Nitrogen and sulfur fertilizers promote the absorption of lead and cadmium with Salix integra Thunb. by increasing the bioavailability of heavy metals and regulating rhizosphere microbes

Utilizing NPKS fertilizer for the enhancement of Pennisetum purpureum growth and phytoremediation of arsenic in treatment wetland

Phytoremediation of arsenic in constructed wetlands (CWs) is becoming the most efficient, eco-friendly, and sustainable technology worldwide. This research aimed to explore the impact of utilizing NPKS fertilizer on the enrichment of Pennisetum purpureum growth and phytoremediation of arsenic in CWs. The study comprised control and 2 phytoremediation treatments with P. purpureum plants: 39 mg kg-1 As alone and the application of 0.04% NPKS fertilizer with 39 mg kg-1 As. This experiment was carried out in CWs for 42 days. Bioavailable and total As were determined by ICP-OES. P. purpureum developed effectively in the phytoremediation treatment with 0.04% NPKS fertilizer application till the end of the experiment. The arsenic phytoremediation treatment with 0.04% NPKS fertilizer removed 72.54% bioavailable arsenic, 72.52% total arsenic, and 0.05% arsenic in the leachate of CWs. The fresh weight of P. purpureum rose considerably when treated with 0.04% NPKS fertilizer in comparison to the arsenic-alone treatment. The maximum efficiency of arsenic absorption at 42 days attained 5041.7 ± 120.4 mg kg-1 DW in the phytoremediation treatment with 0.04% NPKS fertilizer application. These results suggest that phytoremediation treatments with 0.04% NPKS fertilizer can be used in As phytoremediation in anthropogenically polluted environments due to its high capability to uptake As.

Effect of long-term application of pig slurry and NPK fertilizers on trace metal content in the soil

One of the goals of sustainable agricultural production is to avoid soil contamination by elements defined as trace metals (TMs). The aim of this study was to assess the long-term impact of the use of pig slurry (PS) and NPK mineral fertilizers on the soil content of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn). In a 9-year crop rotation, PS was used three times only before root crops. The same four levels of NPK doses (N0P0K0, N1P1K1, N3P2K2, N4P2K2) were applied to both plots with and without PS. Soil samples were collected in early spring from topsoil (0-0.3 m) and subsoil (0.3-0.6 m). Three forms of TMs were determined in the soil: pseudo-total (Aqua regia); bioavailable (Mehlich 3 method) and readily bioavailable (mobile) forms (1 M NH4NO3). The tested factors did not have a significant impact on the Cd, Cu and Pb content, regardless of the form analyzed and the soil depth. PS application significantly increased the content of bioavailable forms of Zn regardless of the year, and the content of pseudo-total Zn only in the sugar beet year, i.e. after manure application. Increasing NPK doses increased the content of mobile Zn in the topsoil, especially in PS plots. A tendency to accumulate mobile forms of Cd and Pb was also observed on NPK-fertilized plots. Thus, long-term application of high NPK doses may increase the risk of contamination of the food chain with these metals. The content of mobile Cd and Zn was positively related to the content of total nitrogen in the soil and negatively related to pH.

Serendipita indica Drives Sulfur-Related Microbiota in Enhancing Growth of Hyperaccumulator Sedum alfredii and Facilitating Soil Cadmium Remediation

Endophytic fungus Serendipita indica can bolster plant growth and confer protection against various biotic and abiotic stresses. However, S. indica-reshaped rhizosphere microecology interactions and root-soil interface processes in situ at the submicrometer scale remain poorly understood. We combined amplicon sequencing and high-resolution nano X-ray fluorescence (nano-XRF) imaging of the root-soil interface to reveal cadmium (Cd) rhizosphere processes. S. indica can successfully colonize the roots of Sedum alfredii Hance, which induces a remarkable increase in shoot biomass by 211.32% and Cd accumulation by 235.72%. Nano-XRF images showed that S. indica colonization altered the Cd distribution in the rhizosphere and facilitated the proximity of more Cd and sulfur (S) to enter the roots and transport to the shoot. Furthermore, the rhizosphere-enriched microbiota demonstrated a more stable network structure after the S. indica inoculation. Keystone species were strongly associated with growth promotion and Cd absorption. For example, Comamonadaceae are closely related to the organic acid cycle and S bioavailability, which could facilitate Cd and S accumulation in plants. Meanwhile, Sphingomonadaceae could release auxin and boost plant biomass. In summary, we construct a mutualism system for beneficial fungi and hyperaccumulation plants, which facilitates high-efficient remediation of Cd-contaminated soils by restructuring the rhizosphere microbiota.

Selenium and Bacillus proteolyticus SES increased Cu-Cd-Cr uptake by ryegrass: highlighting the significance of key taxa and soil enzyme activity

Many studies have focused their attention on strategies to improve soil phytoremediation efficiency. In this study, a pot experiment was carried out to investigate whether Se and Bacillus proteolyticus SES promote Cu-Cd-Cr uptake by ryegrass. To explore the effect mechanism of Se and Bacillus proteolyticus SES, rhizosphere soil physiochemical properties and rhizosphere soil bacterial properties were determined further. The findings showed that Se and Bacillus proteolyticus SES reduced 23.04% Cu, 36.85% Cd, and 9.85% Cr from the rhizosphere soil of ryegrass. Further analysis revealed that soil pH, organic matter, soil enzyme activities, and soil microbial properties were changed with Se and Bacillus proteolyticus SES application. Notably, rhizosphere key taxa (Bacteroidetes, Actinobacteria, Firmicutes, Patescibacteria, Verrucomicrobia, Chloroflexi, etc.) were significantly enriched in rhizosphere soil of ryegrass, and those taxa abundance were positively correlated with soil heavy metal contents (P < 0.01). Our study also demonstrated that in terms of explaining variations of soil Cu-Cd-Cr content under Se and Bacillus proteolyticus SES treatment, soil enzyme activities (catalase and acid phosphatase) and soil microbe properties showed 42.5% and 12.2% contributions value, respectively. Overall, our study provided solid evidence again that Se and Bacillus proteolyticus SES facilitated phytoextraction of soil Cu-Cd-Cr, and elucidated the effect of soil key microorganism and chemical factor.