Anindita Mitra

Phytoremediation Protocols: An Overview

Phytoremediation is a developed technology which exploits naturally occurring uptake capabilities of plant root system, together with the translocation, bioaccumulation, or detoxifying abilities to clean up the surrounding environments. Several strategies used by plants for dealing with xenobiotics include phytostabilization, phytoextraction, phytovolatilization, rhizofiltration, phytodegradation, and phytostimulation. Phytoextraction involves the cultivation of hyperaccumulating plant varieties that concentrate or translocate soil contaminants in their harvestable shoot, whereas phytostabilization aims to immobilize the contaminants within rhizosphere, thus preventing their escape into the trophic level. Uptake and transpiration of heavy metals into a less toxic form is the basis of phytostabilization. In rhizofiltration technology, aquatic plants are used to absorb, concentrate, and remove hazardous compounds from aqueous environment by their root system. Various soil and plant factors such as soil’s physical and chemical properties, plant and microbial exudates, mobility and bioavailability of metals, plants ability to uptake, translocate, sequester, and detoxify metal account for phytoremediation efficiency. Transgenics are becoming new promising tools to enhance phytoremediation potential. This chapter overviews different methods and approaches in phytoremediation strategy.

Use of Wetland Plants in Bioaccumulation of Heavy Metals

Heavy metal pollution due to anthropogenic activities like mining, smelting, untreated waste disposal and dumping, and pesticides and fertilizers application is becoming a major global concern. Once released into the environment, heavy metals find their way into aquatic systems contaminating water bodies and its associated life forms. Wetlands are most vulnerable in this process as they are usually low lands in comparison to the surroundings. Conventional methods of mitigating metal contamination in soils and water like extraction, immobilization, and toxicity reduction, physical barrier, chemical stabilization, electro kinetic processes, soil washing, and pump-and-treat systems are prohibitively expensive, energy intensive, and can reduce the fertility and bioactivity of soils. Natural wetland systems along with its native flora have the capacity to improve water quality by filtering pollutants from water that flows through on its way to receiving water bodies. Many of the wetland plants have the capability to mobilize and uptake the metals at rhizosphere, where microbial association and symbiosis play an important role in the accumulation of metals. This chapter tried to encompass the role of wetland plants and their selection related to natural restoration of contaminated sites through economic, aesthetically pleasing phytoremediation technology.

Modulation of Immune Response by Organophosphate Pesticides: Mammals as Potential Model

Abstract Organophosphates (OPs) are most widely used pesticides and primarily induce toxicity by inhibition of acetylcholinesterase (AChE) in the nerve terminals of central and peripheral nervous system, leading to a variety of short-term and chronic effects in the non-target animals. In addition to acetylcholinesterase, OPs are known to potent inhibitors of serine hydrolases which are vital component of the immune system and therefore influence the immune functions. OPs induce several immunomodulatory effects in vertebrates by altering neutrophil function, macrophage production, antibody production, immunosuppression, reduced interleukin production and T cell proliferation. Immunotoxicity due to OP exposure is mediated through perturbation of the cholinergic response of lymphocytes, altering signal transduction, mutilating granule exocytosis pathway and impairing FasL/Fas pathway of natural killer cell and other immune related cells. Apoptosis of lymphocytes or immune related cells is promoted through mitochondrial pore formation and DNA fragmentation. In this review an attempt has been made to document the immunomodulatory effects of organophosphate pesticides using mammals as potential model with an additional information on the probable mechanism of immunotoxicity induced by OPs.

Uptake, Transport, and Remediation of Arsenic by Algae and Higher Plants

Arsenic (As) pollution is a significant environmental problem. In nature, As exists as inorganic or organic species but is normally not encountered in its elemental state. As is a nonessential metalloid and does not play any biological role in algae, plants and causes toxic response after gaining entry into the cell. Upon translocation to the shoots As can severely impede growth of the plants by slowing or arresting accumulation of biomass, as well as induce loss of fertility, yield, and fruit production. Several reports are there indicating that an elevated concentration of As in soil causes a significant reduction in crop yield. Algae and plants have developed a range of strategies to combat As toxicity including chelation and sub-sequestration of complexes in vacuole. As contamination in human occurs through consumption of cereals, vegetables, and fruits irrigated with As-contaminated water. The consequence is a global epidemic of As poisoning, leading to skin lesion, cancer of bladder, lung, and kidney and other symptoms. Remediation of As-contaminated soil and groundwater, therefore, is an urgent need for providing safe drinking water and food. Among the various bioremediation processes, phytoremediation by algae and plants is quite effective. Phytoremediation strategy involves suitable plants including arsenic hyperaccumulating ferns and some aquatic or terrestrial angiosperms that efficiently remove the metalloid from highly contaminated soil/water. Utilization of transgenic plants is becoming a new promising tool to enhance phytoremediation potential. There is an urgency to have extensive knowledge on arsenic uptake, transport, metabolism, and detoxification in algae as well as plants for improving phytoremediation. The objective of this review is, therefore, to provide an overview about the uptake of the inorganic and organic species of arsenic, their translocation and biochemical fate in algae and plants and to explore the current concepts of phytoremediation along with their limitations and challenges associated with the developed processes.

Potential Role of Microbes in Bioremediation of Arsenic

Arsenic (As) is an extremely toxic metalloid that naturally occurs in the environment from geochemical weathering of rocks, volcanic emission, and anthropogenic activities. The detrimental effects of arsenicals on humans is an increasing menace chiefly due to contaminated drinking water and foods as the levels of As have been elevated in soil and groundwater across the globe. Remediation of arsenic-contaminated soil and groundwater therefore, is an urgent need for providing safe drinking water and food. Bioremediation became an emerging alternative to conventional energy intensive, instrument and chemical based expensive restoration technologies of heavy metal or metalloid contaminated areas of land and water. Bioremediation by microbes (bacteria, fungi, yeast) are quite effective and relies on deliberate action of natural or engineered microbial activity to reduce, mobilize, or immobilize, volatilize As through sorption, bio-methylation, complexation and redox reactions.