IJERD – International Journal of Environmental and Rural Development (2014) 5-2

Research article
erd

Evaluation of Nitrate Pollution in River Water atAgricultural Watershed
TOSHIMI MUNEOKA*
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Email: muneoka@obihiro.ac.jp

YURI YAMAZAKI
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, JapanSACHIYO WAKOU
Department of Agriculture, Forestry & Fishery, Ibaraki Prefectural Government, Ibaraki,
Japan

MASATO KIMURA
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, JapanOSAMU TSUJI
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Received 30 October 2013

Accepted 1 April 2014(*Corresponding Author)

Abstract Nitrate pollution of river water and groundwater in agricultural areas is a serious
problem in many countries, and many people are unconcerned with, or ignorant of, theproblem. In recent years, environmental education on the relationship between agriculture
and water has been provided to the general public in many areas in Japan. In this report,
the nitrate nitrogen (NO3-N) concentration in river water at the normal water level wasevaluated in two agricultural areas in Eastern Hokkaido. The concentration results
obtained using an official analytical method were compared with those obtained using
simplified methods. By focusing on the differences in the results of the measurement
methods, the applicability of simplified methods for NO3-N concentration to water
environmental education was examined. The investigation was carried out in two
agricultural areas in Eastern Hokkaido in late August 2006. NO3-N concentration wasmeasured using an official method and two simplified methods. The comparison between
the two results showed the NO3-N concentration values measured by using the simplified
methods to be 64% to 72% of those measured by using the official analytical method. The
values obtained from the simplified methods were slight underestimates. However, there
was a significant positive correlation between the two sets of values. Even though someconsideration is necessary regarding the accuracy of the simplified methods, it can be said
that the use of such methods in water environmental education is sufficiently effective. It
is also expected that by actively introducing experience-based environmental education inwhich river water quality is measured by learners using simplified methods, it will bepossible to make environmental education truly useful in the conservation of desirable
watersheds in which sustainable agricultural and forestry are developed and desirable
water quality is maintained.
Keywords NO3-N concentration, simplified method, official analytical method, environmental
education

INTRODUCTION
It is well known that nitrate pollution of river water and groundwater in agricultural areas hasgrown to become a serious problem in many countries of the world. Another fact is that there areⒸ ISERD51

IJERD – International Journal of Environmental and Rural Development (2014) 5-2

many people who are unconcerned with, or ignorant of, the problems on nitrate pollution of riverwater. In considering the problem of agriculture and water in terms of environmental education andlearning experiences for basic knowledge, it is necessary to evaluate nitrate nitrogen (NO3-N)
concentration in river water in a watershed with agriculture and forestry.
In Japan, there are two major water quality standards that use nitrogen as indices. “TheEnvironmental Standards Concerning the Protection of the Human Health” specifies 10 mg/L as
the highest acceptable combined concentration of NO3-N and nitrite nitrogen (NO2-N). “TheEnvironmental Standards Concerning the Conservation of the Living Environment” specifies
1 mg/L as the highest acceptable concentration of total nitrogen (T-N).
The authors have been investigating the concentration of NO3-N in river water at the normal
water level for many years in two agricultural areas with different land-use characteristics inEastern Hokkaido, which possesses valuable regional characteristics as a part of the region that isinfluenced by Asian monsoons (Yamazaki et al, 2013; Muneoka et al, 2013; Yamazaki et al,2014). It is anticipated that investigations that lead to the development of measures for controllingthe amount of nitrate flowing into river water in watersheds in agricultural and forestry areas will
progress by using the basic data accumulated in such activities.
In recent years, university faculties have been providing environmental education to thegeneral public as outreach activities for local communities. One theme is the problem of agriculture
and water (Muneoka et al, 2007; Muneoka et al, 2012).
When researchers and engineers measure the NO3-N concentration in river water for theirinvestigations and studies, they generally follow official analytical methods, such as the Japan
Industrial Standards (JIS). Such measurements involve burdens such as time and expense forobtaining and maintaining facilities and equipment for measurement. Training to foster technicalskills that guarantee the accuracy of measured values is also indispensable.
Currently, a simplified method which makes use of inexpensive and easy-to-use water test kits
is widely available in Japan. These make it possible for lay citizens to perform environmental
surveys and for educators to use them in environmental education for children, who will be themain players in the environmental conservation activities of the future and in lifelong learning
programs for adults. Few studies have tested the accuracy and reliability of these simplified
methods.
This report discusses the evaluation of nitrate pollution in river water in two areas withdifferent agricultural land uses in Eastern Hokkaido, based on the perspective of environmental
education. The NO3-N concentration in river water at the normal water level analyzed using theofficial analytical method and that measured using the simplified methods were compared.
Examination was done on the applicability of simplified methods in water environmental
education, focusing on the difference between the two types of measurement methods.
METHODOLOGY
The two investigated areas are outlined in Fig. 1. The Tokachi area, which has 24 watersheds (No.
1 to 24), is in the northwestern part of the area under the jurisdiction of the Tokachi General
Subprefectural Bureau and is an area with upland and dairy farming. The Nemuro area, which has
11 watersheds (A to K) located in the western part of the jurisdiction of Nemuro Subprefectural
Bureau, is an area mainly of dairy farming.
For the years 1981 to 2010, the annual mean air temperature and the yearly precipitation were
5.9 ˚C and 840.7 mm at Komaba in the Tokachi area, and 5.4 ˚C and 1158.0 mm at Nakashibetsu in
the vicinity of the Nemuro area. Both areas have a relatively cold climate with less rainfall thanother agricultural areas in Japan.
The proportion of land use were determined in the two watersheds, and the investigation of theriver water quality was conducted at the normal water level at 35 sampling points in the two
investigated areas in late August 2006. Later, NO3-N concentration was measured in the laboratory,
using the above-described official analytical method and two simplified methods. The details of thecompared methods are shown in Table 1.
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One simplified method for measuring NO3-N is Pack Test, which use is extremely easy. First,
the sampled water is put in a plastic tube that contains a reagent, and it is shaken several times tomix it well. After 3 minutes, the color of the contents of the plastic tube is compared with the color
in the test kit chart, to determine which color in the chart is closest to the sample color. The closest
color is the NO3-N value for the sample. When the sample color is in between two colors in thechart, the value between the two colors is read. In this way, measurers can visually obtain theNO3-N value at the range from 0.23 mg/L to 10 mg/L.

Fig. 1 Outline of the Tokachi and Nemuro areas
Table 1 Measurement methods on the NO3-N concentration
Measurement
methodSimplified method

Official analytical method
Chromotrope acid method

Pack Test

Digital Pack Test

Measurement
Equipment

Test tube / Reagents/ Deionized water etc.
(Absorptiometer)

Water Test Kit

Water Test Kit(Test kit chart)(Original absorptiometer)

Measuring range

0.2-30 mg/L

0.23-10 mg/L

0.2-5.0 mg/L

Sensitivity

0.1 mg/L

coarse precision

0.1 mg/L

Coloring time

5 minutes

3 minutes

5 minutes

Measuring valueNumerical value(Digitalized value)Comparison with
"Test kit chart"

Numerical value(Digitalized value)cf:
Naphthylethylene diamine
methodafter zinc reduction

cf:Naphthylethylene diamine
absorptiometry
after zinc reduction

N.B.

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Another simplified method is Digital Pack Test, which is an improved version of theconventional Pack Test, this method (absorptiometer) gives digitized value with an accuracy of 0.1
mg/L to 5.0 mg/L.
In this report, the values of NO3-N concentration in river water obtained from both two
simplified methods and the official analytical method were compared.
RESULTS AND DISCUSSION
Relationship between NO3-N Concentration and Proportion of Agricultural Land Use
From the 35 sampling points in the two watersheds, a positive correlation has been found between
the proportion of agricultural land in the watershed and the NO3-N concentration in river water ineach area as measured by the official analytical method (Fig. 2 (a), (b)). For the area with a highproportion of upland fields, the NO3-N concentration in river water was found to exceed thatspecified in various water quality standards (i.e., total nitrogen concentration of 1 mg/L or lower).
When we consider the problem of agriculture and water and the effect of hands-on learning inenvironmental education, in which the learners actually measure the water quality, it is desirable
that the NO3-N concentration obtained using simplified methods have as high measurement
accuracy as possible.
8.0

Y = 0.055 X
r = 0.89(b) Nemuro area
Y = 0.031 X

3.0

NO 3 -N (mg/L)

6.0NO 3 -N (mg/L)

4.0(a) Tokachi area※※

4.02.0r = 0.96

※※

2.0

1.00.00.0020406080

1000

Proportion of agricultural land (%)

20406080

100

Proportion of agricultural land (%)

Fig. 2 Relationship between NO3-N concentration and Proportion of Agricultural land use(Tokachi and Nemuro areas, 2006)

Difference of Measurement Methods in Relation to the NO3-N Concentration
To compare the NO3-N concentration in river water as measured by the official analytical method(X axis) with that measured by the simplified methods using Pack Test and Digital Pack Test (Yaxis), the regression line that represents the relationship between the two sets of values (Y＝aX)
and the coefficient of correlation r were obtained (Figs. 3 (a), (b) and 4 (a), (b)).
The comparison found a correlation with a significance level of about 1% between Y and X
for both of the investigated areas. The NO3-N concentrations in river water as measured by thesimplified methods were 64% to 72% of those as measured by the official analytical method. Thevalues as measured by the simplified methods were underestimates. However, it is sufficiently
effective for water environmental education that using the simplified methods to objectively
evaluate the water quality by actually measuring it to determine whether nitrogen levels are safe ornot.
It is hoped that effective education of the general public of a wide range of ages will bepossible by implementing water environmental education that combines conventional lectureoriented learning of basic knowledge on problems of agriculture and water with hands-on learningⒸ ISERD54

IJERD – International Journal of Environmental and Rural Development (2014) 5-2

in which the learners measure the NO3-N concentration of river water. The simplified methodsPack Test, in particular-are very beneficial, because the general public is able to visually determine
the NO3-N concentration in river water easily and at low cost.
4.0(a) Tokachi area
Y = 0.64 X

6.0

Pack test (mg/L)

Pack test (mg/L)

8.0

r = 0.93 ※※4.0

2.0(b) Nemuro area
Y = 0.68 X

3.0r = 0.92 ※※2.01.0[NO3-N concentration][NO3-N concentration]

0.0

0.0
0.0

2.0

4.0

6.0

8.00.0

Official analytical method (mg/L)

1.0

2.0

3.0

4.0

Official analytical method (mg/L)

Fig. 3 NO3-N concentration obtained by Pack Test and Official analytical method(Tokachi and Nemuro areas, 2006)
4.0(a) Tokachi area

Digital pack test (mg/L)

Digital pack test (mg/L)

8.0

Y = 0.72 X

6.0

r = 0.95 ※※4.0

2.0(b) Nemuro area
Y = 0.68 X

3.0

r = 0.93 ※※
2.0

1.0

[NO3-N concentration][NO3-N concentration]

0.00.0
0.0

2.0

4.0

6.0

8.0

0.0

Official analytical method (mg/L)

1.0

2.0

3.0

4.0

Official analytical method (mg/L)

Fig. 4 NO3-N concentration obtained by Digital Pack Test and Official analytical method(Tokachi and Nemuro areas, 2006)

Desirable conservation of watersheds in agricultural and forestry areas that takes into
consideration the realization of sustainable agriculture and the conservation of river water quality isalso expected to be possible through the active introduction of hands-on environmental educationin which river water is measured by using simplified methods.
CONCLUSION
In improving the effectiveness of water environmental education such that it combines lectureoriented learning of basic knowledge with experience-oriented learning in which the participantsmeasure river water quality, further improvement in the water measurement methods and theaccuracy of such methods is an indispensable issue to be addressed. It is necessary to examine theapplicability of the simplified methods to environmental problems related to agricultural activities
and water quality indices other than NO3-N concentration.

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ACKNOWLEDGEMENTS
We would like to express our gratitude to the research assistance provided by the students, Obihiro
University of Agriculture and Veterinary Medicine.
REFERENCES
Muneoka, T., Kimura, M. and Tsuji, O. 2012. Outreach activities for irrigation, drainage and rural
engineering in Tokachi district, Hokkaido. Water, Land and Environmental Engineering, 80 (1), 19-22(in Japanese).
Muneoka, T., Tsuji, O. and Ashizawa, M. 2007. Water environmental education in Tokachi district,
Hokkaido. Applied Hydrology, 20, 54-61 (in Japanese with English abstract).
Muneoka, T., Yamazaki, Y., Wakou, S., Shimura, M., Yoshino, K., Tsuji, O. and Tabuchi, T. 2013. The
nitrogen runoff characteristics in agricultural watersheds after enforcement of animal waste regulation.
IJERD, 4 (2), 56-61.
Yamazaki, Y., Muneoka, T., Wakou, S., Shimura, M., Yoshino, K., Tsuji, O. and Tabuchi, T. 2013. The
difference of agricultural land use in watersheds and long term fluctuation on the river water quality.
IJERD, 4 (1), 152-157.
Yamazaki, Y., Muneoka, T., Wakou, S., Kimura, M. and Tsuji, O. 2014. Evaluation of the ion components
for the estimation of total nitrogen concentration in river water based on electrical conductivity. IJERD,
5 (1), 160-164.

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