Abstract

The constant growth of the offshore oil and gas industry raised questions about its impact on marine ecosystems and biological resources. Considering the potential adverse impacts on the marine environment, a greater level and continuous monitoring of the offshore sites, detecting the presence of pollutants, may be required.

Our research was focused on the design of an autonomous system for detection of heavy metals in water by spectrophotometric analysis. The ground-breaking idea is the implementation of a system inspired to the latest innovative techniques in the field of the microfluidic analysis, based on Lab-on-Chip. Such a choice is due to the unique advantages in terms of reduction of sample and reagents volumes, energy budget and analysis times, besides the possible multi-element analysis on the same sample.

Hexavalent Chrome and Zinc were first considered as detected metal ions, by Diphenylcarbazide and Zincon methods respectively. Main process parameters were individually optimized, to be suitable for a miniaturized and portable device, for real time monitoring system, starting from the standard methods reported in literature. Finally, the optimized values were merged to test any possible mutual effects.

In both cases, the optimized method provided a good agreement of the calibration curve with Lambert & Beer law, till metal concentrations of 5-10 ppb. Test on the bench prototype confirmed the encouraging results obtained at laboratory scale; moreover, test on the field demonstrated the validity of the system and its complete automation.

Introduction

The greatly increased circulation of toxic metals through the soil, water, and air and their inevitable transfer to the human food chain remains an important environmental issue which entails some unknown risks for future generations. [1]

Heavy metals are often referred to as "trace metals", occurring in low concentrations in organisms.

Serious global health concerns are due to the build-up of heavy metals and metalloids in soils and waters, as these metals and metalloids cannot be degraded into non-toxic forms b0ut persist in the ecosystem. [2,3]

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