Agricultural irrigation water in Northwest China accounts for more than 80% of total local water consumption, which is 1.23 times that of China. However, Northwest China is the most water-scarce place in China. Water scarcity in restricts crop growth and production. Reference crop evapotranspiration (ET0) is important for agricultural water management. Understanding the reason for ET0 change is helpful to provide a basis for rational planning of agricultural irrigation systems to conserve water. This study investigated the temporal and spatial variation characteristics of ET0 at 181 meteorological stations in Northwest China from 2000 to 2019. And the sensitive factors and dominant factors affecting ET0 change were quantitatively identified based on sensitivity analysis and contribution rate evaluation. Results showed that (1) a significant increase in maximum and minimum temperature (Tmax and Tmin), a significant decrease in sunshine duration (SD) and relative humidity (RH), and a slight increase in wind speed at 10 m height (U10) were observed. (2) Annual ET0 had an insignificant increasing trend. Spring and autumn ET0 contributed greatly to the growth of annual ET0, especially in March, May, September, October, and November. ET0 in HH (Yellow River Basin area) had decreased at annual scale, while other subregions were the opposite trend. Significant differences in monthly and seasonal changes in the spatial distribution of ET0. (3) U10 was the dominating contribution factor related to annual ET0 variability, followed by Tmin, RH, Tmax, and SD. In seasonal time scale, Tmin, SD, U10, and RH were the most dominant factors in spring, summer, autumn, and winter respectively. (4) Spatial distribution for contribution rates of various meteorological factors showed significant diversity among various subregions. The positive contribution of U10 was the major cause of the increase in ET0 in semi-arid grassland area (BGH), the southwest of “Qice line” (QCXXN), and the southeast of “Qice line” (QCXDN); the significant increase in Tmin contributed most in Qaidam Basin (CDM), Hexi inland river basin (HX), the northeast of “Qice line” (QCXDB), and the northwest of “Qice line” (QCXXB), while the contribution of decreasing SD offsets the positive effects of other factors, leading to the decrease in ET0 in HH. Our work illustrates that water management measures should be different at different spatial and temporal scales. The effect of U10 can be offset by covering, to reduce evaporation and maintain water in BGH, QCXXN, and QCXDN. And high-temperature resistant varieties are planted to adapt to temperature growth in CDM, HX, QCXDB, and QCXXB. Agricultural water management strategies should be formulated and selected according to local conditions.
通过往湖泊水样中添加杀菌剂(CuSO4和HgCl2),利用平衡法,用气相色谱仪测定CO2、CH4、N2O浓度,研究杀菌剂(CuSO4和HgCl2)添加对湖泊水体CO2、CH4、N2O浓度分析的影响.实验设计:对照组(CK)不加任何试剂;处理组T1加1mL CuSO4溶液,T2加5 mL CuSO4溶液,T3加0.5 mL HgCl2溶液;每组的水样分两批分析:(Ⅰ)预处理完成后立即分析和(Ⅱ)预处理完成后静置两天再分析.结果表明,CuSO4和HgCl2的添加均能明显增加水体中CO2的浓度,CK(Ⅰ)和CK(Ⅱ)的CO2平均浓度分别为(11.5±1.47)μmol·L-1和(14.38±1.59)μmol·L-1,T1(Ⅰ)和T1(Ⅱ)的CO2平均浓度分别为(376±70)μmol·L-1和(448±246.83)μmol·L-1;T2(Ⅰ)和T2(Ⅱ)的CO2平均浓度分别为(885±51.53)μmol·L-1和(988.83±101.96)μmol·L-1;T3(Ⅰ)和T3(Ⅱ)的CO2平均浓度分别为(287.19±30.01)μmol·L-1和(331.33±22.06)μmol·L-1.但CuSO4和HgCl2添加对水体中CH4和N2O的浓度没有影响.对比Ⅰ和Ⅱ的实验结果可知,在水样预处理完成后需当天分析其温室气体(CO2、CH4、N2O)浓度.本研究表明,杀菌剂的添加能显著增加水体CO2的浓度. 相似文献
A novel magnetically recoverable thioporphyrazine catalyst (CoPz(S-Bu)8/SiO2@Fe3O4) was prepared by immobilization of the cobalt octkis(butylthio) porphyrazine complex (CoPz(S-Bu)8) on silica-coated magnetic nanospheres (SiO2@Fe3O4). The composite CoPz(S-Bu)8/SiO2@Fe3O4 appeared to be an active catalyst in the oxidation of benzyl alcohol in aqueous solution using hydrogen peroxide (H2O2) as oxidant under Xe-lamp irradiation, with 36.4% conversion of benzyl alcohol, about 99% selectivity for benzoic acid and turnover number (TON) of 61.7 at ambient temperature. The biomimetic catalyst CoPz(S-Bu)8 was supported on the magnetic carrier SiO2@Fe3O4 so as to suspend it in aqueous solution to react with substrates, utilizing its lipophilicity. Meanwhile the CoPz(S-Bu)8 can use its unique advantages to control the selectivity of photocatalytic oxidation without the substrate being subjected to deep oxidation. The influence of various reaction parameters on the conversion rate of benzyl alcohol and selectivity of benzoic acid was investigated in detail. Moreover, photocatalytic oxidation of substituted benzyl alcohols was obtained with high conversion and excellent selectivity, specifically conversion close to 70%, selectivity close to 100% and TON of 113.6 for para-position electron-donating groups. The selectivity and eco-friendliness of the biomimetic photocatalyst give it great potential for practical applications. 相似文献