A new assessment method for urbanization environmental impact: urban environment entropy model and its application.
ABSTRACT The thermodynamic law is one of the most widely used scientific principles. The comparability between the environmental impact of urbanization and the thermodynamic entropy was systematically analyzed. Consequently, the concept "Urban Environment Entropy" was brought forward and the "Urban Environment Entropy" model was established for urbanization environmental impact assessment in this study. The model was then utilized in a case study for the assessment of river water quality in the Pearl River Delta Economic Zone. The results indicated that the assessing results of the model are consistent to that of the equalized synthetic pollution index method. Therefore, it can be concluded that the Urban Environment Entropy model has high reliability and can be applied widely in urbanization environmental assessment research using many different environmental parameters.
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ABSTRACT: For a scientist studying climate change, 'eureka' moments are unusually rare. Instead progress is generally made by a painstaking piecing together of evidence from every new temperature measurement, satellite sounding or climate-model experiment. Data get checked and rechecked, ideas tested over and over again. Do the observations fit the predicted changes? Could there be some alternative explanation? Good climate scientists, like all good scientists, want to ensure that the highest standards of proof apply to everything they discover. And the evidence of change has mounted as climate records have grown longer, as our understanding of the climate system has improved and as climate models have become ever more reliable. Over the past 20 years, evidence that humans are affecting the climate has accumulated inexorably, and with it has come ever greater certainty across the scientific community in the reality of recent climate change and the potential for much greater change in the future. This increased certainty is starkly reflected in the latest report of the Intergovernmental Panel on Climate Change (IPCC), the fourth in a series of assessments of the state of knowledge on the topic, written and reviewed by hundreds of scientists worldwide. The panel released a condensed version of the first part of the report, on the physical science basis of climate change, in February. Called the 'Summary for Policymakers,' it delivered to policymakers and ordinary people alike an unambiguous message: scientists are more confident than ever that humans have interfered with the climate and that further human-induced climate change is on the way. Although the report finds that some of these further changes are now inevitable, its analysis also confirms that the future, particularly in the longer term, remains largely in our hands--the magnitude of expected change depends on what humans choose to do about greenhouse gas emissions. The physical science assessment focuses on four topics: drivers of climate change, changes observed in the climate system, understanding cause-and-effect relationships, and projection of future changes. Important advances in research into all these areas have occurred since the IPCC assessment in 2001. In the pages that follow, we lay out the key findings that document the extent of change and that point to the unavoidable conclusion that human activity is driving it.Scientific American 09/2007; 297(2):64-73. · 1.48 Impact Factor
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ABSTRACT: The Pearl River Delta Economic Zone is one of the most developed regions in China. It has been undergoing a rapid urbanization since the reformation and opening of China in 1978. This process plays a significant impact on the urban environment, particularly river water quality. The main goal of this present study is to assess the impact of urban activities especially urbanization on river water quality for the study area. Some Landsat TM images from 2000 were used to map the areas for different pollution levels of urban river sections for the study area. In addition, an improved equalized synthetic pollution index method was utilized to assess the field analytical results. The results indicate that there is a positive correlation between the rapidity of urbanization and the pollution levels of urban river water. Compared to the rural river water, urban river water was polluted more seriously. During the urban development process, urbanization and urban activities had a significant negative impact on the river water quality.Environmental Monitoring and Assessment 10/2006; 120(1-3):313-25. · 1.59 Impact Factor
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ABSTRACT: Some physicochemical parameters were determined for thirty field water samples collected from different water channels in the Pearl River Delta Economic Zone river system. The analytical results were compared with the environmental quality standards for surface water. Using the SPSS software, statistical analyses were performed to determine the main pollutants of the river water. The main purpose of the present research is to investigate the river water quality and to determine the main pollutants and pollution sources. Furthermore, the research provides some approaches for protecting and improving river water quality. The results indicate that the predominant pollutants are ammonium, phosphorus, and organic compounds. The wastewater discharged from households in urban and rural areas, industrial facilities, and non-point sources from agricultural areas are the main sources of pollution in river water in the Pearl River Delta Economic Zone.Journal of Environmental Monitoring 08/2005; 7(7):664-9. · 2.09 Impact Factor
A new assessment method for urbanization environmental
impact: urban environment entropy model
and its application
Tingping Ouyang & Shuqing Fu & Zhaoyu Zhu &
Yaoqiu Kuang & Ningsheng Huang & Zhifeng Wu
Received: 18 June 2007 /Accepted: 12 November 2007 / Published online: 27 December 2007
# Springer Science + Business Media B.V. 2007
Abstract The thermodynamic law is one of the most
widely used scientific principles. The comparability
between the environmental impact of urbanization and
the thermodynamic entropy was systematically ana-
lyzed. Consequently, the concept “Urban Environment
Entropy” was brought forward and the “Urban Envi-
ronment Entropy” model was established for urbaniza-
tion environmental impact assessment in this study. The
model was then utilized in a case study for the
assessment of river water quality in the Pearl River
Delta Economic Zone. The results indicated that the
assessing results of the model are consistent to that of
the equalized synthetic pollution index method. There-
fore, it can be concluded that the Urban Environment
Entropy model has high reliability and can be applied
widely in urbanization environmental assessment re-
search using many different environmental parameters.
The thermodynamic law, which includes the first law,
second law and third law, is one of the most widely
used scientific principles. The first thermodynamic
law represents the principle of energy conservation.
Entropy is central to the second law of thermody-
namics. Meanwhile, the third thermodynamic law is
about the absolute entropy of substances (Fu et al.
1990). The second law of thermodynamics is the most
meaningful law in physics. It is profound not only
because it is a law that has got the most discussion yet
a law that is most strange to us, but also because it
gives us the clue to the understanding of life, i.e. the
famous arrow of time. The time arrow points to the
direction in which an isolated system gets more and
more chaotic and disordered until its entropy gets to
its maximum (Wang 1996). The second law points out
that an isolated system will evolve in such a direction
in which its entropy never decreases. The entropy is a
variable indicating the disorder of the system. The
bigger the entropy is, the lower the level of order of
the system is. For an isolated system, the natural
course of events takes the system to a more
disordered (higher entropy) state. The entropy law
implies that in the course of all processes in an
isolated system, the quality of energy and matter
deteriorates. It can also be expressed that the quality
Environ Monit Assess (2008) 146:433–439
T. Ouyang (*):S. Fu:Z. Zhu:Y. Kuang:
N. Huang:Z. Wu
Guangzhou Institute of Geochemistry,
Chinese Academy of Sciences,
Guangzhou, Guangdong 510640, China
of a system is lower than it was before after a process
The concept of entropy has been applied to
different research fields. Devins (1982) discussed the
physical impact on the environment of energy. For the
economic development and pollution, Rebane (1995)
pointed out that the more developed the economy, the
more serious the pollution, and the more quickly
entropy increases. Leung and Yan (1997) discussed
the transportation research under the entropy princi-
ple. The entropy principle was also applied to energy
impact on ceramic targets (Smalley and Woosley
1999). Ren (2000) brought forward the conception of
disaster entropy and applied it at a case study. Allan
(2002) used the entropy principle to discuss the cost
of complexity in industrial production. Jonathan and
Costas (2002) applied the entropy method to dynam-
ical fermions. Brohan et al. (2006) used the entropy
law to estimate the uncertainty of regional and global
observed temperature changes. Within the research
field of climate change, some scientists used thermo-
dynamic law to discuss the remained uncertainties
(Collins et al. 2007). Unfortunately, little research has
been done applying entropy law to the environmental
impact assessment (He and Chen 2001). Though Wu
et al. (2000) calculated the entropy in dissipative
structure to discuss the developing direction of urban
eco-system; almost no researcher used this theory to
assess environmental impact of urbanization.
Urbanization is an adjustive process of the rela-
tionship between the humankind and the land. The
primary purpose of urbanization is to improve the
environment and to use all kinds of limited resources
fully and effectively (Pugh 1995; Ouyang et al. 2005).
Through the population agglomeration effect of urban
development, a large number of rural people immi-
grate into urban areas. As a result, the urban
population expands quickly. This population urbani-
zation affects urban environment inevitably. This
impact acts on every subsystem of the entire urban
system. During the current developing phase in
China, urbanization is mainly driven by industrializa-
tion (Chen and Chen 2002). Compared to industrial-
ization, urbanization in terms of population can be
quantified more easily. Therefore, it is a simple thought
that population urbanization is the direct influencing
factor on the state of an urban system. The function of
population urbanization in urban systems is equivalent
to the temperature in thermodynamic systems.
The impact of urban development on the environ-
ment is non-reversible. In a certain developing period,
with the increase of urbanization levels, the natural
environment becomes less ordered. On the contrary,
the human environment probably becomes more and
more steady and balanced (Bureau of Statistics of
Guangdong Province (1988–2007). From a certain
urban system state to another, the variation process
may be different. However, once the original and final
states are decided, the integrative variation of urban
environment is stable. As a result, the impact of
urbanization on urban environment is extremely
similar to the effect of temperature to systematic
entropy. Therefore, the primary purpose of this study
is to establish a method for the urbanization environ-
mental impact assessment based on the thermody-
namic entropy law. Through a case study, the
reliability and application of the established method
Foundation of Urban Environment Entropy model
In the urbanization environmental impact research, a
city is an open system that has both energy and matter
exchanges with its environment. As discussed before,
the urbanization environmental impact research sys-
tem is similar to an open thermodynamic system. In
an urbanization environmental impact research sys-
tem, the urbanization level in terms of population is
the independent variable for all changes while the
environmental level is a dependent variable changing
with the population urbanization level. In order to
establish the Urban Environment Entropy model
based on the entropy law to measure and assess the
influence of urbanization on the urban environment,
two assumptions should be stated.
Firstly, the relationship between urbanization level
and urban environmental level is regarded as a kind of
causality. It means that the urban environmental
variation is a result of urbanization variations.
Secondly, the change of urbanization level is the
exclusive reason for urban environmental impact. It
means that the other factors are not considered when
calculating Urban Environment Entropy to assess the
impact of urbanization on the urban environment.
434Environ Monit Assess (2008) 146:433–439
Within the thermodynamics, the entropy is defined as
the heat added per unit temperature (Schroeder 2000;
Baierlein 2003). Similarly, Urban Environment En-
tropy (simplified as UEE) can be defined as a function
of the environmental effect of urbanization on an
urban system in urbanization environmental impact
research. It indicates the degree of influence of
urbanization on the urban environment during the
process of urbanization. Simply, UEE is the quotient
of the changes of environmental level and urbaniza-
tion level. It can be simply represented as the
UEE ¼ ? ð Þd E
where, E stands for the environmental level and can
be represented by several groups of environmental
indicators, and U stands for the urbanization level
which is the urban population percent to total
population of a certain study area. For the negative
urban environmental indicators, the positive sign is
chosen for calculation. On the contrary, the minus is
used for positive urban environmental indicators.
The positive value of UEE means urbanization has
negative impact on urban environment. The urbani-
zation leads to a decreasing quality in urban environ-
ment. The negative value of UEE indicates some
positive effect of urbanization to urban environment.
Urbanization can improve urban environmental qual-
ity to some extent. If the value of UEE is exactly
equal to zero, it can be regarded that urban environ-
ment remains in a balanced state during this certain
process of urbanization. The value of UEE indicates
the degree of the influence of urbanization on urban
environment. The larger the absolute value of UEE,
the higher the impact of urbanization does on urban
Calculation of Urban Environment Entropy
The calculation of the entropy change in thermody-
namics considered several different changing processes
(Fu et al. 1990). During the process of urbanization,
the environmental impact included the assessment for
the history and actuality. Along with the urban
development, the environmental scientists would want
to predict the environmental impact of urbanization.
Therefore, the calculation of the UEE should include
the following different practical conditions.
(1) Environmental indices are monitored at a certain
time. That means the urbanization level is
relatively steady. This situation is similar to the
equal temperature change in the thermodynam-
ics. The entropy change of a thermodynamic
system is equivalent to the quotient between heat
and temperature (Fu et al. 1990). Correspond-
ingly, the UEE can be calculated by the quotient
between the environmental change and the
urbanization level. It can be represented by the
UEE ¼ ?ð ÞDE
If the concentration of a certain pollutant and its
standard or background value can be determined,
the UEE of this pollutant during the process of
urbanization can be calculated using the follow-
UEEi¼ ?ð ÞDEi
Where, ΔEi stands for the percentage of the
difference between the measuring value of the
ith pollutant and its standard or background
value; U is the temporal urbanization level of the
(2) During a certain developing period, the original
and final values of the urbanization level and the
urban environmental indices are known or can
be acquired. According to the definition and the
formula for the UEE, it can be calculated by the
ratio between the variations of the urban envi-
ronmental values and urbanization level. The
formula can be written as following.
UEEi¼ ?ð ÞDEi
Where, ΔEistands for the variation of the urban
environmental index and ΔU is the variation of
the urbanization level during this period.
(3) Based on the known urbanization level and
urban environmental situation, the environmen-
Environ Monit Assess (2008) 146:433–439435
tal impact can be predicted when the urbaniza-
tion level reaches to a certain degree. In general,
a series of values for environmental parameters
appeared along with the change of urbanization
level. Therefore, a function between the envi-
ronmental parameter and urbanization level can
be found using statistic analysis. Then the UEE
of the predicted environmental impact from a
basic stage (urbanization level is U1) to another
(urbanization level is U2) can be calculated
through the integral method using the following
UEE ¼ ?ð Þ
Where, E stands for the urban environmental
level; U is the urbanization level; moreover, the
urban environmental level is a function of the
urbanization level as E=f(U).
Application of the model – a case study
In the practical application, all different kinds of
indicators of urban environment can be used to calcu-
late the UEE for a certain period. In the present case
study, a series of indices for river water quality were
used to assess the practicability and dependability
of the new established Urban Environment Entropy
Thirty river water samples were collected from the
Pearl River Delta Economic Zone during the middle
water level period of the hydrological year 2002.
Several physicochemical parameters were determined
for all the samples. The study area, the distribution of
urbanization level and the sampling sites are illus-
trated in Fig. 1. The monitoring results were published
in the Journal of Environmental Monitoring (Ouyang
et al. 2005).
In the present study, the Urban Environment
Entropy model was applied to assess the analytical
Fig. 1 The study area and the distribution of urbanization and sampling sites
436 Environ Monit Assess (2008) 146:433–439
results. Subsequently, the assessing results were
compared with the results of integrative pollution
index method published at Environmental Monitoring
and Assessment (Ouyang et al. 2006) to certify the
practicability and dependability of the Urban Envi-
ronment Entropy model. The calculation of the UEE
in this case study belongs to the first condition,
mentioned before. The specific characteristic of
urbanization must be considered during the course
of calculation. Generally, the higher the urbanization
level, the larger the impact does on urban environ-
ment. On the other hand, for the convenience of
comparing the results from different assessing meth-
ods, the formula is slightly changed. In the present
study, the percentage of difference between the
analytical result and its standard is used to represent
the environmental variation. Therefore, the calculat-
ing formula is changed to the following form:
tween the analytical result and the standard value for
the ith parameter and U stands for the temporal
urbanization level of a sampling site.
Considering the condition of river water pollution
in the study area, the parameters, NHþ
and TOC were chosen to calculate their UEE.
According to the standards of surface water, the water
quality reaches class II can be used for the source of
drinking water (Bureau of National Environmental
Protection 1989). Therefore, the water quality stan-
dards of class II were used for the UEE calculation.
The population data of late 2001 were used to
calculate the urbanization level. The results of Urban
Environment Entropy for the above parameters are
listed in Table 1.
At the sampling sites 17, 18, 20, and 28, the Urban
Environment Entropy of all parameters appeared to be
positive values. In addition, the UEE values of
ammonia were extremely large, more than 5.0
(Table 1). According to the definition and physical
meaning of the UEE, the river water bodies at these
locations can be regarded as seriously polluted.
Urbanization had an extremely serious negative
impact on the river water quality of these sampling
sites. Positive UEE values appeared at sampling sites
6, 11, and 14 for all or some calculated parameters
and their absolute values ranged from 1.0 to 5.0. It
1 ? U
iis the percentage of difference be-
4, DO, CODMn
can be concluded that river water at these sampling
sites was heavily polluted. During urban develop-
ment, urbanization did a serious negative impact on
these river water bodies. At sampling sites 1, 2, 12,
19, 21, 24, and 27, only a small part of the UEE
values were positive. Moreover, their absolute values
were relatively low. The river water quality was
slightly affected by urbanization at these sites. As for
the samples that were located far away from urban or
industrial areas, the UEE values of all parameters
were negative. Basically, urbanization did not disturb
the river water quality of these locations. On the
contrary, river water quality was improved to a certain
extent due to the population emigration to urban areas
and the increasing investment in environmental
protection related to the economic development
Table 1 The Urban Environment Entropy of main parameters
for every sampling site
Environ Monit Assess (2008) 146:433–439437
(Bureau of environmental protection, Guangdong
The application of the integrative pollution index
method and its assessing results were published in the
Environmental Monitoring and Assessment (Ouyang
et al. 2006). As discussed, the equalized synthetic
pollution index was more than 3.0 at sampling sites
17, 18, and 20. The water bodies at these locations
were seriously contaminated. For the reason these
sites are located within urban zones, it can be inferred
that urban activities extremely deteriorated the river
water quality. Meanwhile, the water bodies located at
the 6, 11, 14, and 28 sampling sites whose pollution
indexes were larger than 1.0 but less than 3.0 had
heavy polluted water. The river water quality was
affected to some serious extent. The waters of
sampling sites 8, 19, 21, 22, 24, and 27 were slightly
polluted. However, equalized synthetic pollution
indices of the other samples were less than 0.2. The
river water remained relatively clean and could match
the requirements of drinking water sources. These
other water bodies were almost not affected by the
human activity because these sampling sites were
located far away from developing urban and industrial
From the discussion mentioned before and the
detailed comparison of the results from the two
methods illustrated in Fig. 2, it can be clearly seen
that the integrative assessing results from the Urban
Environment Entropy model and the equalized syn-
thetic pollution index method are basically consistent.
Only at sampling site 8 and 22, the ESPI indicated
that the river water at these sites was slightly polluted.
However, the results of UEE implied that the river
water quality was not affected negatively by urbani-
zation at these two sites because the UEE values of all
the parameters were negative. Therefore, the relative
error of the assessment was 6.67% for 30 samples.
This kind of error may be caused by systematic error
or accidental error of the experiment. Moreover, the
error of assessing method is small enough to be
ignored. Consequently, it can be concluded that it is
feasible to apply the Urban Environment Entropy
model in the assessment of urbanization environ-
mental impact. The assessing results can be directly
used to discuss the urban environmental problems.
Based on the simple introduction of thermodynamic
theory and systematic analyses of the urbanization
environmental impact, the authors think that the
thermodynamic entropy law can be used as a
reference for the assessment of urbanization environ-
mental impact. The concept of Urban Environment
Entropy was brought forward, and its physical
meaning was defined in the present study. Before
the establishment of Urban Environment Entropy
model, two assumptions were stated. The calculation
of the Urban Environment Entropy was discussed
through three different circumstances, which included
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Fig. 2 Comparison of
ESPI and UEE for every
438 Environ Monit Assess (2008) 146:433–439
historical and current condition assessments and the
prediction of the future.
As a case study, the assessment of urbanization
impact on river water quality in the Pearl River Delta
Economic Zone was simply introduced to show the
application of the new method. Comparison was
performed between the results from the equalized
synthetic pollution index method and the urban
environment entropy model. The results indicated that
low relative error exists between the two assessing
results. This comparison proves the practicability and
reliability of the urban environment entropy model.
As well known, the state of the urban system can
be represented by many natural environmental factors
such as urban water, urban land use, air and soil
quality, and a series of socioeconomic indicators such
as economic situation, quantity and quality of popu-
Environment Entropy model, almost all the mentioned
series of environmental indicators can be used to
calculate their UEE to assess the urban environmental
impact during urbanization process. Furthermore, the
required database used for the Urban Environment
Entropy model is relatively simple and easy to collect.
model can be widely used in the urbanization environ-
mental impact assessment research.
Group Project of NSF of Guangdong Province (Grant No.
04201163) and the Key Project of NSF of Guangdong Province
(Grant No. 021446). Professor Guangping He gave many help on
the introduction of thermodynamic theory. Mr. John Rollins helped
us with the English writing during the preparation of this
manuscript. We express sincere appreciation to them for their help.
This work was partially supported by the
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