Aluminium in tea plantations: mobility in soils and plants, and the influence of nitrogen fertilization

The levels of extractable aluminum (Al) in soils of tea plantations, Al concentrations in tea leaves and the impact of nitrogen fertilization on these two parameters were investigated. In addition, the properties of soils from tea plantations were compared to those from soils of adjacent non-tea fields to evaluate the effect of land use conversion (from non-tea soils to tea soils). Exchangeable Al (extracted in 1 mol l⁻¹ KCl) ranged from 0.03 to 7.32 cmol_c kg⁻¹ in 94 tea fields and decreased rapidly with increasing soil pH. In comparison with non-tea soils, tea soils had a significantly lower pH and exchangeable Mg²⁺ concentration but higher organic matter contents and exchangeable K⁺ concentration. Contents of extractable Al were not different (P > 0.05) between these two soils. The concentrations of Al in mature tea leaves correlated significantly with exchangeable Al in soil samples taken at a depth of 20–40 cm and with exchangeable Al saturations in soil sampled at␣depths of 0–20 and 20–40 cm. In the pot experiment, nitrogen fertilization significantly increased extractable Al levels but decreased soil pH and the levels of exchangeable base cations. Nevertheless, the levels of Al in mature leaves and young shoots were significantly reduced by the application of large amounts of N fertilizer.     

Zur Beständigkeit von Aluminiumchloridlösungen mit tridekameren Kationen (Al<Subscript><Emphasis Type="Bold">13</Emphasis></Subscript>)

Background, aim, and scopeThe focus of popular interest on the subject of acid rain has been on the effects, which it has on aquatic ecosystems. Aluminium toxicity and the bioavailability depend on the species of aluminium present. The cationic aluminium species are important for the phytotoxocity and for the precipitation of aluminium containing precipitate.Materials and methodsSpeciation diagrams of aqueous aluminium chloride solutions with tridecameric cations (Al₁₃) at room temperature as function of concentration (1·10^–1–1·10^–5 mol·l^–1 Al) and aging time (9 month) have been obtained from a kinetic method; these Ferron method offers a simple and inexpensive alternative for identification and quantification of aluminium cations.ResultsThe Al₁₃-cation stability decrease with decreasing concentration and increasing aging time.DiscussionPolynuclear aluminium species can be formed in nature by the dissolution of Al-containing minerals, as a consequence of surface water acidification, followed by neutralization process. The question of the occurrence of the tridecameric polycation (Al₁₃) in natural soil solutions and stream waters is of considerable interest.ConclusionsThe results are important on the occurrence of the Al₁₃ in natural waters, for the precipitation of aluminium species by acidification and for the aluminium phytotoxicity.Recommendations and perspectivesThis research suggests strongly that Al₁₃ should be negligible in natural soil and surface waters. The toxicity of Al₁₃ to plants and aquatic organism in natural conditions may be considered to be very low.     

Evidence for a new mechanism of Fe2O3 decomposition in lightweight aggregate formation

Hematite (Fe₂O₃) chemical reduction into FeO and Fe₃O₄ by releasing O₂ at high temperatures is considered one of the generally accepted mechanisms for processing waste minerals and clay into lightweight aggregate construction materials. In many case studies, this mechanism has not been strictly confirmed. To verify whether hematite can effectively release O₂ at 1,000–1,260°C, a material containing hematite, simulating waste sediments from a Taiwanese reservoir, was shaped into pellets and fired into lightweight aggregates at high temperatures for 20 min and studied with various techniques. As revealed by the X-ray absorption near-edge structure technique, almost all the hematite remained as Fe(III) in the pellets when fired at 1,000–1,260°C, implying a negligible release of O₂ leading to the creation of pores. This finding shows that the generally accepted mechanism for lightweight aggregate formation associated with hematite decomposition into FeO, Fe₃O₄, and O₂ is invalid. Furthermore, Fe(III)-containing composites were formed in the fired pellets. Although firing at 1,000°C can trigger the decomposition of the components K₂CO₃, Na₂CO₃, and CaCO₃ with a release of CO₂, the sintering reaction was seemingly too weak to encapsulate the gases effectively. For pellets fired at 1,050–1,150°C, pores grew in size because the sintering reaction sufficed to generate a glassy phase that could better encapsulate gases.     

Catalytic ozonation performance and surface property of supported Fe3O4 catalysts dispersions

Fe₃O₄ was supported on mesoporous Al₂O₃ or SiO₂ (50 wt.%) using an incipient wetness impregnation method, and Fe₃O₄/Al₂O₃ exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyacetic acid and para-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe₃O₄ on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO₂, more Lewis acid sites existed on the surface of Al₂O₃, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe₃O₄/Al₂O₃ exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment.     

Hg transfer from contaminated soils to plants and animals

Understanding the transfer of mercury (Hg) from soil to crops is crucial due to Hg toxicity and Hg occurrence in terrestrial systems. Previous research has shown that available Hg in soils contributes to plant Hg levels. Plant Hg concentrations are related to soil conditions and plant characteristics. Mechanistic models describing such soil–plant interactions are however difficult to quantify. Here we performed a field study in agricultural, mining and industrial areas in Portugal to evaluate potential food chain risks. The uptake of Hg by Italian ryegrass, ryegrass, orchard grass, collard greens and rye was measured to calculate daily intakes (DI) of Hg for cows and sheep grazing. A total of 136 soil samples and 129 plant samples were analysed. Results show that total Hg concentrations ranged from 0.01 to 98 mg kg⁻¹ in soils; 0.01–5.4 mg kg⁻¹ in shoots and 0.01–42 mg kg⁻¹ in roots. Calculated DI ranged from 0.18 to 132 mg d⁻¹ for cows, and from 0.028 to 23 mg d⁻¹ for sheep. In 27 grassland sites, daily intakes exceeded the acceptable daily intake of both cows and sheep in view of food safety considering Hg in animal kidneys evidencing potential risks to human health. The transfer of Hg from soil to crops was described using empirical Freundlich-type functions. For ryegrass, orchard grass and collard greens, the soil-to-root or soil-to-shoot transfer of Hg appeared to be controlled by the total soil Hg concentration and levels of Al_ox and Fe_ox. Empirical functions allowed us to obtain realistic estimates of Hg levels in crops and can be used as an alternative to mechanistic models when evaluating food chain risks of Hg contamination in agricultural soils.     

Availability of colloidal ferric oxides to coastal marine phytoplankton

Cell growth of a coastal marine diatom, Phaeodactylum tricornutum (stock cultures), and two red tide marine flagellates, Heterosigma akashiwo and Gymnodinium mikimotoi (stock cultures), in the presence of soluble chelated Fe(III)-EDTA (1:2) and of four different phases of ferric oxide colloids were experimentally measured in culture experiments at 20°C under 3000 lux fluorescent light. Soluble Fe(III)-EDTA induced the maximal growth rates and cell yields. The short-term uptake rate of iron by H. akashiwo in Fe(III)-EDTA medium was about eight times faster than that in solid amorphous hydrous ferric oxide (Fe₂O₃·xH₂O) medium. In culture experiments supplied with four different ferric oxide forms, the orders of cell yields are amorphous hydrous ferric oxide>-FeOOH (lepidocrocite)>Fe₅O₇(OH)·4H₂O (hydrated ferric oxyhydroxide polymer >-FeOOH (goethite). The specific growth rates () at logarithmic growth phase in Fe(III)-EDTA, amorphous hydrous ferric oxide and -FeOOH media were significantly greater than those in Fe₅O₇ (OH)·4H₂O and -FeOOH media. The thermodynamically stable forms such as Fe₅O₇(OH)·4H₂O and -FeOOH supported a little or no phytoplankton growth. The iron solublities and/or proton-promoted iron dissolution rates of these colloidal ferric oxides in seawater at 20°C were determined by simple filtration techniques involving -activity measurements of ⁵⁹Fe. The orders of solubilities and estimated dissolution rate constants of these ferric oxides in seawater were consistent with that of cell yields in the culture experiments. These results suggest that the availability of colloidal iron to provide a source of iron for phytoplankton is related to the thermodynamic stability and kinetic lability of the colloidal ferric oxide phases, which probably control the uptake rate of iron by phytoplankton.     

A Petrographic Investigation of two Sequential Extraction Techniques Applied to Anaerobic Canal Bed Mud

The application of sequential extraction procedures to determine metal speciation in sediments is fraught with uncertainty regarding what is actually dissolving or re-precipitating at each stage. In order to choose an appropriate scheme for the investigation of contaminated anaerobic mud two different sequential extraction procedures (Kersten and Förstner, 1986; Quevauviller, 1998) were investigated using a Cryogenic SEM (CryoSEM) technique coupled with energy dispersive X-ray analysis (EDXA). This enabled assessment of the degree of reagent selectivity and any re-precipitation associated with the respective methods. Analysis of the non-leached sediment revealed the most abundant authigenic minerals in order of decreasing abundance to be Fe²⁺-phosphate vivianite (Fe₃(PO₄)₂·8H₂O), mixed Fe, Zn, Cu sulphides, pyrite and calcite. After each stage of the sequential extraction the sediment residue was examined using CryoSEM. After extraction of the exchangeable fraction no obvious evidence of mineral dissolution was observed. Calcite was not completely dissolved during the carbonate extraction stage of either procedure. Vivianite began to dissolve in the carbonate extraction stage of both procedures and was completely dissolved by oxide extraction stage of both procedures. The sediment leached by acidified ammonium oxalate, contained abundant Fe oxalate crystals, suggesting that a large proportion of the Fe released from the vivianite has been re-precipitated. The Fe oxalate was then dissolved with the subsequent sulphide fraction. The technique used to extract the sulphide and organic fraction is the same in both schemes and no sulphide or metal rich organic matter was found in either residue.     

Trace Metal Contents (Al, Cu and Zn) of Tea: Tea and Soil from Two Tea Plantations, and Tea Products from Different Provinces of China

The present project aims to investigate the possible contamination of teas with the trace metals: Al, Cu and Zn. Tea bushes sampled from two tea plantations in the northern part of Guangdong Province accumulated higher concentrations of Cu and Zn in young leaves, and of Al in old leaves. The analysis of the three metals in tea produced in different provinces indicated higher Al levels in those obtained from Guangdong and Yunnan Provinces, which may be due to the lower soil pH in these areas. Green tea had the lowest Al concentration among the four types of tea studied, as only the bud and two young leaves are used, whereas older leaves are used for other types of tea (black, Oolong and Puerh tea). The transfer of Al, Cu and Zn from soil to different parts of tea bushes was low in general, except for Zn at Lechang tea plantation which next to a Pb/Zn mine, where a higher transfer was observed from young leaves to tea products, indicating possible metal contamination during tea processing. However, low concentrations of Cu and Zn (less than 0.07 mg Cu L^-1 and 0.17 mg Zn L^-1), and moderate amounts of Al (2.1-2.5 mg L^-1) were obtained in the tea liquor (1% hot water extracts).     

Dedication

Hydrochemical, multivariate statistical, and inverse geochemical modeling techniques were used to investigate the hydrochemical evolution within the Ain Azel aquifer, Algeria. Cluster analysis based on major ion contents defined 3 main chemical water types, reflecting different hydrochemical processes. The first group water, group 1, has low salinity (mean EC = 735 μS/cm). The second group waters are classified as Cl–HCO₃-alkaline earth type. The third group is made up of water samples, the cation composition of which is dominated by Ca and Mg with anion composition varying from dominantly Cl to dominantly HCO₃ plus SO₄. The varifactors obtained from R-mode FA indicate that the parameters responsible for groundwater quality variations are mainly related to the presence and dissolution of some carbonate, silicate, and evaporite minerals in the aquifer. Inverse geochemical modeling along groundwater flow paths indicates the dominant processes are the consumption of CO₂, the dissolution of dolomite, gypsum, and halite, along with the precipitation of calcite, Ca-montmorillonite, illite, kaolinite, and quartz.     

UV-C light-enhanced photo-Fenton oxidation of methyl parathion

The photodegradation of aqueous solutions containing 0.2 mM methyl parathion has been studied through the optimization of the [H₂O₂]/[Fe³⁺] ratio in a Fe³⁺/H₂O₂/UV-C flow system of 1.3 L capacity. The decay kinetics and TOC abatement have been analyzed for the experiments performed at pH 3.0 and room temperature. All experiments lead to the total methyl parathion destruction after a few minutes, following a pseudo-first-order decay kinetics. Total mineralization can be reached after 120 min at the optimum ratio found, due to the synergistic effect of the very oxidizing hydroxyl radical (^·OH) produced via the Fenton reagent and the effective photodecarboxylation at 253.7 nm.     

柠檬酸存在下酸性土壤中铝溶解动力学的初步研究

用一次平衡法研究了柠檬酸存在下砖红壤和红壤中铝的溶解动力学并与高岭石的结果进行比较，结果表明土壤铝的溶解速率比高岭石中的大得多，这主要因为土壤中交换态铝和无定形氧化铝的溶解速率较快，而粘土矿物中铝的溶解速率比较缓慢。红壤中硅、铝释放量的比较证明了这一假设，反应41．5h，硅的释放量仅为铝的8％。48h内铝的溶解动力学曲线可分为3个阶段：0-30min的快反应阶段，主要是土壤交换态铝和结晶不良的氧化铝的溶解；30-120min的较快反应阶段，主要是铝氧化物的溶解；120min后的慢反应阶段，主要是氧化铝和粘土矿物中铝的溶解。     

An Environmental Application of Regional Geochemical Mapping in Understanding Enzootic Geophagia of Calves in the Reivilo Area, South Africa

A specific enzootic form of geophagia (the deliberate ingestion of soil) occurs in young cattle and sheep in restricted areas of the Barkley-West, Postmasburg and Vryburg Districts of the Northern Cape- and North West Provinces of the Republic of South Africa. It results in severe, subacute to chronic hepatitis and jaundice, with a high mortality rate in untreated cases. An association between the disease and high concentrations of manganese in soils was shown since all the affected farms are situated on outcrops of the Reivilo Formation of the Campbell Rand Subgroup, which consists mainly of manganiferous dolomite. Furthermore high concentrations of manganese were found in the analysis of liver specimens from affected calves and the characteristic microscopic pathological changes in the liver could be induced experimentally in a calf and lamb by oral administration of manganese sulphate. The highest incidence of geophagia occurs at 7 to 14 days, whereas calves older than about 2 months are rarely affected. The symptoms usually start with intermittent, progressive geophagia, followed by constipation, dehydration and death within ca. 7–10 days in untreated cases. Young calves and lambs display an insatiable appetite for soil and sometimes lick iron poles. The treatment of calves by the parenteral injection of commercial iron-dextran- and vitamin B₁₂ preparations at 1 to 2 days after birth, and at 14 days of age, at the registered therapeutic doses, appeared to have a marked preventative effect on the occurrence of geophagia and its complications. Regional geochemical maps show a northeast–southwest trending anomaly in MnO, Zn and Pb, visually correlating with the distribution of the affected farms. Anomalously high distributions of Pb and Zn are also spatially related to the Pering (Pb,Zn) Mine. In this study, two farms were selected for comparative purposes. Gam, a farm situated on the Reivilo Formation of the Campbellrand Subgroup was chosen where a high incidence of geophagia occurred, as well as the farm Holpan on the Lyttelton Formation of the Malmani Subgroup where the problem was not known to be present. The farm Holpan was chosen as a control area, and is situated close to an old manganese mine on dolomite with a high MnO content. Geographically, Holpan is situated in an area with a high rainfall, with leaching and the formation of deep red soils on the dolomite, together with a hilly relief and low soil pH_{H 2 O}. Gam is situated in an area with lower rainfall, where precipitation would be less than evapotranspiration. The dolomite of the Malmani Subgroup and the Reivilo Formation are significantly different in their soil geochemistry. The MnO, Fe₂O₃ ^T and Co contents are significantly higher in the soils of the Malmani Subgroup than in the Reivilo Formation. The MnO, Zn and Pb contents on Gam are higher than on Holpan, whereas the Fe₂O₃ ^T and Co contents are lower. Soil on Holpan contains iron-minerals such as haematite, while no iron minerals were detected in the soils of Gam. The concretions, found in the soils on both farms, differs remarkably in iron-contents. Concretions on both farms have similar high concentrations of MnO, whereas the FeO content are low for the concretions on Gam and high for Holpan. Preliminary comparative analytical results of the colostrum, sampled from cows with new born calves within three days of birth, do not entirely reflect the soil geochemistry of the different farms. Whereas the soils on Gam have higher MnO, Zn and Pb, and lower Fe₂O₃ ^T and Co than Holpan, the colostrum produced on Gam has lower Mn, Fe and Co than on Holpan. The Pb and Zn concentrations in the colostrum on both farms do not differ significantly. The comparative regional geochemical soil data, together with the colostrum data, suggest that young calves on the farm Gam probably suffer from Fe and Co deficiency. Conversely, it was illustrated that the Fe and Co content in the soils are high and the Fe is abundant in the concretions on the farm Holpan. These findings, together with the apparent absence of geophagia at Holpan, as well as the observed effect of iron and cobalt supplementation in the prevention of geophagia on the farm Gam, suggests an association of geophagia with iron and cobalt deficiencies on the farm Gam.     

酸化对茶园黄棕壤CEC和粘土矿物组成的影响

用采自江苏溧阳种茶13 a和34 a的茶园黄棕壤表土和种茶54 a的茶园土壤剖面研究了酸化对土壤黏土矿物组成和阳离子交换量（CEC）的影响。结果表明：种茶13 a和34 a,表层土壤发生明显酸化,但土壤2∶1型黏土矿物的质量分数和CEC均与荒地土壤相似,说明酸化没有对黏土矿物转化和CEC产生明显影响。但种茶54 a后土壤发生进一步酸化,表层和表下层土壤pH降至3.79和3.70。土壤2∶1型黏土矿物质量分数随采用深度的增加而增加,高岭石质量分数呈相反的变化趋势。说明表层和表下层土壤的严重酸化加速土壤2∶1型黏土矿物向1∶1型高岭石的转化,这导致表层和表下层土壤CEC显著减小。     

Effect of humic acids on the Fenton degradation of phenol

We show that the degradation of phenol by Fe(III) and hydrogen peroxide is faster in the presence of humic acids. This is most likely due to faster reduction of Fe(III)-humate complexes by H₂O₂/HO₂^·/O₂^–· when compared with Fe(III)-H₂O complexes. The fact that humic acids, a major class of naturally occurring compounds, favour the Fenton reaction has great relevance in the field of water and soil decontamination, where organic compounds usually have a negative effect. Furthermore, it adds insight into the self-depuration processes of natural aquifers.     

Aluminium and fluoride concentrations of three tea varieties growing at Lantau Island,Hong Kong

The present project aims to investigate aluminium (Al) and fluoride (F) contents in teas (Camellia sinensis (L.) O. Kuntze). Three different commercial tea varieties: Assam variety and two China sub-varieties, a large leafed variety and small leafed variety, were collected in two tea gardens of Lantau Island tea plantation of Hong Kong. In general, high concentrations of Al and F were accumulated in the mature leaves (15.3 and of 2.07 g kg^–1 respectively). Among the three varieties, the small leafed variety exhibited the highest Al and F contents followed by the large leafed variety whereas the Assam variety had the lowest Al and F concentrations in its tea bushes. Tea products from a plantation were also analysed and it was noted that black tea had higher Al and F concentrations than green tea. The amount of Al and F released into tea liquor was also tested and the results showed that higher concentrations of Al and F were released into tea liquor under repeated infusion method than continuous infusion method.     

Ferrate(VI) oxidation of ibuprofen: A kinetic study

The kinetics of ferrate(VI) (Fe^VIO₄ ²⁻, Fe(VI)) oxidation of an antiphlogistic drug, ibuprofen (IBP), as a function of pH (7.75–9.10) and temperature (25–45°C) were investigated to see the applicability of Fe(VI) in removing this drug from water. The rates decrease with an increase in pH and the rates are related to protonation of ferrate(VI). The rates increase with an increase in temperature. The E _a of the reaction at pH 9.10 was calculated as 65.4±6.4 kJ mol⁻¹. The rate constant of the HFeO₄ ⁻ with ibuprofen is lower than with the sulphur drug, sulfamethoxazole. The use of Fe(VI) to remove ibuprofen is briefly discussed.     

Geochemical Characteristics of the Acid Mine Drainage in the Water System in the Vicinity of the Dogye Coal Mine in Korea

This study investigated geochemical characteristics of the acid mine drainage (AMD) discharged from the abandoned mine adits in the vicinity of the Dogye coal mine in Korea. Acid mine drainage discharged from Jeoncha pit adit of the Dogye coal mine, which is the main source of the AMD in the study area, had a pH value of 3.0 and concentrations of 2148mg SO₄ ^2– L^–1, 229mg Fe L^–1, 71mg A1 L^–1 and 11mg Mn L^–1. The reduction of some metal concentrations downstream from the discharge point could be explained on the basis of dilution and precipitation. The order of removal of metal ions downstream from the discharge point was Fe>A1, Cu>Zn, Mn. Acidity could be used as a good determining factor offering comprehensive and quantitative values for the polluting extent of acid mine drainage. The acidities existing in all acidic water samples in the Gunahan district originated primarily from mineral acidity, especially in the upper Nahan Creek from dissolved Fe and Al and in the middle and down Nahan Creek from dissolved Al. From the application of the WATEQ4F program, it was determined that predominant species of dissolved Fe in all water samples was Fe²⁺, and those of dissolved Al were AlSO₄ ⁺ and Al³⁺ except for IW2 sample which was associated with white precipitates. The species of dissolved Al in IW2 sample include also AlOH²⁺ and Al(OH)₂ ⁺. The saturation indices of goethite and haematite were positive in the water samples associated with ochrous precipitates (usually called Yellow Boy), therefore these solids might be precipitated. For the IW2 sample, the saturation indices of amorphous Al(OH)₃ and gibbsite were positive, so theoretically these solids might also be precipitated. By XRD analysis, it was found that goethite occurs in ochrous precipitates, and gibbsite in white precipitates.     

Modeling and coupling of soil respiration and soil water content in fenced Leymus chinensis steppe,Inner Mongolia

Soil respiration was measured with the enclosed chamber method during 2 years in fenced Leymus chinensis steppe, Inner Mongolia, China. Soil water content at 0–10 cm depth was a major limited factor of soil respiration in semi-arid grassland, accounting for 76.4% of the variation. The temperature-dependent exponential function could only explain 38.7% of the variation in soil respiration. With 246 data over the entire experimental period, multiple linear stepwise regressions of soil respiration rate were analyzed with the influencing factors, including soil water content at 0–10 cm depth, air temperature, air pressure, air humidity, total radiation and their interactions. With soil water content at 0–10 cm depth (W) and air temperature (T_h) as combined factors, the twice linear regression (F = 1.68WT_h − 109.09) was simple and its coefficients were significant, accounting for 83.1% of the variation in soil respiration. Due to the lack of long-term and continuous soil water content, a water sub-model based on precipitation and evapotranspiration was introduced, which could provide better fits with the measured values (R² = 0.813). The magnitudes of soil respiration calculated from the twice linear regression equation and water sub-model were 439.58 and 463.06 g CO₂ m⁻² in 2001 (19 June–23 September) and in 2002 (1 June–24 September), respectively. The mean hourly soil respiration rates were in the range of the previous studies in the adjacent region and the world's major temperate grasslands.     

Metal distribution in urban soil around steel industry beside Queen Alia Airport,Jordan

The objective of this study was to assess the extent and severity of metal contamination in urban soil around Queen Alia Airport, Jordan. Thirty-two soil samples were collected around steel manufacturing plants located in the Al-Jiza area, south Jordan, around the Queen Alia Airport. The samples were obtained at two depths, 0–10 and 10–20 cm, and were analyzed by atomic absorption spectrophotometry for lead (Pb), zinc (Zn), cadmium (Cd), iron (Fe), copper (Cu) and chromium (Cr) levels. The physicochemical factors believed to affect the mobility of metals in the soil of the study area were also examined, including pH, electrical conductivity, total organic matter, calcium carbonate (CaCO₃) content and cation exchange capacity. The high concentrations of Pb, Zn and Cd in the soil samples were found to be related to anthropogenic sources, such as the steel manufacturing plants, agriculture and traffic emissions, with the highest concentrations of these metals close to the site of the steel plants; in contrast the concentration of Cr was low in the soil sampled close to the steel plants. The metals were concentrated in the surface soil, and concentrations decreased with increasing depth, reflecting the physical properties of the soil and its alkaline pH. The mineralogical composition of the topsoil, identified by X-ray diffraction, was predominantly quartz, calcite, dolomite and minor minerals, such as gypsum and clay minerals. Metal concentrations were compared using one-way analysis of variance (ANOVA) to compute the statistical significance of the mean. The results of the ANOVA showed significant differences between sites for Pb, Cd and Cu, but no significant differences for the remaining metals tested. Factor analysis revealed that polluted soil occurs predominantly at sites around the steel plants and that there is no significant variation in the characteristics of the unpolluted soil, which are uniform in the study area.     

Correlation analysis as a tool to investigate the bioaccessibility of nickel, vanadium and zinc in Northern Ireland soils

Correlation analyses were conducted on nickel (Ni), vanadium (V) and zinc (Zn) oral bioaccessible fractions (BAFs) and selected geochemistry parameters to identify specific controls exerted over trace element bioaccessibility. BAFs were determined by previous research using the unified BARGE method. Total trace element concentrations and soil geochemical parameters were analysed as part of the Geological Survey of Northern Ireland Tellus Project. Correlation analysis included Ni, V and Zn BAFs against their total concentrations, pH, estimated soil organic carbon (SOC) and a further eight element oxides. BAF data were divided into three separate generic bedrock classifications of basalt, lithic arenite and mudstone prior to analysis, resulting in an increase in average correlation coefficients between BAFs and geochemical parameters. Sulphur trioxide and SOC, spatially correlated with upland peat soils, exhibited significant positive correlations with all BAFs in gastric and gastro-intestinal digestion phases, with such effects being strongest in the lithic arenite bedrock group. Significant negative relationships with bioaccessible Ni, V and Zn and their associated total concentrations were observed for the basalt group. Major element oxides were associated with reduced oral trace element bioaccessibility, with Al₂O₃ resulting in the highest number of significant negative correlations followed by Fe₂O₃. spatial mapping showed that metal oxides were present at reduced levels in peat soils. The findings illustrate how specific geology and soil geochemistry exert controls over trace element bioaccessibility, with soil chemical factors having a stronger influence on BAF results than relative geogenic abundance. In general, higher Ni, V and Zn bioaccessibility is expected in peat soil types.