Full
Outline
There is the potential for nitrate contamination in the northern karst area. Systematically investigating the spatiotemporal pattern of surface water nitrate and the sources of pollution is extremely important for the timely recognition of the pollution hazard and the accurate location of the sources of pollution. Based on the representative watershed in the northern karst area, the Wuhushan Reservoir Basin, this study carried out evenly distributed sampling on the three main rivers of Jinyangchuan, Jinyunchuan, and Jinxiuchuan. A total of 54surface water samples from 18points along the major streams and primary tributaries were collected in the dry season, normal season, and wet season. By combining hydrochemical analysis, redundancy analysis (RDA), nitrogen and oxygen isotope methods, and the Bayesian isotope mixing model (SIAR), the study outlined the spatiotemporal pattern characteristics of nitrate in the basin's intricately interconnected surface water system and quantitatively estimated the contribution rates of different sources of pollution. The results showed that: ① The hydrochemical conditions in the research area were favorable for nitrification, with low ammonium and nitrite nitrogen contents persistently throughout the three seasons. Average nitrate contents in the dry season were greater than the normal season and wet season. Nitrate contents remained low in the upper reaches of Jinxiuchuan throughout the periods, while the downstream segments (S7-S9) had much higher nitrate contents in the dry season and normal season. Spatial differences in nitrate contents in the wet season narrowed, with relatively high contents at stations X2 and X3 in Jinyangchuan, Y2 and Y3 in Jinyunchuan. ② During the entire course of the three seasonal periods, assimilation and denitrification did not play a dominant role in the nitrate transport and transformation process, with the prevalence of nitrification. ③ During the wet season, nitrate in surface water in the study area came mainly from non-point source pollution, of which soil organic nitrogen was 62.81%. Pollution sources in the normal season were richer in composition, with soil and manure/sanitary sewerage supplying 48.85% and 21.96%, respectively. Sewage from household discharge was the major source in the dry season, which contributed to the surface water nitrate to the extent of 68.03%. These discoveries provide scientific support for the prevention of nitrate pollution and environmental protection of surface water in the northern karst area in China.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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