Influencing factors of element leaching of compressed gravel in Ningxia

Abstract: Studying the elemental leaching of gravel in the sand soil is very important for the maintenance and healthy development of the soil in Xiangshan area，Zhongwei，Ningxia province. The test site was located in Xiangshan Township, Zhongwei, Ningxia province (36ｏ06′N and 105ｏ15′E). In order to study the rule of elemental leaching of sand land under different water supply, salt treatment and temperature, the elements contents of 2 kinds of gravels were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). In the experiment, 2 kinds of sand gravels were studied in Zhongwei, Ningxia grey green deep gray slate, and gray red thick coarse-grained quartz feldspar sandstone. Leaching test was in a semi-closed automated simulation operation room of 5 m×1.2 m×2.5 m. According to the recent 30-year meteorological data at the weather station in Xiangshan District, Zhongweiand meteorological temperature and water quality data, the effects of water, salinity and temperature on elemental leaching of gravel were studied. Based on the annual precipitation, through P-III curve fitting results, the 3 level years of high water year (20%), flat water year (50%) and low water year (80%) are determined, and the three kinds of hydraulic typical years of high water year, flat water year and low water year were selected in 2007, 1988 and 1986 respectively, and the monthly precipitation of each typical year was used to control the water replenishment in simulation experiments. According to the research data of the water melon irrigation system in Xiangshan District of Ningxia and the nearby area combined with the local irrigation habits, 3 levels of adequate irrigation, 75% full irrigation and inadequate irrigation were set up, with a total of 6 experimental levels, 3 replicates at each level. The contribution rate of each influencing factor to elemental leaching was analyzed by multiple regression method. The results showed that: 1 ) With the increase of water replenishment, the leaching amount of elements in green slate fluctuated and increased. The leaching amount of elements Na, Si and Cl in red sandstone increased with the increase of water replenishment. The leaching amount of elements Mn and Ba peaked at 397 mL of water replenishment, and then decreased. The reason was that the leaching solution was diluted with the further increase of water supply, so the leaching solution tended to decrease. The fitting equation showed that the gravel leaching amount of elements had a logarithmic function with the amount of water replenishment, and the fitting degree was high (R2 higher than 0.99). 2 ) With the increase of salinity, the amount of element leaching increased first and then decreased, and reached the maximum under NaCl solution treatment when salinity was about 3 g/L, then decreased gradually. Through fitting equation, we found that the leaching amount of elements in gravel had a quadratic polynomial relationship with salinity. 3 ) Among the influence factors of element leaching amount in the Zhongwei area, the amount of water supplement had the greatest influence on the leaching amount of elements, followed by the lowest temperature and the lowest salinity. In Zhongwei area, the influence of leaching amount of elements in gravel was the highest by water supply, followed by temperature and salinity. The research can provide valuable information for healthy development and sustainable utilization of sandy soil.