Shengrong Lou

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.

Winter haze in eastern China is increasingly dominated by particulate nitrate, but its compositions and source contributions remain poorly constrained. We conducted intensive winter observations at a regional site in suburban Shanghai and developed a semi-quantitative single-particle framework combining SPAMS with factor analysis to attribute nitrate to specific particle types and sources in near real time. Nitrate occurred mainly in the accumulation mode (~0.5–0.7 μm), implying high regional persistence. Four nitrate-containing particle classes (NO₃Lv1–Lv4) were identified. A highly aged class (NO₃Lv4) accounted for the largest fraction of both particle number and nitrate mass loadings. This class showed extensive internal mixing with elemental carbon, ammonium, potassium-rich combustion markers, and chloride-depleted sea salt, indicating coupling between secondary inorganic nitrate, combustion emissions, and processed marine aerosol. Episode analysis and factorization further revealed that severe nitrate build-up reflects the co-occurrence of stagnant boundary layers, humid nocturnal heterogeneous formation of both ammonium and non-ammonium nitrate, long-range transport from northern industrial and urban corridors, and marine influence. These results indicate that winter nitrate haze in the Yangtze River Delta is governed by joint NO_x–NH₃ chemistry, primary combustion, and regional transport, requiring coordinated multipollutant control.