai mat cat phia sdng Cai cd dilm la C3 va C6 cd tdng ham lugng nhom DDT tram tich da vugt muc cd kha nang anh hudng (PEL) tir din lin, va dilm C5 cd gia trj cham vdi muc PEL Trong tai mat cat phia cua Be thi hiu hit cac dilm diu chua co vuot miic PEL So sanh ham lugng TTS hp Clo huu co trim tich tai vjnh Nha Trang vdi cac vung vjnh khac tai Viet Nam nhu Ha Long (Quang Ninh), Tam Giang - Ciu Hai (Thira thien - Hul), dim Thj Nai (Binh Djnh), va ciia sdng Me Kong cho thiy gia trj phan tich dugc cua de tai cao han cac nghien ciiu d nhimg vimg ven bien khac [8,16,13,7]; va cac gia trj vl tdng ham lugng nhom DDT trim tich tai vjnh Nha Trang cd gia trj tuong duong so vdi tdng ham lugng nhom DDT tram tich cua sdng Sai Gdn (gin khu vuc cang Bason) [15] Tieu ban Sinh thai, Moi tnr&ng vd qudn ly Bien 2.2 Phdn bo ve hdm luffng nhiim ban PCBs tram tich vpih Nha Trang Vdi cac ket qua phan tich ve PCBs tram tich cho thiy hiu hk cac vi tri khao sat diu cd harn lugng rit thip, va dudi gidi han phat hien ciia thilt bi phan tich Dilu nay, chung td rang vjnh Nha Trang hau nhu it chiu anh hudng hay nhilm bin bdi cac ngudn phat thai ve PCBs so vdi mgt so vung cua sdng va ven bien ciia Viet Nam [3,13,15] Tuy nhien ket qua nghien ciiu bai bao gan nhu la sd lieu diu tien de cap tdi miic nhiem ban PCBs tron^ mdi trudng tram tich viuig biln Nha Trang Do v$y, viec tim hieu miic dg nhiem ban PCBs mdi trudng cin dugc tilp tuc (dac biet la khu vuc gan san xuit cong nghiep va dd thj) nham xem xet va danh gia ky hon dl tir dd cd thi lam r5 va canh bao nhung tac ddng true tiep cua nhilm bin PCBs den siic khde ngifdi [5] Ciing theo kit qua nghien ciru cua Minh va cgng su (2007) [13] va Nguyen Ngoc Vinh (2009) [15], cho thay ham lugng PCBs dit va trim tich lien quan kha chat toi cac khu virc cd nhieu ngudn chat thai cdng nghiep va dd thi Xu hudng biln ddi theo thdi gian se phy thugc nhilu vao cac tac dpng lam tang lugn^ tdn du cua chung dit Ma cac tac dgng lam tang lugng tdn du chu yeu la cd ngudn d nhilm bd sung vao dit tir viec ngudi tiep tuc sir dung PCB khu vuc Do dd, viec quan ly va xir ly phu hgp cac nguon nhilm PCB la rat can thiet de ngan ngira viec PCB xam nhap vao mdi trudng Ket luan Qua ket qua danh gia ve miic nhiem ban cac chit him co dgc hai, khd phan huy (d day t?p trung vao cac phan thudc trir sau hg Clo hiiu co va PCBs), chung tdi cd mgt sd nhan dinh sau; - Du lugng TTS hg Clo huu co tram tich vinh Nha Trang cd gia tri kha cao, dd nhom thudc trir sau DDT va cac phin phan ciia chiing nhu o,p'- DDD va o,p' DDE cac mlu tram tich tai cac vi tri mat cat phia sdng Cai cao hon (tir - lan) so vdi matcat phia sdng Tic (cira Be) Trong cac phin TTS hg Clo huu co khac va PCBs hau nhu rat nhd va nam dudi gidi ban phat hien - Tuy nhien, tir cac sd lieu phan tich cac Idp cua cdt tram tich cho thay dieu dang quan tam la ham lugng nhdm DDT d day van thudng xuyen hien dien, va co ham lugng kha cao so vdi cac tram tich d vi^g bien khac Tir day cho thay nhiem ban nhdm thudc trir sau DDT tram tich can dugc luu tam nhieu va cd nhiing canh bao d6i vdi mdi trudng bien vinh Nha Trang Bdi cac chat tren rat khd phan huy, va chiing cd the tich IGy mgt sd sinh vat, tir dd cd kha nang gay anh hudng ddi vdi siic khde ciia ngudi TAI LIEU THAIVI KHAO Breivik K., Alcock R., Li Y.F., Bailey R.E., Fiedlere H., Pacyna J.M (2004) Primary sources of selected POPs: regional and global scale emission inventories Environmental Pollution, 128,3-16 DeLaune, R D., R P Gambrell, J H Pardue, W H Patrick,Jr (1990) Fate of Petroleum Hydrocarbons and Toxic organics in Louisiana Coastal Environments Estuaries, Vol 13, Noi: 72-80 HQI nghi Khoa hgc vd Cdng nghj biin loan qu6c_lin ihi V Frignani, M , R Piazza , L.G Bellucci , N.H Cu , \ ^ ^ ^ ^ ° • ^•f^'^^f-J Moret, S Romano , A Gambaro (2007) Polychlonnated biphenyls in sediments Tam Giang-Cau Hai Lagoon, Centtal Viemam Chemosphere 67:1786-1793 Guzzella L., C Roscioli , L Vigand, M Saha, S.K Sarkar, A Bhattacharya (2005) Evaluation of the 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Residue pattem and dietary intake of persistent organochlorine compounds in foodstuff from Vietnam Arch Environ Contam Toxicol, 22: 367-374 lO.Lignell S., Aune M., Damerud P.O., Cnattingius S., Glynn A (2009) Persistent organochlorine and organobromine compounds in mother's milk from Sweden 19962006: Compound-specific temporal trends Environmental Research, 109, 760-767 11 Meekera J.D., Altshulb L., Hauser R (2007) Serum PCBs, p ; pO-DDE and HCB predict thyroid hormone levels in men Environmental Research, 104, 296-304 12 Minh, N.H., M Someya, T.B Minh, T Kunisue, M Wanatabe, S Tanabe, P.H Viet, B.C.Tuyen (2004) Persistent organochlorine residue in human breast milk from Hanoi and Hochiminh city, Vietoam: contamination, accumulation kenetics and risk assessment for infants Environ Pollut , 129: - 4 13.Minh, N.H., T.B Minh, H Iwata, N Kajiwara, T Kunisue, S Takahashi (2007) Persistent prganic polluants in sediments from Sai Gon - Dong Nai River Basin, Vietnam: level and temporal trends Arch Environ Contam Toxicol., 52 (2007a): 458465 14.Monirith, D Ueno, S Takahashi, H Nakata, A Sudaryanto, A Subramanian, S Kamppiah, A Ismail, M Muchtar, J Zheng, B J Richardson, M Prudente, N Due Hue, T S Tana, A V Tkalin, S Tanabe (2003) Asia-Pacific mussel watch: monitoring contamination of persistent organochlorine compounds in coastal waters of Asian countries Marine Pollution Bulletin, 46 (3): 281-300 Tiiu ban Sinh thdi Mdi tnr&ng vd qudn ly Bien ^ _ ^ _ ^ 15.Nguyen Ngoc Vinh, (2009) Occurrence of Persistent Toxic Substances in Soils, Sediments, Fishes and Human Breast Milk in Southern Vietnam POUR L'OBTENTION DU GRADE DE DOCTEUR ES SCIENCES ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, 2009 273 pages 16.Nguyen Diic Cu, Nguyen Manh Cudng (2005) nhilm thudc trir sau clo huu ca tram tich viing ven bd phia Bac Viet Nam Ky yeu Hgi thao toan qudc ve Bao ve mdi trudng va Ngudn Igi thuy san-Bg Thiiy san, 2005: 192-204 17 Nhan, D.D., Am, N,M, Hoi, Ch., Dieu, L.V, Carvalho, F.P, Villeneuve, J.P, Cattini, C (1998) Organchlorine pesticide and PCBs in Red river delta, North Viemam Mar Pollut Bull, 36: 742-749 18.Petersen M.S., Hailing J., Damkier P., Nielsen F., Grandjean P., Weihe P., Brosen K (2007) Polychlorinated biphenyl (PCB) induction of CYP3A4 enzyme activity in healthy Faroese adults Toxicology and Applied Pharmacology, 224, 202-206 19.Scheringer M., Salzmann M., Stroebe M., Wegmann F., Fenner K., Hungerbiihler K (2004) Long-range transport and global fractionation of POPs: insights from multimedia modeling studies Environmental Pollution, 128, 177-188 20 Todaka T., Hori T., Hirakawa H., Kajiwara J., Yasutake D., Onozuka D., lida T., Furue M (2009) Concentrations of polychlorinated biphenyls in blood of Yusho patients over 35 years after the incident Chemosphere, 74, 902-909 2i.US, EPA SW-846 (2007) Test Methods for Evaluating Solid Waste, ?hys\cd\IC]iQmicz\MQihods-hXX^://www.epa.gov/waste/}tazard/testmethods/sw846/on e/index.htm 22 Vos, J H., P J Van Den Brink, F P Van Den Ende, M A G Ooijevaar, A.J.P Oosthoek, J.F Postma, and W Admiraal 2002 Grovrth response of " benthic detritivore to organic matter composition in sediment 23.Wafo, E Luc Sarrazin, Catherine Diana , Frank Dhermain, Therese Schembri, Veronique Lagadec , Magali Pecchia , Pierre Rebouillon (2005) Accumulation and distribution of organochlorines (PCBs and DDTs) in various organs of Stenella coeruleoalba and a Tursiopstruncatus from Mediterranean littoral environment (France) 24.Wagrowski D.M., Kites R.A., (2000) Insights into the global distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans Environ Sci Technol 34, 29522958 25 CCME EPC -98E Tieu chuin hudng dan ve danh gia chat lugng mdi trudng tram tich bien cua Canada ddi vdi phan diudc trir sau Ngicoi doc nhan xet: TS Nguyin Th{ Viet Liin ... 2a: Phdn bo cua DDT trin mgt cdt tic cua song Cdi ngoai vfnh Nha Trang Hinh 2b: Phdn bo cua DDT tren mat cdt tic cua Be ngoai vfnh Nha Trang 52 quk]injhuV_ HAi nalii Khoo hpc vd Cong nghe biin loan... lugng TTS hp Clo hiru co tram tich tai vjnh Nha Trang la rit Idn nhieu Dilu cdn cho thiy cd su nhiem ban thudng xuyen cac phin nhom DDT trim tich vjnh Nha Trang, mac du cac chat da bj cim su dung,... vinh Nha Trang Hgi nghi Khoa hgc vd Cong nghe bien toan quoc lan thiV 50 Phmmg phap nghiSn cvn Zl Khao s4t thu mau Da tiln hanh mpt dot khao sat (thdng 8/2010) thu mlu trim tich bl mSt (trong