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31(4)[CD],299 J(;6 Tap chi CAC KHOA HOC VE TRAI DAT 12 2009 NGHIEN CLTU DAC DIEM DI T H U 6 N G KHI PHONG XA PHUC VU TIM KIEM PHAT HIEN QUANG AN VA DANH GIA MLTC DO 6 NHI6M MOI TRUONG TREN MOT SO M 6[.]
31(4)[CD],299-J(;6 12-2009 Tap chi CAC KHOA HOC VE TRAI DAT NGHIEN CLTU D A C DIEM DI T H U N G KHI PHONG XA PHUC VU TIM KIEM PHAT HIEN QUANG AN VA D A N H GIA MLTC D O N H I M MOI TRUONG TREN M O T SO M QUANG CHUA CHAT PHONG XA LE KHANH PHON NGUYEN THAI SON N G U Y I N V A N N A M , N G U Y S N ANH I M d DAU Nude ta thudc mien nhiet ddi hau ndng dm mua nhieu, lap ddt da be mat chiu tae ddng phong hod xam thirc manh me Bdi vay da phdn cac md quang ndi chung va cac md quang phdng xa ndi rieng thufte dang quang "dn", cac than quang thudng bj chdn viii dudi eae tdng phii bd rdi Do phdng xa, dae biet la radon cd kha nang Ian truyen di xa khdi ddi tupng sinh ching nen phupng phap phdng xa la phupng phap phdng xa cd chieu sau nghien cuu (chieu sau phat hien quang dudi tdng ddt phil) Idn nhdt Cac ddi dirt gdy, dap vd dia chdt tao dudng ddn eiing gay cac di thudng phdng xa Mudn nang eao hieu qua dp dung cac phuong phap phdng xa nghien ciru dja chdt va tim kie'm quang phdng xa, edn thie't phai lam sang td eae dae die'm cila di thudng phdng xa tren cac ddi tupng dia chdt khdc nhau, lira chpn dupe thie't bi ky thuat ed dd nhay, dd tin eay eao, dua dupe tieu ehudn dia chdt - dia hod - phdng xa phan biet dupe dj thudng quang (lien quan vdi eae md chira chdt phdng xa) vd di thudng phi quang (lien quan vdi cac da ed hoat dd phdng xa cao va cac ddi duft gdy dap vo dia chdt) Trong dieu tra mdi trudng cdn lam sang td dae die'm phat tan vd tieh tu radon Idp quyen sat mat ddt tu cac ddi tupng dia chat khae (phu thude vao loai md quang, cdu triie dia chdt) va dae diem bie'n thien ndng dO phdng xa theo thdi gian, theo nhirng bie'n ddi cila thdi tie't Tir dd dua quy trinh quan trde mdi trudng gdm lira chpn thie't bi, mang ludi, thdi gian quan trdc, xii ly tdi lieu nham xae dinh chinh xae ndng dd phdng xa khdng TUA^ phuc vu viec tinh lieu ehie'u qua dudng hit thd va danh gia mire dp nhiim phdng xa, mot nhirng dang d nhiem phdng xa nguy hiem nhdt kho phdng tranh nhdt Nhirng dieu ndi tren ehirng td tinh cap thiet cila d^ tai nghien cUu vd cung la npi dung dupe de cap bai bao II NGHIEN C i r u XAY DUNG M O T SO MO HINH T H A N QUANG CHL/A CHAT PHONG XA CUANUdCTA De lam sang td eo sd khoa hpe ap dung phuong phap phdng xa cong tac tim kieni nhdt la tim kie'm phat hien cac than quang an va danh gia nhiem mdi trudng, chung toi da tien hanh xay dung mo hinh than quang ehUa chat phdng xa dien hinh etla nude ta Id quang ddt hie'm va sa khoang ven bie'n, ddng thdi tinh toan xae dinh eae di thudng phdng xa tren mo hinh quang 1, Mo hinh than quang sa khoang titan Theo eae tai lieu hien cd cua Lien doan Dia chat V (1984), Nguyen Kim Hoan (1985), Nguyen Tie'n Thuan (1998), Vd Ngpc Anh (2004), quang sa khoang titan cd ham lupng khong ddng deu, phan bd tap trung d eae bai cat gdn cac eo, vinh, d phdn phia nam hoac bdc cac mom nho bien noi cd dieu kien de hinh cac than quang dat gia tri cdng nghiep Tir sd lieu cua cac tai lieu ke tren, co the mo hinh hda cac than quang sa khoang ven bie'n mien Trung nhu sau : cac than quang ed chieu day trung binh tu 1,4 m de'n 4,5 m bao hda theo tia gamma 299 (chieu ddy bao hda theo tia gamma h > m), be rdng 40 m - 1,000 m, chieu dai tu 800 m de'n 8.000 m deu bao hda theo tia gamma va cd the coi nhu than quang ed dang Idp nam ngang keo dai vo han Chi trir md An My va Xuong Ly, tai eae md khae, mot bd phan than quang bi phu vdi be ddy tang phu trung binh tir hang chuc de'n 70 cm, chieu ddy tdng phu cue dai tdi 4,0 met Trong cac than quang cd mdi tuong quan ty le thuan giua ham luong quang ilmenit vdi ham lupng cac khoang vat phu nhu zircon vd rutin Trong zircon ham lupng cac nguyen td phdng xa U^Og khoang 0,011 - 0,014 %, Th02 khoang 0,0108 - 0,0128 % Trong monazit ham lupng Th203 chie'm ty le tU 2,31 de'n 6,52 % trung binh 3,79 % Ngudi ta da xac dinh cac ddi sa khoang ham lupng thori bie'n thien khoang 0,0009 - 0,018 %, Quang sa khoang vdi gia tri ham lupng bien ciia ilmenit la 10 kg/m^ cd hdm lupng q-n, ~ 0,002 %, quang dat ham lupng cdng nghiep (>50kg/m ) ed q-n, > 0,01 % Nhu vay md hinh die'n hinh ddi vdi cac than quang sa khoang ven bie'n mien Trung la than quang chira chdt phdng xa dang Idp nam ngang, cac kich thudc iing vdi trudng hpp niia khdng gian birc xa vo han Quang Id tren mat ddt hoac bi phu cd chieu ddy tu hang chuc centimet de'n 3- m phdn chil ye'u la cat hat nhd Mo hinh than quang dat hiem chira chat phong xa Tai nhieu vung cua nude ta nhu Lai Chau, Lao Cai, Yen Bai ed cac md ddt hiem vdi trir lupng Idn thudc loai md trung binh va Idn tren the' gidi Trong quang ddt hie'm cd chira cac chat phdng xa Th, U Quang ddt hie'm cila nude ta thudng cd dang tui, dang d, dang mach hoac dang thau kinh Ham lupng tdng oxid ddt hie'm TR2O3 tu mdt vdi phdn tram de'n tren 30 %, trung binh 10 % Ham lupng Thori da't hie'm vd phong hod la 0,0199 % de'n 0,0441 %, ddt hie'm quang gde la 0,0087 % de'n 0,0204 %, ham lupng urani ddt hie'm tu 0,001 % de'n 0,01% Cac than quang ed be ddy til m de'n m, trung binh 3-4 m, chieu dai tU hang chuc tdi hang tram met Tuang tu nhu ddi vdi quang sa khoang ven bie'n, md hinh than quang ddt hie'm cd hi rdng hang chuc met, chieu dai tdi hang tram met, chieu ddy trung binh 3-4 m, cue dai tdi m ed the' coi nhu la Idp quang nam ngang keo dai vd han 300 Tinh toan sir phan bdnong phong xa tren mo hinh lop quang Viec tinh toan sir phan bd ndng dp phdng xa dupe thue hien chung cho hai ddi tupng sa khoang ven bie'n va quang ddt hie'm dudi dang md hinh mdi trudng Idp nam ngang vd han, lap thir hai la Idp quang phdng xa nam phia dudi vdi cac tham sd : ham lupng chdt phdng xa q2, ndng dd phdng xa N2, mat dd P2, he sd Id rdng ri2, he sd khue'eh tan D2, a()2 - luong eman tu thoat vao cm da giay, (Bq/cmls), he sd eman hda Kc2 Ldp thir nhdt la ldp phu nam d phia tren cd chieu ddy h va cac tham sd N|, pi, r|i, D|, K^ {hinh 1) -Nkh L_ll H N„ N|, r|i.Pi Di,Kci N N„ qo •dz Q T O-i N-> n? 0-) D? Hinh Md hinh tinh sir phan bd ndng dd phdng xa ldp eman hda vd han (ldp quang phdng xa) va trdm tich phil Ndng dp phdng xa N mdi trudng cd dp Id rdng r| bie'n ddi chi theo hudng true z Phuong trinh vi phan can bang lupng phdng xa ldp dx cd dang sau : : d -(NTISC/Z) = Q,-Q2-i-a„&/z-?iNriSJz (1) dd : ddng phdng xa di qua dien tich S cua ldp dz Q = DSdN/dz-I-VNTIS ' a„ = N,;v = K,qp} 3,7.10"' (2) (3) Sir phan bd ndng dp phdng xa theo chieu sau Idy mdu z dupe xac dinh bang each giai phuong trinh vi phan (1) [2, 6, 7] a) Tri/dng hap be day tang ptiCi ti >10cd the coi nhu h ^ 00 Ndng dp phdng xa tai dd sau Idy mdu z dupe tinh theo cdng thire [2, 6) : -J|(.-.) dd No - ndng dd phdng xa tai be mat ldp quang (5) Wo=N2» l-{-dcth{b^h) Bang ly thuye't va thirc nghiem ed the xac dinh ndng dd radgn khdng sat mat ddt hang nghin Idn nhd han gia tri cua nd N, cila nd mdi trudng ddt da Khi khdng cd gid thi ndng dp radon quye'n giam cham theo dd eao, cdn ndng dd toron giam rdt nhanh va hoan toan triet tieu d khoang each khdng qua 10 cm each mat ddt |2, 6| dd N2x - ndng dd phdng xa Idp quang bao hda KET QUA AP DUNG N = Nf,e Rn N 2« (4) l,2.IO-'K,i,„.q„.K,^ ri I (6) /V]i = , l l X T n q n , ^ ^ n I qu (%), q-n, (%) - ham lupng urani, thori ldp quang, K^Kn, KCTH - he sd eman hda cua radon va toron, Kcb - he sd can bang phdng xa eila ddy urani, p - mat dd, r| - dp Id rdng eila quang d = D,b,/D2b2 ; h^^^XrjJD^ b) Be day tang phu hOru han (h 60 lao 1110 DO CHI I" t ; ; j i.^i>itiirii ck-inv; [z: ^*o Ito •Kfo yfo DAN pi;-.|_-L Q H e D ^ ii> Syi'oit y.^\ * • Uixofi iLKJy K A U t Hinh Mat cat dia cha't - phong xa tuye'n mo da't hie'm X 304 ito Ddi vdi muc dich nghien cim mdi trudng phdng xa, hinh dua so dd dang tri ndng dp radon khdng Tren dd thdy rd cac than quang ddt hie'm phdng xa da gay cac di thudng ndng dp radon vuot qua tieu ehudn an toan eho phep (NKn> 100 Bq/m ) ed dien tich phan bd Idn gdp hang chuc, hang tram Ian dien tich phan bd cua than quang Gia tri cue dai ciia di thudng tren mdt sd than quang dat tdi gia trj NKn > 500 Bq/m Idn gdp Idn tieu ehudn an toan eho phep De dang nhan thdy di thudng ndng dp phdng xa ed xu hudng Ian n5ng theo hudng dong nam - tay bdc Uung vdi hudng gid mua chii dao va phuong thung lung dja hinh cua vung md Day la dieu can luu y quy hoach kie'n true cac cong trinh nha xuong san xudt va dan dung cila vung de tranh tac hai d nhiem phdng xa ddi vdi siic khoe ngudi i: H I D A N [ZD ILJ 1 ED CD 1^ IH3 EEEl Du^m ,1.: R.,,1oii,;, ?.,- iii DiiOup ilouy UnvujJ Radou Dinli QUI ^Ti cao boa^.Mioi Difouy 10 E)iioii^ UIOQ L»up L>aQ r>i ilmwa? iioug lio inctou n o u ^ iiLiou^ iilii \ i f i qii.n ri^u cliu.'^ii an lo.iii olio j-Miep Than quSng flat hifim - Baril - Fluorit Hinh So dd ddng trj ndng dd radon khong md X K E T LUAN 1, Tren ed sd xir ly tdng hpp eae tai lieu dja chdt phdng xa hien cd da dua md hinh dae trung eila than quang sa khoang ven bie'n mien Trung va quang ddt hie'm chira chdt phdng xa, cac cdng thirc tinh toan ly thuye't ndng dd phdng xa toron va radon da lam sang td dae die'm di thudng phdng xa tren md hinh than quang lam co sd lufln giai tai lieu thue te'eila cdng tae tim kie'm phat hien quang dn Ke't qua khao sat thue te' tren vung md sa khoang miin Trung vdi hang chuc nghin die'm gamma, hang nghin diem phdng xa da minh ehirng kha nang tim kie'm phat hien quang dn theo dae die'm dj thudng phdng xa : quang sa khoang ham lupng cdng nghiep Id tren mat ddt, gia trj ndng dd toron phu thudc vao ham luong quang nhung ludn ludn Idn gdp - Idn ndng dO radon Khi quang bj phil bdi eae ldp bdi tieh cat set thi eae gia trj eudng d6 gamma, ndng dp phdng xa deu bj giam di Khi be ddy ddt phu h > 80 cm (chieu sau tdi da ciia cac Id chodng Idy mdu khi) thi ndng dp toron se nhd han ndng dO radon Tren cac than quang cd ddt phil ddy (khdng qua 10 m) chi cd the' phat hien dj thudng yeu cua ndng dp radon cdn di thudng gamma va dj thudng ndng dp toron bj triet tieu Ke't qua khao sat phdng xa tai khu md X chi ro phupng phap radon cd the' phat hien dupe than quang ddt hie'm bj chdn vCii dudi tdng ddt phu cd 305 dd ddy tCr 5-7 m tdi 10 m Cac than quang ddt hie'm phdng xa da gay cac dj thudng ndng dd radon khdng NR„ > 100 Bq/m vuot qua tieu ehudn an toan cho phep tren dien tieh Idn gdp hang chuc, hang tram Idn dien tieh phan bd ciia cac than quang Tai mdt sd than quang bien dd cue dai dj thudng ndng dd radon khdng dat tdi gia trj NRnmax > 500 Bq/m"* Idn gdp Idn tieu chud'n an toan cho phep, Dj thudng phdng xa cd xu hudng Ian truyen theo hudng gid thdi va phuang thung liing dja hinh Day la di^u edn luu y quy hoach kie'n true eae cdng trinh san xudt, cdng sd, dan dung d^ tranh tac hai bijc xa d nhiem phdng xa ddi vdi siic khoe ngudi, Bdi bao hoan dua tren ke't qua nghien cim cua di tdi khoa hpe trpng die'm cdp Bd, ma sd B2008-02-57TD Ngudn tai lieu la ke't qua nghien ciru eua di tai vd thu thap tiif Luu trir Cue Dja chdt va Khoang san Viet Nam TAI LIEU DAN [ I ] VO NGOC ANH, 2004 : Luan an Tie'n sT dja chdt "Nghien cim dae die'm dj thudng phdng xa du bao tai nguyen sa khoang titan va danh gia anh hudng eila mdi trudng phdng xa ddi ven bie'n Trung Trung B(3", Luu trir Thu vien Dai hpe Md - Dja chdt Ha Ndi [2] V,I, BARANOV, A.X XERDIUKOVA L.V GORBUSINA I.M NAZAROV, Z.M EPfflMKINA 1966 : "Cac bai toan va thi nghiem phdng xa" Nxb Atomizdat, Moskva (Nga van) [3] NGUYfiN VAN NAM, LE KHANH PHON, 2006 : "Nghien cull su phan bd ndng dd phdng xa phuc vu tim kie'm, tham dd va nghien cim mdi trudng quang sa khoang ven bi^n", Tuye'n tap bao cao Hdi nghj Khoa hpe Idn thii 17, Dai hpe Md - Dja chdt [4| NGUYEN VAN NAM, 1984 : "Bao cao ke't qua tim kie'm quang titan sa khoang ven bie'n thudc vung hoat ddng eila Lien doan Dja chdt V" Luu trir Cue Dja chdt vd Khoang san Viet Nam, Ha Ndi 306 [5] G.F NOVIKOV, 1989 : Thdm dd phdng xa, Nxb Nauka, Leningrad (Nga van) 161 LE KHANH PHON, 2007 : Bao cao "Dae trung trudng phdng xa va d nhilm phdng xa thi xa Lai Chau, huyen Tam Dudng va huyen Phong Thd" [7] Dia vat ly hat nhan tham dd (edm nang Dja vat ly), 1986, Nxb "Ldng ddt", Moskva (Nga van) SUMMARY Researching anomalous features of radioactive gas to detect covered ore and to evaluate environmental contamination in the radioactive mines The theoretical calculations of concentration of radioactive gas radon and toron on the model of the typical body and mining mineral sand at Central coastal zone and the radioactivities contain of rare earth mine indicate : the body of layer-ore contains horizontal substance with the dimensions correspond half-space of infinite radiation The result detects hidden-ore by characteristic of anomaly of radioactive gas At the exposed surface of ore-body, anomaly of toron-gas depends on content of ore by always larger than to times of anomaly of radon gas When the ore is covered, the concentration of toron-gas will reduce quickly ; when the thickness of covered soil h > 80 cm, the concentration of toron-gas will be smaller than radon-gas, but when the thickness m < h 100 Bq/m^, exceeding safety value Anomalous areas are often to hundered times large than distributed area of ore body, and tend to transmit by wind direction and valley rellief Ngay nhan bdi 04-11-2009 Trudng Dai hoc Mo Dia Chdt Lien doan Dia chdt Xa hie'm