British Geological Survey, Maclean Building, Wallingford, OX10 8BB, UK.
Connected Waters Initiative Research Centre, UNSW Australia, Sydney, New South Wales 2052, Australia.
Sci Total Environ. 2018 May 1;622-623:1250-1257. doi: 10.1016/j.scitotenv.2017.11.162. Epub 2017 Dec 13.
We assess the use of fluorescent dissolved organic matter at excitation-emission wavelengths of 280nm and 360nm, termed tryptophan-like fluorescence (TLF), as an indicator of faecally contaminated drinking water. A significant logistic regression model was developed using TLF as a predictor of thermotolerant coliforms (TTCs) using data from groundwater- and surface water-derived drinking water sources in India, Malawi, South Africa and Zambia. A TLF threshold of 1.3ppb dissolved tryptophan was selected to classify TTC contamination. Validation of the TLF threshold indicated a false-negative error rate of 15% and a false-positive error rate of 18%. The threshold was unsuccessful at classifying contaminated sources containing <10 TTC cfu per 100mL, which we consider the current limit of detection. If only sources above this limit were classified, the false-negative error rate was very low at 4%. TLF intensity was very strongly correlated with TTC concentration (ρ=0.80). A higher threshold of 6.9ppb dissolved tryptophan is proposed to indicate heavily contaminated sources (≥100 TTC cfu per 100mL). Current commercially available fluorimeters are easy-to-use, suitable for use online and in remote environments, require neither reagents nor consumables, and crucially provide an instantaneous reading. TLF measurements are not appreciably impaired by common intereferents, such as pH, turbidity and temperature, within typical natural ranges. The technology is a viable option for the real-time screening of faecally contaminated drinking water globally.
我们评估了在 280nm 和 360nm 激发-发射波长下使用荧光溶解有机物，即色氨酸样荧光（TLF），作为粪便污染饮用水的指示剂。利用来自印度、马拉维、南非和赞比亚的地下水和地表水饮用水源的数据，建立了一个使用 TLF 作为预测指标的耐热大肠菌群（TTC）的显著逻辑回归模型。选择 1.3ppb 溶解色氨酸作为 TLF 阈值来分类 TTC 污染。对 TLF 阈值的验证表明，假阴性错误率为 15%，假阳性错误率为 18%。该阈值无法对含有<10 TTC cfu/100mL 的污染水源进行分类，我们认为这是当前的检测限。如果仅对超过此限制的水源进行分类，则假阴性错误率非常低，为 4%。TLF 强度与 TTC 浓度呈很强的相关性（ρ=0.80）。建议使用更高的 6.9ppb 溶解色氨酸阈值来指示污染严重的水源（≥100 TTC cfu/100mL）。目前市售的荧光计易于使用，适合在线和远程环境使用，既不需要试剂也不需要消耗品，并且至关重要的是可以提供即时读数。在典型的自然范围内，TLF 测量不会受到常见干扰物（如 pH 值、浊度和温度）的显著影响。该技术是在全球范围内实时筛查粪便污染饮用水的可行选择。
