https://www.selleckchem.com/products/plerixafor.html Due to the vulnerability of karst hydrological systems, nitrate pollution in karst groundwater has become a global common and serious environmental problem. In order to ensure drinking water safety, it is very important to accurately identify groundwater nitrate sources. The groundwater hydrochemistry and δ15N-NO3- and δ18O-NO3- isotopes were analyzed in samples taken from a suburb of Chongqingthe Longfeng karst trough-valley, which is mainly affected by agricultural activities, and the Longche karst trough-valley, which is primarily affected by urbanization. The IsoSource model was then used to quantify the groundwater nitrate sources. The results showed that① The NO3- concentration in groundwater ranged from 19.31 mg·L-1 to 37.01 mg·L-1(mean of 28.21 mg·L-1) in the Longfeng karst trough-valley, and from 2.15 mg·L-1 to 27.69 mg·L-1(mean of 10.31 mg·L-1) in the Longche karst trough-valley. The groundwater NO3- concentration exhibited an obvious seasonal variation in both valleys. ② The δ15N-NO3- and δ18O-NO3-25% during the rainy season and dry season, respectively.The internal source pollution of sediment is the main factor leading to the repetition of black-odorous river channels. In order to prevent this situation, a river channel in the Binhu District of Wuxi City was used as an experimental site. In-situ CaO2 combined with a biochar covering technology was used to repair the black odorous river sediment in this channel. The effects of this technology on the quality of mud water, sedimentary volatile sulfide (AVS) and phosphorus forms, microorganisms, and restoration of black odorous sediment were investigated. The results showed that CaO2 combined with biochar coverage could significantly increase the dissolved oxygen (DO) concentration and redox potential (ORP) of the muddy water system. The DO concentration and ORP in the overlying water were maintained above 2 mg·L-1 and 50 mV, respectively. The removal rat