Predicting chemical speciation of metals in soil using Visual Minteq

From soil contamination and risk assessment perspectives,it is imperative to understand the ecological processes occurring in soils.Certain soil processes greatly affect chemical speciation of potentially toxic metals(PTMs),and thus also influence their biogeochemical activity.The current study analyzed chemical speciation of eight PTMs(Cd,Cr,Fe,Cu,Mn,Ni,Zn,and Pb)in upper and lower soil layers for 15 agronomic fields of Vehari-Pakistan using Visual Minteq software.The divalent forms of most PTMs(PTM^(2+))generally predominated in both soil layers(79.9%overall occurrence).However,chromium revealed a different pattern of chemical speciation(95.8%as CrOH^(+))compared to other PTMs.The mean percentage of all the PTMs2+was slightly higher for the lower soil layer(81.3%)than in the upper layer(78.4%),the trend being same for all the PTMs,except Cr.This higher PTMs^(2+)percentage in lower soil layers than upper layers was due to lower content of organic matter and other anions such as Cl^(−)and HCO_(3)_(−).The mean percentage ages of all the PTMs^(2+)was similar among all the 15 agronomic fields,which was confirmed by strong Pearson correlation values(R^(2)>0.95).The PCA graph grouped all the agronomic fields and PTM^(2+) closely,except Cr^(2+) and Cu^(2+).This grouping confirmed the similar chemical speciation of PTMs,except Cu and Cr in studied fields.

Water extraction kinetics of metals, arsenic and dissolved organic carbon from industrial contaminated poplar leaves

In industrial areas, tree leaves contaminated by metals and metalloids could constitute a secondary source of pollutants. In the present study, water extraction kinetics of inorganic elements （IE： Pb, Zn, Cd, As, Fe and Mn）, dissolved organic carbon, pH and biological activity were studied for industrial contaminated poplar leaves. Moreover, the distribution of the IE through the size fractions of the associated top soil was measured. High quantities ofMn, Zn and As and polysaccharides were released in the solution from the strongly contaminated leaves. The kinetic of release varied with time and metal type. The solution pH decreased while dissolved organic contents increased with time after 30 days. Therefore, these contaminated leaves could constitute a source of more available organic metals and metalloids than the initial inorganic process particles. However, the distribution of the IE through the size fractions of the top soil suggested that a great part of the released IE was adsorbed, reducing in consequence their transfers and bioavailability. It＇s concluded that mobility/boioavailability and speciation of metals and metalloids released from the decomposition of polluted tree leaves depends on soil characteristics, pollutant type and litter composition, with consequences for environmental risk assessment.

Kinetic study of phytotoxicity induced by foliar lead uptake for vegetables exposed to fine particles and implications for sustainable urban agriculture

At the global scale, foliar metal transfer occurs for consumed vegetables cultivated in numerous urban or industrial areas with a polluted atmosphere. However, the kinetics of metal uptake, translocation and involved phytotoxicity was never jointly studied with vegetables exposed to micronic and sub-micronic particles（PM）. Different leafy vegetables（lettuces and cabbages） cultivated in RHIZOtest？ devices were, therefore, exposed in a greenhouse for 5, 10 and 15 days to various Pb O PM doses. The kinetics of transfer and phytotoxicity was assessed in relation to lead concentration and exposure duration. A significant Pb accumulation in leaves（up to 7392 mg/kg dry weight（DW） in lettuce） with translocation to roots was observed. Lead foliar exposure resulted in significant phytotoxicity, lipid composition change, a decrease of plant shoot growth（up to 68.2% in lettuce） and net photosynthesis（up to 58% in lettuce）. The phytotoxicity results indicated plant adaptation to Pb and a higher sensitivity of lettuce in comparison with cabbage. Air quality needs, therefore, to be considered for the health and quality of vegetables grown in polluted areas, such as certain megacities（in China, Pakistan, Europe, etc.） and furthermore, to assess the health risks associated with their consumption.