3.4 Seasonal variation in pollution

The concentration of pollutants in Myanmar’s dry season is higher than in the rainy season. This is because in the rainy season storm water dilutes pollutants and this alleviates the pollution impact in the rivers. The pollution impact of industrial wastewater and domestic wastewater from river basins will be bigger when the water flow is lower, making it difficult to maintain the desired water quality in surface water in the dry season.

To understand if contamination is a problem in an aquifer or river you need to know both the type of contaminant and the amount. Amounts of contaminants are measured in terms of their concentration using the concepts of ppm and ppb, which are parts per million and parts per billion.

• PPM is the amount of contaminant units in 1,000,000 (1 million) units of groundwater.
• PPB is the amount of contaminant units in 1,000,000,000 (1 billion) units of groundwater.

Different kinds of contaminants need to be present at different concentrations before they start to harm the environment or us.