Bacterial diversity and community structure in nitrate-contaminated shallow groundwater in the Poyang Lake basin, China

¹ State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, 330013 Nanchang, China
² School of Water Resources and Environmental Engineering, East China University of Technology, 330013 Nanchang, China
³ Research and Education Centre “Water”, National Research Tomsk Polytechnic University, 634050 Tomsk, Russia

^* Corresponding author: zhxsun@ecit.cn

Abstract

The Poyang Lake basin in the Jiangxi province of China has been exposed to nitrate pollution caused by irrigation practices, leading to high groundwater nitrate concentration. Eight groundwater samples were collected from shallow wells for hydrochemical, bacterial diversity, and community structure analysis in November 2017. Shallow groundwaters of the basin are weakly acid and in an oxidizing state, with EC ranging from 87.6 to 279.5 µS/cm and TDS varying between 53 to 344 mg/L and averaging of 164 mg/L. The NO₃-N form is the dominant nitrogen species in groundwater, with сoncentrations of NO₃-N, NO₂-N and NH₄-N ranging between 2.5 to 164 mg/L, 0.01 to 0.10 mg/L, <0.01 to 0.08 mg/L, respectively. Groundwater communities are dominated by actinobacteria, alphaproteobacterial, gammaproteobacteria and betaproteobacteria both in high- and low-nitrate groundwaters. The results of a 16S rRNA gene clone library indicate that the bacterial community structure of the high-nitrate groundwater is different from that of the low-nitrate groundwater. The bacterial populations Denitratisoma and Sulfuritalea detected in low-nitrate groundwater suggest that these bacteria are capable of denitrification in anaerobic groundwater environment. Bacterial populations Flavobacteria and Cytophagia in high-nitrate groundwater are common in the s wetlands examined and likely capable of nitrification.