Identification of pollution sources in rivers by downstream analysis of low-concentration elements associated with wastewater

Accurate estimation of pollution sources of industrial wastewater, which is detrimental to the environment and human health, facilitates river quality management. In this study wastewater-specific elements in downstream river water were used to trace back to pollution origin by upstream industry categories. In addition, a sensitivity test is performed on lanthanides to determine the importance of low-concentration elements in the analysis. Over a period of 45 days, water samples are obtained twice daily from a polluted river in southern Taiwan near industrial areas. During the monitoring period, wastewater samples from potential contamination sources are conducted to establish the source profiles. Positive matrix factorization is used to determine the pollution sources from the 31 elements measured in the stream. The results show that heavy metal pollution is primarily caused by wafers and semiconductors (47%), sewage treatment (27%), and electroplating products (12%). The sensitivity test results for lanthanides show that excluding some or all of them renders it impossible to classify pollution sources into the correct industry categories. Because lanthanides are key elements in certain industry categories, they are distinguishing factors in profiles among industries. Therefore, the source profiles of low-concentration lanthanides can aid in identifying pollution sources.