Changes in the heavy metal distributions in whole soil and aggregates affected by the application of alkaline materials and phytoremediation

Abstract

To explore the combined remedy effect of alkaline materials and plants on the distribution of heavy metals in whole soil and aggregates, a 3 year in situ experiment was carried out in a dual copper (Cu)/cadmium (Cd)-contaminated farmland in this study. Treatment was applied by the addition of soda residue (11.2 t ha À1 ), apatite (22.3 t ha À1 ), or lime (4.45 t ha À1 ), respectively, into the heavy metals-contaminated soil as a single application; Elsholtzia splendens was continually planted for 3 years in all the experimental plots. The total metals amounts and distributions of Cu and Cd in the whole soil and aggregates were then investigated. Our results showed that (1) although the total concentrations of Cu and Cd were slightly increased in the whole soil, their exchangeable concentrations were significantly reduced in both abovementioned treatments; (2) all the abovementioned 3 treatments significantly increased the stability of the dry and wet aggregates when compared with the control treatment; (3) similar to the whole soil, combined remediation groups slightly increased the concentrations of Cu and Cd in the aggregates, but decreased their available and exchangeable concentrations observably.Specifically, the highest concentrations of Cu and Cd were found in the aggregates sized <0.053 mm; however, mass loadings of Cu and Cd were observed in the 0.053-0.25 mm and 0.25-2 mm sized fractions, respectively; moreover, the treatments increased the mass loading of Cu and Cd in the aggregates sized >0.25 mm. In total, the combined remediation adopted in our study dramatically decreased the available concentrations of both Cu and Cd in the whole soil and aggregates. The distribution variations of Cu and Cd caused by passivator-plant combined remediation in the whole soil might be because more metal ions have been transformed into less mobile fractions, whereas the heavy metal distribution differences in the aggregates might be not only correlated with the size of the soil wet aggregates, but also possibly controlled by the soil organic carbon.

The Immobilization of Soil Cadmium by the Combined Amendment of Bacteria and Hydroxyapatite

“…The micro-nanometer HAP can increase the soil pH to reduce the availability of heavy metals 34 . This result is consistent with some reports 27,35,36 .…”

Effects of Different Particle Sizes of Hydroxyapatite on the Distribution and Migration of Trace Elements (Copper and Cadmium) in a Smelter-Impacted Soil

“…e total Cu content of soil did not significantly decrease after 3 years of remediation, while the concentration of total Cd in soil increased slightly. ese results seemed to deviate from the goal of soil remediation, which was to reduce the concentration of heavy metals in soil, and similar results have been reported in our previous study in this region [25].…”

Microplastics are a hotspot for antibiotic resistance genes: Progress and perspective

“…The interaction between soil and microplastics could form different aggregates. Soil aggregates play a key role in the horizontal and downward transport of pollutants (like ARGs, microplastics, heavy metals) in the agroecosystems via runoff (Astner et al, 2020;Rillig et al, 2017a;Xu et al, 2017) (Fig. 3).…”