Biogeochemical activity in arsenic prone zone-Juniper Publishers

Juniper Publishers- Open Access Journal of Environmental Sciences & Natural Resources

 

Biogeochemical Activity in Arsenic Prone Zone

Authored by Pinaki Ghosh

Abstract

The world’s largest arsenic (As) mass poisoning have been reported from west Bengal, India in early eight. Arsenic as a Heavy metals are the natural constituents of the earth crust. The level of As have been found to be particular alarmining in India, Bangladesh, China, Taiwan, United state and many other countries. The health risks of As exposure due to the installation of thousand of shallow tube wells in BDP is known, however, microbial contamination of shallow aquifer is another important issue that can be linked with As mobilization and water quality. Different types of Bacteria influence as geochemistry by their metabolic pathway including Oxidation, reduction, and mobilization reaction that highly regulated as speciation in our environment. This further study the microbiological (bacteria, fungus & higher plant) population of ground waters with references various psycho-chemical parameters of water particularly arsenic (As) concentration.

Keywords: Arsenic; Microbiology; Geochemistry; Oxidation

Introduction

Arsenic contamination in ground water is a critical issue of west Bengal in India and Bangladesh. Over the few decades, geogenic arsenic was highlighted in many regions of the world [1-4]. The most notable in south & Southeast Asia where 60 million people are affected this chronic arsenic poisoning [2]. Anthropogenic activities (fertilizer, arsenical pesticides, wooden poles preservative agents, mining waste, waste sewage sludge, and coal burning) and well drilling mobilize arsenic in to the environment [2,4,5]. Several biogeochemical process are involved (i.e. chemical & redox change and bacterial Fe (III) reduction) these Bengal delta plain (BDP). This sub surface arsenic contamination ground water are not stay in the ground, it will be affected human food chain (Rice, vegetables, etc) also human tissues. This endemic problem is most important / challenge to us [3,4].

Biogeochemical Process

Many researchers studied the microbiologically point of view that iron reducing bacteria occur arsenic mobilization [1]. Microbial reduction of Fe (III) system are degraded the organic carbon, these microbial decoupling reaction involved As (V) to converts As (III) which more toxic then As(V) [1]. Many fecal coli form bacteria also involved this decoupling reaction [6]. Some different class fungi are capable of removing toxic arsenic compound from arsenic polluted environments. Most fungus store arsenic inside the cell cytosol with a metal binding polypeptides e.g. metallothioneins or phytochelatins also called cell vacuoles. Fungus group microorganism accumulates the arsenic at the stationary growth phase [7].

i. Depth dependent arsenic mechanism

World largest Bengal delta plain (BDP) soil character is alluvium, also flood porn zone. This delta plain physic chemical parameter is more pragmatic relation of arsenic mobilization. Many chemical parameters such as pH, Eh, Na⁺, Ca⁺, Mg⁺, Fe _T, Fe (II) also temperature are more positive co-relation found with arsenic [2-4].

ii. Oxidation and reduction process

The oxidation model, arsenic are released to sulphide minerals bellow the reaction [8].

FeS₂ (S) + 7/2 O₂ +H₂O ↔ Fe²⁺ + 2SO₄²- +2H⁺

FeAsS (S) + 13Fe³+ + 8H₂O ↔ 14 Fe²+ + SO₄²- + 13H+ + H₃AsO₄

The reduction model of arsenic also called reverse approach of the oxidation model where co-precipitated with Fe/ Mn/-oxide/ Hydroxide, bellows the reaction [8].

4FeOOH + CH₂O- PO₄ (sorbed) +7H⁺ → 4Fe²+ + PO₄³- (desorbed) +6H2O

2H₂AsO₄- + CH₂O +5H+ → 2H₃AsO₄ +HCO³- +2H₂O

Future Scope

From the study it can be stated that the arsenic contamination has spreaded throughout the world and there is an urgency to fight against it. Our hypothesis that Microbiologically (Living organism) which converted high toxic or carcinogen arsenite [As (III)] to arsenate [As (V)]. Also some useable technique that can be analysis between arsenic microbes (bacteria, fungus & higher plant) interaction, and physiological properties of subsurface and surface biodiversity.

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