Recognizing the groundwater related to chronic kidney disease of unknown etiology by humic-like organic matter

Chronic kidney disease of unknown etiology (CKDu) becomes a health concern in developing countries. It is urgent to recognize CKDu-related groundwater in CKDu-prevalent areas. Here, spectral indices showed that DOM from CKDu groundwater was characterized by higher molecular weight, stronger exogenous feature, and greater degree of humification and unsaturation than from non-CKDu groundwater. Parallel factor analysis of fluorescence spectra showed that DOM from CKDu groundwater contained significantly more humic-like substances (C1%) and less protein-like substances than from non-CKDu groundwater. Furthermore, C1% was correlated with concentrations of inorganic chemicals associated with CKDu, indicating the feasibility of using C1% for probing CKDu groundwater. According to our self-developed method, both the non-CKDu probability of groundwater with C1% less than the recognizing threshold (RT, 28.8%) and the CKDu probability of groundwater with C1% larger than RT are 70.1%. This indicates that the C1%-based method is a feasible tool for recognizing CKDu groundwater.