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Apatite ore mining and processing is one of the main mineral activities of Lao Cai province. According to the annual environmental monitoring results, most of the rivers and streams flowing through apatite mining and processing areas such as: O, Ngoi Dum, Ngoi Duong, Dong Ho and Coc streams are all polluted by content of COD, BOD5, TSS, N?2−, N?4+,  N?3−. The concentration of parameters as COD, BOD5, N?3−, N?2−, N?4+,   tends to increase over the years. Streams near the mining areas such as Ngoi Duong, Dong Ho, Chu O, Coc streams were mainly polluted by COD, BOD5, TSS, N?3−. Streams in the ore processing area at Tang Loong such as Trat, Cam Duong, Khe Chom streams,... were mainly polluted by N?4+, NO2- and some heavy metals like as Cu, Fe. The results of cluster analysis showed that basically the quality of stream water in the ore mining and processing area is divided into 4 groups: heavy pollution, medium pollution, light pollution and no pollution. In particular, heavy polluted streams flow through apatite mining areas such as Ngoi Duong, Ngoi Dum and Chu O. The results of PCA show changes in the distribution of environmental quality parameters in major components by years.In particular, the parameters that contain high information values include  COD, BOD5¸ N?3−, N?2− , Cu and Fe. The source of pollution is related to domestic wastewater at apatite mining and processing areas.

Temporal-spatial variation of surface water affected by apatite mining activity in Lao Cai, Viet Nam