**4. Conclusions and Policy Implications**

From the provincial panel data from 2006 to 2017, this paper comprehensively measured and analyzed the impact of the new urbanization and agglomeration of energyintensive industries on NOx emissions in China; at the same time, the systematic GMM method was applied to empirically analyze the impact of China's new urbanization and agglomeration of energy-intensive industries on NOx emissions; what was more, this paper also used the intermediary effect model to explore its impact mechanism.

From above, the conclusions were as follows: (1) There was a negative correlation between new urbanization and NOx emissions. For every 1% increase in the level of new urbanization, the NOx emissions will be reduced by 0.4766%. There was a positive correlation between the agglomeration of energy-intensive industries and NOx emissions. For every 1% increase in the agglomeration of energy-intensive industries, NOx emissions will be increased by 0.1290%. (2) The new urbanization and agglomeration of energyintensive industries have a mutual impact on NOx emissions. The agglomeration of energy-intensive industries' promotion of NOx emissions weakens with the increase in the level of new urbanization. (3) From the research results of the transmission mechanism, it showed that the energy efficiency and human capital reflected the intermediary effect mechanism in the impact of new urbanization on NOx. New urbanization reduces the NOx emissions by improving the energy efficiency and human capital. There are two different mechanisms between the agglomeration of energy-intensive industries and NOx emissions such as: the intermediary effect and masking effect. The industrial structure plays an intermediary role in the agglomeration of energy-intensive industries and NOx emissions, while the mechanism of the energy structure in the agglomeration of the energy-intensive industries and NOx emissions is the masking effect.

From the above conclusions, this paper lists the following suggestions: firstly, the emissions reduction effect of new urbanization shall be given attention to, high-level talent agglomeration is supported and the resource factors shall be invested. At the same time, there is no need in excessively pursuing the development speed of new urbanization, ensuring the quality of development, narrowing the economic and social gaps among regions and realizing urban sustainable development. Secondly, it is scientific and reasonable to guide the agglomeration of energy-intensive industries and optimize the industrial structure, as well as the energy structure. Thirdly, it is also significant to improve the level of scientific and technological governance, as well as give full attention to the ability of coordinated emission reduction.

With the energy transformation continuously promoted, carbon emission reduction, carbon emission peak and carbon neutralization have become the focus of global attention. Next, the research will focus on promoting the coordinated treatment of carbon dioxide and air pollution.

**Author Contributions:** Data curation, Y.Y., and writing—original draft preparation, Y.Y. and T.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by funds from the First-class Discipline Construction of Beijing University of Chemical Technology (XK1802-5).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The datasets used and/or analyzed in the current study are available from the corresponding author upon reasonable request.

**Conflicts of Interest:** The authors declare no conflict of interest.
