16S rRNA Gene-Based Profiling of the Microbial Community in an Acid Mine Drainage Fe Precipitate at Libiola Mine (Liguria, Italy)

Acid mine drainage (AMD) is a common environmental problem in many sulphide mines worldwide, and it is widely accepted that the microbial community plays a major role in keeping the process of acid generation active. The aim of this work is to describe, for the first time, the microbial community thriving in goethite and jarosite Fe precipitates from the AMD of the Libiola mine. The observed association is dominated by Proteobacteria (>50%), followed by Bacteroidetes (22.75%), Actinobacteria (7.13%), Acidobacteria (5.79%), Firmicutes (2.56%), and Nitrospirae (1.88%). Primary producers seem to be limited to macroalgae, with chemiolithotrophic strains being almost absent. A phylogenetic analysis of bacterial sequences highlighted the presence of heterotrophic bacteria, including genera actively involved in the AMD Fe cycle and genera (such as Cytophaga and Flavobacterium) that are able to reduce cellulose. The Fe precipitates constitute a microaerobic and complex environment in which many ecological niches are present, as proved by the wide range of bacterial species observed. This study is the first attempt to quantitatively characterize the microbial community of the studied area and constitutes a starting point to learn more about the microorganisms thriving in the AMD of the Libiola mine, as well as their potential applications

Zinc tolerance and accumulation capability by Penicillium strains isolated from Neutral Mine Drainage (NDM) colloidal precipitates

Zinc, at low concentration, is one of the oligo elements essential for life. As well as many others metals, high environmental Zn concentrations are toxic for several organisms and can compromise their lifecycle. Neutral (or alkaline) Mine Drainage (NMD) are metal-rich solutions with near-neutral pH values, often generated by weathering of sulphide minerals (mainly Zn and Pb sulphides), circulating in mining areas. As this phenomenon favours the dispersion of metals and contributes to the rising of concentration of toxic elements in the groundwaters, NMD threatens the surrounding environment. The effectiveness of autochthonous fungal strains in bioremediation process of ecotoxic metal is today well founded. We investigated the Zn tolerance and accumulation capability of four Penicillium strains (two P. janthinellum, one P. olsonii, and one P. waksmanii) isolated from an NMD environment. The experimental results showed a positive growth response of all strains at 750 ppm of Zn, while only two strains (P. olsonii and P. waksmanii) were able to grow at 1500 ppm of Zn. Further tests showed a bioaccumulation capability by P. olsonii strains up to 8600 ppm. These data, reporting the bioaccumulation capabilities of fungal species that have not been studied previously, are a further confirmation of the potential usefulness of autochthonous microfungi in bioremediation of heavy metals, and highlight the need of increase the number of tested strains.Lo zinco, in basse concentrazioni, è uno degli oligoelementi essenziali per la vita. Così come molti altri metalli, alte concentrazioni di Zn nell’ambiente risultano tossiche per diversi organismi, compromettendone talvolta il ciclo vitale. Il drenaggio Neutro (o alcalino) di miniera (NMD), caratterizzato da alte concentrazioni di metalli e valori di pH prossimi alla neutralità, è un particolare processo generato dall'alterazione di minerali, spesso di solfuri, (in molti casi Zn e Pb), in ambiente di miniera. Questo fenomeno favorisce la dispersione dei metalli e contribuisce all'aumento della concentrazione di questi elementi tossici nelle acque circolanti minacciando l'ambiente circostante. Oggi è ormai assodata l'efficacia dei funghi (in particolare di ceppi autoctoni) nei processi di biorimedio di metalli ecotossici. Nel nostro lavoro abbiamo studiato la capacità di tolleranza e accumulo di Zn in quattro ceppi di Penicillium (due P. janthinellum, un P. olsonii e un P. waksmanii) isolati da un ambiente soggetto a NMD. I risultati ottenuti hanno mostrato una risposta di crescita positiva di tutti i ceppi in presenza di 750 ppm di Zn, mentre solo due ceppi (P. olsonii e P. waksmanii) sono stati in grado di crescere a concentrazioni pari a 1500 ppm di Zn. Inoltre, ulteriori prove hanno dimostrato una capacità di bioaccumulo del ceppo di P. olsonii fino a 8600 ppm. Questi dati, evidenziando la capacità di bioaccumulo di specie poco studiate in precedenza, sono un'ulteriore conferma della potenziale utilità dei microfunghi autoctoni nel biorisanamento di terreni contenenti metalli pesanti

Benthic diatom community response to metal contamination from an abandoned Cu mine: Case study of the Gromolo Torrent (Italy)

Environmental contamination has become a global problem of increasing intensity due to the exponential growth of industrialization. One main debated issue is the metal contamination of rivers receiving Acid Mine Drainage (AMD) from active/abandoned mines. In order to assess the quality of lotic systems, diatoms are commonly used, as their assemblage modifies on the basis of changes in environmental parameters. Benthic diatom changes were analyzed along the metal-impacted Gromolo Torrent (Liguria, NW Italy) with the aim of understanding the effects of input from the abandoned Libiola Cu mine. The results support the hypothesis that metals from AMD lead to massive changes in diatoms, resulting in low biological diversity and in a shift of dominance, passing from the genera Cymbella and Cocconeis to more tolerant and opportunistic species, such as Achnanthidium minutissimum and Fragilaria rumpens. The high concentrations of labile metals, measured through Diffusion Gradients in Thin-films (DGT) immediately downstream of the two AMD inputs in the torrent, corresponded to a sudden decrease in the presence of diatoms, indicating the possible reaching of acute toxic levels. In particular, A. minutissimum dominated the mining area and was positively correlated with Cu and Zn; whereas F. rumpens bloomed downstream of this area, where the metal content was diluted, and was positively correlated with As and Pb. Finally, an important abundance of Nitzschia palea and teratological forms of A. minutissimum and F. rumpens were observed downstream from the mine, indicating that metals may have an important impact on diatoms up to the torrent mouth

Environmental complexity of a port: Evidence from circulation of the water masses, and composition and contamination of bottom sediments

Ports are complex environments due to their complicated geometry (quays, channels, and piers), the presence of human activities (vessel traffic, shipyards, industries, and discharges), and natural factors (stream and torrent inputs, sea action, and currents).Taking these factors into consideration, we have examined the marine environment of a port from the point of view of the circulation of the water masses, hydrological characteristics, distribution of the sediment grain-size, mineralogical characteristics, and metal concentrations of the bottom sediments. Our results show that, in the case of the Port of Genoa (north-western Italy), the impact of human activities (such as a coal power-plant, oil depots, shipyards, dredging of the bottom sediments, etc.), natural processes (such as currents, fresh water and sediment inputs from the torrents), and the morphology of the basin, are important factors in the sediment, water, and metal distributions that have given rise to a complex environment

Marine sediment contamination and dynamics at the mouth of a contaminated torrent: The case of the Gromolo Torrent (Sestri Levante, north-western Italy)

none6noIn this study we have examined the currents and hydrological characteristics of the water column off the mouth of the Gromolo Torrent (north-western Italy) in relation to the grain-size, mineralogical characteristics and metal distribution in the marine sediment sampled. Our purpose was to quantify and map the contamination that was carried out to sea from the abandoned Libiola Fe-Cu sulphide mine that has heavily impacted the torrent. Our results show high concentrations of Cu and Zn, and relatively high concentrations of Cd and Ni inside the bay into which the Gromolo Torrent flows. However, high concentrations of As, Cr, Hg, Mn, Pb, and V found in the northern and/or eastern parts of the study area originated from other sources. The subdivision of study stations in terms of metal and mineral contents in the bottom sediments highlighted the clear influence of the currents on their dispersion and distribution in the area.noneCapello, M.*; Cutroneo, L.; Consani, S.; Dinelli, E.; Vagge, G.; Carbone, C.Capello, M.*; Cutroneo, L.; Consani, S.; Dinelli, E.; Vagge, G.; Carbone, C

Assessment of metal distribution in different Fe precipitates related to Acid Mine Drainage through two sequential extraction procedures

In the last decades, the contamination by metals from mining areas, especially that due to Acid Mine Drainage (AMD), has become a hot topic for the scientific community. The precipitation of secondary minerals related to AMD is the most important natural method of scavenging elements from such solutions. These minerals are a dynamic system, in which mineralogical and chemical transformations could be triggered by sudden changes of the chemical-physical conditions. Therefore, minerals related to AMD could merely act as temporary sink for inorganic pollutants, and understanding the stability over time of metals in these phases is very important. This paper aims to evaluate metal lability in 4 different natural precipitates related to AMD by using two different sequential extraction procedures. Two samples were composed of goethite and jarosite, one sample of schwertmannite, and the last sample of an amorphous Fe phase. The results obtained allowed concluding that the amorphous Fe phase was able to scavenge a high amount of metals from the flowing solutions, but it was also the most reactive compound. Therefore, this phase represented a major threat for the environment. The results obtained showed that the two sequential extraction procedures were not able to dissolve completely the Fe phases, probably because the sample-extractant volume ratio and the time and nature of contact was not optimised for this kind of samples. For this reason, the results of sequential extraction procedures on AMD impacted materials could be unreliable in case of Fe oxyhydroxide very rich samples

Environmental implications of metal mobility in marine sediments receiving input from a torrent affected by mine discharge

Acid Mine Drainage (AMD) is one of the most important sources of pollution in fluvial systems and can enrich rivers in dissolved and suspended metals of environmental concern. Colloidal particles may favour the transport of metals to the sea, where metals can be accumulated in bottom sediments. The aim of this paper was to evaluate the mobility of metals in the “Baia delle Favole” bottom sediments (Sestri Levante, Italy), which receive the input of the AMD impacted Gromolo Torrent, using chemical speciation (BCR sequential extraction). Basing on the Risk Assessment Code (RAC), our results showed a systematic and widespread high risk classification for Mn, whereas a medium risk is associated to Co, Cu, and Zn in the sediments collected near the mouth of the Gromolo Torrent. Moreover, in these sediments the occurrence of Fe oxyhydroxides has been observed, reflecting an increase of metals in the reducible fraction obtained with BCR