Agriculture

  2010 APR 22 - (VerticalNews.com) -- "Emissions from primary and secondary lead (Pb) smelters are responsible for high concentrations of metallic contaminants (Pb, Cd and Zn) in soils. However, less attention has been paid to volatile metalloids, such as antimony (Sb), which accompanies Pb smelting activities," investigators in Prague, Czech Republic report.

  "This paper is focused on geochemistry of Sb in the forest and agricultural soils in the vicinity of the Pribram Pb smelter (Czech Republic), with emphasis on Sb distribution, chemical fractionation and comparison with the behaviour of another toxic metalloid, arsenic (As). Forest soils were enriched in Sb (4.86-2058 mg kg(-1), mean: 379 mg kg(-1), median: 155 mg kg(-1)) with the highest concentrations in the organic horizons. Arsenic was found in significantly lower concentrations in forest soils (9.16-447 mg kg(-1), mean: 127 mg kg(-1), median: 82.9 mg kg(-1)). High concentrations of metalloids in forest soils are related to higher interception of smelter emissions by tree canopies. The Sb/As concentrations ratios ranged between 4.6 and 16.4 in the organic soil horizons, which is in agreement with (i) higher Sb deposition between similar to 1890 and the 1970s as recorded by 210-Pb dated peat cores from the vicinity of the smelter and (ii) rare historical analytical data on processed concentrates and dust from the smelter flue-gas cleaning system. In contrast to organic horizons of forest soils, the concentrations of the two metalloids are rather similar in agricultural soils and in mineral horizons of the forest soils. Antimony concentrations in agricultural soils were in the range 3.12-131 mg kg(-1) (mean: 39.3 mg kg(-1), median: 23.8 mg kg(-1)), whereas As concentrations were in the range 4.33-154 mg kg(-1) (mean: 60.3 mg kg(-1), median: 42.5 mg kg(-1)). Factor analysis showed that Sb and As are statistically correlated to oxalate-extractable Fe, corresponding to amorphous or less crystalline Fe-oxides. The 5-step sequential extraction procedure (SEP), which was originally designed for As, and revised BCR SEP were applied to chemically fractionate Sb and As in the most polluted soil profiles. In forest soils, Sb was mostly bound in residual fraction with ''mobile'' concentrations in the range of 0.6-4% of the total Sb content. In contrast, As was significantly more mobile (1.2-22% of the total content in the ''mobile'' fractions) with dominant binding to Fe-oxides (up to 57% of total As content). In agricultural soils, Sb was again less ''mobile'' than As (1.4-5.9% and 0.34-12.1%, respectively of the total concentrations). Whereas Sb was mainly bound to the residual fraction and partly also in the reducible fraction (Fe-oxides), As was predominantly bound to Fe-oxides (up to 71% of the total As content). Good agreement was observed between the two SEP methods in determining the ''mobile'' concentrations of the metalloids (R-Sb(2) = 0.9918 and R-As(2) = 0.9104, p<0.001)," wrote V. Ettler and colleagues, Charles University ...read more

  2010 APR 8 - (VerticalNews.com) -- "Surfactants affect the water-related soil properties of water-repellent soils but may also affect those of wettable soils. The effect of five surfactants, belonging to three different types, at different concentrations on the hydrophobic behaviour of a nonrepellent agricultural calcareous soil is studied," scientists in Granada, Spain report.

  "Native soil was treated with anionic (Aerosol 22), cationic (TDTMA and HDTMA) and non-ionic surfactants (Triton X-100 and Tween 80) and vapour and liquid hydrophobic characteristics were evaluated. Anionic and non-ionic surfactants at any concentration increase water vapour adsorption but cationic ones reduce it when applied to soil above 50% soil cation exchange capacity. Absorption of liquid water is restricted for all soil treatments with proven changes in water penetration time and wetting contact angles. Surfactant interactions with the soil matrix are related with changes in organic carbon and cation exchange capacity of the soil," wrote J. Fernandezgalvez and colleagues ...read more

  2010 APR 8 - (VerticalNews.com) -- According to recent research published in the journal Geoderma, "Many empirical equations have been developed to predict the properties of saturation extracts, primarily electrical conductivity, from the properties of soil water extracts of I to 5 ratio. Soil water 1:5 extracts are more rapidly and reproducibly prepared than saturation extracts."

  "However, the electrical conductivity of saturation extracts (ECse) is the benchmark to assess soil salinity. Analysis of the information provided by the electrical conductivity of soil 1:5 extracts (EC1:5) is a prerequisite to guide equation development and to use EC1:5 for soil salinity assessment. A total of 135 soil samples were taken from 39 sites at up to four different depths per site, down to a maximum depth of 95 cm in an irrigated agricultural area in SE Spain. Soil 1:5 extracts obtained from each sample were analysed for twelve chemical properties: concentration of sodium, ammonium, potassium, magnesium, calcium, chloride, nitrite, nitrate, sulphate, alkalinity and electrical conductivity. A principal component analysis (PCA) was applied to the correlation matrix of the log-transformed data set. The equilibrium status of 1:5 extracts with regard to gypsum was assessed with the chemical speciation programme SALSOLCHEMIS. The soil gypsum content was determined by using an adaptation of the classical method of total dissolution of soil gypsum, adequate to determine low gypsum contents. i.e. lower than 2%. Three principal components, accounting for 82% of the variance in the correlation matrix, were retained after eigenvector extraction. The first component accounted for 53% of the variance and was interpreted as representing the extract salinity due to gypsum dissolution. The second component accounted for 16% of the variance and was interpreted as representing the component of the extract salinity due to salts more soluble than gypsum, such as sodium and chloride salts. The information about soil salinity is split in two components in the 1:5 extracts, which are not easily resolved, whereas only one salinity component was obtained in the saturation extracts. The EC1:5 is a reliable property to estimate ECse with a 95% confidence interval of +/- 1.2 dS m(-1), only when it is lower than 1 dS m(-1). When EC1:5 is higher than 2.4 dS m(-1) it could also be reliably used to estimate soil salinity only if the 1:5 extract is gypsum-saturated, which is highly probable when the soil gypsum content is higher than 1.5%, or when the saturation extract is not gypsum-saturated, situation which happens when soil gypsum content is lower than 0.2%. When the EC1:5 is between 1 and 2.4 dS m(-1), it provides poor information about the ECse, which could be between 4 and 14 dS m(-1) unless the soil gypsum content is negligible, i.e. lower than 0.2%. The usefulness of the EC1:5 to estimate soil salinity can be extended when it is used in conjunction with an estimate of soil gypsum content," wrote F. Visconti and colleagues ...read more