Evaluation of single extraction procedures for the assessment of heavy metal extractability in citrus agricultural soil of a typical Mediterranean environment (Argolida, Greece)

Abstract

Purpose Heavy metals are natural soil constituents; however, the intense use of agrochemicals can increase total contents above background levels as well as the available fractions of the more toxic elements. In this study, the occurrence of some metals was investigated in agricultural soils from an intensely farmed rural area of Greece (Argolida) aiming to evaluate the various available pools and examine their relationship with the reactive and pseudototal soil fraction. Materials and methods Thirty soil samples were selected from a large database of a previous geochemical survey in the study area. The pseudototal (aqua regia), reactive (0.43 M HNO 3 ), potentially phytoavailable (0.05 M EDTA), mobilizable (0.43 M HAc), and mobile (0.01 M CaCl 2 ) pools of Cu, Zn, Cd, and Mn were determined. Soil properties were also examined including pH, total organic carbon, calcium carbonate content, and amorphous Al, Mn, and Fe oxides. In order to combine all geochemical information and elucidate the association between available metal pools and soil chemical characteristics, multiple linear regression was employed. The various proportions of available metal pools (%) were expressed as a function of the pseudototal or reactive metal content and general soil properties. Results and discussionThe mobile pool of trace elements in the studied soils was quite low, while notable amounts of Cu were released by EDTA indicating a greater tendency for complexation. The acetic acid extraction yielded increased percentages of Cd and Mn and for these elements the reactive pools were quite representative of the pseudototal content. Extractable amounts of Zn by all the applied reagents were very low indicating that a considerable part of this metal is of geogenic origin. The empirical regression models showed that prediction of the available pools of Cu, Zn, and Cd from the pseudototal and reactive content is feasible. Although pH is known to be a key factor of at least exchangeable metal pools, its narrow range blurs its influence in the present study. Conclusions The relatively low extraction yields of the studied elements show that the potential hazard of metal transfer to plants in the area is minimal despite some elevated pseudototal concentrations. The geochemical reactive and various available pools of Cu, Zn, and Cd in Mediterranean calcareous citrus soils can be determined by a single soil extraction test using dilute nitric acid.

The contents of the potentially harmful elements in the arable soils of southern Poland, with the assessment of ecological and health risks: a case study

“…of the total concentration of those elements. Similarly, low solubility of trace elements was found in the studies of Li et al (2014) and Kelepertzis et al (2015), which highlighted the low extraction efficiency of the CaCl 2 extraction, especially in the pH range characterizing the soils under consideration. The results confirmed a higher mobility of Cd in comparison with that of other trace elements.…”

“…Agricultural soils are threatened by the PHE pollution due to rapidly expanding urban and industrial areas or the intensive use of fertilizers and agrochemicals for the crop protection purposes (Kelepertzis et al 2015;Klimek-Kopyra et al 2015;Š ukalić et al 2018). Recent research on agricultural soils revealed the accelerated accumulation of heavy metals and associated health risk, especially due to greenhouse agricultural cultivation (Wan et al 2019) and the usage of fertilizers and fungicides (Huang et al 2019).…”

Evaluation of historical atmospheric pollution in an industrial area by dendrochemical approaches

“…The soils of the area were slightly alkaline (pH = 7.66 ± 0.39, 7.48 ± 0.25 and 7.50 ± 0.23 respectively for rural, urban and industrial areas) responsible for a low mobility of most of the TEs, which did not exceed 5 % of the pseudototal concentration or were very low with values close to the percent or even the thousandth for As, Cr, Co, Mn, Mo, Ni, Sb and V. On the contrary, important exchangeable fractions were measured for Cd (between 21.6 and 23.5 %) and to a lesser extent for Cu, Pb and Zn, of which the DTPA-extractable fraction represented between 3 and 10 % of the pseudototal fraction. This can be explained by the strong affinity of Cu and Pb for dissolved organic matter (Komarek et al, 2008, Kelepertzis et al, 2015, Safari et al, 2015. Indeed, Wu et al (2002) found that a high pH favours the dissolution of humic acids and increases the dissolved concentration of metals due to the formation of metal-organic complexes in solution.…”

Copper Accumulation in Vineyard Soils From Nemea, Greece

“…Referring to the chemical methods used in the laboratory to determine the Cu content in vineyard soil, the aqua regia extraction is frequently applied, especially in the European studies, but with low correlation with the phytoavailability of this element. For that reason, a variety of single stage chemical extractions has been proposed for mimicking the processes that operate at the soil-plant interface providing more useful information for the fraction of Cu that is available for plant uptake (Kelepertzis et al, 2015).…”