The entry of Cd into the food chain is of concern as it can cause chronic health problems. To investigate the relationship between soil properties and the concentration of Cd in wheat (Triticum aestivum L.) and harley (Hordeum vulgare L.) grain, we analyzed 162 wheat and 215 barley grain samples collected from paired soil and crop surveys in Britain, and wheat and barley samples from two long-term sewage sludge experiments. Cadmium concentrations were much lower in barley grain than in wheat grain under comparable soil conditions. Multiple regression analysis showed that soil total Cd and pH were the significant factors influencing grain Cd concentrations. Significant cultivar differences in Cd uptake were observed for both wheat and barley. Wheat grain Cd concentrations could be predicted reasonably well from soil total Cd and pH using the following model: log(grain Cd) = a + b log(soil Cd) - c(soil pH), with 53% of the variance being accounted for. The coefficients obtained from the data sets of the paired soil and crop surveys and from long-term sewage sludge experiments were similar, suggesting similar controlling factors of Cd bioavailability in sludge-amended or unamended soils. For barley, the model was less satisfactory for predicting grain Cd concentration (22% of variance accounted for). The model can be used to predict the likelihood of wheat grain Cd exceeding the new European Union (EU) foodstuff regulations on the maximum permissible concentration of Cd under different soil conditions, particularly in relation to the existing Directive and the proposed new Directive on land applications of sewage sludge.

The selenium concentration of representative bread-making wheat (Triticum aestivum L) samples was measured in national grain surveys collected in 1982 (n (number of samples) = 180), 1992 (n = 187) and 1998 (n = 85) from major wheat-growing regions around the UK. The means and distributions of selenium concentrations over the three years were similar, with mean grain concentrations of 0.025, 0.033 and 0.025 mg kg À1 dry weight respectively and inter-quartile ranges varying from 0.015 mg kg À1 in 1982 to 0.019 mg kg À1 in 1992 samples. No long-term changes in the distribution of wheat selenium concentrations were found over the 17 year period. Geographical mapping of the concentrations identified an area of eastern England as having high grain concentrations compared with other UK regions. There were no significant correlations between grain selenium and grain sulphur concentrations for the national survey samples. However, at an individual field experimental site, increasing the rate of sulphur addition was found to decrease grain selenium concentration significantly. The daily UK dietary contribution of selenium from wheat-based products was estimated and the daily intake was calculated to be 6.4 mg selenium, around one-tenth of the UK recommended intake values for men and women.

Equilibrium constants are reported for the aluminum(III) complexes with four ligands that contain the 1,2-dihydroxyaryl group: trans-3-(3′,4′-dihydroxyphenyl)propenoic acid (caffeic acid), 3-(3′,4′-dihydroxycinnamoyl)-1,3,4,5-tetrahydroxycyclohexanecarboxylic acid (chlorogenic acid), 3,4-dihydroxybenzylamine (DHB), and 1,2-dihydroxyanthraquinone-3-sulfonic acid (DASA). The protonation and complexation reactions were studied by potentiometric and spectrophotometric titrations in aqueous solution at 25 °C (I ) 0.10 M KCl). The complexation reactions were studied for ligand/metal ratios in the range from 1.3 to 5.9. For caffeic and chlorogenic acids (H 3 L), the experimental data were consistent with the formation of six mononuclear Al-ligand species, each involving catecholate coordination: AlHL + , AlL, Al(OH)L -, AlL 2 3-, Al(OH)L 2 4-, and AlL 3 6-. For DHB (H 2 L), the data were consistent with the formation of six monomeric and one dimeric Al species: AlHL 2+ , Al(HL) 2 + , Al(HL) 3 0 , Al(HL) 2 L -, Al(HL)L 2 2-, AlL 3 3-, and (OH) 2 Al 2 (HL) 2 2+ , in which HL has a protonated amino group. On the basis of the DASA (H 2 L -) titration data, three monomeric and one dimeric Al-ligand species were proposed: AlL 0 , AlL 2 3-, Al(OH)L 2 4-, and Al 2 (OH) 2 L 4 8-. The relative stability of the 1:1 complexes, AlL, was DASA > chlorogenic acid > caffeic acid > DHB. This indicates the progressive electron-withdrawing effects of the ring substituents -SO 3 -< -CHdCH‚CO‚O‚(C 6 H 10 O 3 )‚COOH < -CHdCH‚COOH < -NH 3 + .

Grain Cd concentrations were determined in the wheat (Triticum aestivum L.) cultivars Soissons, Brigadier, and Hereward grown in 1994,1996, and 1999, respectively, in soils of a long-term field experiment to which sewage sludges contaminated with Zn, Cu, Ni, or Cr had previously been added. Soil pore water soluble Cd and free Cd2+ increased linearly with increasing total soil Cd (R2=0.82 and 0.84, respectively; P<0.001). Similarly, soil pore water free Cd2+ increased linearly with increasing soil pore water soluble Cd (R2=0.98; P<0.001). There was no evidence of a plateau in soil pore water Cd concentrations with increasing soil Cd concentrations. Grain Cd concentrations were significantly correlated with total soil Cd (P<0.001), soil pore water Cd (P<0.001), and free Cd2+ (P<0.001). A slight curvilinear relationship between grain Cd and soil Cd was apparent, but there was no plateau, even at the maximum soil Cd concentration of about 2.7 mg kg(-1). The relationship between soil pore water Cd and grain Cd was linear for all three cultivars. The slopes were in the order 1994 > 1996 > 1999, with more Cd being taken up into the grain by Soissons grown in 1994, and least by Hereward grown in 1999. For Soissons, Cd concentration in the grain greater than the EU limit (0.24 mg kg(-1) dry wt.) occurred at soil Cd less than the current UK limit of 3 mg kg(-1) for soils receiving sewage sludge. In contrast, for Brigadier and Hereward, grain Cd concentrations were near to and less than the EU limit, respectively, at soil Cd concentrations of 3 mg kg(-1).

No abstract

The impact of land use change from grassland to conifer forest on the aluminium (Al) concentrations in soils and soil solutions was examined. Soils from grassland were compared with those from adjoining 15–19-year old forest stands at 3 contrasting pairs of sites in South Island, New Zealand. The site pairs were on a terrace [Pinus nigra/P. ponderosa, and grassland (CP)], and a hill slope [Pseudotsuga menziesii and grassland (CF)] in the Craigieburn range, Canterbury, and a hill slope in the Lammerlaw Range, Otago [P. radiata and grassland (LP)]. The sites had never been cultivated or fertilised, and for each pair the forest and grassland were similar in terms of soil and topography. The 1 M KCl exchangeable and 0.02 M CaCl 2 extractable Al levels at 0–10 cm were higher in forest than in grassland topsoil at CP and LP (P < 0.01). In soil solutions there was a trend for both ‘reactive Al’ and Al bound in labile organic complexes to be higher in forest soil at all sites, but site-pair differences were only significant at LP, and only for ‘reactive Al’. The increase in ‘reactive Al’ at this site was linked to the low pH and low base saturation. The ratios of exchangeable and soil solution Ca 2+ and Mg 2+ to ‘reactive Al’ were substantially lower in forest than grassland soils at all sites. Aluminium complexation capacity (Al-CC) values at all sites were higher in forest soil solutions than in grassland soil solutions. For the grassland and forest sites at LP, the Al-CC correlated strongly with the amount of soluble fulvic and humic matter present, as estimated from soil solution UV absorbance at 250 nm. In soils with the lowest percentage base saturation and buffering capacity (LP), afforestation of pastoral grassland with Pinus radiata significantly reduced soil pH and base cation levels, while increasing both soil and soil solution Al concentrations. Under such conditions (base saturation <20%), the increase in ‘reactive Al’ concentrations in soil solutions under fast growing conifer tree species may be sufficient to affect Mg uptake.

Concentrations of Al3+ were calculated in soil solutions from concentrations of the monomeric ‘reactive Al’ species ([Al3+] + [Al(OH)2+] + [Al(OH)2+] + [AlF2+]) obtained using a recently reported flow injection analysis (FIA) chelating resin technique. Soil solution samples came from 7 sites encompassing a range of New Zealand soils (Brown, Gley, Pallic, Podzol, and Recent Soils) and vegetation types (pasture, shrub lands, and indigenous and exotic forest). Previously published data from a further 7 sites, obtained using a rapid (7 s) FIA technique, were transformed to give compatible results. The resultant data (n = 85) covered the pH range 2.7–7.6, and showed a single curvilinear relationship for log [Al3+] v. soil solution pH, regardless of vegetation or soil type. At pH >5.6, the data had a slope of –2.98 and fell between the amorphous Al(OH)3 and gibbsite solubility lines. At pH <5.0, the data had a slope of –0.46; further, the soil solutions were under-saturated with respect to both minerals. These results are interpreted as indicating control of Al solubility by Al(OH)3 (s) (at pH >5.6) and soil organic matter (at pH <5.0), respectively. This interpretation is supported by data from a pH-dependent Al–fulvic acid binding curve, for which calculated values of [Al3+] follow the same curvilinear relationship determined from the soil solution samples.

Strategic laboratory planning in limited resource areas is essential for addressing global health security issues. Establishing a national reference laboratory, especially one with BSL-3 or -4 biocontainment facilities, requires a heavy investment of resources, a multisectoral approach, and commitments from multiple stakeholders. We make the case for donor organizations and recipient partners to develop a comprehensive laboratory operations roadmap that addresses factors such as mission and roles, engaging national and political support, securing financial support, defining stakeholder involvement, fostering partnerships, and building trust. Successful development occurred with projects in African countries and in Azerbaijan, where strong leadership and a clear management framework have been key to success. A clearly identified and agreed management framework facilitate identifying the responsibility for developing laboratory capabilities and support services, including biosafety and biosecurity, quality assurance, equipment maintenance, supply chain establishment, staff certification and training, retention of human resources, and sustainable operating revenue. These capabilities and support services pose rate-limiting yet necessary challenges. Laboratory capabilities depend on mission and role, as determined by all stakeholders, and demonstrate the need for relevant metrics to monitor the success of the laboratory, including support for internal and external audits. Our analysis concludes that alternative frameworks for success exist for developing and implementing capabilities at regional and national levels in limited resource areas. Thus, achieving a balance for standardizing practices between local procedures and accepted international standards is a prerequisite for integrating new facilities into a country's existing public health infrastructure and into the overall international scientific community.