Risk assessment of heavy metal contamination in agricultural sites and river sediments at the Vatukoula gold mine, Fiji Islands

A comprehensive study was conducted to explore the concentration and distribution of heavy metals in farm soils and river sediments around a gold mining area in Fiji with particular emphasis on ecological and human health risks. Representative samples were acquired from farm sites in Matanagata Village and the Nasivi river, both situated around the Vatukoula gold mine limited (VGML), the largest operational gold mine in Fiji. Following aqua regia digestion and analysis by AAS, the average soil concentrations for Cu (110.4 mg kg–1), Cr (136.2 mg kg–1) and Cd (1.7 mg kg–1), and sediment concentrations for Pb (69.31 mg kg–1), Cd (1.82 mg kg–1), Cu (88.95 mg kg–1) and Cr (143.12 mg kg–1) were found to exceed the recommended guideline values. Based on the geo–accumulation index (Igeo) and enrichments factor (EF), the farm soils were moderately contaminated with Cd while the and sediments showed moderate to significant contamination with Pb, Ni and Cr. Ecological risk assessment confirmed moderate to considerable ecological risk in the metal–contaminated samples, with Cd and Pb generally presenting greater risk compared to other metals. Multivariate analyses including principal component analysis pointed to gold mining activities as a potential source for heavy metals in the area. Furthermore, human health risk assessment (HRA) indicated that while adults faced no significant carcinogenic or non–carcinogenic risks from metal exposure (HI < 1), children were at more risk from Co, Mn, Cr and Fe exposure, as well as potential carcinogenic risk from Cd (ILCR = 1.46E–04).

Application of Calcium-rich Clay Mineral Under Nonwoven Fabric Mats and Sand Armor as Cap Layer for Interrupting N and P Release from River Sediments

This work investigates the applicability of thermally treated calcium-rich clay minerals (CRCMs), such as sepiolite (SPL), attapulgite (ATT), and dolomite (DLM) to hinder the nitrogen (N) and phosphorus (P) release from river sediments. A non-woven fabric mat (NWFM) or a sand layer were also capped as armor layers, i.e., placed over CRCMs to investigate the capping impact on the N/P release. The capping efficiency was evaluated in a cylindrical reactor, consisting of CRCMs, armor layers, sediments, and sampled water. We monitored N/P concentrations, dissolved oxygen (DO), oxidation reduction potential, pH, and electric conductivity in overlying water over 70 days. The DO concentrations in the uncapped and capped conditions were preserved for 30 days and 70 days (until the end of experiment duration), respectively. ATT showed higher efficiency for NH4-N and T-N than the other two materials, and the capping efficiency of NH4-N was measured as 96.4%, 93.7%, and 61.6% when capped with 2 cm sand layer, 1 cm sand layer, and NWFM layer, respectively. DLM showed a superior rejection capability of PO4-P to ATT and SPL, reported as 97.2% when capped with 2 cm sand armor. The content of weakly adsorbed-P was lower in the uncapped condition than in the capping condition. It can be concluded that ATT and DLM can be used as capping agents to deactivate N and P, respectively, to reduce water contamination from sediments of the eutrophic river.

Seasonal Variation of Phthalate Esters in Urban River Sediments: A Case Study of Fengshan River System in Taiwan

The Fengshan River system is one of the major rivers in Kaohsiung City, Taiwan. This study investigated the concentration of eight phthalate esters (PAEs) in sediments of the river and the impact of potential ecological risks during the dry and wet seasons. The potential risk assessment of sediment PAEs was evaluated by adopting the total risk quotient (TRQ) method. The total PAEs concentrations (∑PAEs) in the sediments of the Fengshan River system are between 490–40,190 ng/g dw, with an average of 8418 ± 11,812 ng/g dw. Diisononyl phthalate (38.1%), bis(2-ethylhexyl) phthalate (36.9%) and di-isodecyl phthalate (24.3%) accounted for more than 99.3% of ∑PAEs. The concentration of ∑PAEs in sediments at the river channel stations is higher during the wet season (616–15,281 ng/g dw) than that during the dry season (490–1535 ng/g dw). However, in the downstream and estuary stations, the wet season (3975–6768 ng/g dw) is lower than the dry season (20,216–40,190 ng/g dw). The PAEs in sediments of the Fengshan River may have low to moderate potential risks to aquatic organisms. The TQR of PAEs in sediments at the downstream and estuary (TQR = 0.13) is higher than that in the upstream (TQR = 0.04). In addition, during the wet season, rainfall transported a large amount of land-sourced PAEs to rivers, leading to increased PAEs concentration and potential ecological risks in the upper reaches of the river.

Penicillium Amapaense sp. nov. Exilicaulis Section and New Records of Penicillium Labradorum in Brazil Isolated from Amazon River Sediments with Potential Applications in Agriculture and Biotechnology

The genus Penicillium is recognized for its ability to produce bioactive molecules with a wide range of biotechnological applications. Currently, the genus is distributed in 28 sections, with more than 50 species in the Exilicaulis section. Representative species of this section are responsible for the production of antimicrobial compounds, but they can also produce genotoxic compounds that affect commercial mushroom production or cause disease in immunosuppressed animals. In the present study, based on morphological characters such as the length of the conidia, phialides and stipes, as well as sequence analysis of the ITS region and partial sequence of CAM, TUB2 and RPB2 loci, we describe a new fungal species denominated Penicillium amapaense and report for the first time the occurrence of Penicillium labrodorum in Brazil, both of which were isolated from sediments of the Amazon River. The isolates obtained in this study for each species were submitted to antibiosis assays against 12 phytopathogenic fungi that affect important agricultural crops in Brazil and showed inhibition of 11 out of 12 of them. The production of amylase, cellulase and siderophore as well phosphate solubilization was also detected. Metabolomic analysis indicates the ability of P. labrodorum and Penicillium amapaense sp nov. to produce polyketides such as known curvularins and anthraquinones. In addition to these, unknown compounds were also detected. These results indicate the biotechnological and agricultural potential of P. labradorum and P. amapaense.

Distributions, Compositions, and Ecological Risk Assessment of Typical Pollutants in Surface Sediment of Xihe River, China

Distributions and compositions of six phthalic acid esters (PAEs), eight phenol compounds and seven heavy metals in riverbed sediments of the Xihe River in Shenyang, China. The ecological risks of these typical pollutants were investigated and evaluated based on the risk quotient (RQ) and potential ecological risk index (PERI) methods. The concentrations of total ∑6PAEs, ∑8phenols and ∑7heavy metals in sediments varied from 92.83 to 293.66 μg/g dw, 8.87 to 83.73 μg/g dw and 0.46 to 419μg/g dw. The main pollutants in Xihe River sediments are DEHP, DIBP, phenol, P-methylphenol and Cd. More than half target PAEs and phenol compounds in sediment of the Xihe River exhibited medium or high ecological risk. Cd poses a very high ecological risk to the Xihe River Basin. It is imperative to take some effective measures to reduce the pollution of those contaminants.

Role of River–Lake System Sediments and Microbial Activity in the Hyporheic Zone

The effect of river–lake systems on the surface water self-purification process is a significant and not fully recognised scientific issue. The conditions prevailing in the hyporheic zone of these ecosystems are of great importance in the process of component exchange between water and sediments. The aim of this study was to investigate the influence of the type of sediments located at the bottom of the riverbed being part of a river–lake system on microbial activity in the hyporheic zone. An ex situ experiment was used to study the microbiological activity and the transformation of components in the collected river sediments. It was found that the specific properties of sediments varied depending on their location in the riverbed between the lakes comprising the system and that the prevailing meteorological conditions can also have an effect on microbial activity in the hyporheic zone, e.g., aerobic conditions. These conditions determined the intensity of component conversion in the sediments due to microbial metabolism. A closer understanding of the processes occurring in the hyporheic zone may allow the processes of water self-purification within river–lake systems to be supported in the future, which will contribute to the improvement of surface water quality.