Annual and decadal variation in chemical composition of rain water at all the ten GAW stations in India

Abstract

Spatial variation of long term annual precipitation volume weighted concentrations of major chemical constituents , NO 3 − , Cl − , NH 4 + , Ca +2 , Mg +2 , Na + and K + ) at all the ten Global Atmospheric Watch (GAW) stations in India for the period from 1981 to 2012 is studied in this paper. Ionic abundance and balance is studied as well. The range of long term annual mean pH at ten stations was 5.25 ± 0.82 to 6.91 ± 0.76, lowest at Mohanbari and highest at Jodhpur. The long term annual mean pH for the period 1981-2012 showed decreasing trend at all the stations (significant at 5 % level). Decadal mean pH among ten stations for 1981-1990, 1991-2000 and 2001-2012 ranged between 7.31 to 5.76, 7.45 to 4.92 and 6.16 to 4.77 respectively and showed decreasing trend at all the stations during 1981-1990 to 2001-12. The percentage occurrence of acidic pH (<5.65) at ten stations ranged from 3 to 72 %, lowest at Jodhpur and highest at Mohanbari and it increased from 1981-1990 to 2001-2012 almost at all the stations. Temporal variation of annual mean values of nssSO 4 −2 , NO 3 −, Ca +2 and pH for the study period were attempted. Variation of nss K (non sea salt Potassium) at all the stations was studied to assess the biomass burning contribution in different regions. Non-marine (terrestrial) contribution dominated for majority of ionic constituents at most of the stations. However marine contribution was found to be dominant for Mg at Port Blair and Minicoy. Also sea salt fraction of SO 4 was higher than terrestrial at Minicoy. Sources of measured ionic constituents in rain water are assessed through correlation analysis. The concentrations of all the ionic species were lowest at Kodaikanal, a high altitude hill top station and the total ionic mass was 136.0 μeq/l. Jodhpur, an arid station not only had highest concentrations of Ca +2 , SO 4 −2 and K + but also had highest total ionic content1051.8 μeq/l) among all the stations. At Srinagar, Jodhpur, Allahabad, Nagpur and Pune stations Ca +2 was the dominant cation while dominant anion was NO 3 − for Srinagar, Allahabad, and Nagpur and Cl − for Jodhpur and Pune; at Mohanbari NO 3 − and Ca +2 ; at Visakhapatnam, Port Blair and Minicoy Na + and Cl − were abundant. Temporal variation had shown an increasing trend for nssSO 4 −2 and NO 3 − and obviously decreasing trend for pH at all the stations. However, Ca +2 J Atmos Chem showed a decreasing trend at all the stations except at Port Blair. With the exception of Pune and Jodhpur stations, nssK showed a decreasing trend at all the stations revealing decreasing influence of soil/biomass burning over Indian GAW stations. Negative correlation of pH with SO 4 −2 was found to be weak compared to NO 3 -.

Global and regional trends of atmospheric sulfur

“…The original data can be accessed from the given web pages.Acronym and referencesNetworkRegionCAPMoN 31,51 Canadian Air and Precipitation Monitoring Network Including the New Brunswick Precipitation Network (NBPN), https://open.canada.ca/en/open-dataCanadaCASTNET 7,51 Clean Air Status and Trends Network, https://www.epa.gov/castnetUSEANET 31,51 Acid Deposition Network in East Asia, http://www.eanet.asia/East AsiaEMEP 10,11,31,51 The European Monitoring and Evaluation Programme, http://ebas.nilu.no/EuropeINDAAF 31,51 International Network to study Deposition and Atmospheric chemistry in Africa, https://indaaf.obs-mip.fr/AfricaIMPROVE 8,38 Interagency Monitoring of Protected Visual Environments, http://vista.cira.colostate.edu/improve/USNADP 6,31 National Atmospheric Deposition Program. Including data from MAP3S-AIRMoN (Atmospheric Integrated Research Monitoring Network), https://nadp.slh.wisc.eduUSGAW - ChinaGlobal Atmosphere Watch, regional sites in ChinaChinaGAW - India 26,31 Global Atmosphere Watch, regional sites in IndiaIndiaWDCPC 31 WMO/GAW World Data Centre for Precipitation Chemistry, http://www.wdcpc.org/Global…”

“…The trends calculated by the global aerosol models have seldom been compared to trends in observations. Trend assessments have mostly been done on regional and national observations 6–8,11,26,27 , though there are also studies which combine modeled and observed trends 9,10,28–30 . Global or hemispheric assessments have on the other hand, been done for short time periods or selected years only 31–35 , or on somewhat limited dataset 36 and few models 19 .…”

Rainwater Harvesting for Drinking Water Production: A Sustainable and Cost-Effective Solution in The Netherlands?

“…According to Grömping et al [40], over 90% of atmospheric contaminants are removed by means of wet deposition. Although many ions present in rainwater are of natural origin (e.g., sodium, calcium and chloride) there also are anthropogenic contaminants like sulphate, nitrate, phosphate, ammonium, traces of iron, copper, cadmium, manganese, lead, zinc, nitrite, bromate and fluoride [41][42][43][44][45][46][47][48]. Concentrations are generally low, and in most cases below the Dutch standards for drinking water [49].…”

Response of Water Chemistry to Long-Term Human Activities in the Nested Catchments System of Subtropical Northeast India

“…The molar ratio of Na:Cl in the study area was approximately 2.0-4.0 for both seasons, results which are higher than the sea water value of 0.86. The low concentration of Cl − indicated limited atmospheric contribution, typical for this part of Northeast India [73]. It is likely that the southern slope of Meghalaya, elevated to 1300-1500 m a.s.l.…”