Electrochemical phosphate detection in oligotrophic seawater with a stand-alone plastic electrode

The northern Adriatic Sea is a particular water system, in which the levels of nutrients are commonly low or unbalanced. In general, phosphate detection can be done with the classical molybdenum-blue method. However, the method cannot be used in oligotrophic seawater samples due to its low sensitivity and high interference problems. In this study, we present a new electrochemical method, based on the application of a plastic conductive electrode containing a molybdenum reagent embedded. The sensitivity for phosphate was high enough to detect this nutrient in oligotrophic seawater

Chapter Electrochemical phosphate detection in oligotrophic seawater with a stand-alone plastic electrode

The northern Adriatic Sea is a particular water system, in which the levels of nutrients are commonly low or unbalanced. In general, phosphate detection can be done with the classical molybdenum-blue method. However, the method cannot be used in oligotrophic seawater samples due to its low sensitivity and high interference problems. In this study, we present a new electrochemical method, based on the application of a plastic conductive electrode containing a molybdenum reagent embedded. The sensitivity for phosphate was high enough to detect this nutrient in oligotrophic seawater

New eco-sustainable feed in aquaculture: influence of insect-based diets on the content of potentially toxic elements in the experimental model zebrafish (Danio rerio).

According to the concept of circular economy, insects represent good candidates as aquafeed ingredients. Nevertheless, there are some potential chemical risks linked with insect consumption. In this study, we reared the teleost Danio rerio, used as an experimental model, with five experimental diets characterized by increasing levels (0%, 25%, 50%, 75%, and 100%) of full-fat Hermetia illucens (Hi) prepupae, substituting for fish meal (FM) and fish oil (FO). We investigated the presence of potentially toxic elements (PTEs) Cd, Pb, Ni, As, and Hg in larval (20 days), juvenile (2 months), and adult (6 months) fish. Quantitative determinations of Cd, Pb, Ni, and As were made with an atomic absorption spectrometer; the total mercury content was determined by a direct mercury analyzer. The substitution of FM and FO with Hermetia illucens meal led to a reduction in the content of some PTEs, such as Pb, As, and Ni, in fishfeed, leading to concentrations below the legal limit of undesirable substances in animal feed. By increasing the Hi meal dietary content, we observed in the Danio rerio specimens an increase in Cd, Pb, and Ni content and a reduction in As content for all life stages. Moreover, a general increase in the content of Cd, Pb, Hg, and Ni from larvae to juvenile was measured, while the shift of Danio rerio from the juvenile to the adult stage involved a significant increase in the content of Pb, Hg, and Ni. Larvae had a reduced ability to bioaccumulate metal(loid)s compared to juveniles and adults. In conclusion, the content of PTEs in Danio rerio is influenced both by the type of diet administered and by the life stage of the animal itself. This research demonstrates the possibility of using Hi prepupae as an aquafeed ingredient without exposing fish to a chemical risk and, in perspective, allows applying these eco-sustainable diets for the breeding of edible fish species, without endangering human healt

Heavy Metals in Spring and Bottled Drinking Waters of Sibylline Mountains National Park (Central Italy)

Heavy metal concentrations (cadmium, lead, and copper) in spring, tap, and bottled waters of the Sibylline Mountains National Park (central Italy) were investigated using square wave anodic stripping voltammetry from 2004 to 2011. The mean (±SD) concentrations detected (1.3 ± 0.4 ng L-1 cadmium, 14 ± 6 ng L-1 lead, and 0.16 ± 0.10 μg L-1 copper) were below the limits stipulated by Italian and European legislation for drinking and natural mineral water. In the three studied areas of the park (Mount Bove north, Mount Bove south, and springs of River Nera) with very few exceptions, both mineral waters bottled in the area and aqueduct waters from public fountains had approximately the same metal concentrations as did the spring waters from which they were derived. Conversely, substantially higher metal concentrations were found at some sites in private houses, which may be due to release of metals from old metal pipes. At the time of this study, waters of Sibylline Mountains National Park were of good quality, and no influence of the bottling process on heavy metal concentrations was found

Heavy metal distribution in organic and siliceous marine sponge tissues measured by square wave anodic stripping voltammetry

May sponge spicules represent a “tank” to accumulate heavy metals? In this study we test this hypothesis determining the distribution of Cd, Pb and Cu concentrations between organic and siliceous tissues in Antarctic Demospongia (Sphaerotylus antarcticus, Kirkpatrikia coulmani and Haliclona sp.) and in the Mediterranean species Petrosia ficiformis. Results show that although, in these sponges, spicules represent about 80% of the mass content, the accumulation of pollutant is lower in the spicules than in the corresponding organic fraction. The contribution of tissues to the total sponge content of Cd, Pb and Cu is respectively 99%, 82% and 97% for Antarctic sponges and 96%, 95% and 96% for P. ficiformis, similar in polar and temperate organisms. These results pave the way to a better understanding of the role of marine sponges in uptaking heavy metals and to their possible use as monitor of marine ecosystems, recommend by the Water Framework Directive