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Energy and Earth Science 
Vol. 2, No. 1, 2019 

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ISSN 2578-1359 (Print)   ISSN 2578-1367 (Online) 

15 
 

Original Paper 

Ammonia Nitrogen Pollution Characteristics of Natural Rainfall 

in Urban Business District in Southern China: A Case Study of 

Chengdu City 

Xintuo Chen1, 2, Yiyao Wang1, Chengyue Lai1, 2, Jia She1, 3, Ke Zhong1, 4, Jiayang Chen5, Zhaoli Wang1* 

1 Institute of Water Environment Research, Chengdu Research Academy of Environmental Protection 

Science, Chengdu, China 
2 Environmental Monitoring and Analysis Laboratory, Chengdu Research Academy of Environmental 

Protection Science, Chengdu, China 
3 Institute of Drinking Water Safety, Chengdu Research Academy of Environmental Protection Science, 

Chengdu, China 
4 Institute of Watershed Research, Chengdu Research Academy of Environmental Protection Science, 

Chengdu, China 
5 Chengdu Experimental Primary School, Chengdu, China 
*Zhaoli Wang, E-mail: 9755014@qq.com 

 

Received: March 28, 2019   Accepted: April 12, 2019   Online Published: April 23, 2019 

doi:10.22158/ees.v2n1p15         URL: http://dx.doi.org/10.22158/ees.v2n1p15 

 

Abstract 

Chengdu city was chosen as the representative of southern cities in China in this work, characteristics 

of ammonia nitrogen (NH3-N) pollution in natural rainfall were analyzed by measuring the 

concentration in 15 natural rainfalls from April to September in 2017. The influence of ammonia 

emission from toilet vent of building on NH3-N pollution in rainfall was investigated, and the variation 

of total NH3-N pollutants and its influencing factors were expounded. The results showed that the 

average concentration of NH3-N in first rainfall was the highest, reaching 18.2mg/L, the average 

concentration of NH3-N in the subsequent 14 rainfalls was between 2.0 and 5.0mg/L, which is higher 

than Grade V (≤2mg/L) of Environmental Quality Standards of Surface Water (GB 3838-2002), and 

was an important source of NH3-N pollution in water. The concentration of NH3-N in natural rainfalls 

decreased with the increase of the distance between the sampling point and the toilet vent, indicating 

that the ammonia discharged from toilet exhaust is a major source of NH3-N pollution in urban 

atmosphere. The main factors affecting total NH3-N pollutants in natural precipitation include rainfall 



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intensity, rainfall duration and drought days. The total amount of NH3-N pollutants in surface runoff is 

less than that in natural rainfall. 

Keywords 

southern city in China, natural rainfall, ammonia nitrogen pollution, total pollutant amount, pollution 

characteristics 

 

1. Introduction 

Rainfall is a natural way to clean the atmosphere (Wang & Xu, 2009), so the air pollutants are an 

important source of pollution in rainwater. At present, the air pollution in cities of China has turned to 

the complex air pollution formed by fine particulate matter (PM2.5) and polluted gases (O3, SOx, NOx, 

NH3) (Cao, 2014; Samen J M et al., 2000; Gao, 2012). Some researches (Ge et al., 2015)pointed out 

that water-soluble inorganic ions (WSII) like SOx, NOx and NH3 are important chemical components of 

PM2.5, secondary water-soluble inorganic ions like SO4
2-, NO3

-, NH4
+ are the most important chemical 

species in the process of regional particulate matter pollution. Among them, (NH4)2SO4 and NH4NO3 

formed by reaction of the secondary pollutants such as sulfuric acid or nitric acid with NH3 have 

become the main water-soluble secondary pollutants in the atmosphere; Yang (Yang et al., 2007) 

observed atmospheric aerosols in Jinan city and found that secondary ions in PM2.5 mainly exist in the 

form of (NH4)2SO4 and NH4NO3, nitrogen deposition has been taken into account as an important 

nitrogen source in the study of nitrogen cycle in river basins; Huang (Huang et al., 2016) studied 

nitrogen deposition in Huanghuai Plain from May 2008 to April 2012. It was found that NH3-N was the 

main type of nitrogen deposition and the proportion of NH3-N in nitrogen deposition was 6%-79%, 

with an average of 53%; Zhu (Zhu et al., 2015) considered 41 ecological research sites in China, and 

found that particulate nitrogen, ammonia nitrogen and nitrate nitrogen accounted for 24%, 40% and 

33% of total nitrogen, respectively, indicating that ammonia nitrogen was the main component of 

atmospheric deposition; Zheng (Ge et al., 2017) studied three ammonia-rich areas in Korea, and found 

that, (NH4)2SO4 and NH4NO3 were the main forms of water-soluble ions in PM2.5; The atmospheric 

(NH4)2SO4 and NH4NO3 can enter urban water body through rainfall, becoming an important source of 

NH3-N in water body, aggravating water eutrophication and destroying water ecosystem balance (Ding 

et al., 2007; Neal et al., 2006); Wang Jin jie (Wang et al., 2014) carried out a 1-year study on nitrogen 

wet deposition in Jinshui River Basin. It was found that the concentration of total nitrogen in rainwater 

ranged from 0.24mg/L to 2.89mg/L, ammonium nitrogen, nitrate nitrogen and organic nitrogen 

accounted for 42.8%, 13.3% and 43.9% respectively, nitrogen concentration of rainwater decreased 

with the increase of rainfall, and was obviously diluted by rainfall; Relevant studies (Wang et al., 2014) 

indicated that compared with nitrate nitrogen, attached algae are easier to absorb and utilize ammonia 

nitrogen, leading to algae and other aquatic plants to proliferate in large numbers, resulting in blooms.  

In this work, Chengdu is taken as a representative city of southern China to study the characteristics of 

ammonia nitrogen natural rainfall caused by air pollution sources. Chengdu is a subtropical humid 



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monsoon climate area with mild climate, distinct seasons, long frost-free period, abundant rainfall and 

less sunshine. The annual total precipitation is 918.2mm, mainly in July to August (Chengdu Statistical 

Yearbook, 2016).  

15 natural rainfalls in Chengdu city from April to September 2017 were collected and detected. The 

characteristics of NH3-N pollution in natural rainfalls were analyzed and the temporal and spatial 

variation of NH3-N pollution in rainfalls near toilet vents of buildings was emphasized. Because there 

are no industrial enterprises in urban business area, and residential buildings or office buildings are the 

main structures, the ventilation outlets of the buildings are only toilet vents. 

Total amount of NH3-N in rainfall and land surface runoff was also discussed. The purpose of this work 

is to provide theoretical support for source analysis and control of ammonia nitrogen pollution in water.  

 

2. Method 

2.1 Sample Collection 

From the beginning of obvious precipitation to the end of the rainy season (April to September) in 2017, 

a total of 15 rainfall samples were collected in Chengdu urban area. The natural rainfall sampling sites 

were located near the author's working unit, which is Environmental Protection Building. The sampling 

sites of surface runoff process were located on the roads and pavement near the building. The sampling 

points were arranged as shown in Figure 1 and the attributes of each point are shown in Table 1. 

Natural rainfall samples were collected by a 2000mL barrel. Rainfall runoff samples are collected 

manually by pumping devices.  

 

 
Figure 1. Satellite Map of Sampling Layout 

 



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Table 1. Attributes of Sampling Points 

Serial number Location 
Sampling type 

Pavement attribute 
Rainfall Runoff 

① Opening space in yard √  / 

② Parking lot ground √ √ Cement 

③ Ground near north gate √ √ Concrete 

④ Automobile Lane √ √ Asphalt 

⑤ Roof of building √ √ Waterproof coating 

 

2.2 Monitoring and Detection 

Rainfall monitoring results were recorded with a dump rain gauge (JDZ02-1) combined with real-time 

rainfall data published by Chengdu Meteorological Bureau. The concentration of NH3-N was 

determined by Nessler’s reagent spectrophotometry (HJ535-2009). All samples were detected within 24 

hours after collection. 

 

3. Result and Discussion 

3.1 Variation of NH3-N Concentration in Natural Rainfall 

The NH3-N concentration of all rainfall samples in Chengdu urban area from April to September in 

2017 was monitored and results are shown in Figure 2. It can be seen that the concentration of NH3-N 

in the first rainfall in 2017 was the highest, reaching 18.2mg/L. According to Environmental Quality 

Standards for Surface Water (GB3838-2002), it was far worse than Grade V (≤2mg/L), which is the 

minimum requirement of water quality evaluation. 

 
Figure 2. Ammonia Nitrogen Concentration in Natural Rainfall (April to September in 2017) 

 

The first rainfall in 2017 occurred on April 22, around the Grain Rain Day which is the 6th solar term 

of the 24 divisions of solar year in traditional Chinese calendar. The higher concentration of NH3-N in 



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rainwater is due to the increase of motor vehicle travel in winter and frequent human in indoor 

activities like catering, bathing, heating, etc. The use of natural gas, fuel and other energy causes the 

increase of SO2 and NOx emissions, which promotes the formation and accumulation of (NH4)2SO4 and 

NH4NO3 in atmosphere. The lower temperature in winter is also conducive to the accumulation of 

NH4NO3 in the atmosphere in granular form (Meng et al., 2015). Meanwhile, the atmosphere structure 

is stable in winter, pollutants are not easy to diffuse. Therefore, during the first rainfall, accumulated 

(NH4)2SO4 and NH4NO3 in atmosphere dissolved into the rainwater, resulting in a higher concentration 

of NH3-N. 

NH3-N concentration decreased significantly in the following 14 rainfalls, ranging from 1.6mg/L to 

5.1mg/L, with an average concentration of 3.1mg/L. It can be seen that atmospheric pollutants are the 

main source of ammonia nitrogen in natural rainfall. The first rainfall has a distinct effect on the 

scouring and purification of (NH4)2SO4 and NH4NO3 accumulated in winter atmosphere, which makes 

the concentration of NH3-N in subsequent rainfall decrease significantly. During the study period, 

NH3-N concentration of natural rainfall in Chengdu city was mostly higher than that of Grade V in 

standard GB3838-2002 (except for rainfall on July 21, August 20 and September 18).Excessive 

ammonia nitrogen from rainfall flows into urban rivers, which may make water quality exceed the 

standard requirement and further cause the eutrophication of water body. 

3.2 Effect of Toilet Vent in Buildings on NH3-N Concentration of Rainfall 

The formation of (NH4)2SO4 and NH4NO3 in the atmosphere depends on NH3 emissions. It is reported 

that the main sources of NH3 in atmosphere include livestock and poultry sources, nitrogen fertilizer 

application, synthetic ammonia production and human feces, accounting for 64%, 17%, 1% and 18% 

respectively (Li, 2012). NH3 in Chengdu urban area mainly comes from human excrement, almost all 

of which are discharged into atmosphere through toilet vents in buildings. Therefore, sampling points 

were arranged near the vent (0, 5, 10 and 15m) on the roof of Environmental Protection Building, as 

shown in ⑤ in Figure 1, and NH3-N concentration in rainfall were detected. 

3.2.1 Characteristics of Rainfall 

The concentration of pollutants in precipitation is influenced by many factors, and there is a large 

spatial-temporal difference (Zhang et al., 2010; Pu et al., 2010). In this study, NH3-N concentration in 

two rainfall events (May 13, 2017 and June 9, 2017) was monitored, and the effect of toilet vent on the 

concentration was analyzed. These two rainfall events belong to light and moderate rain and the rainfall 

amounts were 8.2 mm and 23.5 mm, respectively. The rainfall process line is shown in Figure 3. 



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Figure 3. Rainfall Process Line on May 13, 2017 and June 9, 2017 

 

3.2.2 Temporal and Spatial Variation of NH3-NConcentration in Rainfall 

The variation of NH3-N concentration during rainfall process at different sampling points in two 

rainfall events on May 13, 2017 and June 9, 2017 is shown in Figure 4. It can be seen that with the 

prolongation of rainfall duration at different places, NH3-N concentration of the rainfall decreases in 

varying degrees. At the beginning of rainfall, NH3-N concentration decreases significantly with time, 

but at the later stage, the concentration decreases slowly. This is due to the accumulation of ammonia 

nitrogen pollutants in atmosphere during earlier drought period, and the initial scouring effect of 

rainfall makes NH3-N concentration in the initial rainfall higher. However, ammonia nitrogen in 

atmosphere mainly comes from toilet vent in the late stage of rainfall, ammonia gas discharged directly 

or after secondary reaction dissolves into natural precipitation rapidly, so the NH3-N content in late 

rainfall is relatively lower. In addition, due to the moderate rain on June 9, 2017, the rainfall was larger 

and the initial scouring effect was stronger, so the ammonia nitrogen in rainfall decreased more 

obviously. 

 

Figure 4. Variation of NH3-N Concentration in Rainwater at Different Distance from Toilet Vent 

 

By analyzing the variation of NH3-N concentration with time, it was found that ammonia nitrogen in 

natural rainfall at the same sampling point showed a decreasing trend. As the distance from the toilet 

vent increased, the ammonia nitrogen in rainwater decreased, while the attenuation rate raised. In the 

case of larger rainfall, such as the moderate rain on June 9, 2017. NH3-N concentration in the middle 

and late stages was less affected by distance to the vent, and all the values tended to minimum. 



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3.3 Total Analysis of Ammonia Nitrogen Pollutants 

Because NH3-N concentration in rainwater can cannot reflect the pollution degree in urban water, the 

ammonia nitrogen pollution in rainfall and surface runoff was further assessed by the total amount of 

pollutants measurement method. 

3.3.1 Rainfall Analysis 

Three typical rainfalls on April 22, 2017, June 25, 2017 and August 13, 2017 were selected to analyze 

the total amount of ammonia nitrogen pollutants in rainwater and surface runoff. Three typical rainfalls 

on April 22, 2017, June 25, 2017 and August 13, 2017 were selected to analyze the total amount of 

ammonia nitrogen pollutants in rainfall and surface runoff. According to the 24-hour hyetal grade 

standard, the three precipitations belong to light, moderate and heavy rain. On April 22, 2017, the 

rainfall intensity was small and the duration was short; on June 25, 2017, the rainfall intensity was low 

and the duration was long; on August 13, 2017, the rainfall was intense and lasting for a long time, each 

rainfall was 9.26, 21.25 and 34.33mm, respectively. 

3.3.2 Total Ammonia Nitrogen Pollution Analysis 

The total amount of ammonia nitrogen pollutants per unit area in natural rainfall was calculated by 

multiplying the average NH3-N concentration by amount of rainfall per unit area. The calculation 

results are expressed in grams per square meter as shown in Table 2. 

 

Table 2. Total Amount of Ammonia Nitrogen Pollutant in Three Typical Rainfalls in 2017 (g/m2) 

Date 
Opening space in 

yard 
(Rainfall) 

Parking lot 
ground 

(Runoff) 

Ground near north 
gate 

(Runoff) 

Automobile 
Lane 

(Runoff) 

Roof of 
building 
(Runoff) 

2017/04/22 100.5 88.7 97.8 78.3 85.4 

NH3-N loss rate 11.7% 2.7% 22.1% 15.0% 

Average NH3-N loss rate 12.9% 

2017/06/25 77.1 52.5 56.8 69.2 44.1 

NH3-N loss rate 31.9% 26.3% 10.2% 42.8% 

Average NH3-N loss rate 27.8% 

2017/08/13 129.1 82.9 101.8 94.1 80.1 

NH3-N loss rate 35.8% 21.1% 27.1% 38.0% 

Average NH3-N loss rate 30.5% 

 

The total amount of ammonia nitrogen pollutants per unit area of surface runoff can be calculated by 

formula (1), as in 

WT=
∑ Ct×Pt

T
t=0

1000×A
 
                                (1) 

WTis the total amount of pollutants per unit area, g/m2; Ct is the concentration of pollutants in each 

period, mg/L; Pt is the rainfall in each period, L; A is catchment surface area, m2.  

The total amount of ammonia nitrogen pollutants in natural rainfall and surface runoff at different 



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sampling points were calculated. The variation of NH3-N concentration in rainfall and surface runoff is 

shown in Figure 5 with corresponding rain intensity. 

 

 

 

Figure 5. Variation of Rainfall Intensity and NH3-N Concentration in Rainfall and Surface 

Runoff 

 

According to results of monitoring and calculation, the total amount of ammonia nitrogen pollutants in 

natural rainfall is sorted as follows: June 25, 2017<April 22, 2017<August 13, 2017. On August 13, 

2017, the rainfall intensity was strong and lasted for a long time, ammonia nitrogen pollutants in 

atmosphere was fully washed and absorbed by rainwater, the total amount of ammonia nitrogen 

pollutants in the rainfall was the largest. It also showed that rainfall intensity and duration were one of 

the main factors affecting total amount of ammonia nitrogen in rainfall. On the other hand, although the 

intensity of rainfall on June 25, 2017 was greater than that on April 22, 2017, because the rainfall on 

April 22 was the first rainfall in 2017, the accumulation of pollutants in the atmosphere was very large, 



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and the total amount of ammonia nitrogen pollutants dissolved in rainwater was relatively large, which 

also showed that the number of dry days before rainfall is another major factor affecting ammonia 

nitrogen in natural rainfall. 

Moreover, ammonia nitrogen in rainwater is greater than that in surface runoff. The reason is that 

pollutants in rainwater was adsorbed on impervious surface during runoff, which reduces the total 

amount of ammonia nitrogen. During these 3 rainfall periods, the ammonia nitrogen of surface runoff at 

each sampling point has different degrees of loss compared with that in rainfall, as detailed in Table 2. 

The average NH3-N loss rate in surface runoff was 12.9%, 27.8% and 30.5% respectively, which 

indicate that the greater rainfall intensity, the longer duration and runoff time, the more ammonia 

nitrogen can be lost in the process of runoff. 

 

4. Conclusion 

(1) Among the 15 natural rainfalls monitored in 2017, the NH3-N concentration of 14 rainfalls was 

higher than the value of Grade V (≤2mg/L) of Environmental Quality Standards for Surface Water 

(GB3838-2002). NH3-N concentration of the first rainfall was the highest, reaching 18.2 mg/L, and 

then began to decrease in the subsequent 14 events, basically between 2.0 and 5.0 mg/L. Ammonia 

nitrogen accumulated in the atmosphere is an important source of ammonia nitrogen pollutants in urban 

surface water. 

(2) NH3-N concentration in natural rainfall decreases with the increase of the distance between 

sampling point and toilet vent. Ammonia discharged from toilet is an important source of ammonia 

nitrogen in urban atmosphere. 

(3) The main factors affecting the total amount of ammonia nitrogen pollutants in natural rainfall 

include rainfall intensity, time duration and the number of dry days before rainfall. Because of the 

adsorption effect on ground surface, the total amount of ammonia nitrogen pollutants in surface runoff 

is less than that in natural rainfall. Urban ground surface cleaning and emission reduction are the 

fundamental ways to reduce pollution. 

 

References 

Cao, J. J. (2014). PM2.5 and Environment. Beijing: Science Press. 

Din, G. Y. et al. (2007). Simulation study on algal dynamics based on ecological flume experiment in 

Taihu Lake. Ecological Engineering, 31(1), 200-206. 

https://doi.org/10.1016/j.ecoleng.2007.06.013 

Gao, X. M. (2014). Characterization and Sources of PM2.5 Water-soluble Ions in Typical Areas of 

China. Doctor’s thesis. Shandong University, Jinan, China. 

Ge, L. L. et al. (2017). Characteristics and sources apportionment of water-soluble ions in PM2.5 of 

Wenzhou, Zhejiang province. Journal of Zhejiang University (Science Edition), 44(1), 112-119. 



www.scholink.org/ojs/index.php/ees                      Energy and Earth Science                     Vol. 2, No. 1, 2019 

24 
Published by SCHOLINK INC. 

Ge, S. et al. (2015). Characteristics analysis of haze water-soluble ion in Nanjing in autumn. 

Environmental Science & Technology, 38(2), 99-104. 

Huang, P., Zhang, J. B., & Ma, D. H. (2016). Atmospheric deposition as an important nitrogen load to a 

typical agro-ecosystem in the Huang-Huai-Hai Plain. 2. seasonal and inter-annual variations and 

their implications (2008-2012). Atmospheric Environment, 1(129), 1-8. 

https://doi.org/10.1016/j.atmosenv.2016.01.015 

Li, X. Y., & Li, H. P. (2012). Emission and distribution of NH3 and NOx in China. China Environmental 

Science, 32(1), 37-42. 

Meng, C. C. et al. (2015). Pollution characteristics and source apportionment of water-soluble inorganic 

ions in PM2.5 in Handan City. Acta Scientiae Circumstantiae, 35(11), 3443-3451. 

Neal, C. et al. (2006). Chlorophy Ⅱ-α in the rivers of eastern England. Science of the Total 

Environment, 365(1), 1742-1749.https://doi.org/10.1016/j.scitotenv.2006.02.039 

Pu, W. W. et al. (2010). Characteristics and impact factors of acid rain in Beijing. Journal of Applied 

Meteorological Science, 21(4), 464-472. 

Samen, J. M. et al. (2000). Fine particulate air pollution and mortality in 20 US cities, 1987-1994. New 

England of Medicine,343(24), 1742-1749.https://doi.org/10.1056/NEJM200012143432401 

Wang J. J. et al. (2014). Wet deposition of atmospheric nitrogen of Jinshui Watershed in the upper 

Hanjiang River. Environmental Science, 35(1), 66-72. 

Wang, W. X., & Xu, P. J. (2009). Research progress in precipitation chemistry in China. Progress in 

Chemistry, 21(2), 266-281. 

Wang, X. Y., & Zhong, S. (2014). Study on the changes of NH3-N and TN of different seasons in Taihu 

Lake basin. Journal of Anhui Agriculture Science, 42(25), 8712-8713. 

Yang, L. X. et al. (2007). Study on the water-soluble ions in fine particle matter and the long-range 

transport of air masses in the city of Jinan. Journal of Shandong University: Engineering Science 

Edition,37(4), 98-103. 

Zhang X. M. et al. (2010). Research progress of acid precipitation in China. Research of Environmental 

Science, 23(5), 527-532.https://doi.org/10.1080/14786410600800165 

Zhu, J. X. et al. (2015). The composition, spatial patterns and influencing factors of atmospheric wet 

nitrogen deposition in Chinese terrestrial ecosystems. Science of the Total Environment, 1(511), 

777-785. https://doi.org/10.1016/j.scitotenv.2014.12.038 

 


