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Abstract Oxygen isotope anomaly of nitrate aerosol (∆17O-NO3 −) contributes to understanding the atmospheric nitrogen chemistry in the polar oceans. Here, ∆17O-NO3 − of the aerosol samples was analyzed based on a cruise from East Asia to the Arctic Ocean to explore the nitrate formation mechanisms. ∆17O-NO3 − decreased with the increase of latitude, especially when after entering the Arctic Circle. ∆17O-NO3 − (e.g., 11.5‰–21.2‰) was extremely low while crossing the sea ice-covered Arctic Ocean. This is most likely influenced by the combined enhancement of hydroxyl (OH) and peroxy (HO2 + RO2) radicals derived by sea ice under permanent sunlight period. In addition, the obvious increase in the ∆17O-NO3 − of return trip with shortened daytime indicated the advantage of nocturnal pathways (NO3 related) with the higher ∆17O endmembers. The mutation of ∆17O-NO3 − can reflect the change of NOx conversion pathways to nitrate, and it can be more sensitive to the change of radical chemistry related to atmospheric oxidation.

Inland lakes play a crucial role in monitoring global climate change and managing responses to extreme weather events, with lake elevation being critical for assessing their regulatory capacities. However, due to the limited temporal resolution of current altimetry satellites, obtaining high-frequency, high-precision elevation data for water bodies remains challenging. Consequently, most studies utilize elevation-area (E-A) models constructed from historical elevation and area records, integrated with area observations from high-temporal resolution optical satellites to infer precise water levels. Yet, the construction of the E-A model often assumes a uniform water level across the lake, thus overlooking potential segmentation during dry periods. To address this, our study implemented a zone-based approach, utilizing hydrological connectivity principles to ensure that elevation data within E-A models are confined to appropriate zonal regions. This method effectively minimized uncertainties by preventing errors from zonal discrepancies, significantly improving accuracy compared to traditional methods. It reduced root mean square errors (RMSE) by 0.71–1.73 m during the dry season, achieving RMSEs of 0.35, 0.64, and 0.37 m across three segments. Furthermore, this method ensures water level data are confined to specific zones, preventing the inconsistencies typically caused by averaging data across multiple stations or selecting data from varying elevations. This consistent domain definition reduces extrapolation errors during the model prediction and inversion. Moreover, the method compensates for time information losses often incurred by relying on multi-year percentile charts, thereby enabling more precise aquatic boundary delineation than traditional regional boundaries.

Biomass burning can significantly impact the chemical and optical properties of carbonaceous aerosols. Here, the impacts of biomass burning emissions on chemical and optical properties of carbonaceous aerosols were studied during wintertime in a megacity of Nanjing, East China. The high abundance of biomass burning tracers such as levoglucosan (lev), mannosan (man), galactosan (gal) and non-sea-salt potassium (nss-K+) was found during the studied period with the concentration ranges of 22.4-1476ngm-3, 2.1-56.2ngm-3, 1.4-32.2ngm-3, and 0.2-3.8μgm-3, respectively. Backward air mass origin analysis, potential emission sensitivity of element carbon (EC), and MODIS fire spot information indicated that the elevations of the carbonaceous aerosols were due to the transported biomass-burning aerosols from Southeast China. The characteristic mass ratio maps of lev/man and lev/nss-K+ suggested that the biomass fuels were mainly crop residuals. Furthermore, the strong correlation (p<0.01) between biomass burning tracers (e.g. lev) and light absorption coefficient (babs) for water soluble organic carbon (WSOC) revealed that biomass burning emissions played a significant role in the light-absorption properties of carbonaceous aerosols. The solar energy absorption due to water-soluble brown carbon (BrC) and EC was estimated by the calculation-based on measured light-absorbing parameters and the simulation-based on a radiative transfer model (RRTMG_SW). The solar energy absorption of water-soluble BrC in short wavelengths (300-400nm) was 0.8±0.4 (0.2-2.3)Wm-2 from the calculation-based and 1.2±0.5 (0.3-1.9)Wm-2 from the RRTMG_SW model. The absorption capacity of water-soluble BrC accounted for about 20-30% of the total absorption of EC aerosols. The solar energy absorption of WSOC due to biomass burning was estimated as 0.2±0.1 (0.0-0.9)Wm-2. Potential Source Contribution Function model simulations showed that the solar energy absorption induced by WSOC and EC aerosols was mostly due to the regional transported carbonaceous aerosols from the source regions such as southeast China. Our results illustrate the importance of the absorbing water-soluble brown carbon aerosols in trapping additional solar energy in the low-level atmosphere, heating the surface and inhibiting the energy from escaping the atmosphere. The regional transported biomass burning emissions may significantly impact the chemical and optical properties of carbonaceous aerosols in the polluted atmosphere. [ABSTRACT FROM AUTHOR]