Beijing's annual average concentration of major airborne fine particulate matter, or PM2.5, was recorded at 32 micrograms per cubic meter in 2023, which means the capital has achieved the national air quality standards for three consecutive years, according to the city's ecology and environment bureau on Wednesday.

The number was 33 micrograms per cubic meter in 2021 and 30 micrograms per cubic meter in 2022, which was the best air quality for the city since 2013.

The capital has made great efforts to fight air pollution in the past decade. Multiple measures have been taken, and citizens have seen clearer skies in recent years.

In 2023, Beijing witnessed a significant improvement in air quality. Approximately 90 percent of days were classified as good air quality, with a record-breaking continuous stretch of 192 consecutive good days for PM2.5, 20 days more than the previous year.

Back in 2013, there were only 13 days recorded as good days for PM2.5, according to the bureau.

The reductions in PM2.5, PM10, NO2, and SO2 in Beijing from 2013 to 2023 were 64.2 percent, 43.6 percent, 53.6 percent, and 88.7 percent, respectively, indicating a fundamental improvement in air quality.

Compared to the PM2.5 in 2022, the number for 2023 slightly increased by 2 micrograms per cubic meter. Zhang Qiang, professor and associate head of the Department of Earth System Science at Tsinghua University, identified three factors influencing this change.

"Firstly, social and economic activities returned to normal levels in 2023 since the control measures for the pandemic were lifted in China, which has led to increased emissions," Zhang said. "Secondly, the El Nino in 2023 had a somewhat unfavorable impact, increasing regional pollution transport and deteriorating diffusion conditions."

"Additionally, the year 2023 saw an increase in the frequency of dust storms, reaching the highest level in the past decade," he added.

These factors contributed to the challenges faced in maintaining and improving air quality in Beijing, according to Zhang.