Batgung

Oldtimer, thanks for your feedback. Some comments:

But changes in the surrounding buildings, traffic and industrial activities can alter the trends. The period of record for these parameters are short unfortunately to draw strong conclusions.

Fair point. The conclusion that air pollution levels haven't changed that much are true if you'd been standing next to the monitoring station the whole time. But that effect may be due to some localised changes as you describe. I'll have to take a look at readings from some of the other stations around Hong Kong to see if the same patterns appear.

This brings me to the question whether the criterion for defining reduced visibility, that is, "visibility below 8 kilometres when there is no fog, mist, or precipitation" has been consistently applied since the 1960s, in terms of locations of the line of sight and equipments used. I wonder if human "eyeballs" were used in the early years.

That would be interesting to know, but even if it explains some of the change in the numbers, there's no doubt in my mind that visibility has got worse over the last 10-15 years.

Finally, to what extent can SO2, CO and O3 affect visibility? Dust blown from construction sites may play a role in this - but this could be a non-issue.

Wikipedia has a good article about smog. It explains that the older versions (eg for which London was infamous) were caused by a mixture of smoke and SO2. More recently we face photochemical smog, which it says "is the chemical reaction of sunlight, nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere, which leaves airborne particles (called particulate matter) and ground-level ozone (O3)."

CO is also given as one of the ingredients needed to make O3, so although it is colourless itself, the O3 it produces is not.

MrB

We've been forwarded this photo from the 1968 HK Standard, and 'Comments from a long time Hong Kong resident':

The CLP power station in Hung Hom used high sulphur fuel oil and had short chimneys because of its proximity to the airport. When the wind blew from the east the smoke rolled across the Kowloon peninsula at very nearly ground level. The sulphur in the air could be so bad that your saliva would become acidic and very painful in contact with tooth fillings. 
 
Similarly HK Electric had a power station complex in the middle of North Point and the government had incinerators at Kennedy Town and Tsing Yi all belching out smoke within residential districts.

Here are similar calculations for the figures from the measuring station in Kwun Tong:

And

These are more similar to the Central & Western readings, with pollution in 2007 roughly equal to or better than 1990. We might guess that the Kwun Tong air quality would improve after the airport closed in 1998, but that doesn't seem to have made a big impact on any of the figures between 1995 and 2000.

Again, the figure that stands out from the 2000-7 readings is the Ozone level, increasing where others are falling or staying steady.

MrB

Hi,

I was just wondering how HK was, and how the smog was going since I left -- evidentally not too good.
One reason that you don't get an increase across the board is that I believe you get a chemical reaction between NO2 and O3. So if your NO2 goes up, it will keep your O3 down -- I believe this is why there is often less ozone in, say, Kennedy Town than Sai Kung, and why you often get an ozone free period in the morning (NO2 pollution from the cars interacts with the O3 for a short while) Have look here:

http://www.environmental-protection.org.uk/air-quality-and-climate/air-quality/ozone-pollution/

Here are the figures from the measuring station in Tap Mun:

So if you live in Tap Mun, you are fully justified in saying that the pollution is getting worse!

If you've been to Tap Mun, you'll know it's a quiet island, far from any built-up areas. In that way it can show changes in pollution levels that are not related to changes in local conditions - more traffic, new buildings, etc.

Also remember that these numbers just show changes - whether it's getting better or worse. The absolute readings aren't shown here, but we'll need to come back to them in a future article. They'd show that for most pollutants, though levels have increased in Tap Mun, they are still lower than levels in the built-up areas. The clear exception is Ozone, where levels in Tap Mun are much higher than in the city - as Conrad predicted above.

OldTimer, thanks for taking the time to look at these numbers. Some feedback:

First, starting with the July 2007 figures, Monk Kok, Central and Causeway Bay observed consistently higher APIs than others.

Had you spotted that these are the three 'roadside' stations? So they tend to have the worst figures, reflecting what you breathe when walking next to a busy road.

I looked for improvements in the air quality during the weekends when offices and factories are closed and there seem to be such a pattern but not a strong one.

I hadn't thought of looking for variations across a week, so that's a good idea for another thing to look at in future.

When the December 2007 data are compared with the July 2007 data, the air pollution was much worse in the winter month. For example at Causeway Bay, the API varied between 40 and 50 during July, and between 60 and 130 in December. What could have caused such a big increase in December, more traffic and shopping activities? More factories working to meet Christmas orders, or colder but polluted northerly air from the border city at the border?

You can see a similar trend in the visibility figures - summer has best visibility, winter has worst. I think the wind direction is the main factor. Summer's winds from the south blow in fresh air from the sea, while in winter the wind comes from the north bringing polluted air from the mainland. Summer also tends to be the cloudy, rainy time of year. I haven't seen that mentioned as affecting pollution levels, but I think both cloud and rain will help lower pollution levels.

This report from Civic Exchange has a good discussion about the effects of wind direction on local pollution, but please also read my concerns about how the report's results were presented.

For Tap Mun, which is way out in the country side with little industry and commerce, one can see the late afternoon peaks on many days during rush hour traffic.

It would be worth digging into the detailed readings to see which pollutant caused those peaks. My guess would be Ozone. The API is a coarse measure - a bit like the visibility readings. It shows us the worst figure out of the 8 sub-indices that are calculated each hour. That makes it a good and easy-to-understand indicator to the public of whether pollution levels are high enough to cause problems or not. But that also makes it harder to interpret the causes of problems. For that we need to look at the levels of the individual pollutants.

Also, it's probably something other than rush hour traffic causing the peaks. Tap Mun has a population of around 100, an assortment of boats, but no motor vehicles. Not much of a rush hour in those parts of the world ;-)

Something outside Tap Mun was also affecting its air quality.

This satellite view shows how rural Tap mun is (see red marker on lower right), but also how near the South China industrial miracle is, just to the north. I'll come back to this in a future article, seeing if we can get a better idea of how much pollution is generated within Hong Kong, and how much comes from Southern China.

I can e-mail you my Excel files if you are interested Mr. B.

No need for those, but I'm very interested to keep hearing your conclusions as you think about it some more. It's good to have a second set of eyes looking at the numbers, and keeping me honest!

regards, MrB

Mr. B., as suggested, I read your comments that appeared on another Batgung page. I haven't read the researchers report or their methods of investigation (I need more time). This is about the Media's headline saying "NEW RESEARCH SHOWS 53% OF THE TIME HONG KONG’S DIRTY AIR CAUSED BY HONG KONG SOURCES OF POLLUTION".

I interpret it saying 53% of the time in a typical year, Hong Kong's dirty air can be primarily attributed to its own pollution sources. Take it to the extreme criterion, for each day or hour, sum up all the pollutants across Hong Kong, when the researchers can differentiate (I wonder if they can) that X tonnes came from outside, X plus (1 or more) tonnes came from within, then this particular day or hour is counted as a part of that 53%.

I don't think they meant to say over half (53%) of HK's air pollution comes from local sources.

I can't get my hand on wind-rose data that show the frequency of winds from the different directions. When I look back into my days flying kites during the summer, most of the time I got S, SE or SW winds. W wind was infrequent. E wind must be up there somewhere but I tend to stay indoor due to inclement weather so don't know how frequent it was. Winds from the northern quadrant was very infrequent in the summer. On this basis and without making any detailed investigation, I would think that during the summer when most of the time the winds are from the southern quadrant, it would be also infrequent to see significant air-borne pollutants from north of the border. During the winter when northerly wind becomes dominant, Hong Kong would see her big share of the pollution coming from the north.

Quote from the 2006 annual report: "As a result of the enhanced vehicle emission control programme implemented by the Government since 2000, concentrations of respirable suspended particulates, nitrogen oxides and sulphur dioxide at roadside have been dropping gradually over the past few years." The graphs for the roadside stations show some I would call minor decline in these concentrations. Conditions could have been worse had there been no such government programme. Mr. B., your statistics for the Causeway Bay gives a more comforting picture.

I grew up in the 1940~50s four blocks from the Monk Kok station. The air was poor then, and the traffic here was busy but not as horrendous as shown in present photos -
http://www.epd-asg.gov.hk/english/backgd/bkg_mongkok08.php
It is great to see the 3-storey buildings survive to this day. It looks like the 4th floor living quarters are add-on's. There was once a gasoline station in front of them where the trees and shrubs are. Car washing was a part of its business.
And Great World Cinema was across the street - saw a movie there which featured B-29 bombers as part of the movie.

Here are the figures from the Yuen Long measuring station:

Next the Tung Chung measuring station:

And finally the Kwai Chung measuring station:

Funnily enough I started with a measurement of SO2 levels in Central that showed a significant drop over the last 7 years. But looking at SO2 levels for these last three stations, it's clear that the answer to 'Is our air pollution getting better or worse?' depends on what you measure, and where you measure it.