No abstract

Long-term exposure to airborne fine particulate matter or PM2.5 is associated with an increase in the long-term risk of premature death that creates critical concerns for public health. This study uses twenty years (2002-2021) of daily remotely sensed data with multi-spatial resolution of 1 km to 3 km to examine the long-term spatiotemporal distribution of PM2.5 across Thailand. Good agreement is found between the in-situ measurements of PM2.5 and instantaneous estimates made from the satellite data with correlation coefficients of 0.51. Based on data analysis during the year 2002- 2021, the region with the highest yearly averaged concentration level of PM2.5 was a central region of Thailand (19.91 μg.m-3) followed by northern (19.11 μg.m-3), northeastern (18.92 μg.m-3), eastern (18.76 μg.m-3) and southern (16.16 μg.m-3) region, respectively. The period with the highest PM2.5 levels were during March and April with monthly averages 23.74 to 26.72 μg.m-3. For the 20-year record, monthly-mean PM2.5 concentration in northern Thailand showed statistically significant increase at the rate of 0.14 μg.m-3 month-1 in dry season, the same as in the northeastern (0.126 μg.m-3month-1), eastern (0.12 μg.m-3 month-1) and Central region (0.083 μg.m-3 month-1). While the southern region has a negative trend (-0.018 μg.m-3 month-1) which is different from other regions. The spatiotemporal variation and changing of PM2.5 concentrations were a result of both changing in meteorological factors and anthropogenic activities. Here, we discuss and present possible explanations for long-term spatiotemporal variation of PM2.5.

This article presents the results of recent research on the historical period of west-central Thailand between the eleventh and thirteenth centuries. At this time Dvaravati was in a stage of decline while the prominent rivals of Pagan and Angkor began to prosper. The construction of stone sanctuaries in the Bayon style in west-central Thailand has caused serious debate regarding the influence of Jayavarman VII over that part of Thailand. However, the main point of the present study is that the successors of Dvaravati can be considered to have played a significant part in the socio-economy of that period. This research explores the landscape of the study region using remote sensing techniques as well as carrying out conventional methods of fieldwork. New discoveries and current evidence are discussed, along with some issues concerning the archaeology of the post-Dvaravati, pre-Sukhothai transitional period (c . a.d. 1100–1300). West-central Thailand is believed to have been an economically desirable land with rich resources throughout its history. It is hoped that this work will contribute to the understanding of the social changes after the Dvaravati period when the economic power shifted to other parts of Mainland Southeast Asia.