Long-range transportation of air pollutants from Europe to Israel

In order to characterize long-range transported (LRT) air masses that reach Israel from Europe, a monitoring site was set up on the Israeli Mediterranean coast. The site allowed the sampling of air parcels crossing the Israeli western coastline and the separation into LRT and locally polluted air masses. The measurements performed included the continuous monitoring of the primary pollutants SO₂, NO, and CO and the secondary pollutants NO_y-NO, O₃, sulfate, and nitrate. Differential optical absorption spectrographic (DOAS) measurements of SO₂, NO₂, and O₃ were performed simultaneously on four-kilometer-wide air parcels reaching the monitoring site. Wind direction and wind speed data were measured concurrently with the pollution monitoring. Research campaigns were performed during May through September for three consecutive years, 1993, 1994, 1995. The results from the continuous monitoring showed that for most of the time the primary pollutant levels in the LRT air masses were less than 0.5 ppbv for SO₂ and NO and below 0.3 ppmv for CO. Conversely, the secondary pollutants showed relatively higher concentrations, with NO_y levels varying between 1 and 4 ppbv and ozone levels between 40-60 ppbv. The DOAS measurement results for the air masses show results similar to those obtained from continuous point measurements. Particulate sulfate levels were consistently high, with values almost always above 100 nmoles m^-3, with peak levels double that value. The nitrate concentrations were in the 50 to 100 nmoles m^-3 range, although occasionally levels of around 200 nmoles m^-3 were measured. These levels are as high as measured at any location in Europe or America. The sulfate/total sulfur ratio values were always above 0.7, while the nitrate to NO_y ratios were lower, ranging between 0.8 and 0.4. Based on the formation and deposition rate for sulfate, this suggests that the air masses are at least 3 to 4 days old and must have traveled thousands of kilometers before reaching the Israeli coast. The study clearly indicates that the eastern edge of the Mediterranean Sea, especially Israel, is strongly affected by long-range transported polluted air masses that originated over Europe.