Leaching rates of heavy metal ions in forest soil

The leachability of Mn, Zn, Cd, Ni, V, Cu, Cr, and Pb was studied in two purely organic spruce forest soils: one control soil and one similar soil heavily polluted by Cu and Zn from a brass foundry in southern Sweden. Artificial rainwater, acidified to pH 4.2, 3.2, and 2.8 was used in the experiment. The 10% residence times, estimated from the experimental data, varied from 3 yr (Mn) to 70 to 90 yr (Pb) in the control soil and from 2 yr (V) to > 200 yr (Ph) in the polluted soil with a precipitation water of pH 4.2. Residence times for most elements studied (except V and Cr) decreased with pH of precipitation water.     

Using the RUSLE to identify factors controlling erosion rates of mine soils

Observable differences in particle size, smoothness and compaction between cap site (slope 2·8 per cent) and batter site (slope 20·7 per cent) surfaces on the waste rock dump at Ranger Uranium Mine were quantified in terms of revised universal soil loss equation (RUSLE) parameter values. Cap site surface material had a K_m (erodibility corrected for sediment density) of 0·030 and batter site surface material had a K_m of 0·0056. Using these K_m values (derived from particle size distributions), slope length and steepness (LS) factors of 0·36 for the cap site and 3·66 for the batter site, and a cover (C) factor of 0·45 for the cap site and 0·16 for the batter site, the RUSLE predicts an erosion rate from the cap site that is 1·9 times greater than erosion from the much steeper batter site. The RUSLE indicates that the finer particle size and blocky soil structure of the cap site (D₅₀ = 0·91 mm) compared with the looser granular structure of the batter site (D₅₀ = 1·74 mm) strongly influence erosion. The predictions are similar to observed soil losses from erosion plots on these sites under rainfall simulation events, for which the measured erosion rate from the cap site was approximately twice that from the batter site. For the RUSLE to predict the observed erosion rates, the support practice (P) factor for the cap site would have to be approximately 30 per cent greater than the P factor for the batter site. The higher cap site P factor probably results from smoothing and compaction caused by vehicle movement across the surface. Compaction is considered to have greatly reduced infiltration capacity, thus increasing the erodibility of the cap site. Vehicles probably also crushed the surface material at the cap site, creating the observed finer particle size distribution and further increasing the erodibility. Compaction, through its effects on erodibility (K_m) and surface roughness (P), is concluded to be the major cause of higher erosion from the cap site, even though the slope steepness is 10 times less. Parameterisation of the RUSLE quantifies the differences between sites and explains the unexpected erosion rates observed. The results highlight the need for careful management of rehabilitated sites to avoid increases in erosion which may arise from compaction by machinery.     

Some factors affecting behaviour of boron in soil

It has been reported by many workers that various soil properties influence the retention of boron added to soils, but there is little infomration on the relative importance of these properties to boron retention and there is something controversial in the published results regarding the effects of different soil properties such as organic matter content, soil reaction, available calcium content and texture on boron retention (15). The present study was undertaken to obtain more detailed informations on the relationships between boron adsorption and different properties of soils, and on comparative contribution of soil constituents such as organic matter, sesquioxides and inorganic colloids to boron adsorption of soils. In Japan, boron deficiency symptoms of crops often appear in the fields of volcanic ash soils, and many experiments on boron application have been conducted to amend the boron deficiencies of the soils. It is considered that volcanic ash soils may have special characteristics concerning boron retention in comparison with nonvolcanic ash soils. In the present study, therefore, some volcanic ash soils were also taken as samples in addition to non-volcanic ash soils to confirm their speciality to boron retention.     

4种土壤调理剂改良红壤铝毒害的效果研究

在温室条件下,采用植物盆栽试验,研究4种土壤调理剂不同施用量对酸性红壤铝毒害的缓解效果。结果表明,4种土壤调理剂均显著降低土壤中交换性铝含量及毒害性铝含量,显著提高玉米株高、生物量;各处理土壤中交换性铝含量与玉米株高及生物量之间呈显著相关性。牡蛎壳、白云石、钾长石、麦饭石4种土壤调理剂0.2%的施用量土壤交换性铝分别比对照下降了63.8%、70.5%、53.0%、12.3%;0.4%的施用量土壤交换性铝分别比对照下降了90.5%、92.0%、80.5%、23.4%。土壤中交换性铝、毒害性铝的含量随着4种土壤调理剂的施用量增加而降低,土壤中毒害性铝含量由低到高依次为白云石、牡蛎壳、钾长石、麦饭石。     

吸附性土壤溶质运移参数识别的粒子群-差分算法

非饱和土壤水分和溶质运移参数(导水率、扩散率、水动力弥散系数)的识别是进行数值模拟的关键.基于垂直一维非饱和吸附性土壤水分-溶质运移方程,以溴化钾为入渗溶液,分别以土壤含水率和溶质溶度的实测值与计算值标准差最小为优化目标,建立水分-溶质运移参数识别的多目标优化模型.应用权重系数法,将这一多目标优化问题转化为单目标优化问题,采用动态权重、异步时变学习因子的粒子群算法对模型求解.通过土柱实验,测定了220、380和780 min三组时刻的土壤含水率以及钾离子浓度的空间分布值,以前两组数据识别参数,第三组数据进行验证.结果表明入渗780 min权重系数为0.5时含水率以及钾离子浓度的计算值和实测值相关系数分别为0.977和0.952,标准差分别为0.007 4、2.369,实测值和计算值吻合较好,这表明粒子群识别水分和溶质运移参数是可行的.数值模拟表明,权重越大含水率实测和计算值的相关系数越大而浓度实测值和计算值的相关系数越小.     

污灌区土壤重金属累积影响因素研究

本文研究了大气沉降、化学肥料施用、污水灌溉3个外源因素对污灌区土壤中重金属Hg、Cd、Pb累积的影响,结果表明:污灌区大气干湿沉降和施肥输入土壤中3种重金属元素的数量顺序为Pb>Cd>Hg。污灌水中重金属Hg、Cd、Pb含量的高低与相对应的灌区土壤中重金属的累积量的多少基本一致,对土壤Cd累积影响最大的是污水灌溉,对土壤Hg累积影响最大的是大气沉降,污灌与大气沉降对土壤Pb累积影响作用相近,施肥对3种重金属元素累积影响最小。     

土壤微量元素含量及其影响因素的研究

论述了临沂市土壤中硼、锌、锰、铜、铁等5种主要微量元素的状况与其它因素的关系。有效硼含量0．09～3．67mg／kg，平均0．35mg／kg；有效锰22～572mg／kg，平均244mg／kg；有效锌0．15～4．02mg／kg，平均O．53mg／kg；有效铜0．09～5．78mg／kg，平均1．03mg／kg；有效铁3．2～162mg／kg，平均21．5mg／kg；有效锰2．0～131．4mg／kg，平均23．4mg／kg。不同土壤类型的以上5种微量元素有明显差异，其特征是砂姜黑土缺锌，棕壤、水稻土富含铁、铜、锰、锌；成土母质是影响土壤微黾元素的重要因素之一，发育在基性岩上的土壤一般含量较高，而由红土母质发育的土壤则含量较低。土壤有机质含量与土壤微量元素有明显正相关关系，其中速效锌、速效硼和速效铜与有机质的关系尤为显著。     

土壤微量元素含量及其影响因素的研究

论述了临沂市土壤中硼、锌、锰、铜、铁等5种主要微量元素的状况与其它因素的关系。有效硼含量0.09~3.67 mg/kg,平均0.35 mg/kg;有效锰22~572 mg/kg,平均244 mg/kg;有效锌0.15~4.02 mg/kg,平均0.53 mg/kg;有效铜0.09~5.78 mg/kg,,平均1.03 mg/kg;有效铁3.2~162 mg/kg,平均21.5 mg/kg;有效锰2.0~131.4 mg/kg,平均23.4 mg/kg。不同土壤类型的以上5种微量元素有明显差异,其特征是砂姜黑土缺锌,棕壤、水稻土富含铁、铜、锰、锌;成土母质是影响土壤微量元素的重要因素之一,发育在基性岩上的土壤一般含量较高,而由红土母质发育的土壤则含量较低。土壤有机质含量与土壤微量元素有明显正相关关系,其中速效锌、速效硼和速效铜与有机质的关系尤为显著。     

Effect of metal toxicity on the size of the soil microbial biomass

The amount of soil microbial biomass was measured by the chloroform fumigation technique on agricultural soils which had been previously treated with different bulky organic manures. Amounts of soil microbial biomass in soils receiving sewage sludge or sludge-containing composts were much smaller than in soils which received farmyard manure over the same period. This effect was attributed to the toxic metals present in the sludges and was readily detectable more than 20 years after the last sludge application.     

影响土壤氮素径流流失的因素探析

从自然因素和人为因素出发探讨了地形、降雨、土壤理化性质、植被以及施肥、耕作制度等因素对土壤N素流失的影响,并综述了国内外有关研究的最新进展。并认为,基于这些因素相互作用的复杂性,有必要开展以下3方面的内容:一是大量开展多因子交叉实验,定量评价它们之间的关系,这为深入理解土壤N素流失机理和确定流域非点源污染模拟模型参数提供科学依据;二是加强有关土壤N素流失机理的多学科之间的联系,协同攻关建立较完善的理论认识;三是利用微观径流小区开展田间试验,结合遥感和GIS分析等方法,建立宏观大尺度土壤N素流失模型,为环境问题的宏观决策提供支持。     

The self-diffusion of sodium in soil: factors affecting the surface mobility

A study is presented of the self-diffusion of sodium in a sub-soil. Impedance factors (f_s)associated with the surface phase have been derived, representing the mobility of sorbed sodium ions relative to mobility in an ideal solution. Effects of drying, of cationic com-position and of enrichment with either native clay fraction or ‘pure’ clay minerals were investigated. The liquid phase impedance factor (f_L) without added clay was 0.29: clay enrichment affected soil structure and hence f_L. Values of f_s were in the range 0.19–0.05, and were about one-third of f_L. The value off, decreased as clay content increased, being halved when 50% native clay or 10% clay mineral was added. In a sodium saturated soil f_s was 0.06, less than half that in a calcium saturated soil.     

Use of ammonium bicarbonate DTPA soil test to evaluate elemental availability and toxicity

Abstract

The literature published on the use of the Soltanpour and Schwab Ammonium Bicarbonate‐DTPA (AB‐DTPA) soil test shows that it can be used to determine availability and toxicity indices for many elements. It has been shown to be an effective test for measuring the availability indices of P, K, Zn, Fe, Mn, Mo, Pb, Ni, Cd and Se. Theoretically, it can also be used to determine the availability indices for S, Cu and As. The AB‐DTPA test can predict toxicity of B as well as the standard hot water rest, although within the non‐toxic range of B, it is not as effective as the hot water test. The hot water test alone predicts B availability well, but the AB‐DTPA B test result requires inclusion of soil water pH, organic matter and clay contents in a regression equation for predicting B availability. This test is not suitable for determination of exchangeable plus soluble Ca and Mg (high levels), as these precipitate as carbonates during extraction. The AB‐DTPA test procedure with analysis by an inductively‐coupled plasma spectrometer for simultaneous determination of elements, makes soil and overburden testing very efficient.     

不同耕种时间下土壤剖面盐分动态变化规律及其影响因素研究

以新疆奇台县绿洲不同耕种时间土壤含盐量为研究对象,运用聚类分析与相关分析法对其含盐量变化规律、盐分剖面类型及其影响因素进行了研究。结果表明:在荒地转化成人类熟作的农田(5 a以上)过程中,土壤剖面盐分特征变化依次为表聚型、均匀型、震荡型和底聚型。未耕地土壤含盐量高,是典型的盐渍土,且表层聚集现象明显,含盐量在表层(0～20 cm)占整个剖面的34.31%。耕种5 a、10 a的土壤,多为底聚型盐分剖面。随耕种时间加长,土壤各层含盐量的活跃程度变化依次为活跃层、次活跃层和较稳定层;土壤含盐量与有机质含量的关系由极显著正相关转变为极显著负相关,而与土壤pH的关系变化则相反。有耕作活动的土壤盐渍化发生了逆向演替,耕种10 a土壤平均含盐量仅为未耕地的20.90%,脱盐速度随着时间的增加而减小,由早期(0～3 a)的1.56 g kg-1a-1,下降为后期(5～10 a)的0.04 g kg-1a-1。     

Using fault tree analysis to identify contributing factors to engulfment in flowing grain in on-farm grain bins

Findings reported by researchers at Illinois State University and Purdue University indicated that since 1980, an average of eight individuals per year have become engulfed and died in farm grain bins in the U.S. and Canada and that all these deaths are significant because they are believed to be preventable. During a recent effort to develop intervention strategies and recommendations for an ASAE farm grain bin safety standard, fault tree analysis (FTA) was utilized to identify contributing factors to engulfments in grain stored in on-farm grain bins. FTA diagrams provided a spatial perspective of the circumstances that occurred prior to engulfment incidents, a perspective never before presented in other hazard analyses. The FTA also demonstrated relationships and interrelationships of the contributing factors. FTA is a useful tool that should be applied more often in agricultural incident investigations to assist in the more complete understanding of the problem studied.     

节食通过N-酰基乙醇胺信号介导途径影响线虫寿命

饮食限制在酵母、线虫、果蝇和啮齿动物等众多物种中被证明可以延长寿命和推迟与年龄有关的疾病.在线虫中已经发现了一些与饮食控制影响寿命过程相关的关键分子,包括雷帕霉素营养敏感(target of rapamycin,TOR)途径和Foxa转录因子PHA-4.但是,当营养有限时,生物的新陈代谢信号如何协调器官对营养匮乏的应答和体内动态平衡之间的关系人们仍然知之甚少.     

The influence of soil characteristics on the toxicity of four chemicals to the earthworm Eisenia fetida andrei (Oligochaeta)

Summary The acute toxicity of Cd (chloride), chloroacetamide, 3,4-dichloroaniline and pentachlorophenol to the earthworm Eisenia fetida andrei was determined using the OECD (1984) artificial soil and contact testing procedures. To investigate the influence of two soil characteristics (pH and organic-matter content), the toxicity of the chemicals was also determined in two natural sandy soils. It is concluded that the filter-paper contact test cannot be recommended to predict earthworm toxicity of these chemicals in soil. Toxicity in soil was influenced by both pH and organic-matter content. Differences between LC₅₀ values in the high-organic-matter artificial soil and in an acid, low-organic-matter sandy soil were, however, not greater than a factor of 3–4. The results of this study therefore support the use of a well-defined artificial soil substrate for standardized earthworm toxicity tests.     

Influence of climate factors on soil heavy metal content in Slovenia

Purpose

In spite of equal lithology, the local climate can affect soils’ geochemical characteristics. We investigated the dependence of heavy metal content on climatic factors according to a hierarchical nested analysis of variance design (ANOVA).

Materials and methods

We examined the heavy metal content in soils developed on the Upper Triassic dolomite at six locations situated at increasing distances from the Adriatic Sea towards inland. We tested the influence of the locations’ position, i.e. climate, vegetation cover, small-scale variability and analytical error. Co, Cr, Cu, Ni, Pb and Zn contents were determined by emission spectrometry.

Results and discussion

An initial increase in annual precipitation towards inland is followed by a steady decrease. Very high small-scale variability prevented statistically significant differences from being established at the location level due to the high variance components exhibited. However, the simpler one-way and non-parametric varieties of ANOVA confirmed significant differences in Co, Cr and Ni among locations. The differences are more pronounced in grassland soils where the Cu and Pb contents also differ between locations. There is a positive correlation among annual precipitation, Co, Cr and Ni, and it seems that the prevailing winds can also influence their content in soils.

Conclusions

The Co, Cr, Cu and Ni values are readily the highest in those locations with the greatest precipitation, possibly due to their resistance to leaching. The soils could be additionally enriched by an eolian contribution from the SW located outcropping flysch rocks. The established variability could be due to somewhat different dolomite composition. The reasons for the observed geochemical variability are complex and only partly due to climate.

     

Role of soil properties in sewage sludge toxicity to soil collembolans

Soil properties are one of the most important factors explaining the different toxicity results found in different soils. Although there is knowledge about the role of soil properties on the toxicity of individual chemicals, not much is known about its relevance for sewage sludge amendments. In particular little is known about the effect of soil properties on the toxicity modulation of these complex wastes. In addition, in most studies on sewage sludges the identity of the main substances linked to the toxicity and the influence of soil properties on their bioavailability remains unknown.In this study, the toxicity of a sewage sludge to the soil collembolan Folsomia candida was assessed in nine natural soils from agricultural, grassland and woodland sites, together with the OECD soil. Correlations between the relative toxicity of sludge for collembolans in the different soils and their physical and chemical soil properties were assessed in order to identify the main compounds responsible for the effects observed. Furthermore, the relationships between the toxic effects to collembolans and water-soluble ions released by sludge, pH and electric conductivity were also assessed, together with the modulating effects of soil properties.Sludge toxicity was directly linked to the water extractable ammonium, which explained most of the mortality of the collembolans, and part of the inhibition of reproduction. For the last endpoint, nitrite also contributed significantly to the inhibition observed. The varied levels in water extractable ammonium in the different soils at equal dosages seem to be, in turn, modulated by some soil properties. Higher organic carbon contents were associated with lower toxicity of sludge, both for survival and reproduction, probably related to its higher ammonium sorption capacity. In addition, for reproduction, increasing the C/N ratio and pH appeared to increase the toxicity, probably due to both the greater difficultly in nitrification and the known unsuitability of alkaline soils for this species.     

Some factors affecting survival of sclerotia of Macrophomina phaseolina in soil

At least 75% of the sclerotia of Macrophomina phaseolina survived for 1 yr in most natural soils kept at 26°C and at 50–55% of the soil moisture holding capacity (m.h.c.). Although survivability was reduced in a very acid soil (pH 4.5) collected under a pine stand, 33% of the sclerotia survived for 1 yr. Soil pH had very little or no effect on sclerotial survivability. Of three organic amendments tested (alfalfa hay, chitin, pine needles) only ground alfalfa hay at 0.8% (w/w) reduced survivability of sclerotia in soil by about 75% in a year. Alfalfa hay at 0.4% reduced survivability by 36%. Various N sources added at 200 μg Ng^?1 soil had no effect on survival. Of 13 fungicides tested, only benomyl and captan at 20 μg a.i. g^?1 soil appreciably reduced populations of sclerotia in soil.Soil temperature and moisture content were the two most important factors affecting survivability of sclerotia. At ?5 or 5°C the biggest drop in sclerotial survivability occurred when the soil was incubated moist (at 50% m.h.c. or more). At 26°C the biggest drop occurred in air-dried soil (2–3% m.h.c.) and survivability was decreased to some extent at 15 and 30% m.h.c. Survivability also dropped rapidly in moist soil (50–55% m.h.c.) exposed to four cycles each having 3-week freezing (?5°C) and 1 week thawing (26°C). Sclerotia in air-dried soil (2–3% m.h.c.) continuously kept at ?5°C maintained nearly complete survivability after 16 weeks. Sclerotia survived almost 80–90% in moist soil (50–55% m.h.c.) kept for 16 weeks at 26°C or in moist soil exposed to four cycles each having 3-week thawing (26°C) and 1-week freezing (?5°C).     

The toxicity of the fungicide propiconazole to soil flagellates

 We investigated the effects of the ergosterol-inhibiting fungicide, propiconazole {1-[[2-(2,4-dichlorphenyl) - 4 - propyl - 1,3 - dioxolan - 2 - yl]methyl] - 1H - 1,2,4 triazole; Tilt}, on mixed natural populations of bacterivorous and fungivorous flagellates in soil and on single species of bacterivorous flagellates in liquid culture. The fungicide affected a mixed natural population of fungivorous flagellates less than the population of bacterivorous flagellates. Our results indicated that the effects of propiconazole on flagellates are direct toxic effects and not effects mediated via their food. All tested types of flagellates were significantly harmed when exposed to the concentration of propiconazole normally applied to agricultural fields (625 mg l^–1). However, when exposed to the concentration of propiconazole which we expect in the soil water phase after application (ca. 0.6 mg l^–1) the effect on most of the tested flagellates was slight. Still, one tested flagellate species, Dimastigella trypaniformis, was extremely sensitive to the compound, and it is possible that field application of propiconazole has negative effects on certain sensitive species, and therefore alters the composition of the soil flagellate community in the direction of a higher r/K ratio. Received: 7 April 1999