Ahmed Nasir, Kurita Naoyuki, Chowdhury Md Abdul Mannan, Gao Jing, Hassan S M Quamrul, Mannan Md Abdul, Mallik Md Abul Kalam, Choudhury Sayeed Ahmed, Bhuiyan Md Abdul Quaiyum, Karim Md Masud
Isotope Hydrology Division, Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, Savar, Bangladesh.
Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan.
Isotopes Environ Health Stud. 2020 Jun;56(3):220-237. doi: 10.1080/10256016.2020.1770245. Epub 2020 Jun 1.
The study investigates the factors that control the isotopic composition of tropical precipitation in Bangladesh. Daily and monthly rainfall samples were collected from three stations from 2013 to 2015: (1) northern and moderately high altitude: Sylhet, (2) middle part of the country (close to Tropic of Cancer): Savar, and (3) southern coastal region: Barisal. To escape from the post-evaporation effect, proper care was adopted. This is supported by the fact that the local meteoric water lines (LMWLs) derived for the daily precipitations of all stations mostly follow the global meteoric water line (GMWL). The results exhibit a clear seasonal and spatial variation in both O and H of precipitation. O is more depleted in samples collected during rainy (monsoon) seasons, while O enrichment is associated to winter and summer (pre-monsoon) seasons. During rainy season, intra-seasonal variability of δO rainfall is clearly seen and remarkable depletion of O is observed during the period of intense convective activity over the Bay of Bengal. This feature indicates that isotope variability in Bangladesh is controlled by large-scale convective activity rather than local rainfall amount.
该研究调查了控制孟加拉国热带降水同位素组成的因素。2013年至2015年期间，从三个站点采集了日降雨和月降雨样本：（1）北部及中等高度地区：锡尔赫特，（2）该国中部（靠近北回归线）：萨瓦尔，以及（3）南部沿海地区：巴里萨尔。为避免蒸发后效应，采取了适当的措施。所有站点日降水量得出的当地大气降水线（LMWL）大多遵循全球大气降水线（GMWL），这一事实支持了上述做法。结果表明，降水的氧和氢均呈现出明显的季节和空间变化。在雨季（季风期）采集的样本中，氧的贫化程度更高，而氧的富集与冬季和夏季（季风前）季节有关。在雨季，降雨δO的季节内变化清晰可见，在孟加拉湾强烈对流活动期间，观测到氧的显著贫化。这一特征表明，孟加拉国的同位素变化受大规模对流活动控制，而非当地降雨量。
