Abstracts in Proceedings

· Submitted at the National Symposium on Microbes and Nanotechnology for sustainable Environment (7^th February 2019 ) at Kirori Mal College, University of Delhi.

NPs soil interaction and organic matter

Yamal G.

Department of Botany, Kirori Mal College, University of Delhi

yamalgupta@gmail.com

The production of nanoparticles (NPs) and nanomaterials is increasing at a geometric pace, as NPs find use in daily commodities, industries, pharmaceuticals, agriculture, medicine etc. These engineered NPs are inevitably introduced into environment during different phases of their life cycle (from production to disposal) and have been demonstrated to be toxic to organisms of main food-chain (bacteria, algae, crustaceans, ciliates, fish, yeasts and nematodes). Although, concentration of NPs in environment cannot be measured directly, but exposure modeling strongly suggest that soil is a major sink of NPs. NPs enter soil through various pathways, such as landfills, agricultural sewage sludge. Sewage sludge has been reported to serve as a good source of plant nutrients and organic constituents. In addition, sludge has been demonstrated to cause decrease in pH, increase in salinity and heavy metal contents. Thus sewage sludge is spread on agricultural fields to improve organic fertility, neglecting the fact that it contains various contaminants, including NPs.

Metal oxide NPs such as ZnO, TiO₂, Al₂O₃, SiO₂ have been reported to be toxic to various microorganisms (Dinesh et al., 2012). NPs of Ag have been reported to significantly inhibit microbial biomass and activity. NPs behaviour in soil system is complicated by presence of solid phase and charged components such as humic acid and clay. Presence of organic matter and soil characters are the important factors that govern the toxicity of different NPs. Studies suggest that organic matter compost reduced the negative effect on soil enzyme activity for both Ag NPs and Ag ions derived from Ag acetate. Earlier, it was shown that Ag ions (supplied in form of AgNO₃) is readily immobilized in soil, but Ag NPs can act as continuous source of Ag. They also reported , that irrespective of the state of Ag i.e. in ionic or in NPs form, silver was more mobile in mineral soil than in the soil rich in organic matter. Soil properties such as mechanical structure and presence of dissolved organic matter are the factors which influence the transport of Ag NPs.

Abstract published in Scientific Proceedings of International Conference on Challenges of Climate Change And Air Pollution-Impact on Health and Economy. Organized by Maulana Azad Medical College, New Delhi, December 14-15, 2018.

AN IDEAL AVENUE TREE TO CURB AIR POLLUTION

Gupta Yamal, Dhritiman Lal and P. Pardha-Saradhi*

Department of Environmental Studies, University of Delhi, Delhi, India

Email: ppsaradhi@gmail.com

Trees are ideal air-purifiers with potential to sequester various pollutants from surroundings and generate vital biomolecules/bio-complexes/by-products. Trees are solar energy driven natural factories that breathe in carbon dioxide (the major greenhouse gas) and breathe out oxygen. Nature-invented photosynthetic factory is comprised of two distinct sections. First section possesses machinery equipped to play the most crucial task of transforming solar light energy (physical energy) into chemical energy (often referred as assimilatory power), while second section consists of machinery that uses assimilatory power to primarily bio-transform/fix CO₂ into organic skeletons (in particular sugars). Energy-rich electrons generated by light-harvesting photosynthetic machinery and/or assimilatory power are often used for sulphur and nitrogen metabolism. It is known that SO₂ forms SO₃^2- and HSO₃^1- by interacting with water. Plants possess enzymatic machinery (with components like SO₃^2--reductase) that uses light-harvesting photosynthetic machinery energized electrons to bio-transform inorganic S-ions into S^2- and S-containing organic molecules (in particular cysteine). Similarly, other important gas pollutants comprising of NOX can also dissolve (albeit weakly) in H₂O to generate NO₃^- and NO₂^-. These ionic states of N, similar to that of S can be reduced by the electrons energized by solar-energy-driven photosynthetic machinery to form NH₄⁺ and N-containing organic molecules in particular glutamine/glutamate. Besides having potential to absorb and bio-transform gaseous pollutants, the canopy of the tress possesses potential to adsorb particulate matter (like PM-2.5, PM-10). The potential of trees to adsorb particulate matter depends on the intensity of trichomes and sticky/waxy material present on the surface of leaves and undulations/groves on canopy stem. Heavy metal pollutants (such as Pb, Cd, Zn, Cu) associated with moistened particulate matter are often dissociated/released in ionic state and get absorbed into leaves and other parts. Trees have potential to chelate or bio-transform toxic state of metals into non-toxic state and store/accumulate them in wood.

Organic pollutants (which include xenobiotics) can be biodegraded by the microbes that are harboured by tree on its surface/parts. Natural/artificial rains promote translocation of the various pollutants, in particular particulate matter (with range of pollutants) into soil. The robust root system of trees harbours a wide range of microbes, fauna and flora, each playing/contributing towards some or some other ecosystem functions. Pollutants (including particulate matter, xenobitics, heavy metals) are effectively bio-transformed into useful and/or non-toxic matter in soil. In addition, fine and robust root network of trees help in effectively harvesting rain water and improve water table.

In light of above stated unique properties of trees, it is important for the researchers, planners and policy makers to choose tree species that have [A] large canopy with immense potential to (i) effectively harness solar energy to absorb & fix very high levels of CO₂ to generate organic molecules; (ii) effectively absorb gaseous pollutants like SO₂ & NOx, and bio-transform them into S- and N- containing organic compounds using the electrons energized by solar radiation harnessing photosynthetic machinery; (iii) effectively absorb, bio-transform and accumulate heavy metal pollutants in appropriate parts; and (iv) harbour microbes that have potential to bio-transform toxic organic pollutants [including xenobiotics] into non-toxic entities; and [B] the robust root system that has potential (i) efficiently harvest rain water [thus improving water table]; (ii) harbour microbes, flora and fauna that play a vital role in handling range of ecosystem services; and (iii) harbour microbes that have potential to bio-transform organic and inorganic pollutants.