I Nghien cihi & Trao ddi
KHAO SAT AMMONIA VA HYDROGENSULFIDE TRONG
CAC MO HINH NUOI TOM SU TREN CAC LOAI D A T K H A C NHAU 6"
TINH CA MAU
ThS. Cao Phu'O'ng Nam
Vien Thiiy Igi va Moi trudng - Dai hpe Thuy Lgi
J i jphien ciru duge tien hanh a 15 hp. Mil hp ed dien tich nudi trong khoang 2 ha/mo hinh, vdi
# \ f 3 loai md hinh Quang canh eai tiin (QCCT), Tdm liia (TL) va Tham canh (TC) tren 04 loai dit I V ddt phen hoat dpng man trung binh (Sj2M), ddt phen tiim tang ndng man nang (Sp1Mn), ddt man trung binh (M) vd ddt man nang (Mn) (thupc dia ban 6 xa eita bin huyen tinh Ca Mau, nam 2002-2003 va tir thang 8 din thdng 12 nam 2007). Ham lugng trung binh chdt hu'U ca vd dam hu'u ca di phdn hiiy trong ddt, biin day ao a cae md hinh nudi tdm sit tren dat {Sj2M), dat (SpIMn) cao han tren ddt (M), ddt (Mn). Ning dp trung binh Ammonia (N-NH^ ) , Hydrogen sulfide (H2S) trong nude d eae md hinh nudi tdm sii tren dit Sj2M, Sp1Mn cao han tren dat M vd Mn, tang cao vao cdc thdi diem thdng S, thdng 6, thdng 9 eita mua vu nudi, tuang irng vdi thdi diim tdm dugc 1-2 thang tudi. Nong dp trung binh Ammnonia va Hydrogen sulfide trong biin day cao gip hang chuc din hang tram ldn so vdi trong Idp nude phia tren eiia day ao nudi: tren trang va dudi muang ciia ao nudi tdm a cac mo hinh QCCT va TL cao han va biin thien Idn han so vdi md hinh TC. Ty le tdm sing d cac md hinh QCCT, TL dat nhd han 20%, trong khi dd a md hinh TC ty le tom sing dat tren 70%, ddn din nang suit tdm nuoi a cac md hinh QCCT, TL dat thdp han rat nhiiu so vdi md hinh TC.
1. Dat van de
Tinh Ca Mau cd tong quy dat 520.175 ha, trong dd nhdm d i t man cd dien tfch 208.500 ha, vdi 32.600 ha d i t man nang va 175.900 ha d i t man nhe, chilm 40,0% dien tfch t y nhi§n. Nhdm d i t phen ed dien tfch 271.926 ha, g i m : d i t phen t i l m tang (190.640 ha), vd d i t phen hoat dpng (81.285 ha).
Nhdm dat phen nhiem man khoang 30.387 ha.
Nhdm d i t than biin, vdi dien tich khoang 8.698 ha.
Nhdm d i t bai boi vdi dien tich 15.483 ha [1]. Tir nam 2000, phan Idn d i t nong nghiep chu yeu Id trong liia da dugc chuyen doi sang nudi tom su va trong lua luan canh, tinh d i n thdi d i l m c u l i nam 2008 dien tich nudi td:Ti su tren toan tinh dat tren 248.000 ha, ehu y l u la . ^6 hinh quang canh cai t i l n . Theo quy hoach nuoi t i i n g thuy san tinh Cd Mau d i n nam 2020 dien \.i^ dat dugc sir dung cho nudi torn sii la 235.000 ha v 5 trif 3 lua vdi cae md hinh san xuat:
quang canh cai t i l n , tom liia, tham canh va ban tham canh, trong 5d t-§n 222.000 ha chu y l u la md
hinh quang canh cai t i l n vd tdm liia.
Trong nudi tom su, sy hien dien va tich luy chat hiru eg q u y l t djnh r i t Idn den chat lugng mdi trudng nuoi. Sau moi vu nudi, Idp biin lang tren cac vudng, d i m nudi torn tham canh cd the day 40 - 50 cm, quang canh cai t i l n va tdm lua 20 -SO cm phii khap dien tfch day cae ao nudi tdm. Biin ao bao gom hon hgp ciia c h i t hu'u ca cd san trong dat, tao chit, thire an d u thira.... Theo Giao trinh Quan ly chat lugng nude nudi thiiy san, x u l t ban nam 2002, trong nudi tham canh tdm ea chl sir dung duge to!
da 75% lugng thire an, 10% iugng thire an hda tan trong nude va 15% lugng thire an thira. Trong qua trinh phan hiiy c h i t hu'u ca, dii d d i l u kien hao khi hay y i m khi thi san pham cuoi ciing deu cd NH3 vd CO2 d cac tl le khac nhau.
NH2-CH2-COOH + 3/2O2 = NH3 + CO2 + H2O NH2-CH2-COOH + 2H2O = NH3 + 2CO2 + 3H2 Trong d i l u kien y I m khi mot so lodi vi khuan
Tap chi Khi tifgfng Thuy van * Thang 4/2009 31
Nghien ciiu & Trao doi
Desulfovibrio, Desuifotomaculum sir dung dxy cua sulphate d l oxy hod c h i t huu ca, san pham tao thdnh Id acid hu'u ca, nude va Sulfua (S^-).
2R-CH2-OH + SO42- = 2 R - C 0 0 H + 2H2O + S2- Tat ca cac c h i t ndi tren nhu H2S, NH3, la cae c h i t d6c eho tdm, gay hai d i n sire khoe tdm. Trong nudi tdm sii ndng dp ammonia < 0,1 ppm va khong dugc cd sy hien dien eiia hydrogensulfide.
De tim h i l u mdt s l v i n d l v l N-NH3 va H2S trong cae md hinh san x u l t tren cac loai dat canh tac khac nhau chiing toi da t i l n hanh d l tai nghien ciru: khao sat d i l n b i l n n i n g dp H2S, NH3, trong ao nudi tdm quang canh cai t i l n (QCCT), torn liia (TL) tren cac loai d i t : d i t phen hoat dpng man trung binh (Sj2M), d i t phen t i l m tang n6ng man nang (SpIMn), d i t man trung binh (M) va dat man nang (Mn) tinh Ca Mau.
2. Phu'O'ng tien va Phu'O'ng phap nghien cu'u a. Pham vi nghien cii'u
+ Chpn 15 hp, moi hp cd dien tich nudi t r i n g khoang 2 ha/m6 hinh, vdi cac md hlnh nudi tdm quang canh cai t i l n (QCCT), tdm liia (TL), tdm tham canh (TC) d 6 xa thupc b i n huyen tren 04 loai d i t : xa H i Thj Ky (Sj2M), xa Thdi Binh (Sj2M), xa Tan Hung Dong (M), xa Phu Tan (SpIMn), xa Viet Khai (SpIMn), xa Ta An Khuang (Mn) vd xa Tan Duyet (M) thudc cae huyen Thdi Binh, Cai Nude, Phii Tan vd Dam Doi.
+ Md hinh nudi tdm QCCT, TL dugc thilt ke vdi muang bao chu vi d i t , d i t dao dugc diing d i p bd bao giu nude nudi tdm. Muong bao thudng sau khoang 1,2 -1,5 m, rdng 2-3 m, tuy thupc dien tfch d i t Idn nhd cd the ddo them muang giira. Muang bao vd muang giCra cd tac dung, c i p thoat nude, la nai tru ngu chii y l u ciia tdm. P h i n d i t edn lai gpi la trang. Trang Id nai tom hoat ddng vd k i l m moi. Dien tich trang thudng chiem tren 2/S dien tich ao nudi.
Nude thud'ng d u g c cap true tiep vdo ao nudi md khong qua xir ly. Mat dp tha giong 1-S eon P15/m^.
Tdm s i n g b i n g thire an t y nhien trong ao. Ky thuat nudi bao g i m : sen vet biin, phai trang, bdn vdi, chpn
giong, l i y nude vao va tha giong, va chd thu hoach, chu y l u nhd vao t y nhien. D i i vdi md hinh nudi tham canh, dien tich 500 m^/ao, g i m hai ao (ao nudi va ao xij ly nude d l cap eho ao nudi). Dp sau ao nudi tir 1,2 - 1,5 m, mat dp tha gilng 30 con/m^, cho an b i n g thire an cong nghiep, eo he thong cap dxy vao day ao. Mdi trudng nude, biin day, cham sdc tdm nudi dugc theo doi vd k i l m soat theo dung quy trinh ky thuat. Thdi gian nu6i/vu tir 4 thdng doi vdi m6 hinh TC va 4-6 thang d i i vd'i md hinh QCCT, TL.
+ Khao sat cac ehi tieu nhiet dp, pH, dp man, chit hiru CO, dam de phan huy (N-NH4''he), NH3, H2S, ghi nhan tinh trang: mau nude, s y phat triln, nang s u i t san lugng cua tdm nudi.
+ Thdi d i l m nghien ciru: miia khd va miia mua nam 2003, t i l n hdnh khao sat vao cac thang 12/2002, thang 3/2003, thang 6/2003, thang 9/2003 vd thang 12/2003, thang 8-12 nam 2007.
b. Dung eu thu mau, ky thuat thu mau
Dung cu thu m l u : Dung cu thu m l u duge thilt k l b i n g vien thoi khi ( h i ca) hlnh tru dai 6 cm, dudng kinh 4 cm, ben ngdai dugc bao kin mpt ldp t i m lpc nude ho ca, n i l dau vien thoi khi vdi 01 dau I n g nhya (loai diing cho djch truyin hoac t h i i khi h i ca) va dat vao d i l m e i n thu m l u nude, d i u edn lai cua ong nhya ed khda de cd the khda kin hoac md khi can. Moi d i l m dat 01 dung cu lay m i u ndi tren. Tong so diem thu mau/md hinh: 06 diem. Dgng cu nay eho phep l i y d u g c mau diing diem can khac sat, han c h l t i i da d u g c s y xam nhap eiia khdng khi vdo m l u vd s y pha trpn nude mau giu'a cac d i l m .
Thu mau: D i n thdi diem l i y mau diing I n g hiit chan khong riit bd h i t nude chira trong dung cu Ihu m i u , sau dd chd' khoang 15 phut thi t i l n hdnh lay m i u , thao tac nhanh.Cach thuc co djnh m l u , bao quan m i u thye hien theo hudng d i n cua Standard Methods 2005.
* Phwang phap phan tfch
+ pH : can lOg d i t pha vdi 25ml nude c i t theo ti
32 Tap chi Khi t\i<^ng Thuy van * Thang 4/2009
Nghien ciJu & Trao doi
le dlt:nudc la 1:2,5 do pH bang may Thermo Orion 420A va EC b i n g may WTW. , :
+ Dam hiru ca d l phan huy: Diing dung djch trfch KCI2M dun ndng d 100°C trong 4 gid (Gianello va Bremner, 1986). Dam NH4*-N d u g c phan tich theo phuang phap Kjeldahl ed them vao MgO d l tao mdi trudng k i l m . Dam NH4'"-N dugc xac djnh b i n g each ehuin dp vdi dung djch H2S04 0,0025M.
+ C h i t hiru ca trong biin day: xac djnh c h i t hiru ca trong d i t theo phuang phap Walkley-Black (Houba va ctv, 1988). Dya tren nguyen t i e oxy hda chit huu CO bing K2C1.2O7 trong mdi trudng H2SO4 dam dac, sau dd chuan dp lugng d u K2C1.2O7 bang FeS04.
+ C h i t hiru co trong nuac biin day, nude sat day va nude giu'a ao tdm: Phuang phap 5310 B.
High - temperature combustion Method, Standard Methods 2005
+ Nguyen ly xac djnh N-NH3: Phuang phap 4500 B. Flow Infection Analysis, Standard Methods 2005 • ^ « ' " • ^ " ' ' ' '•''
+ Nguyen ly xac djnh H2S: Phuang phap 4500-S2- J. Acid -Volatile Sulfide Standard Methods 2005. ^--y,l.:
Viec tfnh toan n i n g dp khf NH3 trong mdi trudng nude nude biin day va Idp nude sat day dugc thye hien dya tren tdi lieu tham khao : n i n g dp tong so NH3 (kit qua phan tfch tir phdng thi nghiem), nhiet dp vd pH tai thdi diem l i y m i u va b i n g phygng phap tra bang ndi suy. M i u d u g c phan tfch tai Phdng thf nghiem ciia Truo'ng Oai hpc C i n Tha. Xij ly s l lieu bang p h i n mem Excel, phan tfch tuang quan bang p h i n m i m : SPSS (Statistical Package for Social Sciences).
3. Ket qua va thao luan a. Tfnh chit dit thi nghiem
D i t phen hoat ddng sau man trung binh: Sj2M, t i n g phen hpat dpng x u l t hien trong khoang dp sau 50 -100 cm, khdng ed tang phen t i l m tang trong vdng dp sau 5 0 - 1 2 5 cm. D i t ed ham lugng cac
chat dinh dudng, miin, dam va kali kha cao; chua vira d i n it chua; ngheo lan va chira cae c h i t dpc:
S04^", Fe3'', AP'" va Cl" kha eao; tuy nhien cac tang cd tfch luy ddc c h i t x u l t hien sau (trong dp sau 50 - 100 em) va ed dp day tich luy mong (< 50 cm),
Dat phen t i l m tang nong, man nang (SpIMn), g i l u huu ca, dam va kali; d i t chua va cd lugng dpc to (SO42-, AP*, Fe^-^ va Cl") kha cao. T i n g phen hoat dpng (Bj) x u l t hien trong khoang dp sau 40 - 90 cm.
Phan irng d i t ehua vira den r i t ehua, ngay ea d t i n g d i t khdng phen gia trj v l dp ehua eung chi dat mire t h i p ( P H H 2 O : 5,21 - 5,48; pH^^ci: 4,55 - 4,99;
pH|_|202- 3,5 -4,0); d t i n g phen hoat dpng d i t r i t chua ( P H H 2 O : 4,09 - 4,83; p H ^ c i • 3.84 - 4,00;
P H H 2 0 2 - 2'5 - 3,5). Miin va dam tong s l trong t i n g dat mat kha giau (3,6 -4,4% OM va 0,21 - 0,28% N).
Cac doe c h i t trong d i t d mire kha cao, dac biet la d cac t i n g phen, sulphate hda tan (S04^') len d i n 0,28 - 0,32%, s i t hda tan (Fe^*): 10,27 -28,2 mg/IOOgd, nhom di dpng (AP*): 1,5 -5,5 me/IOOgd, lugng Ci- trong d i t cung len d i n 0,94 -1,20%.
D i t man trung binh, ky hieu: M. Dp ehua trong d i t dat g i n mire trung tfnh, t h i p han trong d i t man nang PHH2O ^9^ 6,6-7,94; PHKCI : 5,66-7,52; dp chua t i l m tang P H H 2 0 2 ^^^ 4,0 don vi pH. Miin va dam t i n g s l trung binh (1,194 - 3,552 % 0 M va 0,056 - 0,142% N). M i r c d d bao hda baza dat 60-65%. Cac dpc c h i t chu y l u la dp man va s i t hda tan d tang sau kha cao, tuy nhien tren dat mat lai t h i p ; lugng Cl" va s i t hda tan trong cac tang sau len d i n 0,4 - 0,5% Cl- va 8,6 -10,8 mg Fe'VIOOg dat, trong khi dd Idp d i t mat chi d i n 0,09% Cl- va 0,26 mgFe'VIOOg d i t . Loai d i t nay ed dp phi kha, dp dpc kha t h i p .
D i t man nang la Idp dat mat (ting Ap va Ab) day, x l p , g i l u hi>u ca; dinh dudng eao, miin, dam va kali giau; lan tong so vd de tieu t h i p ; d i t ft chua va ed dung lugng trao doi cation (CEC) kha cao. Miin va dam t i n g s l trung binh (0,797 - 2,4 % 0 M va 0,070 - 0,207% N). Dung lugng trao d i i cation kha, len d i n 18,6 -19,6 me/100g dat. Mire dp bao hda baza dat 70-80%, day la loai d i t cd dp bao hda baza cao
Tap chi Khi tuftfng Thuy van * Thang 4/2009 33
Nghidn ctfu & Trao dd'i
so vdi cae loai d i t trong tinh va Dong b i n g song ciru long (DBSCL). Cac dpc c h i t trong chii yeu Id dp man cao vd s i t hda tan kha cao, lugng Cl- trong d i t theo thir ty len d i n 0,40- 0,47% Cl", 9,80 -16,32 mg Fe'VIOOgdIt.
b. Nhiet dp, pH va dp man moi trwang nw&e
Dp man trung binh cdc thang tren cae md hinh thay d i i Idn theo miia, tir 4,73°/oo <Jen 32,4''/oo- Thang cd dp man thap nhat Id thang 9/2003 (4,730/00). ke t i l p la thang 12/2002 (9,870/oo), thang 12/2003 (14,20/00). thang 6/2003 (25,50/oo), va eao n h i t la thang 3/2003 (32,4°/oo). Nhiet dp trung binh nam trong khoang 28,6 - 31,8°C. Thang 3/2003 la thang cd nhiet dp trung binh cao n h i t 32°C, cue bd mdt s l thai d i l m dat tren 34°C, cdc thang: thang 6/2003: S0,90C, thang 12/2002: 29,60C, thang 12/2003: 29,40c vd thang 9/2003: 28,60C. Nhiet dp thich hgp eho s y phdt trien cua tdm nam trong khoang 26-300C .Thuc te eho t h i y vao thang 3 hang nam tdm c h i t nhilu tren dien rdng tren dja ban todn tinh Cd Mau. K i t qua khao sat pH cho t h i y n i m trong nguang phii hgp vd ehju dyng dugc ciia sy phat trien eiia tdm sii.
c. Cie yeu to anh hwang den nong dp N-NH^, H2S tren eae loai dat
1) Chit hu'U ca vd dam hiru ca de phan huy trong biin ddy
K i t qua phan tich chat h&u ea tren d i t Sj2M vd d i t SpIMn cao han nhilu so vdi d i t M, Mn. Nong
dp c h i t hu'U ca trung binh cua cdc md hinh tren dat Sj2M vd m i u d i t SpIMn tich luy theo thdi gian vd tang qua eae thang: trung binh thang 12/2002: Sj2M (7,81%), S p I M n (7,99%), Mn (3,2%), M (3,33%);
trung binh thang 3/2003 Id Sj2M (8,09%), S p I M n (8,22%), Mn (3,29%), M (3,29%) va thang 6 nam 2003 Sj2M (8,40%), S p I M n (10,6%), Mn (3,36%), M (3,71%). C h i t hu'U ca cae md hinh tren tang theo thdi gian (xem hinh 1).
Hinh 1. Ham lwang trung binh chat hu'U ca trong bim diy
Ghi chu:
DVK: diu vu miia khd ; ? ; • < ; "
GVK: giira vu miia khd .;. <•:
CVK-DVM: euii vu miia khd - diu vu miia mua
N i n g dp trung binh N-NH4*hc cua cac md hlnh nudi tdm d i u vu nudi thang 12/2002: Sj2M (18,2%), SpIMn (15,8%), Mn (3,31%), M (8,38%); vd cuoi vu nudi vao thang 6/2003: Sj2M (11,9%)), SpIMn (19,2%), Mn (6,11%), M (8,30%,); K i t qua eho thay n i n g dp dam huu ca de phan hiiy eua cac md hinh tren d i t eao han tren hai l l n so vd'i tren dat M, Mn (xem hlnh 2).
Hinh 2. Ham lwang trung binh N-NH/he trong bun day
34 Tap chi Khi tuftfng Thuy van * Thang 4/2009
/ ? .
Nghidn ctfu & Trao doi
7a'Si»:m*K^<s:sassf)si»!S2) Chdt hiru ca tren cdc vj tri muang, trang cua moi md hinh ; / •
K i t qiia khao sat c h i t hiru ea tren trang vd dudi muang ciia eae md hlnh cho thay khdng cd sy khac biet Idn giira trang vd muang. Ndng dp c h i t hu'U ea dat cao n h i t trong biin day, k l d i n la nude sat day va t h i p n h i t trong Idp nude each day 50 cm.
Trong md hlnh TC n i n g dp c h i t hCru ea thap n h i t
Bang 1. Nong dp chat hu'u ca tren trang
trpng biin day va Idp nude sat day so vdi hai mo hinh QCCT va TL. Tuy nhien, d Idp nude each day 50 cm vao thang 11, tom nudi dat hai thang tuoi, n i n g dp c h i t hu'u ca (27 ppm) eao han nhilu so vdi hai md hinh QCCT ( 1 5 , 7 - 1 7 , 9 ppm), TL (12,6 -18,9 ppm) hien tugng nay do thire an d u thira tfch Itiy la lirng trong nude cd t h i da lam tang n i n g dp chat hiru ca trong cot nude d md hlnh TC so vdi md hinh QCCT, TL (xem bang 1).
(T) va dw&i mwang (M) eua eie mo hinh
Mo hinh thi nghiem
Thang Tu6i t6m QCCT-M
QCCT-T TL-M
TL-T TC
Vi tri
M T M T
Biin day
T8
to
93,8 84,8 112 112 75,6
T9 t l 149 119 120 174 38,1
T H t3 27,1 27,1 109 18,0 73,0
Sat day
T8
to
21,3 26,2 37,3 27,3 31,9
T9 tl 35,2 39,1 42,6 39,0 37,0
T H t3 17,7 16,8 17,7 15,0 41,7
Cach day 50 cm
T8
to
25,0 21,0 27,7 31,7 27,9
T9 tl 30,3 37,3 36,2 37,6 33,6
T i l t3 17,9 15,7 18,9 12,6 27,0
d. Nong dp N-NH^, (H2S) trong moi trw&ng ao tom
1) Nong dp N-NH3, H2S cua md hinh QCCT tren dit Sj2M, SpIMn, M vd Mn
Ning dp trung binh N-NH3 eua cac md hlnh nuoi tdm QCCT tren 4 loai d i t dugc tim t h i y nhu sau:
Sj2M (0,016 ppm), SpIMn (0,033 ppm), Mn (0,013 ppm) vd M (0,019 ppm). K i t qua khao sat eho thay nong dp N-NH3 ghi nhan dugc d cac thdi diem khao sat tren d i t Sj2M vd SpIMn ed phan eao han tren d i t Mn va M, tuy nhien, cac gia trj thu duge d i u t h i p han gidi han cho phep (<0,1 ppm), khong lam anh hudng xau d i n sire khde tdm nudi. D i l n bien n i n g dp ammonia tang vao c u l i vu tdm mua khd (thang 6) va vao giira vu mua mua (thang 9). N i n g dp N-NH3 trung binh va cao nhit, tai eae thdi diem khao sat d cac md hlnh tren eae loai dat; Sj2M (0,005 - 0,025 ppm) cao n h i t la 0,025 ppm vao thang 6, c u l i vu tdm; Spl Mn (0,014 - 0,065 ppm), cao nhat vao cuoi miia vu tdm nudi miia khd (0,065 ppm); tren d i t Mn, M nong dp trung binh ammonia r i t t h i p so vdi tren d i t Sj2M va SpIMn, Mn n i m trong khoang (0,002 - 0,024 ppm), tang eao vao thang 6 c u l i vu miia khd
(0,015 ppm), dat cao nhat vdo giu'a vu miia mua (0,024 ppm); tren dat M (0,005 - 0,029 ppm), cao n h i t 0,029 ppm vao giira vu miia mua.
Ndng dp trung binh H2S cua cac md hinh nudi tdm QCCT tren 4 loai d i t d u g c tim t h i y nhu sau:
Sj2M (0,053 ppm), S p I M n (0,030 ppm), Mn (0,024 ppm) va M (0,016 ppm). K i t qua khao sat cho t h i y n i n g dp H2S ghi nhan dugc d cae thdi d i l m khao sat tren d i t Sj2M vd S p l Mn cao han so vdi tren d i t Mn vd M, vugt gidi tian eho phep (0 ppm), lam anh hudng x l u d i n sire khde torn nudi. Dien b i l n nong dp hydrogensulfide tang vdo c u l i vu tdm miia kho va vao giira vu mua mua. Ndng dp H2S trung binh vd cao n h i t , tgi cac thdi diem khao sat d cac md hlnh tren cae loai d i t : Sj2M (0,010 - 0,101 ppm) cao n h i t la 0,101 ppm vao thang S, giira vu tdm miia khd; Spl Mn (0,004 - 0,049 ppm), cap nhat vao giiia miia vu tdm miia mua (0,049 ppm); tren dat Mn, M n i n g dp trung binh H2S r i t t h i p so vdi tren d i t Sj2M va S p I M n , Mn nam trong khoang (0,004 - 0,050 ppm), dat cao nhat vdo giu'a vu miia mua (0,031 ppm); tren d i t M (0,011 - 0,023 ppm), eao n h i t
Tap chi Khi tiTgTng Thuy van * Thang 4/2009 35
Nghien cuTu & Trao doi
0,023 ppm vao giira vu miia mua.
Nhin chung s u hien dien H2S d cae md hlnh cd the da lam thiet hai tom nuoi, kiem tra ao tdm cho thay tdm c h i t nhilu vao thdi d i l m 1-2 thang tuoi, tuang irng vdi cac thdi diem thang 3, thang 6, thang 9. K i t qiia thu hoach cung chi ra r i n g ty le torn s i n g d i n c u l i vu nam trong khoang (6,5 - 1 7 , 3 5 %), t h i p nhat khoang 6,5% tren dat Sj2M va 10% tren d i t SpIMn, tren d i t Mn dat 13-17% va dat M khoang 11,3 - 16%. D i l u nay d i n d i n nang s u i t tdm nudi tren d i t Sj2M va SpIMn t h i p han rat nhilu so vdi
tren d i t Mn va M, tuang irng: 66 - 74 kg/ha/vu, 88 - 124 kg/ha/vu so vdi 149 -197 kg/ha/vu vd 152 -
188 kg/ha/vu.
Nong dp N-NH3 va H2S tren dat Sj2M, S p I M n cao han tren dat Mn, M cd the do n i n g dp c h i t hiru ca, ham lugng dam de phan hiiy cao tren d i t Sj2M, S p I M n q u y l t djnh, ngodi ra cac viing d i t Sj2M, SpIMn thudng t h i p , triing va khd tieu thdat nude han cac viing dat Mn vd M, cang lam cho y l u t l n i n g dp c h i t hu'u ca, ham lugng dam de phan hiiy trd nen quan trpng.
, 0,120 1 0 , 1 0 0 , | 8,ose
I 0,0m
| . 0,040 . 1 0,020 0,000
7^S5
DVK IJVK
NHI
©VM CVAI es+< SM<
fiVM H 2 i
SVM CVM
• * - S ) 2 M - * - Spain -»-Mn
Ciiiti«ull-IIH} v.^ Hmxii «.M fl><>i<n«in
Hinh 3. Nong dp trung binh ciia N-NHj, H2S eua eie mo hinh
Ghi chii: DVK: dau vu miia khd; GVK: giiJ'a vu miia khd; CVK-DVM: euii vu miia khd - ddu vu mua mua;
GVM: giira vu miia mua; CVM: cuoi vu miia mua
2) Ndng dp N-NH3, H2S tren trang vd muang cua cdc md hinh TL, QCCT vd TC tren dat Sj2M
Nong dp trung binh N-NH3, trong biin day dudi muong cua cac md hlnh cao han tren trang. Trong biin day md hinh QCCT (0,075 - 0,983 ppm), md hlnh TL (0,033 - 0,459 ppm), mo hlnh TC (0,048 - 0,714 ppm), tuong irng tren trang la: md hlnh QCCT (0,005 -0,345 ppm), TL (0,054 - 0,294 ppm). Nhin chung nong dp trung binh N-NH3, trong biin day eiia cac md hinh d i u cao han n i n g dp gidi han cho phep (<0,1 ppm). Nong dp N-NH3, trung binh trong ldp nude sat day t h i p han r i t n h i l u so vdi tong biin day, h i u h i t cac k i t qua khao sat dugc d i u t h i p hon ngudng cho phep (<0,1 ppm), chi ed hai gia trj khao sat dugc tren trang vao thang 10 cua md hinh QCCT (0,338 ppm) va thang 9 ciia md hlnh TL (0,116 ppm) vugt gidi han cho phep. So vdi N-NH3, n i n g dp trung binh ciia H2S b i l n thien r i t Idn qua eae d i l m va dgt khao sat, trong biin day dudi muang va tren trang n i n g dp trung binh H2S ciia
cac mo hinh tuang irng: QCCT (0,063 - 20,6 ppm), QCCT (0,295 - 67,3 ppm); TL (1,21 - 32,5 ppm), TL (0,133 - 232 ppm) thien r i t Idn so vdi md hlnh TC (0,409 - 3,62 ppm). Trong Idp nude sat day, ning dp trung binh cua H2S cung kha eao d ca dudi muang va tren trang, tuong irng la: QCCT (0 - 3,48 ppm), QCCT (0 - 10,6 ppm) vd TL (0 - 1,35 ppm), TL (0 - 2,73 ppm), xem bang 2. N i n g dp trung binh cua /\/-NH3 vd Hydrogen cao trong biin ddy d md hinh QCCT, TL Id do viec cai tao biin day ao khdng triet d l , Idp biin day tren SO cm tir vu trudc da khong dugc nao vet h i t ra khdi ao nudi. Mat khac do khdng kiem soat dugc mdi trudng nudi, tao phat trien biing phat r i i tan qua n h i l u dgt da tang cudng chat hCru ca vao ao nudi lam xuc t i l n qua trinh khir sulfate vd phan giai y I m khi d i n d i n tang lugng N-NH3. Viee sir dung djnh ky Zeolite hang thang da ed tae dung h i p thu vd khir khf N-NH3, sinh ra trong ao nudi, lam giam t h i p lugng N-NH3, so vdi H2S. Ham lugng H2S cao ed the da lam thiet hgi tom nudi, k i t qua
36 Tap chi Klu tiTt/ng Thuy van * Thang 4/2009
A>.
Nghien cii'u & Trao doi
quan sat hang ngay eho t h i y tdm trong ao nuoi chet rai rac khi dat 1 thang tuoi vd tang d i n thdi diem tir hai thang tuoi. Ty le tdm s i n g d i n thdi d i l m thu hpach ciia hai md hlnh QCCT va TL dat t h i p han
10%, nhung d md hlnh TC dat tren 70% dan d i n nang s u i t tdm nudi d hai md hinh QCCT (69 kg/ha/vu), TL (88 kg/ha/vu) dat t h i p trong khi dd md hlnh TC cd nang s u i t dat 1,5 tin/ha/vu.
Bang 2. Kit qua nong dp trung binh N-NHj, H2S
Dtft khao sat
8/2007
9/2007
10/2007
11/2007
12/2007
Md hlnh
QCCT TL TC QCCT
TL TC QCCT
TL TC QCCT
TL TC QCCT
TL TC
N-NH3 (ppm)
Biln day- M
0,323 0,245 0,265 0,983 0,307 0,048 0,360 0,459 0,714 0,075 0,038 0,229 0,260 0,033 0,483
Ntfdc s^t day M
0,060 0,041 0,083 0,057 0,064 0,077 0,077 0,087 0,070 0,017 0,016 0,032 0,065 0,015 0,068
Biln di.y T 0,345 0,176 0,031 0,054 0,338 0,294 0,005 0,066 0,027
Ntfdc s^t day T 0,051 0,058 0,067 0,116 0,338 0,063 0,011 0,022 0,034
HzS (ppm)
Biln d^y M 0,063
1,21 3,62 20,6 3?, 5 0,927 7,36 9,45 0,409
5,27 5,20 1,57 0,68 1,77 1,00
Ntfdc s i t day M
0,000 0,793 1,35 0,471 0,676 2,56 3,48 1,35 0,320
0,00 0,00 1,07 0,00 0,354 0,631
Bun diy T 0,295 0,133 67,3
232 10,6 6,67 16,5 7,75 1,20
Ntfdc sat diy
T 0,156 0,000 0,534 0,666 10,6 2,73 0,00 0,00 0,00
Phan tich tuong quan anh hudng cua cac chi tieu qua cdc thang trong tirng md hinh cho t h i y ning dp N-NH3, H2S ed lien quan d i n c h i t hiru ca (TOC), k i t qua tuong quan nhu sau:
- Ldp nude sat day trong md hinh TC [H2S] = -9,382 + 0,339[TOC] - 0,031 [Fe^*]
- Ldp nude sat day trong mo hinh QCCT [N_NH3] = - 23,221 + 1.264 [TOC]
4. Ket luan va de nghj a. Kit luan
- Ham lugng c h i t hiru eg va dam hu'u ca de phan huy trong dat, biin day ao d cac md hlnh nudi tdm sii QCCT tren d i t Sj2M, SpIMn cao han tren d i t M, Mn.
- Ning dp hydrogensulfide trong nude d eae md hinh nudi tdm sii tren d i t Sj2M, Spl Mn cao hon tren
d i t M va Mn. N i n g dp N-NH3, H2S cao vao cac thdi diem thang 3, thang 6, thang 9 eua miia vu nudi, tuang irng vdi thdi d i l m tdm duge 1-2 thang tuoi.
- Trong cae md hlnh nudi tdm sii QCCT, TL va TC nong dp N-NH3 va H2S trong biin day cao g i p hang chuc d i n hang tram l l n so vdi trong Idp nude phia tren ciia ao nudi.
- N i n g dp N-NH3, H2S trong biin day, Idp nude sat day tai cac diem, dgt khao sat tren trang va dudi muang cua ao nudi tdm d cac md hinh QCCT vd TL cao hon va b i l n thien Idn han so vdi md hinh TC.
Ky thuat nudi vd d i u t u q u y l t djnh ham lugng N-NH3, H2S hien dien trong mdi trudng ao nudi.
- Ty le tdm song d cac md hlnh QCCT, TL dat nhd han 20%), trong khi dd d" md hinh TC ty le tom s i n g dat tren 70%, d i n d i n nang s u i t torn nudi d eae md hlnh QCCT, TL dat t h i p han r i t nhieu so vdi md hlnh TC.
Tap chi Khi tiTgfng Thuy van * Thang 4/2009 37
Nghidn cuTu & Trao ddi
/?•b. Kien nghi
- Tang cudng cac bien phap ky thuat thfch hgp d l khoang hda triet d l c h i t hiiu co trong biin day, hoae sen vet sach biin day ao sau moi vu nudi.
- K i l m scat thanh phan dinh duang Nita, P h i t pho trong mdi trudng nude ao nudi nham han c h l sy biing phat ciia tao, vd han c h l t i i da hien tugng tao tan. K i l m soat lugng thire an dua vao ao nuoi.
han c h l toi da viee tich luy thire an d u thira trong ao nu6i. Tang cudng trao doi nude, cai thien e h l dp oxy hda tan vao day ao.
- T i l p tue nghien eiru d l lam rd them qua trinh phat sinh va phat tan N-NH3, H2S tir biin day ao vdo n g u i n nude ao nudi. Nghien eiru cac giai phap ky thuat hiru hieu cd hieu qua kinh t l d l khir triet d l n i n g dp N-NH3, H2S trong mdi trudng ao nudi.
Tai lieu tham khao
1. Cao Phuang Nam, Le Quang Tri, Vd Thj Guang, Nguyen Thanh Cdn, Bui Ddc Tuan vd Truang Quoc Phil. 2005. Bdo edo ting kit di tdi: Bude dau ddnh gia tinh bin vu'ng cua cae md hinh san xudt vung ehuyin dii tinh Cd Mau, di xudt cdc giai phdp phdt triin bin vu'ng cho giai doan 2005-2010. Sa Khoa hoc vd Cdng nghe tinh Cd Mau, 180 trang.
2. Trudng Dai hoe Can Tha- Khoa Thuy san. 2002. Gido trinh cao hgc Quan ly chat lugng nirdc nudi tring thuy san.
3. Fao. 1986. Shrimp Culture: Pond design, operation and managenent.
http://www. fao. org/docrep/fleld/003/A C210E/A C210E09.htmch9.
4. FAO. 1987. Site Selection for Aquaeulture:Chemlcal features of water. Fao library flehe an: 287785.
UNDP programme fao of the United Nations Nigerian Institute for oceanography and marine researchprojeet raf/82/009. http://www.fao.org/docrep/field/003/AC175E/AC175E20.htm
