S. YADA, Y. NAKAJIMA, T. HORIO, K. INAO, S. ITAHASHI,
K. ASADA, S. YOSHIKAWA , S. EGUCHI
Institute for Agro-Environmental Sciences, NARO
Identifying sources of nitrate in an irrigated rice paddy
watershed, Tsukuba, Japan
1WLC16: Bali, Indonesia: November 7-11, 2016
● Background and objectives
● Method
● Results and discussion
● Conclusion
2WLC16: Bali, Indonesia: November 7-11, 2016
Contents
Topic
First comprehensive research using nitrate
(NO3−) isotopes (δ15NNO3 and δ18ONO3) of river
water in an irrigated or non-irrigated rice
paddy watershed.
3
Household wastewater
WLC16: Bali, Indonesia: November 7-11, 2016
Background and object
http://wwwrcamnl.wr.usgs.gov/isoig/isopubs/Fig16-9c.gif
δ15NNO3(‰)
household waste
Identifying NO3− sources for lake water conservation
Transboundary irrigation
http://suido-ishizue.jp/kokuei/kanto/ibaragi/kasumigaura/0201.html
Lake intake
Irrigation tap
Pipe line
Pumping station Drainage + Stream water
WLC16: Bali, Indonesia: November 7-11, 2016
Kasumigaura water conveyance
Rice paddywatershed
Rice paddy
4
5
Scheme of the water circulation
WLC16: Bali, Indonesia: November 7-11, 2016
Non-irrigation periodIrrigation period
6
Study area
Sakasagawa River 0 1 km
1 2 3
45
Rice paddy field
Upland/Orchard
Village
Golf course
Forest
Mountainstream(hillside)
Mountainstream(foothill)
Irrigationwater
Drainegewater
Riverwater
Mt. Tsukuba (876m a.s.l.)
WLC16: Bali, Indonesia: November 7-11, 2016
○Hillside stream
▲Foothill stream
Irrigation water
○Drainage water
●Mainstream river
Golf course
Residential area
Upland
Rice paddy field
Forest
･
Hotel
Hotel
SakasagawaRiver
N2O→N2への
還元酵素を持たない脱窒菌
分析試料
(NO3-30nmol)
NO3- NO3
-→N2O N2O
N2ON2O
②培養①サンプル導入 ③完成
N2O→N2への
還元酵素を持たない脱窒菌
分析試料
(NO3-30nmol)
NO3- NO3
-→N2O N2O
N2ON2O
N2O→N2への
還元酵素を持たない脱窒菌
分析試料
(NO3-30nmol)
NO3- NO3
-→N2O N2O
N2ON2O
②培養①サンプル導入 ③完成
Denitrifyig bacteria
medium vial (20 mL)
Injection of
water sample
7
Nitrate isotope determination by IRMS
Denitrifier method (Casciotti 2002)
Denitrifying bacteria culture
(lack in N2O reductase, 200 mL)
GC-IRMSm/z 44,45 and 46
WLC16: Bali, Indonesia: November 7-11, 2016
DELTA V
8
Seasonal patterns of isotopic composition of nitrate
Outlet of
watershed
(Site1)
0.0
0.5
1.0
1.5
0
5
10
0.0
2.5
5.0
Apr.Mar.
Non-irrigation periodIrrigation period
20132012 Feb.Jan.Dec.Nov.Oct.Sep.AugJul.Jun.MayApr.
NO
3-N
(m
g/L
)
Apr.Mar.20132012 Feb.Jan.Dec.Nov.Oct.Sep.AugJul.Jun.MayApr.
δ1
5 N(‰
)
Apr.Mar.20132012 Feb.Jan.Dec.Nov.Oct.Sep.AugJul.Jun.MayApr.
δ1
8 O(‰
)Irrigation period Non-irrigation period
Irrigationperiod
WLC16: Bali, Indonesia: November 7-11, 2016
δ1
5N
NO
3(‰
)δ
18O
NO
3(‰
)N
O3-N
(mg L
-1)
No distinct
evidence of
denitrification
0.5
2.0
1.5
1.0
2.5
3.0
NO3-N (mg L
-1)
(mg/L)
9
Identifying sources of river water nitrate
0 5 10 15 20-5
0
5
10
15
δ15
N-δ18
O relationship during non-irrigation periodδ
18 O
NO
3(‰)
δ15
NNO
3
(‰)
○Mountainstream (hillside)
○Mountainstream (foothill)
○Drainagewater
●Riverwater (mainstream)
Non-irrigation period
Householdwastewater
δ15NNO3（‰）WLC16: Bali, Indonesia: November 7-11, 2016
Householdwastewater
Chemicalfertilizer
NO3- in Precipitation
○ Hillside stream○ Foothill stream○ Drainage water●Mainstream river water
0 5 10 15 20-5
0
5
10
15
0 5 10 15 20-5
0
5
10
15
0 5 10 15 20-5
0
5
10
15δ
18O
NO
3(‰)
δ15
NNO
3
(‰)
○Mountainstream (hillside)
○Mountainstream (foothill)
●Irrigationwater
○Drainagewater
●Riverwater (mainstream)
δ1
8O
NO
3(‰)
δ15
NNO
3
(‰)
δ15
N-δ18
O relationship during irrigation period
0.5
2.0
1.5
1.0
2.5
3.0
NO3-N (mg L
-1)
(mg/L)
10
Irrigation period
Identifying sources of river water nitrate
Lower nitrate concentrationsin irrigation water
δ15NNO3（‰）WLC16: Bali, Indonesia: November 7-11, 2016
δ15NNO3（‰）
Chemicalfertilizer
Diluted NO3-
in drainage water
○ Hillside stream○ Foothill stream
Irrigation water○ Drainage water●Mainstream river water
11
Conclusion
Nitrogen (N) and oxygen (O) isotopes of nitrate
(δ15NNO3 and δ18ONO3 ) in river water can be used
as a powerful tool to identify sources in a rice
paddy watershed
WLC16: Bali, Indonesia: November 7-11, 2016
=>The major sources of NO3− were;
household wastewater and chemical fertilizer
=>The drainage water had a significant effect on
NO3- dilution of the river water during irrigation period
12http://d3e8ogs60q6bjk.cloudfront.net/image/production/acp/3000007727/pln3000019555/8a44eb4e-1d0e-47a9-b5eb-909a71f9b178.jpg
http://www.expocenter.or.jp/wp-content/uploads/center_outside-600x403.jpg
http://www.tsukubapress.com/imgtsclab/niaes.jpg
Thank you for your attention
Lake Kasumigaura Tsukuba center Institute for Agro-EnvironmentalSciences, NARO
See you Ibaraki in 2018 !!
