Mathematical modeling is a fast and effective tool for better understanding of the interaction of various systems with the environment. Therefore interest is centered around modelling. (a) Ecosystems (b) Non-linear biological and physical systems and (c) Theoretical aspects of astrophysical plasmas. Atmosphere is a medium of transport and diffusion of pollutants, and, once the pollutants are released into the air, they are at the control of atmospheric conditions. Monitoring pollutants is expensive and time consuming, but modeling is least expensive and fast. Therefore, air quality simulation models for point, non-point and multiple sources in different terrain conditions and acid rain are being developed. These have also utility in Environmental Impact Assessment studies for all types of industries. Tropical cyclones transfer various physical properties including pollutants from surface layers to upper troposphere and beyond, They can also act as scavengers of pollutants. For a better understanding of these processes, mathematical modeling of tropical cyclones is in progress. Population migration from rural areas into urban complexes lead to deterioration of air quality and noise levels and effect urban climate. To assess the impact of urbanization spatial variation of air quality in respect of ubiquitous pollutants like SO2,Nox,TSP,O3 along with meteorological parameters and noise levels are being monitored. Experiments are also being conducted to assess the efficacy of various screens particularly vegetation for mitigation of noise and improving air quality and urban climate. Also for quick estimation of noise and for the assistance of regulatory agencies, mathematical models are being developed for industrial sources and urban areas. Aerosols depending upon their size distribution, effect climate. Modeling energy consumption and studies on impact of aerosols on climate are, also in progress. Modernization has led to the use of electrical appliances our daily life causing electrical fields around us. In order to arrive at a safely criteria, experiments simulating the commonly occurring frequency levels are being conducted on the biological effects of anthropogenic electr opollution. The work on biological tissue characterisation using ultrasound is also in progress.