The dynamics of exchangeable cations in the environment of soils at Kampinoski National Park

A set of physico-chemical properties of soils: soil pH, hydrolytic acidity, alkaline exchangeable cations, cation exchangeable capacity (CEC), and base saturation were studied in six-year long investigations of ecto-humus (organic layer) and endo-humus (Ah horizon) horizons of forest soils at the Kampinoski National Park in Poland. The soil properties determined in the present study showed differentiated values, depending on the actual horizon, the type and degree of soil development advancement, the genesis of the soil parent material (bedrock) as well as on the development of plant community prevailing in given site.     

Soil acidification and foliar nutrient status of Ontario's deciduous forest in 1986 and 2005

To assess the impacts of the decline in sulphur (S) deposition over the past 20 years in Ontario, soil chemistry and sugar maple (Acer saccharum Marsh) foliar chemistry were measured at 17 sites in south and central Ontario in 2005 and compared with archived samples collected in 1986. Foliar S concentrations were lower in 2005, reflecting the decline in S deposition whereas foliar N remained unchanged, reflecting the lack of change in N deposition in Ontario. Mineral soil pH, exchangeable base cations were lower in 2005 whereas total S, N and cation exchange capacity (CEC) were unchanged. Foliar concentrations of Ca were positively related to soil Ca levels in the A-horizon and were lower in 2005. Despite evidence of increasing soil acidity and losses of calcium, foliar base cation concentrations at most sites were adequate for sugar maple and forest health in terms of canopy appearance (Decline Index) improved.     

Assessment of environmental impact zones in the Kola Peninsula forest ecosystems

This paper describes the condition of forest ecosystems subjected to smelter pollution in the Kola peninsula. This assessment is based on the parameters of the biogeochemical cycle. The defoliation index was used to delimit three basic forest states: background, defoliating, sparse. Close to the smelter, due to expansion of the area not covered by vegetation, a fourth type of state, so-called "industrial deserts", has been observed. The concentrations of sulphur, copper and nickel in the precipitation in the forests generally declined with distance from the smelter. The defoliating forests are noted for the highest Ca, Mg, K concentrations in the summer precipitation. In sparse forests and industrial deserts a decrease in the Ca, Mg, K concentrations in the summer precipitation in comparison with the defoliating forests, despite the particle emissions, could be attributed to the reduction in forest biomass. The higher levels of soil and soil leachate carbon and acidity in the defoliating forests was due to higher litterfall and to the higher dissolution of fulvic acids by the acidic precipitation. This increase in organic matter levels affects soil cation exchange capacity and cation saturation. The pine trees demonstrated significant changes in the uptake of elements in all types of forests under pollution. Elevated levels of S, Ni, Cu and K and reduced levels of Mg, Mn and Zn were found in the needles of different age classes.     

Modelling long-term cation supply in acidified forest stands

A dynamic soil chemistry model was used to explain the observed decrease in soil base saturation between 1949 and 1984 at three stands in southern Sweden. The results show that acid deposition has caused soil acidification. The model, SAFE (Soil Acidification in Forest Ecosystems), includes the fundamental physical processes such as leaching and accumulation, and chemical processes such as cation exchange, mineral weathering, nutrient uptake and solute equilibrium reactions. The sources and sinks of base cations in the soil system were quantified, showing that weathering, deposition of base cations and depletion of exchangeable base cations supply cations to the soil solution in similar amounts in the upper 1 m during the acidification phase. This demonstrates that budget studies alone cannot be used to distinguish between long-term capacity to resist acidification, represented by weathering, from short-term buffering caused by cation exchange.     

Use of sequential extraction to assess metal partitioning in soils

The state of heavy metal pollution and the mobility of Cd, Cu, Ni, Cr, Pb and Zn were studied in three texturally different agricultural soil profiles near a Cu-Ni smelter in Harjavalta, Finland. The pseudo-total concentrations were determined by an aqua regia procedure. Metals were also determined after division into four fractions by sequential extraction with (1) acetic acid (exchangeable and specifically adsorbed metals), (2) a reducing agent (bound to Fe/Mn hydroxides), (3) an oxidizing agent (bound to soil organic matter) and (4) aqua regia (bound to mineral structures). Fallout from the smelter has increased the concentrations of Cd, Cu and Ni in the topsoil, where 75-90% of Cd, 49-72% of Cu and 22-52% of Ni occurred in the first two fractions. Slight Pb and Zn pollution was evident as well. High proportions of mobile Cd, Cu and Ni also deeper in the sandy soil, closest to the smelter, indicated some downward movement of metals. The hydroxide-bound fraction of Pb dominated in almost all soils and horizons, while Ni, Cr and Zn mostly occurred in mineral structures. Aqua regia extraction is usefully supplemented with sequential extraction, particularly in less polluted soils and in soils that exhibit substantial textural differences within the profiles.     

Ni and Cu migration and accumulation in forest ecosystems on the Kola Peninsula

Biogeochemical cycles of Ni and Cu in pine forests on the northern tree line (Kola peninsula) in the background and industry-disturbed areas have been investigated. Total, bio-available and exchangeable concentrations of Ni and Cu in the soil, atmospheric Ni and Cu fluxes and soil water migration, and metal uptake by plants are considered. In the polluted area, forest ecosystems are seen as biogeochemical barriers which may attenuate intensity of Ni and Cu migration down the soil profile. A quantitative assessment is given of the role of dominating forest plants and soil horizons as barriers to heavy metal fluxes.     

Mobility of heavy metals as related to soil chemical and mineralogical characteristics of Brazilian soils

In order to better understand the relationship between soil characteristics and mobility of some heavy metals, correlation studies were conducted in samples of unlimed and limed A, B and C horizons of three Brazilian soils, representative of the majority of the tropical soils. A number of chemical and mineralogical characteristics of one Oxisol and two Ultisols were related to the retardation factors (Rf) for zinc (Zn), cadmium (Cd), copper (Cu) and lead (Pb). The retardation factors, obtained in leaching column experiments, were used as an estimate of solute movement in the profile. Soil types and soil horizons were found to influence metal retardation factors which, in turn, correlated better with the chemical than the mineralogical soil characteristics. For the unlimed soil samples, the soil characteristics that significantly correlated with Zn-Rf and Cd-Rf were the sum of exchangeable bases (SB), and soil exchangeable (Ca-KCl) and non-exchangeable (Ca-HCl) calcium contents. These results showed the strong influence of the cation exchange phenomenon on the retention and mobility of these two metals. For Cu and Pb, not only SB, cation exchange capacity (CEC) and Ca-KCl and Ca-HCl but also the organic matter correlated well with the Rf, showing that complex or chelate formation may play an important role in the movement of these elements. The important soil chemical characteristics related to the retardation factors in the limed soil samples were SB for Cd, and Ca-HCl for Cu and Pb, suggesting that precipitation may also influence the mobility and retention of the latter two heavy metals in these soil samples. Soil pH influenced the heavy metals adsorption and movement as shown by the significant correlation with the retardation factors when the combined data for the unlimed and limed soil samples was considered.     

Element concentrations in the forest moss Hylocomium splendens: variation associated with altitude, net primary production and soil chemistry.

Net primary production (NPP) of the forest moss Hylocomium splendens increased significantly along an elevational gradient in the southern Alps of Italy. Extracellularly bound metals (Al, Ca, Co, Cr, Fe, Ni, Mo, Ni, Pb) showed declining concentrations in moss tissue with increasing altitude, presumably because the amount of exchange sites on the cell wall increases less than total biomass. Concentrations of intracellular elements did not vary (Cd, Cu, Mg, Na, Zn), or even increased (K) with altitude. The observed patterns were always independent of precipitation amount and soil concentrations of exchangeable elements. A higher soil nutrient status only enhanced K uptake by the moss. We concluded that variations in moss NPP, associated with elevational gradients, may significantly affect estimates of atmospheric deposition based on moss analysis in mountainous regions.     

Nutrient leaching from conifer needles in relation to foliar apoplast cation exchange capacity

Limited evidence to date suggests that acidic precipitation promotes leaching of nutrient cations from conifer foliage. In order to evaluate the relative contribution of the apoplast cation exchange complex and symplast nutrient pools to the leached ions, the magnitude of foliar leaching in response to acidic solutions was compared to foliar apoplast cation exchange capacity (CEC) for two conifer tree species (Pseudotsuga menziesii and Picea engelmanii). Leaching potential was determined by immersing detached needles in acidic solutions (pH5.6, 3.1, 2.1) over a range of time intervals (1, 4, 8, 24 h) and foliar apoplast cation exchange capacity was determined by potentiometric titration. Leaching increased with decreasing pH and increasing time of immersion. At pH values 2.1 and 3.1, equivalents of H+ depleted from the acidic solutions approximated equivalents of base cations gained by the solutions. Maximum amounts leached were less than 40 microeq g(-1) dry weight of needles for the combination of calcium, magnesium and potassium. Measured foliar apoplast CEC for these species was approximately 120 microeq g(-1) dry weight of needles. These relative magnitudes indicate that the apoplast rather than the symplast provided the leached ions. Because the apoplast foliar cation exchange capacity appears to be large relative to the rates of H+ diffusion across the cuticle, it may help to insulate the symplast nutrient reservoir from exposure to the H+ of acidic solutions bathing the foliage.     

Pyrolysis temperature influences ameliorating effects of biochars on acidic soil

The biochars were prepared from straws of canola, corn, soybean, and peanut at different temperatures of 300, 500, and 700 °C by means of oxygen-limited pyrolysis. Amelioration effects of these biochars on an acidic Ultisol were investigated with incubation experiments, and application rate of biochars was 10 g/kg. The incorporation of these biochars induced the increase in soil pH, soil exchangeable base cations, base saturation, and cation exchange capacity and the decrease in soil exchangeable acidity and exchangeable Al. The ameliorating effects of biochars on acidic soil increased with increase in their pyrolysis temperature. The contribution of oxygen-containing functional groups on the biochars to their ameliorating effects on the acidic soil decreased with the rise in pyrolysis temperature, while the contribution from carbonates in the biochars changed oppositely. The incorporation of the biochars led to the decrease in soil reactive Al extracted by 0.5 mol/L CuCl₂, and the content of reactive Al was decreased with the increase in pyrolysis temperature of incorporated biochars. The biochars generated at 300 °C increased soil organically complexed Al due to ample quantity of oxygen-containing functional groups such as carboxylic and phenolic groups on the biochars, while the biochars generated at 500 and 700 °C accelerated the transformation of soil exchangeable Al to hydroxyl-Al polymers due to hydrolysis of Al at higher pH. Therefore, the crop straw-derived biochars can be used as amendments for acidic soils and the biochars generated at relatively high temperature have great ameliorating effects on the soils.     

Is tree growth reduction related to direct foliar injuries or soil chemistry modifications?

In the context of intense emissions causing atmospheric pollution, tree growth reductions could be related to soil chemistry modifications or direct foliar injuries. To verify these hypotheses, mineral soils were sampled in an area (Murdochville, Canada) where previous studies had demonstrated that tree growth was impacted by smelter emissions and that forest floor lead concentrations could be used as a proxy for atmospheric pollutant depositions. Samples were analysed for Al, Pb (concentrations and isotope ratios), basic cations (Ca, K, P, and Mg) and Zr. Mass balance calculations were performed on soil profiles to assess vertical migration of elements. Pb concentrations in litter diminished gradually with distance from the smelter. The Pb isotope ratios in these organic soil layers were close to those measured in the Murdochville ores. These patterns were not encountered in mineral soil layers. Pb isotope ratios in these layers were close to those measured in uncontaminated geological materials, and Pb concentrations and basic cation depletions were not related to the proximity of the smelter. Growth reduction was closely associated with litter Pb concentrations, which were used as a proxy for atmospheric deposition, but was not correlated with any elemental concentration or cation depletion measured in mineral soil layers. Our overall results suggest that trees responded mainly to direct atmospheric emissions, which caused foliar damage, rather than to soil chemistry modifications.     

Impact of soil quality on elemental uptake by, and distribution in, Colocasia esculenta (Amadumbe), an edible root

In this study the elemental distribution of selected essential (Ca, Mg, Al, Mn, Cu, Fe, Co, Cr, Zn, Ni and Se) and the non-essential (Pb, Hg and As) elements were determined in the bulb and peel of Amadumbe (Colocasia esculenta) samples from eight different sites in KwaZulu-Natal, South Africa. The concentration of Se and As in the soil and in the Amadumbe bulbs were below the detection limit of 0.09 μg g?1. The total and bioavailable concentrations of the elements in conjunction with pH, soil organic matter (SOM) and cation exchange capacity (CEC) were determined in the soil samples from the eight sites. Statistical analysis was done to evaluate the impact of soil quality parameters on the chemical composition of the Amadumbe root. The results show accumulation or exclusion of certain elements by the bulb as evidenced by the noticeable increase or decrease of the concentrations of elements, respectively. Ca and Mg were found to be major elements in the range (2000-12000 μg g?1), whilst Mn, Zn, Fe and Al were found to be minor elements in the range (20-400 μg g?1). A general trend observed was that the plant favours the absorption of Zn over Cu. A positive correlation between Mg & Ca, Cu & Fe and Co & Ni was also observed. Statistical analysis revealed that the plant tended to accumulate Mg, Ca, Co, Cr and Pb whilst it excluded Hg and Fe, to a lesser extent.     

Impact of coal mine dump contaminated soils on elemental uptake by Spinacia oleracea (spinach)

The elemental uptake and the growth response of Spinacia oleracea (spinach) to the soil contaminated with the South African bituminous coal mine dump soil, viz. 0%, 5%, 15%, and 25% w/w, was investigated. The contaminated soils were analyzed for pH, cation exchange capacity (CEC), soil organic matter (SOM), and concentrations of selected heavy metals. The pH, SOM, and CEC decreased with an increase in contamination indicating the acidic nature of coal mine soil and the raise in the soil binding sites. The distribution of Fe, Mn, Ni, Cd, and Pb in the in roots and leaves of the plants was determined in two stages of plant growth. Spinach showed high accumulation of Fe and increased levels of Ni and Cd with an increase in contamination. No plant growth was recorded with 25% contamination.     

Changes in the concentrations of phenolics and photosynthates in Scots pine (Pinus sylvestris L.) seedlings exposed to nickel and copper

Studies were done on the effects of elevated soil concentrations of copper (Cu) and (Ni) on foliar carbohydrates and phenolics in Scots pine (Pinus sylvestris L.). Four year-old seedlings were planted in pots filled with metal-treated mineral forest soil in early June. The experimental design included all combinations of four levels of Cu (0, 25, 40 and 50 mg kg(-1) soil dw) and Ni (0, 5, 15 and 25 mg kg(-1) soil dw). Current year needles were sampled for soluble sugar, starch and phenolics at the end of September. Ni increased sucrose concentration in the needles, indicating disturbances in carbohydrate metabolism. Trees exposed to Ni had higher concentrations of condensed tannins compared with controls. In contrast, concentrations of several other phenolic compounds decreased when seedlings were exposed to high levels of Cu or to a combination of Ni and Cu. The results suggest that concentrations of phenolics in Scots pine needles vary in their responses to Ni and Cu in the forest soil.     

Fenuron sorption on homoionic natural and modified smectites

The adsorption isotherms of fenuron (1,1-dimethyl-3-phenylurea) on three smectites (SWy and SAz montmorillonites and SH hectorite) differing in their layer charge (SH相似文献   

Total vs. internal element concentrations in Scots pine needles along a sulphur and metal pollution gradient

Analysis of foliar elements is a commonly used method for studying tree nutrition and for monitoring the impacts of air pollutants on forest ecosystems. Interpretations based on the results of foliar element analysis may, however, be different in nutrition vs. monitoring studies. We studied the impacts of severe sulphur and metal (mainly Cu and Ni) pollution on the element concentrations (Al, Ca, Cu, Fe, K, Mg, Mn, Ni, P, Pb, S and Zn) in Scots pine (Pinus sylvestris L.) foliage along an airborne sulphur and metal pollution gradient. Emphasis was put on determining the contribution of air-borne particles that have accumulated on needle surfaces to the total foliage concentrations. A comparison of two soil extraction methods was carried out in order to obtain a reliable estimate of plant-available element concentrations in the soil. Element concentrations in the soil showed only a weak relationship with internal foliar concentrations. There were no clear differences between the total and internal needle S concentrations along the gradient, whereas at the plot closest to the metal smelter complex the total Cu concentrations in the youngest needles were 1.3-fold and Ni concentrations over 1.6-fold higher than the internal needle concentrations. Chloroform-extracted surface wax was found to have Ni and Cu concentrations of as high as 3000 and 600 microg/g of wax, respectively. Our results suggest that bioindicator studies (e.g. monitoring studies) may require different foliar analysis techniques from those used in studies on the nutritional status of trees.     

Fenuron sorption on homoionic natural and modified smectites

Abstract

The adsorption isotherms of fenuron (l, l‐dimethyl‐3‐phenylurea) on three smectites (SWy and SAz montmorillonites and SH hectorite) differing in their layer charge (SH<SWy<SAz) and saturated with several inorganic and organic cations were determined. The isotherms and sorption parameters from Freundlich equation indicate low adsorptivity on inorganic clays, but medium sorption in organoclays (OCls). Fenuron adsorption on homoionic smectites increases with decreasing layer charge and hydratation power of the inorganic exchangeable cation (except Fe³⁺), indicating that fenuron adsorbs as neutral molecule on uncharged siloxane surface by hydrophobic bonding, with some contribution of polar bond (fenuron C=O group and water associated to exchangeable cation). In the case of Fe³⁺‐saturated smectite fenuron protonation, provided by the interlayer acidic environment, promotes further sorption of fenuron as cationic form. The sorption on organoclays is enhanced via hydrophobic interaction with organocations, which is favoured for high layer charge and basal spacing and organocation saturation close to CEC. Quaternary alkylamonium is more efficient in high layer charge smectite, whereas primary alkylammonium is more efficient in medium charge smectite. The low values of the maximum sorption obtained with homoionic inorganic and organic smectites (100 and 5000 μmol/Kg) represent one fenuron molecule for each 2000–200 exchange sites and indicate that fenuron sorption is mainly associated to the outer exchange sites. This low adsorptivity of fenuron, as consequence of its high water affinity (high water solubility) would suggest high mobility of fenuron in natural soil and water systems.     

A model for evaluation of the phytoavailability of trace elements to vegetables under the field conditions

Currently, several single extraction methods are used for the evaluation of the phytoavailability of metals using pot experiments. A systematic comparison, however, is lacking. It is especially true for the field studies. This study was to investigate the phytoavailability of trace elements to vegetables grown on metal-contaminated soils under the field conditions. All soils collected were typical calcareous soils in northern China. Four frequently used methods using CaCl2, diethylenetriaminepentaacetic acid (DTPA), CH3COOH, and water as extractants were compared for phyto-availability. The concentrations of metals extracted by these four extraction methods ranged from 3.42 to 815, 1.51- 6965, 0.732-24473, 0.688-7863, 0.246-685, 1.99-5337 0.203-4649 ng/g for Cr, Ni, Zn, Cu, Cd, Pb and REEs, respectively. Simple correlation analysis indicated that a significant correlation (Cr: r = 0.5411**; Zn: r = 0.6352**; Cd: r = 0.6979**; Pb: r = 0.5537** and REEs: r = 0.5185** -0.6684**) was observed between the CaCl2-extractable metals in soil solution and that in Chinese cabbage. In addition, soil pH, organic matter (OM), and cation exchange capacity (CEC) also affect the phytoavailability. An empirical model was developed to express the combined effect of soil properties on the phytoavailability. The stepwise multiple regression analysis demonstrated that the phytoavailability of trace elements strongly correlated with the extractable fraction by CaCl2, total metal concentration in soils, and soil pH, OM, CEC. This model can describe approximately 75-95% of the variability of metal uptake and the r2 values ranged from 0.741** to 0.954**, which were much better than the single correlation analysis. For celery and cole, a strong correlation was obtained for Cr, Ni, Zn, Cu, Cd, La, Ce, Pr and Nd. For spinach and Chinese cabbage, however, a positive correlation was only observed for 1 and 3 metals, respectively. Generally, the developed empirical model can integrate the combined effects of soil properties, extractable metal fractions in soil solutions and plant species on the phytoavailability of metals to vegetables in the field conditions.     

Assessment of natural and calcined starfish for the amelioration of acidic soil

Quality improvement of acidic soil (with an initial pH of approximately 4.5) with respect to soil pH, exchangeable cations, organic matter content, and maize growth was attempted using natural (NSF) and calcined starfish (CSF). Acidic soil was amended with NSF and CSF in the range of 1 to 10 wt.% to improve soil pH, organic matter content, and exchangeable cations. Following the treatment, the soil pH was monitored for periods up to 3 months. The exchangeable cations were measured after 1 month of curing. After a curing period of 1 month, the maize growth experiment was performed with selected treated samples to evaluate the effectiveness of the treatment. The results show that 1 wt.% of NSF and CSF (700 and 900 °C) were required to increase the soil pH to a value higher than 7. In the case of CSF (900 °C), 1 wt.% was sufficient to increase the soil pH value to 9 due to the strong alkalinity in the treatment. No significant changes in soil pHs were observed after 7 days of curing and up to 3 months of curing. Upon treatment, the cation exchange capacity values significantly increased as compared to the untreated samples. The organic content of the samples increased upon NSF treatment, but it remains virtually unchanged upon CSF treatment. Maize growth was greater in the treated samples rather than the untreated samples, except for the samples treated with 1 and 3 wt.% CSF (900 °C), where maize growth was limited due to strong alkalinity. This indicates that the amelioration of acidic soil using natural and calcined starfish is beneficial for plant growth as long as the application rate does not produce alkaline conditions outside the optimal pH range for maize growth.     

Impact of soil quality on elemental uptake by,and distribution in,Colocasia esculenta (Amadumbe), an edible root

In this study the elemental distribution of selected essential (Ca, Mg, Al, Mn, Cu, Fe, Co, Cr, Zn, Ni and Se) and the non-essential (Pb, Hg and As) elements were determined in the bulb and peel of Amadumbe (Colocasia esculenta) samples from eight different sites in KwaZulu-Natal, South Africa. The concentration of Se and As in the soil and in the Amadumbe bulbs were below the detection limit of 0.09 μg g^?1. The total and bioavailable concentrations of the elements in conjunction with pH, soil organic matter (SOM) and cation exchange capacity (CEC) were determined in the soil samples from the eight sites. Statistical analysis was done to evaluate the impact of soil quality parameters on the chemical composition of the Amadumbe root. The results show accumulation or exclusion of certain elements by the bulb as evidenced by the noticeable increase or decrease of the concentrations of elements, respectively. Ca and Mg were found to be major elements in the range (2000–12000 μg g^?1), whilst Mn, Zn, Fe and Al were found to be minor elements in the range (20–400 μg g^?1). A general trend observed was that the plant favours the absorption of Zn over Cu. A positive correlation between Mg & Ca, Cu & Fe and Co & Ni was also observed. Statistical analysis revealed that the plant tended to accumulate Mg, Ca, Co, Cr and Pb whilst it excluded Hg and Fe, to a lesser extent.