Assessment of light pollution risk level

. Artificial light has both positive and negative effects, affecting different sites in different ways. The level of light pollution is influenced by the level of local development, population, biodiversity, geography and climate. Therefore, it is important to assess the risk level of light pollution and to study the impact of different interventions to reduce light pollution in different locations. In this paper, four different types of representative locations in China were selected for calculation using the LPRL assessment model. Protected land locations have the lowest L1 values. Urban communities have the highest LPRL of L7. Rural and urban communities have LPRLs of L2 and L5, respectively. the results show that for rural communities, SI works best. It increased LPRL from L2 to L1. however, SII and SIII had no effect on LPRL. For urban communities, SIII had a significant effect in that it increased LPRL from L7 to L5. Therefore, it was necessary to focus on this aspect to develop the most effective intervention strategy for an urban community in Hangzhou, and a 1-page flyer was created to promote the strategy at this site.


Introduction
Light pollution is used to describe the excessive or bad use of artificial light. Some phenomena we call light pollution include light intrusion, over-illumination and light clutter. Light pollution will change our view of the night sky, affect the environment, and affect our health and safety. [1] Plant maturity may be delayed or accelerated, and the migration model wildlife may be affected. Too much artificial light will disturb our circadian rhythm, lead to poor sleep quality, and may also have physical and mental health problems. [2][3] Artificial glare lamps may cause some motor vehicle accidents. Human intervention strategies can reduce the negative impact of light pollution. However, artificial light has positive and negative effects, affecting different locations in different ways. The impact of light pollution may depend on the local development level, population, biodiversity, geography and climate. Therefore, the assessment of the impact degree and potential impact of any intervention strategy must be targeted at a specific location. (ICM) is working to raise public awareness of the impact of light pollution and develop intervention strategies to mitigate these impacts. [4][5] In order to support this work of ICM, we need to solve the problem of measuring and mitigating the impact of light pollution in different places, taking into account human and non-human issues. [6] There are two problems we need to solve: a) Select appropriate indicators and establish a calculation model of light pollution level to evaluate the light pollution of different types of sites (protected land, rural communities, suburban communities, urban communities). Try to explain the model value.
b) Put forward the intervention strategy to solve light pollution, and apply the intervention strategy to two places. Use the model to calculate the impact of intervention strategy on light pollution, get the optimal intervention strategy, and discuss the impact mechanism of the selected intervention strategy.

Model analysis
The degree of glare, light overflow and light invasion can be evaluated by three indicators: glare, light invasion degree and light invasion degree. The value of light pollution degree in the area should be equal to the sum of the three types of internal pollution degree, which is the accumulation of three indicators: glare, light invasion degree and light invasion degree in the area [7]. Like air pollution, water pollution and even nuclear pollution, although the specific pollution index value, the pollution index value can not clearly indicate the degree of pollution. Therefore, the classification criteria of various pollution indicators are proposed. The same is true for glare, light overflow and light pollution in the area. Although the specific value of glare pollution can be calculated by formula, only knowing this value can not clearly reflect the degree of glare. Therefore, the regional glare, light overflow and light invasion are graded [8]. Try to find out the grade of glare and its indicators to clearly understand the grade of glare pollution represented by different glare indicators. In order to further combine with light overflow and light invasion, the calculation method and grade division of regional light pollution degree are formed. Based on the principle of hierarchical cluster analysis in statistics, the glare calculation results in the glare model are analyzed. In order to evaluate glare more accurately, the glare calculation results in the glare model are divided into 7 grades. The glare calculation based on the principle of hierarchical cluster analysis is based on the measurement method of the case's dissimilarity measure, and the square Euclidean distance is selected. The calculation equation is Eq. (1).
According to this distance, the glare distance in the model, that is, the similarity between the two cases, is evaluated. Then, according to the average distance between groups (the average value of the distance between the case and each case in this category), the glare, light overflow and light invasion are graded.
According to the definition of the regional light pollution degree, the regional light pollution degree is equal to the result of the sum of the three values of the internal light pollution degree, glare degree and light overflow degree. The levels of three types of light pollution degree are divided, and the threshold of each level is the basis and premise for determining the level of light pollution degree. According to the threshold value of the three types of light pollution, the light pollution degree can also be divided into seven levels(L1-L7). The threshold value is the sum of three light pollution threshold values. The light pollution level classification table and threshold of each level are shown in Table 1 below. According to the classification level of light pollution degree in the table, it can be seen that when the light pollution degree value is less than -3.36, it is Class I pollution, and the pollution degree level is the lowest. When the light pollution value is greater than 3.81, the light pollution level is the highest L7.

LPRL model application
Four different types of representative sites are selected in China and calculated using the light pollution risk assessment model established in Section 2. The location of protected land refers to national parks or wildlife reserves, etc [9]. We choose Qiandao Lake in Hangzhou as the representative site, while the corresponding locations of rural communities, suburban communities and urban communities are also selected in Hangzhou, making the data more comparable. The selection results are shown in Table 2. Find the relevant key test data on the Internet, and calculate the values of encroachment light, glare and overflow light in various types of areas using the model, so as to calculate the LPRL. The results are shown in Table 3. Note: TM is the model value of T. TN is the normalized value of T. LPD is the light pollution degree. Analyzing the above results, we can find that the protected land is located in a national park or wildlife reserve, they have a low light pollution risk level. This means that there is little sky light and no light intrusion. Glare is also rare, and the illumination level is kept at the lowest level to avoid damaging the natural habitat and ecosystem. Rural communities also have a low risk of light pollution, but their illumination level is slightly higher than the location of the reserve. It is mainly due to the intrusion of skylight and light, and more glare. Traffic and public safety are noteworthy risks. Due to the combination of street lamps, commercial real estate and residential lighting, suburban communities have a moderate level of light pollution risk. Due to the high density of lighting equipment and street lamps in urban communities, urban communities have a high level of light pollution risk.

Intervention strategy and potential impact
Based on the results of the above model analysis, we formulated several intervention strategies and detailed action plans. The plan focuses on reducing skylight and light intrusion, while managing the illumination level to balance the security issues and the demand for a certain level of light.

Strategy Ⅰ: Improve the light source
Because people always want to illuminate the city, the light source used at night is extremely bright, and the light pollution caused by it is also very serious. Therefore, we can start from the perspective of light source improvement. For those unnecessarily strong light sources indoor and outdoor, we can replace them with softer light sources. And for manufacturers of lamps and lanterns, they can speed up the improvement of lamps and lanterns, produce products that meet the requirements of brightness and softness, reduce light pollution, and thus reduce the irritation of light sources on the eyes.

Strategy Ⅱ: Improve the glass curtain wall
The glass facades in urban buildings cause specular reflection or aggregation of light, which is part of the reason for light pollution. The renovation of the glass facade can improve the light pollution problem to a certain extent. First, we can transform the shape of the glass facade. Because the concave surface of the arc can gather light, thus producing light pollution, we can reduce the use of the arc in the glass facade. Second, the glass curtain wall at this stage is mainly made of glass. We can use other materials, such as aluminum plate or steel plate instead of glass or mixed with glass, which can not only increase the design sense of the building, but also reduce the specular reflection and concentration of light.

Strategy Ⅲ: Reasonable planning and strengthening greening
In terms of urban planning and design, the government can incorporate the urban light environment elements into the spatial planning and layout of urban buildings [6], and through the management and regulation of urban planning and management departments, reduce the occurrence of specific light pollution problems in a predictable and targeted manner, so as to institutionalize and standardize the urban light pollution management. Measures such as greening the exterior walls of buildings can be taken to strengthen greening, which can not only improve and beautify the environment, but also reduce the harm of light pollution.

Conclusion
Using the formulas for regional glare, light infringement and light spillover, a comprehensive integration and localization of the light pollution environment can be performed. The division of glare, light infringement, light spillage and overall light pollution is given by this paper. Through detailed knowledge of the regional light environment parameters, not only the values of various types of light pollution in the region can be accurately calculated, but also the overall level of light pollution in the region can be classified. According to different strategies, the risk levels of light pollution rings in different regions can be evaluated and compared. There are more and broader elements in the study of regional light pollution risk levels that need to be discussed and further studied.