KHOA SINH
RAU
LOAN,
-
KHOA SINH
h.
nh
Đà Nẵng, ngày 5 tháng 5 năm 2015
1
1
2
2
2
2
2
. 3
3
3
3.1.2. H 37
3.1.3. 39
42
4.1. 42
42
43
1. BNN
2. QCVN
3.
4. TCCP
5. TCVN
u
.
ng.
nhanh .
TP. 2
2.
2.1.
TP.
2.2.
-
-
- .
g
- Nam
N
-
79,84%
-ma, gra-phit
.
m
4
n.
-
theo
-
1.1.4.
013Vang
73.691 ha [19].
ha. chim 7,6% [19].
6
t.
1.2. VAI SINH TR V PHT TRIN
C
ng c h n a cc vi khun sg trong cy, cc o c v cc vi
khun ng sinh trong r ca mt s loi thc . Mc p thu nhu
hoc nitrat
ca cy trng ph thuc vo ti, li cy trg, mi trng
v cc u t khc. Mt s li rau nh bp c, c ci s dg c c
amonium v nitrat
nhng ci xon, cn ty, b cc loi u sinh trng tt
hn khi cung cp n dg NO, cc li y nh c chua, khoai ty i
thh hp mi trng dinh dng c t lN-NO
3
/N-NH
4
cao. Nhit cg
nh hng t ln n vic p thu nitrat
hn amoniac, c bit nht
2-
16
o
C.
1.4.
nitrat
nitrat
n nitrat .
ngi c bit tr em do nitrat
c ch y trong bmy u ho c kh
ng khthh nitrit. Trong d dy con ngi, do c dg a h vi sinh
vt, cc loi enzym v do c qu h ho sinh m nitrit
d dng c dng
vi cc acid amin tdo to thnh Nitrosamine gy nn ung th, c bit
ung thd dy.
1
http://nioeh.org.vn/nitrat_anh_huong_cua_nitrat_den_suc_khoe
9
1.5. NHNG Y G TN D NITRAT
TRONG
1.5.1. ng
nitrat trong rau
Theo cc nh khoa c th c yu t gy tn d nitrat trong ng
n nh nht , h sng, t i, nc ti, bin php canh c nhng
nguyn nhn ch yu c c nh nng hc kng h lpn bn c
bit l phn n. Hm lng nitrat trong ra mc m l do n
qu liu , bn khg ng ch. Gim lng n s lm m s
pn n kng hp l nguyn nhn dn n hm lng nitrat cao
trong n pm.
Ngi c s ng mt lng ln phn n th thi gian kt thc bn
n trc thu hch cng lmt n tng t ph b tt c cc vng
trg rau trong c nc. Nng n thng thu hch rau ch sau khi n
n 3-7 ngy [3]. Ngi n xut hu nh khng quan tm n tn d
nitrat trong rau m thi gian thu hoch do th trng qut , c bit
vo ma khan him rau. Nhiu t qu nghin cu chng minh ng,
tn d nitrat trong rau lin quan cht chti s cung cp n v qutrnh
quang hp trc lc thu hoch. Nu c thi gian v iu n cy
quang hp mnh to ra glucid v h hp to ra axetoacid thhm lng nitrat
trong cy khg n mc gy c. Do thi gian bn n trc khi thu
hoh qt nh n tn d trong rau. Tuy y kh ng p th
v ch lu nitrat
nhanh hay cm n ph thuc vo tng li rau. Hu
ht cc li rau c hm lng nitrat
t cao nt sau khi bn thc n n
cui t 10 ngy. Hm lng nitrat ci bp t cao nht o ny
th 7 k t khi bn tc ln cu t c cc u lng n khc nhau v
ch thu hoh sau 14 ngy th hm lng nitrat trong ci bp mi gim hn
di ngng an tn [12]. Tn d nitrat trong rau n l v rau n qu cao
nht trong khog thi gian t 10 15 ny lc bn ln cui n khi
thu hch, i vi rau n c l khng 20 n. Thi gian bn thc sau
ng cng xa ngy thu hoh th lng nitrat trong rau cng gim.
Khi nghin cu nh hng ca thi gian n thc n n cui i vi
mt s li rau trng h Lm g, c gBi Cch Tuyn (1998) [26]
cho bi i vi x lch tn d nitrat t cao nht khng 21 y khi ngng
trong rau, nhit quln gy tr ngi cho qu trh kh nitrat r
nn m lng nitrat
trong rau s cao [31].
1.5.3. nh hng ca t trg, n t mc h lu
nitrat trong rau
Mi trng , nc lun lni p nn c ngn thi. i nhng
vng sn xut nng nghip mi trng t, nc chu h hng rt
ln ca qu trh t mi trng theo ng tun hon
s i o nng sn. Cc ngn cu nc ngoi vi vic s dng
ngn t nit h du chra ng n pn n c hthg v ln hn
200 kg N/ha c nh hng n vg n hon n trong sinh thi ng
rng: nitrat ho dn ti ra tri nitrat m nhim ngun nc m, nc
12
ngm khi c nng N-NO
3
> 10 mg/l [17]. Trong iu kin m kh
n phn n ng nitrat
cho t la
ngp nc c th xy ra qu trnh
phn nitrat ho (denitrification) gy mt n v lm gia ng thh phn kh
nh h (N
2
O) n y ma axit [32].
Trong ng trng rau, t thog k, m thh hp cho quh
xy ho, nitrat c hh thnh, rau d p thu. S hp thu n dng nitrat
rt t trong t nh phc h keo t, h ct ny lm cho nitrat
linh ng
di chuyn su hn v nh hng n ngun nc ngm [18]. Trong c loi
rau, lng nc cha t 90% tr ln do y cht lng nc ti nh
hng trc p n cht lng sn phm. Sng h ngun tim ng
c cht c hi trong c nitrat
nhng c ngi nng n s dg
13
hg ny ti cho rau v hu qu t yu l chng sn c ch lu
trong [2].
1.6.
[14]
nitrat
p
n
ng nitrat tro
19-55 --67 -50
n ng nitrat trong
c v
-2013, -5/2013 [27]. K
ng nitrat
trong rau x 748,1
ng nitrat
ng nitrat
N
[37]
15
, khoai
Anjana [30] trong
trong th
DU Shao-ting
(2007) [39]
mg/kg Theo Surendra Prasad
(2008) [36]
.