城市土壤性质及其研究进展

结合近几十年来国内外有关城市土壤性质的研究成果,从物理特征、化学特征和生物特征三个方面进行论述,阐述了城市土壤在特殊成土过程和成土环境下表现出的独特性质,并针对当前城市土壤研究中存在的问题提出了研究展望.     

Data-driven estimates of global nitrous oxide emissions from croplands

Croplands are the single largest anthropogenic source of nitrous oxide (N₂O) globally, yet their estimates remain difficult to verify when using Tier 1 and 3 methods of the Intergovernmental Panel on Climate Change (IPCC). Here, we re-evaluate global cropland-N₂O emissions in 1961–2014, using N-rate-dependent emission factors (EFs) upscaled from 1206 field observations in 180 global distributed sites and high-resolution N inputs disaggregated from sub-national surveys covering 15593 administrative units. Our results confirm IPCC Tier 1 default EFs for upland crops in 1990–2014, but give a ∼15% lower EF in 1961–1989 and a ∼67% larger EF for paddy rice over the full period. Associated emissions (0.82 ± 0.34 Tg N yr^–1) are probably one-quarter lower than IPCC Tier 1 global inventories but close to Tier 3 estimates. The use of survey-based gridded N-input data contributes 58% of this emission reduction, the rest being explained by the use of observation-based non-linear EFs. We conclude that upscaling N₂O emissions from site-level observations to global croplands provides a new benchmark for constraining IPCC Tier 1 and 3 methods. The detailed spatial distribution of emission data is expected to inform advancement towards more realistic and effective mitigation pathways.     

我国农田土壤重金属污染来源及特点

近年来,我国重金属污染日趋严重引起了人们广泛关注。本文概括了我国农田土壤重金属污染来源及特点,为我国农田重金属污染防治提供依据。     

Coupled Numerical Analysis of the Stability Behaviour of Unsaturated Soil Slopes Under Rainfall Conditions

Thebasicstressvariablesintheconstitutivemodelde velopedbyAlonsoetal[5] aresoilnetstressandsoilmatricsuctions ,whicharedefinedby　　　σ″ =σ -ua (1)　　　s=ua-uw (2 )whereσisthetotalstress,uwistheporewaterpressureanduaistheporeairpressure .　　Thenetmeanstresspanddeviatoricstressqarede finedas　　　p =σ1+2σ33-ua (3)　　　q =σ1-σ3(4 )　　Asgenerallyregarded ,thesoilsuctioniscomposedoftwoparts ,matricsuctionandosmosissuction .TheosmosissuctionisneglectedoriginallyinAlonsoetal′smodelandhe…     

Spatial distribution of Cd and Cu in soils in Shenyang Zhangshi Irrigation Area （SZIA）, China

Heavy metal contamination of soils, derived from sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides, and so on, has been of wide concern in the last several decades. The Shenyang Zhangshi Irrigation Area (SZIA) in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years. This study investigated the spatial distribution and temporal variation of soil cadmium (Cd) and copper (Cu) contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd and Cu in soils was analyzed and then the spatial distribution and temporal variation of Cd and Cu in soils were modeled using Kriging methods. The results show that long-term sewage irrigation had caused serious Cd and Cu contamination in soils. The mean and the maximum of soil Cd are markedly higher than the levels in second grade standard soil (LSGSS) in China, and the maximum of soil Cu is close to the LSGSS in China in 2004 and is more than the LSGSS in China in 1990. The contamination magnitude of soil Cd and the soil extent of Cd con- tamination had evidently increased since sewage irrigation ceased in 1992. The contamination magnitude of soil Cu and the soil extent of Cu contamination had evidently increased in topsoil, but obviously decresed in subsoil. The soil contamination of Cd and Cu was mainly related to Cd and Cu reactivation of contaminated sediments in Shenyang Xi River and the import of Cd and Cu during irrigation. The eluviation of Cd and Cu in contaminated topsoil with rainfall and irrigation water was another factor of temporal-spatial variability of Cd and Cu contamination in soils.     

用石灰处理膨胀土路基填料

膨胀土在低压时遇水会发生体积膨胀,失水时会发生体积收缩,对膨胀土路基进行处理是保证路基稳定工作的常用工程措施之一。本文介绍了膨胀土工程性质对公路工程的危害以及膨胀土的石灰处治方法,对不同石灰掺加剂量的实验结果进行了分析,并提出了石灰处理膨胀土的施工工艺及注意事项。     

太湖地区几种水稻土的有机碳储存及其分布特性

选择了采自江苏省吴县市的黄泥土、乌泥土、白土等太湖地区代表性水稻土 ,测定了土壤有机碳的剖面分布、易氧化性碳分异、在土壤团聚体中的分布及 13 C稳定性同位素的剖面分异 .结果表明太湖地区水稻土中有机碳储量达 7～ 10 kg/m2 ,有机碳主要分布于 2～ 0 .2 5mm和 0 .2 5～0 .0 2 mm两级团聚体中 ,各土壤间有机碳的氧化活泼性接近 ,稳定性同位素组成类似 ,说明其有机碳地球化学性质趋向于与当前 C- 3农作物利用状况相平衡 .     

几种水稻土对磷的吸附及解吸特性研究

水稻土对磷的吸附曲线与简单Ｌａｎｇｍｕｉｒ等温吸附方程基本吻合,土壤对磷的吸附及解吸能力主要受土壤物理性粘粒含量及土壤活性铁、活性铝含量的影响,而与土壤本身有效磷含量无关。同一种水稻土随吸附磷量的增加,其解吸率有增加的趋势     

化学淋洗法修复重金属污染土壤效果研究

在国内外相关研究的基础上,文章研究化学淋洗修复技术在重金属污染土壤修复方面的运用．用浓酸消解土样并用火焰原子吸收法测定土壤中重金属含量,选用土壤柱作淋洗实验,分析去离子水和EDTA溶液两种淋洗剂对Cu、Zn、Pb、Cd四种重金属的淋洗效率,并对化学淋洗修复效果进行比较．     

双层地基一维非线性固结性状分析

由于层状土一维非线性固结问题的复杂性,其解析解一般不易求得。本文采用半解析法对多层地基一维非线性固结问题进行了求解,通过编程计算得到了相关沉降量与固结度随时间变化曲线．并详细分析了土性参数等对双层地基一维非线性固结性状的影响。