Long term variation in chemical composition of precipitation and wet deposition of major ions at Minicoy and Portblair : Islands in Arabian Sea and Bay of Bengal

Abstract

Lkkj & bl ’kks/k Ik= esa vjc lkxj ds feuhdkW;  rFkk caxky dh [kkM+h ds iksVZCys;j }hi ds nks LFkkuksa ds o"kZ 1981 ls 2002 rd ds 22 o"kkZsa ds jklk;fud feJ.k ds dsoy vknzZ&o"kZ.k vk¡dM+kas dk fo’ys"k.k fd;k x;k gSA fofo/k vk;fud ldsUnzh;dj.k ds chp ds lglaca/kksa dks Li"V djus dk iz;kl fd;k x;k gSA ’kjn_rq ds nkSjku gqbZ o"kkZ ds ty esa lYQsV] ukbVªsV vkSj gkbMªkstu vk;uksa dh vf/kdre lkUnzrk ikbZ xbZ gS A _rq okj oxhZdj.k ds nkSjku ekWulwu _rq esa lHkh vk;uksa ds vknZz o"kZ.k vfHkokg ds vf/kdre gksus dk irk pyk gS A nksuksa gh LFkkuksa ij vEyh; fu{ksi.k esa c<+ksrjh dh izo`fr ns[kh xbZ gS A futZu}hi ij Tokykeq[kh dh fØ;k’khyrk iksVZCys;j ds o"kkZty esa jklk;fud feJ.k dks izHkkfor djrh gS A lYQsV vk;u ¼½ dk okf"kZd vknzZ o"kZ.k feuhdkW; esa 15-6 fd-xzk- izfr gsDVs;j izfr o"kZ rFkk iksVZCys;j es 25-5 fd-xzk- izfr gsDVsvj izfr o"kZ ik;k x;k gS rFkk ukbVªsV vk;u ¼½ dh fu{ksfir ek=k feuhdkW; esa 38-0 fd-xzk- izfr gsDVs;j izfr o"kZ vkSj iksVZCys;j esa 74-6 fd-xzk- izfr gsDVs;j izfr o"kZ rd ikbZ xbZ gS A /kuk;u vk;uksa esa lksfM;e vk;u ¼Na⁺½ rFkk dSfY’k;e vk;u ¼Ca²⁺½ ds rRo vf/kd ek=k esa tek gksrs gSa ftuesa eSXusf’k;e vk;u ¼Mg²⁺½ds lkFk&lkFk iksVkf’k;e vk;u ¼K⁺½ Hkh feys gksrs gSa A 

 The data on chemical composition of wet only precipitation from two island stations Minicoy in Arabian Sea and Portblair in Bay of Bengal, representing 22 year period, 1981-2002 have been analyzed. An attempt has been made to explain the correlation between various ionic concentrations. The maximum concentrations of sulfate, nitrate and hydrogen ions in rainwater are observed during winter season. When classified by season the wet deposition flux for all the ions is greatest in the monsoon season during which precipitation is substantially high. A tendency for increase in acidic deposition is observed at both the stations. The volcanic activity at Barren island appears to influence the chemical composition of rainwater at Portblair. The annual wet deposition of SO₄^2- ranged from 15.6 kg ha^-1 yr^-1 at Minicoy to 25.5 kg ha^-1 yr^-1 at Portblair, and the corresponding amounts of NO₃^- deposited ranged from 38.0 kg ha^-1 yr^-1 at Minicoy to 74.6 kg ha^-1 yr^-1 at Portblair. Of the cations Na⁺ and Ca²⁺ are the elements deposited in largest quantities followed by Mg²⁺ and K⁺.