Sediment organic matter description from an urban wetland: multivariate analysis of FT-IR bands to determine its origin

ABSTRACT

Urban water bodies have the potential to be polluted in many ways. Organic matter can become a pollutant or in other ways hinder the health of water columns. Sediments can become the sink of the organic matter and dictate the dynamics in the water column. Accordingly, an adequate knowledge of the chemical and structural characteristics of organic matter in sediments is necessary if the pollution of water bodies is to be understood and the correct measures are to be implemented. In this study of sediments from three contrasting sites, organic matter was extracted with hexane and chloroform for non-humic substances, and sodium hydroxide and sodium pyrophosphate for humic substances, and then analysed with chemical and spectroscopic methods. The FT-IR spectra obtained were further evaluated by principal component analysis. The results showed that the chloroform extract can better differentiate the source of the organic material with the help of the phosphate groups; fulvic acids extracted by sodium pyrophosphate could better differentiate the humic substances of the studied areas. The site in an agricultural area had a clear contribution from run-off and aquatic plant decomposition, while the area near a wastewater outlet showed the influence of secondary effluents from water treatment plants. The urban area had organic matter contributed from aquatic plant decomposition and long-chain fatty acids of urban origin.

KEYWORDS:

• Organic matter
• sediments
• FT-IR
• humic substances
• Xochimilco

Acknowledgments

We thank M.Sc. Antonio Calzada Villafuerte (Facultad de Ciencias, UNAM) for his valuable support in the preparation of the figures.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the UNAM-PAPIIT [IN223618].