The presence of cracks significantly impacts the hydrological behaviour of clay embankments. This study aimed to enhance understanding of the complex interplay between the amount and propagation of desiccation cracks and seasonal variations. A full-scale embankment was constructed and equipped with an array of instruments, including pore water pressure, volumetric water content (VWC), and crack observer. The results suggested that continues cracks at shallow depths (0.5 m) exhibit significant seasonal fluctuations due to pronounced soil-atmosphere interactions, facilitating rapid water movement and substantial changes in crack width. In contrast, discontinuous cracks at intermediate depths (0.5 m) are less affected by seasonal changes, but they can propagate and connect over time due to repeated wetting and drying cycles. The crack intensity factor (CIF) above 0.4 m is highly sensitive to climatic variations, leading to pronounced fluctuations with changes in rainfall and dry conditions. The twofold increase in CIF values leads to a significant reduction in VWC (by 13.5%) at the depth of 0.25 m under the same atmospheric water balance. However, this effect is less pronounced at greater depths, such as 0.5 m, as discontinuous cracks are less effective in facilitating rapid drainage and moisture loss.

The optical properties and sources of brown carbon (BrC) have been poorly constrained in climate models due to the variability of spatiotemporal characteristics, impeding the accurate understanding of its impact on air quality and climate. In this study, daily PM2.5 samples, which were collected from January to November 2021 in urban Taipei, Taiwan, and seasonal variations of optical properties of water-soluble and methanol-soluble organic carbon (WSOC and MSOC) were evaluated. The light absorption coefficients at 365 nm (Abs(365)) of both extracts, which strongly correlated with WSOC and MSOC mass concentrations, displayed distinct seasonal variations with the highest in winter and the lowest in summer. The Absorption Angstrom Exponent of WSOC and MSOC ranged from 4.16 to 7.75 and 4.03-6.83, with averages of 6.05 +/- 0.56 and 5.29 +/- 0.61, respectively. The mass absorption efficiency (MAE(365)), which normalizes the Abs(365) of both extracts to the mass of WSOC and MSOC, showed significant seasonal difference with the high MAE(365), (WSOC) of 0.96 +/- 0.29 m(2) g(-1) in winter and the lowest in summer of 0.49 +/- 0.07 m(2) g(-1), whereas contrasting with the largest MAE(365), (MSOC) of 0.99 +/- 0.46 m(2) g(-1) in summer and the lowest in winter of 0.66 +/- 0.28 m(2) g(-1), respectively. Fossil fuel combustion, such as traffic emission, and biomass burning, such as crematorium, were identified to be important contributors to light-absorbing substances. The estimated fractional radiative forcing by WSOC and MSOC to elemental carbon was most significant during winter (8.15 +/- 3.77%) and spring (13.90 +/- 4.38%), respectively, which may greatly affect the atmospheric photochemistry and climate. This study suggests that the impact of BrC in Taiwan on the local and regional air quality and climate is non-negligible.