Temporal and spatial variation in atmospheric wet deposition of nutrients and organic matter at the southern and northern foothills of the Qinling Mountains

Abstract

Wet deposition significantly impacts the basin ecosystem and water quality of the Qinling Mountains (QMs). However, few research focused on the difference in wet deposition between the northern (QN) and southern (QS) foothills due to the barrier effect of the QMs. This two-year investigation studied nutrient and organic matter deposition in QN and QS during summer and autumn. Results showed higher concentrations of nitrogen (N), phosphorus (P), dissolved organic carbon (DOC), and permanganate index (CODMn) in QN's rainwater, particularly in autumn. The CODMn in QN ranged 0.59–7.67 mg/L, and DOC ranged 0.64–4.45 mg/L. For QS, the CODMn ranged 0.71–3.25 mg/L, and DOC ranged 0.28–2.62 mg/L. Backward trajectory analysis revealed the accumulation of pollutants in QN originating from Northern China, intensified by autumn heating and straw burning. Tyrosine-like and humic-like components in rainwater DOM suggested that they primarily originated from autochthonous sources. Rainwater N:P mass ratios range from 39:1 to 145:1, highlighting a higher N input than P in QMs' wet deposition. The findings underscore the importance of atmospheric wet deposition in nutrient and organic matter input to the QMs and establish a foundation for exploring the ecological effects of wet deposition.