100年前，冬季季风只会将零星的戈壁沙尘带到香港。但现在，它带来了更多来自近处的风沙。
A hundred years ago the winter monsoons brought little more than a sprinkling of Gobi desert dust to Hong Kong. But today they bring much more from sources closer to home.
在边境彼岸，内地的珠江三角洲地区将100年的工业化进程浓缩到20年，将沉睡的村庄转变为每日24小时不停工作的制造区。
Across the border, China's Pearl River delta region has crammed a century's worth of industrialisation into twenty years, transforming sleepy villages into 24-hour manufacturing zones.
香港最严重的污染可以追溯到佛山--一座距香港西北约150公里、拥有600万人口的城市。佛山被称作中国南部的陶瓷之都，在当地的空气质量图上，这座城市经常出现在最严重污染带的中心。在这里，烧煤的窑炉喷出大量的黑色废气及二氧化硫和二氧化氮等化合物。
The worst of Hong Kong's pollution can be traced to Foshan, a city of 6m about 150km northwest of Hong Kong. Known as the ceramics capital of south China, Foshan is often featured on regional air quality maps at the centre of the darkest circle of pollution. Its coal-burning kilns spew out huge quantities of sooty waste and chemical compounds such as sulfur dioxide and nitrogen dioxide.
这些污染物被从10月到4月最常见的北风带到香港，导致香港冬季的污染严重加剧。
These pollutants are carried to Hong Kong by the northerlies that prevail from October to April, resulting in much worse pollution during the winter months.
在春夏两季气流扭转方向后，或许可以指望反向的风缓解冬季的阴霾。但这已不再是确定无疑的，正如5月14日的大雾所展示的那样。
After the air stream reverses course in the spring and summer, reciprocal winds could be counted on to bring some respite from the winter haze. But this is no longer guaranteed, as the smog of May 14 showed.
"过去几年发生了根本性的变化，那就是，从东北或东南吹来的风都有可能带来雾霭，"香港天文台台长林超英(CY Lam)表示。"我们可以看到来源确定是台湾西部的雾霭。颗粒物可能来自很多方向。"
"In the past few years there has been a fundamental change- that is the probability of haze in the case of winds coming in from the northeast or southeast," said CY Lam, director of the Hong Kong Observatory. "We could see haze coming from clearly identified sources in western Taiwan. The particulate matter could come from many directions."
汽车和火力发电厂产生的污染，也在香港的污染中占据了相当比例，而被称为"陆海风循环"的当地刮风模式更加剧了这种污染。在钢筋混凝土打造的城区温度升高时，污染物上升并飘向海洋，但又会被温度较低的海风带回香港。
Hong Kong's vehicles and coal-burning power plants also generate a fair share of pollution within the city, which is then exacerbated by local wind patterns and what is known as "land-sea breeze circulation". As concrete-clad urban areas heat up, pollutants rise and disperse over the ocean, only to be carried back into the city by cooler sea breezes.
香港科技大学(University of Science and Technology)大气科学教授及专家刘启汉(Alexis Lau)表示："当吹向海岸的风到达时，它实际上带来了更多被污染的空气，而非清新的海风。"
"When onshore wind comes it actually brings more polluted air instead of a very nice ocean breeze," says Alexis Lau, a professor and expert on atmospheric science at Hong Kong'sUniversity of Science and Technology.
为容纳迅速增长的4500万人口，珠江三角洲一带的各个城市快速扩张，进一步增加了问题的复杂程度。刘启汉表示："城市化导致的气温升高，加剧了陆海风循环，使外部的风更难进入，因此，污染物的消散也变得更加困难。"
The problem is compounded by the rapid spread of cities across the Pearl River delta to accommodate a burgeoning population of 45m. "Increased heat due to urbanisation strengthens the land-sea breeze circulation and makes it more difficult for outside winds to penetrate, so it is more difficult for the pollution to dispers," says Mr Lau.
香港政府尚未找到综合方案，解决既影响旅客也影响居民的空气质量问题。与内地的跨境合作进展缓慢，尽管边境另一侧有5万多个港资工厂。
Hong Kong's government has yet to develop a comprehensive solution to tackle the air quality issues that affect tourists and residents alike. Cross-border collaboration with the mainland has proceeded slowly, even though there are more than 50,000 Hong Kong-invested factories across the border.
5年前，两地政府承诺，到2010年，将按中国内地的空气质量标准实现减排。内地的标准在很多方面比香港标准更为严格。但是，如期实现目标似乎不太可能了。
Five years ago, the two governments pledged emissions reductions by 2010 according to mainland China's air quality standards, which are in many cases more stringent than Hong Kong's. But it appears unlikely that the targets will be met on time.
刘启汉表示："如果减排真的发生了，我们应当能看到天空的状况出现改善。但现在我们还没有看到。"
"If the reduction is actually happening we should be able to see the sky improving," said Mr Lau. "This is not the case yet."
