Improved Prediction and Reduction of Sampling Density for Soil Salinity by Different Geostatistical Methods

The spatial estimation for soil properties was improved and sampling intensities also decreased in terms of incorporated auxiliary data. In this study, kriging and two interpolation methods were proven well to estimate auxiliary variables： cokriging and regression-kriging, and using the salinity data from the first two stages as auxiliary variables, the methods both improved the interpolation of soil salinity in coastal saline land. The prediction accuracy of the three methods was observed under different sampling density of the target variable by comparison with another group of 80 validation sample points, from which the root-mean-square error （RMSE） and correlation coefficient （r） between the predicted and measured values were calculated. The results showed, with the help of auxiliary data, whatever the sample size of the target variable may be, cokriging and regression-kriging performed better than ordinary kriging. Moreover, regression-kriging produced on average more accurate predictions than cokriging. Compared with the kriging results, cokriging improved the estimations by reducing RMSE from 23.3 to 29% and increasing r from 16.6 to 25.5%, regression-kriging improved the estimations by reducing RMSE from 25 to 41.5% and increasing r from 16.8 to 27.2%. Therefore, regression-kriging shows promise for improved prediction for soil salinity and reduction of soil sampling intensity considerably while maintaining high prediction accuracy. Moreover, in regression-kriging, the regression model can have any form, such as generalized linear models, non-linear models or tree-based models, which provide a possibility to include more ancillary variables.

Effect of Sample Temperature on Radiation Characteristics of Nanosecond Laser-Induced Soil Plasma

An Nd:YAG single pulse nanosecond laser of 532 nm wavelength with an 8 ns pulse width was projected on the soil samples collected from the campus of Bengbu College under 1 standard atmospheric pressure. Laser-induced breakdown spectroscopy at different sample temperatures was achieved. The intensity and signal-to-noise ratio (SNR) changes of different characteristic spectral lines could be analyzed when the sample temperature changes.The evolution of plasma electron temperature and electron density with the sample temperature was analyzed through Boltzmann oblique line method and Stark broadening method.The cause of the radiation enhancement of laser-induced metal plasma was discussed. Experimental results demonstrated that the spectral intensity, SNR, the electron temperature and electron density of plasma are positively related to the sample temperature, and reach saturation at 100℃.

Stability of soil organic carbon changes in successive rotations of Chinese fir(Cunninghamia lanceolata(Lamb.) Hook) plantations

The importance of soil organic carbon （SOC） under forests in the global carbon cycle depends on the stability of the soil carbon and its availability to soil microbial biomass. We investigated the effects of successive rotations of Chinese fir （Cunninghamia lanceolata （Lamb.） Hook） plantations on the stability of SOC and its availability to microbes by adopting the two-step hydrolysis with H2SO4 and density fractionation. The results showed that successive rotations of Chinese fir decreased the quantity of total SOC, recalcitrant fraction, and carbohydrates in Labile Pool I （LPI）, and microbial properties evidently, especially at 0-10 cm horizon. However, cellulose included in Labile Pool Ⅱ （LP Ⅱ） and the cellulose/total carbohydrates ratio increased in successive rotations of Chinese fir. The noncellulose of carbohydrates included in LPI maybe highly available to soil microbial biomass. Hence the availability of SOC to microbial biomass declined over the successive rotations. Although there was no significant change in recalcitrance of SOC over the successive rotations of Chinese fir, the percentage of heavy fraction to total SOC increased, suggesting that the degree of physical protection for SOC increased and SOC became more stable over the successive rotations. The degradation of SOC quality in successive rotation soils may be attributed to worse environmental conditions resulted from disturbance that related to ＂slash and burn＂ site preparation. Being highly correlated with soil microbial properties, the cellulose/total carbohydrates ratio as an effective indicator of changes in availability of SOC to microbial biomass brought by management practices in forest soils.

Applications of Soil Series in Sustainable Land Use of Oasis Farmlands

The issue of agricultural land sustainability is important to every part of the world, especially in the developing countries. Based on the data collected by field investigation and laboratory analysis as well as soil classification theory, the authors discuss the applications of soil series in the arid northwestern China. On the one hand, the application in the layout of rational agricultural of oasis farmlands: (1) two soil series,namely,Lanjiabao (main) and Nijiaxiaying, belong to the moderate and extremely arid region in the study area; accordingly, the layout of crops is the spring wheat and maize (main) and winter wheat;(2) Nijiaxiaying (main) and Lanjiabao, however, fall into the warm-cold and extremely arid region, where the winter wheat (main) and spring wheat grow; and (3) the Shangfusi is part of the warm chilly-arid region, which is used as seasonal pastureland. On the other hand, the application on the soil quality of oasis farmlands, the results indicating that among all soil series, the content of N is very low, however, the content of K is abundant, and the content of P is greatly scarce.

Effect of Terrestrial LiDAR Point Sampling Density in Ephemeral Gully Characterization

Gully erosion can account for significant volumes of sediment exiting agricultural landscapes, but is difficult to monitor and quantify its evolution with traditional surveying technology. Scientific investigations of gullies depend on accurate and detailed topographic information to understand and evaluate the complex interactions between field topography and gully evolution. Detailed terrain representations can be produced by new technologies such as terrestrial LiDAR systems. These systems are capable of collecting information with a wide range of ground point sampling densities as a result of operator controlled factors. Increasing point density results in richer datasets at a cost of increased time needed to complete field surveys. In large research watersheds, with hundreds of sites being monitored, data collection can become costly and time consuming. In this study, the effect of point sampling density on the capability to collect topographic information was investigated at individual gully scale. This was performed through the utilization of semi-variograms to produce overall guiding principles for multi-temporal gully surveys based on various levels of laser sampling points and relief variation (low, moderate, and high). Results indicated the existence of a point sampling density threshold that produces little or no additional topographic information when exceeded. A reduced dataset was created using the density thresholds and compared to the original dataset with no major discrepancy. Although variations in relief and soil roughness can lead to different point sampling density requirements, the outcome of this study serves as practical guidance for future field surveys of gully evolution and erosion.

Water Quality Index of Waste Stabilisation Ponds and Downstream of Discharge Point

Water quality index has been used in various researches for the assessment of water quality for various uses and discharges into the environment. The purpose of this study was to determine the water quality index of the effluent from waste stabilisation ponds and 400 m beyond discharge point. This was achieved by evaluating concentrations of seven parameters from soil, eleven physiochemical parameters from effluent and four microbiological parameters. Corresponding water quality indices calculated from microbiological parameters were 854, 142, 96 and 1539 respectively, at sites 1, 2, 3 and 4. Reductions of magnesium, zinc, lead, sodium adsorption ratio, sodium and electrical conductivity in soil samples at site 4 were 15.5%, 57%, 81.6%, 93.5%, 93.5% and 99% respectively. The percentage increases were 21.4% and 185% respectively, for calcium and iron ions. It can be concluded that the water quality index of the waste stabilisation ponds is unsuitable for discharge into the environment. However, the results revealed improved quality downstream of discharge point.

Research on Influencing Factors of Spatial Variation of Soil Nutrients

Based on previous studies,the research methods and influencing factors of spatial variation of soil nutrients are summarized.It is concluded that the spatial variation of soil nutrients is studied generally by geostatistics methods,and the spatial distribution of nutrients is visually observed by using Kriging interpolation method.The influencing factors mainly include topography,sampling method,sampling spacing,sampling density and sampling scale.The influence of random sampling and grid sampling on interpolation is analyzed based on the specific conditions of the actual study area.The influence of sampling density and topography on the spatial variation of soil nutrients cannot be ignored,especially on available nutrients.When samples are collected in a large area(under a small and medium scale),the spatial variation of soil nutrients is large,and they have strong spatial autocorrelation;in a small area(namely under a large scale),the spatial variability of soil nutrients is small,and they have obvious spatial autocorrelation.This study can provide intuitive and convenient reference materials for the following researchers.

Effects of Soil-Cement Stabilization on the Index Properties of Subgrades of Three Selected Roads in the Niger Delta Region of Nigeria

In this study, the impact of soil-cement stabilization on the index properties of the subgrade of roads was investigated. Efforts were on the means of improving the bearing capacity of the subgrade of a flexible pavement structure. Three selected roads (Ogbia-Nembe, section of the East-West Road and section of Port Harcourt-Aba Road) in the Niger Delta Region of Nigeria were examined to determine the effect of sand-cement stabilization on the compaction index property of their undisturbed subgrade and the optimal ratio of soil-cement on the expansive soils at which the California Bearing Ratio (CBR) is optimized. Disturbed soil samples were collected from twenty trial pits on each of the three study roads using a hand ulger and tested for their respective compaction index properties. It was discovered that their California Bearing Ratio (CBR) was very low. Some of the collected specimen materials were stabilized with varying percentages of soil-cement contents ranging from 6% - 14% in order to ascertain its effects on the compaction index properties of the sample soils. Results of the various stabilization test procedures show that: Stabilization of the soil using Soil-Cement Stabilization affected the Compaction Index properties of the soil and further improved the California Bearing Ratio (CBR). On the Ogbia-Nembe Road;Soil-Cement stabilization improved the CBR and is optimized at a 10% sand-cement ratio with optimum moisture content ranging from 6.2% - 14%, maximum dry density ranges from 1700 - 1780 kg/m3, yielding an average CBR of 42.7% for soaked samples. On the section of East-West Road from Eleme Junction to Etteh Junction;Soil-Cement stabilization improved the CBR and is optimized at a 14% sand-cement ratio with optimum moisture content ranging from 6.2% - 14.2%, maximum dry density ranges from 1660 - 1800 kg/m3, yielding an average CBR of 43.9% for soaked samples. On the section of Port Harcourt-Aba Express Road from Eleme Junction to Osisioma Junction;Soil-Cement stabilization improved the CBR and is optimized at a 12% sand-cement ratio having an optimum moisture content ranging from 5.4% - 17.3%, maximum dry density ranges from 1610 - 1740 kg/m3, and an average California Bearing Ratio for soaked samples at 40%.

Soil Quality Mapping Studies Using Nematodes as Bioindicators

Soil quality is one of the most important factors in sustaining the global biosphere and developing sustainable agricultural practices. Land use and management practices greatly impact the direction and degree of soil quality changes in time and space. Understanding the effects of land use and management practices on soil quality and its indicators has been identified as one of the most important goals for modern soil science. Soil quality mapping study represents a method for assessing and mapping soil quality changes in time and space in small units. For the present study, changes in the physical, chemical parameters and nematode density of the soils in the rural and urban areas of Thiruvananthapuram district, Kerala, were determined. The soil samples were collected from seven different categories of contaminated soils namely coastal area, sewage disposal area, industrial area, road-side area, agricultural area, market area and gasoline station area, and also from two control stations in rural and urban areas. The soil physico-chemical parameters and nematode density were determined. Geostatistics combined with GIS was applied to analyze the spatial variability of soil physico-chemical characteristics and nematode density. This soil quality mapping study provides a basis for identifying tension zones and serves as a triggering mechanism for implementation of soil contamination mitigating strategies.

不同无土栽培处理对东方百合‘Siberia’籽球生长的影响

东方百合籽球抗逆性差,田间土壤栽培易感染病虫害,种球年生长量小。为提高种球质量,缩短繁育周期,开展籽球无土栽培技术研究,建立东方百合种球无土栽培繁育技术体系。[方法]以东方百合‘Siberia’为试验材料,采用单因素随机区组设计,探讨不同栽培基质配方、栽培密度、水溶性肥对百合籽球生长的影响。[结果]东方百合籽球无土栽培最佳基质配方为进口草炭∶珍珠岩=3∶1,最适宜无土栽培密度为100粒/箱,生长期施花无缺水溶性肥2000 mg/L最有利于籽球的生长。[结论]筛选出东方百合籽球无土栽培最佳基质配方、栽培密度、肥料种类和浓度,为东方百合籽球规模化生产提供参考。

不同灌溉水源对高原夏芹菜土壤理化性质及其产量、品质的影响

以芹菜品种文图拉为试材,研究引洮水及其引洮水和浅层地下水交替灌溉、浅层地下水3种不同灌溉水源对土壤容重、土壤温度及夏芹菜产量及品质的影响。结果表明,灌溉水质对耕层内(0~30 cm)土壤容重的影响较大,用浅层地下水灌溉后土壤容重增幅最大;在夏芹菜生育期内,土壤温度变化受灌溉水质和气温影响较大,其中引洮水灌溉后生育期土壤平均温度21.4℃,较地下水灌溉高0.7℃;在全生育期灌溉制度相同的条件下,因地下水含氮、磷等有机物较多,灌溉处理夏芹菜产量最高,达135870 kg·hm^(-2),比引洮水灌溉增产21005 kg·hm^(-2),但芹菜粗纤维含量高,食用品质降低。综上,使用矿化度低的引洮水灌溉芹菜,能使土壤保持较好的理化性质,提高芹菜发芽期土壤表层平均地温,有利于芹菜根系的呼吸和生长,易形成茎,能增加芹菜茎秆鲜质量的比例,达到80.79%。

Regional Simulation of Soil Organic Carbon Dynamics for Dry Farmland in East China by Coupling a 1:500000 Soil Database with the Century Model

Changes in soil organic carbon (SOC) in agricultural soils influence soil quality and greenhouse gas concentrations in the atmosphere. Dry farmland covers more than 70% of the whole cropland area in China and plays an important role in mitigating carbon dioxide (CO2) emissions. In this study, 4109 dry farmland soil polygons were extracted using spatial overlay analysis of the soil layer (1:500000) and the land use layer (1:500000) to support Century model simulations of SOC dynamics for dry farmland in Anhui Province, East China from 1980 to 2008. Considering two field-validation sites, the Century model performed relatively well in modeling SOC dynamics for dry farmland in the province. The simulated results showed that the area-weighted mean soil organic carbon density (SOCD) of dry farmland increased from 18.77 Mg C ha1 in 1980 to 23.99 Mg C ha1 in 2008 with an average sequestration rate of 0.18 Mg C ha1 year?1. Approximately 94.9% of the total dry farmland area sequestered carbon while 5.1% had carbon lost. Over the past 29 years, the net SOC gain in dry farmland soils of the province was 19.37 Tg, with an average sequestration rate of 0.67 Tg C year1. Augmentation of SOC was primarily due to increased consumption of nitrogen fertilizer and farmyard manure. Moreover, SOC dynamics were highly differentiated among dry farmland soil groups. The integration of the Century model with a fine-scale soil database approach could be conveniently utilized as a tool for the accurate simulation of SOC dynamics at the regional scale.

Estimates of Soil Organic Carbon Stocks in Zhejiang Province of China Based on 1:50000 Soil Database Using the PKB Method

Soil organic carbon(SOC) is an important component of farming systems and global carbon cycle. Accurately estimating SOC stock is of great importance for assessing soil productivity and modeling global climate change. A newly built 1:50 000 soil database of Zhejiang Province containing 2 154 geo-referenced soil profiles and a pedological professional knowledge-based(PKB) method were used to estimate SOC stock up to a depth of 100 cm for the Province. The spatial patterns of SOC stocks stratified by soil types,watershed(buffer analysis), topographical factors, and land use types were identified. Results showed that the soils in Zhejiang covered an area of 100 740 km2 with a total SOC stock of 831.49 × 106 t and a mean SOC density of 8.25 kg m-2, excluding water and urban areas. In terms of soil types, red soils had the highest SOC stock(259.10 × 106t), whereas mountain meadow soils contained the lowest(0.15 × 106t). In terms of SOC densities, the lowest value(5.11 kg m-2) was found in skel soils, whereas the highest value(45.30 kg m-2) was observed in mountain meadow soils. Yellow soils, as a dominant soil group, determined the SOC densities of different buffer zones in Qiantang River watershed because of their large area percentage and wide variation of SOC density values.The area percentages of various soil groups significantly varied with increasing elevation or slope when overlaid with digital elevation model data, thus influencing the SOC densities. The highest SOC density was observed under grassland, whereas the lowest SOC density was identified under unutilized land. The map of SOC density(0–100 cm depth) and the spatial patterns of SOC stocks in the Province would be helpful for relevant agencies and communities in Zhejiang Province, China.

广东离子吸附型稀土矿床特征及找矿预测

稀土是我国的优势矿种,尤以华南地区离子吸附型稀土矿产资源最为突出,广东省内的风化壳离子吸附型稀土矿床主要分布在韶关、河源、梅州、清远、潮州、揭阳、肇庆和茂名等地。水系沉积物地球化学异常是圈定矿床找矿远景区最有效且快速的一种手段,本次研究以广东省1∶20万水系沉积物地球化学数据为基础,将镧(La)和钇(Y)分别作为轻稀土(LREE)和重稀土(HREE)的特征元素,选取了34处稀土异常调查区(其中LREE异常区15处,HREE异常区19处),通过对人工剥土和人工冲击钻采样分析,初步评估了相应的稀土成矿潜力。139件样品分析结果显示,114个样品达到边界品位(≥0.02%),占送样总数的82.0%;71个样品达到工业品位(≥0.04%,最高可达0.27%),占送样总数的51.1%,新发现韶关乳源、潮州钱东、汕尾碣石、河源东源和河源龙川5个找矿远景区。为了更有效地圈定离子吸附型稀土矿床,结合稀土矿床找矿预测的标志,建议在1∶20万水系沉积物稀土元素地球化学异常区的基础上,开展低密度不规则网土壤地球化学测量,进一步浓缩异常范围并圈定离子吸附型稀土矿床找矿远景区,系统建立稀土资源潜力评价体系。

黑龙江省水土保持方案质量抽查实践与思考

为加强水土保持事中事后监管,基于工作实践,黑龙江省采用专家打分法,综合考虑数量、行业类别、监管重点、方案级别、许可方式等,抽取2018—2022年市、县批复的116个生产建设项目水土保持方案进行了质量抽查。结果表明:方案总体质量较好,中等及以上方案有111个,合格率达到95.69%,不合格方案有5个,不合格率为4.31%;2021—2022年的水土保持方案质量优于2018—2020年的,2021—2022年大部分方案存在缺少现场调查情况、水土保持措施针对性不强等问题,但在表土保护、土石方综合利用、取弃土场选址等方面的质量明显高于2018—2020年的;市、县两级水土保持方案质量情况基本一致,建议在水土保持方案评审中,邀请至少3位以上的省级专家进行质量把关;铁路、输变电、机场、水利等项目水土保持方案质量整体优于其他行业项目,大型项目的方案质量较高,建议对方案质量不高的项目,加强质量把控,即前期严格审查、后期加强监管。

基于碾压应力的土石坝料压实质量控制方法

坝料压实质量是土石坝施工质量控制的关键内容。在长河坝填筑现场进行碾压应力测试,建立土应力与坝料干密度关系模型,得出对应压实密度标准的土应力控制值;构建Midas三维有限元分析模型,模拟坝料碾压过程中的应力动态变化,根据土应力控制值来判断坝料压实质量。研究结果表明:坝料土应力与干密度之间存在较强的线性关系,其线性模型平均决定系数为0.9;对应坝料干密度控制标准,反滤料1上层、中层、下层土体的应力控制值分别为1.465、1.064、0.773 MPa,反滤料3上层、中层、下层的土体应力控制值分别为0.926、0.774、0.664 MPa;运用构建的Midas模型实时监测碾压应力变化,可知反滤料1和反滤料3分别在振碾6遍和8遍后整体达到压实密度标准。

宁波地区长期非粮化生产对耕层土壤理化性质的影响

本研究旨在探究宁波地区长期非粮化生产对耕层土壤理化性质的影响,为非粮化耕地的恢复利用提供参考依据。通过比较采集的全市130个非粮化耕地和53个对照样地的土壤样品,并结合地貌类型(水网平原、滨海平原、丘陵山区、河谷平原)和非粮化种植类型(苗木、果树)进行了系统分析。结果表明:非粮化耕地的土壤pH、有机质含量、土壤容重分别为5.74±0.83、24.72±8.01 g/kg和1.28±0.05 g/cm^(3),分别显著低于或高于周边水田的6.17±1.02、30.07±10.68 g/kg和1.18±0.05 g/cm^(3)(P<0.05)。不同地貌类型条件下,非粮化生产对耕层土壤理化性质的影响存在差异,其中对丘陵山区和河谷平原的耕地产生影响较大,导致土壤EC值、有机质和全氮含量均下降10%以上,土壤pH下降至酸性水平(pH<5.5)。2种非粮化生产方式(苗木和果树种植)均会不同程度导致土壤pH、EC值、CEC值、有机质和全氮含量下降与土壤容重上升,但苗木种植的影响程度均要大于果树种植,其中非粮化苗木地的有机质含量为22.90±7.18 g/kg,显著低于非粮化果园和对照样地的30.07±10.68 g/kg和26.87±8.44 g/kg(P<0.05)。研究表明,宁波地区长期非粮化生产导致土壤酸化、地力下降和土壤紧实度提高等问题,同时非粮化耕地的恢复利用应充分考虑地貌类型和非粮化种植类型等因素差异。

某建筑物沉降突变原因分析及对预制管桩工程相关问题的反思

通过对某建筑物沉降突变的后果呈现和原因分析,印证了基桩上浮的可能性和危害性。为有效检出上浮桩,对抽样检测的可靠度进行了理论分析,计算出在各种情况下的漏检概率。另外还以本工程为例讨论了低应变法的有效检测深度问题,从而对现行规范中的检测方法和抽检数量提出了修订建议。最后,为减小基桩上浮现象,对接桩质量、收锤标准、挤土效应等问题提出了相应的质量控制对策。

土壤检测相关质量控制技术应用研究

本研究旨在探索土壤检测中的质量控制技术应用。我们采用样品预处理、标准曲线建立和内部质量控制等技术,提高了土壤检测的准确性和可靠性。结果显示,质量控制技术显著提高了土壤检测质量水平,对环境监测、农业生产和土壤污染治理具有重要意义。