In 1996, New Hampshire discontinued lead (Pb) monitoring because air quality levels were well below the NAAQS and at the lowest levels of method detection. Nitrogen dioxide (NO2) monitoring was performed at two sites in 1997. The site in Manchester measured the maximum NO2 annual average of 16 ppb or 32% of the NAAQS. There have been no significant trends for NO2 in the last 10 years.
Three of the twelve ozone (O3) sites operating in New Hampshire reported violations of the NAAQS in 1997. The Rye Harbor Site reported the highest daily maximum value of 0.156 ppm or 130% of the standard. Last year none of the sites reported violations of the ozone NAAQS and in 1995 only the Rye Harbor site reported violations of the NAAQS.
None of the thirteen particulate matter (PM10) (with a mass mean diameter of less than 10 microns) sites in New Hampshire had any violations of the annual or 24-hour NAAQS in 1997. Berlin-Lancaster reported the highest 24-hour values and the highest second maximum value of 81 µg/m3 or 54% of the daily standard. Berlin-Lancaster reported the maximum annual average concentration of 37 µg/m3 or 56% of the NAAQS. Over the past five years, all PM10 monitoring sites have recorded particulate matter concentrations well below the annual and 24-hour NAAQS. Yearly variability in the data is common. Factors contributing to variability are in part determined by meteorology, transport of particulate matter from distant sources, and changes in the emission strength of local sources. The ten-year trend graph shows downward trends for PM10 in Manchester, Portsmouth and Berlin.
There were no violations reported at any of the eleven sulfur dioxide (SO2) sites in 1997. The highest annual arithmetic mean was reported in Manchester at 8 ppb or 27% of the NAAQS. Pembroke reported the highest 24-hour second maximum of 53 pb or 38% of the standard, as well as, the highest 3-hour second maximum of 130 ppb or 26% of the NAAQS. Since 1990, the SO2 ten-year data have shown no significant trends.