Canine cops

日期:2019-03-07 02:09:11 作者:达乌冀 阅读:

By Debora MacKenzie TWO Swedish sniffer dogs have found more than 10 tonnes of mercury hidden in drains, electrical equipment and laboratories in the past two years. In December, two more specially trained dogs will begin hunting for PCBs. The mercury-sniffing dogs, an Alsatian named Froy and a Labrador retriever called Ville Sigmund, were the brainchild of Sweden’s national training school for guide dogs in Sollefteå. Canine graduates of the school that are too aggressive to guide the blind have long been used to sniff out explosives in places like Kosovo. Now they are helping to clean up the environment. Five years ago, the Swedish parliament decreed that all old stocks of mercury, which is toxic, must be cleared up and properly disposed of by 2001. Kjell Avegren, an environmental consultant working with the training school, says the dogs have not only found mercury lurking in unexpected places, they have also made collecting it much cheaper. “Most of the mercury is in old equipment, such as pressure meters and thermostats,” he says. But a lot is also trapped invisibly in the U-bends of sinks in dental clinics and research laboratories, and even hiding under floorboards after old spills. In the laboratory of one water treatment plant, 8 kilograms of mercury were found lurking in a U-bend. “We are finding that only about 5 per cent of drains we check contain mercury,” says Avegren. “The dogs save lots of money by finding which ones need cleaning.” It costs about £50 to clear a single drain. The dogs can each check 110 drains a day, and they can sniff out as little as 1 milligram of metallic mercury. Although trained to sniff out the metal, they can also detect mercury salts and methyl mercury, the most toxic form. The dogs have so far located 10 tonnes, most of it metallic mercury. Some 7 tonnes have been collected, of which 1.3 tonnes came from schools. The Swedish Environmental Protection Agency must now decide how to dump the mercury permanently. The dogs are still busy—the Swedish EPA estimates that another 40 tonnes has yet to be found, mostly on industrial sites. Norway is planning a similar programme, and the US is also interested. Meanwhile, the training school in Sollefte å is moving on to tackle PCBs. The pollutant was used in some old plastic building materials, for example, for window frames, especially those used in prefabricated buildings in Sweden and Germany. It is expensive to clear up, says Avegren, as it is not obvious which windows are edged with PCBs and which are not. Training dogs to sniff PCBs was more difficult than for mercury, says Avegren, because there are many different kinds. Nonetheless,