Old Venice has become famous for its pollution.
The claim is:
“As big ships sailed down the main canal, just a stone’s throw from the shore, my team recorded up to 500 ultra-fine particles per cubic centimetre – 500 times higher than clean sea air.”
Marine diesel engine exhaust gas contains toxic gases such as NOx(NO+NO2) and SO2 (Link)
ARPA (Agenzia Regionale per la Prevenzione e Protezione Ambientale del Veneto) publishes pollution values in and around Venice. Sadly not all stations report all values. If this is by chance or design, remains unknown.
Data was collected from the ARPA website since the 2.9.2017 when a air pollution measurement station within old Venice town started to collect data. The name of this station is “Rio Novo”.
Values collected are NO2, PM10, O3, SO3 and CO. Values are the max per hour of (µg/m3).
The stations are:
- Rio Novo (TU)
- Sacca Fisola (BU)
- Via Beccaria (TU)
- Malcontenta (IS)
- Parco Bissuola (BU)
- Via Tagliamento (TU)
- San Dona’ di Piave (BU) [Further away from Venice]
ARPA describes these as:
- TU = Traffic station in an urban area
- BU = Background station in an urban area
- BS = Background station in a sub urban area
- IS = Industrial station in a sub urban area
The traffic of ships big enough to transmit AIS signals is shown here, this EXCLUDES small traffic from local water taxis that could not be detected.
There are as such two stations that are important if one looks at Old Vence, “Rio Novo” that is situated in the old Venice and “Sacca Fissola” , that is close to the AIS traffic into Venice.
Here is the collected data as a box plot.
It is interesting to note that the NO2 values within the old town of Venice (Rio Novo) is a LOT higher that the values close to the AIS recorded traffic (Sacca Fissola). Could diesel powered water taxis be the problem, as Old Venice does not feature cars? Or is its imply the decomposition of organic waste by bacteria? (Link)(Link)(Link) (Link) (Link) Or are the chimneys from the high rising cruise ships drifting into the old city? The predominant wind direction in Venice seems to be North to East North East, making this unlikely though (Link).
PM10 (particulate matter at 10 microns) , Ozone (O3) and SO2 seems to be pretty even around Venice where it is recorded. See this article about the difference between PM10 and PM2.5, which seems not to be recorded very publicly around Venice.
There is a certain seasonality to the NO2 data but the main cruise ship season in summer has not yet been recorded by the “Rio Novo” station.
The correlation matrix shows that the strongest correlation is between “Via Beccaria” and “Malcontenta” (0.78), while the correlation between “Rio Novo” and “Sacco Fissola” is 0.63.
Adding the background station at “San Dona’ di Piave” to this matrix does not change the picture dramatically.
As an over all trend we can see that the station at “Via Beccaria” correlates around 0.7x with all other stations. “Via Beccaria” as a traffic station in an urban area in “New” Venice as such seem to show the overall trend for No2 in the whole area, even if its local values are not as high as at the station “Rio Novo“.
So what ever causes “Old Venice” to have the worst NO2 values without car traffic will also cause higher values in “New Venice” with car traffic. If it is just cruise traffic is doubtful as the higher values in “Rio Novo” are persistent and seem to come from another source than cruise ships alone. Since Nitrogen Oxides seems to be produced by both Diesel engines and decomposing organic waste, it seems more likely that Venice’s sewer problems (Link) and water taxis, buses might be the source.