Deciphering the linkage between dissolved biochar and nitrate reduction in the saturated zone and the associated shifts in microbial communities

¹ Key Laboratory of Marine Environment and Ecology, Ministry of Education of China, Ocean University of China, Qingdao, 266100, China.
² Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
³ College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China

^b* Corresponding author’s email: liulecheng@ouc.edu.cn; arangod0125@163.com;

Abstract

This study delves into the impact of Dissolved Biochar (DBC) on nitrate reduction in the saturated zone, a key process for mitigating groundwater nitrate contamination from agricultural runoff. Through batch experiments, we evaluated the influence of DBC, derived from pyrolyzed corn stalks and pine sawdust, on nitrate reduction rates and microbial community dynamics. The addition of DBC resulted in a significant reduction in NO --N levels, with a 46%-48% decrease observed within six days, surpassing the 25% reduction in the control group. This effect was particularly notable under different C/N ratios, simulating the impact of agricultural activities on soil carbon to nitrogen ratios. Denitrification rates were substantially higher in DBC- treated samples, increasing by 1.9 to 2.3 times compared to the control, with the most significant enhancement observed under higher C/N conditions. Microbial community analysis revealed an increase in denitrifying bacteria in the presence of DBC, indicating its role in shaping the microbial ecology for nitrate transformation. The results highlight the potential of DBC in enhancing nitrate reduction and its implications for groundwater pollution control, presenting an environmentally friendly strategy to manage nitrate loads in agricultural settings.