Reinforced Bioremediation of Excessive Nitrate in Atrazine-Contaminated Soil by Biodegradable Composite Carbon Source

Abstract

Bioremediation is a good alternative to dispose of the excessive nitrate (NO3−) in soil and alleviate the secondary salinization of soil, but the presence of atrazine in soil interferes with the bioremediation process. In the present study, the biodegradable composite carbon source with different dosages was added to the atrazine-contaminated soil to intensify the bioremediation of excessive NO3−. The atrazine-contaminated soil with a 25 g/kg composite carbon source achieved the optimal NO3− removal performance (92.10%), which was slightly higher than that with a 5 g/kg composite carbon source (86.15%) (p > 0.05). Unfortunately, the negative effects of the former were observed, such as the distinctly higher emissions of N2O, CO2 and a more powerful global warming potential (GWP). Microbial community analysis showed that the usage of the composite carbon source clearly decreased the richness and diversity of the microbial community, and greatly stimulated nitrogen metabolism and atrazine degradation (p < 0.05). To sum up, the application of a 5 g/kg composite carbon source contributed to guaranteeing bioremediation performance and reducing adverse environmental impacts at the same time.

The Microbiome and Antibiotic Resistome in Soil under Biodegradable Composite Carbon Source Amendment

“…The relative abundance of nitrogen transport, dissimilatory nitrate reduction to ammonium, assimilatory nitrate reduction, nitrification and nitrogen fixation was relatively low (<8%). It is notable that almost all nitrogen transport, dissimilatory nitrate reduction to ammonium, assimilatory nitrate reduction and nitrogen fixation functional genes acquired higher relative abundance in C5 and C25 than C0, which contributed to the accumulation of ammonia and corresponded to the results of our previous study [7].…”

“…All of the serum bottles were placed in an incubator (GXZ-436, Ningbo Jiangnan Instrument Factory, Ningbo, China) at 25 °C in the dark. A destructive sampling strategy was performed on the 42nd day [ 7 ].…”

“…To accelerate microbial growth and reinforce bioremediation, some specific substrates are supplemented to serve as electron donors, nutrients and pH buffers [ 4 ]. In our previous study, the application of a composite carbon source (<2 mm), made of pretreated corncob and biodegradable polybutylene succinate, successfully strengthened the bioremediation performance of excessive nitrate in soil under atrazine stress [ 7 ]. However, limited information was available about the effects of a composite carbon source on microbial community diversity, nitrogen removal pathways, and the potential risks on the environment.…”