Iodine and bromine contents of some Austrian soils and relations to soil characteristics

Inductively coupled plasma mass spectrometry (ICP-MS) analysis was used to determine iodine and bromine concentrations in several Austrian agricultural soils. The determined iodine concentrations in topsoils vary between 1.1 and 5.6 mg kg^—1, the arithmetic mean amounted to 3.1 mg kg^—1, bromine contents are always higher than the corresponding iodine values, varying between 2.4 and 11.9 mg kg^—1 with an arithmetic mean of 5.7 mg kg^—1. Due to their different geological origin lime-free soils on average contained significantly less iodine and bromine than calcareous soils. In general the observed values are supported by literature values from other countries far from the sea. A correlation analysis of results with several soil parameters resulted in positive correlations with clay content and a negative relation to sand content. In the group of calcareous soils I and Br correlated positively with organic carbon contents and exchangeable calcium.     

Interannual and seasonal changes in the soil exchange rates of monoterpenes and other VOCs in a Mediterranean shrubland

Information about soil VOC inventories and exchange rates in different soils is very scarce. Seasonality of soil VOC exchange rates is also largely unknown, despite the increasing interest in some soil volatile compounds, such as monoterpenes, because of their important role in soil ecology. We aimed to explore and quantify soil VOC exchange rates in a Mediterranean shrubland and their seasonality. Measurements of soil VOC exchange were taken using GC‐MS and PTR‐MS techniques, together with soil temperature, soil moisture and soil CO₂ efflux measurements, during two annual campaigns with contrasting precipitation. Methanol, acetic acid, ethyl acetate, acetaldehyde, acetone, C₃ and C₄ carbonyls (such as methyl ethyl ketone), α‐pinene and limonene, showed the highest emission rates. Maximum soil monoterpene emission rates were very low (0.003 nmol m^?2 s^?1) compared with foliar monoterpene emission rates. The emission rates of the other VOCs were also low (maximum 0.8 nmol m^?2 s^?1) except for methanol (1.2 nmol m^?2 s^?1). Maximum soil uptake rates for some VOCs, such as methanol and acetonitrile (ranging from ?0.1 to ?0.5 nmol m^?2 s^?1) were, however, comparable with foliar uptake rates. Further studies are needed to corroborate these results and the possible importance of the soil VOC sink in regional chemistry‐climate models. Long‐term severe drought increased soil monoterpene emission rates in this Mediterranean shrubland. The increases seem to be linked to changes in the soil’s physical properties induced by low soil moisture. Unlike monoterpenes, other soil VOC emission rates decreased when soil moisture was low. The results suggest a seasonal control of soil temperature on the emission rates of monoterpenes and other VOCs. The emission rates increase with soil temperature. Positive correlations between the VOC exchange rates and the soil CO₂ fluxes suggest that phenology of roots and microorganisms also controls seasonal changes in soil VOCs in this Mediterranean shrubland.     

Shrinkage of clay soils: A statistical correlation with other soil properties

The hypothesis that the shrinkage of soils is greater when expansible minerals are dominant was tested with 63 soils containing between 40 and 64% clay. Shrinkage between pF 2 and 4 (0.1 and 10 bar) correlated significantly with the expansible mineral content (measured by ethylene glycol retention) for remoulded but not for dried and rewetted specimens. Shrinkage between pF 4 and 6 (10 and 10³ bar) was strongly correlated with the expansible mineral content for both kinds of specimens. The physical significance of the results is discussed, and it is concluded that interlamellar shrinkage is not the principal component of bulk shrinkage.     

Zinc distribution in Zimbabwean soils and its relationship with other soil factors

Abstract

The distribution of zinc in some major Zimbabwean soils was studied using 120 profiles taken from 22 different locations. The total zinc status (TL‐Zn) of the horizons of soils studied was low (8 ppm), and the range was narrow (3.7 to 16.3 ppm). The residual zinc (RS‐Zn) fraction was about 65 percent of the total zinc found in the soils, while 15 percent was organically bound zinc (OG‐Zn), 14 percent was available zinc (MG‐Zn), and 6 percent was zinc associated with hydrous metal oxides (OX‐Zn). The total zinc status of the soils was related to parent material. Generally, texture had a significant effect on zinc distribution with heavier textured soils having more zinc in most fractions than the lighter textured soils. A decrease in zinc down the profile was observed for available, residual, and total zinc. If cropped intensively, 32 per cent of the soils with less than 1 ppm available zinc have the potential for zinc deficiency. Multiple stepwise regression analysis showed that organic matter, silt and clay contents, available copper, and resin P₂O₅ contents were important for predicting the available zinc content of the soils, while texture and organic matter content were important in predicting total zinc content.     

Sorption and desorption of cobalt by soils and soil components

The sorption of Co by individual soil components was studied at solution Co concentrations that were within the range found in natural soil solutions. Soil-derived oxide materials sorbed by far the greatest amounts of Co although substantial amounts were also sorbed by organic materials (humic and fulvic acids). Clay minerals and non-pedogenic iron and manganese oxides sorbed relatively little Co. It is considered that clay minerals are unlikely to have a significant influence on the sorption of Co by whole soils. Cobalt sorbed by soil oxide material was not readily desorbed back into solution and, in addition, rapidly became non-isotopically exchangeable with solution Co. In contrast, Co was relatively easily desorbed from humic acid and a large proportion of the Co sorbed by humic acid remained isotopically exchangeable. Cobalt sorbed by montmorillonite was more easily desorbed than that sorbed by soil oxide but less easily than that sorbed by humic acid. Cobalt sorption isotherms for whole soils at low site coverage were essentially linear and the gradients of isotherms increased with pH. A comparison of isotherm gradients for whole soils and individual soil components supported the suggestion that Co sorption in whole soils is largely controlled by soil oxide materials.     

Stability in solution and reactivity with soils and soil components of iron and zinc complexes

Naturally derived complexes with the ability to complex (unidentate) or chelate (polydentate) metals are a cheaper alternative to synthetic chelates to correct micronutrient deficiencies, but despite their widespread use there is a lack of knowledge on their agronomic performance. The aim of this paper was to evaluate the stability of iron (Fe) and zinc (Zn) lignosulfonate, gluconate, amino acid, and humate complexes in solution over time and at different pH values. Also, their stability in a concentrated nutrient solution and their reactivity with soils and soil components was evaluated. In our experimental conditions, all the complexes (except Fe amino acid) remained stable in solution for an extended period of time. All Zn complexes and the Fe lignosulfonate were stable in solution up to pH 7.0–7.5, while Fe gluconate only maintained 20%–40% of the iron in solution in the pH range 5–11 and Fe amino acid and humate complexes barely maintained small concentrations of Fe in solution above pH 3. Most of the complexes maintained Fe and Zn in concentrated nutrient solutions for irrigation systems, but Fe amino acid only maintained around 70% of the iron added. In general, the interactions of complexes with soils and soil components produced a high retention. The interaction of Fe lignosulfonate with peat, illite, and ferrihydrite, and Fe gluconate with peat and illite resulted in significant amounts of Fe to remain in solution, while for the Fe amino acid and humate the Fe remaining in solution was low. All Zn complexes were highly retained in an acidic peat, illite, and montmorillonite clays and soils, while no retention was observed on ferrihydrite. In conclusion, the stability of complexes in different conditions is related to the percentage of complexed element in the products. While complexes can be used to maintain micronutrients in solution in aqueous media (foliar and fertigation), their application to soil should be considered as a measure to increase metal availabilities but not their solubility.     

Effect of the main soil components on the sorption of copper,zinc, and lead by urban soils

The sorption of copper, zinc, and lead by two urban soils with different levels of contamination was studied. Changes in the sorption capacity and fixation strength of the metals were revealed after the destruction of the main components playing the important role in the fixation of metals by the soil.     

Seasonal changes in the microbial biomass of Brazilian soils with different organic matter contents

Abstract

Carbon and nitrogen levels of microbial biomass were studied in four plots located in Rio de Janeiro State, Brazil. Two samplings were carried out, the first one, on November 1992 when rainfall was high which led the soil to high levels of moisture, and the second one on March 1993 when there was a decrease in rainfall coupled with high temperatures. Microbial carbon (MBC) and microbial nitrogen (MBN) assessments were done by the fumigation‐extraction method. The results showed significant differences for MBC and MBN between the sampling times and between different plots. Moreover, MBN showed differences as a function of sampling depth. In the 1993 sampling, developed under moisture conditions of soil which promoted the mineralization of organic matter, lesser values of MBC and MBN were found, whereas there was no difference in the organic carbon content. This fact shows a major sensitivity of biomass measurements to reflect changes which occur in the soil organic matter content. Significant correlations were obtained between MBC and organic carbon (r = 0.35, P < 0.01, n = 68), MBN and total N (r = 0.62; P < 0.07, n = 47), and MBC with NBM (r 0.74, P < 0.01, n = 54).     

Soil micronutrient contents and relation to other soil properties in Ethiopia

Abstract

Alfisols, Vertisols, Inceptisols, Aridisols, Mollisols, and Entisols were sampled (0–30 cm) from 32 locations across Ethiopia. The soils were analyzed for copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) contents using 0.005 M diethylene triamine pentaacetic acid (DTPA), 0.05 M hydrochloric acid (HC1), and 0.02 M ethylene diamine tetraacetic acid (EDTA) extractants. EDTA extracted more of each micronutrient than DTPA, which extracted greater amounts than HC1. The quantities of EDTA and DTPA‐extractable micronutrients were significantly correlated, and were in the order: Mn>Fe>Cu>Zn. The order of HCl‐extractable micronutrients was Mn>Fe>Zn>Cu. Micronutrient contents of Mollisols, Vertisols, and Alfisols were usually greater than those of the other soils, and Entisols usually had the lowest micronutrient contents. The contents were mostly positively correlated with clay and Fe₂O₃ contents, but negatively correlated with soil pH and A1₂O₃contents. While comparison of DTPA‐ and EDTA‐extractable micronutrients with critical levels showed that most soils had adequate amounts of the micronutrients for crops, the amounts extracted by HC1 were below critical levels in most soils. Since the critical levels that were used in the comparisons were not established in Ethiopia, calibration of the soil contents of these micronutrients with crops grown in Ethiopia is required to identify the most suitable extractant(s).     

Studies on the rate of decomposition of plant residues in soil by following the changes in sugar components

Uniformly ¹⁴C labelled straw and ryegrass leaf were incubated in soil in the proportions 0.5 and 1% w/w, respectively at 12°C for various periods up to 5 years.
Samples were hydrolysed with 2.5 m H₂SO₄ under reflux for 20 min to release non-cellulosic sugars and subsequently with 12 M/0.5 m H₂SO₄ to release glucose from cellulose-like polymers. Total radioactivity was determined in whole soil and hydrolysates and in individual sugars.
Fitting the data to simple exponential equations, total and 2.5 m H₂SO₄ hydrolysate radioactivity were best expressed by three part exponential functions, whereas radioactivity in 12M/0.5M H₂SO₄ hydrolysates and sugars were best expressed by two part functions, except for arabinose from the straw, for which a three-part function was better.
A comparison of the fit was made with that using the single-term exponential expressions devised by Janssen, 1984 and Weibull, 1951 and with a modification of the two part exponential expression by the substitution of one term by the Weibull expression. Apart from the Weibull expression on its own, there was no significant difference between the expressions.
It is suggested that, even for well defined carbohydrate components of the substrate, the decomposability changes with time because of their increasing inaccessibility to microorganisms, rather than that several components are present each with a different constant rate of decomposition.     

Standard plant bioassays for toxicity assessment of urban soils with complex xenobiotic profile

We have assessed the toxicity of urban soil with a complex xenobiotics profile incorporating persistent organic pollutants using standard plant biotesting with Latuca sativa (L.) lattice and Triticum aestivum (L.) wheat. Analysis of adjoint variations of the certain endpoints that characterize the growth parameters allowed one to reveal and qualitatively define the tested activity as being similar to the functional effects of some phytoregulators. No correlation was revealed between the level of the tested activity expressed with the indicated endpoints and the concentrations/sum of concentrations of xenobiotics profile components.     

Phosphatase activities of pasture plants and soils: Relationship with plant productivity and soil P fertility indices

Summary Phosphatase activities of herbage roots and soil were measured at low- and high-fertility pasture sites over 12 months. Seasonal trends were examined and relationships with herbage yields, plant P contents, soil moisture and available P were assessed. The phosphatase activities generally followed complex seasonal patterns, although some trends were apparent. At the low-fertility site, where organic P provides most plant P, herbage and root phosphatase activities were correlated significantly (P<0.05) with available organic P, although generally, the plant phosphatases were not good indices of plant yield or P status. Soil moisture content appeared to be the major factor controlling plant phosphatase activity. Herbage phosphatase responded negatively at the low-fertility site, probably as a consequence of lower P availability from dry surface soil. Root phosphatase responded positively at both sites, indicating a different physiological role from that of the herbage enzyme. At the low-fertility site, soil phosphatase was correlated significantly (P<0.05) with herbage yield.     

Interactions in microbial use of soluble plant components in soil

Glucose, glutamic acid, alanine, valine, and albumin were used as model substances to represent readily available soluble plant components. Their mineralisation in soil was monitored by making hourly measurements of total CO₂ evolution and periodic measurements of ¹⁴CO₂ during a 5-day incubation period. When glucose and the amino acids were combined in dual substrates the two components were mineralised simultaneously. In each combination the component with the shortest lag phase or highest specific growth rate () was mineralised preferentially. Glucose accelerated the mineralisation of the amino acids that had longer lag phases than glucose (i.e., alamine and valine). During the first 8 h, glucose mineralisation was reduced in the dual substrates compared with its mineralisation as a single substrate. The smaller the difference between the lag phase of glucose and the amino acid, the greater was the reduction in the glucose mineralisation rate. During the exponential phase, the effects on glucose mineralisation were dependent on the nature and concentration of the amino acid. The interactions observed between glucose and amino acid decomposition indicated that these substances were mineralised, at least partly, by the same microorganisms. In contrast, glucose and the soluble protein albumin were decomposed independently of each other.     

季节性冻融土壤盐分离子组成与冻结层盐分运移规律研究

该文对冻融过程中土壤盐分离子组成及冻结层盐分运移规律进行研究,在内蒙古河套灌区永联试验站开展了冻融期土壤水盐及其离子成分监测试验,分析了冻融期地温、冻结层深度、地下水埋深与水质、土壤含水率、土壤盐分及离子组成的变化规律,通过离子相关性分析确定了土壤盐分运移的主控离子成分和盐分类型,进一步利用二元水盐体系相图探讨了冻融期主控盐分的运移规律。结果表明:冻融期地温梯度变化主要发生在0～1.0 m范围土层中,地下水埋深在冻融期变化趋势为快速增大-缓慢增大-减少,地下水矿化度均值在融化期显著降低;研究区地下水中变异性最大的离子为Na~+、Cl~–和SO_4~(2–),土壤盐分运移和扩散是地下水矿化度变化的主要原因;土壤中Na~+、Cl~–与SO_4~(2–)与含盐量相关系数高于0.9,冻融期土壤盐分浓度变化的主控盐分类型为氯化钠和硫酸钠;冻结层积盐或者脱盐取决于土壤盐分梯度和不同盐分的共饱和点,研究区最大氯化钠浓度(质量分数1.55%)和最大硫酸钠浓度(2.01%)均低于各自的共饱和点,当冻结前土壤溶液浓度梯度为正(从上到下浓度增大)时,冻结层易积盐,反之冻结层主要表现为脱盐。研究对阐明冻融期冻结层盐分累积规律的成因具有重要意义。     

土壤压实指标在城市土壤评价中的应用与比较

通过测定南京市不同土地利用下的52个样点的紧实度、容重和孔隙度3个压实指标来反映城市土壤的压实程度。结果表明,南京市大多数土壤存在不同程度的压实,部分压实严重,可能限制植物的生长。不同压实指标在反映土壤压实程度上基本一致,它们之间具有极显著的相关性,可以相互转换。但紧实度指标受到土壤含水量的显著影响。在同一质地或质地相近的土壤,容重和孔隙度可以很好地反映土壤的压实程度。与总孔隙度和毛管孔隙度相比,通气孔隙度在反映土壤压实时更为敏感。所以在进行城市土壤压实状况评价时,可以选择不同的土壤压实程度指标,但就方法的实用性和可靠性来说,容重比紧实度和孔隙度指标一般更方便可靠。     

Grass-induced changes in properties of soils in urban green areas with emphasis on mobility of metals

Purpose

Green areas in urban parks are special ecosystems because of social and ecological benefits.

Materials and methods

We investigated the ecological impacts of green spaces by comparing the properties of soils, with emphasis on metals, in green spaces and bare soil playgrounds in four urban parks in Murcia City (SE Spain).

Results and discussion

Organic matter (OM) contents in green areas are higher than playground soils due to litter decomposition from grass. Cation exchange capacity in green areas ranged from 10 to 14 compared to 2 cmol₊kg^?1 in playground soils, showing the effect of OM (and clay) contents in green areas due to the presence of vegetation. Soil total metal contents in urban parks are below the environmental threshold values for soils in Spain and other European countries, and come from atmospheric deposition and fertilizers application. Diethylenetriaminepentaacetic acid (DTPA)-extractable soil Cd in green areas (4% of total Cd) is lower than in playground soils (58% of total Cd). We attributed the reduced DTPA- and water-extractable Cd, Co, Cr, Mn, and Mo to the formation of stable complexes between metals and OM produced from the continued decomposition of roots of grasses in green spaces.

Conclusions

Grasses accumulate less metal than soils except in roots where Cr and Zn are higher than soils by as much as 31 and 17%, respectively. We conclude that grasses increased (up to 8×) soil OM content in green areas to significantly increase the ability of soils to accumulate nutrients for plants, and to retain and reduce the mobility and toxicity of metals in soils in urban parks.     

皖南不同质地土壤烤后烟叶中性香气成分含量及焦甜香风格的差异

取皖南3种不同质地土壤生产的烤后烟叶样品进行中性香气物质和常规化学成分含量测定,并进行单料烟感官评吸鉴定.结果表明,砂壤土各部位烟叶的类胡萝卜素降解产物、糖类降解产物含量、中部叶的西柏烷类降解产物茄酮含量、下部叶的苯丙氨酸裂解产物含量水平相对较高.常规化学成分中总糖含量和烟碱含量均较高,糖碱比适宜,评吸认为其感官质量优良,焦甜香突出.水稻士下部和中部叶类胡萝卜素降解产物含量、中部叶茄酮含量偏低,而上部叶苯丙氨酸裂解产物和类胡萝卜素降解产物较高,总糖含量较低,上部叶烟碱和总氮含量偏高,糖碱比偏低,焦甜香不显著,上部叶虽香气量大,但劲头偏大.砂壤土烟叶一般变现为中上部烟叶各类香气物质含量偏低,总糖含量较高,但含氮化合物含量偏低,糖碱比偏高,评吸认为焦甜否弱,烟叶香气量偏小.     

重金属污染土壤的植物修复研究Ⅱ.金属富集植物Brassica juncea根际土壤中微生物数量的变化

本文在盆栽试验的基础上研究了在不同程度的外源重金单一及复合污染下富金属植物印度芥菜(Brassica juncea)根际土壤中微生物数量的变化.研究结果表明,根际中细菌的数量明显多于放线菌、真菌.细菌生长对重金属和植物生长最敏感,其次为放线菌.含高镉(200mg/kg)的金属复合污染处理对细菌、放线圈的生长有抑制作用;加铜(250mg/kg)对细菌有刺激效果.在低于重金属致死临界浓度时,植物根系的存在对细菌的数量的影响会大于重金属元素的影响.印度芥菜根际土壤中微生物数量的变化与微生物种类、重金属元素及组合和植物生长有关.