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Short running title: Nitrate concentration of groundwater
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Nitrate concentration of groundwater and its association with livestock
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farming in Miyakonojo Basin, southern Kyushu, Japan
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Taro Kibana1, Hanako Himuka1 and Ichiro Ebino2
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1 Faculty of Agriculture, Xxxx University, Miyazaki, Japan
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2 Faculty of Agriculture, Zzzz University, Miyazaki, Japan
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Correspondence
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Ichiro Ebino, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192,
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Japan.
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Email: ebino@xxx.miyazaki-u.ac.jp
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Tel & fax: +81 (0)xxx xx xxxx
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Abstract
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Nitrate concentration of groundwater was surveyed in 741 wells in 10 districts in central
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Miyakonojo Basin, southern Kyushu, Japan, to determine the nitrate status in the region
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and to examine its association with livestock farming. Nitrate-N concentration averaged
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5.4 mg L–1, with 13% of the wells exceeding the maximum contaminant level (MCL)
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for drinking water (10 mg L–1). Wells possessed by farmers had a higher maximum
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(48.6 vs. 27.6 mg L–1), mean (7.4 vs. 3.6 mg L–1) and percentage above the MCL (23 vs.
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5%) than those possessed by non-farmers. Occurrence of nitrate in groundwater varied
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not only with the ownership of wells but also among the districts (mean nitrate-N
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concentration = 3.0–8.6 mg L–1, percentage above the MCL = 0–32%). The mean
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nitrate-N concentration of individual districts was positively correlated with both
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excretal nitrogen output from livestock (r = 0.725, P = 0.018) and excretal nitrogen load
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to farmland (r = 0.864, P = 0.001). The results show that groundwater quality in central
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Miyakonojo Basin was considerably deteriorated mainly in farmers’ wells, with
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livestock farming as a responsible source of nitrate contamination.
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Keywords
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Animal waste; farmland; groundwater; nitrate pollution; nitrogen load.
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Introduction
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Nitrogen is essential to life and plays a fundamental role as a major nutrient in global
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ecosystems. However, for the last few decades, there has been an increasing world-wide
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awareness that nitrogen from agricultural activities is largely responsible for
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environmental degradation such as eutrophication in streams and lakes, nitrate pollution
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in groundwater and global warming via nitrous oxide (N2O). Nitrate pollution in
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groundwater is taken as a most serious problem because of its direct adverse effect on
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human health.
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Ingestion of excess nitrate in drinking water causes methemoglobinemia in infants
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under 6 (or 12) months of age (i.e. blue baby syndrome), and can be fatal (Addiscott et
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al. 1990; Follett et al. 1991, 1993; Colleen and Kaneene 1993). ···
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Materials and methods
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Study site
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The study was conducted in 10 districts (Yokoichi, Isoichi, Tsumagaoka, Iwayoshi,
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Komatsubara, Himegi, Shounai, Okimizu, Shiwachi and Nakagou) in the central
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Miyakonojo Basin, southern Kyushu, Japan (Figure 1). Livestock farming is the major
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industry of this region, comprising beef and dairy cattle (mostly housed), pigs and
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broiler chickens.
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Major land use of the region is ···
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Measurements of nitrate concentration of well water
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Water samples were collected in November–December 1997 from 741 wells (farmers’
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possessions = 358, non-farmers’ possessions = 383) in the 10 districts. The sampling
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depth (not necessarily equal to well depth) was also recorded. These wells, accounting
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for 19% of wells in the whole 10 districts (Miyakonojo City Office, personal
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communication), were chosen as randomly as possible from wells whose owners gave
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permission to sample from them. The numbers of sampled wells (farmers’ and
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non-farmers’ possession) were: 61 (47 and 14, respectively) in Yokoichi; 79 (51 and 28)
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in Isoichi; 31 (8 and 23) in Tsumagaoka; 66 (14 and 52) in Iwayoshi; 62 (10 and 52) in
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Komatsubara; 90 (15 and 75) in Himegi; 91 (57 and 34) in Shounai; 78 (14 and 64) in
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Okimizu; 133 (106 and 27) in Shiwachi; and 50 (36 and 14) in Nakagou. Concentrations
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of nitrate and nitrite in the samples were determined by ion chromatography.
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Results
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Nitrate concentration of well water
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Although nitrate toxicity is attributable to nitrite formed by reduction of nitrate, nitrite is
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unstable and is found only at low concentrations in nature. Therefore, to express toxicity
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of water, nitrate concentration is generally used instead of the total concentration of
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nitrate and nitrite. In fact, using ion chromatography in the present study, we detected
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no nitrite in groundwater samples.
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Across all wells in the 10 districts ···
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Excretal nitrogen output from livestock and excretal nitrogen load to farmland
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Annual excretal nitrogen output from livestock in the 10 districts ranged from 21 to
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1,763 t yr–1, being highest in Shiwachi (1,763 t yr–1) and lowest in Komatsubara (21 t
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yr–1) (Table 3). Nitrogen output was closely related to animal population (AU) in the
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district (Pearson’s r = 0.999, P = 0.000; Figure 5), reflecting in part the calculation of
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nitrogen output. The intercept (6.2) of the linear regression equation was not
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significantly different from zero (P = 0.583). The slope showed that one animal unit
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excreted 0.066 t nitrogen per annum.
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Annual excretal nitrogen load to farmland ···
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Discussion
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The present study measured nitrate concentrations only once (November–December; no
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seasonal replications) in 1997 (Figures 2–4) and related them to livestock farming at
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that time (Tables 2–3, Figures 5–6). One may therefore have four major questions about
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the study. Do the data appropriately show the nitrate status of the region in 1997? Have
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the nitrate concentrations remained unchanged thereafter? Why did a considerable time
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lag exist between the data collection and publication of the paper? What is the value of
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the study showing such old data?
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With regard to the first two questions ···
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Conclusions
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The results of the present study show that groundwater quality in central Miyakonojo
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Basin was considerably polluted by nitrate mainly in farmers’ wells, with livestock
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farming as a responsible source of nitrate contamination.
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Acknowledgments
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We are grateful to xxx for cooperation during the study and xxx for reviewing the paper.
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References
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Addiscott TM, Whitmore AP, Powlson DS (1991) Farming, Fertilizers and the Nitrate
Problem. CAB International, Wallingford, UK.
Barnes CJ, Jacobson G, Smith GD (1992) The origin of high-nitrate ground waters in
the Australian arid zone. J Hydrol 137: 181–197.
Colleen SB, Kaneene JB (1993) The effect of nitrate, nitrite and N-nitroso compounds
on animal health. Vet Hum Toxicol 35: 237–253.
Environmental Agency (2000) Report on Groundwater Quality (1999). Environmental
Agency, Tokyo, Japan. (In Japanese.)
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Follett RF, Keeney DR, Cruse RM (eds) (1991) Managing Nitrogen for Groundwater
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Quality and Farm Profitability. Soil Science Society of America, Inc, Madison, USA.
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Hidaka S (1987) Groundwater pollution in the Kushibiki plateau. In: Research on the
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Conservation of Water Quality in the Agroecosystem. Report of the Agriculture,
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Forestry and Fisheries Research Council, Tokyo, Japan, 46–53. (In Japanese.)
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Kawashima H (1996) Food supply and the nitrogen cycle in Japan. J Soc Environm Sci,
Japan 9: 27–33. (In Japanese with English abstract.)
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Table 1 Land use (ha) in the 10 districts in central Miyakonojo Basin (Miyakonojo City 1993)
District
Farmland
Paddy
Upland
Others
Yokoichi
160.9
370.1
31.6
Isoichi
185.0
412.9
Tsumagaoka
185.3
Iwayoshi
Forest
Others
Commercial
124.9
145.8
12.4
5.2
850.9
44.9
207.0
239.7
24.8
8.5
1122.8
59.5
2.2
3.2
192.7
35.5
7.5
485.9
183.5
82.6
8.6
7.3
190.4
46.5
32.9
551.8
68.3
115.9
14.1
17.9
118.4
58.7
21.1
414.4
Himegi
161.7
85.3
4.4
42.6
164.9
52.2
24.9
536.0
Shounai
638.1
630.7
50.8
835.6
188.6
16.7
5.7
2366.2
Okimizu
793.4
156.5
7.1
23.5
180.9
58.0
86.5
1305.9
Shiwachi
635.4
847.5
23.0
548.5
199.3
15.6
35.9
2305.2
Nakagou
555.9
976.0
45.7
5330.0
241.8
12.6
11.7
7173.7
Komatsubara
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Industrial
Total
Residential
Table 2 Livestock population in the 10 districts in central Miyakonojo Basin
Year
District
Beef
Dairy cattle
Pigs
Laying
cattle
1995
2000
2005
Broilers
AU†
hens
A
919
242(206)‡
5044(581)§
17308
50506
2848
B
988
454(308)
10990(1103)
145337
54494
5638
C
349
785(554)
4(4)
0
0
1135
A
328
283(188)
22(6)
2000
0
635
B
239
82(68)
65(55)
0
0
334
C
389
154(107)
56(50)
0
83000
1384
A
1546
620(495)
3425(387)
0
35000
3201
B
4242
1785(1457)
87337(8720)
49100
273900
26724
C
3157
806(648)
40383(4442)
0
475800
16798
†Animal unit (cattle = 1, pigs = 0.2, hens and broilers = 0.01).
‡Adult cows (≥ 2 years old).
§Female pigs for breeding.
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Figure legends
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Figure 1 Location of Miyakonojo Basin and 10 districts in the central Basin.
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Figure 2 Frequency distribution of nitrate-N concentration of well water in central
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Miyakonojo Basin (data pooled over the 10 districts). SD denotes standard deviation.
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Figure 3 Relationship between nitrate-N concentration and depth of well water (sampled
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depth) in central Miyakonojo Basin (data pooled over the 10 districts). r denotes Pearson’s
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correlation coefficient. Symbols show A (○), B (●), C (△), D (▲), E (▽), F (▼), G (□), H
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(■), I (◇) and J (◆).
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Figures
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