: To estimate the magnitude of quality of Asan River water in Dehradun district, Uttrakhand, India, during post-monsoon season. This study explains the post-monsoon seasonal variation of Asan River water quality with physical and chemical parameters, which identified the potential of pollution sources with similar characteristics. Sixteen Physicochemical parameters such as temperature, turbidity, pH, TDS, EC, BOD, COD, DO, TSS, Total Hardness (Calcium and Magnesium), Sodium, Potassium, nitrate and Alkalinity were performed in post-monsoon season to evaluate the concentration of pollution level in samples that were collected from five different locations of the same river by using experimental and statistical methods. Analytic results showed that all parameters in the water quality index were within the permissible limit parameters like Alkalinity, total hardness; sodium, COD, TDS, and TSS were measured to be higher than the required standards suggested by different agencies such as WHO and ISI during post-monsoon seasons. Analysis enlightens the seasonal changes in Asan River water quality, which always indicates that the pollution is caused by rainfall or other sources of human interference. However, the values of various physicochemical properties vary with seasons. To work on environmental monitoring and waste treatment to protect the population from health risks seems essential.

This study focuses on the persistent need for safe drinking water by conducting a seasonal assessment of the Asan River, a tributary of the Yamuna River in Dehradun, Uttarakhand, India. During the monsoon season (July-August) of 2024, five water samples were collected from various locations along a 40 km stretch of the Asan River. The research evaluated thirty physico-chemical and biological parameters, including temperature, pH, electrical conductivity (EC), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), turbidity, and ion concentrations, along with bacterial counts. The study shows the negative correlation coefficient of -0.811 between temperature and biochemical oxygen demand (BOD), suggesting that as temperature increases, BOD tends to decrease. The findings demonstrate the relations between pH and major water quality indicators. The findings emphasize the urgent need for continuous monitoring and effective management of river ecosystems to ensure water quality and public health protection amidst increasing pollution challenges.

Coronavirus disease (COVID-19) was first detected in Wuhan, China in December 2019. The characteristics of the spread of COVID-19 infection from one person to another have led to an increasing number of infected cases and caused tremendous pressure around the world. The rapid spread of COVID-19 infection has made it a pandemic. In India, as of mid-May 2020, there were approximately 75,048 confirmed cases and 2,440 deaths due to COVID-19 alone. In order to break the COVID-19 chain, the Indian government decided to implement a lockdown, which was first implemented on March 23, 2020. The significant benefits of the lockdown have led to a reduction in air pollutants in cities around the world. The significant benefits of the lockdown have led to a reduction in air pollutants in cities around the world. The importance of particulate matter, temperature (°C) and relative humidity (%) to the spread of the COVID-19 virus and its correlation with the total number of cases (TC), active cases (AC), recovered cases (RC) and death cases (DC) Reference DEL will be discussed in detail in this chapter.