The cause of continuous precipitation acidity change is complex. Except for the impact of local acid pollutant emissions, when the wind speed is relatively large, long-distance pollution air masses should be considered for long-distance transportation. The effects of near-surface air humidity and other meteorological factors cannot be ignored. The distance between the west area and the N direction and SSE positional industrial groups is about 50 kilometers, and the straight distance from the NNE direction industrial group is about 60 kilometers. If the friction coefficient is not considered due to the roughness of the underlying surface, the average wind speed is greater than 0.6 m/s respectively. With 0.8m/s, acidic contaminants will affect the measurement point. The average daily wind speed is between 0 and 0.2m/s. It is believed that the change of acidity is mainly caused by the discharge of local acid pollutants; 0.3～0.5m/s, and the change of acidity is considered to be caused by the combined effect of local acidic pollutant discharge and long-range acidic pollution air mass transport. . The determination of wind direction and wind speed may rely on wind speed and direction recorders, or wind direction wind speed monitors.
The analysis of the change in continuous precipitation acidity, in addition to the wind speed on the day, should also focus on the wind speed of the previous day, especially when there is a large industrial pollution group on the upwind, such as when the wind speed is large and the wind direction does not point to the observation point on the previous day. The degree of influence will be relatively weakened. We will now focus on the analysis of typical continuous precipitation with pH rising or falling above 0.6. In 32 continuous precipitations, there are 13 occurrences in this range, accounting for 41%. 3.3.1 Enhancement of acidity Typical analysis of continuous precipitation Contrast between the two days before and after, the maximum value of acidity enhancement appeared on September 27, 2005, the pH value decreased by 1.49, the precipitation continued for 3 days, the dominant wind direction continued to be ENE, and the second day The wind speed is as high as 3.2 m/s, which is conducive to the long-distance transportation of polluted air mass. The wind speed decreases slightly on the third day. With the high humidity in the near-field, acidic pollutants are more likely to react with the polluted air mass, leading to a significant increase in acidity. The next largest value appeared on May 29, 2006. The pH value decreased by 1.10. The precipitation lasted for 4 days. The precipitation on the first and second days was large, totaling 175.2 mm. It had strong scrubbing effect on the local near-ground air. If there is no supplemental supply of external acidic pollutants, the acidity of precipitation should be weakened on the third day, but the continuous two days of heavy rain make the air humidity up to 94%, plus a wind speed of 1.4m/s, and quickly send the air pollution of S direction to and The chemical reaction with the near-surface temperature-humidity air mass resulted in an increase in acidity. The wind direction changed to WSW on the 4th day. The azimuth of the azimuth was less developed in the industry, the transport of acidic pollutants was reduced, and the acidity of precipitation decreased.
Summary: The winds with higher wind speeds of E to SE, S, and SW, especially typhoons, bring about the formation of near-surface air masses that are cleaner on the ocean surface, which will reduce the acidity of precipitation. The SSE azimuth wind with smaller wind speed transports the wind upstream to the industrial pollution air mass; the ENE azimuth wind with high wind speed transports the wind upstream to the industrial pollution air mass and chemically reacts with the near-surface air mass with high humidity along the road. Acidic pollutants are enriched, gradually increasing the acidity of precipitation. From the analysis of the continuous precipitation acidity change, we can see that the wind speed is small, especially when dealing with the static wind frequency, the humid near-surface air is easy to react with the acidic pollutants twice; the wind speed is relatively high, especially from the industrial group which is full of acidic pollutant air masses to supplement the impact. Will increase precipitation acidity. To this end, to mitigate the harm caused by acid rain, the government must strengthen regional cooperation to reduce acid pollution while also destroying the conditions for the formation of acid rain.
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