增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

    Recently, the increasing of shared bikes have made our lives more convenient. However, my classmates and I often noticed some shared bikes place messily everywhere. We felt upset but decided to make a change to the uncivilized behavior. On Saturday morning, we gather outside the subway station. First, we began with those messy shared bikes and tried to put them in to order. People passing by appreciated that we did. Seen the bikes in rows on the pavement, we felt excited. Then, in order to encourage people's civilized behavior, we put up a largely poster saying “Please Be Civilized While Using A Shared Bike”. Of course, we drew much attention from the passer-by. Hopefully our actions will make difference.

PM2.5的沉降速度较慢，自然沉降效果有限，会长期漂浮在空中。2013年3月10日，成都市空气质量和能见度持续下降，至3月10日中午12时，全市各监测点可吸入颗粒物（PM10以下的颗粒物）浓度均已超过1000微克/立方米，致使空气质量重度污染，使成都成为全国最“霾头苦干”的城市。根据相关知识回答下题。
下列说法中不是主要造成成都市雾霾天气的原因是