双曲线拟合法预测真空预压土体的沉降量及固结度

土体固结度是评价真空预压法加固土体效果的一个重要技术指标,而确定土体固结度的关键是土体最大沉降量的计算。本文结合工程实例,依据真空预压法施工前期土体沉降量的实测数据,利用双曲线拟合法进行拟合并预测土体最大沉降量及卸荷时的土体固结度,然后与常用的三点法预测结果进行对比,结果表明双曲线拟合法预测结果更加符合工程实际,且能保证工程的安全。     

GM(1,1)灰色模型在真空预压沉降预测中的应用

土体固结度是真空预压法加固土体效果的一个重要评价指标,地基最大沉降量的计算是确定土体固结度的关键。本文结合工程实例,分析了GM(1,1)灰色模型在真空预压沉降预测中的可行性,根据部分实测数据计算了地基最大沉降量及土体固结度,并与常用的三点法和双曲线法计算结果进行对比,结果表明GM(1,1)灰色模型的预测结果更符合工程实际。该研究对真空预压施工具有一定的指导意义。     

羟基磷灰石对Cd污染土壤中马铃薯生长及品质的影响

通过温室盆栽实验研究了施用羟基磷灰石改良Cd污染土壤对马铃薯生长及品质的影响.实验设置了3个Cd污染水平(0、5、10 mg.kg-1)、6个羟基磷灰石施用量(0、4、8、10、16、30 g.kg-1)和2个马铃薯品种(中薯3号、大西洋).结果表明,土壤Cd污染导致马铃薯单株产量下降(5 mg.kg-1的Cd污染土壤中降低24%～31%,10 mg.kg-1的Cd污染土壤中降低41%～45%),但是施用羟基磷灰石可以提高单株产量.相对于不施用羟基磷灰石,5 mg.kg-1的Cd污染土壤中施用10 g.kg-1的羟基磷灰石可以增产17%～39%,10 mg.kg-1的Cd污染土壤中施用30 g.kg-1的羟基磷灰石可以增产45%～58%.由于羟基磷灰石改善了Cd污染土壤环境,因此马铃薯器官中叶绿素含量和SOD活性明显上升,而MDA含量明显下降.施用羟基磷灰石也提高了马铃薯品质,马铃薯块茎中维生素C含量、淀粉含量以及蛋白质含量也明显提高.随着羟基磷灰石施用量由0 g.kg-1增加到30 g.kg-1,在5 mg.kg-1的Cd污染土壤中,马铃薯块茎Cd含量由0.87～0.95 mg.kg-1下降到0.13～0.21 mg.kg-1,降幅为78%～85%;在10 mg.kg-1的Cd污染土壤中,块茎Cd含量由1.86～1.93 mg.kg-1下降到0.52～0.65 mg.kg-1,降幅为66%～72%.实验表明,羟基磷灰石缓解土壤Cd毒性的主要机制是提高土壤pH值,降低土壤中有效态Cd含量,羟基磷灰石中的Ca阻碍土壤Cd向马铃薯迁移.但是羟基磷灰石对土壤Cd毒性的缓解效应是有限性的,过量施用可能对马铃薯生长和品质产生胁迫作用.在Cd污染土壤中施用适量的羟基磷灰石后中薯3号生长状况和品质好于大西洋,说明不同马铃薯品种对种植环境的改善有不同的响应.     

平朔安太堡矿区复垦地土壤微生物与土壤性质关系的研究

调查安太堡大型露天矿区西排土场植被恢复与土壤微生物的关系.结果表明,土壤中微生物量与土壤中的水分、速效磷、土壤有机质、有效性氮和海拔高度有明显的关系.麦地、林地、草地的土壤中呈现出:细菌》放线菌》固氮菌》霉菌;撂荒地呈现为:细菌》放线菌》霉菌》固氮菌;裸地呈现出:细菌》放线菌》霉菌.细菌、放线菌和霉菌呈现麦地最高,裸地最低,固氮菌为林地高于其他样地.在撂荒地和裸地中,细菌占微生物总量的一半以上.麦地、林地、草地、撂荒地中的各种菌、速效磷、土壤有机质、有效性氮含量明显高于裸地中的含量.微生物总量和样地的海拔、样地土壤的含水率有明显的关系,土壤中的含水量直接影响微生物总量.微生物总量与速效磷含量和有机质含量成正比,有机质含量与有效性氮含量成正比.细菌与海拔呈极显著负相关,与其他几种养分指标呈极显著正相关,放线菌与海拔和速效磷呈极显著相关,与其他指标相关性不显著,固氮菌与几种养分指标相关性均不显著.按全国土壤养分划分标准,安太堡大型露天矿区复垦地等级不高,还需要用科学的方法加快复垦区土壤的恢复.     

西藏拉萨市土壤气中氡、汞环境地球化学特征

研究了拉萨市及其附近土壤气中的氡、汞地球化学特征,利用地质累计指数法评价了其环境质量.1?579个测点的测量结果表明,土壤气中氡、汞的背景值分别是7?634.9 Bq/m³、41.5 ng/m³,标准偏差分别为2.7 Bq/m³、2.2 ng/m³.土壤气氡环境质量在研究区东部和西部比较好,在中部从南向北有逐渐加重的趋势,最高达到中度污染;氡的主要污染源是山间盆地沉积物中局部富集的放射性铀元素.从拉萨郊区向市中心,土壤气汞污染程度逐渐增加,最高达到严重污染;污染源主要是废气中的汞、宗教活动中使用的汞以及含汞的垃圾和废水.     

贵阳市表层土壤中镉的环境地球化学基线研究

以土壤环境地球化学研究为主线,以贵州省贵阳市8　046　km²为研究区域,将土壤重金属污染元素镉的空间分布规律与环境地球化学机理研究相结合,建立区域土壤环境地球化学基线,选用合适的判别指标判识自然作用过程与人类活动过程对土壤环境的影响.通过对487个样品的镉含量的统计分析,结果表明,贵阳市表层土壤中镉的基线值为0.068　mg/kg,镉元素含量大于1.010　mg/kg的样品可能遭受人为污染的影响.地质累积指数分析结果显示,贵阳市40%的表层土壤未受镉污染,19%的表层土壤在无污染与中度污染之间,14%受中度污染,19%的表层土壤介于中度污染到强污染之间,7%受强污染,1%的表层土壤介于强污染到极强污染之间.污染程度指数分析则显示,贵阳市57.9%的表层土壤未受到镉污染,镉的污染程度最大为12.1,96%的表层土壤污染程度小于4,总污染程度大于0,即总体受到污染.     

Assessing field vulnerability to phosphorus loss in Beijing agricultural area using Revised Field Phosphorus Ranking Scheme

Guanting Reservoir,one of the drinking water supply sources of Beijing,suffers from water eutrophication.It is mainly supplied by Guishui River.Thus,to investigate the reasons of phosphorus(P)loss and improve the P management strategies in Guishui River watershed are important for the safety of drinking water in this region.In this study,a Revised Field P Ranking Scheme(PRS)was developed to reflect the field vulnerability of P loss at the field scale based on the Field PRS.In this new scheme,six factors are included, and each one was assigned a relative weight and a determination method.The affecting factors were classified into transport factors and source factors,and,the standards of environmental quality on surface water and soil erosion classification and degradation of the China were used in this scheme.By the new scheme,thirty-four fields in the Guishui River were categorized as"low","medium"or"high"potential for P loss into the runoff.The results showed that the P loss risks of orchard and vegetable fields were higher than that of corn and soybean fields.The source factors were the main factors to affect P loss from the study area.In the study area,controlling P input and improving P usage efficiency are critical to decrease P loss.Based on the results,it was suggested that more attention should be paid on the fields of vegetable and orchard since they have extremely high usage rate of P and high soil test of E Compared with P surplus by field measurements,the Revised Field PRS was more suitable for reflecting the characteristics of fields,and had higher potential capacity to identify critical source areas of P loss than PRS.     

中草药种植区土壤及草药中重金属含量状况及评价

通过野外调查和室内分析相结合的方法,研究了河北省安国市中草药种植区土壤重金属As、Hg、Pb、Cd的含量、空间分布特征及草药中重金属含量状况,以及不同中草药对土壤重金属的累积特征,并对种植区土壤和草药重金属污染程度进行了评价.结果表明,种植区土壤重金属As、Hg、Pb、Cd含量均值分别为12.9、 0.036、 15.6、 0.118 mg·kg-1,均低于相应<土壤环境质量标准>二级标准值;以土壤背景值为标准评价,单项污染指数评价结果显示,16个中药种植区中土壤 As、Hg、Pb、Cd达轻度污染的比例分别为18.75%、43.75%、0%、100%,且6.25%的种植区土壤Hg污染达到中度水平.综合污染指数评价结果表明,12.5%种植区土壤重金属污染等级为警戒级,其余各地区均处于轻度污染水平;而以<土壤环境质量标准>二级标准值评价,各种植区单项污染指数及综合污染指数结果均<0.7,土壤环境清洁;绝大多数(>95%)种植区草药样品污染指数<1,不同中草药对土壤重金属的累积能力存在明显差异:紫菀、知母对Cd的富集系数及白芷、北沙参对Hg富集系数均>1.因此,在中药GAP(优良农业生产)基地土壤质量评价过程中,应重视中草药自身特性对重金属吸收和累积的影响.     

土壤铅-苯并[a]芘复合污染对小麦种子生长的影响研究

研究了土壤中低含量铅(Pb)-苯并[a]芘(B[a]P)复合污染对小麦种子萌发率、根伸长、芽伸长以及芽根比的影响,以期考察复合污染的生态效应并筛选具有指示土壤污染程度的指标.结果表明,小麦种子萌发率对Pb-B[a]P单一及复合污染均不敏感;Pb和B[a]P单一污染时小麦根伸长均受到一定程度的抑制作用;复合污染条件下Pb...     

Review of the remediation strategies for soil water repellency

Many regions of the world are predicted to experience water scarcity due to more frequent and more severe droughts and increased water demands. Water use efficiency by plants can be negatively affected by soil water repellency (SWR). It is timely to review existing techniques to remedy SWR. Ideally remediation addresses the origins of a problem. However, the fundamental mechanisms of how and why SWR develops are still poorly understood. In this review it was hypothesized that SWR occurs where the balance of input-decomposition of organic matter is impaired, due to either increased input or decreased decomposition rates of hydrophobic substances. Direct and indirect strategies to remedy SWR were distinguished. While direct remediation aims at abolishing the causes of SWR, indirect strategies seek to manage sites with SWR by treating its symptoms. The 12 reviewed strategies include applying surfactants, clay, slow-release fertilizers, lime, and fungicides, bioremediation of SWR through stimulating earthworms, choosing adapted vegetation, irrigation, cultivation, soil aeration and compaction. Some of the techniques have been applied successfully only in laboratory experiments. Our review highlights that it is not straightforward to cure SWR based on easily measurable and site-specific soil and vegetation properties, and that long-term, large-scale field experiments are required to improve the understanding of the evolution of SWR as cornerstone to develop cost-effective and efficient remediation strategies. We also identified current research gaps around the diagnosis and prevention of SWR.