Mackkjer5027

Cadmium (Cd) is a highly toxic element and non-essential to human. Herein, the source and fate of Cd were examined in a typical sediment profile from the North River, South China, which was affected by the massive Pb-Zn smelting activities for decades. An exceptionally high enrichment of Cd, 107-441 mg/kg, was observed across the whole profile. 17β-estradiol datasheet Approximately 50-75% of Cd was retained in the weak acid soluble fraction. Risk assessment based on geoaccumulation index (Igeo), potential ecological risk index (Eri), bioavailable metal index (BMI) and toxic risk index (TRI) further indicated an extremely strong degree of potential ecological pollution and high toxic risks. The mineralogical composition of particles from the sediment profile exhibited the presence of pyrite, magnetite, wurtzite and greenockite. This further confirmed that Cd was migrated from smelting slags to the North River basin and enriched in sediment profile. Sediment Cd speciation analysis also implied a possible transformation of Cd from metal oxides in smelting slags to adsorbed phases and carbonates, which enhances the bioavailability of Cd. The findings indicate proper countermeasures or remediation approaches should be promptly taken towards high ecological risks of Cd arising from the depth profile extending nearly 1 m, due to lead-zinc smelting related activities. Polycyclic aromatic hydrocarbons (PAHs) are widespread pollutants in marine ecosystems including threatened and potentially sensitive coral reefs. Lower organisms such as phytoplankton, known to bioconcentrate PAHs, could serve as potential entry points for these chemicals into higher trophic levels. Here, we present a novel method using a 13C-labelled PAH and cavity ring-down spectroscopy (CRDS) to investigate accumulation, uptake rates and trophic transfer of PAHs in corals, which are key organisms to sustain biodiversity in tropical seas. We quantified the accumulation of 13C-phenanthrene in the marine microalga Dunaliella salina, and in the coral Acropora millepora after diffusive uptake from seawater or dietary uptake via labelled D. salina. Additionally, we monitored the photophysiological health of D. salina and A. millepora during phenanthrene exposure by pulse-amplitude modulation (PAM) fluorometry. Dose-dependent accumulation of 13C-phenanthrene in the microalga showed a mean bioconcentration factor (BCF) of 2590 ± 787 L kg-1 dry weight. Corals accumulated phenanthrene from both exposure routes. While uptake of 13C-phenanthrene in corals was faster through aqueous exposure than dietary exposure, passive diffusion showed larger variability between individuals and both routes resulted in accumulation of similar concentrations of phenanthrene. The 13C-PAH labelling and analysis by CRDS proved to be a highly sensitive method. The use of stable isotopic label eliminated additional toxicity and risks by radioactive isotopic-labelling, and CRDS reduced the analytical complexity of PAH (less biomass, no extraction, fast analysis). The simultaneous, precise quantification of both carbon content and 13C/12C ratio (δ13C) enabled accurate determination of 13C-phenanthrene accumulation and uptake rate. This is the first study to provide empirical evidence for accumulation of phenanthrene in a phytoplankton-coral food chain. A study was performed to assess if nitrate reductase (NR) participated in brassinosteroid (BR)-induced cadmium (Cd) stress tolerance primarily by accelerating the ascorbate-glutathione (AsA-GSH) cycle. Prior to initiating Cd stress (CdS), the pepper plants were sprayed with 0.5 μM 24-epibrassinolide (EBR) every other day for 10 days. Thereafter the seedlings were subjected to control or CdS (0.1 mM CdCl2) for four weeks. Cadmium stress decreased the plant growth related attributes, water relations as well as the activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), but enhanced proline content, leaf Cd2+ content, oxidative stress-related traits, activities of ascorbate peroxidase (APX) and glutathione reductase (GR), and the activities of antioxidant defence system-related enzymes as well as NR activity and endogenous nitric oxide content. EBR reduced leaf Cd2+ content and oxidative stress-related parameters, enhanced plant growth, regulated water relations, and led to further increases in proline content, AsA-GSH cycle-related enzymes' activities, antioxidant defence system-related enzymes as well as NR activity and endogenous nitric oxide content. The EBR and the inhibitor of NR (tungstate) reversed the positive effects of EBR by reducing NO content, showing that NR could be a potential contributor of EBR-induced generation of NO which plays an effective role in tolerance to CdS in pepper plants by accelerating the AsA-GSH cycle and antioxidant enzymes. In back-fill mining, how to rapidly increase the concentration of tailings is an important problem facing mining engineers. In this paper, the effects of ultrasound frequency (17-25 kHz), power (50-100 W), duration (5-20 min) and start time (3-12 min) on the final underflow concentration (FUC) of unclassified tailings (UTs) were investigated. The flocculation-sedimentation and thickening of tailings were compared with and without ultrasound application. The response surface method was applied to analyze the primary and secondary relationships and interactive relationships between the various ultrasound operating parameters and the FUC, and the optimal conditions were determined. In addition, Environmental Scanning Electron Microscope (E-SEM) was used to analyze the structural changes of underflow aggregates and clearly demonstrated a denser underflow after ultrasound treatment. The results indicated that ultrasound can significantly improve the underflow concentration of the UTs slurry. The frequency and power are the most important influencing factors. The best conditions for ultrasound application are a frequency of 20.4 kHz, power of 90 W, duration of 6.2 min and start time at 15.0 min. The FUC reached 71.75% after several minutes of sonication, which is 4.31% higher than the FUC of free flocculation. The results of E-SEM analysis showed significant differences among the microstructures of settled tailings (STs) after free flocculation and 17 and 20 kHz ultrasound treatment. Ultrasound at a frequency of 20 kHz has a more effective mechanical vibration and cavitation action and can therefore effectively break the polymer flocculant chains into shorter chains and promote the compaction of tailings and the release of water. The size distributions of the flocs before and after sonication also support this conclusion. V.