Water-soluble organic carbon (WSOC) from vegetation fire and its differences from WSOC in natural media: Spectral comparison and self-organizing maps (SOM) classification

Huiying Zhang; Jinzhi Ni; Ran Wei; Weifeng Chen

doi:10.1016/j.scitotenv.2023.165180

Water-soluble organic carbon (WSOC) from vegetation fire and its differences from WSOC in natural media: Spectral comparison and self-organizing maps (SOM) classification

Sci Total Environ. 2023 Oct 15:895:165180. doi: 10.1016/j.scitotenv.2023.165180. Epub 2023 Jun 27.

Authors

Huiying Zhang¹, Jinzhi Ni¹, Ran Wei¹, Weifeng Chen²

Affiliations

¹ Key Laboratory for Humid Subtropical Eco-geographical Processes of the Ministry of Education, Fujian Normal University, Fuzhou, Fujian 350007, China; Fujian Provincial Key Laboratory for Plant Eco-physiology, Fujian Normal University, Fuzhou, Fujian 350007, China; School of Geographical Sciences, Fujian Normal University, Fuzhou, Fujian 350007, China.
² Key Laboratory for Humid Subtropical Eco-geographical Processes of the Ministry of Education, Fujian Normal University, Fuzhou, Fujian 350007, China; Fujian Provincial Key Laboratory for Plant Eco-physiology, Fujian Normal University, Fuzhou, Fujian 350007, China; School of Geographical Sciences, Fujian Normal University, Fuzhou, Fujian 350007, China. Electronic address: CWF_geo@fjnu.edu.cn.

PMID: 37385508
DOI: 10.1016/j.scitotenv.2023.165180

Abstract

Vegetation fire frequently occurs globally and produces two types of water-soluble organic carbon (WSOC) including black carbon WSOC (BC-WSOC) and smoke-WSOC, they will eventually enter the surface environment (soil and water) and participate in the eco-environmental processes on the earth surface. Exploring the unique features of BC-WSOC and smoke-WSOC is critical and fundamental for understanding their eco-environmental effects. Presently, their differences from the natural WSOC of soil and water remain unknown. This study produced various BC-WSOC and smoke-WSOC by simulating vegetation fire and used UV-vis, fluorescent EEM-PARAFAC, and fluorescent EEM-SOM to analyze their different features from natural WSOC of soil and water. The results showed that the maximum yield of smoke-WSOC reached about 6600 folds that of BC-WSOC after a vegetation fire event. The increasing burning temperature decreased the yield, molecular weight, polarity, and protein-like matters abundance of BC-WSOC and increased the aromaticity of BC-WSOC, but presented a negligible effect on the features of smoke-WSOC. Furthermore, compared with natural WSOC, BC-WSOC had a greater aromaticity, smaller molecular weight, and more humic-like matters, while smoke-WSOC had a lower aromaticity, smaller molecular size, higher polarity, and more protein-like matters. EEM-SOM analysis indicated that the ratio between the fluorescence intensity at Ex/Em: 275 nm/320 nm and the sum fluorescence intensity at Ex/Em: 275 nm/412 nm and Ex/Em: 310 nm/420 nm could effectively differentiate WSOC of different sources, following the order of smoke-WSOC (0.64-11.38) > water-WSOC and soil-WSOC (0.06-0.76) > BC-WSOC (0.0016-0.04). Hence, BC-WSOC and smoke-WSOC possibly directly alter the quantity, properties, and organic compositions of WSOC in soil and water. Owing to smoke-WSOC having far greater yield and bigger difference from natural WSOC than BC-WSOC, the eco-environmental effect of smoke-WSOC deposition should be given more attention after a vegetation fire.

Keywords: Burning temperature; Smoke; Spectral features; Vegetation fire; Water-soluble organic carbon.