Process water from hydrothermal carbonization: The impacts on the aquatic dissolved organic matter feature and microbial network at the soil-water interface

This study aimed to explore the effects of process water generated by hydrothermal carbonization (HTC-PW) at 180 degrees C and 260 degrees C on the soil-water environment. The input of HTC-PW changed the aquatic DOM components, such as the C1-C3 component decreased by 51.92-100%, and the C4 component increased by 81.40-100%. HTC-PW promoted the development of Proteobacteria and Firmicutes with relative abundance ratios of 1.75-2.31 and 1.4-3.25 times higher than CK, with a positive association revealed with the carbon conversion indicators. Furthermore, Proteobacteria play a critical role in bacterial networks exposed to high-temperature HTC-PW due to the facilitated nutrient exchange and metabolite. The prevalence of Ciliophora and Chlorophyta positively correlated with the nutrient compounds of HTC-PW. Moreover, the higher percentage of positive correlation in fungal networks was 75.26%, which implicated that microbial cooperation of fungi was more pronounced on an equal footing exposed to low-temperature HTC-PW. This study provides a theoretical basis for analyzing the potential ecological effects of HTC-PW in the soil-water environment associated with HTC applications, intending to provide parameters and guidance for the rational disposal of HTC-PW.