Characteristics of land use conversion in soda saline-alkali soil region of central Northeast China

Since the 1970s,the soda saline-alkali soil region,which is located in the semiarid-arid region of the central Northeast China,has experienced drastic climate variability.Meanwhile,human activities and socio-economic development have led to an increase in water consumption.These factors have brought out considerable land use change and a lot of soil salinize-alkalization.The land use types were obtained from remote sensing images interpretation based on Landsat MSS in 1970s,TM,ETM in 1990s and 2010s.The characteristics of land use conversion and its response to climate change and influence of human activities were explored in the study area during 1970-2010.The results include:(1)The land use types had changed significantly,especially farmland and grassland,with annual growth rates of 0.31% and 0.35%,respectively.In terms of the saline-alkali land,the area increased greatly during 1970-1990,and its increase was mainly from grassland.There was a decrease from 1990 to 2010,and the loss of saline-alkali was replaced by farmland and grassland.(2)Climate change in the study area is obvious,showing a trend of decreasing precipitation and increasing temperature.The change of saline-alkali land area is closely related to the precipitation,with R2=0.78,passed a passing the 0.01 significance test.(3)The correlation of land use degree index and human activity index with saline-alkali land was not obvious,and the changes in these indices only reflected the land use patterns.Under sufficient rainfall,the saline-alkali land was developed into farmland by humans,which caused the decrease of the saline-alkali land.Therefore,climate change is the main driving force of land salinization in the study area.

Effects of Biochar and Wood Vinegar on Labile Phosphorus Pool in Soda Saline-Alkaline Soil

A pot experiment was conducted to research the effect of biochar and wood vinegar on labile phosphorus fractions in saline-alkali soil.There were eight treatments,including CK(0 kg•hm-2 biochar+0 kg•hm-2 wood vinegar),C1(0.6 t•hm-2 biochar),C2(0.6 t•hm-2 wood vinegar),C3(1.2 t•hm-2 wood vinegar),C4(1.8 t•hm-2 wood vinegar),C5(0.6 t•hm-2 biochar+0.6 t•hm-2 wood vinegar),C6(0.6 t•hm-2 biochar+1.2 t•hm-2 wood vinegar),and C7(0.6 t•hm-2 biochar+1.8 t•hm-2 wood vinegar).The results showed that biochar without wood vinegar and the co-application of biochar and wood vinegar significantly increased soil total phosphorus content.Meanwhile,compared with CK,all of treatments increased resin phosphorus and sodium bicarbonate-extracted inorganic phosphorus(NaHCO3-Pi)contents in saline-alkali soil.Especially,the contents of resin phosphorus and NaHCO3-Pi under C5,C6,and C7 treatments were higher than those of C2,C3,and C4 treatments,respectively,indicating that the increases of labile phosphorus contents under the co-application of biochar and wood vinegar were better than those of the alone application of biochar and wood vinegar.Each treatment increased the proportion of labile phosphorus pool in saline-alkali soil and the proportion of labile phosphorus pool increased with the increase of the amount of wood vinegar.In addition,the application of biochar and wood vinegar increased the 100-grain weight of rice,and C6 treatment had the best effect,increasing the 100-grain weight by 134.35%.Therefore,the application of biochar and wood vinegar in saline-alkali soil could improve the soil phosphorus availability,increase the weight of rice grains,thereby realizing the resource utilization of agricultural waste and the sustainable development of agriculture.

Effects of different soil amendments on physicochemical property of soda saline-alkali soil and crop yield in Northeast China

Soil amendment is one of the most effective methods to improve saline-alkali soil.In this study,laboratory experiments were conducted to verify the effect of 13 kinds of amendments and their combinations(Citric acid(NM),Phosphogypsum(LS),Aluminum sulfate+citric acid(AL+NM),Aluminum sulfate+phosphogypsum(AL+LS),Aluminum sulfate+citric acid+phosphogypsum(HH),Zeolite(Z),Acidified zeolite(ZH),Aluminum sulfate(AL),Aluminum sulfate+zeolite(AL+Z),Aluminum sulfate+acidified zeolite(AL+ZH),Poly Aluminum chloride(ALCL),Polyaluminium chloride+zeolite(ALCL+Z),Polyaluminium chloride+acidified zeolite(ALCL+ZH))on soil pH,metal cations content,exchangeable Na+,exchangeable sodium percentage(ESP)in the lab.And then the five most effective amendments(Z,ZH,AL,AL+Z,and AL+ZH)were chosen applying both in dry field(maize field)and paddy field to evaluate their improvement on soda saline-alkali soil and crop yield in the northeast Songnen Plain,China.The lab results showed that AL,AL+Z and AL+ZH treatments could significantly reduce the pH in soil solution and increase the content of metal cations.Z and ZH treatments could adsorb metal cations in soil.Both in dry and paddy fields,all five treatments could increase the soil saturated hydraulic conductivity(Ks),increased from 9.63 to 60.02 mm/d and 0.18 to 33.25 mm/d,respectively,of which the AL treatment was the best;all five treatments could reduce the content of exchangeable Na+in soil,and decrease by 38.62%-61.33%and 25.24%-71.53%,respectively,of which the AL+ZH treatment was the best;all treatments could reduce soil exchangeable sodium percentage,and decrease by 0.14-0.22 and 0.14-0.41,respectively,of which the AL+ZH treatment was the best;AL,AL+Z and AL+ZH treatments could improve soil organic matter content;all treatments could effectively improve the yield of crops,and increase 23.98%-60.75%and 52.51%-260.21%,respectively,of which the AL treatment was the best in dry field and the AL+ZH treatment was the best in paddy field.The effect of AL treatment was the best in dry field and AL+ZH treatment was the best in paddy field of soda saline-alkali soil.This study could provide instructive information for the chemical improvement and agricultural utilization of soda saline-alkali soils in the world.

Soil Carbon, Nitrogen and Phosphorus Concentrations and Stoichiometries Across a Chronosequence of Restored Inland Soda Saline-Alkali Wetlands, Western Songnen Plain, Northeast China

Soil carbon(C), nitrogen(N) and phosphorus(P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon(SOC), total nitrogen(TN), and total phosphorus(TP) pools, for a chronosequence of three restored wetlands(7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C∶N(RC N), C∶P(R CP), and N∶P(R NP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr(P > 0.05). Soil nutrients changes occurred mainly in the upper layers(≤ 30 cm), and no significant differences were found in deeper soils(> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RC N, R CP, and RN P in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC(r =-0.704, P < 0.01), TN(r =-0.722, P < 0.01), and TP(r =-0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

Strength Model of Soda Residue Soil Considering Consolidation Stress and Structural Influence

Soda residue(SR)is a type of industrial waste produced in the soda process with the ammonia-soda method.Applying SR to backfilling solves the land occupation and environmental pollution problems in coastal areas and saves material costs for foundation engineering.The strength characteristics of soda residue soil(SRS)under different consolidation conditions are the key points to be solved in the engineering application of SRS.Triaxial compression tests were performed on the undisturbed SRS of Tianjin Port.The shear properties of SRS under different consolidation conditions were then discussed.Meanwhile,a structural strength model(SSM)based on Mohr-Coulomb theory was proposed.SSM reflects the influence of soil structure on undrained strength(Cu)and divides the Cu into the following two parts:friction strength(C_(uf))and original structural strength(C_(u0)).C_(uf)characterizes the magnitude of friction between soil particles,which is related to the consolidation stress.Meanwhile,C_(u0)represents the structural effect on soil strength,which is related to the soil deposition and consolidation processes.SSM was validated by the test data of undisturbed soils.Results reveal that the undisturbed soil generally had a certain C_(u0).Therefore,the SRS strength model was established by combining the experimental law of SRS with SSM.Error analysis shows that the SRS strength model can effectively predict the Cu of undisturbed SRS in Tianjin Port under different consolidation conditions.

A STUDY ON GROWTH OF PLANTATION ON SODA-SALINE-ALKALI SOIL

If some suitable treatments are used plantations can be grown and established on the soil of soda-saline-alkali with the soil condition of PH 8.5- 9.6, salinity 0.1-0.3% and normality ratio of saline base Na+ / ( Ca+++ Mg++)≥4. From the results of plot inventory and tree stem analysis, the increment of Poplus simonigra is highest. For 9 years, the volume can reach 100 m3/ha, the biomass (above ground) can reach 28.7 ton/ha. Poplus simonigra grows very well on the all kinds of soda-saline-alkali soils except for the alkali spot with the worst soil condition. So Poplus simonigra is a good tree species for planting on the soil of soda-saline-alkali.

Planting six tree species on soda-saline-alkali soil

Populus simonigra， Salix matsudana， Ulmus pumila， Populus nigra， Acer negundo， Fraxinus mandshurica。Tamarix chinensis， Hippophae rhammoldes， Syriga onlata 在 soda-saline-alkali 上被种。土壤有 pH 8.5 鈥 ?.6，咸度 0.1% 鈥 ?.3% ， sodiumionized 比率 16% 鈥 ?1% 并且盐的基础 Na+/(Ca+++Mg++) 的规度比率 > 4。除了在碱运动上， Populus simonigra 与最糟的土壤条件在各种 soda-saline-alkali 土壤上成长很好并且显示出一根高木头增长和生物资源。在 9 以后一，体积能到达 100 m3/hm2，并且未葬生物资源罐头重新拱 28.7 t/hm2。

Present situation and tendency of saline-alkali soil in west Jilin Province

Taking west Jilin Province as an example, this paper put forward the assessment index of salinization, and based on it, the authors present the distribution characteristics of saline-alkali soil in the 1980s and the 1990s in west Jilin and analyze its physical and chemical properties in detail. The developing tendency of salinization was also inferred by comparing the saline-alkali soil of the 1980s with that of the 1990s. Finally, the natural and human factors leading to salinization are analyzed.

Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China

Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0–200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops.

Microbial diversity in the saline-alkali soil of a coastal Tamarix chinensis woodland at Bohai Bay, China

Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of y-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.

Quantitative Analysis of Relationships Between Crack Characteristics and Properties of Soda-saline Soils in Songnen Plain, China

The Songnen Plain has a typical soda-saline soil, which often shrinks and cracks under natural conditions during water evaporation. This study aims to analyze the relationships between the crack characteristics and the soil properties of soda-saline soils quantitatively, and attempts to establish prediction models for the main soil properties of soda-saline soils based on the results. In order to achieve these objectives, a desiccation cracking test was conducted using 17 soil specimens with different salinity levels under controlled laboratory conditions. Correlation analysis was then performed between the crack characteristics and the soil properties. The results indicate that the crack characteristics can well represent the surface appearances of cracked soils, they also can well distinguish the salinity levels of soda-saline soils while the clay contents and mineralogical compositions of soils are stable. Among the crack characteristics, crack length has the best relationships with the salinity levels of soda-saline soils. Specifically, the crack length has high correlation(R2 > 0.87) with the electrical conductivity(EC), Na+, CO32– and the salinity, it also has reasonable relationship(R2 > 0.68) with HCO3–, this indicates crack length can be well used for the prediction of these properties of soda-saline soils.

Studies on Fast Remediation of Soda Meadow Alkaline Soil

Researches on models of remediation quickly in soda meadow alkaline soil, and dynamic variation of water-salt in saline soil of Zhaozhou County were studied systematically from 2001 to 2006. Realize the vegetation cover of those years through the artificial planting, mixed seeding lyme grass （Elymus dahuricus Turcz） and melilot in the mode of rotary tillage and deep loosening in lower and medium saline soils. The results showed that there was remarkable relationship between net evaporation （difference of precipitation and evaporation） and total salt content in the soil. The net evaporation could be used as a new method to forecast the dynamics variation of salt to ensure the pasture optimum sowing time. Realize the autumnal vegetation cover of those years through direct planting on the bourgeon layer of soda meadow alkaline soil, on the other hand, the covered pasture made the function of restraining salt and alkaline content to realize the biology reverse succession quickly. Forage seeds were seeded directly on the seeding bed of soda alkaline meadow at the end of July. In fall of the same year, a certain amount of biomass was obtained. The model, which has remarkable economical efficiency and use widely, represented the innovative model for the fast vegetation restoration on the soda alkaline meadow soil.

Effects of Different Halophytes on Soil Microflora and Enzyme Acti-vities of Saline-alkali Soil

In the pot experiment,seven varieties of halophytes were grown in saline-alkali soil to investigate the responses of microflora and soil enzymes in the rhizosphere.The results showed that compared to the control,the population of bacterial colony(84.8%-95.6%),actinomycetes colony(12.0%-14.5%)and fungi colony(0.5%-1.1%)increased significantly(P<0.05).The population of ammonia bacteria,aerobic cellulose decomposition bacteria in the soil of Vicia sativa L.(201.99%and 395.49%),Medicago sativa(152.43%and 319.90%)and Sesbania cannabina(Retz.)Pori(193.14%and 396.08%)were higher significantly than that of Panicum virgatum L.(49%and 60%),Sorghum bicolor(L.)Moench(99%and 210%),Amaranthus hypochondriacus L.(75%and 36%)and Aneurotepidimu chinense(75%and 77%)(P<0.05).However,Sorghum bicolor(L.)Moench was evidently higher than Panicum virgatum L.,Amaranthus hypochondriacus L.and Aneurotepidimu chinense(P<0.05)in the soil.The population of ammonia bacteria and aerobic cellulose-decomposing bacteria was significantly correlated with the five enzymes(P<0.05),which could improve the microenvironment in saline-alkali soil to accelerate the element cycling and promote the sustainable development of agriculture through cultivating Medicago sativa,Vicia sativa L.,Sesbania cannabina(Retz.)Pori and Sorghum bicolor(L.)Moench.

Relationship between spatio-temporal evolution of soil pH and geological environment/surface cover in the eastern Nenjiang River Basin of Northeast China during the past 30 years

To illuminate the spatio-temporal variation characteristics and geochemical driving mechanism of soil pH in the Nenjiang River Basin,the National Multi-objective Regional Geochemical Survey data of topsoil,the Second National Soil Survey data and Normalized Difference Vegetation Index(NDVI)were analyzed.The areas of neutral and alkaline soil decreased by 21100 km^(2)and 30500 km^(2),respectively,while that of strongly alkaline,extremely alkaline,and strongly acidic soil increased by 19600 km^(2),18200 km^(2),and 15500 km^(2),respectively,during the past 30 years.NDVI decreased with the increase of soil pH when soil pH>8.0,and it was reversed when soil pH<5.0.There were significant differences in soil pH with various surface cover types,which showed an ascending order:Arbor<reed<maize<rice<high and medium-covered meadow<low-covered meadow<Puccinellia.The weathering products of minerals rich in K_(2)O,Na_(2)O,CaO,and MgO entered into the low plain and were enriched in different parts by water transportation and lake deposition,while Fe and Al remained in the low hilly areas,which was the geochemical driving mechanism.The results of this study will provide scientific basis for making scientific and rational decisions on soil acidification and salinization.

Effects of Soil Improver on Wheat in Saline-Alkali Lands in the Yellow River Delta

Field experiment carried out to test the effects of soil improver on wheat yield and soil physical-chemical properties. The results indicated that soil improver could optimize soil aggregates structure, decrease soil bulk density, soil pH and soil salt content, increase soil organic matter and 1 000-grain weight, thereby enhancing wheat yield. With the increase of soil improver application amount, soil physical-chemical properties became better and wheat yield increased. However, there was no significant difference in the treatments with the application amounts of 3%, 4% and 5%. In addition, the treatment of reducing nitrogen showed no superiority in soil physical-chemical properties and wheat yield, indicating that sufficient nitrogen was essential for the growth of wheat.

Significant changes in arbuscular mycorrhizal community and soil physicochemical properties during the saline-alkali grassland vegetation succession

Arbuscular mycorrhizal(AM)fungi are widely distributed in various habitats,and the community composition varies in response to the changing environmental conditions.To explore the response of community composition to the succession of saline-alkali land,soil samples were collected from three succession stages of Songnen saline-alkali grassland.Subsequently,the soil characteristics were determined and the AM fungi in soil samples were analyzed by high-throughput sequencing.Then,the response relationship between community composition and soil characteristics was studied by Canonical correlation and Pearson analyses.The soil properties improved with the succession of saline-alkali grassland.There was no significant difference in alpha diversity between the first and second succession stage(Suaeda glauca and Puccinellia tenuiflora,respectively),and the microbial community had a dense association network at the third stage(Leymus chinensis);in addition,each succession stage had significantly enriched amplicon sequence variants(ASVs)and functional pathways.All the soil properties except cellulase activity had significant effects on community composition.Furthermore,the pH,organic carbon,organic matter,and sucrase activity significantly correlated with alpha diversity indices.These results provide a theoretical basis for realizing the significant changes in AM fungal community and soil properties during the saline-alkali grassland vegetation succession.

Influences of Soda Soil on the Ultrastructure and Storage Inclusions of Chloroplasts of <i>Syringa oblata</i>Lindl.

With a high pH value, soda soil restricts the growth of plants. It had previously been assumed that the inhibition of plant growth by neutral salt stress was partly due to the changes of the ultrastructure and storage inclusions of chloroplasts. The aim of this paper is to investigate the effects of alkali-salt mixed stress of soda soil on chloroplasts of higher plant Syringa oblata Lindl. Testing S. oblata plants had grown for more than five years in soda soil, and transmission electron microscope was used for determining the ultrastructure and storage inclusions of chloroplasts. The results showed that some chloroplasts were destroyed, the normal chloroplasts became smaller, and the envelopes of the functional chloroplasts were slightly expanded generally in soda-stressed plants. The most noteworthy fact was that much more starchgrains accumulated in the chloroplasts of S. oblata growing in soda soil than in neutral soil. The total contents of plastoglobules in chloroplasts did not change considerably, and plastoglobules with different electron densities appeared in chloroplasts in the plants growing in soda soil. We presume that the reduction of the volume and number of functional chloroplasts and the occupation of carbon resources by starch grains accumulated in chloroplasts were the possible reasons for the inhibition of S. oblata growth by soda soil. The accumulation of starch grains was one of the adaptive traits of S. oblata, which promoted the survival of plants in soda soil for that the starch grains could serve as a steady source of soluble sugars, which were known as protectors of plant cells under stressed conditions. Soda soil did not significantly change the total content of plastoglobules in chloroplasts, but changed their compositions.

Arbuscular Mycorrhizal Fungal Colonization at Different Succession Stages in Songnen Saline-Alkali Grassland

Arbuscular mycorrhizal(AM)fungi can form symbiosis with 90%of the vascular plants and play important roles in ecosystem.To realize the AM fungal colonization at different succession stages in saline-alkali land and screen AM fungi species with great functions,roots and soil samples were collected from the three succession stages of Songnen saline-alkali grassland.The soil properties and AM fungal colonization were measured,and the fungus distributed extensively in three stages was annotated by sequencing for AML1/AML2 target,subsequently,maize was selected as the host to verify its colonization.The results showed that the soil properties improved with the succession of saline-alkali grassland.The plants’communities of the three stages could be colonized by AM fungi,and the colonization rate of Leymus chinensis(the third stage)ranged from 66.67%to 100%,Puccinellia tenuiflora(the second stage)ranged from 50%to 80%,while the Suaeda glauca(the first stage)was only 35%–60%.Glomeraceae sp1 was identified as the dominant AM fungi species which occurred frequently in the succession of saline-alkali land with the isolation frequency,relative abundance,and importance value of 100%,18.1%,and 59.1%,respectively.The colonization rate of Glomeraceae sp1 in maize ranged from 80%to 87%and similar mycorrhizal characteristics were detected in the roots of P.tenuiflora,S.glauca,and L.chinensis,indicating that Glomeraceae sp1 colonized the samples in the field.The correlation matrix indicated that colonization rate,colonization intensity,and vesicle abundance were closely related to soil conditions most,and they were related significantly to all the soil properties except cellulase activity.Besides,redundancy analysis(RDA)showed that soil properties drove the changes of AM fungal colonization and sporulation.These results will provide theoretical support for realizing the relationship between AM fungal colonization and soil conditions,and also for the exploration of AM fungi species with great functions.

考虑地下水位影响的碱渣土地基半埋混凝土内氯离子传输试验研究

关于碱渣土地基环境下钢筋混凝土结构耐久性问题,尚未见相关研究成果,是有待研究的课题。为探究碱渣土地基混凝土内氯离子传输规律,本工作模拟真实碱渣土地基及地下水侵蚀环境,设计了三种地下水位-0.2 m、-0.5 m、-0.8 m,开展半埋于碱渣土地基的混凝土氯离子自然扩散试验,探究不同地下水位环境下混凝土地表吸附区及地下区域的氯离子分布规律。结果表明,地表吸附区由于其蒸发浓缩及毛细作用,氯离子浓度高于地下区域。氯离子浓度随地下水位的变化呈现较大差异,地表吸附区氯离子浓度随地下水位的升高呈下降趋势,地下区域地下水位的影响主要体现在试件与水位的相对位置,地下水位以下区域氯离子浓度高于地下水位以上区域。在此基础上,探究碱渣土地基半埋混凝土内氯离子传输机理,基于Fick第二定律定量研究了地下水位对表面氯离子浓度及扩散系数的影响,建立考虑地下水位影响的氯离子传输时变模型,通过与实测结果对比印证了模型的正确性,本模型可为实际工程中定量评估不同碱渣土侵蚀环境下混凝土内氯离子浓度以及服役寿命预测提供技术支持。

秸秆还田对苏打盐碱土pH、电导率及玉米生长的影响

通过田间试验,分析玉米秸秆不同还田方式对苏打盐碱土pH、电导率及玉米生长的影响。结果表明,在作物整个生长阶段内,处理HCS与FCS中0~20 cm土壤pH均低于CK,但30~50 cm略高于CK;处理HCS与FCS中各层土壤EC均低于CK;相比CK,处理HCS与FCS玉米株高、茎粗、穗位高、穗长、穗粗均增加;二者产量分别比CK高6.70%和18.25%。综上,秸秆还田可有效减轻苏打盐碱土的碱害和盐害,促进玉米生长,提高产量,玉米秸秆还田量为1.2 t/hm^(2)的作用效果优于还田量为0.6 t/hm^(2)。