Risk assessment and strontium isotopic tracing of potentially toxic metals in creek sediments around a uranium mine, China.

The contamination of creek sediments near industrially nuclear dominated site presents significant environmental challenges, particularly in identifying and quantifying potentially toxic metal (loid)s (PTMs). This study aims to measure the extent of contamination and apportion related sources for nine PTMs in alpine creek sediments near a typical uranium tailing dam from China, including strontium (Sr), rubidium (Rb), manganese (Mn), lithium (Li), nickel (Ni), copper (Cu), vanadium (V), cadmium (Cd), zinc (Zn), using multivariate statistical approach and Sr isotopic compositions. The results show varying degrees of contamination in the sediments for some PTMs, i.e., Sr (16.1-39.6 mg/kg), Rb (171-675 mg/kg), Mn (224-2520 mg/kg), Li (11.6-78.8 mg/kg), Cd (0.31-1.38 mg/kg), and Zn (37.1-176 mg/kg). Multivariate statistical analyses indicate that Sr, Rb, Li, and Mn originated from the uranium tailing dam, while Cd and Zn were associated with abandoned agricultural activities, and Ni, Cu, and V were primarily linked to natural bedrock weathering. The Sr isotope fingerprint technique further suggests that 48.22-73.84% of Sr and associated PTMs in the sediments potentially derived from the uranium tailing dam. The combined use of multivariate statistical analysis and Sr isotopic fingerprint technique in alpine creek sediments enables more reliable insights into PTMs-induced pollution scenarios. The findings also offer unique perspectives for understanding and managing aqueous environments impacted by nuclear activities.

Distribution and migration of uranium, chromium, and accompanying metal(loid)s in soil-plants system around a uranium hydrometallurgical area.

The extraction and utilization of uranium (U) ores have led to the release of significant amounts of potentially toxic metal(loid)s (PTMs) into the environment, constituting a grave threat to the ecosystem. However, research on the distribution and migration mechanism of U, chromium (Cr), and their accompanying PTMs in soil-plant system around U hydrometallurgical area remains insufficient and poorly understood. Herein, the distribution, migration, and risk level of PTMs were evaluated in soil and plant samples around U hydrometallurgical area, Northern Guangdong, China. The results demonstrated that the maximum content of U and Cr found in the analyzed soils were up to 84.2 and 238.9 mg/kg, respectively. These values far exceed the soil background values in China and other countries. The highest content of U (53.6 mg/kg) was detected in Colocasia antiquorum Schott, and the highest content of Cr (349.5 mg/kg) was observed in Pteridium aquilinum, both of which were enriched in their roots. The risk assessment of PTMs demonstrated that the study area suffered from severe pollution (PN > 3), especially from U, Cr, Th, and As, suggesting the non-negligible anthropogenic impacts. Hence, in light of the significant ecological hazard posed by the U hydrometallurgical area, it is imperative to implement appropriate restoration measures to ensure the human health and maintain the stability of the ecosystem.

A study on the effects of anion, cation, organic compounds, and pH on the release behaviors of As and Sb from sediments.

The trace element of As and Sb have resulted in serious threats to ecological sustainability and human health in the Xijiang River basin, China. The geoaccumulation index (Igeo) results showed the sediment of Xijiang River was heavily contaminated by Sb as well as moderately contaminated by As. The effect of inorganic anions on the released As and Sb from the sediment increases in the following sequence: Cl- < SO42- < CO32- < PO43-. The presence of PO43- and CO32- had the greater effect over As mobility from the sediment compared to Sb. The effect of Ca(II), Al(III), and Mg(II) on the released amount of Sb from the sediment is negligible. Meanwhile, in the case of As, Ca(II) and Mg(II) had small impacts, but the released amount of As increased slightly with an increase of Al(III) concentration. The stability of As and Sb in the sediment was found to be the best at pH 5. The effect of organic compounds (≤ 0.05 mol/L) on the dissolved As percentages from the sediment increased in the following sequence: ethylenediaminetetraacetate (EDTA) < oxalate < citrate, and the effect on Sb release was oxalate < EDTA < citrate at concentrations (≤ 0.025 mol/L). This study provides the basic theoretical basis to manage the mobilization of co-contamination of sediments with As and Sb under the influence of external perturbations.

A systematic study of the synthesis conditions of blue and green ultramarine pigments via the reclamation of the industrial zeolite wastes and agricultural rice husks.

Discarded industrial zeolite waste and agricultural rice husks have caused a waste of resources. To achieve resource reuse, we proposed an economical method for the preparation of ultramarine pigments via the reclamation of industrial zeolite waste (ZW) and agricultural rice husks (RHs) or previously bio-charred rice husks (BRHs). The optimal blue and green pigments were synthesized by solid state reaction of mixtures of BRH/ZW/Na2CO3/S with mass ratios of 1:2:1:1.5 and 2:2:7:3, respectively, and using a two-step calcination process with a first stage at 500 and a second stage at 800 °C. Furthermore, the blue and green pigments were also obtained using directly RH (instead of BRH) as raw material, but this time with RH/ZW/Na2CO3/S mass ratios of 1:2:2:3 and 1:2:7:3.5 and with first-stage and second-stage calcination temperatures of 400 and 800 °C. This was done to reduce additional chemical reactions (e.g., BRH derived from the pyrolysis of RH). The XRD, FT-IR, Raman, and SEM results suggest that the synthetic blue and green pigments have the sodalite structure containing S3- and S2- radicals. The synthetic green pigment using RH as raw material had the best acid resistance. Additionally, the synthesis of blue and green ultramarine pigments via the reclamation of the industrial zeolite wastes and agricultural rice husks can reduce the costs of the production process.

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study.

The biotic or abiotic reduction of nano-crystalline 2-line ferrihydrite (2-line FH) into more thermodynamically stable phases such as lepidocrocite-LP, goethite-GT, magnetite-MG, and hematite-HT plays an important role in the geochemical cycling of elements and nutrients in aqueous systems. In our study, we employed the use of in situ liquid cell (LC) and semi in situ analysis in an environmental TEM to gain further insights at the micro/nano-scale into the reaction mechanisms by which Fe(ii)(aq) catalyzes 2-line FH. We visually observed for the first time the following intermediate steps: (1) formation of round and wire-shaped precursor nano-particles arising only from Fe(ii)(aq), (2) two distinct dissolution mechanisms for 2 line-FH (i.e. reduction of size and density as well as breakage through smaller nano-particles), (3) lack of complete dissolution of 2-line FH (i.e. "induction-period"), (4) an amorphous phase growth ("reactive-FH/labile Fe(iii) phase") on 2 line-FH, (5) deposition of amorphous nano-particles on the surface of 2 line-FH and (6) assemblage of elongated crystalline lamellae to form tabular LP crystals. Furthermore, we observed phenomena consistent with the movement of adsorbate ions from solution onto the surface of a Fe(iii)-oxy/hydroxide crystal. Thus our work here reveals that the catalytic transformation of 2-line FH by Fe(ii)(aq) at the micro/nano scale doesn't simply occur via dissolution-reprecipitation or surface nucleation-solid state conversion mechanisms. Rather, as we demonstrate here, it is an intricate chemical process that goes through a series of intermediate steps not visible through conventional lab or synchrotron bulk techniques. However, such intermediate steps may affect the environmental fate, bioavailability, and transport of elements of such nano-particles in aqueous environments.

Correction to: Arsenic concentration, speciation, and risk assessment in sediments of the Xijiang River basin, China.

In the original paper, there was an error in the communication unit 1. The communication unit was "Liaoning Engineering Research Center for Treatment and Recycling of Industrially Discharged Heavy Metals, Shenyang University of Chemical Technology, Shenyang 110142, People's Republic of China".

Arsenic concentration, speciation, and risk assessment in sediments of the Xijiang River basin, China.

In order to acquire the spatial distribution, speciation, and risk assessment of arsenic (As), 18 sediment samples were collected in the middle and upper reaches (Nanpan River, Beipan River, Hongshui River, Diaojiang River, and Duliu River) of the Xijiang River basin, China. The chemical fractions of As in the collected sediments were mainly dominated by the residual fraction and the Fe (Mn, Al) oxide/oxyhydroxides fractions. The correlation analysis results showed that the chemical fraction of As in sediments had close correlations with Mn, good correlations with Fe and organic matter (OM), while weak correlations with Al and carbonate. In addition, it also showed that Diaojiang River basin was found to have an extremely high As pollution status and suffered from high ecological risk. Duliu River and Nanpan River had moderately polluted levels of As and showed a low ecological risk. The other sample sites of Xijiang River basin were uncontaminated of As. The assessment results from this study indicated that the different types of species present based on the chemical fractionation of As from the Xijiang River basin showed different risks. Graphical abstract.

Systematic study on the reduction efficiency of ascorbic acid and thiourea on selenate and selenite at high and trace concentrations.

Selenate (Se(VI)) and selenite (Se(IV)) are common soluble wastewater pollutants in natural and anthropogenic systems. We evaluated the reduction efficiency and removal of low (0.02 and 2 mg/L) and high (20 and 200 mg/L) Se(IV)(aq) and Se(VI)(aq) concentrations to elemental (Se0) via the use of ascorbic acid (AA), thiourea (TH), and a 50-50% mixture. The reduction efficiency of AA with Se(IV)(aq) to nano- and micro-crystalline Se0 was ≥ 95%, but ≤ 5% of Se(VI)(aq) was reduced to Se(IV)(aq) with no Se0. Thiourea was able to reduce ≤ 75% of Se(IV)(aq) to bulk Se0 at lower concentrations but was more effective (≥ 90%) at higher concentrations. Reduction of Se(VI)(aq)→Se (IV)(aq) with TH was ≤ 75% at trace concentrations which steadily declined as the concentrations increased, and the products formed were elemental sulfur (S0) and SnSe8-n phases. The reduction efficiency of Se(IV)(aq) to bulk Se0 upon the addition of AA+TH was ≤ 81% at low concentrations and ≥ 90% at higher concentrations. An inverse relation to what was observed with Se(IV)(aq) was found upon the addition of AA+TH with Se(VI)(aq). At low Se(VI)(aq) concentrations, AA+TH was able to reduce more effectively (≤ 61%) Se(VI)(aq)→Se(IV)(aq)→Se0, while at higher concentrations, it was ineffective (≤ 11%) and Se0, S0, and SnSe8-n formed. This work helps to guide the removal, reduction effectiveness, and products formed from AA, TH, and a 50-50% mixture on Se(IV)(aq) and Se(VI)(aq) to Se0 under acidic conditions and environmentally relevant concentrations possibly found in acidic natural waters, hydrometallurgical chloride processing operations, and acid mine drainage/acid rock drainage tailings. Graphical Abstract ᅟ.

One-step synthesis of zerovalent-iron-biochar composites to activate persulfate for phenol degradation.

A novel zerovalen-iron-biochar composite (nZVI/SBC) was synthesized by using FeCl3-laden sorghum straw biomass as the raw material via a facile one-step pyrolysis method without additional chemical reactions (e.g., by NaBH4 reduction or thermochemical reduction). The nZVI/SBC was successfully employed as an activator in phenol degradation by activated persulfate. XRD, SEM, N2 adsorption-desorption and atomic absorption spectrophotometry analysis showed that the nanosized Fe0 was the main component of the 4ZVI/SBC activator, which was a mesopore material with an optimal FeCl3·6H2O/biomass impregnation mass ratio of 2.7 g/g. The 4ZVI/SBC activator showed an efficient degradation of phenol (95.65% for 30 min at 25 °C) with a large specific surface area of 78.669 m2·g-1. The recovery of 4ZVI/SBC activator after the degradation reaction of phenol can be realized with the small amount of dissolved iron in the water. The 4ZVI/SBC activator facilitated the activation of persulfate to degrade phenol into non-toxic CO2 and H2O. The trend of Cl-, SO4 2- and NO3 - affected the removal efficiency of phenol by using the 4ZVI/SBC activator in the following order: NO3 - > SO4 2- > Cl-. The one-step synthesis of the nanosized zerovalent-iron-biochar composite was feasible and may be applied as an effective strategy for controlling organic waste (e.g. phenol) by waste biomass.