长江重庆段干支流中PPCPs的时空分布特征、来源及生态风险

Temporal and spatial distribution characteristics, sources and ecological risks of PPCPs in the main stream and tributaries of Yangtze River of Chongqing section

关键词:  药物和个人护理品  长江  时空分布特征  生态风险评价

Key words:  pharmaceuticals and personal care products  Yangtze River  temporal and spatial distribution characteristics  ecological risk assessment

摘要:

长江重庆段地处我国西南部，是长江经济带上游的核心区域，为探究水环境中药物和个人护理品 （PPCPs）的分布特征与生态风险，该研究分别采集丰水期和枯水期长江重庆段干支流上27个点位的表层水样品，采用在线固相萃取-超高效液相色谱-三重四极杆质谱仪对水样中 8 种 PPCPs 进行检测，探讨 PPCPs的时空分布特征及来源，并采用风险熵法评价其生态风险。结果表明，丰水期可待因 （CDI） 和避蚊胺 （DEET） 检出率＞50%，枯水期罗红霉素 （ROX） 和DEET检出率＞50%。DEET和CDI是检出的主要污染物，丰水期DEET平均浓度为80.8 ng/L，枯水期CDI平均浓度为69.4 ng/L。支流圣水河和临江河表层水中PPCPs的浓度在枯水期较高，长江重庆段干流表层水中PPCPs的浓度在丰水期较高。长江重庆段干支流表层水中PPCPs浓度为临江河＞长江干流＞圣水河。PPCPs可能源于未经处理的生活污水、污水处理厂排水和养殖废水等。生态风险评价结果显示干支流中PPCPs风险总体较低；支流临江河下游区域部分采样点位在枯水期CDI、MIC和ROX污染存在中等风险。

Abstract:

Background, aim, and scope Pharmaceuticals and personal care products (PPCPs) represent a class of emerging contaminants that have been increasingly used in industrial production and daily life amid rapid economic growth and rising living standards, leading to their widespread occurrence in aquatic environments. Prolonged presence of PPCPs may impair the growth and reproduction of aquatic organisms and induce the development of drug resistance in environmental microbes. While PPCPs have been frequently detected in the mainstream of the Yangtze River Basin and large lake reservoirs, existing studies have mostly focused on the Yangtze mainstream, Jialing River, Dongting Lake, and the Yangtze River Delta, with scarce data available on relatively small tributaries such as the Shengshui River and Linjiang River. To comprehensively clarify the PPCP pollution status in surface waters of the main stream and tributaries of the Yangtze River in Chongqing, this study targeted the Shengshui River and Linjiang River, selected 8 typical PPCPs with high consumption and widespread social concern as the target compounds via systematic investigation, and aimed to elucidate their temporal and spatial distribution characteristics, identify potential pollution sources, and assess their ecological risks. This research is expected to provide essential data support for ecological risk identification and the formulation of regional PPCP prevention and control strategies in this area. Materials and methods Surface water samples were collected at 27 sampling sites across the main stream and tributaries of the Yangtze River in Chongqing in early August 2022 (wet season) and early March 2023 (dry season). The target PPCPs in the samples were analyzed using an online solid-phase extraction coupled with ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (online SPE-UPLC-MS/MS) system. The risk quotient (RQ) method was employed to evaluate the ecological risks of the detected PPCPs. Results Temporally, five PPCPs (propranolol (PR), bezafibrate (BZB), clindamycin (CLI), codeine (CDI), and diethyltoluamide (DEET)) were detected in the dry season, where as all 8 target PPCPs (PR, BZB, CLI, ROX (roxithromycin), CDI, IND (indomethacin), DEET and MIC (miconazole)) were detected in the wet season. The detection rates of CDI and DEET exceeded 50% in the wet season, while those of ROX and DEET were over 50% in the dry season. The macrolide antibiotics CLI and ROX had detection rates of 42% and 54% in the dry season, respectively, but were nearly undetectable in the wet season. PR, a commonly used β-blocker for hypertension, had detection rates of 4% and 29% in the wet and dry seasons, respectively, and CDI, an analgesic and anti-inflammatory drug, had detection rates of 63% and 38% in the wet and dry seasons, respectively. BZB (a lipid-lowering drug), IND (an analgesic and anti-inflammatory drug), and MIC (a disinfectant) exhibited low detection rates of less than 10% across both seasons. DEET and CDI were identified as the primary pollutants, with the average concentration of DEET reaching 80.8 ng/L in the wet season and that of CDI hitting 69.4 ng/L in the dry season. Spatially, the Linjiang River had the highest total PPCP concentrations, followed by the Yangtze mainstream, while the Shengshui River had the lowest. Overall, the ecological risks posed by the target PPCPs in the study area were relatively low. Discussion As a core economic development zone in the upper Yangtze River, Chongqing has seen PPCPs from agricultural cultivation, livestock and poultry breeding, and domestic sewage discharge enter the aquatic environment with its rapid economic growth. All target PPCPs were detected to varying degrees in this study, and a comparison with domestic and international surface water data showed that most PPCP concentrations in the study area were at low levels, with DEET, ROX, and CDI at moderate levels. The temporal and spatial distribution of PPCPs was found to be associated with multiple factors, including human activity patterns, hydrological conditions, and climatic factors. PPCP concentrations in surface water were diluted by high water discharge and concentrated by low water volume; temperature also affected microbial activity and thus PPCP degradation, with higher temperatures potentially reducing PPCP concentrations. Seasonal fluctuations in human demand for PPCPs also led to distinct seasonal variations in their distribution. Correlation analysis revealed a significant relationship (P≤0.05) between water temperature (WT), pH, electrical conductivity (EC), dissolved oxygen (DO), and PPCP concentrations. Land use type analysis suggested that PPCPs in the study area primarily originated from agricultural activities and domestic sewage. Conclusions PPCPs were detected to varying degrees in both the wet and dry seasons, with the insect repellent DEET and the analgesic and anti-inflammatory drug CDI being the most prevalent pollutants. The total PPCP concentrations in the Shengshui River and Linjiang River were higher in the dry season, while those in the Yangtze River (Chongqing section) mainstream were higher in the wet season. The average total PPCP concentration in surface waters followed the order: Linjiang River＞Yangtze mainstream＞Shengshui River. PPCP concentrations and distributions were influenced by aquatic environmental conditions, and the pollutants in the study area were primarily derived from agricultural non-point source pollution, untreated domestic sewage, and effluents from sewage treatment plants. Notably, moderate ecological risks from CDI, MIC, and ROX were observed at certain sampling sites in the lower reaches of the Linjiang River during the dry season. Recommendations and perspectives CDI, MIC, and ROX were identified as the priority PPCPs of concern in the surface waters of the Yangtze River tributaries in Chongqing. Enhanced routine risk monitoring is recommended, particularly for the lower reaches of the tributaries during the dry season, to mitigate potential ecological risks posed by these contaminants.