JMR-2017v7n17 - page 9

Journal of Mosquito Research 2017, Vol.7, No.17, 134-141
137
(P>0.05) among the rice fields subjected to different agricultural chemical inputs. The mean temperatures however,
ranged from 30.00±0.00 to 30.50±0.00
o
C, while DO and BOD were 6.00±0.00 to 7.00±1.41 mg/l and 4.00±0.00
to 4.50±0.71 mg/l, respectively. On the other hand, Turbidity, Nitrate and Chloride were significantly (P<0.05)
higher in site A (rice-fields without agrochemical inputs), where they ranged as follows: 0.27±0.24 to 0.24±0.18
NTU, 9.92±1.94 to 7.72±2.23 mg/l and 31.45±15.00 to 23.41±15.00 mg/l, respectively. The distribution of the
concentrations of chloride among the sites followed the same trend, been significantly highest in site A (mean =
31.45±03 mg/l). Alkalinity, Hardness, Sodium and Conductivity were highest in site B (rice field with only
chemical fertilizer application) (means = 132.00±19.79 mg/l, 81.00±41.01 mg/l, 51.70±1.41 mg/l and
508.58±44.54 µS/cm, respectively) and least in site C (rice field with both fertilizer and herbicide) (means
=31.00±15.56 mg/l, 32.00±14.14 mg/l, 38.15±2.75 mg/l and 194.00±43.84 µS/cm, respectively). The
concentration of Potassium was significantly lowest in site A (10.40+0.14 mg/l) and did not significantly differ
between sites B and C (14.40+0.14 mg/l and 13.40+3.11 mg/l, respectively).
Table 1 Variation in physicochemical properties of rice-field mosquito larval habitats subjected to various agricultural chemical
inputs in Minna, Nigeria
PHYSICO-CHEMICAL PARAMETERS
Site A
Site B
Site C
Temperature (
o
C)
30.50±0.71
a
30.00±0.00
a
30.00±1.41
a
pH
6.57±0.51
a
7.17±1.48
b
6.16±0.11
a
Turbidity (NTU)
0.27±0.35
b
0.24±0.28
a
0.24±0.21
a
Conductivity (µS/cm)
344.50±61.51
b
508.50±44.54
c
194.00±43.84
a
Alkalinity (mg/l)
75.00±21.21
b
132.00±19.79
c
31.00±15.56
a
Hardness (mg/l)
62.00±19.79
b
81.00±41.01
c
32.00±14.14
a
Potassium (mg/l)
10.40±0.14
a
14.90±2.12
b
13.40±3.11
b
Sodium (mg/l)
47.75±2.33
b
51.70±1.41
c
38.15±2.75
a
Phosphate (mg/l)
5.58±2.69
b
2.71±1.77
a
9.98±1.69
c
Nitrate (mg/l)
9.92±1.94
b
7.93±3.18
a
7.72±2.23
a
Chloride (mg/l)
31.45±4.03
c
27.47±0.49
b
23.41±15.03
a
D.O (mg/l)
7.00±1.41
a
6.00±0.00
a
6.00±2.83
a
B.O.D (mg/l)
4.50±0.71
a
4.00±0.00
a
4.50±2.12
a
Note: * Mean values followed by the same superscript alphabets in a row are not significantly different at P = 0.05; Site A: rice-field
without agrochemical application; Site B: rice field with only chemical fertilizer application and Site C: rice-field with both fertilizer
and herbicide application; * Dissolved Oxygen (DO) and Biological Oxygen Demand (BOD)
2.2 Relationships within the physicochemical conditions
Table 2 shows the relationships that exist between the physicochemical parameters, in which some were
significantly correlated while others were not. Significant positive correlation among the physicochemical
parameters include those between Chloride and Temperature (r=0.95), Conductivity and pH (r=0.96), Alkalinity
and pH (r=0.93), Sodium and pH (r=0.89), Alkalinity and Conductivity (r=0.96), Sodium and Alkalinity (r=0.88),
DO and Nitrates (r=0.92), DO and Chloride (r=0.76), DO and BOD (r=0.94). On the other hand significant
negative correlation also exist among the following parameters Phosphate and pH (r= -0.92), Phosphate and
Conductivity (r= -0.97), Phosphate and Alkalinity (r= -0.97), phosphate and Sodium (r= -0.91). Potassium
distinctly showed a negative correlation between sodium, Phosphate, Chloride, DO and BOD.
3 Discussions
The results of this study showed that water temperature, Dissolved Oxygen (DO) and Biochemical Oxygen
Demand (BOD) were not significantly affected by agrochemical inputs in the rice-field larval habitats. The
temperatures recorded in this study were considerably lower than the 40.00
o
C maximum limit for the thriving of
aquatic organisms by Federal Environmental Protection Agency (FEPA, 1990). This may be due to the fact that
water temperature is generally dictated by atmospheric temperature, as influenced by the amount of absorbed solar
radiation (Kemker, 2014). The conductive water temperature in Minna rice-fields may mean that such habitats are
active vector-mosquito production sites, with its attendant public health implications in the area. According to
Kawo et al. (2004) low water temperatures eliminate thermal pollution in aquatic habitats and promote the
thriving of invertebrates.
1,2,3,4,5,6,7,8 10-11,12,13,14,15,16
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