China News Service, May 18th. According to the official Weibo news of the Ministry of Ecology and Environment, the Ministry of Ecology and Environment today announced the state of surface water and ambient air quality throughout the country in April and January to April 2021.

In terms of ambient air, in April, the average number of days with good air quality in 339 cities at the prefecture level and above was 92.5%, an increase of 3.8 percentage points from the same period last year; from January to April, the average number of days with good air quality in 339 cities at the prefecture level and above was 83.8 %, a year-on-year decrease of 0.9 percentage points.

Surface water

Overall situation

　　In April, among the 3641 national surface water assessment sections, the proportion of sections with good water quality (Class I to III) was 79.8%, a year-on-year decrease of 0.4%; the proportion of sections inferior to Class V was 2.0%, a year-on-year decrease of 1.1%.

The main pollution indicators are chemical oxygen demand, permanganate index and total phosphorus.

National surface water quality category ratio in April

　　From January to April, among the 3641 national surface water assessment sections, 81.9% of the sections with good water quality (Class I to III) were up by 1.0% year-on-year; the ratio of sections with poor water quality was 2.1%, down by 0.9% year-on-year.

The main pollution indicators are chemical oxygen demand, permanganate index and total phosphorus.

Proportion of surface water quality categories nationwide from January to April

Water quality status of main rivers

　　In April, the seven major river basins including the Yangtze River, the Yellow River, the Pearl River, the Songhua River, the Huaihe River, the Haihe River and the Liaohe River, as well as the northwestern rivers, the southwestern rivers, and the rivers in Zhejiang and Fujian Provinces had good water quality (class I to III). The percentage of cross-sections was 81.1%, a year-on-year decrease of 0.4. Percentage points; the proportion of sections inferior to Category V was 1.8%, a year-on-year decrease of 1.1 percentage points.

The main pollution indicators are chemical oxygen demand, permanganate index and five-day biochemical oxygen demand.

Among them, the water quality of the rivers in the northwest, the Yangtze River basin, Zhejiang-Fujian rivers and the rivers in the Southwest is excellent, the water quality of the Pearl River, Liaohe and Yellow River basins is good, and the Huaihe, Haihe and Songhua River basins are lightly polluted.

The proportion of water quality in the seven major river basins and the rivers in the southwest, northwest and Zhejiang and Fujian provinces in April

　　From January to April, the seven major river basins including the Yangtze River, the Yellow River, the Pearl River, the Songhua River, the Huaihe River, the Haihe River and the Liaohe River, as well as the rivers in the northwest, southwest and Zhejiang and Fujian provinces, had good water quality (class I to III). An increase of 1.5 percentage points; the proportion of sections inferior to Category V was 2.1%, a year-on-year decrease of 1.1 percentage points.

The main pollution indicators are chemical oxygen demand, permanganate index and five-day biochemical oxygen demand.

Among them, the water quality of the rivers in the southwest, the northwest, the Yangtze River basin and the rivers in Zhejiang and Fujian are excellent; the water quality in the Pearl River, Liaohe and Yellow River basins is good; the Huai River, Songhua River and Haihe River basins are lightly polluted.

From January to April, the water quality categories of the seven major river basins and the rivers in the southwest, northwest and Zhejiang and Fujian provinces

Water quality and nutritional status of key lakes (reservoirs)

　　In April, among the 200 key lakes (reservoirs) monitored, the number of lakes and reservoirs with good water quality (Class I to III) accounted for 78.5%, an increase of 0.5% year-on-year; the number of lakes and reservoirs with poor water quality accounted for 5.0%. A year-on-year decrease of 2.0 percentage points.

The main pollution indicators are total phosphorus, chemical oxygen demand and permanganate index.

Among the 194 lakes (reservoirs) monitored for nutritional status, 11 were moderately eutrophic, accounting for 5.7%; 24 were mildly eutrophic, accounting for 12.4%; the rest of the lakes (reservoirs) were in the state of medium nutrition and poor nutrition.

Among them, Taihu Lake is lightly polluted and mildly eutrophic, and the main pollution index is total phosphorus; Chaohu Lake is lightly polluted and moderately eutrophication, and the main pollution index is total phosphorus; Dianchi Lake is lightly polluted and moderately eutrophic, and the main pollution index is total phosphorus. The pollution indicators are total phosphorus, permanganate index and chemical oxygen demand; Danjiangkou Reservoir has excellent water quality and poor nutrition; Erhai Lake has excellent water quality and medium nutrition; Baiyangdian Lake has good water quality and medium nutrition.

Compared with the same period last year, the water quality of Dianchi Lake and Erhai Lake has improved, the water quality of Chaohu Lake has declined, and the water quality of Taihu Lake, Danjiangkou Reservoir and Baiyang Lake has no obvious changes; the nutritional status of Chaohu Lake has declined, and the water quality of Taihu Lake, Dianchi Lake, Danjiangkou Reservoir, Erhai Lake and Baiyang Lake has declined. There was no significant change in nutritional status.

　　From January to April, among the 205 key lakes (reservoirs) monitored, the number of lakes and reservoirs with good water quality (Class I to III) accounted for 76.1%, an increase of 0.7% year-on-year; the number of lakes and reservoirs with poor water quality of Class V accounted for 4.9 %, an increase of 0.5% year-on-year.

The main pollution indicators are total phosphorus, chemical oxygen demand and permanganate index.

Among 202 lakes (sinks) monitored for nutritional status, 7 were moderately eutrophic, accounting for 3.5%; 36 were mildly eutrophic, accounting for 17.8%; the rest of the lakes (storages) were in a mesotrophic and oligotrophic state.

Among them, Taihu Lake and Chaohu Lake are lightly polluted and mildly eutrophic, and the main pollution index is total phosphorus; Dianchi Lake is lightly polluted and moderately eutrophic, and the main pollution indicators are chemical oxygen demand, total phosphorus and permanganate. Index: Danjiangkou Reservoir and Erhai Lake are both excellent and moderately nutritious; Baiyangdian Lake is of good quality and moderately nutritious.

Compared with the same period last year, the water quality of Chaohu Lake has declined, and the water quality of Taihu Lake, Dianchi Lake, Danjiangkou Reservoir, Erhai Lake and Baiyang Lake has no obvious changes; the nutritional status of Dianchi Lake has decreased, and the nutrition status of Taihu Lake, Chaohu Lake, Danjiangkou Reservoir, Erhai Lake and Baiyang Lake has no obvious changes. Variety.

National surface water assessment section ranking of cities at prefecture level and above

　　From January to April, among the prefecture-level and above cities in the country, 30 cities including Jiayuguan, Liuzhou, and Qiandongnan Prefecture have relatively good water environment quality at the national surface water assessment sections (from 1st to 30th), Luliang, Ulan The water environment quality of the national surface water assessment sections in 30 cities including Chabu and Wujiaqu City is relatively poor (from the bottom to the bottom 30).

From January to April 2021, the top 30 cities and their water bodies in the water environment quality of the national surface water assessment section

From January to April 2021, the bottom 30 cities and their water bodies in the water environment quality of the national surface water assessment section

Ambient air

Overall situation

　　In April, the average number of days with good air quality in 339 prefecture-level and above cities across the country was 92.5%, a year-on-year increase of 3.8 percentage points; the average PM2.5 concentration was 28 micrograms/m3, a year-on-year decrease of 15.2%; the average PM10 concentration was 55 micrograms /M3, a year-on-year decrease of 11.3%; the average O3 concentration was 129 μg/m3, a year-on-year decrease of 11.6%; the average SO2 concentration was 8 μg/m3, a year-on-year decrease of 20.0%; the average NO2 concentration was 23 μg/m3, a year-on-year decrease A decrease of 11.5%; the average CO concentration was 0.9 mg/m3, which was the same year-on-year.

　　From January to April, the average number of good days in 339 prefecture-level and above cities across the country was 83.8%, down 0.9% year-on-year; the average PM2.5 concentration was 41 micrograms/m3, down 2.4% year-on-year; the average PM10 concentration was 70 micrograms /M3, an increase of 7.7% year-on-year; the average concentration of O3 was 117 micrograms/m3, a year-on-year decrease of 4.9%; the average SO2 concentration was 11 micrograms/m3, which was the same year-on-year; the average concentration of NO2 was 27 micrograms/m3, a year-on-year increase of 12.5 %; The average CO concentration is 1.3 mg/m3, a year-on-year decrease of 7.1%.

Proportion of days of each level in 339 prefecture-level and above cities nationwide from January to April 2021

Concentrations and year-on-year changes of the six indicators in 339 prefecture-level and above cities across the country from January to April 2021

Key area

　　In April, the average number of good days in "2+26" cities in Beijing-Tianjin-Hebei and surrounding areas was 84.5%, an increase of 4.4 percentage points year-on-year; the PM2.5 concentration was 39 micrograms/m3, a year-on-year decrease of 2.5%.

From January to April, the average number of good days was 63.2%, a decrease of 0.3% year-on-year; the PM2.5 concentration was 58 micrograms/m3, a year-on-year decrease of 14.7%.

　　The proportion of good days in Beijing in April was 90.0%, a year-on-year increase of 6.7 percentage points; the PM2.5 concentration was 31 micrograms/m3, a year-on-year increase of 6.9%.

From January to April, the proportion of good days was 66.7%, a year-on-year decrease of 15.9 percentage points; the PM2.5 concentration was 53 micrograms/m3, a year-on-year increase of 15.2%.

　　The average number of good days in April in 41 cities in the Yangtze River Delta was 94.2%, an increase of 5.8 percentage points year-on-year; the PM2.5 concentration was 30 micrograms/m3, a year-on-year decrease of 14.3%.

From January to April, the average number of good days was 89.1%, an increase of 2.6 percentage points year-on-year; the PM2.5 concentration was 39 micrograms/m3, a year-on-year decrease of 7.1%.

　　The average number of good days in the 11 cities in the Fenwei Plain in April was 88.2%, which was the same year-on-year; the PM2.5 concentration was 36 micrograms/m3, a year-on-year decrease of 5.3%.

From January to April, the average number of good days was 65.5%, a year-on-year increase of 1.3 percentage points; the PM2.5 concentration was 58 micrograms/m3, a year-on-year decrease of 14.7%.

Ranking of key cities

　　In April, among the 168 key cities, the air quality of Harbin, Tangshan, and Xinxiang was relatively poor (from the bottom to the bottom 20th); the air quality of cities such as Haikou, Lhasa, and Ya'an was relatively good ( From 1st to 20th).

List of 168 key cities in the top 20 and bottom 20 cities in April 2021

　　From January to April, among the 168 key cities, the air quality in Tangshan, Xianyang, and Anyang was relatively poor (from the bottom to the bottom 20); the air quality in Lhasa, Haikou, and Zhoushan was relatively good (From 1st to 20th).

List of top 20 and bottom 20 cities in 168 key cities from January to April 2021