Microplastic accumulation in benthic invertebrates in Terra Nova Bay (Ross Sea, Antarctica)

Microplastic contamination of the benthic invertebrate fauna in Terra Nova Bay (Ross Sea, Antarctica) was determined. Twelve macrobenthic species, characterized by different feeding strategies, were selected at 3 sampling sites at increasing distance from the Italian Scientific Base (Mario Zucchelli, Camp Icarus, Adelie Cove). The 83% of the analyzed macrobenthic species contained microplastics (0.01–3.29 items mg−1). The size of the particles, measured by Feret diameter, ranged from 33 to 1000 µm with the highest relative abundance between 50 and 100 µm. Filter-feeders and grazers displayed values of microplastic contamination from 3 to 5 times higher than omnivores and predators, leading to the hypothesis that there is no evident bioaccumulation through the food web. The prevalent polymers identified by micro-FTIR were nylon (86%) and polyethylene (5%); other polymers identified in Antarctic benthos were polytetrafluoroethylene, polyoxymethylene, phenolic resin, polypropylene, polystyrene resin and XT polymer

Preparation and Characterization of Fluorescence Probe from Assembly Hydroxyapatite Nanocomposite

A new nanocomposite fluorescence probe with thioglycolic acid (TA) functional layers embedded inside the hydroxyapatite nanoribbon spherulites has been synthesized. The fluorescence intensity of the novel probe is about 1.5–3.3-fold increase compared with the probe containing no TA. When used to detect cadmium ion, the most of original assembly nanoribbon spherulites structure in the novel probe is found to have been damaged to new flake structures. The mechanism of determining cadmium ion in alcohol solution has been studied. The present systematic study provides significant information on the effect of assembly nanostructure on the metal-enhanced fluorescence phenomenon

Removal of Lead, Copper, Zinc and Cadmium from Water Using Phosphate Rock

Removal of Pb(2+), Cu(2+), ZD(2+) and Cd(2+) from aqueous solutions by sorption on a natural phosphate rock (FAP) was investigated. The effects of the contact time and initial metal concentration were examined in the batch method. The percentage sorption of heavy metals from solution ranges generally between 50% and 99%. The amount of sorbed metal ions follows the order Cu>Pb>Cd>Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate. The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb(2+), Cu(2+), ZD(2+) and Cd(2+) from polluted waters

Synthetic phosphates as binding agent of Pb, Zn, Cu and Cd in the environment

The sorption of Pb, Zn, Cu and Cd from aqueous multiple-species solutions by synthetic hydroxyapatite (HAP) was investigated. HAP was reacted with solutions containing different heavy metals concentrations (10, 100 and 500 mg/L) for four times (2, 4, 24 and 48h). The results showed that HAP was very effective in removal heavy metals from aqueous solutions. Approximately 95-99% of the Pb applied was removed from solutions, with the best sorption capacity of 497 mg of Pb/g of HAP, while 92-99% of Zn, 93-99% of Cu and 88-99% of Cd added were attenuated, with best removal capacity of 498, 485 and 477 mg/g, respectively. Sorption mechanisms other than dissolution/precipitation of crystalline phases could be involved in attenuating heavy metals concentrations such as ion exchange, coprecipitation, surface complexation and formation of amorphous phases. The study results confirm HAP provides a cost effective method for the decontamination of solutions polluted by heavy metals

Immobilization of heavy metals in water and soil by phosphate treatment

Heavy metals such as Pb, Cd, Cu, Zn, Hg, Cr, and Ni are the main contaminants of surface water, groundwater, and soils. The heavy metals are of great concern because of their extreme toxicity even at low concentration and the tendency to accumulate in the food chain. Conventional methods for heavy metal removal from water and soil include chemical precipitation, filtration, solvent extraction, electrochemical technique, ion exchange, and adsorption. In particular, chemical immobilization is one of the most used for reducing the bioavailability of heavy metals. The aim is to immobilize the ions trapping them in minerals with low solubility and stable in the environment in a wide range of conditions. Synthetic or natural apatite and phosphate rock have been proved to immobilize divalent heavy metal ions such as Pb, Zn, Cd, Cu, Co, Cr, Ni, and Sb in contaminated waters and soils. The mechanisms of metal removal include ion exchange, surface complexation and dissolution/precipitation. In this study the removal of Cd, Pb, Zn, and Cu from aqueous solutions by both synthetic hydroxyapatite (HA) and natural phosphate rock (FAP) was investigated in batch conditions at 25 ± 2°C. The metals were applied both as single- or multi-metal (Cd + Pb + Zn + Cu) systems with initial concentrations from 0 to 8 mmol L-1. The removal capacity of phosphate amendments generally ranges between 50 and 99%. In the multi-metal systems competitive internal metal sorption reduced the removal capacity by 13–83% compared to the single-metal systems. The sorption of heavy metals by phosphate amendments follows the Langmuir model. Heavy metal immobilization occurs through a two-step mechanism: rapid surface complexation on the ≡POH sites followed by partial dissolution of phosphates and ion exchange with Ca resulting in the formation of heavy metal-containing phosphates.The sorption of Cu on HA was further investigated by means of the results of a combined structural simulation and EXAFS analysis. The EXAFS results suggest that the heavy metal is present in the Cu+2 form. The structural experimental and theoretical analysis shows that Cu is bond to about four O atoms at a distance of about 1.95Å. In all the studied cases the immobilization site of Cu is the same. The fixation of Cu occurs in the surface sites of hydroxyapatite whereas the sorption in the Ca sites in the inner part of the structure is unlikely.The effectiveness of phosphate treatment for Cd, Pb, Zn, and Cu immobilization in mine waste soils from sulfide mine areas (tailing dumps, ore stocking areas, streams, etc.) in Tuscany and Sardinia (Italy) was examined in batch conditions. Application of HA and FAP effectively reduced the heavy metals water solubility generally by about 84 to 99%. Between the two amendments evaluated, HA was slightly more effective with respect to FAP in immobilizing heavy metals. Although the lower effectiveness of phosphate rock, its application to reduce metal solubility in contaminated soils may minimize soil acidification and potential risk of eutrophication associated with the application of highly soluble phosphate sources