Distribution and Fractionation of Uranium in Weapon Tested Range Soils

Proteomics analysis of resistance mechanism of Trichoderma harzianum under U(VI) stress

Trichoderma harzianum has a certain resistance to Hexavalent Uranium (U(VI)), but its resistance mechanism is unknown. Based on proteomics sequencing using DIA mode, differentially expressed proteins (DEPs) of Trichoderma harzianum under U(VI) stress were identified. GO enrichment, KEGG annotation analysis and DEPs annotation were performed. The results showed that 8 DEPs, 8 DEPs and 15 DEPs were obtained in the low-dose, medium-dose and high-dose groups, respectively. The functional classification of GO demonstrated that DEPs were associated with 17 molecular functions, 5 biological processes, and 5 cellular components. Furthermore, DEPs were enriched in transport and catabolism, energy metabolism, translation, and signal transduction. These findings showed that Trichoderma harzianum was significantly changed in protein expression and signaling pathway after U(VI) exposure. Therefore, these results have provided Trichoderma harzianum with a theoretical background that can be applied to environmental cleanup.

U(VI) exposure induces apoptosis and pyroptosis in RAW264.7 cells

U(VI) pollution has already led to serious harm to the environment and human health with the increase of human activities. The viability of RAW264.7 cells was assessed under various U(VI) concentration stress for 24 and 48 h. The reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and superoxide dismutase (SOD) activities of RAW264.7 cells under U(VI) stress were measured. The results showed that U(VI) decreased cell activity, induced intracellular ROS production, abnormal MMP, and increased SOD activity. The flow cytometry with Annexin-V/PI double labeling demonstrated that the rate of late apoptosis increased with the increase of U(VI) concentration, resulting in decreased Bcl-2 expression and increased Bax expression. The morphology of RAW264.7 cells dramatically changed after 48 h U(VI) exposure, including the evident bubble phenomenon. Besides, U(VI) also increased the proportion of LDH releases and increased GSDMD, and Ras, p38, JNK, and ERK1/2 protein expression, which indicated that the MAPK pathway was also involved. Therefore, U(VI) ultimately led to apoptosis and pyroptosis in RAW264.7 cells. This study offered convincing proof of U(VI) immunotoxicity and established the theoretical framework for further fundamental studies on U(VI) toxicity.

Effect of humic acid derived from leonardite on the redistribution of uranium fractions in soil

Humic acids (HAs) are complex organic substances with abundant functional groups (e.g., carboxyl, phenolic-OH, etc.). They are commonly distributed in the soil environment and exert a double-edged sword effect in controlling the migration and transformation of uranium. However, the effects of HAs on dynamic processes associated with uranium transformation are still unclear. In this study, we used HAs derived from leonardite (L-HA) and commercial HA (C-HA) as exogenous organic matter and C-HA as the reference. UO₂, UO₃, and UO₂(NO₃)₂ were used as the sources of U to explore the fractionations of uranium in the soil. We also studied the behavior of the HA. The incubation experiments were designed to investigate the effects of HA on the soil pH, uranium fraction transformation, dynamic behavior of exchangeable, weak acid, and labile uranium. The observations were made for one month. The results showed that soil pH decreased for L-HA but increased for C-HA. Under these conditions, uranium tended to transform into an inactive fraction. The dynamic behavior of exchangeable, weak acid, and labile uranium varied with the sources of HA and uranium. This study highlighted that HA could affect soil pH and the dynamic redistribution of U fractions. The results suggest that the sources of HA and U should be considered when using HA as the remediation material for uranium-contaminated soils.

Horizontal and Vertical Transport of Uranium in an Arid Weapon-Tested Ecosystem

Armor-penetrating projectiles and fragments of depleted uranium (DU) have been deposited in soils at weapon-tested sites. Soil samples from these military facilities were analyzed by inductively coupled plasma-optical emission spectroscopy and X-ray diffraction to determine U concentrations and transport across an arid ecosystem. Under arid conditions, both vertical transport driven by evaporation (upward) and leaching (downward) and horizontal transport of U driven by surface runoff in the summer were observed. Upward vertical transport was simulated and confirmed under laboratory-controlled conditions, to be leading to the surface due to capillary action via evaporation during alternating wetting and drying conditions. In the field, the 92.8% of U from DU penetrators and fragments remained in the top 5 cm of soil and decreased to background concentrations in less than 20 cm. In locations prone to high amounts of water runoff, U concentrations were reduced significantly after 20 m from the source due to high surface runoff. Uranium was also transported throughout the ecosystem via plant uptake and wild animal consumption between trophic levels, but with limited accumulation in edible portions in plants and animals.

Environmental and health hazards of military metal pollution

An increasing body of literature has demonstrated that armed conflicts and military activity may contribute to environmental pollution with metals, although the existing data are inconsistent. Therefore, in this paper, we discuss potential sources of military-related metal emissions, environmental metal contamination, as well as routes of metal exposure and their health hazards in relation to military activities. Emission of metals into the environment upon military activity occurs from weapon residues containing high levels of particles containing lead (Pb; leaded ammunition), copper (Cu; unleaded), and depleted uranium (DU). As a consequence, military activity results in soil contamination with Pb and Cu, as well as other metals including Cd, Sb, Cr, Ni, Zn, with subsequent metal translocation to water, thus increasing the risk of human exposure. Biomonitoring studies have demonstrated increased accumulation of metals in plants, invertebrates, and vertebrate species (fish, birds, mammals). Correspondingly, military activity is associated with human metal exposure that results from inhalation or ingestion of released particles, as well as injuries with subsequent metal release from embedded fragments. It is also notable that local metal accumulation following military injury may occur even without detectable fragments. Nonetheless, data on health effects of military-related metal exposures have yet to be systematized. The existing data demonstrate adverse neurological, cardiovascular, and reproductive outcomes in exposed military personnel. Moreover, military-related metal exposures also result in adverse neurodevelopmental outcome in children living within adulterated territories. Experimental in vivo and in vitro studies also demonstrated toxic effects of specific metals as well as widely used metal alloys, although laboratory data report much wider spectrum of adverse effects as compared to epidemiological studies. Therefore, further epidemiological, biomonitoring and laboratory studies are required to better characterize military-related metal exposures and their underlying mechanisms of their adverse toxic effects.