Search

Aims: Atmospheric trace metal deposition is an important source in agricultural soils and crops, but a large knowledge gap exists between foliar and root uptake of wet/dry deposition. We aim to distinguish the contribution of dry and wet-deposited trace metals to rice plant via foliar and root uptake and to investigate their accumulations during the full growth season. Methods: We performed an atmospheric exposure experiment using customized open top chambers (OTCs) to distinguish the impacts of wet and dry deposition contribution to foliar and root uptake and their mobility in soils. The foliar uptake and then translocation was hypothesized the major pathway of trace metal accumulation in rice grains. Results: Foliar uptake of wet- and dry-deposited Cu, Zn, and Pb played an important role in their accumulations in rice plant, contributing to 44–47%, 23–25%, and 35–37% in rice grains, respectively. The leaf Cu, Zn, and Pb accumulated from atmospheric deposition can be transported upward to rice grains but nodes seem to restrict them downward translocation. Rice leaves cannot directly take up atmospheric As and the deposited As can only accumulate in rice through the root uptake. The trace metals showed high mobility in atmospheric deposition, which significantly increase the bioavailable trace metal fractions in surface soils and soil solutions. Conclusions: This study provides a new insight of similar or even higher contributions of foliar uptake than root uptake of trace metals from atmospheric deposition and that reducing the accumulation of atmospheric trace metals due to deposition on leaves can effectively decrease the accumulation of trace metals in crops. [ABSTRACT FROM AUTHOR]

Phytoextraction is a promising technology for remediating heavy metal-contaminated soil. Continuously screening potential plants is important for enhancing the efficiency of remediation. In this study, fourteen local native plant species and four cultivated plant species, along with their paired soils, were collected from around a copper smelter. The characteristics of soil pollution were evaluated using contaminant factors (CF) and a geoaccumulation index (Igeo). The phytoextraction potential of plants was investigated using the translocation factor (TF) and bioconcentration factor (BCF). The soils around the smelter were very acidic, with a mean pH of 5.01. The CF for copper and cadmium were 8.67–32.3 and 5.45–44.2, and the Igeo values for copper and cadmium were 2.43–4.43 and −0.12–2.29, respectively, indicating that the level of soil contamination was moderate to severe. The copper concentrations in the root (357 mg/kg), shoot (219 mg/kg), and leaf (269 mg/kg) of Elsholtzia splendens Nakai were higher than that in the other species. The cadmium in the shoot (32.2 mg/kg) and leaf (18.5 mg/kg) of Sedum plumbizincicola was the highest, and Phytolacca acinosa Roxb. had the highest cadmium level (20 mg/kg) in the root. Soil total and CaCl2-extractable copper and cadmium were positively correlated with copper and cadmium in the plant roots, respectively. The results of TF and BCF for copper and cadmium suggested that the accumulation and translocation capacities for cadmium were higher than those of copper in the eighteen plant species. Although not all plants met the criteria of being hyperaccumulators, Sedum plumbizincicola, Mosla chinensis Maxim, and Elsholtzia splendens Nakai showed the most potential as candidates for the phytoextraction of copper and cadmium contaminated soils, as indicated by their TF and BCF values. [ABSTRACT FROM AUTHOR]

Fly ash (FA) is promising for environmental remediation, but how to modify the FA with high remediation efficiency through an environmentally friendly and low-cost modification method is scare. A modified FA (MFA) was prepared through a one-step hydrothermal modification with Ca(OH)2 and KH2PO4. Results indicated that irregular agglomerates occurred on the surface of the MFA and that the specific surface area increased by 1.94 times compared to that of FA. Compared to FA, glassy compositions in MFA were destroyed and amorphous Si/Al and alkaline aluminosilicate gels were formed. The soil application of 0.2–0.6% MFA significantly increased soil pH by 0.23–0.86 units compared to FA and decreased available lead (Pb) and copper (Cu) by 25–97.1% and 13.5–75%, respectively. MFA significantly decreased exchangeable Pb and Cu by 12.5–32% and 11.4–35.2%, respectively, compared to FA. This may be due to the high pH and specific surface area of MFA, which promoted to the formation of amorphous Si/Al, metal–phosphate precipitation, and complexation with functional groups. In addition, MFA slightly increased the biomass of shoots and roots and decreased the uptake of Pb and Cu by ryegrass. This study provides a new modification method for the utilization of FA in the heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

The atmospheric deposition of copper (Cu) and cadmium (Cd) was monitored in eight sites around a Cu smelter with similar distance to verify whether tree leaf and ring can be used as bio-indicators to track spatial pollution record. Results showed that total atmospheric deposition of Cu (103–1215 mg/m2/year) and Cd (3.57–11.2 mg/m2/year) were 4.73–66.6 and 3.15–12.2 times higher than those in background site (164 mg/m2/year and 0.93 mg/m2/year). The frequencies of wind directions significantly influenced the atmospheric deposition of Cu and Cd, and the highest atmospheric deposition of Cu and Cd were at the prevalent northeastern wind (JN), and low frequency south (WJ) and north (SW) winds for the lowest deposition fluxes. Since the bioavailability of Cd was higher than that of Cu, the atmospheric deposition of Cd was more easily adsorbed by tree leaf and ring, resulting in only significant relation between atmospheric Cd deposition and Cinnamomum camphora leaves and tree ring Cd. Although tree rings cannot correctly record the atmospheric Cu and Cd deposition, higher concentrations in the indigenous tree rings than the transplanted tree rings suggested that tree rings can reflect to some extent the variations of atmospheric deposition. Generally, spatial pollution of atmospheric deposition of heavy metals cannot reflect the distribution of soil total and available metals around the smelter, and only camphor leaf and tree ring can bio-indicate Cd deposition. A major implication of these findings is that leaf and tree ring can serve for biomonitoring purposes to assess the spatial distribution of atmospheric deposition metal with high bioavailability around a pollution source with similar distance. [ABSTRACT FROM AUTHOR]