Comprehensive Evaluation of Optimal Environmental Policies about
Nitrogen cycle for Sustainable Development in China: Case Study ofSongYuan City.
Li’ang AN, Yoshiro HIGANO
Master program in Environmental Sciences, Tsukuba University
Abstract:
Nitrogen is precursor of environmental problem, which contributes to smog, acid rain
and global warming. Anthropogenic input can result in nitrogen saturation, whichbroken material circulation and can damage the development of sustainable society. In
this study, we analyze the conditions of nitrogen material circulation, simulate theinterrelation between the excessive emission of nitrogen and socio-economic structureby the mathematical model in the study area, and observe if the nitrogen utilization
can satisfy the requirements of environment and economy, in order to reach a decision
regarding the optimal solution to the comprehensive problem.
We formulate the comprehensive system as a linear optimization model. It is built
based on the principle of nitrogen material balance, Input and Output table and othermacroeconomic indicators to analyze the interrelation between nitrogen material
circulation system and socio-economic system. Use the LINGO software to simulate acomputer modeling of the nitrogen material circulation system and the socioeconomic system. The computer modeling is utilized to give predictions, which canbe employed in the process of decision-making.
Key words:
Nitrogen material balance, Input and Output Simulation, mathematical model
1. Introduction
China is a large agricultural country. With 70% of its 1.5 billion people living in ruralareas, China faces grave challenges from both global economic integration and globalchanges in the natural environment. As a developing country with 9.6 × 106 km2 ofland, China must acquire a good understanding of sustainable development; developscientific methods for evaluating the sustainable capability of its socio-economic
development, and deal with the issues of imbalance between economy andenvironment of socio-economic development in order to devise policies to achieve thegoal of sustainable development across the country.

Fig.1 The material balance model: interdependence of economics and environment
Source: Callen and Thomas “Environmental Economics and Management—Theory, Policy,and Applications”—Irwin, USA, p. 6. A slight change in the Figure is incorporated. [1]The relationship between the economy and the environment is generally explained in
the form of a “Material Balance Models” developed by Alen Kneese and R.V. Ayres.
The material balance models Inputs are bestowed with physical property of energy
which is received from the sun. The resulting output from input carries the same levelof energy. Similar to this, there are wastes resulting from consumption activities.
Materials and energy are drawn from the environment, which are used for production
and consumption activities and returned to environment as wastes. So far as thisbalance is maintained, there are no environmental issues. The material balance modelof the economy is given in the Figure 1.

Fig.2 Source: Pidwirny, M. (2006). "The Nitrogen Cycle". Fundamentals of Physical Geography,
2nd Edition. Date Viewed. [2]The nitrogen cycle represents one of the most important nutrient cycles found in
terrestrial ecosystems (Figure 2). Nitrogen is used by living organisms to produce anumber of complex organic molecules like amino acids, proteins, and nucleic acids. The
store of nitrogen found in the atmosphere, where it exists as a gas (mainly N2), plays
an important role for life. This store is about one million times larger than the total
nitrogen contained in living organisms. Other major stores of nitrogen include organic
matter in soil and the oceans. Despite its abundance in the atmosphere, nitrogen isoften the most limiting nutrient for plant growth. This problem occurs because mostplants can only take up nitrogen in two solid forms: ammonium ion (NH4+) and theion nitrate (NO3-). Most plants obtain the nitrogen they need as inorganic nitrate fromthe soil solution. Ammonium is used less by plants for uptake because in large
concentrations it is extremely toxic. Animals receive the required nitrogen they needfor metabolism, growth, and reproduction by the consumption of living or deadorganic matter containing molecules composed partially of nitrogen.
2. Statement of the problem
The activities of humans have severely altered the nitrogen cycle. Some of themajor processes involved in this alteration include:

The application of nitrogen fertilizers to crops has caused increased rates ofdenitrification and leaching of nitrate into groundwater. The additional nitrogenentering the groundwater system eventually flows into streams, rivers, lakes, andestuaries. In these systems, the added nitrogen can lead to eutrophication.
Increased deposition of nitrogen from atmospheric sources because of fossil fuelcombustion and forest burning. Both of these processes release a variety of solid
forms of nitrogen through combustion.
Livestock ranching. Livestock release a large amount of ammonia into theenvironment from their wastes. This nitrogen enters the soil system and then thehydrologic system through leaching, groundwater flow, and runoff.
Sewage waste and septic tank leaching.
3. Model Structure
Nitrogen load of production in Songyuan city
(1)
: Total nitrogen of production: Nitrogen from farming waste: Nitrogen from industrial waste: Nitrogen from disposal waste into river: Nitrogen from Excretion
Flow balance in commodity market(2): Column vector of the total production of each industry (Figure 3): Input-output coefficient matrix.
: Total non-governmental consumption: Total governmental consumption: Column vector of the total investment of each industry: Export of each industry: Import of each industry

Objective function(3)(4): Total nitrogen of constraint discharge

NOX

Factitious
fixation

fixation

Fertilizer

NH3NOX

Arable land

Farming

Crops

CompostIndustrial

FodderFood

Stockbreeding
Excretion

Composting
ProductIndustry

Excretion

Consume

Disposal
ServiceLeavings

Leavings
NOX

Leavings
NOX

Fig.3 Nitrogen flow and classification of the production in Songyuan city

4. Result
The expectant result will reduce the nitrogen discharge having maintained GDP.
References[1] Callen and Thomas “Environmental Economics and Management—Theory,
Policy, and Applications”—Irwin, USA, p. 6. A slight change in the Figure isincorporated.
[2] Pidwirny, M. (2006). "The Nitrogen Cycle". Fundamentals of Physical Geography,
2nd Edition. Date Viewed.