An innovative autonomous robotic system for on-site detection of heavy metal pollution plumes in surface water

Use of Unmanned Surface Vehicles (USVs) in Water Chemistry Studies

Unmanned surface vehicles (USVs) equipped with integrated sensors are a tool valuable to several monitoring strategies, offering enhanced temporal and spatial coverage over specific timeframes, allowing for targeted examination of sites or events of interest. The elaboration of environmental monitoring programs has relied so far on periodic spot sampling at specific locations, followed by laboratory analysis, aiming at the evaluation of water quality at a catchment scale. For this purpose, automatic telemetric stations for specific parameters have been installed by the Institute of Marine Biological Resources and Inland Waters of Hellenic Centre for Marine Research (IMBRIW-HCMR) within several Greek rivers and lakes, providing continuous and temporal monitoring possibilities. In the present work, USVs were deployed by the Athens Water and Sewerage Company (EYDAP) as a cost-effective tool for the environmental monitoring of surface water bodies of interest, with emphasis on the spatial fluctuations of chlorophyll α, electrical conductivity, dissolved oxygen and pH, observed in Koumoundourou Lake and the rivers Acheloos, Asopos and Kifissos. The effectiveness of an innovative heavy metal (HM) system installed in the USV for the in situ measurements of copper and lead was also evaluated herewith. The results obtained demonstrate the advantages of USVs, setting the base for their application in real-time monitoring of chemical parameters including metals. Simultaneously, the requirements for accuracy and sensitivity improvement of HM sensors were noted, in order to permit full exploitation of USVs' capacities.

Sub-Liquid and Atmospheric Measurement Instrument To Autonomously Monitor the Biochemistry of Natural Aquatic Ecosystems

Monitoring the biochemistry of aquatic ecosystems is critical to understanding the biogeochemical cycling induced by microorganisms. They play a vital role in climate-gaseous drivers associated with natural ecosystems, such as methane emission in wetlands and peatlands; gas cycling and fixation: methane, sulfur, carbon, and nitrogen; water quality assessment and remediation; monitoring oxygen saturation due to contamination and algal proliferation; and many more. Microorganisms interact with these environments inducing diurnal and seasonal changes that have been, to date, poorly characterized. To aid with the long-term in-situ monitoring of natural aquatic ecosystems, we designed a Sub-liquid and Atmospheric Measurement (SAM) instrument. This floating platform can autonomously measure various sub-liquid and atmospheric parameters over a long time. This paper describes the design of SAM and illustrates how its long-term operation can produce critical information to complement other standard laboratory-based microbiological studies.

Microfluidic Devices for Heavy Metal Ions Detection: A Review

The contamination of air, water and soil by heavy metal ions is one of the most serious problems plaguing the environment. These metal ions are characterized by a low biodegradability and high chemical stability and can affect humans and animals, causing severe diseases. In addition to the typical analysis methods, i.e., liquid chromatography (LC) or spectrometric methods (i.e., atomic absorption spectroscopy, AAS), there is a need for the development of inexpensive, easy-to-use, sensitive and portable devices for the detection of heavy metal ions at the point of interest. To this direction, microfluidic and lab-on-chip (LOC) devices fabricated with novel materials and scalable microfabrication methods have been proposed as a promising approach to realize such systems. This review focuses on the recent advances of such devices used for the detection of the most important toxic metal ions, namely, lead (Pb), mercury (Hg), arsenic (As), cadmium (Cd) and chromium (Cr) ions. Particular emphasis is given to the materials, the fabrication methods and the detection methods proposed for the realization of such devices in order to provide a complete overview of the existing technology advances as well as the limitations and the challenges that should be addressed in order to improve the commercial uptake of microfluidic and LOC devices in environmental monitoring applications.

Electroanalytical Trace Metal Cations Quantification and Speciation in Freshwaters: Historical Overview, Critical Review of the Last Five Years and Road Map for Developing Dynamic Speciation Field Measurements

An historical overview covering the field of electroanalytical metal cations speciation in freshwaters is presented here, detailing both the notable experimental and theoretical developments. Then, a critical review of the progress in the last five years is given, underlining in particular the improvements in electrochemical setups and methodologies dedicated to field surveys. Given these recent achievements, a road map to carry out on-site dynamic metal speciation measurements is then proposed, and the key future developments are discussed. This review shows that electroanalytical stripping techniques provide a unique framework for quantitatively assessing metals at trace levels while offering access to both thermodynamic and dynamic features of metal complexation with natural colloidal and particulate ligands.

Recent advances in instrumental techniques for heavy metal quantification

Heavy metals (HMs) are ubiquitous; they are found in soil, water, air, and all biological matrices. The toxicity, bioaccumulation potential, and deleterious effects of most of these metals on humans and the environment have been widely documented. Consequently, the detection and quantification of HMs in various environmental samples have become a pressing issue. The analysis of the concentrations of HMs is a vital component of environmental monitoring; hence, the selection of the most suitable analytical technique for their determination has become a topic of great interest in food, environment, and human health safety. Analytical techniques for the quantification of these metals have evolved. Presently, a broad range of HM analytical techniques are available with each having its outstanding merits as well as limitations. Most analytical scientists, therefore, adopt complementation of more than one method, with the choice influenced by the specific metal of interest, desired limits of detection and quantification, nature of the interference, level of sensitivity, and precision among others. Sequel to the above, this work comprehensively reviews the most recent advances in instrumental techniques for the determination of HMs. It gives a general overview of the concept of HMs, their sources, and why their accurate quantification is pertinent. It highlights various conventional and more advanced techniques for HM determination, and as one of its kind, it also gives special attention to the specific merits and demerits of the analytical techniques. Finally, it presents the most recent studies in this regard.

Optimized porous carbon-fibre microelectrode for multiplexed, highly reproducible and repeatable detection of heavy metals in real water samples

This work demonstrates the simultaneous identification of four hazardous heavy metals in water samples, namely copper, lead, cadmium, and mercury. A simple yet selective electrode with the simplest fabrication procedure was used. The modified porous carbon threads coated with gold nanoparticles (AuNPs) was employed as a working electrode. The surface chemistry and morphology of the AuNPs deposited porous carbon thread surface were examined. The electrocatalytic activity of the metals on the Au-modified thread surface was observed using the differential pulse voltammetry (DPV) technique. Furthermore, all four metal ions were detected simultaneously, and no interference was observed. Individual and simultaneous experiments to test the impact of concentration revealed that the limit of detection (LoD) was observed to be 1.126 μM, 1.419 μM, 0.966 μM, 0.736 μM for the Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ metal ions respectively in a linear concentration range of 10-110 μM of each. Subsequently, the study of pH, interference with coexisting metal ions, repeatability study, and stability analysis was also performed. A real sample analysis utilising three different lake water samples is also carried out to further understand the application of the proposed sensor. A good recovery rate is achieved, and the results are reported. This work paves way for the on-field applicability of the present heavy metal detection platform.

Waste biomass based potential bioadsorbent for lead removal from simulated wastewater

Present study deals with the lead removal from simulated wastewater using cost effective bio-adsorbent of mango seeds cover with kernel (M), and jamun seeds cover with kernel (JP). Lead removal optimization of adsorption parameters has been analyzed by using Response surface methodology (RSM). The optimum adsorption was attained at speed of 500 rpm, 60 mg, pH 6.5 and contact time of 120 min. The adsorption capacities are around 39.15 mg/g of M and 20.28 mg/g of JP bio-adsorbent, and also the maximum Pb removal were observed ̴ 94.85% and 92.78%, respectively. The regression coefficient was best fitted for both bio-adsorbents are Freundlich model and pseudo-first order reaction kinetic.