Occurrence of herbicides and antibacterial agents in surface water and sediment around Baihe reservoir

  • 曹 書涵

Student thesis: Doctoral Thesis

Abstract

Nowadays the occurrence of emerging contaminants is greatly influenced and released by human activity Due to the development of advanced analytical instruments the detection of trace contaminants in water samples has become easier through proper pretreatments This study aimed to investigate the occurrence of emerging contaminants in Baihe reservoir related to agricultural activities and hot-spring tourism Based on the potential pollution sources in this area several herbicides (glyphosate aminomethylphosphonic acid (AMPA) and glufosinate) and antibacterial agents (triclosan and triclocarban) were monitored to investigate whether reservoir water quality is influenced by human activities In addition to the water in the adjacent aquatic system the contaminants in solid phase was also traced so that we can fully understand their residue levels in the sampling area The water samples were collected during Dec 2018 to Apr 2020 for 12 times and the mud samples were collected during Sep 2019 to Apr 2020 for 7 times respectively In our results the detected concentration and frequency of herbicides in 135 water samples (glyphosate: 0 11±0 79 μg/L 10% AMPA: 0 17±0 51 μg/L 35% glufosinate: 0 004±0 024 μg/L 5%) indicates that glyphosate and its metabolite AMPA seem to be more common than glufosinate By contrast antibacterial agents (sample number n=126) existed in sub-ppt levels but the frequency of occurrence was relatively high (triclosan: 3 97±13 41 ng/L 47 6% triclocarban: 0 86±1 83 ng/L 47 2%) which may be resulted from their photodegradable properties and application in daily based detergents or personal care products In hot weather season as shown by the seasonal pattern the concentration and detection frequency of herbicides are higher (glyphosate: 0 19±1 10 μg/L 11%; AMPA: 0 25±0 66 μg/L 37%; glufosinate: 0 01±0 03 μg/L 4%) which corresponds to the weed control program On the contrary due to the peak tourist season in the hot spring tourism more antibacterial agents are detected in cold weather season (TCS: 7 0±19 7 ng/L 58 2%; TCC: 1 1±2 0 ng/L 58 2%) Therefore this trend can be used to select an appropriate time to monitor different contaminants in Baihe reservoir catchment Furthermore to discuss the contaminants contribution from 3 tributaries of Baisui River (Wen Quan Keng Creek You Zitou Creek and Guan Zilling Drainage) herbicides had been detected with higher level in Guan Zilling Drainage during whole sampling period; antibacterial agents had been detected with more concentration in Wen Quan Keng Creek in cold weather season and in both Wen Quan Keng Creek and Guan Zilling Drainage in hot weather season Regarding the accumulation in the solid phase the adsorption of herbicides and antibacterial agents is also discussed Because there was very little sediment in the upstream area only two locations with mud samples were collected The carbon content of hot-spring mud samples (n=13) in two sampling sites were 0 23±0 13% and 0 82±0 47% The percentage of triclosan and triclocarban detected at the hotel sampling sites was 100% and the average cumulative concentration of all mud samples were 4 98±5 63 μg/kg (Triclosan) and 2 06±2 57 μg/kg (Triclocarban) respectively In contrast to common residue of antibacterial agents AMPA and glufosinate were only detected one time in mud samples with average concentration 0 93±3 37 μg/kg and 0 90±3 25 μg/kg No occurrence of glyphosate in mud samples The calculated organic carbon adsorption coefficient (log Koc) values of triclosan and triclocarban were 5 31±0 26 and 5 63±0 65 indicating their strong adsorption tendency on the solid phase Our results showed that antibacterial agents seem to be more likely to remain on solid phase than herbicides and the main pollution source in the surrounding environment (such as hotel wastewater) may lead to higher accumulative levels of triclosan and triclocarban
Date of Award2020
Original languageEnglish
SupervisorWan-Ru Chen (Supervisor)

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