共查询到20条相似文献，搜索用时 530 毫秒
1.
通过15N示踪试验,以及根据嫌气条件下含15NH4+培养液加无定形氧化铁后全氮回收量下降(损失15N约15%),以及产生15NO2、15N2O、15N14NO、15NO、15N2和15N14N等含N气体的研究结果,初步证明无定形氧化铁可作为嫌气下NH4+氧化时的电子受体,这可能是引起水田土壤中铵态氮肥损失的又一机理。目前因无各种合15N氧化物标准气体,无法对其形成的含15N气体组分进行定量,这一机理对氮素损失的贡献究竟有多大?尚需进一步研究。 相似文献
2.
应用传统的径流系数法与SCS-CN模型法预测了北京市门头沟西侧小流域雨水资源利用潜力,并对比了不同方法预测的雨水资源量及其时空分布规律。结果表明,径流系数法预测的丰水年(P=25%)、平水年(P=50%)、枯水年(P=75%)和多年平均年份地表雨水资源量分别为:2.84×107m3,1.98×107m3,1.22×107m3和2.14×107m3。模型法预测的丰水年、平水年、枯水年和多年平均地表雨水资源量分别为:3.21×107m3,2.16×107m3,1.31×107m3和2.50×107m3,经验法预测值小于模型法。夏季的7月,地表的雨水资源利用潜力达到相应特征年份的最大值。 相似文献
3.
气候变暖对甘肃省不同气候类型区主要作物需水量的影响 总被引：6，自引：0，他引：6
作物需水量是农田水分循环系统中最重要的因素之一。在未来温度上升1~4 ℃的情景下, 研究了气候变暖对我国甘肃省不同气候类型区主要作物需水量的影响。结果表明, 气候变暖对不同作物需水量的影响程度不同。其中对冬小麦需水量的影响最大, 对玉米和春小麦次之。当生长期内温度上升1~4 ℃时, 冬小麦需水量将增加3.05%~12.90%, 相当于13.2~81.2 mm; 玉米需水量将增加2.49%~10.80%, 相当于9.9~60.6 mm;春小麦需水量将增加2.74%~11.69%, 相当于6.7~40.0 mm。气候变暖对作物需水量的影响存在一定地域性差异。对干旱区的作物需水量影响最大, 半干旱区次之, 其次是半湿润区, 对湿润区影响不大。根据甘肃省目前的种植结构, 据此估算, 当温度上升1~4 ℃时, 将使甘肃省冬小麦的灌溉需水量增加12.43×108 m3、13.02×108 m3、13.74×108 m3 和14.65×108 m3, 玉米的灌溉需水量增加7.94×108 m3、8.32×108 m3、8.78×108 m3 和9.30×108 m3, 春小麦的灌溉需水量增加4.97×108 m3、5.16×108 m3、5.42×108 m3 和5.76×108 m3。 相似文献
4.
第四纪红色粘土发育的红壤中营养元素的淋失 总被引：13，自引：2，他引：11
A red soil derived from Quaternary red clay was employed to study nutrient leaching with soil columns repacked in laboratory. The objective was to identify the effects of fertilization practices on leaching patterns and magnitudes of Ca2+, Mg2+, K+, NH4+, and NO3-. The treatments were CK (as a control), CaCO3, CaSO4, MgCO3, Ca(H2PO4)2, urea, KCl, and multiple (a mixture of the above-mentioned fertilizers). The fertilizers were added to the bare surface of the soil columns, and then the columns were leached with 120 mL deionized water daily through peristaltic pumps over a period of 92 days. Leaching processes of NH4+, and NO3- were only measured in CK, urea, and multiple treatments which were directly related to N leaching. Results showed that sole application of CaSO4, and Ca(H2PO4)2 scarcely had any effect on the leaching losses of Ca2+, Mg2+, and K+; the application of MgCO3 stimulated the leaching of Mg2+; the application of CaCO3 promoted the leaching of Ca2+, Mg2+ and K+; urea treatment also promoted the leaching of K+ and NH4+, and NO3- leaching mainly occurred at late stage of leaching process in particular; under KCl treatment, leaching of Ca2+, Mg2+, and K+ was promoted to a large extent; under multiple treatment, leaching of Ca2+, Mg2+, K+, NH4+, and NO3- was all increased and NO3- was mainly leached at the end of leaching process and still had a trend of increase. 相似文献
5.
土壤水分状况对14C标记秸秆的腐解及腐殖质中碳素分布的影响 总被引：2，自引：0，他引：2
14C-tracer technique and closed incubation method were used to study straw 14C decomposition and distribution in different fractions of newly formed humus under different moisture regimes. Decomposition of straw 14C was faster during the initial days, and slower thereafter. Decay rate constants of straw 14C varied from 3.29 × 10-3 d-1 to 7.06 × 10-3 d-1. After 112 d incubation, the amount of straw 14C mineralized was 1.17~1.46 times greater in submerged soils than in upland soils. Of the soil residual 14C, 9.08%~15.73% was present in humic acid (HA) and 31.01%~37.62% in fulvic acid (FA). Submerged condition favored the formation of HA, and HA/FA ratio of newly formed humus (labelled) was greater in submerged soils than in upland soils. Clay minerals affected the distribution of straw 14C in different humus fractions. Proportion of 14C present in HA to 14C remaining in soil was greater in Vertisol than in Ultisol. 相似文献
6.
通过水培试验探讨了NO-3胁迫下K+、Ca2+对黄瓜幼苗膜质过氧化及活性氧清除酶系统的影响。结果表明，在相同NO-3浓度胁迫7d后， Ca2+浓度越大，膜脂过氧化产物丙二醛(MDA)含量越高，而K+浓度越大，电解质相对渗透率越高，由此说明K+、Ca2+对细胞膜造成伤害的机理不同。黄瓜幼苗活性氧清除酶系统对K+、Ca2+的响应亦不同，在一定程度上，K+和Ca2+ 可提高SOD、POD和CAT活性，保护植物免受自由基伤害，继而可增强植物对逆境的适应能力。 相似文献
7.
尿素肥斑中氮素形态转化初探 总被引：1，自引：0，他引：1
采用特制模拟容器,通过尿素扩散形成营养斑,观察斑内NH4+、NO2-和NO3-浓度变化及它们之间的相互转化。结果表明,NH4+、NO2-和NO3-浓度在距离肥斑7～8cm处的微域达到最大,尤以NO2-浓度增加较为显著,是一般土壤NO2-水平的数千倍。随培养时间增加,NO2-和NO3-最大浓度峰向施肥点移动,但两者浓度变化趋势不同,NO2-浓度在21d前随培养时间增加而增加,之后随培养时间增加而下降,而NO3-浓度随培养时间增加一直增加。结果还表明,NO2-是尿素营养斑内主要离子形态,从NH4+到NO2-的转化比较迅速,而NO2-转化为NO3-不是短暂的过程,这可能与施肥引起的土壤pH值变化有很大关系。 相似文献
8.
根据甘肃省黄土高原区城市雨洪资源的分布特征,选取主要城市兰州、定西、平凉、庆阳和天水为研究区,研究了各主要城市降水量特征变化规律,并对各主要城市雨洪资源利用潜力进行了分析计算。结果表明,兰州、定西、平凉、庆阳和天水雨洪资源的平均理论潜力分别为5.71×107,8.61×106,2.38×107,7.62×106和3.21×107m3,平均可实现潜力分别为2.91×107,4.65×106,1.43×107,4.87×106和1.95×107m3。计算结果说明,甘肃黄土高原区各主要城市雨洪资源利用潜力相对较大,具有很好的开发利用前景,并且可为黄土高原区城市雨洪资源高效利用和有效管理提供参考依据。 相似文献
9.
新疆棉花种植面积的时空变化及适度规模研究 总被引：6，自引：0，他引：6
本研究通过对建国以来新疆植棉业的调查数据进行统计分析, 探究其时序演变规律和空间分布特点,并运用模糊数学理论和层次分析法, 构建植棉规模及其影响因素的交互作用模型, 揭示新疆植棉业发展的适度规模。研究结果表明: (1)1949 年以来, 新疆植棉规模不断扩大, 从1949 年的33.41×103 hm2 上升到2007 年的1 782.60×103 hm2, 且表现出明显的阶段性和波动性; 三大棉区即南疆棉区、北疆棉区、东疆棉区变化特点各异, 其中南疆棉区起主导作用; 按绿洲分类棉区中, 以塔里木盆地绿洲棉区和西北沿边绿洲棉区变化明显。(2)现有条件下, 整个新疆棉花种植经营适度规模以800×103~1 000×103 hm2 为最优, 600×103~800×103 hm2 次之,400×103～600×103 hm2 再次之, ＞1 000×103 hm2 最差。该规模标准可作为制定新疆植棉业发展、安排植棉业经济投入和劳动力投入、进一步优化农业产业结构的依据。 相似文献
10.
Interactions of three heavy metal ions, Cu2+, Cd2+, and Pb2+, and, for comparison, Na+ with electrodialytic clay fractions (less than 2 μm in diameter) of four paddy soils as well as a yellow-brown soil as a control soil were evaluated based on measurements of the Wien effect in dilute suspensions with a clay concentration of 10 g kg?1 in four nitrate solutions of 2 × 10?4/z mol L?1, where z is the cation valence, and a nitric acid solution of 3 × 10?5 mol L?1. Field strengths ranging from 15 to 230 kV cm?1 were applied for measuring the electrical conductivities (ECs) of the suspensions. The mean free binding energies between the various cations and all of the soils determined from exchange equilibrium increased in the order: Na+ < Cd2+ < Cu2+ < Pb2+. In general, the ECs of the suspensions in the sodium nitrate solution were smaller than those of the suspensions in the heavy metal solutions because of the lower electrophoretic mobility of sodium compared to the divalent cations. In terms of relative electrical conductivity-field strength relationships, relative electrical conductivity (REC) of suspensions containing various cations at field strengths larger than about 50 kV cm?1 were in the descending order: Na+ > Cu2+ > Cd2+ > Pb2+ for all tested soils. A characteristic parameter of the REC-field strength curves, ΔREC200, REC at a field strength of 200 kV cm?1 minus that at the local minimum of the concave segment of the REC-field strength curves, characterized the strength of adsorption of the cations stripped off by the applied strong electrical field, and for all soils the values of ΔREC200 were generally in the order: Na+ < Cu2+ ≤ Cd2+ ≤ Pb2+. 相似文献
11.
基于稳定同位素和贝叶斯模型的引黄灌区地下水硝酸盐污染源解析 总被引：5，自引：0，他引：5
地下水硝酸盐（NO3-）污染已经成为全球严重的水环境问题之一,由于饮用水中高含量NO3-会转化成亚硝酸盐而增加各种疾病和癌症风险,其来源的确定对于NO3-污染的预防和控制非常重要。本文以黄河下游第二大灌区——潘庄灌区为例,首次采用NO3-的氮氧稳定同位素结合贝叶斯模型追溯地下水NO3-的来源并量化各种来源的贡献比例。结果表明,地下水NO3-含量分布在0.1~197.0 mg·L-1,平均值为34.2 mg·L-1。与《生活饮用水卫生标准》中规定的地下水NO3-最大含量[20 mg（N）·L-1,相当于NO3-含量90 mg·L-1]相比,有10%的样品NO3-含量超标。井深<30 m、30~60 m和>60 m的地下水NO3-平均含量分别为25.9 mg·L-1、39.7 mg·L-1和20.1 mg·L-1。空间上,宁津县、武城县、平原县和禹城市有大片区域地下水NO3-含量较高。地下水NO3-的δ15N组成范围为0.72‰~23.93‰,平均值为11.62‰;δ18O组成范围为0.49‰~22.50‰,平均值为8.46‰。同位素结果表明粪便和污水、农业化肥是地下水中NO3-的主要污染来源。这反映了人类活动是引起地下水NO3-污染的主要原因。贝叶斯模型结果显示,粪便和污水对潘庄灌区地下水中NO3-平均贡献率高达56.2%,化肥的平均贡献率为19.3%,大气降水和土壤的平均贡献率分别为6.2%和12.3%。由于污水、粪便和化肥是地下水中NO3-的主要来源,为保护和改善研究区地下水水质,建议加强污水管道建设,强化畜禽粪便的管理以及提高化肥利用效率。 相似文献
12.
松嫩平原盐渍土主要类型、性质及其形成过程 总被引：10，自引：0，他引：10
松嫩平原是我国内陆盐清土主要分布地区之一.这里的盐清土从很早以前就已开始受到注意.川岛[17]池田[16],[18]宋达泉[6.10]、陈恩凤[1-3]熊毅[4]、B.A.柯夫达[7,9]И.П.格拉西莫夫和焉溶之[5]、程伯容[8]等的研究对这个地区盐清土的剖面性态、理化性质、发生分类和地理分布砚律方面提供了大量宝贵的资料. 相似文献
13.
升高CO2浓度能够促进作物的光合作用，提高作物的生物量和产量，但关于CO2与NH+4/NO-3比及其交互作用对作物影响的研究较少，为探索番茄幼苗生长发育对CO2浓度升高的响应是否对NH+4/NO-3配比有较强的依赖关系，本试验在营养液栽培条件下，以番茄(Lycopersicun esculentum Mill)为试材，研究正常大气CO2浓度(360 μL/L)和倍增CO2浓度(720 μL/L)与不同NH+4/NO-3配比的交互作用对番茄幼苗生长的影响。结果表明：CO2浓度升高提高了低NH+4/NO-3比例处理中番茄叶片的光合速率和水分利用率，提高幅度随NH+4/NO-3比例的降低而增强，光合速率增强最大达55%。在同一CO2浓度处理下净光合速率与水分利用率均随NH+4/NO-3比例的增加而显著降低。这说明CO2浓度升高对番茄幼苗生长发育的促进作用随NH+4/NO-3比例的降低而提高，但并没有减弱全NH+4-N处理中番茄幼苗的受毒害作用。综上所述，CO2浓度升高能提高植物生产的节水能力和水分生产力；水培条件下，NO-3-N是最适合番茄幼苗生长发育的氮源，其它NH+4/NO-3比例对番茄幼苗的生长发育有一定的抑制作用，仅以NH+4-N作氮源则番茄幼苗很难生长。 相似文献
14.
Hydraulic Resistance and Capacitance in the Soil-Plant System 总被引：1，自引：0，他引：1
In this paper, the hydraulic resistances and capacitances were evaluated. based on the development of non-(?) model of water flow in the soil-plant system and the simulating experiment work.The results show that the mean hydraulic resistance in the soil-plant system is 6.79×109 MPa·S·m-3; the mean hydraulic capacitance in the system is 5.2×107m3·MPa-1. In the components of hydraulic capacitance in the system, the capacitance in soil (81.8×10-6m3·MPa ) is the biggest and its variability with suii water potential is extremely strong, the capacitance in plant (5.3×10-7m3·MPa-1) is much smaller than that in soil, and the capacitance in shoots (15.5×10-7m3·2MPa-1) is bigger than that in roots (8.4×10-7m3·2MPa-1). An interesting result is that the capacitance in plant is almost equivalent to that in the soil-plant system. 相似文献
15.
本文应用穆斯堡尔谱学方法,研究了在不同pH条件下Fe+++,Fe++与胡敏酸结合的性质。计算机拟合的pH3.057Fe-胡敏酸络合物泥浆的穆斯堡尔谱和参数表明,三对四极双峰(图1,AA',BB',CC')是合理的。在pH3.0 Fe+++以高自旋态存在,它和胡敏酸的结合多于一种环境类型。在pH1.0的57Fe-胡敏酸络合物中,观察到了Fe+++的穆斯堡尔谱信号,但没有Fe++的信号,在这个样品离心分离出的液体部分检测到了加入量的59.7%的铁,表明在pH1.0时相当数量的Fe+++被胡敏酸还原成Fe++,Fe++并不与胡敏酸牢固结合。在30伏电析过的57Fe-胡敏酸络合物样品中(pH2.8)出现了Fe+++,Fe++的穆斯堡尔谱,这一结果指示出,在电析过程中由于57Fe+++-胡敏酸络合物悬浮液pH的降低,一部分Fe+++还原成Fe++,在pH2.8相当数量的Fe++与胡敏酸牢固结合。根据在80K记录的穆斯堡尔谱,在pH1—3的范围出现了磁有序成份,但在室温记录的穆斯堡尔谱没有磁分裂。 相似文献
16.
二价锰离子对柠檬酸还原六价铬的催化作用 总被引：2，自引：0，他引：2
The catalysis of manganese(Ⅱ) (Mn2+) on chromium(Ⅵ) (Cr6+) reduction by citrate was studied through batch experiments with the concentration of citrate greatly in excess of Cr6+ at 25℃ and in pH ranges of 4.0 to 5.0. Results showed that at pH 4.5 within 22 h direct reduction of Cr6+ by citrate was not observed, but for the same time when Mn2+ (50 to 200μmol L-1) was added, nearly all Cr6+ was reduced, with the higher initial Mn2+ concentration having faster Cr6+ reduction. In the initial stage of the reaction, the Cr6+ reduction could be described with a pseudo-first-order kinetics equation. In the later stage of the reaction, plots of lnc(Cr6+) versus t, where c(Cr6+) is the Cr6+ concentration in the reaction and t is the reaction time, deviated from the initial linear trend. The deviations suggested that the pseudo-first-order kinetics did not apply to the whole experimental period and that some reaction intermediates could have greatly accelerated Cr6+ reduction by citrate. The catalysis of the intermediates increased with the reaction time and gradually reached stability. Then, the plot of lnc(Cr6+) versus t in the presence of Mn2+ was linear again, with the rate constant increasing by 102 times compared with the absence of Mn2+. Complexation between Mn2+ and citrate was likely a prerequisite for the catalysis of Mn2+ on the reaction. Additional experiments showed that introducing ethylenediaminetetraacetic acid (EDTA) into the reaction system strongly suppressed the catalysis of Mn2+. 相似文献
17.
Plants show different growth responses to N sources supplied with either NH4+ or NO3-. The uptake of different N sources also affects the rhizosphere pH and therefore the bioavailability of soil phosphorus, particularly in alkaline soils. The plant growth, P uptake, and P availability in the rhizosphere of oat (Avena nuda L.) grown in hydroponics and in soil culture were investigated under supply with sole NH4+-N, sole NO3--N, or a combination. Sole NO3--fed oat plants accumulated more biomass than sole NH4+-fed ones. The highest biomass accumulation was observed when N was suppliedw ith both NH4+-N and NO3--N. Growth of the plant root increased with the proportion of NO3- in the cultural medium. Better root growth and higher root/shoot ratio were consistently observed in NO3--fed plants. However, root vigor was the highest when N was supplied with NO3-+NH4+. NH4+ supply reduced the rhizosphere pH but did not affect P uptake by plants grown in soils with CaHPO4 added as P source. No P deficiency was observed, and plant P concentrations were generally above 2 g kg-1. P uptake was increased when N was supplied partly or solely as NO3--N, similarly as biomass accumulation. The results suggested that oat was an NO3--preferring plant, and NO3--N was essential for plant growth and the maintenance of root absorption capacity. N supply with NH4+-N did not improve P nutrition, which was most likely due to the absence of P deficiency. 相似文献
18.
灌溉对大麦/玉米带田土壤硝态氮累积和淋失的影响 总被引：7，自引：3，他引：7
以甘肃省河西走廊灌区为试验地点，分别在0、150、300 kg/hm2氮水平和816、1632 m3/hm2灌水量下，对3次灌水前、后大麦/玉米带田0～200 cm土壤NO-3-N含量变化和灌水后135 cm处渗漏液NO-3-N浓度进行了测定。结果表明：灌水明显影响土壤硝态氮累积量，随灌水次数增加，土壤硝态氮累积量降低，而且在高灌水条件下土壤硝态氮累积量变化比低灌水量时大。从渗漏液硝态氮浓度来看，大麦带和玉米带都是以第1次灌水最高，浓度分别为8.04～17.21和3.30～14.57 mg/L。3次灌水土壤硝态氮淋失量，玉米带以N 150 kg/hm2和灌水量1632 m3/hm2最高，平均为4.31 kg/hm2；大麦带以N 150 kg/hm2及灌水量1632 m3/hm2和N 150 kg/hm2及灌水量816 m3/hm2比较高，平均为6.82 kg/hm2。 相似文献
19.
华北平原小麦-玉米农田生态系统服务评价 总被引：8，自引：1，他引：7
本研究于2006 年和2007 年在中国科学院栾城农业生态系统试验站田间试验基础上, 评价了华北平原小麦-玉米农田的初级产品生产、气体调节、土壤有机质累积、水调节和氮素转化等5 项生态系统服务。研究表明, 华北平原小麦-玉米农田初级产品量包括籽粒产量5.04~5.71 t·hm-2·a-1(小麦)和6.69~8.24t·hm-2·a-1(玉米), 秸秆量8.58~9.72 t·hm-2·a-1(小麦)和6.97~8.58 t·hm-2·a-1 (玉米); 农田气体调节包括释放O2 24.99~28.64 t·hm-2·a-1, 固定CO2 34.23~39.22 t·hm-2·a-1, 排放N2O 0.72~1.13 kg·hm-2·a-1, 吸收CH4 3.39~5.70 kg·hm-2·a-1; 农田耕层土壤有机质累积量为1.13~2.39 t·hm-2·a-1; 水资源消耗量为2 890~3 830 m3·hm-2·a-1; 农田土壤氮素几乎都处于亏缺状态, 变化范围为-107.73~5.33 kg(N)·hm-2·a-1, 不施氮肥农田亏缺较多。综合评价发现, 小麦-玉米农田提供生态服务的经济价值为5.48~6.25 万元·hm-2·a-1, 是粮食生产价值的3 倍左右。氮肥施用对农田生态系统服务及其产生福利的影响较为复杂, 这主要是由于施加氮肥明显增加了氮素转化功能导致的经济损失, 而同时可能会增加初级产品生产、气体调节中作物固定CO2 和释放O2 功能的经济价值。尽管目前有关生态系统服务评价研究主要关注生态系统产生的正效应, 但仍有必要对农田产生的负效应做出评价, 以便客观看待农田生态系统价值, 正确认识农田生态系统对人类福利的影响。 相似文献
20.
一种直接测定硝化—反硝化气体的15N示踪—质谱法 总被引：3，自引：0，他引：3
本文对15N示踪—质谱法的可靠性进行了检验。结果表明,在不同的15N丰度气体样品的测定中,用两种方法(反硝化作用源的15N丰度法和气样的15N丰度法)计得的反硝化损失量基本一致,故建立起来的15N示踪—质谱法是可靠的。该方法的测定偏差随气样15N丰度的降低而增大。此外,回收率结果表明,(N2+N2O+NOx)-15N累积释放量占加入NO3-15N量的94.1％。因此,这一方法可用于直接测定氮肥的硝化—反硝化损失的研究中。 相似文献