Effective mapping and monitoring of soil moisture content (SMC) in space and time is an expected application of remote sensing for agricultural development and drought mitigation, particularly in the context of global climate change impact, given that agricultural drought is occurring more frequently and severely worldwide. This study aims to develop a regional algorithm for estimating SMC by using Landsat 8 (L8) imagery, based on analyses of the response of soil reflectance, by corresponding L8 bands with the change of SMC from dry to saturated states, in all 103 soil samples taken in the central region of Vietnam. The L8 spectral band ratio of the near-infrared band (NIR: 850–880 nm, band 5) versus the short-wave infrared 2 band (SWIR2: 2110 to 2290 nm, band 7) shows the strongest correlation to SMC by a logarithm function (R2 = 0.73 and the root mean square error, RMSE ~ 12%) demonstrating the high applicability of this band ratio for estimating SMC. The resultant maps of SMC estimated from the L8 images were acquired over the northern part of the Central Highlands of Vietnam in March 2015 and March 2016 showed an agreement with the pattern of severe droughts that occurred in the region. Further discussions on the relationship between the estimated SMC and the satellite-based retrieved drought index, the Normal Different Drought Index, from the L8 image acquired in March 2016, showed a strong correlation between these two variables within an area with less than 20% dense vegetation (R2 = 0.78 to 0.95), and co-confirms the bad effect of drought on almost all areas of the northern part of the Central Highlands of Vietnam. Directly estimating SMC from L8 imagery provides more information for irrigation management and better drought mitigation than by using the remotely sensed drought index. Further investigations on various soil types and optical sensors (i.e., Sentinel 2A, 2B) need to be carried out, to extend and promote the applicability of the prosed algorithm, towards better serving agricultural management and drought mitigation.

High concentration of ammonium was detected in groundwater in southern Hanoi, Vietnam while municipal solid waste (MSW) landfills were known to generate large amounts of NH4 + . Thus, bottom barrier with well performance should be required in Hanoi MSW landfills to minimize NH4 + migration. Hanoi is expected to experience temperature increase, which enables to reduce hydraulic-barrier performance. Hence, study on temperature effect on NH4 + adsorption and diffusion through landfill barriers plays a key role in prevention of NH4 + contaminated aquifers. The objective is to evaluate effect of three kinds of temperature ( 20o C, 35 o C and 50 o C) on NH4 + adsorption and diffusion through GCL and in-situ clayey soil sampled in Hanoi (HN clay). The results show that GCL possesses higher non-linear partitioning coefficient (Kd*) and lower diffusion coefficient (De) than HN clay in all cases of temperature. Both GCL and HN clay experienced an increase of Kd* and De in the temperature range of 20 o C and 35 o C. When temperature rises to 50 o C, Kd* tends to decrease but De keep increasing. Hence, the study indicates a more dominant effect of diffusion coefficient than non-linear partitioning coefficient in promotion of ammonium mass transport through HN clay.