Iron oxide-supported gold nanoparticle electrode for simultaneous detection of arsenic and sulfide on-site

The environmental behavior of arsenic (As) has garnered significant attention due to its hazardous nature. The fate of As often couples with sulfide, thus co-detecting arsenic and sulfide on-site is crucial for comprehending their geochemical interactions. While electrochemical methods are suitable for on-site chemical analysis, there currently exists no electrode capable of simultaneously detecting both arsenic and sulfide. To address this, we developed a dual-metal electrode consisting of iron oxide-encased carbon cloth loaded with gold nanoparticles (Au/FeOx/CC) using the electrochemical deposition method. This electrode enables square wave stripping voltammetry (SWASV) binary detection of As and sulfide. Comparison experiments reveal that the reaction sites for sulfide primarily reside on FeOx, while the interface synergy of iron oxide and gold nanoparticles enhances the response to arsenite (AsIII). Arsenate (AsV) is directly reduced to As0 on Fe0, obviating the need for an external reducing agent. The electrode achieves detection limits of 1.5 μg/L for AsV, 0.25 μg/L for AsIII, and 11.6 μg/L for sulfide at mild conditions (pH 7.8). Field validation was conducted in the Tengchong geothermal hot spring region, where the electrochemical method exhibited good correlation with the standard methods: Total As (r = 0.978 vs. ICP-MS), AsIII (r = 0.895 vs. HPLC-ICP-MS), and sulfide (r = 0.983 vs. colorimetric method). Principal component analysis and correlation analysis suggest that thioarsenic, could potentially be positive interferents for AsIII. However, this interference can be anticipated and mitigated by monitoring the abundance of sulfide. The study provides new insights and problems for the electrochemical detection of coexisted As and sulfide.

Variability of particulate organic carbon and assessment of satellite retrieval algorithms over the eastern Arabian Sea

Particulate organic carbon (POC) and its variability were studied to assess the accuracy of ocean colour retrieval algorithms over the eastern Arabian Sea (EAS) as it controls the carbon sequestration, oxygen minimum zone and biogeochemical (C, N and P) cycles. The seasonality in the physical and biological processes strongly influenced the distribution of POC along the EAS. Higher POC and chlorophyll a (chl a) during the spring inter monsoon (SIM) in the north EAS were due to detrainment bloom. The lower POC:chl a ratios during the winter monsoon (WM) (299.8 ± 190.8) than the SIM (482.1 ± 438.3) were due to the influence of freshly derived organic matter with high nutrient levels. The moderate coefficient of regression values of POC with chl a (R² = 0.49, N = 59) suggests the importance of dead organic materials in controlling the POC distribution in the EAS. Validation between satellite and in situ POC using the four ocean colour retrieval algorithms showed that the algorithm based on the ratio of remote sensing reflectance (Rrs) performed better (R² = 0.6, N = 17). It also showed a linear trend of POC with absorption coefficients suggesting it as an optical proxy for the POC retrieval.

Semiochemical oviposition cues to control Aedes aegypti gravid females: state of the art and proposed framework for their validation

In the fight against mosquito-borne diseases, odour-based lures targeting gravid females represent a promising alternative to conventional tools for both reducing mosquito populations and monitoring pathogen transmission. To be sustainable and effective, they are expected to use semiochemicals that act specifically against the targeted vector species. In control programmes directed against Aedes aegypti, several candidates of different origins (conspecifics, plants) have already been identified as potential oviposition attractants or repellents in laboratory experiments. However, few of these candidates have received validation in field experiments, studies depicting the active molecules and their mode of perception are still scarce, and there are several methodological challenges (i.e. lack of standardization, differences in oviposition index interpretation and use) that should be addressed to ensure a better reproducibility and accelerate the validation of candidates. In this review, we address the state of the art of the compounds identified as potential candidates for trap development against Ae. aegypti and their level of validation. We also offer a critical methodological analysis, highlight remaining gaps and research priorities, and propose a workflow to validate these candidates and to increase the panel of odours available to specifically trap Ae. aegypti.

One-pot synthesis of β-cyclodextrin amended mesoporous cerium(IV) incorporated ferric oxide surface towards the evaluation of fluoride removal efficiency from contaminated water for point of use

Surface modified Cerium(IV)-incorporated hydrous Fe(III) oxide (CIHFO) with β-cyclodextrin (β-CD) nanocomposite (βC-CIHFO) has been developed by in-situ wet chemical deposition method and characterized by means of some analytical tools such as FTIR, XRD,OM, SEM-EDX, TEM-EDX, AFM, TG-DTA and BET surface area analyses, resembled the irregular and undulated surface morphology consisting of microcrystals (∼2-3 nm) and mesoporous (∼6.022 nm) structure confirm surface amended CIHFO with β-CD. Enhanced fluoride adsorption capacity of βC-CIHFO (107.62 mg g^-1) than pure CIHFO (32.62 mg g^-1) at pH 7.0 is due to the plenty of surface -OH groups of β-CD, which plays a crucial role in enhancing fluoride adsorption capacity of CIHFO. Kinetic studies obeyed pseudo-second order kinetics and multilayer adsorption process, respectively. The adsorption process is reasonably spontaneous and endothermic in nature. Minute amount of βC-CIHFO (1.8 g L^-1) can effectively treat fluoride containing natural groundwater samples (9.05 mg L^-1) and achieved desirable permissible level in a while. The adsorbent was magnificently regenerated up to 75.19% with a solution of pH 13.0, and can be reused up to five cycles ensures sustainable use of proposed adsorbent for fluoride removal from aqueous media.

Spores of Beauveria bassiana and Trichoderma lignorum as a bioinsecticide for the control of Atta cephalotes

Background

The leafcutter ant (Atta cephalotes) is associated with losses in the agricultural sector, due to its defoliating activity; for its control, biological, mechanical and chemical methods have been developed, the latter associated with adverse effects on human and environmental health. This research validated in the field for the control of the leafcutter ant (A. cephalotes) using a mixture of Beauveria bassiana and Trichoderma lignorum spores.

Methods

The effectiveness from the combination of spores of B. bassiana and T. lignorum with an initial concentration of 2 × 10⁹ spores/ml, in the following proportions of B. bassiana and T. lignorum, A (1:1), of each fungus. It was evaluated within the university campus, comparing it with two commercial formulations, Mycotrol (B. bassiana) and Mycobac (T. lignorum). Additionally, this formulation was evaluated in 49 nests distributed 16 in 14 locations in Colombia. The formulation application was carried out by direct application, using a pump at a speed of 10 ml/m². The effectiveness was estimated from the reduction of the flow of ants, evaluating the statistically significant differences using the ANOVA and Tukey-test.

Results

Effective control of 90% of the nests was observed in the field phase in 60 days, except in nests with areas > 50 m² that were located in regions with high rainfall (annual average precipitation above 7000 mm), such as Buenaventura.

Conclusions

In this work, it was demonstrated that the combination of B. bassiana and T. lignorum spores represent a viable alternative for the control of the leafcutter ant, in which the effectiveness is related to several factors, including the size of the nest and the rainfall in the area.

Enhanced capacity of fluoride scavenging from contaminated water by nano-architectural reorientation of cerium-incorporated hydrous iron oxide with graphene oxide

An in situ wet chemical deposition method has been applied for the successful surface modification of Ce (IV)-incorporated hydrous Fe(III) oxide (CIHFO) with a hydrophilic graphene precursor, graphene oxide (GO). The surface area of as-prepared composite (GO-CIHFO) has enhanced (189.57 m² g^-1) compared with that of pristine CIHFO (140.711 m² g^-1) and has irregular surface morphology consisting of microcrystals (~ 2-3 nm) and mesoporous (3.5486 nm) structure. The GO-CIHFO composite shows enhanced fluoride scavenging capacity (136.24 mg F g^-1) than GO (3 mg F g^-1) and pristine CIHFO (32.62 mg F g^-1) at pH 7.0. Also, in acidic pH range and at 323 K temperature, the Langmuir capacity of as-prepared composite is 190.61 mg F g^-1. It has been observed that fluoride removal by GO-CIHFO occurs from solutions obeying pseudo-second-order kinetics and multilayer adsorption process. The film/boundary layer diffusion process is also the rate-determining step. The nature of the adsorption reaction is reasonably spontaneous and endothermic in thermodynamic sense. It was observed that 1.2 g.L^-1 of GO-CIHFO dosage can effectively optimise the fluoride level of natural groundwater samples (9.05 mg L^-1) to the desirable permissible limit. Reactivation of used material up to a level of 73.77% with a solution of alkaline pH has proposed reusability of nanocomposites ensuring sustainability of the proposed material as fluoride scavenger in future.

Fire and burn severity assessment: Calibration of Relative Differenced Normalized Burn Ratio (RdNBR) with field data

The assessment of burn severity is highly important in order to describe and measure the effects of fire on vegetation, wildlife habitat and soils. The estimation of burn severity based on remote sensing is a powerful tool that, to be useful, needs to be related and validated with field data. The present paper explores the relationships between field accessible variables and Relative Differenced Normalized Burn Ratio (RdNBR) index by using linear mixed-effects models and boosted regression trees, based on data from 28 large fires and 668 field measurements across three countries in southern Europe. The RdNBR clearly reflected the mean height of charred stem and loss of ligneous, living shrub and tree cover during the fire. The paper confirms that remote sensing indices provide an acceptable assessment of fire induced impact on forest vegetation but also highlights there are important between-fire variations due to specific contexts that modify these relationships. These variations can be effectively assessed and should be taken into account in future predictive efforts.

Determination and validation of soil thresholds for cadmium based on food quality standard and health risk assessment

Cadmium (Cd) is an environmental toxicant with high rates of soil-plant transfer. It is essential to establish an accurate soil threshold for the implementation of soil management practices. This study takes root vegetable as an example to derive soil thresholds for Cd based on the food quality standard as well as health risk assessment using species sensitivity distribution (SSD). A soil type-specific bioconcentration factor (BCF, ratio of Cd concentration in plant to that in soil) generated from soil with a proper Cd concentration gradient was calculated and applied in the derivation of soil thresholds instead of a generic BCF value to minimize the uncertainty. The sensitivity variations of twelve root vegetable cultivars for accumulating soil Cd and the empirical soil-plant transfer model were investigated and developed in greenhouse experiments. After normalization, the hazardous concentrations from the fifth percentile of the distribution based on added Cd (HC5_add) were calculated from the SSD curves fitted by Burr Type III distribution. The derived soil thresholds were presented as continuous or scenario criteria depending on the combination of soil pH and organic carbon content. The soil thresholds based on food quality standard were on average 0.7-fold of those based on health risk assessment, and were further validated to be reliable using independent data from field survey and published articles. The results suggested that deriving soil thresholds for Cd using SSD method is robust and also applicable to other crops as well as other trace elements that have the potential to cause health risk issues.

Bioenergy and biodiversity: Intensified biomass extraction from hedges impairs habitat conditions for birds

Biomass is increasingly used as an alternative source for energy in Europe. Woody material cut from hedges is considered to provide a suitable complement to maize and oilseed rape, which are currently the dominant biomass sources. Since shrubs and trees are also important habitats for birds, however, coppicing of hedges at the landscape scale may adversely affect the diversity of the avifauna. To evaluate this risk, we estimated the response of hedge birds to three management scenarios differing in cutting intensity and hedge selection. The analysis was done using hedge data of the Lautertal municipality (n = 339 hedges; Vogelsberg area, Hesse, Germany). It focused on 25 bird species, which are all listed in the hedge programme of the German Ornithological Stations. Information on the preferences of these birds for certain hedge features such as height or width was gathered by an extensive literature review. A cluster analysis on the consolidated literature data allowed us to identify three groups of birds according to their preference for certain hedge attributes. Two groups, which included Yellowhammer (Emberiza citrinella L.) (i) and Blackbird (Turdus merula L.) (ii), favoured trees located in hedges, but differed in their preference for hedge shape, with (i) being attracted by long and broad hedges and (ii) by high hedges. The third group, which included the Whitethroat (Sylvia communis L.), preferred small hedges with gaps and medium vegetation density. Spatially explicit suitability models based on these data allowed us to predict the status quo of hedge suitability for these species groups. Field surveys proved the accuracy of the predictions to be sufficient, since the hedge suitability predicted was significantly and positively correlated to the occurrence of 9 out of the 12 testable focal species. Our models predicted biomass extraction to almost always reduce hedge suitability for the three bird groups. Concerning the Yellowhammer and the Blackbird group, a high level of biomass extraction reduced hedge suitability by approximately 20%. We thus conclude that intensively extracting biomass can significantly reduce hedge suitability for birds, despite considerable differences in habitat requirements. Considering the variable response of the bird groups to our scenarios as well as the variation in habitat occupancy by birds, however, cutting woody material from hedges nevertheless provides an option to reduce adverse effects of bioenergy production on biodiversity at the landscape scale, as long as hedge management is based on the best knowledge available.

Development of a bioavailability-based risk assessment approach for nickel in freshwater sediments

To assess nickel (Ni) toxicity and behavior in freshwater sediments, a large-scale laboratory and field sediment testing program was conducted. The program used an integrative testing strategy to generate scientifically based threshold values for Ni in sediments and to develop integrated equilibrium partitioning-based bioavailability models for assessing risks of Ni to benthic ecosystems. The sediment testing program was a multi-institutional collaboration that involved extensive laboratory testing, field validation of laboratory findings, characterization of Ni behavior in natural and laboratory conditions, and examination of solid phase Ni speciation in sediments. The laboratory testing initiative was conducted in 3 phases to satisfy the following objectives: 1) evaluate various methods for spiking sediments with Ni to optimize the relevance of sediment Ni exposures; 2) generate reliable ecotoxicity data by conducting standardized chronic ecotoxicity tests using 9 benthic species in sediments with low and high Ni binding capacity; and, 3) examine sediment bioavailability relationships by conducting chronic ecotoxicity testing in sediments that showed broad ranges of acid volatile sulfides, organic C, and Fe. A subset of 6 Ni-spiked sediments was deployed in the field to examine benthic colonization and community effects. The sediment testing program yielded a broad, high quality data set that was used to develop a Species Sensitivity Distribution for benthic organisms in various sediment types, a reasonable worst case predicted no-effect concentration for Ni in sediment (PNECsediment ), and predictive models for bioavailability and toxicity of Ni in freshwater sediments. A bioavailability-based approach was developed using the ecotoxicity data and bioavailability models generated through the research program. The tiered approach can be used to fulfill the outstanding obligations under the European Union (EU) Existing Substances Risk Assessment, EU Registration, Evaluation, Authorisation, and Regulation of Chemicals (REACH), and other global regulatory initiatives. Integr Environ Assess Manag 2016;12:735-746. © 2015 SETAC.

Environmental relevance of laboratory-derived kinetic models to predict trace metal bioaccumulation in gammarids: Field experimentation at a large spatial scale (France)

Kinetic models have become established tools for describing trace metal bioaccumulation in aquatic organisms and offer a promising approach for linking water contamination to trace metal bioaccumulation in biota. Nevertheless, models are based on laboratory-derived kinetic parameters, and the question of their relevance to predict trace metal bioaccumulation in the field is poorly addressed. In the present study, we propose to assess the capacity of kinetic models to predict trace metal bioaccumulation in gammarids in the field at a wide spatial scale. The field validation consisted of measuring dissolved Cd, Cu, Ni and Pb concentrations in the water column at 141 sites in France, running the models with laboratory-derived kinetic parameters, and comparing model predictions and measurements of trace metal concentrations in gammarids caged for 7 days to the same sites. We observed that gammarids poorly accumulated Cu showing the limited relevance of that species to monitor Cu contamination. Therefore, Cu was not considered for model predictions. In contrast, gammarids significantly accumulated Pb, Cd, and Ni over a wide range of exposure concentrations. These results highlight the relevance of using gammarids for active biomonitoring to detect spatial trends of bioavailable Pb, Cd, and Ni contamination in freshwaters. The best agreements between model predictions and field measurements were observed for Cd with 71% of good estimations (i.e. field measurements were predicted within a factor of two), which highlighted the potential for kinetic models to link Cd contamination to bioaccumulation in the field. The poorest agreements were observed for Ni and Pb (39% and 48% of good estimations, respectively). However, models developed for Ni, Pb, and to a lesser extent for Cd, globally underestimated bioaccumulation in caged gammarids. These results showed that the link between trace metal concentration in water and in biota remains complex, and underlined the limits of these models, in their present form, to assess trace metal bioavailability in the field. We suggest that to improve model predictions, kinetic models need to be complemented, particularly by further assessing the influence of abiotic factors on trace metal uptake, and the relative contribution of the trophic route in the contamination of gammarids.