Tracing phosphorous distributions in the surficial sediments of two eastern Himalayan high altitude lakes through sequential extraction, multivariate and HYSPLIT back trajectory analyses

Phosphorous (P) fractionation of the surficial sediment of high altitude lakes (HAL) i.e. P.T.Tso and Sella lakes of Arunachal Pradesh State, India were studied with an objective to investigate the phosphorus availability in the environment, nutrient status of the lake and the role of climate change. Moreover, the variation in phosphorous fraction was investigated through mineralogical studies like grain size analysis and X-ray diffraction. The findings revealed that the surficial sediment of lakes are least influenced by anthropogenic sources, since a slight increase in each of the P-Fractions was observed from year 2011 to 2012, except organic P. Loosely sorbed exchangeable phosphorous was found to be slightly high which was due to difference in atmospheric precipitation, which is one of the strong factors in high altitude regions. Decrease in organic fraction of P indicated that lakes became more oligotrophic in nature. Mineralogical investigation shows that illite-montmorillonite and montmorillonite are the main minerals in Sella Lake, whereas montmorillonite and graphite are main minerals in P.T.Tso lake. Factor analysis of seasonal data of P fractionation in surface sediments, along with physical parameters of Sella Lake water indicates three factors for the 2011 data principle factors are pH, EC, oxide-bound and organic P. Factor analysis of P.T.Tso lake water indicates three factors for the 2011 data with principle factors are adsorbed P and authigenic P, pH, oxide-bound P. This study shows that except organic fractions all other fractions are increasing in the following year. It implies that even at such remote high altitude locations P characteristics are changing year to year which sought for further investigation and enables HALs to show the early impacts of climate change related changes. A clear influence of long range transported air pollutants has been found through HYSPLIT back trajectory models which needs to be substantiated through long-term monitoring.