urban transport vi, c.a. brebbia & l.j. sucharov (editors ... · present situation in the old...

Air pollution in Riga

J. Kleperis*, D. Danilane, I. Pruse, J. LunevaAir Protection Division of Environmental Department, Riga City Council,Latvia;Institute of Solid State Physics of University of Latvia, Latvia

Abstract

Three DOAS type stations are controlling the quality of air in Riga -the capital ofLatvia. The measurements from all three DOAS stations (two - roof-levelstations, one - street-level station) are compared. The strong correlation wasfound between data of ozone and nitrogen dioxide pollution from all threestations. It is concluded that air monitoring on roof level as well as on street levelin Riga corresponds very well to the traffic motion in the city. Nevertheless thepollution with toluene and ozone too are much higher on roof level. AIRVIRO airquality control and management system in Riga City Council is used from 1992.Information databases about traffic intensity in streets and different point andsquare pollution sources (plants, factories, heating enterprises and different typesof boilers, including private houses) are collected throughout of all Riga. The OldTown of Riga is the most popular place for tourists, crowded by businessmen andmembers of Parliament, and full of motor vehicles as well. There are intensivetraffic flows on all four sides of the Old Town, in particular the bank of theDaugava River, where heavy traffic is going to the Riga harbour. There arenumber of complaints about air quality from residents in Old Town and acid raindamaged architectural monuments - buildings from the 15 - 19 centuries. Duringthe last 10 years the number of vehicles in Riga has increased twofold. Thepresent situation in the Old Town has become critical. Different ways ofimproving the air quality in the Old Town of Riga are proposed by modelcalculations. The research tests the hypothesis that it is possible to reduce airpollution in the Old Town of Riga by mitigating the heavy traffic around the OldTown.

Urban Transport VI, C.A. Brebbia & L.J. Sucharov (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-823-6

424 Urban Transport and the Environment for the 21st Century

Introduction

Nowadays three DOAS type stations are controlling the quality of air inRiga -the capital of Latvia. Two stations belong to the State HydrometeorologicalAgency (SHMA), they are situated in Imanta and Kengarags regions of Riga andare measuring air pollution in the roof level (background stations). Third stationbelongs to Riga City Council (RCC), is movable and measures air pollution onthe street level. It is circulating around different streets of Riga and during 6 yearsof operation collected information about air quality in Riga from 6 places indifferent time periods. Air Protection Division of RCC analysed an air qualityinformation from all three DOAS stations for 1998. The strong correlation wasfound between data of ozone and nitrogen dioxide pollution from all threestations. It is concluded that air monitoring on roof level as well as on street levelin Riga corresponds very well to the traffic flow intensity in the city.

Riga is the capital of the Republic of Latvia, and it is not only the centreof industry, business, entertainment and tourism, but also the home for about800000 inhabitants. The most important and famous place in Riga is the OldTown, which in 1998 was joined by UNESCO to the heritage of the worldculture. Now, at the same time, the Old Town is the place in Riga most crowdedby tourists and polluted by cars. On the three main streets out of four around theOld Town there is a very intensive traffic flow, particularly heavy traffic goesright along the Riverside. According to an analysis conducted by Air ProtectionDivision of RCC, the air pollution in the Old Town frequently exceeds acceptablenational level the main reason of which is the intensive traffic flow around thecentre of the city [1]. During the last five years the number of vehicles in Rigahas increased almost 2 times [2] and air pollution has increased 1,5 times [1]. Thepresent situation in the Old Town is really very poor, therefore new solutions andimprovements are extremely necessary to save our treasure - the Old Town ofRiga.

In the present work we compared air quality data from 3 DOAS stationsin Riga and investigated how to decrease air pollution in the Old Town of Riga.The proposal was made to reorganise the flow of motor vehicles in Old Town andaround it.

Ambient air quality measuring stations in Riga

Air pollution in Riga today is monitored by two institutions:/ The State Hydrometeorogical Agency, which is using two DOAS-type

instruments situated at the roof level (from 1998, measuring thebackground pollution in city).

/ The Air Protection Division of RCC, which is using Air QualityManagement System INDIC AIRVIRO and one DOAS instrument onstreet level [3]. Measurements were started in 1992 as a result of co-operation between Riga and Norkoping (Sweden) supported by BITS(SIDA today).


Urban Transport and the Environment for the 21st Century 425

Air pollution in Riga and the Old Town today

At present the pollution levels of air in Riga and particularly in the OldTown are close to the limitations set by the national guidelines for nitrogendioxide NO] and sulphur dioxide SOi. An average yearly concentration for NO?bags overrun 60 jig/nr' in this year, and must be reduced till 40 pg/m^ in 2010;but seasonal (winter) concentration for SO? is designated 30 pg/nf in this yearand must be reduced till 20 |ug/nf in 2003. Measurements from DOAS stations inRiga are collected in Table 1.

Table 1. Mean values of air pollution in Riga measured by DOAS stations.Pollution,in jiig/m*

SO:(mean winter)

NO:(mean annual)

03(mean 24 h)Benzene(mean 24 h)Toluene

(mean 24 h)Formaldehyde(mean 24 h)

The place and time of measurementsV aide mar a

Street199636.81996/97

60.2

42.7

25.6

81.9

13.1

3"' JanvanStreet199717.2

1997/98

43.2

473

16.4

45.1

7.9

NometnuStreet19982321998/99

29.5

40.7

222

629

7.1

Kengaragsregion199814.0

1998/99

25.7

627

21.8

66.9

-

Imantaregion199818.11998/99176

48.7

19.5

89.4

7.8

TvaikaStreet199910.81999/00

24.8

572

17.1

75.8

8.7

The limits for 24fig/rn^ for ozone;formaldehyde.

hour values in Latvia are stated next: 125 fig/m for SO]; 65100 jug/rn^ for benzene; 600 p.g/m for toluene and 3 pg/m^ for

Another way to obtain indirect air quality characteristics in Riga is to usethe capabilities of AIRVIRO air quality management system in RCC [3]. It isrunning by a HP 9000 series workstation. A digital map of Riga with scale1:10000 as a part of software covers an area of 20x 20 km and is used both foraccurate wind field calculations and the visualisation of results. Specialmeteorological equipment is on-lined via modem in order to evaluate theatmospheric stability and to measure different parameters necessary for thecalculation dispersion models. Emission database (EDB) contains data aboutmore than thousand points (smokestacks) and 300 linear (street) sources pollutingair in Riga. Dispersion calculations of mean winter SO] concentrations in Rigagave result with maximum 29 |ig/nf (including industrial plants, central heatingenterprises and private boilers) in west part of city (Agenskalns region) whichcoincide very well with measured values (Table 1). Calculations of mean seasonalNO] dispersions from traffic flow (traffic is giving about 80% from all NO]pollution in Riga) on main 300 roads in city gave values 50-60 fig/rn^ in the


426 Urban Transport and the Environment for the 2 1st Century

Central part of Riga, and above 40 jdg/m^ in the entire city. These values also arecomparable with real measured data (Table 1). Also actual concentrations of NO]in the Old Town are within 50 - 60 |ug/m\

General information about motor vehicles in Riga

During the last 5 years the amount of motor vehicles in Riga has increased almost2 times and now every third resident of Riga possesses a car. On January 1 , 2000in Riga there were registered 221307 motor units:

O 174833 light vehicles (1/3 of all the light vehicles in Latvia),"=> 25450 heavy vehicles (1/5 of all the heavy vehicles in

Latvia),"=> 3540 buses (1/4 of all the busses in Latvia).

Every vehicle using gasoline or diesel petrol is a source of nitrogen oxides (NO,NO] and N]O), carbon oxides (CO, CO?), sulphur dioxide (SO] - from dieselfuelled cars), and unbumed hydrocarbons [4]. Most of all cars travelling throughRiga every day are 15-20 years old (Table 2).

Table 2. Proportions of used/new cars in Riga on the beginning of 2000.Year of release

1975-19791980-1984

1985-19891990-19941995-1999

Proportion14%

38%35%9%4%

We counted the cars on all main streets around Old Town last summer (1999).From three parts there are large streets (Kr.Valdemara, 11* November, 13*January) with 2-3 lines in both directions, but two remainders (Merkela andRaina) are one-way streets with only 2 lines. As it seen from Table 3, the numberof cars on Merkela and Raina streets changed little from 1994 (as one-way andnarrow streets their exhausted permeability resources). However the traffic flowon two larger streets (Kr.Valdemara, 11* November) increased markedly - 1.5 to1.7 times, but on 13* January street - only 1.06 times by comparing with 1994.

Table 3. The number of traffic units on the 5 streets around the Old Town on aworking day (C - light cars, H - heavy vehicles, B - busses)

CHB

MerkelaStreet

199413848160662

199912137180623

Rainaboulevard

199410844114649

199911185145620

Kr. Valdemarastreet

199444398645770

1999677411018609

11*Novemberembankment1994198703151133

1999353842928371

73'* Januarystreet

199422785490968

1999242323831432



Real air pollution data obtained from the OPSIS measurement station of the RigaCity Council were compared with the quantity of vehicles on Brivibas Street(Figure 1). NO] concentrations on this street correlate the intensity pattern of thetraffic flow. It means that in Riga almost all pollution with NO] comes from themobile sources and reorganisation of it is a key for cleaner air. It is possible to seehow changes the intensity of the motor flow in different parts of working day.The most intensive motor flow on the Brivibas Street is from 8^ to 19T

Brivibas street in working day (July)

2500

11 13 15 17 19 21 231 3

Figure 1: Comparison of traffic flow and NO] pollution on Brivibas Street intypical working day.

Factors influencing air pollution in the centre of Riga

Density of buildings. The Old Town was built mostly 200-300 years ago andstreets are very narrow but houses - high. Nevertheless, there is lot of light cars inthe Old Town (see Table 4), since many business offices and places forrecreations are located exactly there. Though middle part of city was built on atthe turn of 19 /20 centuries - high houses mostly in art nouveau stile and largerstreets but with very marked canyon character. Newest regions in Riga were buildup during Soviet time with characteristic uptowns in a Soviet-stile and very largestreets with certain distance from houses. Therefore an influence of traffic causedpollution is more important in the central part of city, where housing more closureand streets narrower.Closeness of green belts. There are only a few small parks in the downtown Rigalocated at the very border of the Old Town. Besides they great number of parkedcar surrounds all. There are quantity of parks (some few of them very old andbeautiful) and green belts in Riga outside the Old Town. Nevertheless negative



trend is observed of late years to built car-parking places (also underground) inRiga's parks and green belts.

Table 4. Number of cars in Old Town.Cars parking and driving in the Old TownCars parked in the Old Town early in the morningCars parked in the Old Town in the middle ofworking daySingle passes (12$) issued for cars to drive into theOld Town during one working daySingle passes issued for inhabitants of Old Town todrive into the Old TownOperative cars (police, ambulance etc.) driving intothe Old Town during one working dayRegular passes issued for offices (parliamentincluding) to drive into the Old TownRegular passes issued for private persons to driveinto the Old Town

Number4342191

130-150

220-250

35-40

-1500

-500

Territory relief. Dominance relief in Riga is plain. In olden times there weresandhills around the city, but nowadays they are built up. Baltic Sea is locatedonly 13 km from the Centre of Riga, and the Old Town is situated along theembankment of River Daugava. The street along the riverside (11^ Novemberembankment) presently is the main traffic link to the Riga seaport and all theheavy traffic serving Riga seaport is using it.Weather. Weather conditions in Riga are mostly influenced by the Baltic Seathereby winters are mostly with rather little snow and mildly cold (-15 to -20 °C)but summers are wet with average temperatures around 14-19 °C (exception isthe middle of the summer when the temperature is reaching 25-32 °C). The windis mostly from South and South - West direction -blowing to the Sea.Seasonal, daily pollution. There is higher sulphur dioxide pollution in Rigaduring winters, when central heating network and personal boilers are working.This part of pollution is quite low in summer. In city the main pollutant is traffic,therefore traffic flow daily changes influence pollution very mutually, whileseasonal influence is less enounce. On Saturdays and Sundays air pollution inRiga is lower, since many people are going to rest outside of Riga and the trafficflow in the city is decreased. Friday is a specific day, when many peoples aregoing to countryside or Sea-side (Jurmala) after work or celebrating the weekend.Inverse temperatures. Under special weather conditions the air temperature islower at ground and the wind is slow - a cover of warm air is formed above thecity and pollution caused by traffic and stationary sources can not escape [5], Theindicator of such weather is the differential temperature, which is a differenceof temperature between two thermometers at different height from the groundlevel (the temperature at 2 and 8 meters above ground are measured in our case).Such situations are observed in Riga very frequently but mostly in nights duringspring and autumn seasons.



Modelling of the present air pollution situation in the Old Town

The INDIC AIRVIRO system simulates and evaluates air pollutionlevels at various locations of the city and processes the data in order to predict airquality from a number of criteria and parameters measured, including data ofMeteorological Service and results of episodic measurements. Results are viewedas dispersion lines on the map and values of pollution of every interesting areacan be specified. If necessary, the system allows making different manipulationswith simulated concentrations. For example, the background level can be added,by conversion from NO% to NO] described by formula:X] = 0.73*Xi*exp (-0.00452*Xi+0.003014*0.0001*Xi*Xi), where Xo - value ofNO] concentration; X\ - corresponding NO% value.

We simulated NO? dispersion in Old Riga, coming from surroundingstreets. The main parameters for this simulation were the real traffic flow on allthe 5 streets around the Old Town (see Table 3), including Aspazijas-BastejaBoulevard. Emissions from light cars parked in and around the Old Town wereaccounted for by considering all the area of the Old Town as a single pollutingarea source. Firstly the background pollution (parked cars) was calculatedseparately and the pollution caused by traffic flow on the main streets around theOld Town were added to it.

The obtained results show that the largest part of Old Town is includedin a region where NO? concentrations are reaching 50 pg/nf and more. Thispollution mostly comes from 3 sides: Kr.Valdemara street, the 11^ Novemberembankment and the 13* January street. The cleanest places in the Old Town(NO] concentrations 40 pg/nf and less) are only in the area of St.-Peter church.

To compare the obtained simulation levels in the Old Town with themeasurements done by OPSIS it is necessary to choose a certain place - the placewhere OPSIS is located, since this system provides the most precise data onlyabout the street on which it stands. So, looking at the data obtained by OPSISfrom Kr.Valdemara street, it is seen that concentrations obtained in the process ofcalculations are very close to reality (Table 1). Therefore we can conclude thatour dispersion simulations can be compared with reality and used to obtainfurther prognosis.

Prognosis of air pollution in the Old Town of Riga:

The optimistic and pessimistic models

To evaluate the necessity of traffic flow reorganisation we simulated theair pollution in the Old Town of Riga for 2005: in the case nothing is being doneto improve the traffic flow of the city of Riga (pessimistic model) and in the casewhen traffic reorganisation will be made (optimistic model). This simulation wascarried out by AIRVIRO air quality management software. On the base of theexisting traffic flows on the 5 streets around the Old Town the extrapolationsaccordingly to pessimistic and optimistic models were made and related pollutiondispersion calculated (Figure 2).



Number of buses on the streets

around the Old Town

Pesimistic

Optimistic

1999 2005

Number of heavy vehicles on the streets

around the Old Town

Pesimistic

1994 19992005

Number of light cars on the streetsaround the Old Town

300000,

200000

100000Pesimistic

Optimistic

1999 2005

Figure 2. Total number of traffic on streets around Old Town during workingday - existing situations and prognoses.



The dispersion calculation shows a very dramatic situation in pessimisticmodel for 2005 - mostly all Old Town will be in the region where NO]concentrations exceed 50-60 jug/m*. It means that air pollution values will exceedthe values of national guidelines and will be extremely dangerous both for peopleand the environment. An optimistic model includes next traffic flowimprovements (foreseen in Traffic Conception of Riga for 1999-2003 [6]:1) the heavy traffic flow on the 11* November embankment will be closed;2) the traffic flow on Basteja - Aspazijas boulevard will be eliminated;3) parked cars and traffic in the Old Town will be eliminated and new multi-

storey car parking places will be built.The results of dispersion calculations for an optimistic model showed that

the air pollution in the centre of Riga in 2005 will be better than in 1999.Dispersion model clearly shows that it is possible to reduce the air pollution in theOld Town of Riga to 40 |ig/nf and less. Because of a low penetrability of thestreets and inconvenient routs there are frequent traffic jams causing increased airpollution on Kr.Valdemara street, Raina boulevard and Merkela street, especiallyat the end of working days.

Some proposals what to do to improve the air quality in Old Town andRiga could be next:=> The penetration of streets in Central part of city must be increased. Nowadays

about 80% of all cars travelling around Old Town are looking for free parkingplaces. Solution will be to build up new car parking places (under-ground andmulti-storey) with moderate parking price.

^> The heavy traffic on the 11* November embankment must be eliminated and anew ring road Highway to Riga harbour must be built.

o The old motor vehicles must be completely substituted by new ones.Unfortunately, at the present situation this action is not realistic because ofhigh taxes, short-term warranties, low incomes for most population.

Conclusions

1. The main air polluters in the Old Town are motor vehicles driving on theroads around the centre of the city.

2. The air pollution with nitrogen dioxide in the Old Town has grown up from36 pg/nf in 1994 to 48 ug/nf in 1997 and 51 pg/nf in 1999. The number ofcars registered in Riga has grown up from 115975 (1994) to 221307 (1999).

3. Pessimistic prognoses (nothing is done to improve the traffic around the OldTown) indicate that air pollution with NO] in 2005 in the centre of the citywill increase even up to 68 ug/nf in 2005 (the number of cars will increaseto 225000).

4. Optimistic prognoses means that the traffic flow around/in the Old Town ofRiga will be reorganised. Different models were elaborated and relatedpollution decrease was calculated by proposing the following conditions:



The heavy traffic flow on themain streets around the Old Townis closed.

More serious inspection ofvehicles driving in and aroundthe centre of the city is being setup and heavy traffic flow on the11 November embankment, aswell as the traffic in the OldTown are closed (new parkingplaces around the centre of thecity are built).

Pollution will decrease to 41i/nf in2005.

The total NO% pollution in2005 will decrease by 12(ug/m (the backgroundconcentration of NO2 in theOld Town today produced byparked cars and traffic insidethe Old Town).

New parking places for cars(underground and/or multi-storey) around the Old Town ofRiga are built and heavy trafficflow on the main streets aroundthe centre of the city is closed.

Pollution will decrease to 39/nf in 2005.

References

1. Data from reports of Air Protection division of Riga City Council.2. Republic of Latvia Road Traffic Safety Directorate, http://www.csdd.lv/3. Airviro Specification, Indie Air Quality Management (1993), SHMA, p. 100.4. Fair A., Weaver C.S. and Walsh M.P., Air Pollution From Motor Vehicles

(1996), The World Bank, Washington DC.5. Alloway B.J.and Ayres D.C., Chemical Principles of Environmental Pollution

(1997), pp. 86-157.6. Traffic department of Riga City Council "Traffic Conception of Riga for

1999-2003" (1999), 150 p.


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