Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils

The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carried out at 60%WHC(water holding capacity)and 25℃to evaluate the gross N transformation rates and N_(2)O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province,China.The results showed that the gross rates of N mineralization,immobilization,and nitrification were 3.60,1.90,and 5.63 mg N/(kg·d)in silt loam soil,respectively,which were 3.62,4.26,and 3.13 times those in sandy loam soil,respectively.The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia)in sandy loam soil and silt loam soil were all higher than 1.00,whereas the n/ia in sandy loam soil(4.36)was significantly higher than that in silt loam soil(3.08).This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil,and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_(3)–leaching.Under aerobic conditions,both nitrification and denitrification made contributions to N_(2)O emissions.Nitrification was the dominant pathway leading to N_(2)O production in soils and was responsible for 82.0%of the total emitted N_(2)O in sandy loam soil,which was significantly higher than that in silt loam soil(71.7%).However,the average contribution of denitrification to total N_(2)O production in sandy loam soil was 17.9%,which was significantly lower than that in silt loam soil(28.3%).These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.

Effects of NaCl salt on mineralization and nitrification of a silt loam soil in the North China Plain

Low quality water has been widely used for irrigation all over the world due to water shortage.However,the use of low quality water may cause accumulation of salt in root-zone soils,resulting in poor nitrogen utilization by crops.The objective of the present study was to investigate the effects of sodium chloride(NaCl)on mineralization and nitrification of soils in the North China Plain(NCP).The experiments were conducted with laboratory incubators at 30℃.Five levels of NaCl-salt concentrations 0%,2%,3%,5%and 8%in the added solutions were used in the soil samples collected from NCP.The mineralization at NaCl-salt concentration lower than 3%was not significantly different from that of the control,whereas,significant inhibition of mineralization was found in the treatments with NaCl-salt concentration higher than 3%.The inhibition of mineralization was attributed to the retardation of nitrification in relatively high salt content because ammonification was not depressed by the added NaCl salt.The gas losses and nitrification were found decreasing with the increase in salinity.It was also found that the nitrification was more sensitive to salinity than the mineralization.Nitrification of soil samples was inhibited by 44.72%,57.87%,and 83.64%compared with the control after 38 days of incubation at NaCl-salt concentrations of 3%,5%and 8%,respectively.The time dependence of both the mineralization and nitrification can be fitted into a first-order kinetic model.The rate constant of mineralization and nitrification decreased exponentially with the salt content in the soils.The results of the present research may provide some scientific implications for the use of saline water or treated sewage water in the farming regions of the NCP.

Threshold friction velocity influenced by soil particle size within the Columbia Plateau, northwestern United States

Wind erosion is a geomorphic process in arid and semi-arid areas and has substantial implications for regional climate and desertification.In the Columbia Plateau of northwestern United States,the emissions from fine particles of loessial soils often contribute to the exceedance of inhalable particulate matter(PM)with an aerodynamic diameter of 10μm or less(PM10)according to the air quality standards.However,little is known about the threshold friction velocity(TFV)for particles of different sizes that comprise these soils.In this study,soil samples of two representative soil types(Warden sandy loam and Ritzville silt loam)collected from the Columbia Plateau were sieved to seven particle size fractions,and an experiment was then conducted to determine the relationship between TFV and particle size fraction.The results revealed that soil particle size significantly affected the initiation of soil movement and TFV;TFV ranged 0.304-0.844 and 0.249-0.739 m/s for different particle size fractions of Ritzville silt loam and Warden sandy loam,respectively.PM10 and total suspended particulates(TSP)emissions from a bed of 63-90μm soil particles were markedly higher for Warden sandy loam than for Ritzville silt loam.Together with the lower TFV of Warden sandy loam,dust emissions from fine particles(<100μm in diameter)of Warden sandy loam thus may be a main contributor to dust in the region's atmosphere,since the PM10 emissions from the soil erosion surfaces and its ensuing suspension within the atmosphere constitute an essential process of soil erosion in the Columbia Plateau.Developing and implementing strategic land management practices on sandy loam soils is therefore necessary to control dust emissions in the Columbia Plateau.

酚在饱水亚砂土层中迁移转化的研究

通过静态吸附实验、静态降解实验和动态土柱实验，研究了苯酚在饱和亚砂土层中的吸附性能，在好氧和厌氧条件下的降解性能以及其他有机物和氮、磷等营养元素对苯酚降解过程的影响；实验结果用计算机进行线性拟合和参数估值，求解出分配系数Ｋｄ＝０．１１２ｃｍ３／ｇ和降解系数Ｋ＝０．５５ｄ（－１）。研究表明，苯酚在亚砂土层中的吸附性能较差，在好氧条件下具有很好的降解性能，而在厌氧条件下，其降解性能极差；营养元素氮、磷的存在将加速生物降解作用；受固体效应的影响，静态吸附实验求得的Ｋｄ偏大。

特大暴雨作用下土壤盐分运移特征研究

利用粉砂壤土柱研究特大暴雨过程中土壤盐分运移特征结果表明 ,当地下水埋深为 1.5m时特大暴雨作用下 0～ 30cm土层土壤盐分下移至 30～ 10 5cm土层段 ,属浅位脱盐 ,雨后土壤盐分极易再次升至耕作层 ;地下水埋深为 2 .5m时 0～ 83cm土层土壤盐分下移至 83～ 2 0 0cm土层段 ,其淋洗效果最佳 ;地下水埋深为 3.0m时 10 0～ 2 0 0cm土层土壤盐分下移至 2 0 5～ 2 5 5cm土层段 ,属深部脱盐。

盐分对粉壤土氮转化的影响

采用室内恒温通气培养法,以北京地区耕作层典型粉壤土为对象,研究盐分对土壤氮素矿化和硝化的影响.实验设置了4个不同盐分〔以ρ(NaCl)计,分别为20,30,50和80 mg/L〕处理和对照处理,并在硝化实验的土壤中加入一定量的(NH4)2SO4,分别在30℃恒温培养箱中进行为期105 d(矿化)和49 d(硝化)的培养实验.结果表明:在初期的培养中,低盐分有利于土壤氮素转化,ρ(NaCl)为20 mg/L的处理分别比对照处理的累积矿化量和累积硝化量多18.21%和1.87%;而在长期培养过程中,高盐分不利于土壤氮素转化,且ρ(NaCl)越高抑制越明显,其对土壤氮素矿化和硝化的抑制率达到67.92%和62.58%;土壤矿化势和硝化势随w(NaCl)分别呈指数递减,矿化速率常数和硝化速率常数与土壤中w(NaCl)为二次函数关系.

Dynamic Monitoring of the Mud

[Objective] The research aimed to provide basic files and theoretical guidance for constructing sluicing-siltation dam using soil with high clay content soil.[Method] The soils of Dagou basin near Xiwu Village of Baishui County,Shaanxi Province were taken as experimental materials.pvc pipes with same height and diameter were used to construct testing model for dynamically determining settlement,shear strength,wet density of grouting bulk under 2 different grouting speeds(15 cm/d and 25 cm/d).[Result] Under different grouting speeds,general change trend was similar during grouting course.The subsidence,deformation,shear strength and wet density increased with the increase of grouting speed.Five or six days after grouting,daily displacement under 25 cm/d grouting speed was fewer than that under 15 cm/d grouting speed.[Conclusion] The increase of grouting speed could shorten the time for reaching the same subsidence,deformation,shear strength and wet density and increased displacement at the initial stage of grouting,however,with the increase of grouting time,lower grouting bulk was bad for displacement at later grouting period because it was near impermeable layer.

不同质地黑土净氮转化速率和温室气体排放规律研究

为探讨黑龙江省半干旱地区不同质地黑土的净氮转化速率和温室气体排放规律,以壤砂土和粉壤土为研究对象开展室内培养试验,对土壤净硝化速率和净矿化速率、N2O和CO2排放速率与累积排放量进行研究。结果表明:7d培养期间壤砂土的平均净矿化速率和CO2平均排放速率分别为0.49mgN kg-1 d-1和0.30mgCO2-C kg-1 h-1,显著低于粉壤土的平均净矿化速率(1.37 mgN kg-1 d-1)和CO2平均排放速率(0.47mgCO2-C kg-1 h-1)。壤砂土的平均净硝化速率和N2O平均排放速率分别为1.65mgN kg-1 d-1和212.6ngN2O-N kg-1 h-1,显著低于粉壤土的5.02mgN kg-1 d-1和521.3ngN2O-N kg-1 h-1。壤砂土和粉壤土的N2O排放比率分别为0.081%~0.301%和0.210%~0.254%。研究表明,土壤质地显著影响土壤净氮转化速率和温室气体排放,壤砂土较低的pH、有机碳和水溶性有机碳含量是导致其净硝化速率、净矿化速率以及N2O、CO2排放速率显著低于粉壤土的主要原因。

基于地中渗透仪的入渗补给方式分析

文章通过在某均衡试验场地中的渗透仪上开展土壤水流穿透试验,分析灌溉水对地下水补给方式。试验结果表明:淹灌条件下,粉细砂扰动土中的穿透曲线为典型的单峰对称型,表明粉细砂中的土壤水通过活塞式入渗补给地下水;而亚粘土中的穿透曲线显示多峰、优先穿透、拖尾等现象,表明亚粘土中的土壤水以优势流方式补给地下水。通过对均衡场降水入渗补给的长观资料分析发现:在自然降雨条件下亚粘土中优势流明显,粉细砂中主要以活塞流为主。

重粉质壤土泥浆泵筑坝人工管网排水技术研究

人工管网排水技术在泥浆泵筑坝工艺中的应用,为重粉质壤土区修筑泥浆坝提供了基础资料和理论指导,也为同类地区推广应用该筑坝技术,普及该排水措施提供了科学依据。以陕西省白水县西武村附近雷牙沟流域的黄土作为试验对象,对该排水系统的布设、施工方法及其排水效果进行了试验研究。结果表明,排水管道的材料选定和管道布设形式是影响坝体排水的决定性因素;聚乙烯微孔波纹管排水系统在一定程度上加速坝体脱水固结,但效果不显著;重粉质壤土黏粒含量较高,致使泥浆排水困难。人工管网排水技术在泥浆泵筑坝试验中的应用加速了坝体脱水固结,但是效果不佳,还需不断总结经验,选取理想的管道滤水材料,合理布设排水管道并完善排水设施。

重粉质壤土泥浆特性动态检测

[目的]为用舍粘粒量高的土修建水坠坝提供基础资料和理论指导。[方法]以陕西白水县西武村附近大沟流域的土作为试验对象，用等高等直径的PVC管样桶组建测试模型，对2种灌浆速度（15和25cm／d）下灌浆体的沉降量、抗剪强度、湿密度、下渗量等指标进行动态测定。[结果]不同灌浆速度下，灌浆过程中灌浆体各指标的总体变化趋势相同。对于同一高度的灌浆体，其沉陷变形、抗剪强度、湿密度均表现为灌浆速度大则相应的值大。灌浆5～6d以后，以25cm／d速度灌浆的日排水量小于以15cm／d速度灌浆的日排水量。[结论]灌浆速度加大可缩短达到相同沉陷变形、抗剪强度和湿密度的时间，可明显增加灌浆初期排水量，但随灌浆时间的累积，下层灌浆体接近不透水层而不利于灌浆后期的排水。

粉砂壤土中大孔隙对坡地产汇流的影响

以室内试验槽为平台,采用人工模拟降雨实验,研究粉砂壤土大孔隙对坡面出流、坡面流流速、坡面流阻力系数、曼宁糙率、雷诺数、弗劳德数和坡面累积产沙量的影响.结果表明,在粉砂壤土中,相对于无大孔隙试验槽,含有大孔隙的试验槽的坡面阻力系数和曼宁糙率较大,而坡面出流量、坡面初始出流时间、雷诺数、弗劳德数坡面流流速,以及坡面累积产沙量则较小.两坡面流的流态均为层流和缓流,累积产沙量随时间的变化过程可用幂函数描述.

再生水及土壤类型对绿化树种耗水和生长的影响

【目的】探讨再生水合理灌溉城市绿化树种的技术。【方法】以清水灌溉为对照,采用盆栽试验,研究了再生水灌溉对种植在2种土壤质地(砂壤土和粉砂壤土)下的5种绿化树种(云杉、樟子松、侧柏、小叶女贞和白榆)耗水及生长状况变化的影响。【结果】再生水灌溉不会改变不同土壤下各绿化树种的耗水量和Kc值(作物系数)的变化趋势以及耗水量和Kc均值的大小,但可改变小叶女贞的耗水高峰期以及云杉和白榆的Kc峰值时间;除樟子松外,2种水质灌溉下其余4种绿化树种在粉砂壤土中的累积耗水量和Kc值均小于砂壤土,在清水灌溉下云杉、侧柏、小叶女贞和白榆的累积耗水量依次减少13.85%、15.23%、23.27%和8.07%,再生水灌溉下减少17.00%、12.13%、22.48%和11.98%,在清水灌溉下Kc值减少13.51%、15.52%、23.42%和10.21%,再生水灌溉下Kc值减少17.86%、14.54%、20.55%和14.98%;再生水灌溉改变了种植在不同土壤的各绿化树种(除白榆外)株高生长状况,也改变了樟子松和白榆的冠幅生长情况。【结论】清水灌溉下云杉和侧柏适宜在粉砂壤土生长,再生水灌溉下小叶女贞和白榆适宜在砂壤土生长。

阴山北部农牧交错带耕作粉壤土未冻水含量预报模拟研究

本文对内蒙古阴山北部农牧交错带耕作土壤进行了未冻水含量试验,得出了在不同初始含水量情况下的土壤未冻水含量变化曲线。并应用典型预报模型Anderson模型对该区粉壤土未冻水含量进行了预报模拟,并将模拟结果与试验结果进行对比分析,验证了Anderson模型对该区粉壤土未冻水含量模拟的可信度。通过阴山北部耕作土壤粉壤土的未冻水含量试验模拟研究,揭示了该地区粉壤土的冻结特性,明确了冻结粉壤土未动水含量随温度的变化规律,对进一步研究该地区的土壤冻融水热运移、土壤冻融作用下的结构变异、冻结粉壤土的含水量测试提供帮助。

中粉质壤土泥浆泵法修筑淤地坝人工排水管网布设优选研究

以延安市志丹县前拐沟淤地坝筑坝现场修筑的人工试验小区为研究对象,使用土水比为1.0和1.5的泥浆,进行3种管道布设方式(横向管道、竖向管道、横竖向结合管道)、3种灌浆高度(30、60、90cm)下的排水管网优选试验。结果表明,横竖结合管道的排水效果最好,竖向管道次之,且二者差距不大,横向管道最差,实际筑坝中宜优先选用竖向排水管道;在布设竖向管道和布设横竖结合管道2种情况下,管道排水均集中在试验最初的12h内,且同种布设方式管道排水效果受灌浆高度的影响不大,可适当缩短1次灌浆后的静置时间和适当增大灌浆高度以缩短筑坝工期。

钾细菌制剂肥效试验

研究了不同来源的钾细菌制剂及KCl对水稻、小麦等作物生长的促进作用和增产效果。结果表明 ,钾细菌制剂对土壤矿物钾有较强的分解能力 ,在缺钾小粉白土中施用钾细菌制剂对水稻和小麦的生长有促进作用 ,能将更多的土壤无效钾转化为植物可吸收利用的速效钾。如在缺钾土壤中施用钾细菌制剂 ,能提高钾肥和土壤钾的利用率 ,经济效益显著 ,投入产出比达1∶9.2～ 2 2 .5。

大桥台后软基处治设计与施工控制

介绍了淤泥地质台后采用粉喷桩、塑料排水板、土工格栅、反压护道等措施的设计与施工控制,对台后软基处治工程的施工有指导意义。

振动水冲法在海子湾水库除险加固工程中的应用

通过对新疆海子湾水库溢洪道第四系全新统冲洪积松软地基的振冲加固处理以及用土工试验和标准贯入法检测分析，论证了应用振冲法加密粉质壤土，消除其液化的可能性是行之有效的。

黄河堤防粉土增湿变形特性试验研究

对黄河堤防粉土增湿变形特性进行了试验分析,认为:①土料试样在不同的压力下浸水,从膨胀转变为湿陷的界限压力值为330 kPa,当压力值小于25 kPa时,该土样的膨胀量较大;②击实土样的制备含水率对于增湿后膨胀变形的影响很大,在工程实际中应在大于或小于最优含水率时进行试验研究;③不同的粉土土质具有不同的增湿变形特性,应根据工程实际情况,分别针对不同的土质进行增湿胀缩变形试验。

含管状孔隙黄土状重粉质壤土渗透性分析

为正确认识含管状孔隙黄土状重粉质壤土的渗透性，采取了现场水文地质调查，在现场做原位渗透试验，采取大尺寸原状方块样进行室内试验。经分析，发现这种土的渗透性远大于一般的重粉质壤土，多属中等透水性，且渗透性具方向性，竖直向渗透性能远大于水平向渗透性能。所以在进行防渗和基坑降水时，要充分考虑到这种土渗透性与一般重粉质壤土的差异。