Inorganic N of Atmospheric Wet Deposition From A Typical Agro-Ecosystem In Southeast China During Rainy Season

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Procedia Engineering

ProcediaProcedia Engineering 00 (2011) Engineering 18 000–000 (2011) 95 – 100 www.elsevier.com/locate/procedia

The Second SREE Conference on Chemical Engineering

Inorganic N of Atmospheric Wet Deposition From A Typical Agro-Ecosystem In Southeast China During Rainy Season Jian Cui·a,b, Jing Zhou·a*, Ying Peng b, Hao Yang a, Yuan Q. He a a.

Institute of Soil Science, Chinese Academy of Sciences, 71st East Beijing Road, Nanjing, 210008, P.R. China b

College of Geography Science, Nanjing Normal University, 1st Wenyuan Road, Nanjing, 210046, P.R. China

Abstract

Atmospheric N (N) deposition, especially for atmospheric wet deposition has led to changes in agroecosystems from N limited to N saturated. Rained agriculture is weather dependent, and in turn the impact of the vagaries of the rainy rainfall on food production has been of great concern. In this paper, rainy season was determined and characteristics of wet-deposition N, including NH4+-N and NO3--N was done by rainfall and N concentration in rainwater at Red Soil Ecological Experiment Station, Chinese Academy of Sciences (116º55´E, 28º12´N), a typical red soil agro-ecosystem, located in Yingtan city, Jiangxi province, Southeastern China during the rainy season in 2003, 2005 and 2008. The deposition fluxes of NH4+-N and NO3--N in the rainy season was in the range of 4.93-7.75 and 1.19-2.51 kg ha-1, respectively. The inorganic N (NH4+-N plus NO3--N) deposition flux varied from 6.12-10.26 kg ha-1, which was equivalent to 14.57-24.43 kg ha-1 urea or 34.53-57.90 kg ha-1 ammonium bicarbonate applied in the red soil agro-ecosystem. So, the N input of wet deposition during the rainy season could not be neglected in farmland ecosystem. And it is worth considering of reducing N application rate in the red soil farmland. © 2010 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Society for Resources, Environment and Engineering Key words: Inorganic nitrogen, Atmospheric wet deposition, Rainy season, Agro-ecosystem, China 1. Introduction Atmospheric N (N) deposition is increasing due to anthropogenic activities, especially for significant rates of rapid industrialization and agricultural activities [1]. Globally, N deposition has reached 70 Tg yr-1,

1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.11.015

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its mean is 5 kg ha-1 yr-1 [1]. Asia, including China has become a region with the third highest rates of N deposition following North America and Europe, and the rates are projected to continue increasing in the coming decades owing to the fast industrialization and economic development [1,2]. In 2000, NOx emission in China was 11.4 Tg which overpass 280% in 1980 and NH3 was 13.6 Tg which played a significant role in pollutant concentrations in Asian region[3,4]. Increased N emission and deposition can have both positive and negative effects on agro-ecosystem [1,4], which is important for human’s subsistence and is strongly affected by atmospheric actions, such as N limited /saturated, acid rain and soil acidification[5]. The rainy season also plays an important role in the agriculture. In some regions having no readily available water sources, fields especially for paddy fields are irrigated by rainwater during the rainy to maintain crops supply[6]. In China, it is different when rainy season begin and end for the country geography position, as does in red soil regions. The red soil regions covered 2.18×106 ha, accounting for 20% of the total area of China. This region is important for the development of agriculture and economy in China for its abundant natural resources of light, temperature and water. With the economic development, those problems involving environment pollution and soil resource degradation are becoming more serious than before. As the result of instances above, this study focuses on a typical red soil agro-ecosystem in Southeast China to determine the rainy season by the hourly data from the automatic weather station during 20032008, and then characterize N deposition and estimate the N deposition flux in the rainy seasons of the three years (2003, 2005, 2008) to increase knowledge about N deposition in the rainy season and further serve for agricultural produce. 2. Materials and Methods 2.1 Site Description The sample site is located at Red Soil Ecological Experiment Station, Chinese Academy of Sciences (RSES, 116º55´E, 28º12´N), in the suburb of Yingtan city in Jiangxi province, southeast China. Its landscape is a typical hilly region of red soil in subtropical China. Surrounding the study site, farmlands and forestlands covered respectively about 75% and 15% of the area (120 ha), respectively. In the farmlands, more than 320 kg N ha-1 fertilizers were applied each year, mainly in April, May and July. The Yingtan Industrial Park and the Guixi Coal-Burning Power Plant are about 13 km east-northeast and about 30 km northeast of RSES, respectively. 2.2 Sample collection and Analysis Rainwater samples were collected by ASP-2 automatic sampler (WuhanTianhong Instrument Factory, China) on an event basis for measuring the precipitation chemistry from April to June in 2003, 2005 and 2008. During rain events, a wetness detector was triggered to open the lid of the wet deposition bucket. Once the rain stopped the lid closed and sealed the bucket to prevent evaporation and contamination of the sample. The samples were preserved at a temperature below 4○C in previously cleaned polyethylene bottles immediately after collection. These bottles and all equipment in contact with the samples were cleaned with 10% HCl solution, and kept in cleanly plastic bags until they were used for sample collection. NH4+-N and NO3--N were determined by the indophenol blue spectrophotometric and ultraviolet spectrophotometric method, respectively. Profile hourly meteorological data (including wind speed and direction, precipitation) were continuously monitored with automatic weather station (VSALA-ML520, Finland) during 2003-2008. Wind data were monitrored at 10m above ground level during the study period. 2.3 Statistical Analysis The monthly wet deposition fluxes for each N species (Fd, kg ha-1) were calculated by

Fd  PC a

where P is the monthly deposition precipitation (mm), Ca is the corresponding monthly N concentration (mg L-1).

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Descriptive statistics were used to characterize the monthly data of N collected during the sampling period. Mean and standard error were reported for each concentration of each N species. To study the composition of N deposition, the contributing proportionality of each inorganic N species was calculated. The monthly data collected were used in the one-way ANOVA and the correlation analysis in SASS 9.0. 3. Results and discussion 3.1 Characteristics of rainy season During the six years (2003-2008), annual rainfall was 1392.8-1932.6 mm (Fig.1, Table 1). The month of lager rainfall mainly concentrated in April, May and June and its mean was 251.0 mm/month. And the number of rain day also converged in the three month above, its mean was 16 d /month. What’s more, the cumulative days of rainfall (>25mm/d) ranged from 6-8 d during April-June, accounting for 35.29%75.00% of the accordingly year. So the rainy season in the study site mainly lasted from April to June every year. The number of rainfall in the rainy season ranged from 515.9-1187.0 mm, with 36.82%-61.4% accounting for the corresponding annual rainfall during 2003-2008 (Table 1). The maximum of rainfall both in the rainy season and the whole year appeared in 2006 while the minimum in 2007. But there were all the similar rainfall and rain frequency in the rainy seasons for 2003, 2005 and 2008, its rainfall and rain frequency were 827.1, 700.6 and 687.4 mm and 52, 46 and 48 d, respectively. So the three rainy seasons can more display typical article of the study site. a

b

Jan. 450 Dec.

Jan. 30 Dec.

Feb.

Nov.

Nov.

Mar.

Mar. 10

150

Oct.

0

May

Aug.

Jun. Jul.

Apr.

0

Sep.

May

Aug.

2006

Oct.

Apr.

Sep.

2003

Feb. 20

300

2004

2005

2003

2007

2008

2006

Jun. Jul.

2004

2005

2007

2008

Fig.1 Monthly rainfall (a) and rain frequency (b) during 2003-2008 Table 1 The cumulate rainfall and rain frequency during the monsoon during 2003-2008 Rainfall(mm)

Rain frequency

Apr.-Jun. Whole year <10mm rainfall 10-25mm rainfall >25mm rainfall Sum.

2003

2004

2005

2006

2007

2008

827.1 1407.3 31 9 12 52

515.9 1401.1 22 11 6 39

700.6 1659.6 32 5 9 46

1187 1932.6 28 14 12 54

599.4 1392.8 36 8 11 55

687.4 1493.2 30 10 8 48

3.2 Concentrations of N in precipitation Fig.2 shows the monthly concentrations of NH4+-N and NO3--N, that is Cm(NH4+-N) and Cm(NO3--N) of rainwater collected. During the three rainy seasons, Cm(NH4+-N) were higher than Cm(NO3--N). Cm(NH4+-N) ranged respectively from 0.34-2.20 mg L-1 and Cm(NO3--N) from 0.02-0.62 mg L-1. For every precipitation during May-June in 2008, it was larger that concentrations of NH4+-N were 0.16-1.96 mg L-1. The reason was correlated with the characteristic of NOx and ammonia and its emission source.

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2008

-

NO3 -N

-1

1.5

2.0

1.0

2005 0.5

1.5

2003

30-Jun.

26-Jun.

20-Jun.

2-Jun.

16-Jun.

12-Jun.

29-May

25-May

18-May

10-May

0.0

1.0

Date

0.5

Jun.

Apr.

May

Jun.

Apr.

May

Jun.

Apr.

0.0

May

Monthly nitrogen concentration in rainwater (mg L )

2.0

+

NH4 -N

2.5

Fig.2 Monthly concentrations of NH4+-N and NO3--N, that is Cm(NH4+-N) and Cm(NO3--N) of rainwater collected.

Oxidized N, NOx is formed through atmospheric reactions and fossil fuel combustion and is apt to generate long distance transportation, which the distance may arrive thousands of kilometers. It is found in the form of gaseous nitric acid (HNO3), N dioxide (NO2) and aerosol nitrate (NO3-). Power plants and motor vehicles are the primary sources[7]. For rural areas, NO3--N concentration was governed by imported NO2 pollution[8]. As for as our study, the prevailing wind direction is from south-southwest to southwest-west and northwest during the three rainy reason. And the Guixi Coal-Burning Power Plant, as the main NO2 emission resource, is located downwind of the prevailing wind direction, which maybe lead to lower NO3--N concentration. Ammonia is known to volatilize from soils and was produced mainly by N fertilizer and farm manure [7] . NH4+-N concentration of wet deposition had a significant correlation with total ammonia volatilization loss from N fertilizer applied in rice growing season in Eastern and Northeastern China [9,10]. In China, NH4+-N loss accounted for 0.40%- 40% for N applied in farmlands [10]. Chemical fertilizer usage showed increased tendency by 16.8% every five years in Jiangxi province in 1980-2005. Only in one city named Guixi city belonging to Yingtan city, N fertilizer usage arrived N 4,718 kg. In the beginning of the rainy season, it was the sowing time for peanut and rice. Quantities of N fertilizer were applied usually with unreasonable amount and manner in the study site, which maybe resulted in higher NH4+-N concentration of precipitation in this study agro-ecosystem. 3.3 N fluxes from wet atmospheric deposition Table 2 The seasonal N fluxes of wet deposition and monthly N deposition fluxes for NH4+-N, NO3--N and inorganic N during the three monsoon seasons. in the monsoon during 2003, 2005 and 2008. April NH4+-N NO3--N

May NH4+-N NO3--N

June NH4+-N NO3--N

Monsoon season NH4+-N NO3--N I-N

2003

1.72

0.56

1.28

0.08

1.93

0.55

4.93

1.19

6.12

2005

0.97

0.32

1.49

0.25

4.45

1.42

6.92

1.99

8.90

2008

6.25

1.54

1.01

0.69

0.49

0.27

7.75

2.51

10.26

During the three rainy seasons, Fd(NH4+-N) and Fd(NO3--N) were in the range of 0.49-6.25 and 0.081.54 kg ha-1, respectively. Though there were some variations for monthly N deposition flux, both Fd(NH4+-N) and Fd(NO3--N) were higher in April and June (Table 2). Table 2 also shows that all of the cumulants of Fd(NH4+-N), Fd(NO3--N) and Fd(I-N) arrived the maximum in April and the minimum in May. This was associated with crop planting. Usually, April is a sowing season and June is a

Jian Cui name et al. // Procedia – 100 Author Procedia Engineering Engineering 18 00 (2011) (2011) 95 000–000

Usage of chemical fertilizer and number of motor vehicle

supplemental fertilizing season for peanut and rice. Plenty of compounds containing N especially for NH3 are emitted into the surface air over the filed and are brought into fields with rainwater, which results in higher N deposition flux in April and June in our study agro-ecosystem. During the study rainy reasons, monthly ratio mean of F(NH4+-N)/F(NO3--N) was 3.3±1.4 except 16.0 for May 2005,which meant that NH4+-N deposition was the main form for inorganic N from wet deposition in the red soil ago-ecosystem. The monthly ratios of F(NH4+-N)/F(NO3--N) ranged from 1.5 to 6.0, which good in agreement with other’s results (1.5-5.7) [9,10]. This was closely related to cropping season. It was in agricultural planting season and fertilizer was active (Anderson and Downing, 2006), which caused more NH3 shifted from N fertilizer and resulted in much more NH4+-N deposition along with precipitation. The cumulants of seasonal fluxes for NH4+-N and NO3--N were from 4.93-7.75 and 1.19-2.51 kg ha-1 in the three rainy seasons (Table 2). Compared with the three rainy seasons, accumulatively seasonal fluxes for NH4+-N and NO3--N had an increasing trend but its increasing velocity reduced. Both the usage of N fertilizers and number of motor vehicles were increasing each year during 1995-2005 (Fig.3), which led to the increasing N concentration in the surface air and further to the increase of N deposition flux in this study site. At the same time, cleaner fuel and tighter emission standards were introduced and newtype motor vehicles were used, which also further reduce NOx emission. The factors above in common made accumulatively seasonal fluxes for NH4+-N and NO3--N increased and its increasing ration reduced. During these rainy reasons in our study period, the accumulative Fd(I-N) ranged from 6.12 to 10.26 kg ha-1, which was equivalent to the usage of urea (14.57-24.43 kg ha-1) or ammonium bicarbonate (34.5357.90 kg ha-1). This indicated that rain played an important role in the N biogeochemical circulation. Taking gaze and vegetable rotation ecosystem as the object of study, contribution of N input from atmospheric wet deposition on N balance in the red soil agro-ecosystem was discussed and then found total wet N flux was 34.34 kg ha-1, with 12.97%, 17.65% and 40.90% contribution rate to the input, output and surplus of T-N in the farmland ecosystem during April 2005 to January 2006 [9]. This also indicated that wet-deposition N could not be neglected in farmland ecosystem. 500

usage of chemical fertilizer number of motor vehicle

400

300

200

100

0 1980

1985

1990

1995

2000

2005

Year

Fig.3 Usage of chemical fertilizer (1,000 t) and number of motor vehicle (1,000) in Jianxi province during 19802005. These data all came from Jiangxi Statistical Yearbook 2008.

4. Discussion In recent ten years (1994-2004), it was 7.89 to 38.46 kg ha-1 for annual N input to agro-ecosystems by atmospheric wet deposition in China, the ratio of F(NH4+-N)/F(NO3--N) was 1.3 to 2.9 [11-14]. It could be inferred that NH4+-N deposition was dominant in N deposition by precipitation and critical loads for most of agro-ecosystems were about 0.8-7.6 times higher than that of terrestrial ecosystems, and were in or beyond critical loads of forest ecosystems. Compared with other regions or countries in the word, annual

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N deposition was far greater than that 7.7 kg ha-1 in America [11], 7.3 kg ha-1 in Japan [12]. In our study site, only during the rainy season (three months) inorganic N deposition by precipitation was 6.12 to 10.26 kg ha-1, which was a little higher than the upper limit of critical loads of terrestrial ecosystems including farmland ecosystems (5-10 kg ha-1 yr-1 [13]). And the usage of N fertilizers arrived 176-220 kg ha-1 in Yingtan during 2000-2007. Moreover, China is a major N fertilizer consumer and overuse of N fertilizer made substantially regional soil N surpluse. Only in the Yangtze River basin’s agricultural fields including our study site, there were N surpluses which reached 3.42×106 t yr-1 in 1999 and 4.78×106 t yr-1 in 2000. Overuse of N fertilizer contributes substantially to regional soil acidification in China[14]. However, only in the rainy season (April-June), there had a high N deposition in our study agroecosystem. Therefore, it is worth considering that N application rate should be reduced properly for lowering the cost of agricultural produce and improving the agricultural environment. And fertilization based on comprehensive, knowledge-based N management practices also should made for sustainable agriculture in red soil region in China and in other rapidly developing regions worldwide. Acknowledgements This work was supported by the National Key Technology Research and Development Program of China (2011BAD41B00, 2009BADA6B04 and 2009BADC4B02) and the CAS Innovation Program (ISSASIP0730). Thanks are given to Benhua Chen and Youjun Guan employed in the RSES for their help in collecting samples. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

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