Comparison of ceramic suction cups and KC1 extraction for the determination of nitrate in soil

Comparisons of nitrate concentrations in soil core extracts and ceramic suction cup isolates were made on a coarse sand and a sandy loam to evaluate the methods for estimating nitrate concentrations percolating through the root zone. On the coarse sand the comparisons were made at 80 cm on three dates during the winter of 1988/89. For each date, 103 soil samples and 101 or 102 suction cup isolates were taken. On the sandy loam the comparisons were made at 25 and 80 cm on two dates in March 1990. For each date and depth, 57 soil samples and 55–57 suction cup isolates were taken. On the coarse sand the mean nitrate concentrations were the same for the two methods. On the sandy loam the results obtained using the two methods differed significantly in only one of the four comparisons. However, the results indicated that the suction cup isolates differed slightly from the volume-averaged concentrations obtained from the soil samples. The type of frequency distribution, normal or lognormal, seemed to be influenced both by the mean nitrate concentration and by the soil structure, and thus by the pattern of percolation. The size of sample required to estimate the mean nitrate concentration with a probability of 95% and a precision of 10% varied from 7 to 106.     

Evaluation of porous ceramic cups for monitoring soil-water aluminium in acid soils: comment on a paper by Raulund-Rasmussen (1989)

Following recent observations by Raulund-Rasmussen (1989) implicating A1 contamination of soil solutions isolated by suction-cup samplers, A1 release from porous ceramic cups in acid solutions was investigated. In our studies a flush of Al, followed by a gradual decrease in leaching over successive extractions was observed. The amount of Al released was retarded by the presence of 37 μmol dm^?3 of A1 in solution. Gibbsite solubility controls were not observed; all solutions isolated by the cups were undersaturated with respect to amorphous gibbsite. The cups evaluated in this study are appropriate for sampling acidic soil solution, provided they are suitably pretreated and then equilibrated in the field before use.     

Sorption of phosphate and oxalate by a synthetic aluminium hydroxysulphate complex

We studied the sorption of phosphate and oxalate on a synthetic aluminium hydroxysulphate complex and the associated release of sulphate from this complex. In the pH range 4.0–9.0 the presence of phosphate or oxalate tended to increase the release of sulphate. Much more phosphate than oxalate was sorbed, but in most cases oxalate caused more removal of sulphate than did phosphate. Only in acid systems may these results be partly attributed to the greater solubilization of the complex in the presence of oxalate than in the presence of phosphate. At pH > 8.0 in the presence of phosphate, and at pH > 6.5 in the presence of oxalate, the quantities of sulphate replaced were greater than the quantities of phosphate or oxalate sorbed, suggesting that hydroxyl ions competed with phosphate and oxalate for sorption sites and sulphate removal. Sulphate was only partly removed from the complex even after repeated washings with phosphate or oxalate solutions or after 120 h in the presence of these ligands at pH 6.0. When phosphate and oxalate were added as a mixture much more phosphate than oxalate was retained. Phosphate strongly inhibited oxalate sorption, whereas oxalate partly prevented phosphate sorption only at pH < 7.0. More sulphate was removed in the presence of both the anions than in the presence of phosphate alone, but less than that desorbed in the presence of oxalate alone.     

Aluminium contamination of acid soil solution isolated by means of porcelain suction cups: a reply to a paper by Hughes & Reynolds (1990) and an interpretation of aluminium release

Possible aluminium contamination of acid soil solutions isolated by use of porous porcelain suction cups (‘P.80 type’) was reported by Raulund-Rasmussen (1989). The aluminium release was explained by a proton-induced dissolution of cup material. Hughes & Reynolds (1990) suggested that the aluminium release and proton consumption could be explained by an ion-exchange reaction. In an attempt to understand the mechanism and thereby also the usefulness of suction cups, laboratory experiments were carried out to define mineralogical and chemical composition, stability under acid conditions, cation exchange capacity, and reactivity under conditions relevant to the field. The cups consisted of mullite and corundum (65% Al₂O₃) as shown by X-ray diffraction analysis. The cation exchange capacity of the cups was too low (0.65 μmol_c per cup) to explain the observed contamination of isolated soil solution. Ground cup material dissolved slowly in acid. Investigations on whole cups showed that aluminium release to acid test solutions depended on the time of exposure. It is concluded that porcelain suction cups may lead to contamination of isolated soil solution depending on: (i) the intake rate, (ii) the rinsing procedure before sampling, and (iii) the composition of the soil solution (pH and aluminium ion activity being important parameters).     

Developments in the use of porous ceramic cups for measuring nitrate leaching

Porous ceramic cups are widely used for measuring nitrate leaching from agricultural land, but it is not fully clear what procedures give the most reliable results, or what factors could limit the validity of their use. This paper reports improvements in methodology made during tests of the technique when it was first used on a large scale, on light soils. Porous cup assemblies must be installed carefully to avoid preferential flow through the disturbed soil around them, and to maximize contact between cup and soil. Newly-installed and well-established porous cups could give differing results. Sampling must start as soon after return to field capacity as possible, when concentrations are often highest. The estimate of nitrate loss can be greatly affected by the calculated date of start of drainage, and some independent check on this date is advisable. Sampling frequency must be sufficient to define the shape of the curve of concentration against drainage, but this curve is normally fairly smooth. Methods of calculating nitrate loss are discussed. The spatial variability between cups in arable soils is typically 30–60% of the mean, less than between individual soil samples. Because porous cups can be left in situ, changes over time are not confounded with changes due to sampling from differing locations, as they are with successive soil samples.     

Sorption of trace quantities of cadmium by soils with different chemical and mineralogical composition

Cadmium sorption experiments were performed using four soil separates of different chemical and mineralogical composition, adding Cd solutions with initial concentrations ranging from 15 to 150 μg l^?1. At the soils pHs, the sorption isotherms were a mixture of a constant partition isotherm with a high affinity one. Also, more than 90% of the initially added Cd was sorbed by all four soils. These results indicate a high affinity of these soils for trace amounts of Cd. The effect of pH was, in general, to decrease the amount of sorbed Cd as the pH decreased. The sorption isotherms were linear at all pH's. Also, the data fitted the Freundlich's sorption isotherm in all cases, but not Langmuir's. Freundlich's k values were found to be a good index of the relative Cd sorption affinities of the four soils at all the pH's used. It was found that the structural and chemical nature of the soils sorbent complex was a more important parameter than the CEC when studying the sorption of these trace amounts of Cd by soils.     

Sorption of phosphate by aluminium and iron(iii)-hydroxy species on mica surfaces

Freshly cleaved mica sheets with aluminium- or iron(III)-hydroxy species on the cationexchange surface were prepared by suitable treatment with AlCl₃ or FeCl₃. These surfaces were considered as model soilk mineral surfaces and their interaction with phosphate studied using techniques previously developed for the study of single planar surfaces.Adsorption isotherms for both the iron(III) and aluminium systems were very similar and could be interpreted as two Freundlich isotherms indicating two different adsorption processes, one operating below a solution concentration of 10^?5 M and thee other above. Results obtained from the continuous monitoring of adsorption indicate that a rearrangement of adsorbed phosphate occurs with time on both the aluminium- and iron(III)hydroxy surfaces. This rearrangement reduces the rate of desorption and could be a cause of phosphate fixation in soils.     

Sorption of heavy metals by iron-manganic nodules in soils of Primorskii region

The accumulation and deactivation (detoxification) of heavy metals in soils and in soil iron-manganic nodules have been studied. Data on the relative distribution of the total and mobile compounds of heavy metals in soils and nodules upon different rates of technogenic loads are obtained. It is shown that iron-manganic nodules play the role of specific depositors in the soil system, affect the redistribution of heavy metals in the soil cover, and control their migration in the soil profiles.     

Effect of concentration on uptake of some trace metals by plants

Abstract

The uptake by plants of somes trace metals at different concentrations was related closely to the decay constant, I. This means that for a 10‐fold increase in applied concentration, the increase in uptake was close to 4. 93 (10^0.693 = 4. 93). With some trace metals the value of Y (10^Y = ratio of uptake for 10‐fold increase in metal concentration was around 1. For generalized conditions the value of Y in the expression, (/ = uptake ratio, for different concentrations and varied around I. Some values of Y for whole plants were Ni, 0.699 with C.V. (coefficient of variation) 12.2%, Cu, 0.468 with C.V. 12.1%, Zn, 0.606 with C V. 31.5%, and Cd, 0.903 with C.V. 10.9%. From soil the values for shoots for Co were 0.855 (C.V. = 14.8%) without EDTA (ethylenediamine tetraacetic acid) and 0. 941 (C. V. = 20. 8%) with EDTA; for Cu with EDTA it was 0. 562 (C. V. = 25.8%). with EDTA; for Cu with EDTA it was 0.562 (C.V. =25.8%).     

Tolerance of rice plants to trace metals

Abstract

The tolerance of rice (Oryza sativa L. C.V. Earlirose) to various trace metal excesses was tested to determine if high levels of the trace metals found in some field‐grown plants were at toxicity levels. In one experiment, levels of 2200 μg Zn/g dry weight, 44 μg Cu/g dry weight, 4400 μg Mn/g dry weight, and 32 μg Pb/g dry weight in shoots of young plants had no adverse effects on vegetative yields. A level of 3160μgZn/ g dry weight decreased yields about 40% (P = . 05). In another test 51 μg Cu/g dry weight or 94 μg Pb/g dry weight did not decrease vegetative yields. Boron supplied at 10^‐3 MH₃BO₃ not only caused no toxicity but resulted in only 144 μg B/g dry weight in shoots. Root levels of Zn were about equal to those in shoots; Mn levels were lower in roots than in shoots (1/4 to 1/10); B levels were generally low in both shoots and roots with roots 1/10 that of shoots; Cu levels were higher in roots than in shoots. Rice was tolerant of a high level of Cr. The tolerance of rice to high levels of some trace metals in these experiments may be related to high P levels in plants.     

Deposition of trace metals in stream sediments

Sediment samples have been collected downstream from a Pb smelter and analyzed for Cd, Cu, Fe, Pb, and Zn. The concentrations of these trace metals decrease with increased distance from the smelter. The decrease in trace metal contant has been utilized to provide an indication of how rapidly artificially high levels of trace metals are reduced to the carrying capacity of a natural water. Equilibrium calculations are utilized to predict the water's intrinsic trace metal carrying capacity.     

Mapping of trace metals in urban soils

Spatial distribution maps depicting the concentrations of antimony, lead, tin, copper and zinc, and the presence of land-use units were generated for Mühlburg, a district of the City of Karlsruhe, Germany. The influence of the spatial land-use structure on the distributions of the element concentrations is statistically evaluated and discussed. The variography for Mühlburg shows an average range of 200-400 m for the spatial correlations of Sb, Pb, Sn and Zn. The variograms of Pb and Zn are characterised by hole effects at 300 m distances, i.e. the result of repeated stronger spatial correlations for certain distances between the sample sites. Most probably, this is an effect of the typical urban structure of streets, buildings, green spaces, and industry. Kriging method was used for the interpolation of Sb, Pb, Sn and Zn concentrations. Only Cu does not show a spatial correlation. In this case, the interpolation was carried out with a smoothed triangulation routine. Pollution plumes of point sources such as lead works, a bell foundry and a coal-fired thermal power station superimpose the more diffuse pollution from traffic, household heating processes, waste material disposal, etc. The trace element concentrations in soils of housing areas increase with the age of the developed area. Industrial areas show the highest level of pollution, followed by housing areas developed before 1920, traffic areas, allotments, housing areas developed between 1920 and 1980, parks and sports areas, cemetery and housing areas developed after 1980. It is demonstrated that spatial distribution maps of element concentrations indicate potential emission sources of harmful substances, even if the emission itself or the direct surrounding soil have not been analysed. The analytical tools presented enable town planners to discern areas of higher soil pollution. Detailed investigations can be focussed on these areas to evaluate the possibilities of soil usage and transfer. These methods enable one to manage urban soil in an adequate manner. For these reasons, the methods demonstrated support an urban environmental impact assessment and are a part of a sustainable urban soil management.     

Evaluation of porous cup soil-water samplers under controlled field conditions: comparison of ceramic and PTFE cups

The value of soil water samples used in ecological studies is highly dependent on the quality of the samplers. Tension soil-water samplers are widely used to extract soil solutions, and the samplers are often tested in the laboratory under conditions that differ significantly from field conditions. This study describes a field procedure useful for comparison of two different tension soil-water samplers. Ceramic and PTFE cups are compared. There were no differences in the concentrations sampled by the two different types of sampler for Na⁺, K⁺, Ca²⁺, Al³⁺, NH₄⁺, H⁺ and NPOC (non-purgeable organic carbon). Change in the applied vacuum in the range 0 to –0.4 × 10⁵ Pa did not change the concentrations of chemical species in the collected soil water. The ceramic cups collected significantly larger amounts of water due to differences in the hydrostatic characteristics of the two samplers. It was found that the ceramic samplers collected the highest concentrations of Mg²⁺ in some situations. The results are evaluated and discussed in relation to the possible sources of errors and the temporal and spatial variabilities.     

Concentration and deposition of trace metals in Ontario-1982

Results of trace metal concentrations in air and precipitation and the corresponding wet and dry deposition in Ontario in 1982 arc reported. In terms of the spatial patterns, in general, there was a decreasing gradient from south-to-north in both concentration and deposition. Patterns differed with each parameter although certain groups of metals (e.g., Fe and Al; Pb, Zn, and Mn) displayed similar patterns. In general, wet deposition was greater than dry deposition at all sites. Geographically, the variability in the wet to dry deposition ratio for coarse particles (MMD > 2.5 μm) was small. However, it increased from the south to the north for fine particles (MMD < 2.5 μm), being higher away from the source areas. Scavenging ratios (W) have been derived from the precipitation and air concentrations of trace metals. The scatter in W is quite large for all trace metals, up to 2 orders of magnitude. There was little seasonal variability in W for fine particles (Pb, Mn, Zn, and Cd). However, coarse particles (Fe, Al, and Cu) were more efficiently scavenged by snow than by rain.     

Origin,retention and release of trace metals from sediments of the river seine

Metallic contents (Fe, Mn, Pb, Cu, Cd, Zn, Cr) of sediments were measured in 14 sites in the River Seine (France) along 110 km; in three sites surrounding the sewage treatment plant at Achères, vertical profiles were established from cores and dialysis cells, and interface exchanges have been studied. Metal contamination increases downstream, except for Pb for which contamination is higher immediately downstream of stormdrains (up to 130 mg kg^?1); that confirms its urban origin. Upstream of Achères, metallic contamination increases with depth while downstream, contribution to sediments of suspended matter from the treatment plant, loaded with organic matter, alters the behaviour of metals within the first ten centimeters. A strong link between particulate organic carbon (POC), polycyclic aromatic hydrocarbons (PAH), polychlorobiphenyls (PCB) and metal contents has been established. The organic matter brought down by the treatment plant effluents induces a specific diagenesis downstream leading to metal release in summer as attested by a 30% metal contents decrease in sediments. Calculation of molecular diffusion fluxes shows that in september, the release phenomenon is ending.     

Immobilization of trace metals and arsenic by different soil additives: Evaluation by means of chemical extractions

Abstract

Soils were amended with metal and arsenic (As) immobilizing soil additives [steel shots (SS 1% w/w), beringite (B 5% w/w), combination steel shots+beringite (SSB 1% SS + 5% B), hydroxyapatite (HA 0.5,1, and 5% w/w)]. The effectiveness of the additives in reducing metal and As mobility was assessed by means of chemical extractions with 1M calcium nitrate [Ca(NO₃)₂] in the case of metals and distilled water in the case of As. Among the additives tested, B, SSB, and 5% HA were most effective in reducing the mobility of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Moreover, the effect of these additives was consistent in the different soils and their use might, therefore, be more or less universal. The lowest amount of As was extracted in soils amended with B, SS, and SSB. The effect of B was, however, soil dependent. The addition of HA led to higher As mobility due to the phosphate‐arsenate competition for the sorption complex of the solid soil phase. Therefore, the use of HA at combined metal‐As polluted sites has to be taken with care. Based on this study, it can be concluded that the addition of SSB seems the most promising treatment for the remediation of mixed metal‐As polluted sites.     

Atmospheric input of trace metals to Lake Michigan

Atmospheric bulk deposition was collected on a monthly basis in the Lake Michigan basin from September 1975 through December 1976 to determine the atmospheric loading of trace elements to Lake Michigan. The sampling network consisted of bulk collectors located at 21 locations in the northern and southern basin. Atmospheric loading rates to Lake Michigan were estimated as (in units of 10⁵ kg yr^?1): Al-50; Fe-28; Mn-6.4; Zn-11; Cu-1.2; Pb-6.4; Cd-0.11; Co- <0.25; Ca-798; Mg-155; Na-110; K-64. Atmospheric deposition of all elements measured was greater in the southern basin than in the northern basin as a result of intense urban/industrial activity in the former. The percentage of total atmospheric deposition falling in the southern basin was: Fe-74%, Al-71%; Mn-75%; Zn-67%; Cu-62%; Pb-78%; Cd-74%; Co- ti 56%; Ca-79%; Mg-62%; Na-65%; K-61 %. Atmospheric loading rates reported are in general agreement with estimates made by others from emission inventories and aerosol concentrations. Atmospheric loadings were estimated to represent 10% or more of the total loadings to Lake Michigan from tributary and erosion sources for the trace elements Mn, Zn, Cu, Cd and Pb. Also, atmospheric deposition may account for recent accumulations of Zn, Cu, Cd, Pb and Co in southern Lake Michigan surficial sediments. The atmospheric Ph flux to southern Lake Michigan was estimated as ～1.7 μg sm^?2 yr^?1 for 1975–1976 which compares favorably with the 1972 anthropogenic Pb flux of 1.3 μg cm^?2 yr^?1 (total ? ～1.5 μg cm^?2 yr^?1) as determined from Pb-210 dating (Edgington and Robbins, 1976). The geographical distribution of trace element loading implicates the southern periphery of Lake Michigan as the principal emission source area.     

Sorption of polycyclic aromatic hydrocarbons to soils enhanced by heavy metals: perspective of molecular interactions

Purpose

Combined pollution by polycyclic aromatic hydrocarbons (PAHs) and heavy metals are commonly found in industrial soils. This study aims to investigate the effect of the coexistence of heavy metals on the sorption of PAHs to soils. We focused specifically on the relationship of the sorption capacity with the estimation of the binding energy between PAHs and heavy metals.

Materials and methods

The sorption of typical PAHs (naphthalene, phenanthrene, and pyrene) to soils coexisting with heavy metals (Cu(II), Pb(II), and Cr(III)) was characterized in batch sorption experiments. The binding energy between PAHs and heavy metals in aqueous solution was estimated by quantum mechanical (QM) method using density functional theory (DFT) at the M06-2x/def2svp level of theory.

Results and discussion

Sorption capacity and nonlinearity of the PAHs to the soils were enhanced by the coexisting heavy metals. The extent of increment was positively associated with the hydrophobicity of the PAHs and the electronegativity and radius of the metal cations: Cr(III)?>?Pb(II)?>?Cu(II). The cation-π interaction was revealed as an important noncovalent binding force. There was a high correlation between the binding energies of the PAHs and K _f ′ (K _f adjusted after normalizing the equilibrium concentration (C _e) by the aqueous solubility (C _s)) (R ²?>?0.906), indicating the significant role of the cation-π interactions to the improved PAH sorption to soils.

Conclusions

In the presence of heavy metals, the sorption capacities of naphthalene, phenanthrene, and pyrene to soils were enhanced by 21.1–107 %. The improved sorption capacity was largely contributed from the potent interactions between PAHs and heavy metals.

     

An investigation of phosphate adsorbed on aluminium oxyhydroxide and oxide phases by nuclear magnetic resonance

The adsorption of phosphate by soil minerals controls availability of P to plants, but the chemical environments of adsorbed phosphate are poorly known. We used ³¹P MAS NMR to study the adsorption of phosphate on to boehmite (γ‐AlOOH) and γ‐Al₂O₃ with large surface areas. The solid phases were reacted in 0.1 m phosphate solutions at pH from 3 to 11 and in solutions with pH 5 at concentrations from 10^?1 m to 10^?4 m . The spectra suggested three different phosphate environments: (i) orthophosphate precipitated from the residual solution after vacuum filtering, (ii) surface‐adsorbed phosphate in inner‐sphere complexes, and (iii) Al‐phosphate precipitates on the surfaces of the minerals. The chemical shifts of both the inner‐sphere complexes and surface precipitates became progressively less shielded with increasing pH and decreasing concentration of phosphate solution. For the inner‐sphere complexes, we interpret these changes to be the result of decreasing phosphate protonation combined with rapid proton exchange among phosphate tetrahedra with different numbers of protons, which causes peak averaging. The chemical shifts of ³¹P of the Al‐phosphate precipitates were more negative than those of the surface phosphates at a given pH and solution concentration, probably because of a larger number of P–O–Al linkages per tetrahedron. The observed trend of decreasing shielding is probably due to the decreasing average number of P–O–Al linkages per tetrahedron combined with decreasing protonation and an increasing number of K⁺ next‐nearest neighbours. Even at small concentrations of phosphate solution, a significant amount of Al‐phosphate precipitate was present.     

Sources of bioavailable trace metals for earthworms from a Zn-, Pb- and Cd-contaminated soil

The sources of bioavailable metals for earthworms were investigated in a Zn-, Pb- and Cd-contaminated soil. Selective sequential extractions (SSE) of metals were performed on soil samples with different amounts of contamination and compared with the body burden concentration of metals in two earthworm species: Aporrectodea caliginosa and Lumbricus rubellus. The most labile forms (water extractable and exchangeable) of metals were poorly related with metal accumulation by the earthworms, except for Cd, whereas the moderately available forms (acid-soluble, bound to iron oxides and organic matter) were related to the pattern of metal accumulation by earthworms. This indicates that the ingestion of metals bound to soil components is likely to be a more important uptake route than the dermal uptake of dissolved ions for metals entering the body tissue of earthworms.