NGHIEN CI/U TRAO DOI 6 N H I E M A R S E N T R O N G N l t f C M A T C A C S O N G R A C H C H I N H VUNG MAN VA VUNG LU DONG BANG SONG A LONG • • Le Vdn MiM Trudng Dai hoc Bac Lieu >r Viet Nam, 6 nhi[.]
NGHIEN CI/U - TRAO DOI N H I E M A R S E N TRONG N l t f C M A T CAC SONG RACH CHINH VUNG MAN VA VUNG LU DONG BANG SONG A LONG • • Le Vdn MiM Trudng Dai hoc Bac Lieu >r Viet Nam, nhiem kim loai nang dac biet la Arsen (As) dii va dang dtfdc cong ddng quan I I tiim Theo dieu tra cua UNICEF, d nhiem As chii yeu hoat ddng ciia ngtfdi ^ ^ ^ r ndng nghiep, cdng nghiep va sinh hoat Phan ldn cac ngudn deu thai trtfe tiep hay gian tiep ngoai mdi trtfdng ma khdng dtfdc xtf ly theo quy dinh, ttf cho thay kha nang xiim nhiem viio mdi trtfdng ttf nhien rat ldn Dac biet d cac viing ctfa song, ven bien la ndi tich tu cac chat d nhiem cd ngudn gdc ttf ndi dia Trong nhffng nam gan day, kim loai nang dtfdc nghien ctfu nhieu tram tich cffa sdng, vung ven bien va rffng ngiip man tai mdt sd'qud'c gia tren the'gidi (Bryan & Langslone, 1992; Tam & Wong, 1995; Zheng & Lin, 1996; Zheng el al., 1997; Saifullah et al., 2004; Defew et al., 2005; Balachandran et al., 2005; Rashida et at., 2005; Sabine el al, 2006) O Viet Nam, nghien ctfu As tap trung d viing dat phen va vung dd thi (Phuong et al., 1998; Hoa et al., 2004) Tuy nhien, chtfa cd nhieu nghien ctfu ve mtfc dd d nhiem As dieu kien sinh thai khac Do vay, de tai "O nhiem As ntfdc mat cac sdng rach chinh viing Id va man ddng bang sdng Cffu Long", dtfdc thtfe hien nham cung cap dff lieu ve d nhiem As la cd sd eho cac nghien ctfu tiep theo ve As d ciic viing sinh thai khac - NOI DUNG VA PHUONG PHAP NGHIEN CUU Ndi dung nghien ciiu - Thu mau ntfdc tai viing CANTHO Id vii man ciia viing DBSCL; - Xac dinh pH, LC, chat ran ld ltfng (SS) va ndng As mau ntfdc tai viing Id va man; VJNHLONG zinrsi - Danh gia stf khac biet As d viing Id va man theo khdng gian vii thdi gian thu mau Phan lich md'i ttfdng quan ciia As vdi pH EC vii SS PhUdng phap nghien ciiu llSlil * Dia diem thu mau - Mau ntfdc d vung Id dtfde • Dia diem thu mau thu tir ndi dia ngoai ctfa Hinh I: Stf dd thu mau tai vung man va IdtfDBSCL sdng tai eae dja diem nhtf sdng Nguon: TT Quan trac TN&MT Can Thtf 2008 TAP CHI KHOA HOC CAN THO 29 NGHIEN CUU - TRAO DPI Dai Ngai, ciia Tran De kenh Quan Lo tinh Soc Trang (ha nguon song Hau); ttf Rach Song -Vinh Kim, Rach Tiin Lap - Hiep My huyen Cau Ngang, song Co Chien xa Long Hda, huyen Chau Thanh thi xa Tra Vinh (ha nguon sdng Tien) - O vung man mau ntfdc dtfdc thu theo htfdng ttf ndi dia vung cira song ven bien nhu" song Hd Phong, cira Ganh Hao (giap vdi bien Ddng) vit sdng Ong Trang, cira song Ong Doe, sdng Bay Hap va khu vtfc Bai Boi (giap vdi bien Tay) * Phuang phap thu mdu Tai mdi dia diem, mau ntfdc dtfdc thu mau, mau phan tich As va mau phan tich SS Mdi mau dtfdc thu each khoang - km Mlu dtfdc thu each mat ntfdc tif 30 - 40 cm Mieng chai hifdng ve phia ddng mfdc chay tdi (tru'dc lay man sue rira chai bang ntfdc tai hien trtfdng lan) Mau dtfde trtf lanh d 4°C Nhffng mau phim tich As eho vao ml HNO, dam dac de co' dinh (Le Trinh, 1997) * Phuang phap phdn tich Mau dtfdc phan tich tai Khoa Mdi trtfdng & Tiii nguyen Thien nhien vit Phong thi nghiem Chuyen situ, trtfdng Dai hoc Can Thd Mau ntfdc dtfde phan tich theo phtfdng phap chuan (APHA, 1998) * Phuang phap xvt ly so lieu - Sff dung phan mem excel 2003 de ve thi - Sff dung phan mem SPSS 13.0 de xu" ly so' lieu Kiem dinh Duncan d mtfc y nghia 5% de danh giii sff khac biet ndng dd As theo vi tri thu mau Dung T-Test de so sanh stf khac biet As theo miia KET QUA VA THAO LUAN - Arson ntfdc mat viing man Vao miia khd As dao ddng khoang 24.47 - 78,41 ug.L Cao nha't dtfde xac dinh tai Bai Boi vdi trung binh 78.41 ± 3.08 pg.L ' Ndng As tha'p nha't d ctfa Bay Hap, vdi gia tri trung binh 15,43 ± 6,84 pg.L ' Ndng dd As ntfdc tai Bai Bdi 1, va sdng Ong Trang cao gap de'n lan Khac biet cd y nghia thdng ke so vdi As ntfdc mat tai sdng Ong Ddc, ctfa Bay Hap, song Hd Phong va ctfa Ganh Hao ACM ABB_1 ABB_2 mnnrj Mua kho ABH AOTR Vung intin AHP AGH QCVN IO:2OD8/BTNMT Hinh 2: Ndng As (pg.L ) ntfde tai cac diem thu mau d vung man vao miia khd Ghi chu: ACM: sdng Ong Ddc ABB_1;ABB_2: Bai Boi ABU: eita Bay I Idp AOTR: sdng Ong Trang AHP: song Ho Phdng AGH: ciia Ganh Hao 30 TAP CHI KHOA HOC CAN THO Theo White & Driscoll (1987) (trich WHO, 2001) nirdc mat, vat chat hull cd cd vai trd quan trong viec hap phu As, dac biet d pH > 6,5 Thirc te khao sat cho thay tat Bai Boi va cira sdng Ong Trang cd ham ltfdng vat chat ld lung eao, pH ldn hdn Day la cac yen to gdp phan quan vao stf nhiem As nirdc mat tai hai dia diem tren Mat khac As ntfdc d khu vtfc Bai Boi va sdng Ong Trang cao Nguyen nhan viing ctfa sdng ven bien la noi tiep nhan va bdi lang cha't d nhiem ttf cac sdng rach ndi dia, chiu anh htfdng ttf hoat ddng thi, nudi trdng thuy san va phtfdng tien giao thdng thiiy (Sanders, 1980 trich Gomez-Caminero et ai, 2001; Chi Cue Mdi trtfdng Tay Nam bd 2009) Ke't qua dtfdc Irinh bay d hinh cho tha'y, ndng As tang dan ttf ndi dia de'n viing ctfa sdng ven bien dao ddng khoang ttf 15.43 - 78,41ug.L Ke't qua niiy chu'ng td, ctia sdng la ndi lang dong cac vat lieu tram tich ttf dat lien ra, hoac ddng chay ttf sdng vao bien hay thiiy trieu ttf nhffng ndi khac dtfa de'n Ke't qua phan tich cho tha'y, nhffng diem thu mim phia bien Tay (Biii Boi_l, Biii Boi_2, va sdng Ong Trang) cd ndng As cao hdn, ed y nghia tho'ng ke so vdi nhffng diem thu thudc trieu bien Ddng (sdng Ho Phong, ctfa Ganh Hao) Dieu niiy eho tha'y cd the stf phdng thich As tram tich vao ntfdc vi nhffng khu rtfng ngap man rat giau sulphide vii vat cha't hffu cd Day ciing chinh la ndi lang dong va ltfu giff chat d nhiem cd ngudn go'c ttf dat lien, nhai lii kim loai nang (Zheng et al., 1997; Defew et al., 2005) Theo nghien ctfu ctia WHO (2001) ndng dd As eho viing bien thtfdng lit - pg.L va ndng dp As d cac song vii hd thtfdng tha'p hdn 10 pg.L ' Nhin chung, ndng dp As ntfdc mat d viing khao sal kha eao, vtfdt ngtfdng ndng dp As cd ntfdc bien va sdng hd Theo ke't qua ctia de tai, ndng dp As dao ddng khoang 4,14 - 78,41pg.L ', vtfdt gidi han cho phep ctia Bp Tai nguyen Mdi trtfdng ve cha't ltfdng ntfdc ven bd, chie'm ti le 89/r tdng so' mau (gidi han cho phep theo QCVN 1():20()8/BTNMT la 10 pg.L ') Nong dd As ntfdc mat eao hdn so vdi ke't qua nghien ctfu ctia Sd Thiiy san Ca Mau va etv (2005) dao ddng khoang - 20 pg.L '; vii Nguyen Van Tho (2007) dao ddng 0,4 - 23.3 pg.L ' Ttf nhffng nghien ctfu vtfa mdi de cap, eho tha'y ndng dp As ntfdc cd xu htfdng gia tang nam gan day (2005 - 2010) va ndng dp irung binh vtfdt quy chuan cho phep dd'i vdi ntfdc ven bd khoang lan Ke't qua phan tich thdng ke, eho tha'y ndng dp As ntfdc mat viing nghien ctfu vao miia khd va miia mtfa khdng khac biet vdi giii tri trung binh Vao mua khd la 25,60 + 10,77 pg.L va miia mtfa 17,49 ± 15,80 pg.L 1 r 1 Bang I: Trung binh ndng As (pg.L ) ntfdc mat d vung man mua khd va mua mtfa Quy chuan Mua Trung binh Gia trj sai khac (P) QCVN 10:2008 (pg.L ) Miia khd Miia mtfa 25,60 + 10,77 17,49 + 15,80 a 0,41 10 a As ntfdc mat viing man cd md'i ttfdng quan thuan vdi pH, LC vit SS; As ttfdng quan chat vdi SS He so ttfdng quan lan ltfdt la r=0.56 r=0,55 va r= 0,84 Ke't qua ttfdng quan chi rang, pH, LC va SS tirng len thi ham ltfdng As cung tang theo vit ngtfdc lai Dae biet de tai cho thay, chat ran lit ltfng mdi trtfdng ntfdc cang cao thi kha nang ltfu giff As ciing tang Ke't qua eita de ttii phii hdp vdi nghien ctfu ctia Chunguo & Zihui (1988) (trich Biii Thi Mai Phung 2008) eho thiiy As cd cite vat chat ld ltfng va chat ran ld lffng la tac nhiin ha'p phu kim loai nang rat lot, dae biet la As TAP CHI KHOA HOC CAN THO 31 NGHIEN CUU - TRAO DOI - Arson ntfde mat vung lo" Nong As ntfdc giffa hai mua dao dong kha cao 0.30 - 15.39 pg.L ' Vao mua kho nong As cao nha't tai diem thu mau d rach Tan Lap vdi trung binh 15.39 ± 12,76 pg.L va ndng As tha'p nha't d cffa Tran De vdi trung binh 0,30 ± 0,4.3 pg.L \ d Rach Sdng_2 kenh Quan Ld vdi trung binh dffdi ngtfong phat hien Ke't qua tho'ng ke eho tha'y tai eae diem thu mau d kenh Quan Lo, song Dai Ngai cffa Tran De Rach Sdng_l va Rach Sdng_2 khac biet khdng ed y nghia thdng ke Nong As cao tim tha'y d sdng Co Chien rach Tan Lap va khac biet ed y nghia thdng ke so vdi eae diem thu mau tren cac sdng rach ndi dia (Bang 2) Being 2: Nong As (pg.L ) ntftfc tai eae diem thu mau 6" vung lo" mua khd va mffa Vi tri thu mdu Kenh Quan Ld Sdng Dai Ngai Cffa Tran De Rach Sdng_l Rach Sdng_2 Rach Tan Lap Sdng Co Chien Mua miia 2,30 1,32 1,18 0,93 1,07 3,37 0,97 Mua khd KPH 0,55 0,30 l,03 KPH 15,39 12,89b AB b B b B b B b B a A B QCVN 10.-2008/BTNMT 10 10 10 10 10 10 10 Thdng thtfdng, tai cac sdng rach nOi cd chtfa nhieu vat chat Id liing, ntfdc thai thi, ndng nghiep va ntfdc thai cdng nghiep la cac yeu to'ddng gdp quan vao stf d nhiem As ntfdc mat Ke't qua niiy phii hdp vdi khao sat thtfe tectfa de tai Cho tha'y, rach Tan Lap la ndi tap trung ddng dan ctf va la ndi tie'p nhan cac chat thai sinh hoat, ndng nghiep vit nudi trdng thiiy san thai trtfe tiep vao ngudn tiep nhiin vdi ham ltfdng vat chat ld ltfng cao Nong As ntfdc mat vao miia khd nam gidi han cho phep ctia Bo Tai nguyen Mdi trtfdng ve chat ltfdng ntfdc ven bd chiem ti le 57% vtfdt gidi han cho phep ciia quy chuan la 43% tdng so' m§u (gidi han cho phep theo QCVN 10:2008/BTNMT lii 10 pg.L ') Ket quit trinh bay bang cho tha'y ndng As cd xu htfdng giam vao miia mtfa va dao ddng khoang 0.93 - 3.37 pg.L ' Nong dd As eao d rach Tan Lap vdi trung binh 15,39 ± 2.16 pg.L vit tha'p nha't d Rach Sdng_l vdi gia tri trung binh 0,93 ± 0,72 pg.L" Ke't qua tho'ng ke cho tha'y ndng As ntfdc tai cac diem thu mau kenh Quan Ld, sdng Dai Ngai, ctfa Tran De, Rach Sdng_l Rach Sdng_2 va song Co Chien khac biet khdng cd y nghia tho'ng kc Nhtfng ciing khac biet ed y nghia thdng ke so vdi diem thu miiu tai rach Tan Lap Rieng diem thu mau tai kenh Quan Ld va rach Tan Lap khac biet khdng ed y nghia 1 Ci khu vtfc song Co Chien va rach Tan Lap ndng As dao ddng kha cao vao mua khd khoang ttf 12.89 - 15.39 pg.L vtfdt ngtfdng As cd ntfdc bien va sdng hd Ke't qua nghien ctfu ctia de tai phii hdp vdi nghien ctfu ctia Patel et al (2005); Farag et al ( 2007); Simone de Rosemond et al (2008) da tim thay ndng dd As d cac khu vtfc cffa sdng vao miia khd dao ddng khoang 15 - 53 pg.L ' Ket qua nghien ctfu ctia de lai eho tha'y ndng dd As ntfdc mat vao miia khd va mtfa dao ddng khoang 0.30 - 15.39 pg.L eao hdn so vdi ke't qua nghien ctfu ctia Mai Thanh Truye't (2003); Dao Manh Tien vii ctv (2005); Nguyen Viet Ky (2009) bao cao rang ndng As ntfdc mai dao ddng khoang ttf - 5,1 pg.L ' Dieu chtfng to tai vung Id stf d nhiem As ntfdc mat ed khoang bien ddng ldn vii cd xu htfdng gia tang theo thdi gian 1 32 TAP CHI KHOA HOC CAN THO NfiHIEN CUfU-TRAO DPI As ntfdc mat d viing Id khong co moi ttfdng quan vdi pH nhu'ng ttfdng quan thuan vdi EC (r = 0,6) Ket qua phan tich EC viing cho tha'y, EC tang ttf kenh rach de'n ctfa song va ham ltfdng As cung tang theo xu htfdng nhtf vay Ngoai ra, As cd ttfdng quan thuan vdi SS ntfdc vdi he so ttfdng quan kha cao r = 0,9 Ke't qua chu'ng td, As dtfdc hap phu cac dang vat chat It) lung va tai viing ciia sdng cao hdn sdng, rach ndi dia Khi ham ltfdng SS ciing cao thi kha nang ltfu giff As cang tang (Chunguo & Zihui 1988 trich Bui Thi Mai Phung, 2008) Ke't qua dtfdc trinh bay bang chi rang, ndng As ntfdc mat giffa mua khac biet cd y nghia thdng ke (P < 0,05) vdi gia tri trung binh vao miia khd la 8,5 + 7.79 pg.L vii mua mtfa lit 1,59 ± 1,19 pg.L ' Ndng dd As ntfdc giffa hai miia nam quy chuan cho phep ciia Bd Tai nguyen va Mdi trtfdng ve chat ltfdng ntfdc ven bd (gidi han cho phep theo QCVN l():2008/BTNMTla lOpg.L') Bang 3: Trung binh ndng dp As (pg.L" ) ntfdc mat viing ltf mua khd va mua mtfa 1 Mua Miia khd Mira mtfa Trung binh Gia tri sai khac (P) 8,5 l ± 7,79 1,59" ± 1,19 0,02 Quy chuan QCVN 10:2008 (ug.L ) a 10 Danh gia mtfc d