再生水灌溉对深层土壤盐分迁移累积及碳氮转化的影响

发布时间：2018-05-29 20:54

  本文选题：再生水 + 深层土壤　； 参考：《中国农业大学》2016年博士论文

【摘要】：再生水灌溉是缓解水资源短缺地区农业用水压力的重要举措,但是再生水中含有相对较高的盐分、养分及溶解性有机质(DOM)等,再生水灌溉可能增加深层土壤中盐分离子的含量和对地下水的污染风险,增强农田排放温室气体的潜能。本文通过种植夏玉米/冬小麦田间试验,首先研究了不同水氮水平下深层土壤中氮素的迁移特性,以及再生水灌溉下深层土壤中盐分离子的迁移规律；然后率定和验证了再生水灌溉下深层土壤中水盐运移参数,构建了区域模拟模型和评估模型,评估了再生水长期灌溉对地下水的影响；最后借助室内培养试验,一是探讨灌水水质类型(地下水、再生水)、添加氮肥类型(K15NO3、(15NH4)2SO4)和不同含水率(40%、60%和90%WFPS)对土壤N2O排放和氮肥转化的影响机理,二是研究灌水水质类型(地下水、再生水)和氮肥类型(尿素、硫酸铵和缓释肥)对土壤碳和氮矿化的影响机理。获得以下结论：(1)在深层壤土土壤中,3种施氮量(142.5、285.0和427.5 kg Nhm-2)和80 mm灌水定额下NO3--N、NH4+-N和TN主要在0～145 cm土层变化,影响深度为440 cm。在深层非均质土壤中,土壤质地和结构对水分、NO3--N和TN在土壤剖面中的分布有显著影响,土壤结构对NH4+-N在土壤剖面中的分布有显著影响；4种施氮量(0、130、260和390kgNhm-2)和2种灌水定额(52.5和105 mm)下NO3--N、NH4+-N和TN主要在0～400、0～200和0～120 cm土层变化,影响深度为400 cm,而380～450 cm粘质壤土土层对氮素的迁移起到了阻滞作用。(2)在深层非均质土壤中,土壤质地和结构显著影响土壤中盐分离子的含量。3种灌水处理(地下水灌水定额52.5 mm、再生水灌水定额分别为52.5和105 mm)下Na+、Mg2+、SO42-、 HCO3主要在0～120 cm土层中随水分迁移和累积,380～450 cm粘质壤土土层对盐分离子的迁移起到了阻滞作用,减小了对地下水的污染风险。与地下水相比,相同灌水定额的再生水灌溉使土壤中K+、Ca2+和Cl-含量明显增加,3种离子迁移能力较强,分别主要在0～450、0～250和0～120cm土层变化,而影响深度分别为450、450和380 cm。(3)模拟了田间深层非均质土壤中含水率和ECe值,率定和验证了水盐迁移参数。构建了水盐迁移区域模拟模型,结果表明未来50年间通州区和大兴区再生水灌溉包气带底端土壤ECe平均值是0.70和0.85 dS m-1,分别是地下水灌溉的1.40和1.09倍。提出了5个风险指标,构建了区域评估模型,发现通州区和大兴区再生水灌溉盐分对地下水的污染风险分别是地下水灌溉的1.06和1.08倍,而通州区地下水和再生水灌溉的污染风险分别是大兴区的1.75和1.72倍。长期再生水灌溉需要同时考虑再生水中的盐分含量以及包气带结构特性。(4)室内原状土柱添加K15NO3或(15NH4)2SO4并在不同含水率下培养216 h后,不同处理N2O累积排放量为3.78～36.30 mgNm-2,氮肥N2O损失占氮肥总量的0.14%～2.44%,氮肥残留占氮肥总量的10.16%～26.95%。与地下水相比,再生水灌溉土壤在40% WFPS时N2O排放量显著增加了10.98%,在60% WFPS时氮肥残留显著增加了20.95%。灌水水质类型和土壤含水率对氮肥N2O损失具有显著交互作用,灌水水质类型和氮肥类型对氮肥残留也具有显著交互作用,再生水灌溉在特定条件下影响了土壤N2O排放和氮肥转化。氮肥类型和含水率是影响N2O排放量和氮肥转化的2个重要因素。再生水滴灌时控制土壤含水率在41%和60% WFPS之间(最佳含水率为45.5% WFPS)并施用KNO3能减少N2O排放和氮肥N2O损失,增加土壤氮肥残留。(5)室内开展了20 d的碳矿化试验和14周的氮矿化试验,不同处理碳和氮矿化量的平均值分别为73.50～91.37 mg kg-1和52.65～64.04 mg kg-1。与地下水相比,再生水灌溉处理没有显著增加土壤中DOC、DON、有机碳和有机氮的含量,而土壤碳和氮的矿化量分别只增加了3.33%和1.01%。与不施氮肥土壤相比,施尿素、硫酸铵和缓释肥土壤碳和氮的矿化量分别显著增加了14.14%-21.22%和15.81%～22.16%；去DOM后土壤碳和氮的矿化量分别显著降低了9.B3%和14.83%,氮肥和DOM是土壤碳和氮矿化的重要影响因素。(6)综合考虑地下水和再生水灌溉对土壤-地下水-温室气体的影响效应,建议北京和其他类似半湿润气候地区长期再生水灌溉时选择滴灌灌溉,施用NO3-形态氮肥,单季施氮量小于150kg N hm-2,并控制土壤含水率在41%和60% WFPS之间。
[Abstract]:Reclaimed water irrigation is an important measure to alleviate the water pressure in agricultural water shortage area, but the reclaimed water contains relatively high salinity, nutrient and dissolved organic matter (DOM). Reclaimed water irrigation may increase the content of salt ions in deep soil and the risk of contamination of groundwater, and enhance the potential of greenhouse gas emission from farmland. In the field of summer maize / winter wheat field experiment, the migration characteristics of nitrogen in deep soil under different water and nitrogen levels and the migration law of salt ions in deep soil under reclaimed water irrigation were studied, and the parameters of water and salt migration in deep soil under reclaimed water irrigation were determined and verified, and a regional simulation model and evaluation were constructed. The model was used to assess the effect of reclaimed water on long-term irrigation on groundwater. Finally, with the help of indoor culture tests, one was to explore the effects of irrigation water quality (groundwater, reclaimed water), nitrogen fertilizer type (K15NO3, (15NH4) 2SO4) and different water content (40%, 60% and 90%WFPS) on soil N2O emission and nitrogen fertilizer transformation, and two to study irrigation water quality. The influence mechanism of type (groundwater, reclaimed water) and nitrogen fertilizer type (urea, ammonium sulfate and slow release fertilizer) on soil carbon and nitrogen mineralization. The following conclusions are obtained: (1) in deep loam soil, 3 kinds of nitrogen application (142.5285.0 and 427.5 kg Nhm-2) and 80 mm irrigation quota are NO3--N, NH4+-N and TN are mainly in the 0~145 cm soil layer, and the influence depth is 440 cm. in the deep loam soil. In deep heterogeneous soil, soil texture and structure have significant influence on the distribution of water, NO3--N and TN in soil profile. Soil structure has a significant influence on the distribution of NH4+-N in soil profile; 4 nitrogen application (0130260 and 390kgNhm-2) and 2 kinds of irrigation quota (52.5 and 105 mm) NO3--N, NH4+-N and TN mainly from 0 to 400,0 to 200 and 0 to 0 ~. 120 cm soil layer change, the influence depth is 400 cm, and the 380~450 cm clay loam soil layer has blocked the nitrogen migration. (2) in the deep heterogeneous soil, the soil texture and structure significantly affect the content of salt ions in the soil.3 irrigation treatment (groundwater irrigation quota 52.5 mm, reclaimed water irrigation quota is 52.5 and 105 mm respectively). Na+, Mg2+, SO42-, HCO3 are mainly migrated and accumulated in the 0~120 cm soil layer with water, and the 380~450 cm clay loam soil layer plays a blocking effect on the migration of salt ions and reduces the risk of pollution to the groundwater. Compared with the groundwater, the same irrigation quota of regenerated water irrigation makes the content of K+, Ca2+ and Cl- significantly increased, 3 kinds of ions in the soil. The migration ability is strong, mainly in 0 ~ 450,0 ~ 250 and 0 ~ 120cm soil layers, and the depth of influence is 450450 and 380 cm. (3) respectively. The water content and ECe value in the deep inhomogeneous soil in the field are simulated. The water and salt migration parameters are determined and verified. The simulation model of water and salt migration is constructed. The results show that Tongzhou District and Daxing are in the next 50 years. The average value of soil ECe at the bottom end of the zone of reclaimed water irrigated by regenerated water is 0.70 and 0.85 dS M-1, 1.40 and 1.09 times of groundwater irrigation, respectively. 5 risk indexes are put forward, and a regional evaluation model is put forward. It is found that the risk of groundwater pollution in Tongzhou District and Daxing District is 1.06 and 1.08 times of groundwater irrigation, while Tongzhou District The pollution risk of groundwater and reclaimed water irrigation is 1.75 and 1.72 times as high as that of Daxing District. Long term reclaimed water irrigation needs to consider the salt content of the regenerated water and the structural characteristics of the cladding zone. (4) K15NO3 or (15NH4) 2SO4 is added to the original soil column and 216 h under different water content, and the cumulative emission of N2O is 3.78 ~ 3 at different treatments. 6.30 mgNm-2, nitrogen fertilizer N2O loss accounted for 0.14% ~ 2.44% of total nitrogen, nitrogen residue accounted for 10.16% ~ 26.95%. of total nitrogen, compared with ground water, the N2O emission of the soil irrigated by reclaimed water was significantly increased by 10.98% at 40% WFPS. At 60% WFPS, the nitrogen residue significantly increased the 20.95%. water quality and the soil moisture content to the N2O loss of nitrogen fertilizer. The irrigation water quality and nitrogen type have significant interaction with nitrogen fertilizer residues. The reclaimed water irrigation affects the soil N2O emission and nitrogen fertilizer conversion under specific conditions. Nitrogen type and water content are 2 important factors affecting N2O emission and nitrogen fertilizer conversion. The soil water content of the regenerated water drip irrigation is 41% and the soil water content is controlled by the reclaimed water drip irrigation. 60% WFPS (the optimum water content is 45.5% WFPS) and KNO3 can reduce N2O emission and nitrogen fertilizer N2O loss and increase soil nitrogen fertilizer residues. (5) 20 d carbon mineralization test and 14 week nitrogen mineralization test have been carried out in the room. The average value of different treatments of carbon and nitrogen mineralization is 73.50 to 91.37 mg kg-1 and 52.65 to 64.04 mg kg-1. and underground water facies, respectively. In contrast, reclaimed water irrigation did not significantly increase the content of DOC, DON, organic carbon and organic nitrogen in soil, while the mineralization of soil carbon and nitrogen increased by 3.33% and 1.01%., respectively, and the mineralization of carbon and nitrogen in urea, ammonium sulphate and slow-release fertilizers increased by 14.14%-21.22% and 15.81% to 22.16%, respectively, and to DO After M, the mineralization of soil carbon and nitrogen was significantly reduced by 9.B3% and 14.83%. Nitrogen and DOM were important factors for the mineralization of soil carbon and nitrogen. (6) the effects of groundwater and reclaimed water irrigation on soil groundwater and greenhouse gases were considered. It was suggested that the drip irrigation should be selected in Beijing and other semi humid regions. Irrigation, applying NO3- form nitrogen fertilizer, single crop nitrogen application amount was less than 150kg N hm-2, and control soil moisture content between 41% and 60% WFPS.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S153;S274
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本文编号：1952357