Divergent contributions of acidic and neutralization potential to precipitation acidity across Islet, Urban and Forest sites, northern Taiwan
Journal
Environmental Pollution
Journal Volume
406
Start Page
128630
ISSN
0269-7491
Date Issued
2026-10
Author(s)
Abstract
This study investigated 20-year trends (2004-2024) in precipitation pH and major ion chemistry across three environmentally contrasting sites in northern Taiwan, an offshore islet (Penjayu), an urban site (Taipei), and a forest site (Fushan). During the study period, the deposition of SO42-, the dominant acidifying ion, showed similar deposition across sites, ranging from 52 to 65 kg ha−1 yr−1. At Penjayu, rainwater chemistry was dominated by Cl− (254 kg ha−1 yr−1) and Na+ (142 kg ha−1 yr−1), reflecting its oceanic background. All ions except Ca2+ showed significant declines in both concentration and deposition. Higher deposition of NO3−, NH4+, and Ca2+ was observed in Taipei than at the other two sites, likely due to strong anthropogenic influences. Although H+ and SO42- deposition declined, NO3−, K+, Mg2+, and Ca2+ deposition increased after 2020 in Taipei. At Fushan, H+ and SO42- deposition, as well as NH4+ and Mg2+ deposition, declined significantly, whereas Ca2+ deposition remained stably low. Despite these differences among the three sites, precipitation pH increased significantly at all three sites. At Penjayu and Taipei, pH remained above 5.0 after 2015 and 2020, respectively, whereas at Fushan it did not consistently exceed 5.0 until 2024, indicating a delayed recovery. Our findings suggest that a decreasing acidifying potential, combined with stable or increasing neutralization potential, promoted pH recovery in Penjayu and Taipei. In contrast, a concurrent decline in acidic potential and neutralization potential at Fushan likely constrained recovery. These results indicate that, in addition to reductions in acidifying inputs, cation buffering plays a critical role in the recovery of precipitation pH.
Subjects
Acidic potential
Cation buffering
Delayed acidification recovery
Islet-urban-forest environmental gradients
Neutralization potential
Publisher
Elsevier BV
Type
journal article