14. starptautiskā konference 2012 - Latvijas Jūras akadēmija

200020012002200320042005200620072008200920102011Proceedings of 14th International conference „Maritime Transport and Infrastructure - 2012”Annual average benzene concentrations on Tvaika Street at Riga Harbour is decreasing after2002, when handling of light oil products was stopped, and is increasing from 2006, when theirhandling returned (Figure 3). After regulations on air pollution in Latvia [6] annual limit value forbenzene from 2010 is 5 mg/m 3 , and it was again exceeded in 2011 (7.1 mg/m 3 ). The companies in RigaHarbour is ordering the monitoring of air pollution in their territories from State Ltd LEGMA, and in2011 benzene concentrations in the territory of “ManTess” was measured 9 months with diffusionsampler technique. Average concentration was only 3.7 mg/m 3 , which is about 2 times less thanmeasured with DOAS station. The diffuse sampler method is monitoring air pollution only in onepoint; nevertheless an open-beam DOAS system captures air pollution from a much wider area.Concentration, mg/m 320181614121086420Annual average benzene concentrationsFig. 3. Annual average benzene concentrations on Tvaika Street at Riga Harbour (red line - annual limitvalue for benzene).Therefore it is possible that with DOAS technique are measured benzene emissions frommany different sources: rail cars, tankers, handling operations in the terminals, trucks and passengercars, buses.4.2 Concentrations of Sulphur Dioxide SO 2Analyzing SO 2 concentration distribution depending on wind directions (Figure 4), it isnoticeable that the higher SO 2 pollution is coming from certain directions. Comparing the position oflight beam and surrounding emission sources, it is expected Ltd BMGS is responsible for SO 2pollution from North, tankers – for pollution from West-Northwest, stacks of Ltd ManTess – forpollution from East.Sometimes pollution cases are observed in Riga in specific weather conditions (temperatureinversion, low wind speed) when simultaneously all 7 urban air monitoring stations are recording thegrowth of SO 2 concentrations (Figure 5). In the particular case (January 31, 2009, 3:00-5:00 AM) thetemperature was -8 o C, the wind blew from the North (31 degrees) with speed 3,2 m/s. A possiblesource of pollution could be a Riga Harbour.72