Mohan M P, D'Souza Renita Shiny, Rashmi Nayak S, Kamath Srinivas S, Shetty Trilochana, Sudeep Kumara K, Yashodhara I, Mayya Y S, Karunakara N
Centre for Advanced Research in Environmental Radioactivity, Mangalore University, Mangalagangothri, 574 199, India.
Centre for Advanced Research in Environmental Radioactivity, Mangalore University, Mangalagangothri, 574 199, India; Department of Chemical Engineering, Indian Institute of Technology-Bombay, Mumbai, 400 076, India.
J Environ Radioact. 2018 Dec;192:194-207. doi: 10.1016/j.jenvrad.2018.06.018. Epub 2018 Jul 4.
As a part of establishing a regional database on natural radioactivity, the atmospheric concentrations of Pb and Be were measured over a three and half year period (2014-2017) in Mangalore and Kaiga in the South West Coast of India. A total of 99 air samples, collected in the different months of the year, were analysed in this study. The mean activity concentrations of Be and Pb were found to be 5.5 ± 3.1 mBq m and 1.1 ± 0.73 mBq m, respectively. Both the radionuclides exhibited strong seasonal variations, with maximum concentration of Be occurring in the summer and that of Pb in the winter season. The concentration of both the radionuclides was minimum in the rainy season. Higher Pb concentration during winter was attributed to the ingression of continental air masses due to the wind regime from the North East. The sunspot number index of the solar activity also plays an important role in the increase and decrease of Be concentration in the air. A clear trend of increased and lowered concentration of Be with lower and higher solar activity (low and high sunspot number), respectively, in accordance with the 11-year solar cycle, was observed in this study. The temporal variation of PM concentration was also studied and it showed maximum value in the winter and minimum in the rainy season with an average of 56.9 μg m. Statistically significant positive correlation was observed between the PM and Pb activity concentration, whereas a weak correlation was observed between PM and Be. This is due to the fact that Be is largely associated with sub-micrometer size particles, whereas PM is contributed by larger sizes. The dependence of the activity concentrations of Be and Pb with meteorological parameters such as rainfall, temperature, and humidity was studied through linear regression analysis. A significant correlation was observed between Be and Pb concentrations with rainfall intensity (with identical correlation coefficients), which suggested that the removal mechanisms of these two radionuclides were similar. Be showed a strong correlation with temperature, whereas Pb with humidity. A comparison of the data obtained in the present study for the South West Coast of India with the global literature values of Be and Pb in aerosols showed that the values did not reflect the well-known latitudinal dependence of the Be tropospheric fluxes. Overall, the study provides an improved understanding of the correlation and variability of Pb and Be concentrations in the atmosphere in the South West Coast of India.
作为建立区域天然放射性数据库的一部分，在印度西南海岸的芒格洛尔和凯加进行了为期三年半（2014 - 2017年）的铅和铍大气浓度测量。本研究分析了全年不同月份采集的总共99个空气样本。发现铍和铅的平均活度浓度分别为5.5±3.1 mBq/m和1.1±0.73 mBq/m。两种放射性核素均表现出强烈的季节变化，铍的最高浓度出现在夏季，铅的最高浓度出现在冬季。两种放射性核素的浓度在雨季最低。冬季铅浓度较高归因于东北风导致大陆气团的侵入。太阳活动的太阳黑子数指数在空气中铍浓度的增减中也起着重要作用。本研究观察到，根据11年太阳周期，铍浓度分别随着太阳活动降低和升高（太阳黑子数低和高）呈现出明显的增加和降低趋势。还研究了颗粒物浓度的时间变化，其在冬季达到最大值，在雨季达到最小值，平均值为56.9 μg/m。观察到颗粒物与铅活度浓度之间存在统计学上显著的正相关，而颗粒物与铍之间的相关性较弱。这是因为铍主要与亚微米尺寸的颗粒相关，而颗粒物由较大尺寸的颗粒构成。通过线性回归分析研究了铍和铅活度浓度与降雨、温度和湿度等气象参数的相关性。观察到铍和铅浓度与降雨强度之间存在显著相关性（相关系数相同），这表明这两种放射性核素的去除机制相似。铍与温度呈现出强相关性，而铅与湿度呈现出强相关性。将本研究在印度西南海岸获得的数据与全球气溶胶中铍和铅的文献值进行比较，结果表明这些值并未反映出铍对流层通量众所周知的纬度依赖性。总体而言，该研究有助于更好地理解印度西南海岸大气中铅和铍浓度的相关性及变异性。
