Actuality Evaluation of Agricultural Non-point Source Pollution in the Zhangweinan Basin

Actuality Evaluation of Agricultural Non-point Source Pollution in
the Zhangweinan Basin
– Case Studies in Lucheng City and Xinxiang County
LUO Zunlan, ZHAO Caiyun, LI Junsheng
Chinese Research Academy of Environmental Sciences, Beijing, P.R.China, 100012
[email protected]
Abstract: This study took Lucheng City and Xinxiang County in Zhangweinan Basin as the typical
cases to investigate and analyze the potential agricultural non-point source pollution. The potential
pollution loads (PPL) of total N of Lucheng City and Xinxiang County are 46,855 t and 50,262 t,
respectively; the potential pollution loads of total P are 5,604t and 4,292 t, respectively; and the potential
pollution loads of COD are 14,868t and 10,862t, respectively. We also analyzed the components and
sources of the agricultural non-point source pollution, and calculated the amounts of total N, total P and
COD discharged into rivers.
Keywords: Agricultural non-point source pollution (ANPSP), evaluation
Water pollutions can be divided into two types, the point source pollution and non-point source pollution,
and the latter includes agricultural non-point source pollution and urban non-point source pollution. For
the strong randomness, wide distribution range, complicated mechanism and pollution time lag of
non-point source pollution, related researches made slow progress. But more and more attention has
been paid to this issue since point source pollutions were under effective controls. Agricultural non-point
source pollution (ANPSP) is one of the most important aspects of water pollution. Nowadays there are
plenty of studies associated with this subject, but the evaluations of ANPSP are regional questions, and
few studies have been carried out in Zhangweinan Basin. Since the water pollution of this region is very
serious and typical, it is very important to evaluate its current state of ANPSP, and provide scientific
reference to pollution control. And because the area of this region is very wide and the detailed data are
lacking, our study takes Lucheng City as the typical case of mountainous areas, and Xinxiang County
the typical case of plain areas, and analyzes their current state of ANPSP.
1 Study area
The Zhangweinan Basin (35°N – 39°N, 112°E – 118°E), covers 37,700 km2. Southwest of this region is
higher and northeast is lower. The upstream mountain areas account for about 67% of the study area,
and the downstream plain areas account for about 32.5%. The climate is temperate, semihumid and
semiarid, the annual mean temperature is about 14°C, annual mean precipitation is 608 mm, and annual
mean runoff is 67.5 mm.
This region suffers from water resources shortage. The water use of middle and lower reaches badly
depend on Yellow River diversion project and overexploitation of underground water. Its annual mean
water resource per person is only 240 m3, and its water resources exploitation and utilization ratio is
above 90%. Because of the overexploitation of underground water, the groundwater level has dropped,
and it is formed a deep groundwater funnel area of about 21,400 km2, centered in Tianjin, Changzhou
and Dezhou.
According to the investigation of the 22 rivers (1,789 km) in the Zhangweinan canal river system, the
water problem of this region is very serious. The length of river with Grade I water is 30 km, only
accounting for 1.7% of the total river length; and the total length of river with Grade V and worse than
Grade V water is 1,432 km, accounting for 79.8%. Water quality of most reaches is very bad, and fish
and other aquatic organisms are disappeared, and middle and lower reaches are becoming drainage
ditches, even more, the underground water along the Zhangweinan canal have been polluted at different
degrees.
Lucheng City, the typical hilly area in the upstream, has little irrigation agriculture, and is relatively rich
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in water resource, and its annual precipitation is 503.7 mm and water per person is 3,652 m3. But
Xinxiang County, the typical plain area in the downstream, with annual precipitation 548.3 mm and with
306 m3 water per person (2006), has much irrigation agriculture, and needs plenty of water from Yellow
River diversion project and exploitation of underground water.
2 Estimate methods of ANPSP
A lot of methods have been used to estimate ANPSP, and these methods can divide into four main types:
(1) the first type is based on models, e.g. SWAT Model, AGNPS Model, HSPF Model[2] et al.; (2) the
second type is hydrological estimate of storm runoff[3]; (3) the third type is simple estimate based on
statistical investigations[4]; and (4) the forth type is coefficient output method[5]. After reviewed these
methods, we explored the fast estimate method of ANPSP, and analysis the potential pollution loads of
agricultural non-point sources. The detail algorithms are as follows:
2.1 Pollution for crop farming
Potential pollution loads of crop farming are the losing nitrogen and the losing phosphorus in soil
through rainfall, irrigation eluviation or runoff, due to over applying chemical fertilizers. To estimate the
ANPSP of crop farming in Zhangweinan Basin, the potential pollution loads of crop farming are
calculated by formula (1) and formula (2):
TNp=Ns+Nn+Nd-Np-Nv
(1)
TPp=Ps+Pn-Pp
(2)
Where TNp is total nitrogen potential pollution load of crop farming, Ns is the content of soil nitrogen
before fertilized, Nn is the amount of fertilizers used in the very year, Nd is the amount of atmospheric
nitrogen wet deposition, and Np is the amount of nitrogen absorbed by crops, calculated by multiplying
crop yield with the amount of nutrient absorbed by per unit crops. The numbers of nutrient absorbed by
per unit crops refer to the data of nutrient absorption of economic yield of main crop published by
Agricultural Ministry. Nv is the content of ammonia volatilization, calculated from the rate of nitrogen
fertilizer used, in this paper, the proportion of ammonia volatilization is 33%. TPp is the total
phosphorus potential pollution load, Ps is content of soil phosphorus before fertilized, and Pp is the
amount of phosphorus absorbed by crops.
2.2 Pollution for livestock and poultry breeding
Pollution for livestock and poultry breeding is expressed by the chemical oxygen demand (COD) of
nitrogen and phosphorus in the livestock’s dung and urine and their emission. The potential pollution
load of livestock and poultry breeding is calculated by formula (3):
BTN=(Bn× 1-A ×B)×Cn
BTP=(Bn× 1-A ×B)×Cp
BCOD=(Bn× 1-A ×B)×CCOD
(3)
Where BTN is the total nitrogen potential pollution load of livestock and poultry breeding, BTP is the
total phosphorus potential pollution load, BCOD is the COD potential pollution load, Bn is the number
of livestock, A is the percentage of manure disposal of farms, B is the excretion coefficient of feces of
livestock, and Cn, Cp, CCOD are the total nitrogen, total phosphorus, and mean COD per unit feces,
respectively.
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2.3 Rural Domestic pollution
Rural domestic pollution is one of the unneglectable factors of ANPSP. We use emission coefficient
method to estimate the rural domestic wastewater pollution load in the Zhangweinan Basin, and the
pollution load is calculated by multiplying population with domestic wastewater emission coefficient.
And the emission coefficient of COD is 16.4 g per person per day, the emission coefficient of total
nitrogen is 5 g per person per day, and the emission coefficient of total phosphorus is 0.44 g per person
per day.
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3 Assessment on potential pollution load (PPL) of agricultural non-point source
(ANPS)
3.1 Estimates of potential pollution load (PPL)
3.1.1 Pollution for crop farming
The PPL per unit area and TPPL of ANPS were estimated for each type of cropland in Lucheng City and
Xinxiang County (Table 1, Table 2, Table 3 and Table 4), using the datasets of sown area, grain output,
as well as the amount of fertilizer application, wet deposition of atmospheric nitrogen and volatilization
of ammonia nitrogen of the two locations in 2007.
Crop
Table 1 The potential pollution load (PPL) of total N of crop farming in Lucheng City, 2007
Ns (kg/ha)
Nn (kg/ha) Nd (kg/ha) Np (kg/ha)
Nv(kg/ha) PPL(kg/ha)
TPPL(t)
Wheat-corn
2121
626
24
94
208
2468
6823
Corn
2121
130
24
167
43
2065
33674
Millet
2121
1486
24
410
495
2726
890
Legume
2121
834
24
132
278
2569
979
Potato
2121
1193
24
25
397
2915
1079
Cotton
2121
779
24
130
397
2397
860
Total
——
——
——
——
——
——
44304
Crop
Table 2 The potential pollution load (PPL) of total P of crop farming in Lucheng City, 2007
Ps (kg/ha)
Pn (kg/ha)
Pp (kg/ha)
PPL(kg/ha)
TPPL(t)
Wheat-corn
32
1054
43410
1047
2894
1
Corn
32
P fertilizers are not used.
——
——
Millet
32
1246
5670
1158
378
Legume
32
874
4995
875
333
Potato
32
1366
7710
1389
514
Cotton
32
1157
6165
1144
411
Total
——
——
——
——
4529
Table 3 The potential pollution load (PPL) of total N of crop farming in Xinxiang County, 2007
Crop
Ns(kg/ha)
Nn (kg/ha) Nd (kg/ha) Np (kg/ha) Nv(kg/ha) PPL(kg/ha)
Winter wheat-corn
2234
377
24
411
35
2188
TPPL(t)
2234
379
24
372
35
2229
2111
Cotton
2234
185
24
162
17
2262
7998
Winter wheat-peanut
2234
301
24
551
28
1979
4362
Total
——
——
——
——
——
——
48154
Table 4 The potential pollution load (PPL) of total P of crop farming in Xinxiang County, 2007
Crop
Ps (kg/ha)
Pn (kg/ha)
Pp (kg/ha)
PPL (kg/ha)
TPPL(t)
Winter wheat-corn
57
122
169
11
166
Winter wheat-paddy
1
33682
Winter wheat-paddy
57
675
172
According to field survey in Lucheng City.
305
560
531
Cotton
57
466
57
466
1648
Winter wheat-peanut
57
680
153
584
1287
——
——
——
——
3633
Total
3.1.2 Pollution for livestock and poultry breeding
The PPLs of livestock and poultry breeding were calculated for Lucheng City and Xinxiang County
according to Formula 3 (Table 5).
Table 5 The pollution loads for livestock and poultry breeding in Lucheng City and Xinxiang County, 2007
Pig
Cattle
Sheep
Chicken
Duck
Total
Livestock
XX
LC
XX
LC
XX
LC
XX
LC XX
LC
XX
LC
COD(t)
1953
876
5212
5075
219
445
5318
2475
120
193
13822
9064
Total N(t)
331
148
794
1249
206
75
1163
541
28
46
2523
2060
Total P(t)
125
56
212
206
78
28
635
295
16
26
1065
612
3.1.3 Rural domestic pollution
The PPLs of rural domestic pollution were estimated for Lucheng City and Xinxiang County according
to the method illust
rated in Section 2.3 (Table 6).
3.1.4 Total potential pollution load (TPPL)
Of the agricultural non-point source pollution loads in Lucheng City in 2007, the PPL of total N is 46
855 t, while the PPL of total P is 5 604 t, and the PPL of COD is 14 868 t. Of the agricultural non-point
source pollution loads in Xinxiang County in 2007, the PPL of total N is 50 262 t, while the PPL of total
P is 4 292 t, and the PPL of COD is 10 862 t.
Table 6 The total potential pollution load (TPPL) of agricultural non-point sources
Total N (t)
Total P (t)
COD (t)
Source
LC
XX
LC
XX
LC
XX
Crop farming
44304
Livestock and poultry breeding
2523
48154
2060
Rural domestic pollution
28
48
Total
46855
50262
4529
1065
3633
612
——
13822
——
9064
10
48
1046
1798
5604
4292
14868
10862
3.2 Component analysis and source analysis of pollution load
3.2.1 Component analysis of pollution load
Component analysis shows that (Fig. 1 and Fig. 2), the PPL of total N contributes as the main
component, accounting for 69.59% and 76.83% of the TPPL in Lucheng City and Xinxiang County,
respectively. Secondary to total N, the PPL of COD accounts for 22.08% and 16.60% of the TPPL,
respectively, whereas the PPL of total P accounts for 8.23% and 6.56% of the TPPL, respectively.
3.2.2 Source analysis of pollution load
Source analysis of agricultural non-point source pollution load in the two typical counties shows that,
the PPL of COD mainly origins from livestock husbandry, accounting for 92.96% and 83.45% of the
TPPL in Lucheng City and Xinxiang County, respectively, followed by that from rural domestic
wastewater. The PPL of total N mostly derives from planting industry, accounting for 94.56% and
95.81% of the TPPL, respectively, whereas the livestock and poultry breeding and rural domestic
pollution contribute trivial part to the TPPL (Fig.3 and Fig.4). With respect to total P, planting industry
emerges as the main source of the PPL, accounting for 80.82% and 84.63% of the TPPL, respectively,
followed by livestock husbandry and rural domestic pollution (Fig. 5 and Fig. 6).
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COD
22.08%
COD
TP
TN
TP
8.32%
TN
69.59%
TP
6.56%
COD
16.60%
TP
TN
76.83%
COD
TN
Fig. 1 Component analysis of agricultural non-point
source pollution load in Lucheng City
Fig. 2 Component analysis of agricultural non-point
source pollution load in Xinxiang County
BTN
4.10%
PTN
0.06%
BTN
5.38%
PTN
0.10%
TNp
94.56%
TNp
BTN
TNp
95.81%
TNp
PTN
Fig.3 Source analysis of TN load in Lucheng City
PTN
Fig.4 Source analysis of TN load in Xinxiang County
PTP
1.12%
BTP
14.25%
PTP
0.18%
BTP
19.00%
BTN
TPp
80.82%
TPp
84.63%
TPp
BTP
PTP
Fig. 5 Source analysis of TP load in Lucheng City
TPp
BTP
PTP
Fig. 6 Source analysis of TP load in Xinxiang County
3.3 Pollutant discharged into rivers
According to Assessment on Water Resources in the Haihe River Basins, the discharge coefficient of
agricultural non-point source pollution (ANPSP) is assumed to be 0.05~0.06. However, field survey in
Lucheng City and Xinxiang County showed that, due to the scarce rainfall in 2007, the amount of
surface runoff is extremely small, resulting in little sewage flux besides wastewater from livestock farms
in the drain. In addition, the drain functions as a closed system during dry seasons and the sewage
seldom flows into the riverway. Therefore, we assumed the discharge coefficient to be 0.5, and
quantified the pollutant discharge amount for Lucheng City and Xinxiang County. The discharge
amounts of total N for the two counties are 234 t and 2 513 t, respectively, while those of total P are 280
t and 215 t, respectively, and those of COD are 743 t and 543 t, respectively.
4 Conclusion
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In this paper, we investigated the agricultural non-point source pollution (ANPSP) in the Zhangweinan
Sub-catchment and analyzed the components and sources of potential pollution load (PPL) in two
typical counties. Component analyses show that the PPL of total N is relatively high compared to other
pollutants, accounting for c.a. 70% of the total potential pollution load (TPPL) of agricultural non-point
sources, while the PPL of COD occupies another 20%. With respect to the pollution sources, the PPL of
COD mainly derives from livestock husbandry, accounting for more than 80% of the TPPL of COD,
whereas the PPLs of total N and total P mainly origin from planting industry, accounting for more than
90% and 80% of the TPPLs, respectively.
—
Biography: Luo Zunlan(1979 ), female, Associate professor, mainly engaged in non-point source
pollution, water resource and environment.
Supported by found GEF Hai River Basin IWEMP IWEMPSAP TF053183 .
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References
[1]. Wang Liqing, Yu Weidong. Study on Water Resource and Environment Problems in Zhangweinan
Basin. HAIHE WATER RESOURCES, 2008, 10 : 6~8.
[2]. Hu Xuetao, Chen Jining, Zhang Tianzhu. A Study on Non-Point Source Pollution Models.
ENVIRONMENTAL SCIENCE, 2002, 23 3 : 124~128.
[3]. CHENYou-yuan,HUI Er-qing,JIN Chun-ji et. A Hydrological Method for Estimation of Non-Point
Source Pollution Loads and Its Application. Research of Environmental Sciences, 2003, 16(1):
10~13.
[4]. WANG Xiao-yan, WANG Yi-xun,CAI Xing-guang et. Investigation of Non-point Pollution in
Watershed of Miyun Reservoir. Environmental Science and Technology, 2002,25 4 1~4.
[5]. LI Gen, MAO Feng. Evaluation on Non-Point Source Pollution of Soil and Water Loss and Its
Econom ic Loss of China. SOIL AND WATER CONSERVATION IN CHINA, 2008, 2 : 9~12.
[6]. Su Fang, Ding Xinquan, Gao Zhiling et. Ammonia volatilization from nitrogen fertilization of
winter wheat-summer maize rotation system in the North China Plain. China Environmental
Science, 2007, 27(3):409~413.
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