就是通过打扫卫生，使污浊的环境重新变得自然干净。
By cleaning up-by getting back to natural wholesome conditions.
北京——每天大约有1000辆新车上路，使本来已经污浊不堪的城市更加拥挤。
BEIJING — Nearly 1,000 new cars hit the streets here every day, crowding a city already choked with pollution.
如果育雏室内通风不良，氧气就会逐渐减少，二氧化碳浓度增大，使空气变得污浊起来。
If the brood indoor and ventilated bad, oxygen will gradually reduce the concentration of carbon dioxide, air pollution, increase become up.
科学家称，上周晚些时候空气中的一氧化碳含量已经高达安全值的六倍，其它有毒物质则使空气更加污浊。
Scientists say levels of carbon monoxide peaked at six times the acceptable norm late last week and other toxic particles have clogged the city's air.
科学家称，上周晚些时候空气中的一氧化碳含量已经高达安全值的六倍，其它有毒物质则使空气更加污浊。
Scientists say levels of carbon monoxide peaked at six times the acceptable norm late last week and other toxic particles have clogged the city's air.
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