KHOA H O C , CONG NGHE - CHUYEN GIAO
OANH GIA SO BO HAIVILaONG CAC OONG Vj PHONG XA (U-238, TH-232, K-40, CS-137) TRONG K H O N G KHI
TAITP. HO CHl MINH DO TAC OONG CUA VIEC 0 0 THJ HOA
• I I I
PGS.TS. DINH XUAN
T H A N G , Vien Moi trudng va Tai nguyenThS. NGUYfeN THI THUY VAN
Dal hgc Khoa hgc Tu nhien TP Ho Chi Minh
Tom tat: Chat lirang moi tnrdng khong khi la mot trong cac yeu to quan trong quyet drnh chat lugng cugc song vl no anh hwang true tiep gen sire khoe con nguai. Tu" sir can thiet nay TP. HCM ga sdm xay gi/ng mang ludi quan trac 6 nhiim khong khi vai cac thong so quan trac nhu: SO^, NO^, CO, O3, NO 2, benzen, xylene, toluen, chi, hui tong, tieng on... Ngoai cac thong so ga neu, ham lugng phong xa trong khong khi cung la mgt thong so can gugc khao sat va ganh gia mgt each thuang xuyen, gac biet la tai cfp cao tir 1 gen 3m tinh tir mat gat. Tuy nhien, cho gen nay ham lugng phong xa trong khong khi van chua gugc khao sat mot each eo he thong.
Nhom tac gia ga tien hanh khao sat va ganh gia sa bg ham lugng cac gSng vi phong xa (U-238, Th-232, K-40, Cs-137) trong khong khi tai TP. HCM. Dong thai chung toi cung gua ra mgt sSgS xuat gang luu y trong viec giam sat va giam thieu 0 nhiem moi truang (ONMT) khong khi tai TP. HCM.
Abstract: The quality of air is one of an Important factors which affects gireetly to the human health. For this reason, Hochimlnh city has establisheg air polution monitoring stations with some main monitoring paramaters, such as: SO^, NO^, CO, 0^, NO^, benzene, xylene, toluene, /ead, TSP noise... Besige those parameters, the ragio-active Isotopes concentration in the air is also a parameter which Is geserveg to stugy frequently, especially In the high from 1 to 3 meter above the earth's surface.
However, untill now the radio-active isotopes concentration In the air hasn't studleg systematically.
To take full advantage of the nuclear analysis technology, we studied and evaluated the status of the radio-active isotopes concentration (U-238, Th-232, K-40, Cs-137) in the air in Hochimlnh city.
Form that point, we proposed some remarkable solutions to supervise and minimize the air population in Hochimlnh city.
I. CAC NGHIEN CUU TRONG VA NGOAI NUtfC Tren the gidi, viec Ung dung cac ky thuat hat nhan de xac djnh ham lupng cac ddng vi phdng xa trong khdng khf da dupe tie'n hanh tai nhieu nudc nhu My [6], Nga [7], Nhat [8], Pakistan [9]. Cac ke't qua thu dupe tU cac nghien eUu nay da cung cap cho cac nha khoa hpc nhirng dU lieu vd eiing quan trpng de danh gia xu hudng cung nhu nhUng anh hudng ciia chiing den sUc khde ciia con ngudi trong thdi ky phat trid'n rat nhanh cua khoa hpc - cdng nghe.
Tai Viet Nam, trong thdi gian qua cac don vj true thudc Vien Nang lupng Nguyen tir Viet Nam da thuc hien mdt sd cdng trinh nghien curu ham lupng phdng xa trong nhilu ddi tupng mdi trudng khac nhau nhu trong dat, thue vat [1], luong thue [2], thuc pha'm [3]. Tuy nhien, viec danh gia
hoat dp cac ddng vi phdng xa trong khdng khf van chua dupe quan tam dung mUc, cu the la tai TR HCM chi cd 1 tram quan trac su sa lang phdng xa toan eau, dat d dp cao 25m. Viec danh gia ham lupng phdng xa trong Idp khdng khi ma con ngudi thudng xuyen sinh sdng (tU b l mat da't den dp cao khoang 3m tren mat da't) ma van chua dupe tiln hanh.
II. muc TIEU, NOI DUNG, PHUfONG PHAP NGHIEN CUU
11.1. Muc tieu nghien CL^
Muc tieu dat ra cQa viec nghien ciru la dua trdn cac sd lieu thu thap, kit qua do dac tai hien trudng de danh gia hien trang ham lupng eae ddng vj phdng xa (K-40, U-238, Th-232, Cs-137) trong khdng khf tai 2 quan (Quan 1, Quan
11/2010 BAO HO LAO DQNG 13
KHOA H O C , CONG NGHE - CHUYEN GIAO
I
Tan Phii), TR HCM, tren cd sd dd d l xua't cac bien phap giam sat va giam thieu ONMT khdng khf do cac chat phdng xa.
11.2. No! dung nghien cuTu
De dat dupe muc tieu de ra, ndi dung nghien ciru chiing tdi da tien hanh bao gdm:
- Tdng quan ve d nhiem khdng khf do K-40, U-238, Th-232, Cs-137;
- Khao sat thue dja va lua ehpn vi tri lay miu, thie't lap sodd vj trila'y mau;
- Oanh gia so bd hien trang ONMT khdng khf do eae chat phdng xa trong khu vue khao sat;
- 0 1 xua't cac bien phap giam sat va giam thieu ONMT khdng khf do cac chat phdng xa.
11.3. Phi/dng phap nghien ciiru a. Nghien ciru ly thuyet
- Suu tam tai lieu cd lien quan nhu cac de tai nghien eiru khoa hpc, cac bai bao, saeh, cac bao cao kit qua quan trac mdi trudng khdng khf, eae tieu chuan Viet Nam hien hanh.
- Tham khao y kie'n eua cac chuyen gia trong viec lua ehpn dja diem lay miu, thu thap miu, do dae miu, dae biet la xir ly va danh gia kit qua phan tfch mau.
- Tdng hpp, phan tfch tai lieu thu thap, xir ly sd lieu...
b. Nghien ciru thuc nghiem - Khao sat hien trang khu vuc nghien cifu, lua chon vjtriliy mau, tien hanh thu thap miu.
- Sir dung phan mIm Mapinfo de sd hda ban dd va trinh bay so bd vj tri lay miu.
- Do dac miu, xir ly sd lieu.
- So sanh ke't qua do dac vdi eae tieu chuan va cac ket qua giam sat sa lang phdng xa toan cau ciia Vien Nghien cifu hat nhan de nhan xet danh gia.
c. Lay mau tai hien trudng
Do thdi gian va kinh phf cd han, chung tdi ehi ehpn ra hai quan de tie'n hanh lay mau la Q.Tan Phu (quan dang trong qua trinh dd thj hda manh me nen tde dp xay
N.I Ul 2007
dung nha cira, dudng xa... hien nay kha cao) va Q.I (khu dan eu hien hUu). Tai mdi quan, chung tdi ehpn 2 dja diem de tiln hanh lay miu (xem Hinh 1), eu the:
- Quan 1: miu dupe lay tai Trung tam Hat nhan TR HCM (TTHN), Sd Tai nguyen va Mdi trudng (Sd TN-MT).
- Quan Tan Phu: miu dupe lay tai Khu cdng nghiep Tan Binh (KCN T Binh) va Trung tam Y te Quan Tan Phu (TTYT T Phu).
Do TR HCM nam trong vung nhiet ddi gid mua, can xich dao nen thdi tilt tai day chia ra 2 mua rd ret: mua mua (tUthang5-thang 10); muakhd(tUthang 11 -thang4nam sau) nen chung tdi da lua ehpn lay miu theo hai mua.
Ngoai ra, de giam thieu sai sd cua miu thu thap chung tdi da tien hanh thu thap miu lap: tai mdi dja diem chung tdi tie'n hanh thu thap 3 mau cho mdi mua, nhu vay tdng sd miu chung tdi da thu thap la 24 miu/2 mua/4 dja diem.
Viec thu gom miu dupe tie'n hanh tren phim loc chuyen dung Pallflex membrane filters thdng qua he may hut khf Ecotech hivol 3000, loai may bui thu gom la bui lo limg tdng cdng TSP. Do cao lay mau each mat dat 1 m, la dp eao ma khdng khf bj xao trdn nhilu nha't do hoat ddng eiia con ngudi.
d. Phan tich mau
Viec phan tfch miu dupe tie'n hanh tren he may phan tfch phd gama diing detectd ban din sieu tinh khiet HPGe
sa BO \1 TRi L.4'V Ukv Bl'I K Hi H wh i
12 00
Q.Go Va'p
<lhi (Hu
Rauli gi»'i qliau, hliyeu Klui vH'c utJlii^n cii'll
Vi rri hy ui.iii
Nyni>'i thuc hieu ; NguyeuTWTlluy V.iu Nyirofi hii'tfug tl.i ii: PGS.TS. f>iuh Xua u Tlu ut
Colli fai lien : E.iu (tii di.i hiuhTi) HCM I< le 1 : 50.000
H/'n/i 1: Soldo vj tri lay mau bui khi
KHOA H O C , CONG NGHE - CHUYEN GIAO
Bang 1 .Ke't qua pt
Ky hieu mau
M4 M5 M6 M7 M9 M10 Mil M12 M13 M14 M15 M16 M17 M18 M19 M21 M25 M26 M27 M28 M29 M30
Ncfi lay mau
Sd TN-MT Q.1 Sd TN-MT Q.I Sd TN-MT Q.1 TTYT T Phu TTYT T Phu KCN T Binh KCN T Binh KCN T Binh TTHN (Q.I) TTHN (Q.I) TTHN (Q.1) Sd TN-MT Q.1 Sd TN-MT Q.1 Sd TN-MT Q.1 KCN T Binh KCN T Binh TTYTTPhu TTYT T Phu TTYT T Phu TTHN Q.1 TTHN Q.1 TTHN Q.1
lan tich ham iWcfng phong xa trong mau bui khi tai Quan Tan Phu
Thdi diem lay mau (thang
/nam)
06/06 06-07/06 07/06 07/06 07-08/06 08/06 08/06 08-09/06 09-10/06 10/06 10/06 11/06 11/06 12/06 12/06 12/06-01/07 01-02/07 02/07 02/07 02-03/07 03/07 03-04/07
The tfch miu
(m')
4925 4176 3866 4570 4338 4700 4182 4406 3049 4099 3783 4717 4406 4097 4397 3525 4613 4228 4818 4808 5270 5122
Khoi luong
bui
(g)
0,9 0,78 0,67 0,98 0,86 0,76 0,83 0,97 0,32 0,57 0 , ^ 0,98 0,95 0,89 0,97 0,74 1,2 1,12 1,13 0,63 0,95 0,74
U-238 (10'Bq/m')
Ham lUtfng
1,52 1,37 1,4 1,92 1,64 1,76 1,61 1,68 2,16 2,39 1,73 2,23 2,05 2,2 1,53 2,19 2,51 2,29 2,47 1,58 1,56 1,79
Sai so
0,46 0,45 0,53 0,79 0,54 0,71 0,57 0,6 0,73 0,7 0,72 0,65 0,73 0,8 0,67 0,73 0,95 0,81 0,81 0,54 0.61 0,66
Th-232 (10-'Bq/m')
Ham lUOng
4,97 5,35 4,09 7,29 4,71 3,74 8,54 5,96 2,76 5,2 7,05 8,23 7,12 8,02 9,13 6,64 6,79 8,33 8,51 3,48 11,42 6,67
Sai so
0,64 0,97 0,54 1,16 0,59 0,59 1,04 0,85 0,3 0,9 1 1,11 0,93 1,03 1,18 0,84 0,91 1,12 1,42 0,57 0,65 0,71
K-40 (10*Bq/m')
Ham luong
1,47 1,53 1,25 1,16 1,73 2,25 2 2,02 1,05 2,06 2,33 1,98 2 2,16 2,13 3,1 3,28 3,06 2,41 2,06 1,76 2,59
Sal so
0,25 0,27 0,22 0,21 0,3 0,54 0,34 0,35 0,41 0,34 0,43 0,33 0,34 0,37 0,37 0,52 0,57 0,51 0,41 0,22 0,3 0,24
Cs-137 (10- 'Bq/m')
- - - - - - - - - - - - - - - - - - - - - - (-; Du&i giai han phat hien)
Bang 2: Ham iMng trung binh cac dong vi phong xa trong khong khi theo mua tai cac vj tri quan trie khac nhau
Noi lay mau
SdTNMT
TTHN
TTYT T Phu
KCN T Binh Tram VNCHN
[1]
Miia
Mua Kho Mua Kho Mua Kho Mua Kho Mua Kho
Ham lUOng bui (10''g/m')
1,810 2,130 1,300 1,530 2,070 2,530 1,930 2,160 X X
Ham K-40 (10-''Bq/m5)
1,42 1,81 1,81 2,14 1,45 2,91 2,09 2,61 0,48 0,66
luong phong xa Th-232 (10-'Bq/m')
4,80 7,79 5,00 7,19 6,00 7,88 6,08 7,88 1,92 3,82
U-238 (10-'Bq/m^)
1,43 2,16 1,09 1,64 1,78 2,42 1,68 1,86 0,60 0,75 (- .• Dudi gidl han phat hien, X: khong co so lieu)
ciia Trung tam Hat nhan TP. HCM dupe thie't ke dat tai Phdng An toan BUc xa va Mdi trudng tU nam 1996. He may dupe trang bj Detectd Germanium sieu tinh khiet (HPGe) model GC1518 ciia hang Canberra eua My, ed cac dae trung ky thuat:
- Hieu suat tUdng ddi: 15%
- Op phan giai nang lupng: 1,8 keV tai dinh 1332 keV(Co-60)
- TT sd dinh/compton: 45/1 tai dinh 1332 keV (Co-60)
- The tfch detectd: 71,1cm' (dudng kfnh 5,34 em va chilu cao 3,20 cm)
III. KET QUA, THAO LUAN De danh gia hien trang ham lupng cac ddng vj phdng xa trong khdng khf, tac gia so sanh ket qua phan tfch tir cac miu thu thap eiia Sd TN va MT TR HCM
11/2010 BAO HO LAO DONG 15
H . i n i l i C v u g l -2.'8 110"" BViir"]
TC^ .\: a.I-l x 10- Dq/ii.
•
Mtii) niirn— [ — 1 — —
n n
S6' Si> TTHN TTHN TTYT TTYT hCN KCN Trsm Tr^m TNMT TNlvAT TPhu TPhu TBinh TBInh VNCHN VNCHN
Do thi 1: Ham li/dng K-40 trung binh theo mua tai cac vi tri quan trac khac nhau
8.00 -
4 . 0 0 2.00
H A 11 l l i l O
V i i g T l i - 1
" B q / l l l ' l 3 2
'T
St/ So. TTHN TTHN TTYT TTYT KCN KCN T r i i m T r ? n i TNMT TNMT TPhu T P h d T B i n h T B i n h VNCHN VNCHN
W i g
Do thj 2: Ham lifting Th-232 trung binh theo mua tai cac vi tri quan trac khac nhau
Hiini liioiig V-liS (lO'-'BVi""'!
TC\.\; S.14\ 10- Bfi/nt'
I -Mun ii.-iiit;
I I Mii.T iiitrn
— 1 — 1 —
n n
Si- S * TNMT TN^^^
TTHN TTHN TTYT TTYT KCN KCN Trgm Trsm , TPhO TPhu TBInh TBinh VNCHN VNCHN
Bo thi 3: Ham lifting U-238 trung binh theo miia tai cac vj tri quan trie khac nhau
(xem Bang 1) vdi cac ket qua quan trac roi lang phdng xa toan eau tai TR HCM nam 2006 eua Vien Nghien eiru Hat nhan (Tram VNCHN) [5]. Ddng thdi tac gia so sanh cac ket qua phan tfch vdi TCVN v l ham lupng cho phep ciia cac ddng vj^phdng xa nay trong khdng khf [4] de danh gia mUc dp nguy hai eua chiing ddi vdi sire khde con ngudi.
TCrcac sd lieu do dac taing binh eiia miu {^mz neu trong Bang 1) va ke't qua quan trac rd lang phdng xa toan cau tai TR HCM nam 2006 cua Vien Nghien eiru H^t nhan [5], chiing tdi da thdng ke sd lieu theo tUng mua cho timg vj trf quan trac de danh gia su khac nhau v l ham lupng cac ddng vj phdng xa eiia eae mau bui khf (xem Bang 2), sd lieu da dupe bieu diln dudi dang dd thj 1,2 va 3.
Ket qua phan tfch ham lupng phdng xa trong cac miu bui khf dupe thu thap tai eae vj trf quan tam ndi tren theo tirng quan dupe trinh bay trong Bang 1.
TU eae do thi 1, 2 va 3 ta cd the riit ra mot sd nhan xet nhu sau:
- Cac ddng vj phdng xa tu nhien K-40, Th-232 va U-238 trong eae mau thu thap eung mdt mua, vdi cac vj trf lay mau khac nhau cd su chenh lech. Dilu nay la do ham lupng bui tai cac vj trf lay mau khac nhau khdng gidng nhau, tuy nhien su chenh lech nay khdng dang ke. Rieng ham lupng eiia ddng vi phdng xa nhan tao Cs-137 rat thap nam dudi mire phat hien ciia may.
- Ham lupng cac ddng vj phdng xa tu nhien cd trong mau bui khf tac gia da thu thap deu cao hdn so vdi miu CLia tram quan trac dat tai TR HCM cua Vien Nghien ciru Hat nhan dat d dp cao tfnh tU mat da't la 25m, vdi 2 dp cao lay mau khac nhau thi ham lupng bui se khac nhau, vj trf lay mau sat mat dat se cd ham lupng bui cao han nen ham lupng eae ddng vj phdng xa trong mau eung cao han.
- Hoat dp eiia cac nguyen td phdng xa thu dupe trong qua trinh quan trac khdng khf diu thap han gia trj ndng dp gidi han nen chua gay nguy hai den mdi trudng va eon ngudi.
IV.DANHGIAANHHaOTNGCUA TOC DO 0 0 THj HOA TOTI HAM LirOTNG CAC CHAT PHONG XA TRONG TirONG LAI
TR HCM vdi sd lupng dan cu ngay cang tang do qua trinh dd thj hoa, CNH da thu hut mdt luc lupng ngudi nhap eu kha Idn vao TR Dan sd eua TRHCM (theo thdng ke cua trang web - Bach khoa toan thu 28/12/2007) la 7,163 trieu ngudi, do la chua ke hang tram ngan ngudi vang lai hoac chua dupe thdng ke do khdng khai bao tam trii tai cac dja phuong. Tdc dp dd thj hoa ngay cang tang vdi eae khu dan cu, khu cdng nghiep, eae NM, XN, cd sd SX ngay cang tang keo theo viec tang dang ke nhu eau di lai ciia cdng ddng. Do cac phuong tien cdng cdng
KHOA HOC, CONG NGHE - CHUYEN GIAO
chua dap Ung dupe nhu cau nay nen eae phuong tien giao thdng ca nhan ngay cang tang dang la mot ap lue rat Idn eho giao thdng van tai. Sd lieu thd'ng ke mdi nha't (6/2006) eho tha'y TRHCM hien cd 3.228.288 xe may, 344.836 xe d td, trung binh hang thang cd them 37.790 xe may va 960 xe d td dang ky mdi cho tha'y mUc dp gia tang dang ke ciia cac loai phuong tien nay. Cac sd lieu tren cho tha'y ndng dp bui va cac chat phdng xa trong khdng khf se ngay cang tang do td'c dp dd thj hoa, cdng nghiep hoa ngay cang phat then. TU dd eho tha'y mUe dp anh hudng ciia chiing tdi mdi trudng se tang len. Day la mdt van d l rat Idn va phUe tap, chung tdi se d l cap d bai bao khac khi ed dilu kien.
V. MOT SO BIEN PHAP GIAM THIEU HAM Ll/ONG CAC CHAT PHONG XA TRONG TlTONG LAI De ed cd sd de xua't cac bien phap cu the nham giam thieu mUe dp d nhiem do eae chat phdng xa va chi trong tudng lai, nhdm tac gia xin d l xuat cac bien phap trudc mat nhu sau:
1. Can phai xay dung mang ludi cac tram quan trac phdng xa trong khdng khf ed djnh (quan trac roi lang phdng xa toan eau) va di ddng (quan trac phdng xa xung quanh cac ngudn phat thai cue bd) tai nhilu diem khac nhau tren dien rdng tai nhilu diem "nhay cam" khac nhau tren dja ban TR HCM; tU dd ed cd sd de danh gia mdt each chfnh xac va day dii nha't v l hien trang d nhilm do eae chat phdng xa tai TR HCM hien nay;
2. Quy hoach, sap xep hoac han che dau tu cac ca sd SX phat sinh cac chat d nhilm phdng xa hpp ly nham giam thieu ndng dp eae chat phdng xa trong khdng khf;
3. Phat trien giao thdng cdng cdng, han che eae phUdng tien ea nhan nham giam thieu ket xe, dap Ung nhu eau di lai eiia ngudi dan gdp phan giam thieu phat thai cac chat d nhilm;
4. Dau tukinh phf thfch hpp phuc vu eho cac hoat ddng kiem tra, giam sat, danh gia cac ngudn d nhiem neu tren.
VI. KET LOAN VA KIEN NGHj VI.1. Ket luan
Qua qua trinh nghien ciru, chung tdi da dua ra mdt sd nhan djnh ve nhUng van d l lien quan den ham lupng cac ddng vi trong khdng khf tai TR HCM:
- Hien trang v l d nhiim phdng xa trong khdng khf:
nhin chung hoat dp ciia cac nguyen td phdng xa thu dupe trong qua trinh quan trac khdng khf diu tha'p hon gia trj ndng dp gidi han. Tuy nhien, ham lupng eae chat nay tang khi ham lupng bui tang, dieu nay eho tha'y rat rd khi tac gia dd'i chieu so sanh ke't qua phan tfch giUa mua
khd va mua mua.
- Hien trang cdng tac giam sat ham lupng ehi va cac ddng vj phdng xa trong khdng khf chua dupe quan tam dau tu dung mUc, dae biet la viec giam sat ham lupng cac ddng vj phdng xa. Tai TR HCM chi' cd mdt tram quan trac roi lang phdng xa toan eau (dat d dp cao 25m so vdi mat dat), trong khi dd ham lupng phdng xa tu nhien trong Idp khdng khf ma eon ngudi thudng xuyen sinh sd'ng (tU be mat da't den dp eao khoang 3m) dang bi xao trdn va tang len dang ke do qua trinh dd thj hda lai chua cd tram quan trac nao dupe xay dung.
- De cd Cd sd de xua't cac bien phap eu the nham giam thieu mUe dp P nhiem do cac chat phdng xa va chi trong tUdng lai, can thie't phai thue hien ddng bp eae giai phap da neu d tren, tU dd ed nhffng djnh hudng chie'n lupe va dau tu phu hpp nham giam thieu anh hudng xau den mdi trudng trong tuong lai.
VI.2. Kien nghj
Nhdm tac gia rat mong mud'n tie'p tuc eae nghien cUu tilp theo tren dja ban toan TR HCM. De nghj cac cd quan quan ly nha nude tao dilu kien de nhdm nghien cUu cd the thuc hien nghien cUu eiia minh.
Tai lieu tiiam idiao Tieng Viet
[1] Ngo Quang Huy, Tran Van Luyen, Nguyin Van Mai (1999), Khao sat nen phong phong xa mdi trudng doi vdi mgt so doi tugng moi trudng tai TP HCM, Hgi nghi Vat ly va Ky thuat Hat nhan lan thir 3, Da Lat.
[2] Nguyen Van Mai (2003), Phan tich, danh gia va kien nghi mgt tieu chuan quoc gia ve ham lugng phdng xa Cs-134, Cs-137, Th-232, U-238, K-40 trong cac mau gao xuat khau chinh eua khu vuc dong bang song CO'u Long, Bao cao de tai ca sa, Vien Nang lugng Nguyen tir Viet Nam, Ho Chi Minh.
[3] Nguyin Van Mai (2004), Bude dau phim tich, danh gia ham lugng phong xa Cs-134, Cs-137, Th-232, U-238, K-40 trong mgt so mau thuy hai san (ca, torn, muc,...)d khu vue Nam bg Viet Nam, Bao cao de tai ca sd, Vien Nang lugng Nguyen tir Viet Nam, Ho Chi Minh.
[4] Tong cue Tieu chuan do ludng chat lugng (1987), TCVN 4397-87- Quy pham an toan birexa ion hda, Ha Ngi.
[5] Trung tam Nghien ca'u moi trudng (2007), Bao c^o ket qua quan trac va phan tich phong xa moi trudng tai TP HCM tir th^ng 01 den thang 12 nam 2006, Vien Nghien ciru Hat nhan Da Lat, Da Lat
Tie'ng Anh
[6] John Kada and Coling. Sanderson (1996), Radionuclides in Surface Air at BRW, MLO, SMO, and SPO During 1994 and 1995, Environmental Measurements Laboratory, U.S. Department of Energy, New York.
(Xem tiep trang 23)
11/2010 BAO HO LAO DONG 17