Part of the increase stems from human activities—directly, in the case of construction, or indirectly, when it results from clearing vegetation from marginal land in order to farm it.

尘埃量的增加一部分原因源于人类活动——比如，建筑，它属于直接原因，又如，为了耕种而将边际地块上的植物清除所造成的后果就属于间接原因。

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Part of the increase stems from human activities-directly, in the case of construction, or indirectly, when it results from clearing vegetation from marginal land in order to farm it.

部分原因是人类活动- - -例如建筑施工这样的直接原因，或者是为了开垦贫瘠土地而清理植被这样的间接原因。

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