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River water quality sampling frequency is an important aspect of the river water quality monitoring network. A suitable sampling frequency for each station as well as for the whole network will provide a measure of the real water quality status for the water quality managers as well as the decision makers. The analytic hierarchy process (AHP) is an effective method for decision analysis and calculation of weighting factors based on multiple criteria to solve complicated problems. This study introduces a new procedure to design river water quality sampling frequency by applying the AHP. We introduce and combine weighting factors of variables with the relative weights of stations to select the sampling frequency for each station, monthly and yearly. The new procedure was applied for Jingmei and Xindian rivers, Taipei, Taiwan. The results showed that sampling frequency should be increased at high weighted stations while decreased at low weighted stations. In addition, a detailed monitoring plan for each station and each month could be scheduled from the output results. Finally, the study showed that the AHP is a suitable method to design a system for sampling frequency as it could combine multiple weights and multiple levels for stations and variables to calculate a final weight for stations, variables, and months.

This study investigated and evaluated the quality of PFASs in the water of the Bac Hung Hai River passing through Van Giang district, Hung Yen, Vietnam. PFASs concentration in the river water samples were detected by using LC-MS/MS spectrum. The results showed that the studied river region contaminated PFASs. PFASs concentration ranged from 0.10 to 3.88 ng/l. The average concentrations of individual PFASs were PFBA 5

Perfluorooctanoic acid (C7F15COOH, PFOA) is a persisted organic pollutant widely used in industry in recently. It is widespread occurrence in the environment and because of its ability to bioaccumulate. PFOA is reported toxic and carcinogenic to animals such as rats, fishes, monkeys, and even humans. Photodegradation PFOA solution in presence Na2SO4 was studied in this study. PFOA was photodegraded about 93% after 24 h by using a combination of UV 254nm irradiation and Na2SO4 30mM, while under only UV irradiation, 43% of PFOA was photodegraded. Na2SO4 30mM was the concentration that photodegradation PFOA reached highest efficiency. The optimal temperature for PFOA degradation is 25 o C.