Red Panda feces from Eastern Himalaya as a modern analogue for palaeodietary and palaeoecological analyses.

Modern feces samples of the endangered red panda (Ailurus fulgens) were examined using multiproxy analysis to characterize the dietary patterns in their natural habitat in India. An abundance of Bambusoideae phytoliths and leaves (macrobotanical remains) provide direct evidence of their primary dietary plants. In contrast, Bambusoideae pollen is sporadic or absent in the pollen assemblages. An abundance of Lepisorus spores and its leaves along with broadleaved taxa, Betula, Engelhardtia, and Quercus are indicative of other important food sources. Average δ13C values (- 29.6‰) of the red panda feces indicate typical C3 type of plants as the primary food source, while the, δ15N values vary in narrow range (3.3-5.1‰) but conspicuously reveal a seasonal difference in values most likely due to differing metabolic activities in summer and winter. The multiproxy data can provide a baseline for the reconstruction of the palaeodietary and palaeoecology of extinct herbivores at both regional and global scales.

Chemical and isotopic characteristics of PM2.5 over New Delhi from September 2014 to May 2015: Evidences for synergy between air-pollution and meteorological changes.

The capital city of India, New Delhi, is experiencing serious PM2.5 pollution in the form of recurrent hazy skies and smoky fog (SMOG) episodes in recent years. Besides source-emission strengths, frequency and time-spans of these air-pollution episodes are uncertain due to variable urban meteorological influences, preventing the formation of a cohesive policy to tackle air-quality degradation. About 70% mass of PM2.5 particle is composed of Carbon (C), Nitrogen (N), and Sulphur (S) and, hence, their mass concentrations along with their stable isotopic imprints (viz. δ13CPM2.5, δ15NPM2.5 and δ34SPM2.5) provide powerful tools to gain insights into complex aerosol chemistry. This study presents the aforementioned data generated for PM2.5 collected from New Delhi covering full post-monsoon, winter, and summer months of 2014-15. Temporal variability in the generated dataset was analyzed with variabilities in atmospheric concentrations of key gaseous species (NH3, NOx, and SO2) and meteorological indices. The highest PM2.5 concentrations were observed in winter months with enhanced aerosol N and S concentrations. Active biomass (crop-residue) burning in the northwest Indo-Gangetic Plains (IGP) appears to be the major source of aerosol TC for post-monsoon and winter months in addition to emission sources from the combustion of bio- and fossil- fuels. Aerosol TN contents appear to be largely impacted by ambient ammonia emissions, especially during winter. Aerosol TS contents could be manifested by emissions from coal combustion, road dust, and biogenic sulphur. Total C + N + S contents of PM2.5 showed significant negative correlations with surface solar radiation and air-visibility. Both δ15NPM2.5 and δ34SPM2.5 values show remarkable correlations with air-quality and meteorological parameters during winter months demonstrating considerable secondary cycling. Cluster analysis and concentrated weighted wind trajectories over New Delhi for the study-period showed ~64% and ~58% of air mass trajectories from the northwest (Punjab-Haryana) region during post-monsoon and winter months respectively.

Chemical and isotopic characteristics of PM10 over the Bay of Bengal: Effects of continental outflow on a marine environment.

Pollutants transport from South and Southeast Asia can profoundly affect the marine atmospheric boundary layer (MABL) over the Bay of Bengal (BoB). This study presents chemical and stable isotopic composition of PM10 collected at Port Blair Island (11.6°N, 92.7°E) located in the middle of the BoB during the late northeast monsoon (February-April), a period when the BoB receives considerable continental outflow. These samples (n = 50) were analysed for major ions, carbonaceous species, trace metals, and isotopic composition of total C, N, and S components. Mass concentration of PM10 ranged from 24 to 65 µg m-3 during the study period. The dominance of continental inputs over a marine realm was evident by a significant amount of non-sea-salt (nss)-SO42- (range: 1.8 to 16.9 µg m-3), which accounts for ~65% of the total water-soluble inorganic constituents. The impact of anthropogenic emissions was further evident from the widespread depletion of chloride (range: 57-100%, avg.: 98 ± 7%) from sea-salt aerosols. Carbonaceous species (elemental carbon and organic matter) contributed nearly 35% to PM10. Further, average δ13C (-25.6‰ ± 0.5) and δ34S (4.5‰ ± 1.3) values observed over the marine study region were similar to those found in typical urban environments. δ15N values (13.7‰ ± 5.1) show the significant presence of combustion sources along with the effect of atmospheric processing. Aerosol δ13C values correlate positively with the ratio of water-soluble organic carbon to total organic carbon, indicating the aging of organic aerosols during the transport. Chemical and isotopic data suggest that both biomass burning (BB) and fossil fuel burning (FFB) contributed to ambient PM10 with relatively more contribution of BB during February to early March and that of FFB during late March to middle of April. In aggregate, this study provides newer insights into sources of carbonaceous species and their chemical processing in MABL of BoB.

Radiocarbon measurements using new automated graphite preparation laboratory coupled with stable isotope mass-spectrometry at Birbal Sahni Institute of Palaeosciences, Lucknow (India).

Conventional beta counting technique based radiocarbon dating facility at Birbal Sahni Institute of Palaeosciences- Lucknow was established in 1974 (Rajagopalan,1978). In 2017-18, BSIP received an upgrade with installation of an Automated Graphitization Equipment (AGE) coupled with an Elemental Analyser, a Carbonate Handling System (CHS) along with an in-line stable isotope mass-spectrometer (IRMS). Using this combo, stable Carbon (C), Nitrogen (N) and Sulfur (S) isotopic measurements could be carried out in both organic and inorganic type samples followed by graphite preparation (~1 mg) for 14C measurement by Accelerator Mass Spectrometry (AMS). This communication addresses details of pre-processing, processing, and quality checks adopted for achieving acceptable and demonstrable accuracy and precision of measured Δ14C, δ13C, δ15N, and δ34S measurements. Information regarding chemical preparation of samples for aforesaid stable and radio isotopic analysis is provided in succinct manner. Overall, average coefficient of variation determining precision of our graphite powders for 14C measurements is ~2.4%. The mean age of blank (anthracite) processed using established EA-IRMS-AGE unit comes as 42,100 ± 300 years.

8000-year monsoonal record from Himalaya revealing reinforcement of tropical and global climate systems since mid-Holocene.

We provide the first continuous Indian Summer Monsoon (ISM) climate record for the higher Himalayas (Kedarnath, India) by analyzing a 14C-dated peat sequence covering the last ~8000 years, with ~50 years temporal resolution. The ISM variability inferred using various proxies reveal striking similarity with the Greenland ice core (GISP2) temperature record and rapid denitrification changes recorded in the sediments off Peru. The Kedarnath record provides compelling evidence for a reorganization of the global climate system taking place at ~5.5 ka BP possibly after sea level stabilization and the advent of inter-annual climate variability governed by the modern ENSO phenomenon. The ISM record also captures warm-wet and cold-dry conditions during the Medieval Climate Anomaly and Little Ice Age, respectively.

Altered cropping pattern and cultural continuation with declined prosperity following abrupt and extreme arid event at ~4,200 yrs BP: Evidence from an Indus archaeological site Khirsara, Gujarat, western India.

Archaeological sites hold important clues to complex climate-human relationships of the past. Human settlements in the peripheral zone of Indus culture (Gujarat, western India) are of considerable importance in the assessment of past monsoon-human-subsistence-culture relationships and their survival thresholds against climatic stress exerted by abrupt changes. During the mature phase of Harappan culture between ~4,600-3,900yrsBP, the ~4,100±100yrsBP time slice is widely recognized as one of the major, abrupt arid-events imprinted innumerous well-dated palaeo records. However, the veracity of this dry event has not been established from any archaeological site representing the Indus (Harappan) culture, and issues concerning timing, changes in subsistence pattern, and the likely causes of eventual abandonment (collapse) continue to be debated. Here we show a significant change in crop-pattern (from barley-wheat based agriculture to 'drought-resistant' millet-based crops) at ~4,200 yrs BP, based on abundant macrobotanical remains and C isotopes of soil organic matter (δ13CSOM) in an archaeological site at Khirsara, in the Gujarat state of western India. The crop-change appears to be intentional and was likely used as an adaptation measure in response to deteriorated monsoonal conditions. The ceramic and architectural remains of the site indicate that habitation survived and continued after the ~4,200yrsBP dry climatic phase, but with declined economic prosperity. Switching to millet-based crops initially helped inhabitants to avoid immediate collapse due to climatic stresses, but continued aridity and altered cropping pattern led to a decline in prosperity levels of inhabitants and eventual abandonment of the site at the end of the mature Harappan phase.

Variations in some environmental characteristics including C and N stable isotopic composition of suspended organic matter in the Mandovi estuary.

Chemical and isotopic (δ13C and δ15N) investigation of the Mandovi estuary along the Indian west coast affected strongly by the seasonal monsoon cycle was carried out. The Mandovi estuary is a major waterway for Goa and extensively used for transportation of iron and manganese ore. In addition, with large population centers as well as agricultural fields located on its shores, the estuary is assumed to have been influenced by human activities. Measurements of chemical and isotopic parameters made in the lower part of the estuary during the southwest (SW) monsoon and post-monsoon seasons reveal distinct changes, and it is observed that despite considerable enrichment of macronutrients during the SW monsoon, productivity of the estuary (phytoplankton biomass), as inferred from the chlorophyll-a content, is not as high as expected. This is due to occurrences of high turbidity and cloud cover that limits photosynthetic productivity. The isotopic characterization (C and N isotopes) of suspended organic matter produced/transported during the monsoon and post-monsoon seasons of year 2007 provides a baseline dataset for future isotopic studies in such type of tropical estuaries.