Chemical time bombs related to forestry practice: Distribution and behaviour of pollutants in forest soils

Heavy metals and persistent organic pollutants from atmospheric deposition and from fertilizer and pesticide applications are important hazardous substances in forest soils. Data are presented showing that these substances preferentially accumulate in the upper humic horizons of the soils. Another group of substances to be considered in relation to the chemical time bomb concept are the components of humus and soil minerals, mainly nitrogen and metals, which May, be mobilized and thus threaten groundwater quality. Forestry management practices such as thinning, cropping, fertilization and liming are discussed as potential triggers for the mobilization of harmful substances. in this context, The turnover (build-up and mineralization) of organic matter plays a crucial part. It will be shown, however, that even more danger arises from soil acidification induced by the atmospheric deposition of acidifying pollutants such as sulphates and nitrates.     

滑转条件下星球车坡面通过性评估试验

星球车是执行深空探测任务的主要移动平台,针对星球表面崎岖地形地貌,开展滑转条件下星球车坡面沉陷研究,确保其安全通过性能具有重要意义。基于传统地面力学研究方法,以速度和坡度为试验因素,车轮滑转率和沉陷为试验指标,开展滑转条件下的缩比星球车坡面沉陷试验;分析了试验因素对各车轮滑转率影响,以及不同滑转率和速度条件下沉陷变化规律,建立了滑转率关于坡度的一元二次模型。结果表明,模型车前轮和中间轮的滑转率随速度和坡度变化趋势总体趋于一致,与后轮滑转率变化趋势明显不同。坡度为25°时,前轮和中间轮滑转率最大值达到92.3%,后轮相应的最大滑转率为61.8%。试验条件下,各车轮沉陷最大值分别为33.1 mm（前轮）、33.9 mm（中间轮）和13.6 mm（后轮）;当滑转率的范围为25%～60%时,前轮和中间轮沉陷增加的较为平缓,平均增加率为22.5%,对于后轮滑转率超过35%后,沉陷变化较小,波动范围为?1.3～1.8 mm;速度对各车轮沉陷的影响明显较滑转率的小,沉陷的相对变化率范围为?12.5%～10.7%。该研究可为低重力环境下星球车研制、坡面通过性评估提供参考。     

高通过性四轮自走式烟草田间作业机的设计

针对烟草中后期田间管理迫切需要高通过性动力机械的现状,通过采用拱桥式车架,偏置布置在拱桥式车架一侧的发动机及传动系统,架高转向横拉杆及过桥传动轴等结构措施,设计出高通过性的四轮自走式烟草田间作业机,其最大通过高度1700?mm,变速范围1.0～18?km/h,解决了烟草田间作业动力机械高通过性的技术难题。该机自身可实现植保作业,若悬挂不同的机具可实现耕地、起垄、移栽、铺膜、中耕培土、打顶、采摘烟叶、拔烟秆等多种作业。小批量生产试验表明,该机驾驶劳动强度小,通过性好,对烟叶损伤小,作业效率高。     

轻载荷条件下轻型车辆车轮牵引通过性模型的建立与验证

为研究轻型地面车辆松软地面通过性能,针对轻载荷条件建立车轮牵引通过性预测模型,该文采用轮上载荷为30~90 N的轻载荷条件,以轮上载荷和轮径度为试验因素,车轮沉陷、挂钩牵引力和牵引效率为试验指标,开展滑转条件下轮壤相互作用试验研究。分析了试验因素对车轮牵引通过性的影响规律,发现载荷因素对试验指标的影响最为显著,显著性检验的置信度达90%。沉陷随着轮径的减小以及轮上载荷和滑转率的增加,车轮沉陷均呈现增加趋势,平均相对增加率分别为14.3%、36.9%和77.4%。挂钩牵引力随着载荷、滑转率和轮径的增加平均提高了约263%、295%和29.71%,牵引效率最大值均值为0.23,对应的滑转率为26.86%。基于传统沉陷模型和轮壤接触应力分布线性化公式,结合车轮土槽试验结果,建立了适合滑转条件的沉陷模型,模型计算值与试验值残差低于3.6 mm,平均相对误差小于6.4%,结果表明该模型能准确预测轻载荷条件下车轮沉陷。该研究为轻型车辆研制、轻载荷条件下车轮牵引通过性评估提供了参考。     

The zinc status of some Nova Scotia soils and crops

Abstract

Ranges for total, 0.1N HCl and EDTA‐(NH₄)₂CO₃ extractable Zn in 69 samples of surface soil (0–15 cm), representing nine soil series, were 14–108, 0.9–10.5 and 0.5–8.0 ppm respectively. Total Zn in barley (Hordeum vulgare), carrot (Daucus carata sativa), corn (Zea mays L), grape (Vitis spp.), onion (Allium cepa), pea (Pisum sativum, strawberry (Fragaria spp.), and wheat (Triticum spp.) leaves and in barley and wheat grain ranged from 13.5 to 80.6 ppm.

The results suggest that, with the possible exception of corn leaf samples from one location, Zn levels in plant tissue were adequate. However, the results also indicate that liming strongly acid sandy soils reduces Zn availability and may induce a deficiency in Zn sensitive crops.     

Assessing cadmium availability of contaminated saline-sodic soils as influenced by biochar using the adsorption isotherm models

ABSTRACT

In arid/semi-arid regions, soil salinization, sodification and contamination by heavy metals (HMs) are the main constrains to plant growth, crop production and human health. Biochar can affect soil behaviors, e.g. adsorption of HMs that is one of the most effective techniques for reducing their bioavailability. Effect of three levels (0%, 2% and 4% wt) of sugarcane bagasse-derived biochar and two cadmium (Cd) levels (0 and 50 mg Cd kg^?1 soil as Cd(NO₃)₂) on Cd adsorption of saline, sodic, saline-sodic and normal soils were evaluated through studying adsorption isotherms. Six isotherm models were fitted to the data and the best model were chosen. The maximum Cd adsorption (694 mg kg^?1) obtained in sodic soils without biochar treatment. Cadmium removal decreased when dosage of the applied biochar increased. The minimum Cd removal obtained as 17%, 21%, and 23% in control, 2% and 4% biochar-treated saline soils, respectively. Biochar increased Cd adsorption in salt-affected soils. Increasing pH in soil solution after biochar addition resulted in an increase in net negative surface charge and the affinity of soil particles for Cd adsorption. Consequently, 2% biochar could ameliorate Cd contamination. However, Cd adsorption decreased when dosage of the applied biochar increased from 2% to 4%.     

On the determination of total heavy metal content in saline soils and soils rich in organic matter

Abstract

Methods of soil decomposition for determination of heavy metal total content were considered. Two saline soils (chloride and sulphate solonchak solonetz) and one rich in organic matter were uzed for investigation. It has been established that decomposition by using HF‐HCl with a preliminary ignition at 500°C is a very suitable method. The type of the studied soils and the results obtained allow for this method to be recommended for decomposition of various soils.

On the basis of experiments with modelled soils it has been proved that possibilities for heavy metal losses on ignition are created when NaCl content and the percentage of weakly bound heavy metals (water‐soluble, exchangeable, etc.) are high. Under the conditions of the experiment (acid soils ‐ pH 4.3 and 5.0) losses of Zn and Pb but not of Cu have been incurred. Although these cases are not typical, this requires the applicability of the method for such particular occasions to be checked.     

Using iron metal rods to infer oxygen status in seasonally saturated soils

The oxygen status in soils is fundamental to a number of earth-science processes including biological, physical and chemical interactions. Since oxygen is time consuming and often difficult to measure in soils, this research explores the use of zero-valent iron rods as a means of estimating oxygen content in soils. Zero-valent iron rods (polished nails) were placed in three soil toposequences and the surface coatings formed by oxidation were compared to measured oxygen concentrations taken every three weeks for one year. When water was present in the soils, the oxygen was measured as dissolved oxygen and in drained conditions it was reported as percent. Coatings on iron metal rods inserted in the soil appear to correlate well with specific oxygen ranges. Rods in soils with O₂ concentrations below about 2 mg l^− 1 do not develop bright (7.5YR 4/4 to 5/8) oxide/oxyhydroxide coatings, but instead formed black (10YR 2/1–2) coatings. Rods in soils with O₂ concentrations between about 2% to 5% develop variegated bright (7.5YR 4/4 to 5/8) oxide/oxyhydroxide coatings indicating soil drainage and microsite differences in O₂ concentrations. Rods in soils with O₂ concentrations above about 5% with adequate moisture are almost completely coated with bright (7.5YR 4/4 to 5/8) iron oxide/oxyhydroxides. Mineralogy of oxide/oxyhydroxide coatings could not be established by XRD presumably due to the short-range order crystal structure of the metal oxide/oxyhydroxides. This method provides a simple and inexpensive means to qualitatively estimate the ranges of O₂ status in soils. This research may have implications in hydric soil determination, horticultural and agricultural applications, as well as, remediation techniques.     

Redistribution of organic pollutants in river sediments and alluvial soils related to major floods

Background, Aims, and Scope  More frequent occurrence of stronger floods in Europe as well as in other parts of the world in recent years raises major concern about the material damages, but also an important issue of contamination of the affected areas through flooding. The effects of major floods on levels and distribution of contamination with hydrophobic organic pollutants were examined from the continuous set of data for floodplain soils and sediments from a model industrial area in the Czech Republic where a 100-year flood occurred in 1997. The goal of this study was to evaluate the risk related to contamination associated with such extensive natural events and characterize the spatial and temporal distribution and dynamics of pollutants related to a major flooding shortly after the floods and also in the time period several years after floods. Methods  Sediments and alluvial soils from fourteen sites each were repeatedly sampled during the period from 1996 until 2005. The sampling sites represented five regions. Collected top-layer sediment and soil samples were characterized and analyzed for hydrophobic organic pollutants PCBs, OCPs and HCB using GC-ECD and PAHs using a GC-MS instrument. Spatial and temporal differences as well as the relative distribution of the pollutants were examined in detail by statistical analysis including multivariate methods with special emphases placed on the changes related to floods. Results  The organic pollutants levels in both alluvial soils and sediments exceeded the safe environmental limits at numerous sites. Pollutants concentrations and relative distribution as well as organic carbon content in both sediment and floodplain soils were significantly affected by the flooding, which resulted in a decrease of all studied contaminants in sediments and significant rise of the PAH pollution in the flooded soils. There was a unique and highly conserved PAH pattern in soils regardless of the floods and greater changes in PAH pattern in sediments related to floods. The relative distribution of individual PAHs reflected a combustion generated PAH profile. PAH levels in the river sediments rose again at the sites with continuous sources several years after floods. Discussion  The results showed different dynamics of PAHs and PCBs during the floods when PAHs were redistributed from the sediments to alluvial soils while PCBs have been washed out of the study regions. The data reveal longer contamination memory and consistent contamination pattern in soils, whereas sediments showed more dynamic changes responding strongly to the actual situation. The stable PAH pattern within the regions also indicates that a relative amount of all compounds is comparable across the samples and, thus, that the sources at different sites have similar character. Conclusions  Sediments have the potential to function as a secondary source of contamination for the aquatic ecosystem, but also for the floodplain soils and other flooded areas. The floods served as a vector of PAHs contamination from sediments to soils. The reloading of river sediments in time, namely with PAHs, due to present sources increases their risk as a potential source in the next bigger flood event both to the downstream river basin and affected alluvial soils. Recommendations and Perspectives  The results stress the importance of including the floodplain soil contamination in the risk assessment focused on flood effects. Floodplain soils have stable long-term environmental memory related to contamination levels, pattern and distribution, whereby they can provide relevant information on the overall contamination of the area. The sediments will continue to serve as a potential source of contaminants and alluvial soils as the catchment media reflecting the major flood events, especially until effective measures are taken to limit contamination sources. ESS-Submission Editor: Dr. Henner Hollert (Hollert@uni-heidelberg.de) This article is openly accessible!     

Properties,degradation risks and rehabilitation possibilities of heavy soils in Bulgaria

The objective of this study was to determine soil properties, limiting site deficiencies for agricultural production and degradation risks of some major soil groups of Bulgaria. Vertisols, Planosols, Chernozems and Luvisols were characterised based on soil analyses. Temporal waterlogging in combination with water erosion, soil compaction and chemical degradation limit the fertility of Vertisols and Planosols. Chernozems and Luvisols are partly compacted. To ensure soil productivity for coining generations and to protect soil and water resources, the evident soil degradation must be halted. Long‐term field studies of soil rehabilitation variants were conducted. Soil parameters and crop yield were the main indicators used to estimate soil quality. Pipe drainage in combination with subsoiling and the application of gypsum and limestone, respectively, are effective measures for site rehabilitation of degraded Vertisols and Planosols. Degraded Luvisols and Chernozems characterised by distinct and persistent subsoil compaction can be regenerated by subsoil loosening and following site‐adapted soil management practices.     

昆明市植烟土壤肥力状况评价

为了全面分析昆明市植烟土壤肥力状况,以1 000个代表性植烟土壤的理化指标为基础数据,运用模糊综合评价法(Fuzzy)对植烟土壤的肥力状况进行综合评价。结果表明:(1)昆明市植烟土壤质地以壤土为主,容重、孔隙度和持水量整体处于适宜烤烟生长范围,>0.25 mm水稳性团粒含量较高,土壤抗侵蚀能力强。(2)植烟土壤pH变异系数较小,微酸性土壤比例占48.10%;有机质含量丰富,全氮含量适宜,碱解氮含量中等,有利于烤烟种植中氮素的调控;速效磷含量变异程度较高,速效钾含量丰富;交换性镁、有效钼含量变异程度较大,有效硼含量中等,水溶性氯含量不均衡。(3)昆明市植烟土壤肥力综合评价指数(IFI)的变化范围是0.258～0.957,平均值为0.703,整体IFI分值较高。植烟土壤肥力综合评价中养分强度因素的有效钼、有效硼、交换性镁和速效磷指标相对其余指标对植烟土壤肥力的作用分值较小,是影响昆明市植烟土壤肥力的限制因子。     

同位素动力学方法评价中国亚热带地区主要酸性土壤磷状况及生物有效性的适用性

A ^32P isotope kinetic approach was used to describe the chemical status and bioavailability of phosphorus in 32 acidic soils from subtropical China.By determining the residual radoactivity,rt,in soil solution at different time,t,after introduction of the isotope in an amount of R into the steady soil-water system,a well-defined isotope kinetic model was established,and upon this model the decrease rate ,n,of log(rt/R) with respect to logt,the mean sojourn time of phosphate ions in solution,the mean exchange rate and the mean flux of phosphate ions between soil solid and solution phases were calculated.Other parameters,such as the exchangeable P within the first minute of isotope exchange(E1),and P in various compartments that could be exchanged with solution phosphte ions at different perods of time,were also obtained.For these acidic soils,the r1/R had a significant correlation with the contents of clay and free Al2O3 where r1 is the radioactivity in solution 1 minute after introduction of the isotope into the system.Parameter n also had a significant correlation with clay content and a neagtive correlation with soil pH,E1 values and Cp,the P concentration in soil solution,also Significantly correlated with clay and sesquioxide contents of the soils.these indicated that these isotope kinetic parameters were largely influenced by P-fixing components of the soils.For the soils with strong P-fixing ability,the E1 values overestimated labile P pools and hence their correlations with A values and plant P uptake were not significant .The other iostope kinetic parameters also had no significant correlation with plant P uptak.On the other hand,the convetional chemical-extracted p correlated better with plant P uptake .It was concluded that the iostope kinetic method could assess the p chemical status yet it would inappropriate in predicting plant available P for soils with a high P-fixing ability as the problem of an overestimation of soil lable P in these soils was inevitable.     

Micro flora related to the nitrogen cycle in the tropical upland farm soils

Samples of upland-farm surface soils (0–10 em in depth) belonging to various great soil groups were collected in 28 upland sites in Thailand during the rainy season.

Among the microbes related to the transformation of nitrogen, namely ammonifiers, ammonia oxidizers, nitrite oxidizers and denitrifiers, the count of denitrifier showed the maximum value amounting to 10⁴ to 10⁵ per 1 g of dry soil, followed byammonifier. The population level of nitrogen-fixing blue green algae was unexpectedly high, being 10³ to 10¹

The microbial counts in Brown Forest Soils, Rendzinas and Grumusols with high content of organic matter, available phosphorus and exchangeable potassium tended to be high.

Non-calcic Brown Soils, Reddish Brown Lateritic Soils, Alluvial Soils, Red-Yellow Podzolic Soils and Gray Podzolic Soils which lack in some nutrients showed intermediate levels of microbial populations, while the counts of nitrogen-fixing blue green algae in Alluvial Soils and those of denitrifier in Red-Yellow Podzolic Soils were markedly high. In the case of Low Humic Gley Soils and Regosols with low content of organic matter, available phosphorus and available potassium, the population of microbes was generally small.

The relationship between the organic matter content and the microbial population of soils was positively significant at 0.1 % level only in the case of fungal population (r=0.551), while the relationship between the available phosphorus content and the microbial population was positively significant at 0.1% level only in the case of Azotobacter (r=0.682).

The relationships between the total nitrogen, the exchangeable potassium, the amount of NH₄+^-N, the amount NO₂ ^--N, or the amount of NH₄ ⁺-N+NO₂ ^--N and each microbial population were not significant in any microbial groups.

The count of denitrifiers in upland farm soils of Thailand was 9 times as high as that in non-volcanic upland-farm soils of Japan and was 23 times higher than that in volcanic soils though large variations were seen among the great soil groups of Thailand. Conversely, the population of non-spore-forming nitrite oxidizers in the upland farm soils of Thailand was 1/100 that in non-volcanic soils of Japan and 1/280 that in volcanic soils. In the case of Azotobacter, the count in upland farm soils of Thailand averaged 2,800 per 1 g of dry soil. while that in non-volcanic upland farm soils of Japan was 77 on the average.

The ratio of aerobic bacteria to actinomycetes in upland farm soils of Thailand was 2.31, while that of non-volcanic soils of Japan was 7.28.     

不同侵蚀程度下地带性土壤的结构及渗透性能分析

为探讨侵蚀退化过程中地带性土壤结构的变化规律,选取湖北省不同侵蚀程度(微度、轻度、强度、剧烈)的3种典型地带性土壤(黄褐土、黄棕壤、红壤),比较分析了土壤结构稳定性和土壤渗透特性差异。结果表明:随侵蚀程度增加,3种地带性土壤团聚体水稳性逐渐降低,容重增加,饱和导水率呈现不同程度的下降,机械稳定性变化存在差异;在侵蚀程度相同时,3种地带性土壤团聚体机械稳定性、水稳性和饱和土壤导水率的高低顺序均为红壤黄棕壤黄褐土。相关分析表明,土壤团聚体机械稳定性和水稳性与游离氧化铝呈极显著正相关关系(相关系数=0.77和0.81,P0.01),与游离氧化铁呈显著正相关关系(相关系数=0.73和0.76,P0.05),说明游离态铁铝氧化物是影响土壤结构稳定性并形成地带性差异的关键因素,饱和导水率与团聚体水稳性指标和非毛管孔隙度、容重呈显著相关关系(P0.05),其中与水稳性团聚体分形维数达到极显著水平(相关系数=0.76,P0.01),表明水稳性团聚体分形维数可以作为预测和表征饱和导水率的指标。     

根际促生菌及其在污染土壤植物修复中的应用

植物对重金属吸收、转运和积累以及植物生物学特征使其成为修复重金属污染土壤的重要手段之一。然而,由于植物对重金属的耐受性有限而限制其广泛实际应用,因而探讨植物修复技术强化措施就显得尤为重要。随着自然资源的开发和技术的发展,微生物调控使植物修复技术变得更为可行和更有价值。回顾近年来新兴的微生物调控技术,植物根际促生菌资源因其对环境无污染,可利用自身的抗性系统减缓重金属对植物的毒性,促进植物的生长和影响重金属的迁移等优势,在修复过程中发挥着重要作用。目前,国内外就植物根际促生菌的筛选、鉴定和应用价值等方面已经做了大量的相关研究。本文综述了根际促生菌-植物相互作用的机制及其促进植物修复重金属污染土壤的作用原理。     

铵、钾同时存在时, 土壤对铵的优先吸附

Ten soils collected from different parts of China were used in a series of experiments to study fixation of NH4^ and K^ by soils.When K^ was added concurrently with or prior to NH4^ ,the soils were found to fix more moles of NH4^ than those of K^ ,irrespective of the mole ratios of NH4^ to ^ that were added.     

Assessing risks to groundwater from contaminated soils

Abstract. The regulatory regime for contaminated soils and groundwater in the UK is risk based. Indeed, the definition of contaminated land in UK law requires the presence, or likelihood, of significant pollution or harm before affected land meets the statutory test of being contaminated land. In dealing with contamination, a risk management approach is used that also requires the consideration of wider land-use planning priorities, the costs and benefits of remedial action, and the goal of achieving sustainable development. A parallel risk-based framework is adopted for polluted groundwater. The risk assessment process adopted for contaminated groundwater in the UK follows a tiered structure. A simple conceptual model is developed from desk study and site reconnaissance. This model is then used as the basis for designing a site investigation programme, the sampling being undertaken to test assumptions within the model as well as to develop it further. The Environment Agency (England & Wales) has developed a package of tools to aid this tiered approach. This paper describes the integrated risk assessment and risk management processes for contaminated groundwater in the UK, with emphasis on the tools and methods developed. It explains the importance of a conceptual understanding (or model) to all tiers of risk assessment and subsequent risk management.     

A survey of Michigan soils as related to possible boron toxicities

Abstract

The saturation extraction method for measuring available B in soil provided variable results and a narrower range thus making this test more difficult to interpret than tests with the boiling water method.

No close relationship between available soil B and either soil texture or soil pH level was found. The available B in soil ranged from 0.16 to 0.95 ppm with the highest level reflecting the recent use of B. The B level in the profiles of three typical sugarbeet‐bean soils ranged from none detectable in the subsoil to 0.54 ppm in the surface soil.

A survey of cropped versus uncropped soils showed that, on the average, cropped soil contained two‐thirds as much B as uncropped soil, suggesting that more extensive B deficiencies may occur in the future. Soil test levels for B in a calcareous soil decreased rapidly after B application. In this experiment soil B levels in excess of 1.5 ppm represented a potentially toxic condition for beans while any level above 2.0 ppm represented a definite toxicity. The bean plant B threshold level was in excess of 100 ppm. In the range of potential toxicity, bean yields and B soil tests were more closely related than were bean yields and B plant tests.     

裂隙膨胀土细观结构演化试验

为研究裂隙膨胀土的细观结构特征,对重塑膨胀土进行了干湿循环、三轴浸水和各向等压加载试验。利用CT(computerized tomography)机对试验过程中进行无损实时动态扫描,从细观上分析膨胀土裂隙的产生以及裂隙在水和外力作用下的闭合全过程。将细观扫描数据与宏观物理参数相联系,研究裂隙对膨胀土变形特征的影响。结果表明:无约束情况下对膨胀土进行干湿循环,试样边缘以及孔洞聚集区易形成裂隙;干湿循环造成膨胀土体积收缩存在一个稳定渐近线,体缩会趋于1个稳定值。裂隙膨胀土在浸水初期产生膨胀力并出现湿胀变形;随着浸水量的增加,软化效应产生且膨胀力逐渐减小,在围压和偏应力压缩作用下继而出现体缩现象;浸水后期,在偏应力作用下试样产生剪胀破坏,再次出现轻微剪胀变形。在水和荷载作用下,不规则裂隙和孔洞逐渐演化为较规则的圆形孔洞,且圆形孔洞趋于闭合;仅在外力作用时,裂隙较难完全闭合;水和外力的共同作用使得膨胀土裂隙的闭合效果要优于单纯施加荷载时的闭合效果。裂隙膨胀土在各向等压加载过程中存在明显屈服现象,以屈服点为分界,扫描数据和孔隙比随荷载的增大分为快速体缩段和缓慢体缩段,前者与裂隙在荷载作用下闭合并演化成孔洞有关;后者与加载后期孔洞较难闭合且形成的新结构具备抵御外部荷载的能力有关。研究成果可为进一步认识裂隙对膨胀土力学特性的影响提供参考。     

The pH of bodenburg silt loam soil as related to forest cover and time under cultivation

Abstract

Soil pH's were evaluated at three time intervals following land clearing at two locations in the Matanuska Valley. Seasonal fluctuations of pH values over a seven‐year period as determined in water (pH_w,) and 0.01 M CaCl₂ (pH_s) were additionally evaluated at these locations. A statistical rise in soil pH occurred at both locations with clearing and subsequent cultivation. Soil reaction differences related to season and year were not consistent and were not related to a definite pattern. No relationship between monthly or seasonal precipitation and the soil reaction was found. The correlation coefficient between pH_w and pH_s was highly significant. Work of other investigators is discussed in the interpretation of the data collected.