分类： 地球科学 >> 大气科学 提交时间： 2019-06-20 合作期刊: 《干旱区科学》
摘要： As a main component in water balance, evapotranspiration (ET) is of great importance for water saving, especially in arid and semi-arid areas. In this study, the FAO (Food and Agriculture Organization) Penman-Monteith model was used to estimate the magnitude and temporal dynamics of reference evapotranspiration (ET0) in 2014 in subalpine meadows of the Qilian Mountains, Northwest China. Meanwhile, actual ET (ETc) was also investigated by the eddy covariance (EC) system. Results indicated that ETc estimated by the EC System was 583 mm, lower than ET0 (923 mm) estimated by the FAO Penman-Monteith model in 2014. Moreover, ET0 began to increase in March and reached the peak value in August and then declined in September, however, ETc began to increase from April and reached the peak value in July, and then declined in August. Total ETc and ET0 values during the growing season (from May to September) were 441 and 666 mm, respectively, which accounted for 75.73% of annual cumulative ETc and 72.34% of annual cumulative ET0, respectively. A crop coefficient (kc) was also estimated for calculating the ETc, and average value of kc during the growing season was 0.81 (ranging from 0.45 to 1.16). Air temperature (Ta), wind speed (u), net radiation (Rn) and soil temperature (Ts) at the depth of 5 cm and aboveground biomass were critical factors for affecting kc, furthermore, a daily empirical kc equation including these main driving factors was developed. Our result demonstrated that the ETc value estimated by the data of kc and ET0 was validated and consistent with the growing season data in 2015 and 2016.
分类： 地球科学 >> 地球化学 提交时间： 2018-07-05 合作期刊: 《干旱区科学》
摘要： Effects of sludge utilization on the mobility and phytoavailability of heavy metals in soil-plant systems have attracted broad attention in recent years. In this study, we analyzed the effects of municipal sludge compost (MSC) on the solubility and plant uptake of Cd, Ni, Cu, Zn and Pb in a soil-potato system to explore the mobility, potato plant uptake and enrichment of these five heavy metals in sierozem soils amended with MSC through a potato cultivation trial in Lanzhou University of China in 2014. Ridge regression analysis was conducted to investigate the phytoavailability of heavy metals in amended soils. Furthermore, CaCl2, CH3COONH4, CH3COOH, diethylene triamine pentacetic acid (DTPA) and ethylene diamine tetraacetic acid (EDTA) were used to extract the labile fraction of heavy metals from the amended soils. The results show that the MSC could not only improve the fertility but also increase the dissolved organic carbon (DOC) content of sierozem soils. The total concentrations and labile fraction proportions of heavy metals increase with increasing MSC percentage in sierozem soils. In amended soils, Cd has the highest solubility and mobility while Ni has the lowest solubility and mobility among the five heavy metals. The MSC increases the concentrations of heavy metals in the root, stem, peel and tuber of the potato plant, with the concentrations being much higher in the stem and root than in the peel and tuber. Among the five heavy metals, the bioconcentration factor value of Cd is the highest, while that of Ni is the lowest. The complexing agent (DTPA and EDTA) extractable fractions of heavy metals are the highest in terms of phytoavailability. Soil properties (including organic matter, pH and DOC) have important impacts on the phytoavailability of heavy metals. Our results suggest that in soil-potato systems, although the MSC may improve soil fertility, it can also increase the risk of soils exposed to heavy metals.
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