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It is a new problem for the prevention and control of non-point source pollution to adsorb pollutants by colloids and assist them to quickly migrate from soil to water during the rainfall-runoff process. Southwest Guizhou Province is one of the important ecological barrier areas in the Pearl River Basin, but some areas sow corn in the middle and late April and enter the rainy season in May. The destruction of soil structure, the significant increase of precipitation and the typical karst landforms in the region lead to high water environmental risks in sloping farmland areas. Undisturbed soil samples are collected from newly ploughed yellow soil slope farmland in karst area. These samples undergo simulated rainfall infiltration experiments. The purpose is to investigate the dynamic release rule of colloids under different rainfall intensities, including the change characteristics of colloid concentration, particle size distribution and its content level with the increase of accumulated rainfall. The results show as follows. The colloid concentration increased with the increase of rainfall intensity and cumulative infiltration, and the study further revealed that the difference of released soil colloid concentration under three rainfall intensities showed three different stages: the colloid concentration is not significantly different when the rainfall intensity is 25 mm/h and 40 mm/h in the 0~100 mm stage, but is significantly higher than 10 mm/h. The colloid concentration in the 100~250 mm stage is quite different under three rainfall intensities. When the accumulated rainfall is more than 250 mm, the difference between them is very small. When the rainfall intensity is 40 mm/h, the characteristic statistics of colloidal particle size show obvious two-stage and sudden drop characteristics. At first, the average particle size of effluent increases with the increase of rainfall intensity, and then decreases slightly with the further increase of rainfall. When the rainfall intensity is 25 mm/h and 10 mm/h, it presents a gradual change characteristic. The change of colloid content with different particle sizes shows a trend of stability, increase and decrease respectively. The research innovatively reveals the stage characteristics of the outflow concentration difference of soil colloids at different flow rates, and quantifies the change trend of colloids with different particle sizes with the cumulative infiltration from the meso-scale, which will provide a reference for further evaluating the regional water environmental risk and driving mechanism in this period.
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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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