Education of the republic of uzbekistan tashkent state technical university named after islam karimov

№3/2021 year. 
Technical science and innovation
76
0
50
100
150
200
250
Conce
ntr
atio
n, 
pp
m
Sample5
Cu
Zn
Ga
As 
Se
Br
Rb
Sr
Y
Zr
Nb
Mo
Ag 
Cd 
In
0
50
100
150
200
250
Conce
ntr
atio
n, 
pp
m
Sample6
Cu
Zn
Ga
As 
Se
Br
Rb
Sr
Y
Zr
Nb
Mo
Ag 
Cd 
In
0
50
100
150
200
250
Conce
ntr
atio
n, 
pp
m
Sample7
Cu
Zn
Ga
As 
Se
Br
Rb
Sr
Y
Zr
Nb
Mo
Ag 
Cd 
In
0
20
40
60
80
100
120
30
40
50
60
70
80
90
100
110
Сa2+
SO
2- 4
0
20
40
60
80
100
120
NO
- 3
Fig.2. Volume weighted mean concentrations of major ions (μeq l−1) and possibility of 
NH
4-
 , SO
42 
, 
-
NO
3-
 ions for seven regions in rainwater collected 
 
Preliminary comparative analysis of data showed, that contents of alkali (K, Na) and earth alkali 
(Mg, Ca) are on the high level as in the other. In literature this type of concentration of alkaline 
and earth alkaline elements explained that Main reason of contents heavy metal is linked to the 
presence of Cd, Cr, Cu, Ni, Pb, and Zn in street dust, which consists of mineral and organic 
particles originating from the soil, industrial emitters, motor vehicles, and fuel consumption [15]. 
Presence of NH
4
-
, SO
4
2-
NO
3
-
ions in studied samples varied 1.5-3.0 μeq l−l, 54.0-158.0 μeq l−l 

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Civil and environmental engineering
77 
and 1.0-6.0 μeq l−l respectively. The quantities of major ions in rainwater were compared with 
those reported in other urban areas (Table 1). The comparison dates showed that the 
concentration of heavy metals are higher than Kazakhstan and lower than Kirgisistan [16,17,18]. 
Table 1. Comparison of heavy metals in fractions (μg l−l) in rainwater between Tashkent and 
other locations 
Countries 
Heavy metals in rainwater 
Pb 
Cu 
As 
Cd 
Almaty 
(Kazakhstan) 
0–30.2 
1.7–32.5 
0–1.3 
0–2.1 
Balhash 
(Kyrgisistan) 
18.66–3.44 
30.4–8.54 
2.73 – 24. 25 
1.66 и 2.68 
Tashkent 
(Uzbekistan) 
8.0-12.0 
3.0-17.00 
7.0-8.0 
0.82-1.62 
The reason of accumulation of these contaminants possibly because of the combined emissions 
of industries and mobile sources in the Metropolitan Zone of Tashkent and agricultural activities 
near Tashkent (Fig.2). Soluble metal ions such as Na
+
and K
+
varied 23-204 μeq l−l and 4.0-8.0 
μeq l−l respectively. pH value showed neutral medium 7.0-7.3 which close to distilled water. 
The rain water at all the places except near the industrial source was not acidic and was 
characterized by the presence of excess cations, particularly Ca. The acid rain near the industrial 
source was associated with excess anions, especially sulphate. The difference between the 
cations and anions was inversely proportional to the H
+
ion concentration [19]. 
CONCLUSION. 
The concentrations of heavy metals and the total organic impurities in 
rainwater samples were determined in the Tashkent city on February and March. The pH value 
of except samples 5,6 ranged from 7.0 to 7.3 the showing higher alkalinity which may be due to 
suspension of particles in the atmosphere which is rich in carbonates and bicarbonates of calcium 
buffers the acidity generated by mineral acid [20].
Samples 5 and 6 deferred from other samples 
with low value pH 5-5,3 which showed acidic medium in rainwater studied areas. Literature 
suggests that if the source is influenced by anthropogenic activities, the nature of rainwater 
becomes acidic because anthropogenic activities contribute acidic gases like SO
2
and NO 
x
and a 
basic gas like NH
3
. When these acidic gases are dissolved in clouds, sulphuric and nitric acids 
are formed, respectively [21].
 
The concentration of heavy metals were specific for samples. Areas with high traffic and close to 
industries showed more quantities than others. 
References 
[1]
S V, Lakshminarayana & Sathian, K & Ravikumar, B. (2017). Rainwater Purification. 
Trends in Biosciences 10 (2), 541-548 
[2]
Zhang Guozhen et al. / Energy Procedia 5 (2011) 307–313 
[3]
Riffat Shaheed, Wan Hanna Melini Wan Mohtar, Ahmed El-Shafie,Ensuring water 
security by utilizing roof-harvested rainwater and lake water treated with a low-cost 
integrated adsorption-filtration system, Water Science and Engineering, Volume 10, Issue 
2, 2017,Pages 115-124,ISSN 1674-2370,https://doi.org/10.1016/j.wse.2017.05.002. 

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