Improving the relationship between soil characteristics and metal bioavailability by using reactive fractions of soil parameters in calcareous soils

Abstract

The contribution of the nature instead of the total content of soil parameters relevant to metal bioavailability in lettuce was tested using a series of low-polluted Mediterranean agricultural calcareous soils offering natural gradients in the content and composition of carbonate, organic, and oxide fractions. Two datasets were compared by canonical ordination based on redundancy analysis: total concentrations (TC dataset) of main soil parameters (constituents, phases, or elements) involved in metal retention and bioavailability; and chemically defined reactive fractions of these parameters (RF dataset). The metal bioavailability patterns were satisfactorily explained only when the RF dataset was used, and the results showed that the proportion of crystalline Fe oxides, dissolved organic C, diethylene-triamine-pentaacetic acid (DTPA)-extractable Cu and Zn, and a labile organic pool accounted for 76% of the variance. In addition, 2 multipollution scenarios by metal spiking were tested that showed better relationships with the RF dataset than with the TC dataset (up to 17% more) and new reactive fractions involved. For Mediterranean calcareous soils, the use of reactive pools of soil parameters rather than their total contents improved the relationships between soil constituents and metal bioavailability. Such pool determinations should be systematically included in studies dealing with bioavailability or risk assessment.

Aridity and reduced soil micronutrient availability in global drylands

“…For available metal concentrations, 12 mL of a solution containing 0.005 M DTPA, 0.01 M CaCl 2 and 0.1 M triethanolamine (TEA) at a pH of 7.30 was added to 6 g of soil; the mixture was shaken for 2 h at room temperature (20ºC), and the supernatant filtered through a 42 Whatmann filter prior to analysis by ICP-OES. We used the DTPA method as indicator of available pool of metals in soils because this technique is extensively used for these purposes in neutral to basic soils, as is the case of most of the soils studied69–71. The LD and LQ were 0.04 and 0.1 mg kg -1 for available Cu, 0.2 and 0.5 mg Fe kg -1 for available, 0.02 and 0.05 mg Mn kg -1 for available Mn, 0.04 and 0.1 mg kg -1 for available Zn.…”

Copper and zinc accumulation, fractionation and migration in vineyard soils from Santa Catarina State, Brazil

“…The highest Zn EDTA contents were observed up to the depth of 0.10m in the vineyard 2 soil (Figure 1e). Thehigher contents of Cu EPA and Zn EPA , and Cu EDTA and Zn EDTA , frequently used to assess the mobility of Cu and Zn in the soil profile and, in the case of EDTA, the availability of the element to the plants, may be explained by the frequent leaf applications of fungicides over the years for control of fungal leaf diseases (Mackie et al, 2012;Santiago-Martin et al 2015). In vineyard 1 (4-year-old), Zn EPA levels at the 0.10 to 0.40 m layers were higher than those observed in vineyard 2 (15-year-old).…”

Metallic micronutrients are associated with the structure and function of the soil microbiome

“…All the digestion solutions were filtered through filter papers and then adjusted to a volume of 50 mL with distilled water. Soil available micronutrients were extracted by an extractant containing 0.005 mol/L DTPA, 0.01 mol/L CaCl 2 , and 0.1 mol/L triethanolamine at a pH of 7.30 and the extraction solutions were filtered through a grade 42 Whatman filter paper 39 . This extraction has been commonly used for different soils during the last decades.…”