Why blood in pulmonary artery is voilet but in pulmonary vein is scarlet?

The blood in the pulmonary artery is violet because it is not oxygenated, while the blood carried by the pulmonary veins is oxygenated and its color is scarlet.

Explanation:

Under normal conditions, the arteries carry oxygenated blood, giving it a dazzling red or scarlet color, while the veins carry non-oxygenated blood —called venous blood— of a purplish and dark red color.

The only exceptions are the pulmonary arteries and veins

This is why in the pulmonary arteries the blood is violet, and in the pulmonary veins the blood is scarlet.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.