https://orcid.org/0000-0002-9820-0400
Abstract
Economic and social development have worsened the situation of water pollution and even the ecological environment. It is helpful to quantify the water pollution ecological environment losses for decision-makers to formulate reasonable pollution control plans. However, the current quantitative analyses led by economic methods are not comprehensive and systematic. Therefore, based on the emergy theory and method system of eco-economics, this study analyzed the internal energy flow process of the water-polluted ecosystem, discussed the composition of water-polluted ecological environment loss, and proposed a quantitative model of water-polluted ecological environment loss based on the emergy analysis method. It can reasonably quantify the ecological environment loss caused by water pollution and provide a reference for optimizing regional industrial layout, scientifically formulating pollution control planning, and promoting the sustainable development of the ecosystem. Taking Kaifeng City in Henan Province as an example, the rationality of the model is verified. The results show that the annual average total energy value of water pollution ecological environment loss in Kaifeng City is 3.83 × 1020sej, equivalent to 145 million yuan (0.76) of Kaifeng's gross domestic product (GDP) in 2018.
HIGHLIGHTS
This study analyzed the internal energy flow process of the water-polluted ecosystem.
This study discussed the composition of water-polluted ecological environment loss.
This paper is based on the emergy theory and method system of eco-economics and proposed a quantitative model of water-polluted ecological environment loss based on the emergy analysis method.
INTRODUCTION
Water is a fundamentally natural and strategic economic resource that plays a vital role in promoting economic and social development (Wu et al. 2021). But the rapid development of the global economy has aggravated the interference of human activities on natural rivers, which leads to the frequent occurrence of water pollution and the degradation of river ecological functions. As a result, economic, industrial, and social development in most countries have led to an increase in water pollution and to varying degrees of damage to regional ecological systems (Xu 2020). For a long time, River water resources provide a wide range of necessary ecosystem services (Ćosić-Flajsig et al. 2020). The role of the ecological environment system in supporting economic and social development is rarely measured by price, so its ecological functions are always regarded as ‘free’ services for humans (David 1997; Niu 1997). This is not conducive to the benign development of the ecological environment system. Quantitative research on water pollution ecological environment losses is conducive to understanding the threat in front of the ecological environment intuitively, which is of strategic significance for the sustainable regional development.
Several quantitative research on ecological environmental loss focuses on the quantitative assessment of ecological environmental cost and gradually formed the environmental economic loss assessment method system represented by the willingness assessment method, benefit-cost method, and market value method (Jatropha 2007; Yang et al. 2015; He & Wu 2017). Kopsidas (2017) used the willingness assessment method to calculate how much they might be WTP (Willing to Pay) for supporting activities concerning the preservation/restoration of the Lake Kastoria and Akhtar et al. (2017) used willingness assessment to quantify the willingness of individuals to pay for improved air quality in Lahore, Pakistan. Results revealed that 92.5% of respondents showed a positive willingness to pay and the average predicted willingness to pay by each person was $9.86 per month.
Sun et al. (2020) calculated the economic and environmental benefits of rainwater utilization measures in urban sponge community by using the benefit-cost method and made a comparative analysis with its cost, which proved that rainwater utilization in sponge community has better investment benefits. Jia et al. (2022) used the VEST model and machine learning method to effectively evaluate the impact of the ecological retreat (ER) project on water conservation in the Yellow River Basin and the specific value of comprehensive water production benefits. In addition, Joseph et al. (2021) used the cost-benefit method to analyze the ecological service value of multi-function small reservoirs in northern Ghana and optimize the ecosystem service flow from small reservoirs to wider communities. Cai et al. (2020) used the market value method and other methods to evaluate the farmland ecosystem service value of Qingdao in 1997, 2002, 2007, 2012, and 2017, and established the index system of farmland ecosystem service value. The results showed that the total value of farmland ecosystem services increased year by year. Wang et al. (2013) evaluated the ecological environment loss caused by lead pollution of typical lead-acid battery enterprises in Taizhou with the market value method, and the results showed that the total loss of lead pollution was 1.2183 million yuan, of which the cost of soil remediation and monitoring accounted for 77.1%. Gastineau et al. (2021) proposed a spatial theoretical framework to calculate some values of ecological compensation.
To sum up, most of the current quantification of ecological environment losses is based on the monetary theory of traditional economics, starting from the externality of the system without analyzing the changes within the system. However, money, essentially the equivalent of human labor, can only reflect the value of human labor. Besides, its circulation is independent of nature, so the environmental losses cannot be measured comprehensively only by the monetary theory. In 1987, Odum proposed the emergy analysis method from the perspective of ecological economics. This method is used in the continuous evaluation research on natural ecosystems, agricultural ecosystems (An et al. 1998; Lefroy & Rydberg 2003), urban ecosystems (Huang & Hua 2003), and regional ecosystems (Higgins 2003) widely, and it evaluates the possible impact of human production activities on the ecosystem through the emergy analysis, providing decision-making guidance for ecological management and ecological design (Prado & Brown 1997).
Based on the emergy theory, this paper has discussed the quantification method of water pollution ecological environment losses. According to the flow characteristics of pollutants in water and energy flow in the ecological environment system, the composition of water pollution ecological environment losses has been analyzed for a quantitative method system of water pollution ecological environment losses to be proposed. Kaifeng City, a key promotion city for water ecological civilization construction in Henan Province, should undertake arduous tasks in the prevention and control of water pollution and water ecology. Quantification could intuitively show the amount of water pollution ecological environment losses, supporting decision-making for the protection and governance of the water ecological environment in Kaifeng City in the new era, providing theoretical and methodological references for the quantification of water pollution environmental losses in other areas, and effectively promoting the process of regional ecological protection and high-quality development.
Overview of study area
Kaifeng City, located at 113°–115 °E longitude, 34.5°–35.5 °N latitude, is about 125 km from east to west and 87.5 km from north to south, with land area of 5,077 km2 (Feng 2008). The geographical location is shown in Figure 1. There are many rivers in Kaifeng, belonging to the Yellow River and Huaihe River basins, and two Level 1 water functional areas and five Level 2 water functional areas in downtown. According to Kaifeng Municipal Water Resources Bulletin (2018), the discharge of waste water and sewage in Kaifeng City in 2018 was 145.1133 million tons, most of the water function areas were seriously polluted, and only a few months of the year met the standard. Water quality monitoring at five sections of five major rivers, including Kaifeng section of the Yellow River, Guohe River, Jialu River, Huangbian River, and Huiji River, showed that the current water environment in Kaifeng City was worrisome (the water quality of the Yellow River section was Class III, the Guohe River and the Huiji River were in Class IV, and the other rivers were Class V). See Figure 2 for some on-site investigations.
The geographical location and administrative divisions overview of Kaifeng City.
The geographical location and administrative divisions overview of Kaifeng City.
Current status of water pollution of Kaifeng City.
RESEARCH METHODS
Analysis of the composition of water pollution ecological environment losses
Clean water is an indispensable essential resource on which humans and other living beings depend (Wu & Wang 2022). Therefore, it is of great significance to analyze the composition of ecological environment loss caused by water pollution and understand the value of loss for water pollution control. The composition of water pollution ecological environment losses should be analyzed according to the flow characteristics of pollutants in water body and the circulation process of energy in ecological environment system.
After entering the water body, pollutants flow with the material circulation process of the ecosystem and cause the accumulation of water pollutant year by year (Jamwal et al. 2020). Water pollution damages the aquatic ecosystem, which is aquatic organisms' necessary habitat for survival and reproduction. Aquatic flora and fauna and shoreline plants thereupon reduce and biodiversity gradually decreases.
The self-purification ability of natural water to reduce pollutant concentration through dilution and self-purification is limited. If the concentration of pollutants into the water exceeds the limit, the water quality will continue to deteriorate. Water pollution increases the burden of water self-purification. This leads to a decrease of the self-purification capacity of water body and leads to the water body self-purification loss.
As the water cycle processes, pollutants flow along with it, then the pollutants will enter the water body and cause infiltrate. Then, the composition, structure, and function of the soil are changed due to the infiltrated polluted water. Microbial activities in soil are inhibited, so harmful substances and their decomposition products gradually accumulate in soil and cause soil pollution loss.
In addition, the chemical composition, physical properties, and biological characteristics of the groundwater would change if contaminated surface water invaded the groundwater aquifer along with the hydrological cycle. Therefore, the decline of groundwater quality leads to the loss of groundwater pollution.
Based on the above analysis for the characteristics of pollutant flow in different stages of water cycle in the ecosystem, the specific composition of water pollution ecological environment loss was proposed as follows: biodiversity loss, water self-purification loss, groundwater pollution loss, and land pollution loss.
Quantification of ecological environment losses from water pollution
Emergy theory
The emergy theory and analysis method realize the conversion between the solar energy value and traditional currency through the emergy/dollar ratio (EDR), to solve the difficult problem of measuring the values of natural resources and economic and social currency uniformly (Wang & He 2015).
The emergy theory perfects the insufficiency of traditional economic methods. By the emergy theory, this paper has considered the loss in the process of water pollution fully and established the emergy quantification method for water pollution ecological environment losses from the perspective of ecological methodology.
Energy system diagram for water pollution ecological environment losses
According to the energy flow, conversion and storage process, and the flow path of pollutants in ecological environment system, the various energy flows and logistics in ecological environment system are classified and summarized, and the energy system diagram of water pollution ecological environment losses are shown in Figure 3.
Energy system diagram of ecological environment loss from water pollution.
In the energy system diagram, the flow, transformation, storage process of the main energy flow, and the flow path of the pollutants in the system can be seen clearly, and the input–output relationship of energy in different links pollutant flow process is clarified. According to the flow process and manifestation of pollutants of water cycle in Figure 3, a quantitative method for the loss of all stages of the material cycle in eco-environmental system caused by water pollution is proposed based on the emergy analysis method.
Emergy quantification method of water pollution ecological environment losses
- (1)
Biodiversity loss
- (2)
Water body self-purification loss
- (3)
Groundwater pollution loss
- (4)
Soil pollution loss
is area of sewage irrigation area (km2), 
is cultivated land area in groundwater pollution area (km2), 
is total cultivated area (km2), 
is agricultural product yield reduction rate, and 
is quality loss rate of agricultural products. According to the research results of Wei & Su (2004) Ri is 5% and Rq is 10%.RESULTS AND DISCUSSION
In 1980, China was in the early stage of economic development, and the degree of ecological environment damage caused by water pollution was low, which was close to the natural state. Therefore, this paper takes 1980 as the base year and 2012–2018 as the research period to quantitatively analyze the water pollution ecological environment losses in Kaifeng City, Henan Province.
Quantification of water pollution ecological environmental loss in Kaifeng City
Based on the relevant data in the Kaifeng City Water Resources Bulletin and the Kaifeng Statistical Yearbook, water pollution ecological environment losses in Kaifeng were calculated by the quantitative formula proposed above. Due to the lack of data on aquatic species in Kaifeng City in 1980, the biological species data of the Henan section of the Huai River Basin were used because most of the area in Kaifeng City belonged to the Huai River Basin. The conversion rate of solar energy value of water body is calculated according to the method proposed by Lv et al. (2020), and the conversion rate of solar energy value comes from the achievement of Lanshengfang. Other data sources are clearly given below.
Table 1 shows that the values of biodiversity loss, water self-purification loss, groundwater pollution loss, and land pollution loss caused by water pollution in Kaifeng City from 2012 to 2018. And the summary of water pollution ecological environment losses is shown in Table 2. Based on the analysis of the proportion of each water pollution ecological environment losses in Kaifeng City in 2012–2018, the proportion chart (Figure 4), an energy value trend map (Figure 5), and a trend map (Figure 6) were drawn.
Calculation table of water pollution ecological environment losses in Kaifeng City from 2012 to 2018
| Items | Parameter | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 |
|---|---|---|---|---|---|---|---|---|
| Water self-purification lossa | COD emissions (t) | 76,838.42 | 72,875.24 | 72,044.89 | 71,409.43 | 5,659.03 | 14,752.33 | 15,650.46 |
| Ammonia nitrogen emissions (t) | 7,982.00 | 7,277.52 | 6,750.70 | 6,785.17 | 566.38 | 2,774.16 | 2,497.27 | |
| COD water self-purification coefficient (/d) | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 | |
| Ammonia nitrogen water body self-purification coefficient (/d) | 0.18 | 0.18 | 0.18 | 0.18 | 0.18 | 0.18 | 0.18 | |
| COD transformity (104 sej/g) | 3.16 | 3.16 | 3.16 | 3.16 | 3.16 | 3.16 | 3.16 | |
| Ammonia nitrogen transformity (109 sej/g) | 2.80 | 2.80 | 2.80 | 2.80 | 2.80 | 2.80 | 2.80 | |
| COD water self-purification loss (1014 sej) | 3.73 | 3.54 | 3.50 | 3.47 | 0.28 | 0.72 | 0.76 | |
| Self-purification loss of ammonia nitrogen (1018 sej) | 4.02 | 3.67 | 3.40 | 3.42 | 0.29 | 1.40 | 1.26 | |
| Water self-purification loss (1018 sej) | 4.02 | 3.67 | 3.40 | 3.42 | 2.86 | 1.40 | 1.26 | |
| Biodiversity lossb | Species difference between base year and current year (species) | 86 | ||||||
| Species transformity (1025 sej/ species) | 1.26 | 1.26 | 1.26 | 1.26 | 1.26 | 1.26 | 1.26 | |
| The ratio of the area of biological activity to the total area of the world (10−7) | 3.45 | 3.45 | 3.45 | 3.45 | 3.45 | 3.45 | 3.45 | |
| Biodiversity loss (1020 sej) | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | |
| Groundwater pollution lossc | Transformity of water energy value before pollution (105 sej/J) (III) | 3.73 | 3.73 | 3.73 | 3.73 | 3.73 | 3.73 | 3.73 |
| Transformity of water energy value after pollution (105 sej/J) (IV) | 3.83 | 3.83 | 3.83 | 3.83 | 3.83 | 3.83 | 3.83 | |
| Transformity of water energy value after pollution (105 sej/J) (V) | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | |
| Contaminated groundwater (106m3) (IV) | 3.53 | 2.98 | 3.91 | 4.06 | 4.03 | 4.45 | 4.59 | |
| Contaminated groundwater (106m3) (V) | 3.53 | 2.98 | 3.91 | 4.06 | 4.03 | 4.45 | 4.59 | |
| Gibbs free energy of water relative to surrounding environment (J/g) (IV) | 8.11 | 6.86 | 8.99 | 9.34 | 9.27 | 10.23 | 10.56 | |
| Gibbs free energy of water relative to surrounding environment (J/g) (V) | 5.02 | 5.02 | 5.02 | 5.02 | 5.02 | 5.02 | 5.02 | |
| Groundwater pollution loss (1017 sej) | 4.91 | 4.91 | 4.91 | 4.91 | 4.91 | 4.91 | 4.91 | |
| Land pollution lossd | Gross agricultural production (1010¥) | 2.85 | 3.07 | 2.70 | 2.79 | 2.88 | 2.77 | 2.88 |
| Total cultivated area (km2) | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | |
| Area of sewage irrigation area (km2) | 66.70 | 66.70 | 66.70 | 66.70 | 66.70 | 66.70 | 66.70 | |
| Cultivated land area in groundwater pollution area (km2) | 99.00 | 99.00 | 99.00 | 99.00 | 99.00 | 99.00 | 99.00 | |
| Soil energy loss (1018 sej) | 6.09 | 6.39 | 5.45 | 5.14 | 4.94 | 3.56 | 3.32 | |
| Items | Parameter | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 |
|---|---|---|---|---|---|---|---|---|
| Water self-purification lossa | COD emissions (t) | 76,838.42 | 72,875.24 | 72,044.89 | 71,409.43 | 5,659.03 | 14,752.33 | 15,650.46 |
| Ammonia nitrogen emissions (t) | 7,982.00 | 7,277.52 | 6,750.70 | 6,785.17 | 566.38 | 2,774.16 | 2,497.27 | |
| COD water self-purification coefficient (/d) | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 | 0.15 | |
| Ammonia nitrogen water body self-purification coefficient (/d) | 0.18 | 0.18 | 0.18 | 0.18 | 0.18 | 0.18 | 0.18 | |
| COD transformity (104 sej/g) | 3.16 | 3.16 | 3.16 | 3.16 | 3.16 | 3.16 | 3.16 | |
| Ammonia nitrogen transformity (109 sej/g) | 2.80 | 2.80 | 2.80 | 2.80 | 2.80 | 2.80 | 2.80 | |
| COD water self-purification loss (1014 sej) | 3.73 | 3.54 | 3.50 | 3.47 | 0.28 | 0.72 | 0.76 | |
| Self-purification loss of ammonia nitrogen (1018 sej) | 4.02 | 3.67 | 3.40 | 3.42 | 0.29 | 1.40 | 1.26 | |
| Water self-purification loss (1018 sej) | 4.02 | 3.67 | 3.40 | 3.42 | 2.86 | 1.40 | 1.26 | |
| Biodiversity lossb | Species difference between base year and current year (species) | 86 | ||||||
| Species transformity (1025 sej/ species) | 1.26 | 1.26 | 1.26 | 1.26 | 1.26 | 1.26 | 1.26 | |
| The ratio of the area of biological activity to the total area of the world (10−7) | 3.45 | 3.45 | 3.45 | 3.45 | 3.45 | 3.45 | 3.45 | |
| Biodiversity loss (1020 sej) | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | |
| Groundwater pollution lossc | Transformity of water energy value before pollution (105 sej/J) (III) | 3.73 | 3.73 | 3.73 | 3.73 | 3.73 | 3.73 | 3.73 |
| Transformity of water energy value after pollution (105 sej/J) (IV) | 3.83 | 3.83 | 3.83 | 3.83 | 3.83 | 3.83 | 3.83 | |
| Transformity of water energy value after pollution (105 sej/J) (V) | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | 3.91 | |
| Contaminated groundwater (106m3) (IV) | 3.53 | 2.98 | 3.91 | 4.06 | 4.03 | 4.45 | 4.59 | |
| Contaminated groundwater (106m3) (V) | 3.53 | 2.98 | 3.91 | 4.06 | 4.03 | 4.45 | 4.59 | |
| Gibbs free energy of water relative to surrounding environment (J/g) (IV) | 8.11 | 6.86 | 8.99 | 9.34 | 9.27 | 10.23 | 10.56 | |
| Gibbs free energy of water relative to surrounding environment (J/g) (V) | 5.02 | 5.02 | 5.02 | 5.02 | 5.02 | 5.02 | 5.02 | |
| Groundwater pollution loss (1017 sej) | 4.91 | 4.91 | 4.91 | 4.91 | 4.91 | 4.91 | 4.91 | |
| Land pollution lossd | Gross agricultural production (1010¥) | 2.85 | 3.07 | 2.70 | 2.79 | 2.88 | 2.77 | 2.88 |
| Total cultivated area (km2) | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | 3,940.4 | |
| Area of sewage irrigation area (km2) | 66.70 | 66.70 | 66.70 | 66.70 | 66.70 | 66.70 | 66.70 | |
| Cultivated land area in groundwater pollution area (km2) | 99.00 | 99.00 | 99.00 | 99.00 | 99.00 | 99.00 | 99.00 | |
| Soil energy loss (1018 sej) | 6.09 | 6.39 | 5.45 | 5.14 | 4.94 | 3.56 | 3.32 | |
Note: aAccording to the Kaifeng City Water Resources Bulletin, the main pollutants in Kaifeng City's rivers are COD and ammonia nitrogen. The data of pollutant emissions are cited from the Kaifeng City Water Resources Bulletin (2012–2018), and the transformity of each pollutant and self-purification coefficient of polluted water are cited from Research results of Odum (1994) and Zhang et al. (2015).
bThe species data of the base year are cited from the research results of Wei et al. (1991), and the species data of research period are data in 2015 and research results of Min et al. (2016). The number of species in the base year is 86 more than that of species in research period.
cDue to data limitation, the amount of contaminated groundwater is calculated by the area ratio method. The related water transformity refers to the literature, and the data of contaminated groundwater area are cited from the research results of Cui & Xu (2008).
dThe data of land output value and cultivated land area are from the Kaifeng City Statistical Yearbook (2013–2019) and Kaifeng City Water Resources Bulletin (2012–2018).
is the area of cultivated land in the contaminated groundwater area and 
is the total cultivated land. (The data of area are from the Special Research Report on the Coordination of Land Use and Ecological Environment Construction in Kaifeng City).
Summary table of water pollution ecological environmental losses in Kaifeng City from 2012 to 2018
| Years | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | Average |
|---|---|---|---|---|---|---|---|---|
| Biodiversity loss (1020 sej) | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 |
| Water self-purification loss (1018 sej) | 4.02 | 3.67 | 3.40 | 3.42 | 0.29 | 1.40 | 1.26 | 2.49 |
| Groundwater pollution loss (1017 sej) | 8.94 | 7.56 | 9.90 | 10.30 | 10.22 | 11.28 | 11.64 | 9.98 |
| Land pollution loss (1018 sej) | 6.09 | 6.39 | 5.45 | 5.14 | 4.94 | 3.56 | 3.32 | 4.99 |
| Ecological loss from water pollution (1019 sej) | 38.50 | 38.48 | 38.38 | 38.36 | 38.03 | 38.01 | 37.97 | 38.25 |
| EDR (1011 sej/¥) | 3.39 | 3.30 | 3.20 | 2.92 | 2.72 | 2.04 | 1.83 | / |
| Currency representation (109¥) | 1.14 | 1.17 | 1.20 | 1.31 | 1.40 | 1.86 | 2.08 | 1.45 |
| Years | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | Average |
|---|---|---|---|---|---|---|---|---|
| Biodiversity loss (1020 sej) | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 | 3.74 |
| Water self-purification loss (1018 sej) | 4.02 | 3.67 | 3.40 | 3.42 | 0.29 | 1.40 | 1.26 | 2.49 |
| Groundwater pollution loss (1017 sej) | 8.94 | 7.56 | 9.90 | 10.30 | 10.22 | 11.28 | 11.64 | 9.98 |
| Land pollution loss (1018 sej) | 6.09 | 6.39 | 5.45 | 5.14 | 4.94 | 3.56 | 3.32 | 4.99 |
| Ecological loss from water pollution (1019 sej) | 38.50 | 38.48 | 38.38 | 38.36 | 38.03 | 38.01 | 37.97 | 38.25 |
| EDR (1011 sej/¥) | 3.39 | 3.30 | 3.20 | 2.92 | 2.72 | 2.04 | 1.83 | / |
| Currency representation (109¥) | 1.14 | 1.17 | 1.20 | 1.31 | 1.40 | 1.86 | 2.08 | 1.45 |
The percentage of the multi-year average ecological environment losses from water in Kaifeng City.
The percentage of the multi-year average ecological environment losses from water in Kaifeng City.
The emergy expression trend diagram of ecological environment losses from water of Kaifeng City in 2012–2018.
The emergy expression trend diagram of ecological environment losses from water of Kaifeng City in 2012–2018.
Trends of ecological environment losses from water in Kaifeng City. (a) Ecological loss from water pollution is expressed in emergy. (b) Ecological loss from water pollution is expressed in currency.
Trends of ecological environment losses from water in Kaifeng City. (a) Ecological loss from water pollution is expressed in emergy. (b) Ecological loss from water pollution is expressed in currency.
Result analysis of ecological environment losses from water pollution
The analysis of Figure 4 shows that the values of biodiversity loss, water body self-purification loss, groundwater pollution loss, and soil pollution loss in Kaifeng City from 2012 to 2018 are 3.74 × 1020, 2.49 × 1018, 9.98 × 1017, and 4.99 × 1018 sej and accounted for 82.52, 4.86, 0.79, and 10.83%, respectively. The multi-year average total emergy of water pollution ecological environment losses was 3.83 × 1020 sej, equivalent to 145 million yuan in currency and accounting for 0.76‰ of Kaifeng's gross national income (GNI) in 2018. In general, the biodiversity loss accounts for the largest proportion of all losses, followed by land pollution loss and water body self-purification loss. Groundwater pollution loss accounts for a relatively small proportion. It is related to the actual situation of Kaifeng City that the aquatic organisms are harmed firstly when the water body is polluted. In addition, the time span in this paper is long and the species may change greatly. Secondly, there are sewage irrigation area and groundwater pollution area in the Huiji River Region. The large sewage irrigation area results in a higher proportion of soil loss among ecological environment losses from water pollution.
In the research of other scholars, the economic loss of water pollution in each reach of the Xiangjiang River Basin in 2016 was calculated by using the economic loss function of water pollution and one-dimensional water quality model by Liu et al. (2020). Loudi Xiangtan Section lost 670.9 billion yuan, accounting for 0.36% of Xiangtan's GDP in 2016. Zhu & Wu (2020) estimated that the total economic loss caused by water pollution in Xinjiang in 2017 was 2.69 billion yuan, accounting for 0.25% of GDP, by using the decomposition summation method to prove the reasonableness of the calculation results of the model.
With the introduction and implementation of the ‘three red lines (water resources development and utilization control red line, water use efficiency control red line, and water functional area limit pollution red line)’ system and the continuous improvement of the river chief system, the losses of water body self-purification and soil pollution are downward steadily. However, in Figure 5, we can see that the groundwater pollution loss is increasing. Though the quantification value of groundwater pollution loss is small, the increasing trend cannot be ignored.
The water pollution ecological environment losses in Kaifeng City from 2012 to 2018 have shown different trends in emergy and currency. Referring to Figure 6(b), we find that it is mainly due to the difference in the EDR. It can also reflect the lack of imbalance between economic development and water environment governance in Kaifeng, namely the economic growth rate is greater than the rate of environmental governance. So, it is necessary to persist in overall planning and coordinate the two aspects.
CONCLUSION AND OUTLOOK
In this paper, the emergy theory and analysis method was applied to the quantitative study of ecological environment loss caused by water pollution, which enriches the quantitative method of ecological environment value loss caused by water pollution and broadens the thinking of application of the emergy analysis method. Firstly, the energy conversion process in the polluted aquatic ecosystem was analyzed by using the energy value theory. On this basis, the specific components of the water-polluted ecological environment loss were summarized and the calculation system of the ecological environment loss was determined. Finally, the specific quantitative method of water pollution ecological environment loss was given and a quantitative model of water pollution ecological environment loss based on energy value analysis was constructed.
The water pollution ecological environment losses in Kaifeng from 2012 to 2018 were calculated. The conclusions are as follows: the multi-year average total emergy of water pollution ecological environment losses was 3.83 × 1020 sej, equivalent to 145 million yuan in currency and accounting for 0.76‰ of Kaifeng's GDP in 2018. In Kaifeng City, the biodiversity loss accounts the largest in the composition of ecological environment losses from water pollution, followed by soil loss, water body self-purification loss, and groundwater pollution loss. This indicates that the treatment of water pollution ecological environment losses in Kaifeng City should mainly focus on the treatment of water body and soil pollution. From the perspective of energy flow, it can be seen that the preliminary development in water pollution control has been achieved in recent years, but the control strength and efficiency should be improved further. The calculation results are helpful for understanding the value of ecological environment loss caused by water pollution in Kaifeng City, causing the protection of water environment, coordinating the relationship between economic development and water environment management, reducing environmental losses caused by water pollution in Kaifeng City, and promoting social and economic development and sustainable development of water ecological environment in Kaifeng City.
This paper still has shortcomings: In the emergy theory, this paper referred to the existing results of solar transformity and other indexes. Since the solar transformity is related to geographical location and other factors, the calculation based on existing results may affect the accuracy of conclusions here. In addition, due to the lack of a continuous biodiversity data, this paper assumed that the number of aquatic organisms did not change in the short term (2012–2018) and cites the data in 2015 as the aquatic life data from 2012 to 2018 in Kaifeng, so the data are inaccurate to some degree. Since the energy conversion of water pollution ecological environment losses is complicated, this paper analyzed and studied the energy flow changes in the certain years and did not consider the integrity of the energy conversion fully. In the future, the pertinence of energy conversion rate and other indicators should be enhanced in the calculation, the calculation method of biodiversity loss value should be improved, and the energy conversion in the multi-level and multi-angle analysis system should be studied to enrich the energy network of the research system.
CONCEPTUALIZATION
C.L. and Y. J. developed the methodology. X.G. conducted formal analysis and investigation. C.L. and Y.J. prepared and wrote the original draft. C.L., Y.J., M.L., and D.Y. wrote, reviewed, and edited the article. X.G. involved in funding acquisition. D.Y. brought resources. M.L. supervised the article.
FUNDING
This research was funded by the National Natural Science Foundation of China (No. NSCF-51909240 and No. NSCF-52079125).
ACKNOWLEDGEMENTS
The authors would like to express their sincere gratitude to the anonymous reviewers for their constructive comments and the Editor of the journal. Their detailed suggestions have resulted in an improved manuscript.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST STATEMENT
The authors declare there is no conflict.
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