Air quality in portal areas is usually compromised by local emissions related to many different typologies of commercial, industrial and touristic activities.
Therefore, in order to reduce the consequences on the environment and human health due to exhausted gas released near the water surface and the ground, the air quality of portal areas should be monitored in all the different subareas of a harbour, by dividing it according with the different intended use areas.
Thus, it will be possible to pinpoint the most critical zones of each considered port and consequentially to plan specific actions for improving air quality in those areas.
In particular, this chapter deals with the emissions of VOCs (Volatile Organic Compounds) which play a key role in the short term chemical composition of the troposphere, as well as in climate changes (Murrells & Derwent, 2007).
Are classified as VOCs, in fact, both hydrocarbons containing carbon and hydrogen as the only elements (alkenes and aromatic compounds) and compounds containing also oxygen, chlorine or other elements, such as aldehydes, ethers, alcohols, esters, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). According with the Italian regulation (article 268 of the 152/2006 Legislative Decree) VOCs are those organic substances which have at 293.15 K (20°C) a vapour pressure greater then or equal to 0.01 kPa.
The contents of this chapter have been developed considering the Italian and European regulations, which applications will improve the environmental quality in portal areas.
Among these, the Marine Environmental Protection Committee (MEPC) of the International Maritime Organization (IMO) has developed a protocol of an International Convention for the Prevention of Pollution from Shipping (IMO/MARPOL 73/78) establishing a monitoring program for reducing emissions (IMO, 2008).
In the light of these considerations, the main goals of our chapter are:
To elaborate an air quality index weighed on the atmospheric concentrations of all VOCs, in order to obtain a single number that expresses the overall VOCs pollution of an area.
To validate this index through its application in some case studies areas
To pinpoint the most critical areas of the analysed harbours in order to select BAT (Best Available Technologies) and best practices for mitigating VOCs concentrations and improving local air quality.
2. AQIvoc index elaboration
In order to elaborate an Air Quality Index for VOCs, called AQIvoc, weighed on the atmospheric concentrations of all VOCs as well as on dangerousness and impact of each substance in atmosphere, we assigned to each VOC an environmental impact coefficient (α) interrelated with its emission limit value according with the Italian regulations
Where:= environmental impact coefficient for the i-th VOC
Vmax = highest emission limit value among all VOCs
Vi = emission limit value for the i-th VOC
The values of the environmental impact coefficient were assigned in proportion to the emission limit value specified for each ith class, giving a coefficient of greater environmental impact where the regulatory limit value of emission in atmosphere is lower.
In particular, considering the Italian regulation, the Annex III of the fifth part of the 152/2006 Legislative Decree shows a classification of volatile organic compounds divided into five classes according to their impact on the environment; consequentially the same Decree assigns to each of the five classes a maximum value of emission in atmosphere (Table 1).
|Pollutants classification (152/2006 Legislative Decree)||Emission limit in atmosphere (152/2006 Legislative Decree)||environmental impact coefficient α|
|Class I||5 mg/Nm3||120|
|Class II||20 mg/Nm3||30|
|Class III||150 mg/Nm3||4|
|Class IV||300 mg/Nm3||2|
|Class V||600 mg/Nm3||1|
Briefly, the equation for the AQIvoc indices evaluation is the following:
AQIvoc = Air quality index related to VOCs concentrations= environmental impact coefficient for the i-th VOC
vi =atmospheric concentration of the i-th VOC detected in the analysed intended use area= highest value of (related to the intended use portal area with lower concentrations of VOCs pollution in the atmosphere)
Consequentially, these values, standardized in a range from zero to hundred, have a comparative nature, with the value 100 assigned to the lowest VOCs concentration detected (in a certain port, in a certain detected area and in a certain season).
3. Case studies: The harbours of Anzio, Formia, Terracina and Ventotene
In order to validate the above mentioned methodology four ports of the Lazio region have been selected as case studies (Fig. 1)
In each port, divided into subareas according with its different intended use zones, was carried out an annual field data gathering, detecting VOC concentration in each season.
Lastly, an air quality matrix with VOC concentrations and AQIVOC values (for each intended use area in each season) has been elaborated for each analysed port.
4. Data gathering methods
In each of these four ports were monitored the concentrations in atmosphere of the following 18 VOCs: Dichloromethane; 2-Methylpentane; Hexane; Methylcyclopentane; Chloroform; 2-Methylhexane; Cyclohexane; Benzene; Heptane; Trichloroethylene; Methylcyclohexane; Toluene; Tetrachloroethylene; Ethylbenzene; m- p- xylene; o- xylene; 1,2,4-Trimethylbenzene; 1,2-Dichlorobenzene.
The concentrations of these substances were sampled seasonally in each intended use area of the four ports, leaving many radial diffusive samplers called “Radiello ®” (Bruno et al., 2008) for a period ranging between 7 and 10 days per season (Fig. 2)
All the obtained VOCs concentrations have been compared spatially and seasonally in order to pinpoint portal areas and seasons where VOC pollution was higher.
4.1. VOCs concentrations results in the four case study harbours
The following graphics summarize the results obtained in each port, considering the seasons and the intended uses zones.
The sums of all the 18 VOCs concentrations recorded during each data gathering were compared, in order to rank in each port the intended use areas and the seasons according with their VOCs pollution (Tables 2 and 3). In order to have a reference value to define the "minimum" VOCs pollution of each port, a Radiello was placed in the most area distant from every sources of pollutant emissions (end of the breakwater) during the season with lower portal activity (winter). Unfortunately, it was no possible to obtain this value in the harbour of Formia because the Radiello in the breakwater has not been found at the end of the ten sampling days.
4.2. AQIvoc indices in the four case study harbours
The AQIvoc index equation has been used for the elaboration of four air quality matrices that provide an overview of the air quality level within each one of the four portal areas. This approach allows to highlight those portal activities that have a major impact on air quality, and will be preparatory for the choose of which BAT or best practices is better to use for the mitigation of air pollution in each particular harbour.
In order to facilitate the reading of the comparison of the results, the AQIvoc values have been subdivided into three categories: low VOCs pollution, values under the twenty-fifth percentile (green boxes); average VOCs pollution, values between the twenty-fifth and the seventy-fifthpercentile (yellow boxes) and high VOCs pollution, values over the seventy-fifth percentile (red boxes).
Before that, the statistical distribution of the data has been considered, highlighting unusual observations (outliers and extreme values) by means of boxplot analysis.
In particular, the box-plot method analyzes the distribution of data considering the median, the interval between interquartiles, the outliers values and the extreme values of individual variables. The length of the box was considered as the range of values between interquartiles, or rather between the twenty-fifth and seventy-fifth percentile. Consequently, the outliers values are those that are at a distance between 1.5 and 3 boxes from the top or the bottom edge of the box, between the twenty-fifth and seventy-fifth percentile; at the same way, the extreme values are distant more than 3 boxes from the top or bottom edge of the box. The purpose of the method is therefore to identify these values in order to get a distribution composed by values statistically attributable to the same population.
The box-plot application proceeds step by step in order to be able to select all the extreme and outliers values up to a statistically homogeneous distribution of the population.
In this way, the 4 unusual values have been pinpointed and removed assigning to them the maximum IQAcov value of one hundred (Figure 11).
It was therefore possible to elaborate the 100 standardization of the IQAcov value, considering a statistically homogeneous distribution (Table 4).
Moreover, the results have been registered in a GIS (Geographic Information System) database that contains a comparative spatial analysis of IQAvoc values in order to produce thematic maps able to pinpoint areas where the VOCs pollution was higher (some examples of these maps will be reported in the following maps).
5. Best practices for air quality improvement in portal areas
Aim of this paragraph is to illustrate some BAT (Best Available Technologies) and best practices for mitigating VOCs concentrations and improving local air quality in those portal areas characterized by high concentrations of pollutants.
The obtained results show that the main sources of pollutant emissions in the four analyzed harbours are the Internal Combustion Engines (ICE) of Ro/Pax ferries and hydrofoils, pleasure boats, fishing boats as well as cars and trucks circulating in the ports.
Excluding fishing boats, these sources of emission are all highly dependent on tourism activities which involve an increase of vehicular traffic in the port areas, an enhanced number of daily trips of ferries and hydrofoils and, last but not least, a heavy pleasure boats traffic.
Nowadays, the best practices and technologies for mitigating air pollution in portal areas are:
SSE (Shore-Side Electricity) enables ships at port to use electricity from a local power grid through a substation at the port to power loading and unloading activities, electronic systems, fuel systems, discontinuing the use of their auxiliary engines. The emission reduction efficiency of this solution is about 94% for VOCs (De Jonge et al., 2005).
DWI (Direct Water Injection) is a technology which consists in introducing into the cylinder a mixture of water and pressurized fuel which allows lower consumption and emissions (Wahlström at al., 2006).
Use of low emission fuels: in particolar seaweeds hold a huge potential as a biofuel. Briefly, biofuels are used for fighting climate changes because the same amount of CO2 that is released from combusting biofuels has previously been taken up from the atmosphere as the plant grows, thus not leading to any net increase in the concentration of CO2 in the atmosphere (Opdal & Johannes, 2007).
Optimization of combustion processes in ship engines by means of particolar devices able to optimize combustion disaggregating hydrocarbons (gas emission reduction up to 75-80%).
The use of the IQAcov index and the implementation of the best practices and technologies described in the last paragraph could be considered useful tools for monitoring and improving air quality in portal areas for stakeholders and decision makers such as port/maritime authorities, licensed port company operators and local and governmental authorities involved in port jurisdiction.
Indeed, as recommended by the European Sea Port Organisation (ESPO, 2003), among the main environmental objectives which the EU port sector should aim to achieve there is the increase of environmental awareness, the implementation of environmental monitoring and the use of best practices and technologies on environmental issues.
These targets, together with the promotion of environmental monitoring in ports, are fully included among the ESPO top ten environmental objectives that the European port sector should pursue.