Caffeine as a chemical tracer for contamination of urban rivers

ABSTRACT The growing urbanization in urban centers have continuously contributed to the deterioration of water quality in rivers. The use of caffeine as a chemical tracer for anthropic activities is an approach to the environmental monitoring of urban waterbodies, as its use is limited to humans and less susceptible to sampling error comparing to other traditional parameters for anthropic pollution. To analyze the possibility of using caffeine as a water quality parameter, the anthropic influence over three watersheds (Atuba, Belem and Palmital) from the Greater Curitiba was observed over five sampling campaigns. The caffeine was analyzed by liquid chromatography tandem diode array detection, after the solid phase extraction. Traditional parameters of water quality monitoring, such as ammoniacal nitrogen, thermotolerant coliforms, biochemical oxygen demand and orthophosphate, were measured for comparison. The results indicate anthropic influence over the basins, probably due to the lack of infrastructure, thus leading to the assumption of untreated domestic wastewater being discharged. The most degraded river was the Belem river (caffeine concentration of 23.08 µg.L-1). Caffeine presented itself as an appropriate approach for environmental monitoring, presenting a good correlation with the traditional parameters, such as for thermotolerant coliforms (R = 0.7375).

摘要
城市中心日益加剧的城市化进程持续加剧了内河水质的恶化。将咖啡因作为人为活动的化学示踪剂，是开展城市水体环境监测的有效路径：咖啡因的代谢仅与人类活动相关，且相较于其他传统人为污染监测参数，其受采样误差的影响更小。为分析将咖啡因作为水质监测参数的可行性，研究团队针对大库里蒂巴都会区的三个流域（阿图巴（Atuba）、贝伦（Belem）与帕尔米塔尔（Palmital））开展了五次采样监测。样品经固相萃取（solid phase extraction）后，采用液相色谱串联二极管阵列检测法（liquid chromatography tandem diode array detection）对咖啡因进行定量分析。同时测定了氨氮、耐热大肠菌群、生化需氧量与正磷酸盐等传统水质监测参数以作对照。研究结果表明，上述流域均受到人为活动影响，这大概率源于基础设施建设的缺失，由此可推测存在未经处理的生活污水直排现象。其中污染程度最高的河流为贝伦河，其咖啡因浓度达23.08 µg·L⁻¹。咖啡因可作为适用于环境监测的有效指标，且与耐热大肠菌群等传统水质参数呈现出良好的相关性（相关系数R=0.7375）。