Environmental Chemistry and Ecotoxicology最新文献

The rapid expansion of industry leads to the emission of heavy metals into the environment, posing a significant global concern presently. The management of heavy metals holds particular significance due to their resilience and persistence in the environment. Removal technologies of heavy metals include physical and chemical treatments. Chromium (VI) was utilized as a representative of heavy metals in this research. Sorption experiments were conducted using a composite material consisting of supported nano zero-valent iron on sawdust, designated as NZVI/SD. The NZVI/SD composite was prepared through a two-step process involving the impregnation of sawdust with ferrous sulfate, followed by a chemical reduction using Sodium borohydride (NaBH₄). The adsorbent was characterized with the help of Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), X-Ray Diffraction analysis (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and chemical test. The adsorption characteristics have been investigated under various conditions, including different pH values, adsorbent dosages, initial metal ion concentrations, contact times, and varying temperatures. The optimal conditions for employing NZVI/SD for the removal of Cr(VI) were observed at a pH of 3.0, an adsorbent dosage of 0.5 g/L, an initial metal ion concentration of 61.45 mg/L, a contact time of 180 min, and a temperature of 50 °C. Sorption of Cr(VI) on NZVI/SD followed Langmuir Isotherm model. The maximum monolayer sorption capacity on NZVI/SD was 39.8 mg/g at 298 K temperature (equilibrium pH of 3.0) estimated from the Langmuir isotherm. Kinetics and thermodynamic studies on the sorption of Cr (VI) on NZVI/SD were done to understand the sorption mechanism. Sorption kinetics of Cr (VI) on NZVI/SD confirmed that pseudo second order reaction kinetics was followed concluding that the rate of adsorption depends on the analyte and the available free site of adsorbent. By employing the Langmuir isotherm model and Van't Hoff equation, the determination of thermodynamic parameters such as Gibbs free energy, enthalpy change, and entropy change of the adsorption process was facilitated. It was found that the sorption of Cr(VI) was spontaneous (∆G° = −10.36 kJ.mol⁻¹) on NZVI/SD and the process was endothermic (∆H = +4.609 kJ/mol). NZVI/SD can be effectively regenerated by elution with 1 M NaOH for 4 h.

Perchlorate is a widespread environmental pollutant and a known thyroid hormone disruptor. Little is known about the sources and pathways of human exposure to perchlorate. We measured perchlorate in drinking water, foodstuffs, indoor dust and urine collected from various locations in the United States, with a vast majority of them from New York State. The highest concentration of perchlorate was found in indoor dust, at a geometric mean (GM) concentration of 280 ng/g, followed by foodstuffs including beverages (1.77 ng/g) and drinking water (0.09 ng/mL). Among nine categories of foodstuffs analyzed, perchlorate concentrations as high as 839 ng/g were found in vegetables. The estimated average perchlorate exposure dose for adults from various sources was 141 ng/kg body weight (BW)/day. Previously reported perchlorate concentrations in breast milk from the United States in 2007 were used for the estimation of exposure doses in infants, and were 1580, 1230, and 1010 ng/kg BW/day for 0–3, 3–6, and 6–12 months of age, all exceeded the United States Environmental Protection Agency's (EPA) chronic reference dose (700 ng/kg BW/day). Breastfeeding was the dominant exposure pathway accounting for > 90% of perchlorate exposure among infants < 1 year, whereas milk, vegetables, and beverages were the dominant exposure sources (73–83%) for age groups > 1 year. Perchlorate was detected in all human urine collected from Albany, New York (N = 31) at a GM concentration of 2.30 ng/mL. The GM perchlorate exposure doses calculated from urinary concentrations, through a reverse dosimetry approach, were 46.1 and 37.8 ng/kg BW/day for age groups 16–21 and > 21 years, respectively, which were similar to those calculated from external sources of exposure.

In the absence of any hazardous substances, colloidal gold nanoparticles (AuNPs) were synthesized through the reduction and stabilization of corresponding metal cations by a simple Eucommia ulmoides bark extract (EUBE). Employing these AuNPs as catalysts, at least ten distinct azo compounds were catalyzed and analyzed. The findings reveal outstanding catalytic performance across a diverse range of azo dyes, regardless of structural complexity, the count of azo bonds, the presence of various functional groups in the side chains, differences in molecular weight, degrees of water solubility, ionic characteristics of the dyes, and the particular class of dyes, whether reactive or acidic. Regardless of these varieties, azo dyes achieved over 90% degradation within 16 min, following a first-order pseudo-kinetic reaction. This report systematically explains the mechanics of AuNPs synthesis using EUBE and the step-by-step azo dye degradation. It signifies an advancement in azo-contaminated wastewater treatment, transcending the varied types and structural complexities of azo compounds.

With the objective of understanding microbe—pesticide interactions in soil, the effect of pesticides alone and in combination on the activities of amylase, cellulase, and invertase was assessed in black, and red soils collected from the groundnut (Arachis hypogaea L.) cultivated fields of Andhra Pradesh, India. In addition, the potential bacteria that can break down chlorpyrifos was identified using biochemical assays and a partial 16S rRNA gene sequence analysis. Soil enzymes were analyzed using standard procedures described elsewhere. The activities of amylase, cellulase, and invertase were solely dependent on the dose of pesticides used in the current study. Enzyme activities were significantly increased at the level of 2.5 or 5.0 kg ha^–1, whereas increases in the concentration of pesticides at 7.5–10 kg ha⁻¹ were lethal to the enzyme activities in both soils at 10-day incubation. The effective combination for the increase in the activities of amylase, cellulase, and invertase were monocrotophos + mancozeb. Mineral salts medium with 50 ppm chlorpyrifos as a carbon source had the greatest growth of the bacteria (i.e. Pseudomonas citronellolis strain CF3) at 14th h of incubation with OD value of 0.24 at 660 nm, and the same strain could eliminate 75% of the chlorpyrifos within 24 h from the medium. Based on the present study it was concluded that insecticides used alone or in combination with fungicides at specific doses (2.5 or 5.0 kg ha⁻¹) improved the amylase, cellulase, and invertase activities, which are involved in the carbon cycle in soils. Pseudomonas citronellolis strain CF3 is a potential bacterium in the remediation of chlorpyrifos-contaminated sites.

Wildlife is at risk of exposure to rodenticides used in pest management. An industry-led stewardship scheme introduced new rules on use and sale of products across the UK in 2016, with the aim of reducing this risk. To determine if the scheme had achieved this, exposure to second generation anticoagulant rodenticides (SGARs) was measured in foxes. Liver samples from 406 foxes collected between 2011 and 2022 were analysed and the percentage presence and concentrations of SGARs, where present, from pre-stewardship and post-stewardship samples were compared. There was no statistically significant change in the percentage of foxes exposed to bromadiolone, difenacoum or summed SGAR residues after the introduction of stewardship. The percentage of foxes exposed to brodifacoum increased significantly post-stewardship, from 18% to 43%. There were no significant changes of either summed or individual SGAR concentrations post-stewardship.

These findings suggest that the industry-led stewardship scheme has not yet had the intended impact of reducing SGAR exposure in non-target wildlife, and they highlight a substantial increase in foxes encountering brodifacoum, together with weak statistical evidence of an increase in the percentage of foxes exposed to multiple SGARs.

The association between childhood metal exposure and oxidative stress levels is of paramount importance, as children are a susceptible group to metal toxicity and elevated oxidative damage has been linked to a variety of diseases. Despite the fact that urinary creatinine is commonly used to account for variations in urine dilution, it may introduce analytical bias if creatinine excretion is influenced by the same factors that affect urinary metal excretion or if metal exposure compromises kidney function. In this study, we evaluated the individual and joint association between urinary metal ion concentrations and the oxidative stress biomarker 8-hydroxy-2′ -deoxyguanosine in preschool children and assessed the moderation role of urinary creatinine. Multiple linear regression showed that copper and selenium were negatively correlated with 8-hydroxy-2′ -deoxyguanosine, arsenic and antimony were positively correlated with 8-hydroxy-2′ -deoxyguanosine. Restricted cubic spline demonstrated the non-linear relationship between lithium, nickel, arsenic, tin, and antimony and 8-hydroxy-2′ -deoxyguanosine. Bayesian kernel machine regression and quantile g-computation analyses showed a positive association between urinary metal ion concentration and 8-hydroxy-2′ -deoxyguanosine levels, with selenium being the most significant metal ion contributing to elevated oxidative stress levels. Moderation analyses revealed that the association between urinary metal ions and 8-hydroxy-2′ -deoxyguanosine is more significant at high urinary creatinine levels. The results indicated the importance of adequately accounting for urinary creatinine levels to avoid overestimation of metal exposure and distortion of the true association between metal exposure and oxidative damage.

Industrially important metal working fluids are reported to be vulnerable to microbial growth, leading to loss of its working efficiency. The present study is dedicated towards the green synthesis of Zinc Oxide (ZnO) nanoparticles using Eclipta prostrata leaf extract and investigated for antimicrobial activity. Characterization studies using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FT-IR) displayed the presence of agglomerated rod shaped ZnO nanoparticles with characteristic peak between 700 and 500 cm⁻¹, respectively. Antimicrobial testing against gram-positive and gram-negative bacteria, as well as fungi, showed the ZnO nanoparticles' effectiveness. Against gram-positive bacteria, inhibition ranged from 0.48 to 1.51 at concentrations of 25 μl to 100 μl. Against gram-negative bacteria, inhibition ranged from 0.82 to 2.02, and against fungi, inhibition ranged from 1.20 to 2.34, all at the highest concentration tested. The results of the study indicate that the ZnO nanoparticles were effective against both fungi and bacteria, more effectively against gram negative bacteria. The results suggest that the green synthesized ZnO nanoparticles from Eclipta prostrata can be exploited to reduce the load of microbial contamination in metal working fluids.

Organosulfur compounds asssociated with coal are the major contributors to environmental pollution. An organosulfur compound dibenzothiophene (DBT) occupies about 70% of all the organosulfur compounds detected in coal. Microbial desulfurization processes are evolving as a tool for the remediation of organosulfur compounds. The present work deals with a microbial processing technique developed for the degradation of an organosulfur compound DBT by a noble bacterial strain Proteus mirabilis isolated from petroleum-contaminated soil. The study revealed that the bacterium has a high tolerance towards higher concentrations of DBT and performed a normal rate of bacterial growth in a culture medium supplemented with 50 mM of DBT. The Proteus mirabilis bacterium catalyzed the microbial desulfurization of DBT present in the culture medium. It was estimated that the bacterium desulfurized about 99% of the DBT incubated in 500 mL of culture medium at 37 °C ± 2 with the Proteus mirabilis for 5 days. The high-performance liquid chromatography (HPLC) analysis showed the presence of 2-hydroxybiphenyl in the bacterial culture medium indicating that the bacterium has followed a sulfur-specific 4S microbial pathway for the degradation of DBT through the production of 2-hydroxybiphenyl.

Biochar, plants, and earthworms have good remediation effects on cadmium (Cd)-contaminated soils. However, few studies have combined all three technologies to explore the treatment of Cd-contaminated soils. This study investigated the effect of corn straw biochar addition (1% and 5% mass ratios) on soil Cd treatment in an Eisenia fetida–Solanum nigrum system. The addition of corn straw biochar increased soil pH, total nitrogen (TN), total phosphorus (TP), and soil organic carbon (SOC); adding 5% (w/w) biochar under Cd stress resulted in significant increases (P < 0.05) of soil pH, TN, TP, and SOC. Adding 5% (w/w) biochar under Cd stress increased Cd enrichment by E. fetida and S. nigrum and significantly reduced the soil total and available Cd contents (P < 0.05). The addition of biochar increased the metallothionein content of E. fetida, which functions to resist Cd stress in high-Cd environments (P < 0.05); with the addition of 5% (w/w) biochar, the metallothionein content was 1.55 times higher than in the 1% (w/w) biochar treatment, at 23.78 ng L⁻¹. Adding 5% (w/w) biochar significantly increased the Cd enrichment coefficient and transfer coefficient values of S. nigrum under high-Cd stress (P < 0.05), reaching 7.37 and 1.89, respectively. Adding 5% (w/w) biochar significantly reduced the exchangeable and acid-soluble fraction of Cd, increased the oxidizable fraction, reduced Cd bioavailability, and mitigated physiological damage (P < 0.05). The present study demonstrated that adding biochar to the E. fetida–S. nigrum system could effectively reduce the soil Cd pollution level, providing a new method and scientific guidance for the remediation of heavy metal-polluted soil.

Discarded marine plastics (DMPs) are emerging pollutants currently attracting significant attention. This present investigation focuses on the collection, characterization, and distribution analysis of DMPs collected from marine sediments followed by isolation and molecular characterization of microplastic-degrading native bacteria sequestered from Chandipur coast sediments, Bay of Bengal India. The study identified two potential microplastic-degrading strains, Exiguobacterium sp. (ON627837) and Bacillus amyloliquefacin (ON653029). The biodegradation investigation of 0.5 g of microplastic incubated under optimized conditions resulted in 4% weight loss after 30 days subject to 200 rpm constant shaking. SEM and FT-IR spectroscopy analysis of the microbial-degraded plastics' surface morphology and composition revealed uneven surfaces with residues compared with the control samples and suggested an abundance of PET (37%) which was further used for bioremediation analysis. This investigation emphasizes the significance of the biodegradation properties of the native bacterial isolates assessing the conditions and degradability of the microorganisms.