## 3 Results and Discussion
### The Literature and References  
#### 3.5.1 The Literature Analysis  
Analyzing significant articles within the field is essential for understanding the research domain. Citations serve as a crucial indicator of the impact of research work. Therefore, we created a subset consisting of the top 5 review articles and 25 articles with the highest citations from the BCL dataset for further analysis. Figure 7 visually represents this subset through a network graph generated with Bibliometrix's Historiograph tool. Each node in the graph represents an article, identified briefly by the authors' names and publication year. Detailed information, including article titles and citation counts, can be found in Supplementary Information (SI) Table S7. Links between nodes indicate citation relationships. Notably, the size of a node correlates positively with its local citation rate within the network. Nodes connected by links or sharing connections belong to the same knowledge network, while different knowledge networks are depicted in distinct colors. However, due to the constraint of a limited number of nodes, certain articles belonging to the same knowledge network may be segregated into different networks, particularly in non-mainstream knowledge networks. Figure 7 illustrates that there is a mainline network of this subset, represented by the red nodes. Within the mainline network in Figure 7, the study of [PERSON] (2001) [24] stands as the most locally cited article, which conducted model simulations to investigate the evolution of aerosol chemical composition. The findings reveal that the coagulation and growth of  
Figure 7: Network graph of the top 5 review articles and the top 25 articles in terms of citations [1; 2; 6; 11; 24; 40; 49; 52; 53; 55; 56; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91; 92; 93; 94; 95; 96; 97; 98; 99]. Each node represents an article, and articles with citation relationships are represented using the same color. aerosol particles drive the mixing state of black carbon components toward internal mixing. Consequently, it suggests a potentially higher positive radiative forcing of black carbon than previously estimated, speculating that black carbon's direct radiative forcing could be the second most significant component after carbon dioxide. This study highlights the crucial impact of black carbon's mixing state on aerosol direct radiative forcing, thereby significantly influencing global climate. The most cited article in the mainline network in Figure 7 is that of [PERSON] et al. (2013) [6], a comprehensive review article. This study meticulously summarizes the characteristics, emissions, and quantity of black carbon. This study provides a thorough evaluation of black carbon's climate forcing, including direct radiative forcing, cloud effects, and snow-ice effects, and offers a comprehensive analysis of black carbon's climate impacts. Moreover, it analyzes and summarizes evaluation indicators and emission reduction strategies for black carbon and its sources. By integrating known processes and estimating the major forcing terms of black carbon, this research suggests a total climate forcing of +1.1 W/m\({}^{2}\) for black carbon, making black carbon the second-largest climate forcing factor after carbon dioxide. These findings lay a crucial foundation for further exploration of the impacts of black carbon. In Figure 7, the purple and pink branches, which belong to a unified knowledge network focusing on carbonaceous substances in soil, appear disconnected due to the limited number of nodes. Within this network, the most cited article is that of [PERSON] et al. (2011) [55], a review article that emphasizes the potential of biochar as a soil amendment to enhance fertility and mitigate climate change. It indicates that research on biochar's impact on soil biota is limited. Although biochar can increase microbial biomass and alter community composition, the underlying mechanisms remain unclear.