Moss differentiating the fluxes and sources of nitrogen deposition between 1984 and 2021 in a mountain area of Northern China.

Anthropogenic reactive nitrogen (N) deposition has increased significantly since the industrial revolution. Northern China has become a global hotspot for N deposition. However, few studies have been conducted to quantify the historical changes of atmospheric N deposition fluxes and source contributions in Northern China. By investigating N contents and δN values of mosses at Mount Tai (Northern China) in 1984 and 2021, we reconstructed fluxes and source contributions of wet inorganic N deposition and evaluated their historical changes. Compared with 1984, moss N contents (from 1.7 ± 0.3% to 2.1 ± 0.4%) showed a significant increase in 2021, which was mainly attributed to a significant increase in nitrate N deposition fluxes at Mount Tai. Moss δN values (from -5.9 ± 0.9‰ to -5.2 ± 2.4‰) showed a slight increase from 1984 to 2021 at Mount Tai. The importance of combustion-related NH (including vehicle exhaust, coal combustion, and biomass burning) in 2021 (51.2%) were higher than those in 1984 (43.9%), while the importance of volatilization NH sources (including waste and fertilizers) in 2021 (48.8%) were lower than those in 1984 (56.1%). It was fossil-fuel NO (from vehicle exhaust and coal combustion) (54.1%) rather than non-fossil fuel NO (from biomass burning and microbial N cycles) (45.9%) dominated NO emissions in both 1984 and 2021. Our results revealed significant contributions of combustion-related NH and fossil-fuel NO sources emissions to the elevation of N deposition at Mount Tai in Northern China, which are beneficial for mitigating N emissions and conducting ecological benefit assessments in Northern China.