Xinfeng Zhao

Rapid urbanization exacerbates atmospheric pollutant emissions, markedly altering precipitation chemistry. However, a comprehensive understanding of the equilibrium between multicomponent precipitation chemistry and urbanization remains unclear. This study characterizes the spatiotemporal urbanization dynamics of the Pearl River Delta (PRD) urban agglomeration from 2000 to 2020 by integrating multi-source datasets, including nighttime light (NTL) observations, Landsat-derived land cover, and gridded population products. The interplay between precipitation chemistry and urbanization was evaluated through a multidimensional equilibrium assessment framework integrating spatial heterogeneity, trade-off and synergy analysis, and decoupling diagnosis. The results indicated that interannual variation in precipitation ion concentrations initially increased and then decreased from 2000 to 2020. Spatially, major ion concentrations (SO₄²⁻, NO₃⁻, Ca²⁺, and NH₄⁺) generally declined across the region after 2009, with the most pronounced declines in peripheral PRD areas. Conversely, urbanization intensified, spreading from the central core to the periphery. NTL intensity exhibited the strongest explanatory power for major ion concentrations, suggesting that economic urbanization is more closely associated with spatial variability in precipitation chemistry. Over time, the relationship between precipitation ion concentrations and urbanization shifted from synergy to trade-off. After 2005, the dominant decoupling status of major ion concentrations relative to urbanization shifted from expansive negative decoupling (up to 62.93%) to strong decoupling (up to 75.86%). This shift indicates that the antagonism between urbanization and precipitation pollution has gradually transitioned toward equilibrium. However, this equilibrium exhibits spatiotemporal non-stationarity. These findings highlight the complex nonlinear interactions between urbanization and precipitation chemistry. Identifying spatial heterogeneity in decoupling between urbanization and environmental pollution facilitates the formulation of differentiated zoning management strategies.

This study elucidates soil–climate regulatory mechanisms on regional health baselines in China and hydrogeochemical roles in cardiovascular biomarker differentiation. Utilizing data from 26,759 healthy adult samples across 286 Chinese cities/counties, seven core factors were identified via Pearson correlation analysis from 25 indicators, including longitude (X₁, r = −0.192, p = 0.009), elevation (X₃, r = 0.377, p = 0.001), and precipitation (X₇, r = −0.200, p = 0.006). Ridge regression analysis (R² = 0.714) was subsequently applied to simulate predicted values for 2232 cities/counties. The synergistic effects of soil calcium sulfate content and salinity (X₂₅) on serum cardiac troponin I (cTnI) reference values were rigorously validated, explaining 25.5% of regional cTnI elevation (ΔR² = 0.183). The findings demonstrate that precipitation leaching and groundwater recharge processes collectively drive a 25.5% elevation in cTnI levels in northwestern regions (e.g., Nagqu, Tibet: altitude > 4500 m, annual sunshine > 3000 h) compared to southeastern areas. To mitigate salinity transport dynamics, optimization strategies targeting soil cation exchange capacity (X₁₈/X₁₉) were proposed, providing a theoretical foundation for designing gradient water treatment schemes in high-calcium-sulfate zones (CaSO₄ > 150 mg/L). Crucially, regression equations derived from the predictive model enable the construction of a geographically stratified reference framework for cTnI in Chinese adults, with spatial analysis delineating its latitudinal (R² = 0.83) and longitudinal (R² = 0.88) distribution patterns. We propose targeted strategies optimizing soil cation exchange capacity to mitigate sulfate transport in groundwater, informing geographically tailored water treatment and cardiovascular disease prevention efforts. Our findings provide localized empirical evidence critical for refining WHO drinking water sulfate guidelines, demonstrating direct integration of hydrogeochemistry, water quality management, and public health.

Fine particulate matter is associated with adverse health effects, but exactly which characteristics of PM_2.5 are responsible for this is still widely debated. We evaluated seasonal dynamics of the composition and chemical characteristics of PM_2.5 in Zhuhai, China. PM_2.5 characteristics at five selected sites within Zhuhai city were analyzed. Sampling began on January 10, 2015, and was conducted for 1 year. The ambient mass concentration, carbon content (organic and elemental carbon, OC and EC), level of inorganic ions, and major chemical composition of PM_2.5 were also determined. Average concentrations of PM_2.5 were lower than the National Ambient Air Quality Standard (NAAQS) 24-h average of 65 μg/m³. The daily PM_2.5 concentration in Zhuhai city exhibited clear seasonal dynamics, with higher daily PM_2.5 concentrations in autumn and winter than in spring and summer. Carbon species (OC and EC) and water-soluble ions were the primary components of the PM_2.5 fraction of particles. Apart from OC and EC, chemical species in PM_2.5 were mainly composed of NH₄⁺ and SO₄²⁻. There was a marked difference between the summer and winter periods: the concentrations of OC and EC in winter were roughly 3.4 and 4.0 times than those in summer, while NH₄⁺, SO₄²⁻, NO₃⁻, and Na⁺ were 3.2, 4.5, 28.0, and 5.7 times higher in winter than those in summer, respectively. The results of chemical analysis were consistent with three sources dominating PM_2.5: coal combustion, biomass burning, and vehicle exhaust; road dust and construction; and from reaction of HCl and HNO₃ with NH₃ to form NH₄Cl and NH₄NO₃. However, additional work is needed to improve the mass balance and to obtain the source profiles necessary to use these data for source apportionment.