The dynamic evolution of collaborative networks in sustainable development: Untying impact of environmental policy in China using network-based text analysis approach.

As one of the key subjects of multi-center governance of environmental concerns, public perception is crucial in forming and implementing environmental policy. Based on data science research theory and the original theory of public perception, this study proposes a research framework to analyze environmental policy through network text analysis. The primary contents are bidirectional encoder representation from transformers-convolution neural network (BERT-CNN) sentiment tendency analysis, word frequency characteristic analysis, and semantic network analysis. The realism of the suggested framework is demonstrated by using the waste classification policy as an example. The findings indicate a substantial relationship between perceived subject participation and policy pilot areas and that perceived subject participation is repeating. On this premise, specific recommendations are made to encourage policy implementation.

Introduction

The negative implications of global climate change are increasingly being examined in numerous fields, and both natural and human components of climate change are being addressed in the literature (Palm and Thoresson, 2014; Rajapaksa et al., 2018). More precisely, the public’s perception of environmental issues and the degree of public concern are major factors affecting the effectiveness of climate change policies (Cheng and Li, 2020). The government formulates environmental policies in China, which include administrative environmental policies, market-oriented environmental policies, and public engagement in environmental policies (Yang et al., 2019). The key to effective policy implementation to promote resource efficiency is public acceptance, and support demonstrated through actions. However, in most situations, the public’s degree of concern is very low, or the public’s views have not been turned into environmentally friendly actions, reducing the efficacy of environmental policies (Weber, 2016; Foguesatto and Machado, 2021). With the development of China’s economy and the continuous improvement of residents’ consumption levels, the output of domestic waste is increasing year-by-year. In today’s unsustainable waste treatment mode, simply relying on landfills and incineration, waste source treatment is the meaning of solving the dilemma of “waste besieging the city” and improving urban resources and the environment (Kuang and Lin, 2021).

The study of Zhang et al. (2021) used a sample of Twitter data to analyze people’s perception of greenhouse gas emissions and their preference for renewable energy by using semantic text similarity and network analysis. China’s per-capita ecological wealth is relatively low at this stage, and environmental protection has become the bottleneck of development (Zheng et al., 2019). As one of the main bodies of multi-center governance of environmental issues, the public’s perception will directly affect the success of environmental policy implementation (Zhu et al., 2016). To understand the public perception of waste classification policy, it is necessary to analyze the public attention, emotional tendency, and policy evaluation of environmental policy. Exploring the public perception of environmental policy is one of the important links between scientific and democratic decision-making and an important reference basis for the promotion and improvement of environmental policy.

Scholars have successively researched environmental policies, which are mainly divided into three aspects. The first is analyzing the environmental policy system and environmental policy tools (Shen et al., 2020). The second is the analysis of the impact of environmental policies. For example, Shen et al. (2019) analyzed different types of environmental regulations and their heterogeneous effects on environmental total factor productivity. Marti and Puertas (2021) studied the impact of environmental policies on waste disposal. Although scholars have analyzed the public perception of environmental issues, Zhang et al. (2019) studied the public’s perception of haze during haze weather and how public environmental perception promotes the implementation of environmental policies. Mao et al. (2018) studied the difference in risk perception between officials and the public in dealing with environmental conflicts. Although scholars are concerned about the public perception of environmental policies, it is mainly through questionnaire surveys to analyze the understanding and evaluation of specific people on specific policies. Pan et al. (2020) discussed the reasons affecting the ecosystem service value of Taihu Lake through in-depth interviews, increased the sense of public participation, and linked public perception with environmental policies, to form an environmental policy reflecting social values. The public perception of environmental policy is a rare but worthy research direction.

Based on the preceding assessment, present environmental policy research does not address public perceptions of environmental policy characteristics, content, emotional orientation, or policy evaluation. Previous research has largely used empirical data with small sample sizes and no text data from cyberspace. Weibo’s popularity and China’s systematic environmental policy execution make analyzing the public perception of environmental policy implementation more intuitive and complete. This article proposes an analytical framework of public perception of environmental policy based on network text analysis, which systematically and fully grasps popular perception of environmental policy, providing a basis for further enhancing environmental policy. As an example, this study focuses on the specific analysis process and public perception of the framework and proposes applicable countermeasures and solutions.

Bidirectional encoder representation from transformers-convolution neural network model

Bidirectional encoder representation from transformers is a state-of-the-art language model that can be fine-tuned or directly used as a feature extractor for various text tasks (Devlin et al., 2019). The study by Kim (2014) uses a convolutional neural network (CNN) to solve the problem of emotion classification, and the experimental results show that the classification characteristics of the CNN are significantly better than that of a recursive neural network. Bahdanau et al. (2015) proposed that the attentional mechanism model has achieved good results in machine translation. After that, Google expanded the self-attention model into a multi-head structure and proposed Transformer, a model framework based on pre-trained feature extraction technology, for machine translation tasks, updating the best results for multiple NLP tasks (Vaswani et al., 2017). Open AI proposes a class of pre-training model GPT based on Transformer, which combines unsupervised pre-training with supervised fine-tuning and seeks a general model learning method for multi-domain NLP tasks (Radford et al., 2018). Furthermore, Google AI Language adopts the two-stage training idea of GPT and proposes a BERT model for the deep bi-directional Transformer pre-training model. BERT has strong generality and can be fine-tuned to adapt to most tasks of NLP, such as named body recognition, machine translation, and a series of natural language processing tasks such as emotion analysis (Devlin et al., 2019; Zhao and Wu, 2021).

Convolutional neural network is a kind of neural network that originated from the visual receptive field in biology. It is an important part of the field of deep learning (Kim and Jeong, 2019). In natural language processing, CNN can better extract local features based on pre-training word vectors. Due to easy data feature extraction and great experimental findings, deep learning-based sentiment analysis models represented by CNN have been frequently employed in text sentiment classification and sentiment analysis in social media reviews (Dong et al., 2020). However, relying only on the CNN model and ignoring the semantic relations existing in the context of the review text will result in low accuracy. Furthermore, existing text sentiment analysis methods are insufficient in expressing complex semantic and contextual information in sentences (Pota et al., 2021). In addition, the use of sentiment evolution analysis techniques for effective public opinion analysis has not been fully studied in practice. Considering that the BERT model can better model the semantic information of text sentences, the CNN can better extract local features. Therefore, this article proposes a text sentiment analysis model based on bidirectional encoder representation from transformers-convolution neural network (BERT-CNN) fusion. It also explains the semantics of the text to be processed well, verifies the effectiveness of the model, and analyzes actual public opinion cases.

Materials and methods

Research methods

The research method of this article is the public perception analysis method based on network text. The rapid advancement of technology has introduced many new aspects to human society’s communication behavior, making it possible to collect data on people’s activities (Barbosa et al., 2018). With the progress of natural language processing, the research of social media content based on real-life is a current research hotspot. The social platform contains several text data expressing emotions. Full mining and analysis can intuitively and comprehensively reflect the public’s thoughts, attitudes, and emotions (van Atteveldt et al., 2021). As the mainstream social networking platform in China, Weibo has similar functions to Twitter. As of December 2018, according to the 2018 Weibo user development report, the number of monthly active users of Weibo was 462 million. Although the data from social media such as Weibo may not be completely true and objective, the comments do not necessarily reflect people’s actual views (Conversi, 2012). However, these contents can reflect the public’s emotions and values to a certain extent. The new media represented by Weibo has become the main channel for the public to obtain information, and express opinions and feelings because of its strong openness, high concealment, and unique way of information fission and communication (Han et al., 2020). These two characteristics make Weibo a platform that reflects the public perception of history, current situation, and future. Because of its limitations, Weibo may not be the main basis for the government to make decisions on environmental issues (Kay et al., 2015), but it can provide valuable information conducive to decision-making.

The public perception of environmental policy based on network text analysis is mainly divided into two stages: one is to obtain the network text information; the second is to analyze the public perception of environmental policy through network text information mining. The specific process is as follows: firstly, the public perceived microblog text information on environmental policy is obtained through the collection search crawler; secondly, descriptive statistical analysis is used to understand the characteristics of the perceived subject and the topic types of the perceived object; then, an emotion analysis model based on deep learning is constructed. There are three main types of sentiment analysis methods: dictionary (Whissell, 2009), machine learning (Severyn et al., 2016), and deep learning (Hinton et al., 2006). The deep learning method performs well in expressing complex semantic and contextual information in sentences. Therefore, this article constructs an emotional tendency analysis model based on BERT-CNN to analyze the public’s emotional tendency on important topics of environmental policy (Pota et al., 2021). Finally, the word frequency characteristics and semantic network analysis of classified texts are carried out to mine the focus of different public emotion types, and to analyze the public perception of environmental policy comprehensively and systematically.

Research framework

Big data is changing people’s work, life, and thinking mode (Armstrong, 2011), which has a far-reaching impact on culture, technology, and academic research (Boyd and Crawford, 2012). After Peter Naur put forward the concept of data science for the first time, with the advent of the era of big data, the fourth paradigm – “data paradigm,” which is different from the computing paradigm, has been promoted, and a new discipline – “data science” (Provost and Fawcett, 2013) has emerged. The emergence of data science makes scientific research data-oriented and explains the essence and law of scientific research problems through data collection and mining. Policy researchers have also begun to combine policy research with data science. Big data analysis can create a new era of policymaking and decision-making (Bertot et al., 2014). Applying data science research to policy research will help formulate more accurate and effective policies (Ruggeri et al., 2017). At the same time, data science theory can also be widely applied to social issues such as social media analysis (Toivonen et al., 2019) and hot spot discovery (Bello-Orgaz et al., 2016). In recent years, more and more policy researchers have realized the importance of data and used content analysis to analyze the policy text (Du et al., 2021) and policy communication process (Wu et al., 2021). However, there is a lack of research on public policy perception. Therefore, based on the theory of data science, this article discusses how to analyze the public perception of environmental policies through text information in cyberspace to provide decision support for the formulation and improvement of relevant policies.

The second theoretical support of the research framework is the original theory of public opinion (Noelle-Neumann, 1991). The origin of public perception is composed of three elements: cognition, emotion, and behavior. Cognition, emotion, and behavior are the process of shaping public perception. Public perception refers to the process in which the public’s cognitive information, such as policies and public affairs, is transformed into subsequent behavioral intentions after emotional processing (Morgan, 1997). Specifically, as users participating in public affairs, the public can be regarded as “consumers” interacting with public management departments. In the process of behavior selection of public participation in public policy, the public forms cognition based on existing knowledge or evaluation information for the first time; secondly, combined with personal values, it forms the emotion with obvious tendency to public affairs; finally, affect the final behavior choice of the public based on emotion. The public’s cognition, emotion and behavior response to the policy can reflect the public’s satisfaction with the policy itself and the implementation effect of the policy, and the key to the smooth promotion of the policy lies in whether the public has made a positive response and support to the government’s measures. Therefore, whether the environmental policies formulated by the government can be implemented smoothly and whether the environmental problems can be solved effectively, the key is to grasp the public policy perception. Foreign scholars believe that public perception can be used to study the public’s understanding, attitudes, and views on specific policies, technologies, and events (Panagiotopoulos et al., 2017). The original theory of public perception reveals the specific composition of public perception, which provides a research direction for the public perception of environmental policy in this article. Because this research focuses on analyzing the public perception of environmental policy by mining network text information, combined with the original theory of public perception and the research of scholars at home and abroad, the scope of public perception studied in this article is limited to the public’s cognition and emotion of environmental policy, and the subsequent behavior transformation can be used as the research direction in the future.

The research framework of this article is guided by the research theory of data science and the original theory of public perception. Combined with the process of network text analysis and the characteristics of policy perception research, the construction of the research framework is mainly carried out from three aspects: “network text acquisition” – “network text processing” – “network text analysis.” The research framework of public perception of environmental policy based on network text analysis is shown in Figure 1.

FIGURE 1

Research framework.

Data source

The emergence of the Internet makes human society’s mobility and communication behavior present many unprecedented new characteristics (Yang et al., 2017); in the face of massive network texts, it is necessary to select a suitable network medium for mining. As of December 2018, according to the “2018 Weibo User Development Report,” Weibo has 462 million monthly active users, which is China’s mainstream online social platform. Therefore, the source of the data in this article is the information related to “waste classification” on Weibo, and the data is collected using Jisouke web crawler software. The information obtained includes two parts: user information and post information. Obtained data fields include username, authentication status, location, number of fans, number of posts, authentication status, blog content, comment content, time, and others. The research period is from 26 April 2019, to 22 November 2020. The crawled data was cleaned, deduplicated, and noise reduced, and a total of 1,166 Weibo users and 5,210,000 followers, and 140,000 posts were obtained using “waste classification” as the keyword. Some comments on Weibo topics related to “waste classification” published by People’s Daily and CCTV News were used as sentiment analysis texts, and 9,789 Weibo comments were obtained. The results are shown in Table 1.

TABLE 1

The users’ information.

Username	Authentication status	Location	Number of fans	Number of posts
Friends of nature	Official certification	Eastern China	540,000	10,000
The angry WZY	Personal certification	Eastern China	920,000	3,492
The Guangzhou urban management	Official certification	Eastern China	950,000	10,000
Garbage classification guide	Ordinary users	Western China	280	1,200
Solid waste treatment expert Zhang Xu	Personal certification	Middle China	9,056	2,796
Total: 1,166			5,210,000	140,000

Results and discussion

Demographic characteristics

The general characteristics of public perception of waste classification policy include perceptual subject characteristics and perceptual object characteristics. The general characteristics of perceptual subjects are the diversity of subjects such as gender, age, region, and the tendency of perceiving subjects to participate in topics; the general characteristics of perceptual objects are the types of perceptual topics.

The characteristics of perceptual subjects include the diversity of perceptive subjects and the tendency of perceptive subjects to participate in topics. From the perspective of the diversity of perceptual subjects, as shown in Table 2, through the analysis of the “authentication situation,” the proportion of ordinary user accounts in the waste classification policy is 83.7%, and the proportion of Weibo official authentication accounts is 13.64%, and the proportion of Weibo personal authentication accounts is 2.66%. The proportion of ordinary user accounts is relatively high, which to a certain extent makes the data more comprehensive and covers a wider range. In addition, among the subjects of the waste classification policy perception, the proportion of men is 59.52%, and the proportion of women is 40.48%. The gap between the proportions of people is small, indicating that gender is not an important factor affecting the public perception of waste classification policies. Analyzing the area where the sensing subject is located, the proportion of users in the eastern region is relatively high, at 47.54%, and the proportion of users in the northeast, western and central regions is significantly reduced, being 2.32, 8.49, and 8.67%, respectively. The proportion of users who indicate their region is 33.07%. Further analysis shows that Zhejiang Province, the province where the main body of waste classification policy perception is located, is followed by Beijing, Guangdong, Shanghai, Jiangsu, and other places (Figure 2).

TABLE 2

Perceived subject characteristics of waste classification policy.

Category	Percentage
Gender
Male	59.52
Female	40.48
Region
Eastern China	47.54
Northeast China	2.32
Western China	8.49
Middle China	8.67
Not indicated	33.07
Certification status
Official certification	13.64
Personal certification	2.66
Ordinary users	83.7

FIGURE 2

Statistics on the characteristics of perceived subjects based on provinces.

Important topics of public perception of waste classification policy

There are two reasons for the large geographical gap between the perception subjects—first, is the popularity of Weibo. The Weibo User Development Report shows that Weibo users are showing a downward penetration trend, with Weibo users in second-and third-tier cities accounting for half of the total users. Affected by many factors such as regional economic development, demographic structure, culture and education, and industrial development, Weibo users in eastern regions such as the Pearl River Delta, the Yangtze River Delta, and the Beijing-Tianjin-Hebei region account for a relatively large proportion. In areas with a more developed economy, users have a higher demand for information, and users in this type of area use Weibo more frequently than in other areas. Therefore, the perception of the subject has a higher degree of participation. Second, is the degree of relevance of the area to the waste classification policy. In 2019, Shanghai took the lead in implementing the waste classification policy, and then many places across the country, such as Beijing, Shenzhen, Xiamen, Suzhou, Hangzhou, Ningbo, and others, have gradually begun to carry out and implement waste classification. Therefore, the regional differences in perception subjects are more obvious.

In addition, through time series analysis of the topic search index, we can understand the trend of public participation. As shown in Figure 3, the Baidu Index on topics related to garbage classification policies is on the rise. In 2019, public participation on the topic increased significantly. The Ministry of Housing and Urban-Rural Development said that by the end of 2020, 46 key cities in China would build waste classification and treatment systems. On 28 June 2019, after the “people’s network” published relevant articles, it triggered a heated discussion on the waste classification policy from all walks of life. On July 1, Shanghai officially implemented waste classification, resulting in the peak of public participation on that day, and the search index reached 300,000. After 3 July 2019, public participation dropped significantly. With a series of publicity and implementation on waste classification in Hangzhou, Xi’an, and other cities, waste classification pilot work has been carried out all over the country. The intelligent classified dustbin of the second world artificial intelligence conference has also attracted public attention, and the participation of the subjects of waste classification policy has increased again; the search index reached about 1,750,000. According to the topic trend of perceptual subject participation analysis, the perceptual subject participation in waste classification policy is repetitive. Waste classification policy is an environmental topic of long-term public concern. It has been dormant for a long time because there is no conclusion. Once relevant departments make progress, the participation of perceptual subjects will rise again.

FIGURE 3

“Waste classification” Baidu Index.

The perceptual object is characterized by the perceptual topic type. Weibo launched the “Hot Topic List” in 2013, and the Hot Topic List contains topics that have the most attention now. This article uses “waste classification” as the keyword to retrieve the top 15 hot topics on Weibo, as shown in Table 3. This article divides public perception topics into policy propaganda, policy evaluation, and policy influence based on the content of the topic discussion.

TABLE 3

Waste classification policy hot topic.

Sr. No.	Hot topic	Number of discussion (thousand)	Number of readings (million)
1	#Waste classification challenge#	2,146	2,280
2	#Waste classification together#	724	710
3	#Waste classification#	602	760
4	#Waste classification is a new fashion#	259	680
5	#Why is China in a hurry to classify waste#	175	520
6	#In Shanghai, waste classification individual throwing wrong penalty#	88	550
7	#Waste classification starts with me#	76	49.589
8	#Beijing will promote waste classification legislation#	75	350
9	#In Chengdu, there is no dry and wet classification standard#	47	340
10	#Waste classification guide#	46	29.201
11	#Waste classification makes me quit milk tea#	45	270
12	#In Shanghai, 190 tickets issued for waste classification in 6 days#	36	370
13	#Animals cannot classify waste, but we can#	36	130
14	#Shanghai people after waste classification#	35	320
15	#Waste classification has become a new social network in Shanghai#	19	170

Policy publicity topics are mainly reflected in the publicity and guidance of relevant media on waste classification policies and the guidance in the specific implementation of relevant policies, such as #waste classification challenges#, #waste classification together#, #waste classification is a new fashion#, #waste classification starts from me#, etc. policy publicity topics are the most, which can promote the smooth implementation of waste classification policies.

Policy evaluation topics mainly include the public’s evaluation of the necessity and rationality of policies. #Why China is in a hurry to classify waste#, this topic mainly describes the current environmental problems in China to explain the urgency of the implementation of the waste classification policy. #In Shanghai, 190 tickets issued for waste classification in 6 days# relates to the punishment mechanism in the process of waste classification, which is praised and criticized by the public. Some people think that compulsory waste classification is necessary, which is conducive to cultivating public participation consciousness and improving classification efficiency; the other part believes that the implementation of a punishment mechanism will stimulate social contradictions without considering the actual situation. #In Chengdu, there is no dry and wet classification standard# indicating that the public is more concerned about whether the classification standard is unified nationwide or adapted to local conditions.

Policy impact topics mainly include the impact on the public after the implementation of waste classification policy #Waste classification makes me quit milk tea#, #Shanghai people after waste classification#, #waste classification has become a new social in Shanghai#. All these show that the waste classification policy has been affecting people’s daily lifestyles. To some extent, it shows that the public perception of waste classification will impact the classification behavior.

Through the above analysis, we have a comprehensive understanding of the general characteristics of the perceived subject and perceived object of the waste classification policy. However, due to the great differences in the discussion and reading of topics perceived by the public, the analysis of some important topics in this article will help to understand the focus of public perception of waste classification policy and provide a decision-making basis for the formulation and improvement of policies of relevant departments. This part uses the BERT-CNN model based on deep learning to analyze the emotional tendency of important topic comment texts; then, it analyzes the characteristics of high-frequency words in the texts with different emotional tendencies in the comments; finally, semantic network analysis is carried out based on word frequency analysis. According to the relevance between subject words, we can understand the subject differences under different emotional networks to make the research more accurate.

Emotional tendency of important topics

Emotional tendency analysis is to extract the emotional characteristics of the public on the evaluation object from the text produced by the public and excavate the public’s attitude, view, or emotion (Li et al., 2019), to have a more intuitive understanding of the public perception. This article takes some comments on Weibo topics related to “waste classification” released by the authoritative media people’s daily and CCTV as emotional analysis text and obtains 9,789 Weibo comments. By constructing the emotional tendency analysis model based on the deep learning BERT-CNN model, this article analyzes the emotional tendency of text comments on important topics of waste classification policy.

The pre-training model BERT is a great breakthrough in the field of natural language processing (Pota et al., 2021). The BERT model is based on the encoder of the bidirectional transformer, which makes the BERT model have significant advantages in learning the internal context of sentences and the dependency of words (Vaswani et al., 2017). When carrying out specific tasks, fine-tune, or extract features according to the task requirements, and add corresponding output layers downstream to create the optimal model. Therefore, this article applies the BERT pre-training model to the feature representation of public perception of waste classification policy. The BERT model mainly includes three parts: input layer, coding layer, and output layer. The input of BERT is composed of three vectors, word vector, sentence vector, and position vector. The addition of these three sets of vectors forms the input of the BERT model. When calculating the attention of the BERT coding layer, x is the input, and each input is transformed into a through the matrix operation of embedding, and a is operated respectively with the three matrices W, W, W generated by the transformer. And calculate the attention through the dot product.

Based on attention, the multi-head attention mechanism of BERT expands the original matrix of a single group of Q, W, and E into multiple groups, thereby making the focus more comprehensive. In this article, the BERT model is connected to CNN for further feature extraction, and a sentiment analysis model based on BERT-CNN is constructed.

Convolutional neural network can be used for text classification tasks composed of the input layer, convolution layer, pooling layer, full connection layer, and output layer. The input of CNN is to express sentences or documents in matrix form. Firstly, the data is divided into a training set and verification set, and the training set data is labeled and put into the model for learning. In the specific prediction task, the test set data is used as the input layer data x. the task of the convolution layer is to extract the input information features and splice the input word vectors according to lines to obtain the word vector splicing x of the [i : j] word, and obtain the features of the input information after convolution operation, which is represented by C, where w is the weight matrix of the convolution kernel; b is the offset vector; f is the nonlinear activation function.

Next, multiple sizes of convolution kernels are used to perform convolution operations on the input matrix. Each convolution operation will get a feature map. After performing the convolution operation on each component, C is obtained.

The pooling layer acts on the feature map output by the convolutional layer. The method chosen in this article is maximum pooling, which selects the largest feature from the matrix obtained after convolution to reduce the output dimension while retaining important features. The function of the fully connected layer is mainly to integrate features and connect the feature map to the classification layer in a full connection.

Based on the deep learning BERT-CNN model, this article constructs an emotional tendency analysis model of key topics perceived by the public regarding waste classification policy (shown in Figure 4). In this model, firstly, the crawler tool is used to obtain the waste classification data set based on the Weibo platform and preprocess the text; secondly, the BERT pre-training model is used for word vector training and feature extraction; thirdly, the convolution neural network is used to extract the text features and calculate the text emotion score; finally, the model is trained, the performance indicators are evaluated, and the model is used for emotion classification.

FIGURE 4

Emotional tendency analysis model based on BERT-CNN.

This article adopts sentence-level sentiment classification. Sentence-level sentiment classification is a process of processing and classifying subjective texts with emotional colors, divided into positive emotions and negative emotions (Zhang et al., 2018). This model is a supervised learning model, which requires training data based on a training set data model with known sample labels. Therefore, this article randomly selects 2,289 pieces of data and refers to the manual annotation method of domestic and foreign scholars to mark the text as the model training set (van Atteveldt et al., 2021). Among them, 2002 were used as a training set and 287 were used as a verification set. When the text mainly expresses positive emotions, it is marked as “positive,” such as “support,” “garbage classification, start with me”; when the text mainly expresses negative emotions, it is marked as “negative,” such as “really troublesome,” “Skin-jobs,” etc. Finally, for the model’s accuracy, this article marks the ratio of positive emotions to negative emotions close to 1:1. To prevent over-fitting, a dropout layer with a drop rate of 0.5 is added after the full connection layer. After model training and validation set test, the model’s accuracy reached 88.50%, indicating that its classification effect is good. The experimental results are shown in Table 4.

TABLE 4

Model experiment results.

Corpus	Precision	Recall	F1-score	Support
Positive	0.86	0.92	0.89	144
Negative	0.91	0.85	0.88	143

The accuracy curve and loss curve during model training are shown in Figures 5, 6.

FIGURE 5

Accuracy curve.

FIGURE 6

Loss curve.

Next, the constructed model is used to analyze the emotional tendency. In this article, the collected 7,500 test set data are calculated and presented visually. The score of the public’s emotional tendency towards the waste classification policy is obtained (shown in Figure 7). Based on text classification, this article defines the text with an emotion score between 0.8 and 1 as a positive emotion category, and the number of texts is 3,450 (accounting for 46%); the text with an emotion score between 0 and 0.2 is defined as negative emotion category, and the number of texts is 3,230 (accounting for 43%). The public perception of waste classification policy is polarized.

FIGURE 7

Sentiment score of spam classification topics.

Word frequency characteristics of important topics

To further analyze this event’s residents’ emotional characteristics, this article separately analyzes the weights of positive emotion and negative emotion review texts and extracts keywords through the TF-IDF algorithm. TF-IDF is a calculation method based on statistics, including Term Frequency (TF) and Inverse Document Frequency (IDF). The importance of this word is proportional to the number of times it appears in the text and inversely proportional to the Document Frequency in the total corpus. This algorithm is often used to evaluate the importance of a word in a document to a document, which is obviously in line with the demand for keyword extraction. The more important a word is to a document, the more likely it is to be a keyword of the document. The statistics of the top 20 perceptual words with a weight ratio from high to low are shown in Table 5.

TABLE 5

Perceptual word weight coefficient statistics.

Positive emotion keywords	Weight coefficient	Negative emotion keywords	Weight coefficient
Waste classification	0.771030451	Waste classification	0.358282741
Coming	0.356777804	Trash can	0.227504117
Garbage	0.194963533	Shiver	0.089586032
Protect the environment	0.159501279	Kitchen waste	0.084066341
Support	0.144610607	Plastic bag	0.066147429
Everyone is responsible	0.143690642	Garbage truck	0.064855662
Start with me	0.126995485	Recyclable	0.050947055
Classification	0.126175768	Disposable bag	0.041899371
Hope	0.063272435	Harmful waste	0.034694046
Come on	0.058318732	Packing	0.032665049
Trash Can	0.058285222	Take-out food	0.027707648
Lovely	0.050448476	Handle	0.024762259
Happy to get	0.045546103	Downstairs	0.024670028
Should come	0.045299632	Recyclable waste	0.024018955
Start doing	0.044554029	Standard	0.019634590
A congratulatory message	0.042838154	Implementation	0.019571106
Plastic bag	0.038704886	Notice	0.019548292
Send	0.034949036	Plastic	0.018935138
Earth	0.034804002	Too difficult	0.018515262
Packing	0.032672343	Garbage	0.018014216

Among them: count(t) represents the number of occurrences of the word t in the article; count(d) represents the total number of words in the article; num(corpus) represents the total number of documents in the corpus; num(t) represents the number of documents containing the word.

According to the statistical results, “Waste classification” is the keyword of this article, with the highest weight of 0.78 and 0.36 in positive emotion and negative emotion texts, respectively. Perceptive words such as “Protect the environment” (weight coefficient = 0.16), “Everyone is responsible” (weight coefficient = 0.14), “Start from me” (weight coefficient = 0.13), and “Support”” (weight coefficient = 0.14) and “Come on” (weight coefficient = 0.06) have a high weight in positive emotion, indicating that the public supports the garbage sorting policy. In terms of negative emotion keywords, adjectives such as “Shiver” (weight coefficient = 0.09) and “Too difficult” (weight coefficient = 0.02) have high weights, indicating that part of the public has a negative attitude toward the waste classification policy, has dissatisfaction, and does not actively accept and implement the policy. “Trash” (weight coefficient = 0.23), “Garbage trucks” (weight coefficient = 0.06), “Kitchen waste” (weight coefficient = 0.08), and other nouns with a much higher weight, suggest that the public attention to these aspects are there and opinions and suggestions, public policy at the same time for the garbage classification cities in our country many aspects in the process of waste classification policy implementation met with resistance.

Semantic network analysis of important topics

Based on word frequency analysis, semantic network analysis of waste classification policy comments based on different emotional tendencies can better understand the natural language structure of perceptual subjects when discussing perceptual objects and have certain reasoning and judgment ability. The semantic network analysis of positive and negative emotional texts can reflect the relevance between high-frequency words and tap the focus of perceptual subjects of different emotional types, which is more persuasive and credible. The waste classification policy’s positive and negative emotional text is input into the idiom semantic network diagram in NetDraw, respectively. NetDraw software developed by Steve Borgatti is a very representative semantic network analysis software (Borgatti, 2010). NetDraw has an intuitive graphical display function, simple and easy to learn. The excellent open compatibility injects new vitality into semantic network analysis and has been widely used in semantic network analysis. In this article, positive emotion text and negative emotion text of waste classification policy are saved as notepad files and input into NetDraw respectively for semantic network analysis and semantic network graph generation.

The more edges connected with the node, the stronger the node’s centrality in the whole semantic network. The thicker the edge, the more co-occurrence times between nodes.

As shown in Figure 8, in the positive emotional semantic network of waste classification policy, in order to facilitate the distinction, the first layer is the graph of circular signs, in which the perceived words such as waste classification (degree = 32), garbage (degree = 12), Shanghai (degree = 8), environment (degree = 8), Beijing (degree = 7), and protection (degree = 6) are relatively central. The words with high co-occurrence times include “Support,” and “come on” to express the public’s positive attitude towards the waste classification policy. Words such as “Environmental protection is everyone’s responsibility” and “Suggest promote it nationwide” have a high degree of relevance, indicating that the public’s awareness and enthusiasm for participating in garbage classification have increased, and they can consciously implement the waste classification policy. The second layer is the graph of square signs, indicating that the public supports environmental policies, limited to waste classification policies and simplified packaging, and plastic restriction orders. The third layer is the graph of triangular signs, indicating that the public supports environmental policies. The supporting attitude of waste classification policy is related to the environmental protection concept of “Lucid waters, and lush mountains are invaluable assets” advocated by China for many years. Therefore, in implementing a waste classification policy, the government should strengthen the publicity of ecological, and environmental protection policy, pay attention to the concept guidance of the public, gradually cultivate a green lifestyle, and transform it into self-consciousness and public spirit.

FIGURE 8

Positive affective semantic network diagram.

As shown in Figure 9, there are two levels in the negative emotion semantic network of the garbage classification policy. The first floor is a square sign, “shiver and shaking,” which shows that in the gradual evolution of waste classification policy from voluntary to compulsory, the public expresses their dissatisfaction playfully, not resolutely resisting. The second floor is a circular sign, which shows the main reason the public is dissatisfied with the waste classification policy. Among them, the relative centrality of perception words such as waste classification (degree = 35), trash can (degree = 25), plastic bag (degree = 7), unity (degree = 6), and garbage truck (degree = 5) is relatively high. In-depth exploration found: (1) The words closely connected with the “trash can” are “time-limited” and “delivery.” It shows that there is a big controversy in the implementation of the waste classification policy about the fixed-point release. The time limit for waste classification and disposal conflicts with working hours, which causes inconvenience in life and makes the rules of public action contradict the logic of private life. (2) The high relevance of “uniform standards across the country” indicates that the public is dissatisfied with the current situation of different waste classification standards. (3) The co-occurrence of the word “trouble” and “waste classification” shows that the public is lack waste classification literacy and insufficient understanding of the urgency of waste classification. (4) The frequent references to the words “recyclable” and “harmful” reflect that the public has insufficient knowledge reserves of waste classification, and there is a long way to go in popularizing waste classification knowledge. (5) “Garbage trucks,” “indiscriminate,” and “disposal” co-occur more frequently. The public said that the garbage truck did not achieve classified transportation after classified garbage placement, which dampened the public’s enthusiasm to participate in waste classification. The co-occurrence of “personnel” and “waste classification” indicates a lack of community waste classification staff or dissatisfaction with the work process of relevant personnel.

FIGURE 9

Negative emotion semantic network diagram.

Conclusion and implications

Under the guidance of data science theory and public perception theory, combined with natural language processing, this study puts forward a research framework of public perception of waste classification policy based on network text analysis. It systematically analyzes the public perception of garbage classification policy, the emotional tendency, word frequency characteristics, and the semantic network of important hot topics. The main conclusions are as follows: (1) The public participation in the topic of waste classification policy has been generally improved, the participation of perceptual subjects is repetitive, and the regional differences of perceptual subjects are obvious, indicating that there is a strong correlation between the public participation and the pilot areas of waste classification policy. (2) The types of public perception topics of waste classification policy mainly include policy publicity, policy evaluation, and policy impact. (3) In the emotional tendency analysis of waste classification policy, the public has a mixed attitude. A total of 43% of the public showed negative feelings toward the waste classification policy, and 46% of the public showed positive feelings toward the waste classification policy. (4) Through word frequency analysis of texts with different emotional tendencies, it can be found that the perceived words “protect the environment,” “everyone’s responsibility,” “start from me,” “support,” and “refueling” account for a higher weight in positive emotions. The perceived words “shivering,” “too difficult,” “trash can,” “garbage truck,” and “kitchen waste” account for a higher weight in negative emotions. (5) On the basis of word frequency analysis, the positive and negative emotional texts are analyzed, respectively. In the positive emotional semantic network analysis, the publicity of the environmental protection concept and waste classification policy can effectively promote waste classification. From the negative emotional semantic network, we can see that the reasons for public dissatisfaction mainly include the following aspects: first, the publicity and education efforts and the public’s awareness of environmental protection are insufficient, and the public’s current garbage classification literacy is insufficient, and the relevant knowledge reserve is insufficient. Second, waste classification policies, laws, and regulations are imperfect, which makes the public have great disputes over the specific delivery process, such as regular and fixed-point delivery and different waste classification standards. Third, the infrastructure supporting facilities and collection, transportation, and treatment methods are backward, there are work loopholes in waste classified collection and transportation facilities and terminal treatment facilities, and the staffing of relevant community staff is insufficient.

By analyzing the public perception of waste classification policy, the problems existing in the promotion and implementation of waste classification policy and the areas that need to be improved are found. To effectively deal with the negative public sentiment, promote the supply-demand matching of policies and smoothly promote the waste classification policy, this article puts forward the following policy suggestions. First, improve the effectiveness of waste classification policy promotion. The public’s perception of waste classification policy has different emotional tendencies. Part of the reasons for negative emotions is weak awareness of waste classification and lack of knowledge reserve, which indicates that policy diffusion fails to reach the audience effectively. Therefore, the government and the media should return to the public’s daily life in the early stage of science popularization and publicity. Only by “deeply rooted in the hearts of the people” can we improve the “master” consciousness of each resident, improve the participation rate of public waste classification, and turn cognition and attitude into practical action. Second, strengthen policy support for waste classification infrastructure. Among the topics of waste classification policy perceived by the public, the chaotic collection and transportation of garbage trucks, the regular and fixed-point delivery of garbage cans, and the lack of community staffing are the key topics. The lag of infrastructure will inevitably affect the smooth implementation and promotion of waste classification policy. Therefore, we should strengthen policy support for waste classification infrastructure and improve the construction of waste classification facilities.

Third, establish an effective policy demand feedback mechanism. Big data is the key to improving the supply efficiency of public policies and innovating social governance models. Waste classification belongs to the environmental protection category, including the scope of social public policy services, and it is a typical public good. Promote the supply-side reform of public policy, pay particular attention to the expression of policy needs of the broad masses of the people, and strengthen the communication and interaction between the government and society. Through the establishment of policy demand expression and feedback mechanism to ensure the effectiveness of obtaining public policy demand information, make reasonable supply arrangements. However, at present, the public feedback mechanism of waste classification policy is relatively lacking, and the public’s emotional evaluation, questioning, and other perceived information about relevant policies have not received corresponding attention and response, thus reducing the public participation rate, and affected the implementation effect of the policy. Therefore, it is necessary to establish a policy demand expression and feedback mechanism based on cyberspace, timely understand the public’s demands in the implementation of waste classification policy and master the public’s feedback and suggestions to effectively promote the improvement of the implementation of waste classification policy and the matching between policy supply and demand.

Limitation and prospects

Besides the implications, this study has some limitations that can be addressed in future studies. First, this article tentatively puts forward the research framework of public perception of environmental policy based on network text analysis. Compared with other methods, the network data based on Weibo can extract relevant information from the public more effectively. Admittedly, only the information extracted from Weibo is limited and cannot fully represent the public’s ideas because many people still do not use Weibo. Future research can comprehensively adopt the multiplatform comparison method to capture the public’s perception of environmental policies comprehensively. Second, in terms of information processing, this article combines computer and manual information screening, which ensures the accuracy of information to a certain extent, but it also invests more manual energy in training set data annotation. In future research, the efficiency of information screening can be improved by constructing a corresponding corpus and knowledge base and applying machine learning methods. Finally, the scope of public perception studied in this article is limited to the public’s cognition and emotion of environmental policy, future research may focus on the transformation process from Chinese public cognition and emotion to subsequent behavior or explore the global participation.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.

Author contributions

WW: conceptualization, methodology, and formal analysis. JD: supervision, fund acquisition, and project administration. FS: visualization, writing—review and editing, and validation. XD: conceptualization, writing—original draft preparation, methodology, software, and formal analysis. XZ: methodology and data curation. All authors contributed to the article and approved the submitted version.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

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