agriculture yongding river

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Ecological Indicators 36 (2014) 254261

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Original Articles

Agricultural non-point source pollution in the Yongding River Basin

Wenxian Guo a , b , Yicheng Fu b , , Benqing Ruan b , Huaifeng Ge c , Nana Zhao ba North China University of Water Resources and Electric Power, No. 36 Beihuan Road, Zhengzhou 450045, P.R. Chinab State KeyLaboratory of Simulation and Regulation of River Basin Water Cycle, China Institute of Water Resources and Hydropower Research,A-1 Fuxing Road Haidian District, Beijing 100038, P.R. Chinac China RenewableEnergyEngineering Institute, No.2 Liupukang Street Xicheng District, Beijing 100120, P.R. China

a r t i c l e i n f o

Article history:Received 18 October 2012Received in revised form 10 July 2013Accepted 11 July 2013

Keywords:Agricultural non-point source pollutionESINitrate lossAmmonium salt lossPhosphorus lossThe Yongding River Basin

a b s t r a c t

More and more nitrogen and phosphorus chemical fertilizers are applied inthe upstream of the YongdingRiver Basin. With the aid of convertibility between emergy and value, the calculated ESI (EnvironmentalSustainability Index) of basin agricultural production is 0.1056, indicating that local agriculture is seri-ously unsustainable. According to the different combining types of nitrate and ammonium salts with soilparticles, soil nitrogen losses under the inuence of rainfall-runoff are quantitatively evaluated from theperspective of the nitrogen cycle. By virtue of the content of dissolved and particulate phosphorus in soil,the calculation process for soil phosphorus loss is modeled according to the eld runoff volume. The totalnitrogen and total phosphorus losses from soil are 96 kg hm 2 and 9 kg hm 2 , respectively. The calcula-tion result of nitrogen and phosphorus losses in the basin is certainly reasonable. Finally, the researchemphasis of calculation method for reducing basin agricultural non-point source pollution is representedfrom management level.

2013 Published by Elsevier Ltd.

1. Introduction

Agricultural non-point source pollution is mainly caused by thenitrogen and phosphorusfertilizers, pesticidesand otherorganic orinorganic nutrients leaked with eld surface runoff or agriculturalwastewater discharge. Rainfall runoff is the power to produce agri-cultural non-point source pollution load as well as the carrier totransport pollutants and decide pollutant types and accumulationquantity ( Liu et al., 2009 ). Agricultural non-point source pollutionhas the features of asymmetric information, high uncertainty, ran-domness, moral hazard, adverse selection and so on ( Liu et al.,2008 ). Thecontrol ofagricultural non-pointsource pollutionis dif-cult tobe quantiedas itis involvedwitha wide rangeof inputs, andthe control process has many randomness and strong uncertainty.The balance method, additional calculation method, probabilisticmethod, analogy method, model simulation and other methodswere adopted to calculate pollutant load in previous study ( Yu andLiu,2009 ). However, the impact of soilproperties, fertilizerresiduesin arable land and eld rainfall runoff is less considered.

Agricultural non-point source pollution has obvious geographi-calfeaturesand is impacted by soil types,land usetypesand terrainconditions. So far, there is no mature and standardized method toquantify pollutant load ( Zhang et al., 2004; Zhang et al., 2009 ).

Corresponding author. Tel.: +86 10 68781699; fax: +86 10 68781990.E-mail address: [email protected] (Y.C. Fu).

With the digital technology, scholars have studied agriculturalnon-point source pollution produce load by virtue of geograph-ical sub-blocks. Yan (2008) studied the source distribution of theYellowstone agricultural non-point source pollutionand the differ-ential distribution in space with analytical methods andprovided atheoretical basis to reduce agricultural non-point source pollution.Lei and Huang (2007) gave the key areas of agricultural non-pointsource pollution with the spatial analysis model GIS and suppliedrisk assessment of agricultural non-point source pollution. Withthe intensive study on the inuencing factors of agricultural non-point source pollution, scholars attempted to conduct quantitativeanalysis of agricultural non-point source pollutants in land-uselevel. Inuence evaluation of management practices, climate, andsoil different properties on nitrogen and phosphorus leaching hasbecome the focus of agricultural non-point source pollution con-trol. The simplied qualitative or semi-quantitative calculationmethod for nitrogen loss index has appeared. For example, in theNetherlands, scholars have calculated and compared nitrogen lossindicators for different types of land use ( De et al., 2007 ); in France,a method, known as Manipulation Receiver, has been used toanalyze the output diversity of nitrogen loss in different elds(Bockstaller et al., 2008 ). Agricultural non-point source pollution isclosely linked with water cycle. Therefore, the hydrological modelhas been widely used to estimate the impact of nitrogen and phos-phorus loads and agricultural productionactivities fromthe view of water quantity and quality. For example, USLE is used for estimat-ing annual soil loss and DANSAT is used to simulate the temporal

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W.X. Guo et al./ Ecological Indicators 36 (2014) 254261 255

R

F N

ESI=5

ESI=1

Fullysustainable

Sustainable

Unsustainable

Fig. 1. Agricultural production sustainability state. R is on behalf of renewableresources; N , non-renewable resources; and F , economic input of environmen-tally friendly production. ESI is environmental sustainability index), and ESI =( R+ N + F F )/ (

N + F R ). In thegure, thesustainability linesdepartfrom the N apex in direc-

tion leading to the RF side allowing the division of the triangle into sustainabilityareas, which are very useful to identify and compare the sustainability of productsand processes. Theupper part of thediagramshows theregion (ESI > 5), wheresys-tems aresustainable; the middle part marks theregion (1< ESI< 5),wheresystemsare sustainable for the medium term, and the lower part of the diagram shows aregion (ESI< 1), where systems are not sustainable ( Giannetti et al., 2006; Almeidaet al., 2007 ).

and spatial variation of soil erosion and pollutant emission charac-teristics. In model simulation estimation of the amount of nitrogenand phosphorus losses, starting from hydrologic simulation, theinuence of optimalmanagementpractices and surface and groundwaterconjunctive management on non-pointsource pollutantsarealso emphasized in basin scale. However, nitrogen and phospho-rus losses have not been essentially described from the combinedaspects of soil, pollutants, and hydrological characteristics.

Agricultural non-point source pollution is complex for com-prehensive multi-factors. According to contaminant informationaccessibility and water quality inuence degree, pollutant loadbasedon agricultural non-point source pollutants leaching is quan-titatively analyzed. The study foundation is agricultural fertilizer

application. The agricultural production is not sustainable in theYongding River Basin,and theESI is 0.1056. Theoverallloss of nitro-gen and phosphorus is 96kg hm 2 and9kghm 2 , respectively. Thereliability of thecalculation resultof basin nitrogen andphosphoruslosses is elaborated with management status.

2. Materials and methods

The purpose of agricultural production is to fulll the maxi-mum agricultural production and ecosystem service value withthe smallest investment in environmental protection. Wheat, corn,soybeans, peanuts, cotton, fruits and vegetables are chosen in thispaper to study emergy of products and ecological services. Accord-ing to thecalculateddataof ESI (EnvironmentalSustainability Index

for the management of agricultural output andenvironmental load,in which it is assumed to obtain the largest production with theminimum of environmental damage), the sustainable developmentdegree of basin agricultural production is proposed. The triangleemergy representation in the study area is shown in Fig. 1 .

The losses of nitrogen and phosphorus in agriculturalnon-pointsource pollution are the main reason causing eutrophication of lakes, reservoirs and other water bodies. During rainstorms, a lotof dissolved or adsorbed nutrients enter water with the farm-land surface drainage and sediment. Model estimation of N andP losses from farmland fertilizer is not only the effective controlfarmland non-point source pollution, butalso the basis for improv-ing the quality of cultivated soil. In this paper, based on ArcGISspatial analysis, we identied the priority control areas of agricul-

tural non-point source pollution, the control object, the research

Table 1Thefarmland area (hm 2 ) in Yongding River Basin.

Water resourceregionalization

Administrative region Farmland

Province City

The upstream of CetianReservoir in theYongding River Basin

Shanxi Datong 102,709

Shuozhou 206,105Xinzhou 2706

Total 311,520BetweenCetian Reservoir

and Sanjiadian in theYongding River Basin

Hebei Zhangjiakou 257,069

Shanxi Datong 114,881Total 371,950

The Yongding River Basin 683,470

scale,and diversity in regionalizationpurposes and calculatedtotalnitrogen (TN) loss and total phosphorus (TP) loss in chemical fer-tilizer application as according to the model of non-point sourcepollutants.

In the view of the previous model parameter randomnessand monitoring data inaccessibility, inspired by carbon balanceproposedby Suzuki et al. (1993) , we conductedcalculation unitpar-tition according to regional water resource management principle.According to the coefcientdifferences of nitrogen and phosphoruslosses under different land-use types, pollutant losses are calcu-lated with the combination of changes of soil, crop and residuescharacteristic in time andspacelevel( Siet al.,2000 ). With thechar-acteristics of distributed parameters, physical basisand continuoussimulation of the dynamic assessment model of agricultural non-point source pollution ( Jaepil Cho and Saied Mostaghimi, 2009 ),the loss calculation method for farmland fertilization is proposedaccording to the characteristics of soil moisture and the continu-ous impact of nitrogen and phosphorus. To avoid the inuence of parameteruncertainties, the migrationand transformation mecha-

nismof agriculturalnitrogen andphosphorus pollutants is analyzeddeeply with the aid of digital technologies.

Although the nutrient balance of the Yongding River Basin ispositive, with nitrogen and phosphorous losses due to extensiveplanting permanentcrops, degradation of soilquality mayoccur. Asa result, the balance state of soil andwaterbody would be damagedand the regional sustainable development would be destroyed. Sothe nitrogen and phosphorous losses are the key indicators to real-ize the sustainable development of watershed agriculture. Withagricultural activities and the increasing ecological impact, agri-cultural nutrition pollution has become the dominant factor of affecting watershed water quality sustainability.

2.1. Study area

In the view of the accuracy of research data, the upstream of Guanting Reservoir Basin of the Yongding River is selected as thestudy area. A schematic map of the main components of the studyarea is presented in Fig. 2 . The upstream area of Guanting reser-voir of the Yongding River is 37,062km 2 and Shanxi Province andHebei Province, respectively, account for 52% and 48%. In the viewof thedistribution of administrativeregion in the basin area, Zhang- jiakou City in Hebei Province, as well as Datong, Shuozhou andXinzhou City in Shanxi province are the main cities ( Yi-cheng Fuet al., 2012 ). In order to nd out the net nitrogen and phosphoruslosses during agricultural production and farmland management,crop pattern and plant area of the agricultural zones in the studyarea is required. Table 1 shows the plant area of the agricultural

zones in the Yongding River Basin. Accounting for about 98% of the


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256 W.X.Guo et al./ Ecological Indicators 36 (2014) 254261

Fig. 2. Yongding River Basin study area location.

total basin area, the 4 cities are the main affected area of the water-shed ecology. The study area has the main eld crops includingmaize(corn) andwheat andthesame plantingpattern andarea. TheYongding River Basin has lumped corn and wheat crops together,so we can not analyze the differences in fertilizer application at thesingle crop level. The area has less crop rotation because of water

shortage and infertile soil.Agriculturalproductionof thearea is more developedwith large

amount of chemical fertilizer application. Since the implementa-tion of the First Water Planning in study area, municipal sewagetreatment plants have been constructed and effectively reducedpoint source pollution load discharged into the rivers. In recentyears, water quality data of the automatic detection section of the watershed showed that excessive nitrogen had become animportant restriction factor in improving watershed water qual-ity. Contaminants have an important impact on watershed aquaticecosystem. Water quality grade degradation of basin upstream islargely related with nitrate leaching from farmland soil. Non-pointsourcenitrogenemissions have becomethe leading cause of water-shed water quality deterioration.

Annual precipitation in the basin is about 450mm. In the paper,precipitation is considered as a control constant in the wholeYongdingRiverBasin toreduce calculation errorof nutrimentlossesresulting from regionalization runoff amount distribution disequi-librium. For the area lacks of rain and irrigation infrastructures,agricultural production is in severe water shortage. The averageannual precipitation is far from the soil eld capacity in a shorttime. Precipitation is generally used to meet the demand of earlysoil loss, and it is difcult to form surface runoff. The loss of agri-cultural nitrogen andphosphorus is in positive correlation with therainfall and mainly occurs in wet one with rainfall and soil erosion.Considering the discretization of the rainfall, we jointly apply theconversion type of rainfall runoff and storm management model.According to the basic forming principle of rainfall runoff, we gen-

eralize farmland into permeable areas to deduce the runoff loss

of eld fertilization. The entirety slope of Yongding River Basin is2.5 , which is small in the vast mountainous area. Although itpromotes soil erosion in response to every rainfall event duringthe growing season, in the paper, the variable impact of slope isnot considered during the calculation of nitrogen and phosphoruslosses for the similarity of geographic landscape and geomorpho-

logy parameter.

2.2. Nitrogen loss calculation

Nitrogen fertilizer accounts for more than 50% of the nitratepollution sources in surface water. 20 30% farmland nitrogenapplication are excessive nationwide; the loss of nitrogen fertil-izer by underground leakage and farmland drainage and stormrunoff are10% and 15%, respectively ( Ren etal.,2010 ). The loss wayof nitrogen mainly includes ammonia volatilization (loss rate ashigh as 40 50% of nitrogen quantity), nitrication-denitricationloss (loss rates of 16 41% and 15 18%, respectively), leaching andrunoff loss. Exchangeable ammonium and nitrate in soil are bothavailable nitrogen directly absorbed by crops.

2.2.1. Ammonium salt lossNitrogen cycle under the joint action of the natural and human

factors should include a number of biological processes involvingvarious environmental factors. The nitrogen cycle under naturaland human inuence has a closed loop path in the transferringform of solid, liquid and gaseous states. With regard to the con-version and loss characteristics of ammonium salt, we calculatedammoniumsalt lossesbased on soil-water content and ammoniumsalt concentration. The loss of ammonium salt in soil is related toprecipitation, water inltration depth, specic sediment yield andfarmland displacement ( Xu and Liu, 1999 ).

Based on the nitrogen cycle model in the constructional regionof nitrogen balance in natural ecosystems, the transport and trans-

formation of the nitrogen in the terrestrial biosphere is simulated.


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The cycle balance model of ammonium salt is shown as follows:

DELTA N/ DELTA t = N dm + N hm + N amm N uptakeN amm

N amm + N nit N nitrif N v ola + fert amm (1)

where, N amm refers to the amount of nitrogen deposition in ammo-nium salt (tkm 2 d 1 ); N dm refers to the amount of the nitrogentransfer in the gravel mineralization process (tkm 2 d 1 ); N hmrefers to the amount of the nitrogen transfer in the humus min-eralization process (tkm 2 d 1 ); N uptake refers to crop nitrogenuptake (tkm 2 d 1 ); N nit refers to the nitrogen deposition includein the nitrate salt (tkm 2 d 1 ); N nitrif refers to the nitrate transferamount (tkm 2 d 1 ); N vola refers to the volatilization of ammo-nia (tkm 2 d 1 ); fert amm refers to the ammonium salt amount infertilizer (t km 2 d 1 ); the time step of t is 1day.

The Langmuir isotherm and two-phase equilibrium state of adsorption and dissolution of ammonia and nitrogen were coupledtodescribethe changeof ammoniumnitrogenin soil ( Vanon, 1975 ).For the combination of the balance equation of ammonium salt insoil, the loss formula of the ammonium salt with surface drainageis shown as follows:

W NH +4 N = (10 6

Ss + 10 3

r R ) A (2)

where:

r = h + P 1

h + P (3)

where, W NH4 +-N is the amount of the ammonium salt loss fromfarmland (t); a is the content of ammonium salt in soil solution(mg L 1 ); S s is the specic sediment yield (tkm 2 ); a r is the con-centration of ammonium salt of runoff (mg L 1 ); is the content of absorbed ammonia nitrogen (ugg 1 ); is soil-water content; h isthe mixture depth of water inltration (mm); a 1 is the concentra-tion of ammonium salt in rainwater (mg L 1 ); P is rainfall (mm); Rais displacement from farmland (mm); A is drainage area (km 2 ).

According to the difculty of content calculation of ammoniumsaltin soilsolution,the solutionformulacombinedwith thebalanceequation of ammonium salt in soil was represented as follows:

=K e

10 3 0

0(4)

where, K e is thecontent of ammoniumsaltin soil ( ug cm 3 ); issoildensity (gcm 3 ); 0 is soil wilting water content (%); 0 is waterdensity (g cm 3 ).

2.2.2. Nitrate lossNitrate is the main form of inorganic nitrogen of damp soil, cin-

namon soil, sandy soil and saline soil ( Ding et al., 2001 ). The annualleaching loss of nitrate in the rotation system of winter wheat and

summer maize in northern China is 136 kghm

2 , which is about20.3% of the total nitrogen inputs ( Zhao et al., 2009 ). The nitrateleaching is estimated according to fertilizer utilization of differ-ent types of land use. Soil nitrication and denitrication activityis closely related to soil properties. Studies have shown that thenitrate leaching is related to soil-water content, soil structure andthe concentration of nitrate.

Studies have shown that nitrication ( NITRIF ) in soil can beexpressed with a function of soil-water content ( f NIT,SW (W S )), tem-perature ( f NIT,T (T )) andthe concentration of ammoniumsalt( N amm ),which are signicantly affected by soil-water content, soil aerationporosity degree, total nitrogen content and C/N ( Shi et al., 2009 ).With f NIT,T (T ) of exponention notation, the changes between theaverage soil temperature ( Q 10,NIT ) of 2 C and the optimum soil

temperature ( Q opt,NIT )o f20

C; f NIT,SW (W S ) is assumed to be related

linearly to soil-watercontent; uNIT representsrate constantof nitri-cation, dened as 0.003 d 1 in this paper. Calculation formula of nitrication quantity is as follows:

NITRIF = NIT f NIT,SW (W S) f NIT,T (T ) N amm

f NIT,T (T ) = Q (T T opt,NIF )/ 10)10 ,NIT

f NIT,SW (W S) =1 .17

W S

W FC + 0 .165 W S < W FC

1 .0 0 .1W SW FC

W S W FC

(5)

Anti-nitrication ( DENITR) is driven by various types of anaero-bic bacteria. We use a function of soil-water content ( f DENI,SW (W S ),temperature ( f DENI,T (T )) and nitrate available ( Nnit ) in soil tomodelthe process. uDENI is the rate constant of denitrication, dened as0.0015d 1 in this paper. The calculation formula of denitricationamount is as follows:

DENITR= DENI f DENI,SW (W S) f DENI,T (T ) N nit f DENI,T (T ) = Q (T T opt,DENI )/ 10)10 ,DENI

f DENI,SW (W S) =0 W S W FC

1 .0W SW FC W S > W FC

Soil deposition of nitrogen ( DEPO) mainly includes two kinds:deposition nitrogen of ammonium salt ( DEPOammd ) and depositionnitrogen in nitrate ( DEPOnitd ). The calculation formula is as follows(Bin-Le Lin et al., 2000 ):

DEPOammd =13

Rrain + RDEPO,dry,ammd

DEPOnitd =23

Rrain + RDEPO,dry,nitd

(7)

where, Rrain refers to the potential concentration of ammoniumsalt and nitrate in the water (kg hm 2 a 1 ): tropical forests (1.77),temperate forests (1.08), boreal forest (0.55), and arable/grassland(1.0); RDEPO,dry,Amm refers to ammonia deposition in dry region(kg hm 2 a 1 ); RDEPO,dry,Nit refers to nitrate deposition in dry region(kg hm 2 a 1 ).

Suppose the vertical movement of nitrogen occurs in the top2 meters of the soil layer. K is a parameter termed as hydraulicconductivity, which can be calculated according to the Brooks andCorey Equation with the soil parameters ( Maidment, 1992 ). Thesolution calculation of nitrate leaching loss, LEACH, is as follows:

LEACH = K C Nit

2 (W S/W FC )

K = K s.leach ( r

r )3+ 2 (8)

where, K s,leach is the hydraulic conductivity of the fully saturatedsoil, dened as 2.55cm h 1 in this paper; is soil-water content in 33kPa, dened as 0.273 cm 3 cm 3 ; r is moisture content involv-ing the soil, dened as 0.075; is the total porosity, dened as0.442 cm 3 cm 3 ; is the series of pore size distribution.

2.3. Phosphorus loss calculations

The phosphate fertilizer utilization ratio by crops is low, onlyabout 10% and generally no more than 25%. As a result, about75 90% phosphate fertilizer is retained in soil ( Wang and Li,1999 ). The current loss of phosphate fertilizer in soil mainlycontains twoforms of dissolved andparticulate states. Consideringsoil properties, initial soil-water content, surface soil seasonally

variable parameters and land geometry traits ( Sharpley et al.,


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1995 ), the calculation methods for phosphorus concentration wasrepresented as follows:

TDP =K Pav D B ( t )a wb

V

TPP = TP E PER(9)

where, TDP is the concentration of dissolved phosphorus in soil(mg L 1 ); TPPis the concentration of particulate phosphorus in soil(mg L 1 ); Pav is the phosphorus content of available soil (mg m 3 );K, a and b are the kinetic parameters related to soil clay and organiccarbon content, a and b are thecoefcientand theexponent,respec-tively ( Leone et al. , 2008 ); D is the efcient depth (mm) of theinteraction between phosphate fertilizer and soil; B soil bulk den-sity (mg m 3 ); t is the period length (min); w is the proportion of water and soil in runoff (Lg 1 ); V is the total runoff (mm); TP is thetotal phosphorus content in soil (mg L 1 ); E is sediment concentra-tion (gL 1 ); PER is the enrichment rate of phosphorus in soil (g 1 ).

It is the key to effectively estimate the rainfall runoff inphosphate loss calculation. To avoid the inltration loss of farm-land runoff, the Horton inltration mechanism was introducedto describe the transformation between the rainfall runoff. Theground in the model is divided into pervious surfaces and impervi-

ous surfaces to calculate runoff. The calculation formula of runoff by permeable surface is as follows:

v rp = 0 v sdp + siw + f c /

v sdp siw f c / v > s dp + siw + f c /(10)

where, v is the rainfall (mm); S dp is the depression storage capacity(mm) of inltration area; S iw is initial soil inltration loss (mm) of permeable surface; f c is stable inltration rate (mm h 1 ); is thereciprocal of average rainfall duration (h 1 ).

3. Results and discussion

3.1. Agricultural sustainable situation

By virtue of correlation and cluster analysis, we calculated thearable land of different calculation units in the study area with thestatistical analysis function of GIS, as illustrated in Table 1 (Wedivided the calculation units according to basin water resourceregionalization and administrative region). In order to give fullconsideration to the impact of the crops on the loss of farmlandnutrients and on the surface underground runoff process, we stud-ied the loss of agricultural non-point source pollutants withina year. We calculated the index of ESI by transforming naturalresources, agricultural products and environment-friendly agri-cultural production economic input into emergy ow. Throughcombining the calculation result of emergy, fundamental quantityESI(the environmentalsustainabilityindex aggregatesthe measure

of environmental load. The objective function for sustainabilityis toobtain thehighest yieldratiowith the lowest environmental load) is0.1056, whichis farfrom5. Atpresent,emergysynthesis was widelyapplied to assess the environmental performance of agriculturalsustainable development situation in China, such as Fu Yichenget al. (2013) and Lu Hongfang et al. (2005) . The unit of emergy issolar emergy joules (seJ). During calculation process, we convertedrelated material and economic inputs of the agricultureproductioninto emergy ows. R, N and F represent renewable resources, asnon-renewable resources and inputs from the economy. Comparedwith the 15.83 10 24 seJ/year baseline, the transformity baselinevalue between emergy and energy is important ( Odum and Odum,2000 ). A detailed description of the emergy calculation processis elaborated by Fu Yicheng et al. (2013) . Therefore, unsustain-

able input or output accounts for a large proportion during basin

R

F N

ESI=5

ESI=1

0.17 R0.81 F

0.02 N

ESI=0.1056

increase

Fig. 3. Emergy ternary diagram representing the agricultural production systemof Yongding River Basin in 2007. The upper part of the diagram shows the region(ESI>5), where systems are sustainable for long term; the middle part marks theregion (1< ESI< 5), where systems aresustainablefor medium term, and thelowerpart of thediagram shows a region (ESI


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Table 2The ammonium salt loss amountof agricultural non-point sourcepollution in the YongdingRiverBasin.

Water r esource r egionalization Administrative r egion Content o f NH4 +-N(10 6 g cm 3 )

Solution content of ammonium salt(10 3 g L 1 )

Content of NH 4 +-N in soilparticles adsorption(10 6 g cm 3 )

Loss amount of ammoniumsalt (t)

Provinces Cities

The upstream of CetianReservoir in the YongdingRiver Basin

Datong 1136 109 337 9808Shanxi Shuozhou 1136 109 337 28,627

Xinzhou 1135 109 337 590Total 39,025

Between Cetian Reservoir andSanjiadian in the YongdingRiver Basin

Hebei Zhangjiakou 581 35 144 4055Shanxi Datong 1136 72 247 8772

Total 12,827The Yongding River Basin 51,852

nitrogen in soil ( He et al., 2010 ). According to previous studies(Sun and Wang, 1995 ), nitrogen runoff loss is related to nitrogenapplication amount of different soil properties: when the nitrogenapplication rate of sandy loam is 160 kghm 2 , the total runoff lossis approximate 135.7kg hm 2 . The nitrogen application amount inthe Yongding River Basin is 195kg hm 2 and the nitrogen fertil-izer losses are 96kg hm 2 . So the result is reasonable. The nitrogennutrient loss from farmland is positively correlated with cumu-

lative runoff. Due to the diversity of fertilizer and improper useduring agricultural production in the Yongding River Basin, theoverall losses of nitrogen are 96kghm 2 , which is the same withthe national proportion of nitrogen loss. Due to high dependencyon nitrogen fertilizers and more extensive management in agricul-tural production, nitrogen depositionare relatively larger in ShanxiProvince and nitrogen losses are 137 kghm 2 . While ZhangjiakouCity in Hebei Province has increased its efforts in controlling agri-cultural non-point source pollution, so the nitrogen loss is only29kghm 2 .

3.3. Phosphorus loss

The losses of cumulative total phosphorus (TP) in YongdingRiver Basin runoff are up to 0.0439 2.0798 g.m 2 and the aver-age loss level during agricultural runoff is 2.67kghm 2 (Huanget al., 2003a,b ). Studies have shown ( Huang et al., 2003a,b )that surface runoff from agricultural eld in Yongding River hasbecome the potential pollution hazards to water body of reser-voirs. Accumulative bio-available phosphorus loss in runoff is upto 0.008 0.4804g m 2 and the bio-available phosphorus loss of agricultural runoff is up to 0.49kg hm 2 .

In the view of complexity and uncertainty of farmland phos-phorus loss calculation, we took different rainfall, agricultural landmanagement methods and research-scale into consideration torepresent the total phosphorus loss during agricultural productionin the Yongding River Basin. The results were illustrated in Table 4 .

The census data of the rst national pollution source shows

that agricultural pollution has become the primary factor to affect

chinawaterresourcesecurity.As a double-edgedsword, nitrogenand phosphorus of fertilizers applied during agricultural produc-tion should be fully utilized. Since surface growth of crops hascausedserious erosion on thearable land,90% phosphorus in runoff is in particulate forms. From 20cm below ground level up to thesurface, the total phosphorus content presents overall downwardtrend ( Chen et al., 2005 ). As a result, since soil mineral content isrelatively low in the Yongding River Basin, phosphorus fertilizer

application amount is relatively high in agricultural production,leading to a high surface runoff loss, 9kghm 2 . Organic mattercontent, clay content and particle size in sediments will directlyaffect the adsorption capacity of dissolved phosphorus such as Ca-P, Al-P and Fe-P. From the surface to the depth of 20cm in the soilin the Yongding River Basin, clay content of the sediment is grad-ually reduced and sand content is increased. Therefore, the totalphosphorus residues are increased. Rainfall runoff leads to a higheramount of phosphorus loss.

3.4. Discussion

In principle, there are two methods to calculate nitrogen lossamount of soil: determination based on the balance data of annualnitrogen input and output, and determination based on the mea-surement data of mineral nitrogen in soil before and after leachingstudyperiod.In this paper,on thebasis ofexcludinguncertain inu-encing factors, we have fullled the effective calculation of basinagricultural nitrogen loss data. In agricultural ecosystems, anthro-pogenic nitrogen application accounts for a large part, leading torelatively high nitrogen loss in the Yongding River Basin. On thebasis of generalization, we represented an overview of nitrogenloss index under different nitrogen application conditions in thebasin ( Table 5 ) and conrmed the reliability of the research resultsfrom application level.

Although crop daily uptake of phosphorus is lower, unit lengthof the root demands a relatively large daily amount of phosphorus(Schrder, 1999 ). Soil phosphate content is relatively low in the

Yongding River Basin with the majority of sandy loam and clay.

Table 3The nitrate loss amount of agricultural non-point source pollution in theYongding River Basin.

Water resource r egionalization Administrative r egion Soil-watercontent

Nitricationrate constant

Ammonium saltconcentration

NITRIF Loss amount of nitrate

Province City f NIT,SW (WS ) uNIT (d 1 ) t km 2 t km 2 d 1 t


Datong 1.101 0.003 1136 3.752 2494.000Shanxi Shuozhou 1.101 0.003 1136 3.752 5007.000

Xinzhou 1.101 0.003 1135 3.749 65.000Total 7566.000

Between Cetian Reservoir andSanjiadian in the YongdingRiver Basin

Hebei Zhangjiakou 1.101 0.003 581 1.920 3633.000Shanxi Datong 1.101 0.003 1136 3.752 2727.000

Total 6360.000The Yongding River Basin 13,926.000


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Table 4The phosphate fertilizer loss situation in agricultural runoff in the Yongding River Basin.

Water resource regionalization Administrativeregion

Total phosphatelosses (t)

Phosphorus loss amountper unit area(kghm 2 )


Datong City 1132 11Shanxi Shuozhou City 3088 15

Xinzhou City 60 22Total 4 281 14

Between Cetian Reservoir and

Sanjiadian in the YongdingRiver Basin

Hebei Zhangjiakou 747 3

Shanxi Datong City 1063 9Total 1810 5Total in the Yongding River Basin 6090 9

Table 5Overviewof nitrogen loss index reference.

Index source of nitrogen loss Calculation base Output data Limit value of nitrogen loss

Nitrogen balance All nitrogen input andoutput

Loss amount of nitrogen(kgha 1 a 1 )

60 (sand) 100 (clay)

Mineral nitrogen deposited in soil Measured data Loss amount of nitrogen ata xedtime(kgha 1 a 1 )

40

Nitrogen fertilizer application rate Datap rovided by growers Loss amount of nitrogen(kgha 1 a 1 )

170

Efciency of nitrogen fertilizer application Crop nitrogenuptake/nitrogen fertilizerapplication rate 100

Theoretical value

Leachingamount of crop residue nitrogen Nitrate concentration inleachate= 11.3mgL 1

Nitrogen leaching amount:10.5 (wet season) & 7.82(dry season) g nitrogen/kgdry matters

Nitrate leaching concentration>11.3

Thus high external inputs of phosphate fertilizer are applied dur-ing agricultural production. In acidic soils, phosphorus is easy tobe combined with iron, aluminum elements and colloids of soilparticles. However, less study on the migration rule of phospho-rus in alkaline soils ( Jalali, 2007; Lge et al., 2008 ) was reported. Forthe soil type of the Yongding River Basin is neutral or alkalescent,the loss of phosphorus in agricultural production is mainly based

on experimental data and lack of popularized basis. According tothe research results of OECD (Organization for Economic Cooper-ation and Development), the regional average phosphorus inputis 21kghm 2 a 1 , harvest or grazing output is 17kghm 2 a 1 andsoil phosphorus residue is 5 kghm 2 a 1 . Therefore, in the view of the advanced control technology of European agricultural practice,total phosphorus loss (9kg hm 2 a 1 ) of agricultural cultivation inthe Yongding River Basin is reasonable.

4. Conclusion

In thispaper, thedeterminant indicatorof ESIfor agro-ecologicalsustainability is 0.1056, indicating that agricultural production isnot sustainable in the Yongding River Basin. We modeled the cal-

culation method of loss amount for ammonium salt and nitratebased on the nitrogen cycle according to the soil structure andthe physical and chemical properties of nitrogen and phosphorus.With the calculation results of agricultural nitrogen and phospho-ruslossamountin theYongding RiverBasin, thepaper proposedthereliability analysis of the calculation results: (1) nitrogen fertilizerapplication is excessive for agricultural production in the YongdingRiver Basin, leading to the overall loss of 96kghm 2 nitrogen.However, the loss of nitrogen per unit area is only 29kghm 2 inZhangjiakou; (2) phosphorus fertilizer application in the basin ishigh during agricultural production and the loss per unit area is9kghm 2 .

The calculation method mentioned in this article can be appliedto calculate the loss amount of nitrogen and phosphorus in other

similar basins on the basis of the change the underlying surface

condition of the soil. Agricultural non-point source control modelis the basis of basin environmental assessment, environmentalmanagement, environmental policy simulation, etc. It is the meta-synthesis of geographical characteristics, crop characteristics andmanagement mode. The calculation model for agricultural non-point source pollutant has some applicability, but its parametersshall be classied by region. In this way, the control model of agri-

cultural non-point source with temporal and spatial selectivity canbe established.In the paper, we use a lot of non-linear functions to calculate

the loss of nitrogen and phosphorus. Some small changes of theinput variables may induce changes of the result values at dif-ferent scales. However, during nitrogen transformation processesbetween biosphere and atmosphere, this is difcult to give quan-titative sensitivity analysis to the parameters change caused byanthropogenic disturbances. At present, the nitrogen uxes weremodeled in conjunction with thecarbon uxes in organic-soilcom-partments. Therefore, to improve the structure of our nitrogen andphosphorus loss calculation model, the parameter calibrations andquantitativelyevaluatingthe potential impacts analysis willbe dis-cussed in our future work.

Acknowledgments

This work was conducted as part of the working group on thestudy on watershed ecological compensation theory, method andimplementation mechanism. The paper was funded by NationalNatural Science Foundation of China (Grant No. 50979114 and51209091).

Appendix A. Supplementary data

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.ecolind.2013.

07.012 .
http://dx.doi.org/10.1016/j.ecolind.2013.07.012http://dx.doi.org/10.1016/j.ecolind.2013.07.012http://dx.doi.org/10.1016/j.ecolind.2013.07.012http://dx.doi.org/10.1016/j.ecolind.2013.07.012


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