Silvia Rita Stazi

Copper distribution and hydrolase activities in a contaminated soil amended with dolomitic limestone and compost.

Chemical fractionation of copper in bulk soil and its distribution in the particle-size fractions were analyzed in a Cu-contaminated soil (674 ± 122 μg Cu g(-1), up to 1900 μg Cu g(-1) in the clay fraction) sampled from a wood preservation site left untreated and subsequently treated with dolomitic limestone (DL, 0.2% w/w) and compost (CM, 5% w/w), singly and in combination (DL+CM). Soil enzymatic activities of leucine aminopeptidase, cellulase, N-acetyl-β-glucosaminidase, arylsulfatase, β-glucosidase, acetate esterase, butyric esterase, and acid phosphatase were determined. Chemical speciation showed that Cu was mostly present in the acid-soluble and reducible fractions in both untreated and treated soils, whereas treatments with DL and CM reduced the soluble and exchangeable Cu fractions, due to Cu precipitation and complexation, and increased Cu bound to soil organic matter. Analysis of the particle-size fractions showed that more than 80% of Cu was in the silt and clay fractions and that treatment with CM increased the concentration of Cu in the sand size fractions. Soil treatment with DL and CM, singly or in combination, increased hydrolase activities, mainly in the clay fraction, with the largest positive effects on N-acetyl-β-glucosaminidase, leucine aminopeptidase, and β-glucosidase activities. Overall, results confirm that (1) Cu in contaminated soils is mainly bound to the silt-clay fraction, (2) CM additions change its allocation in the particle-size fractions, and (3) treatments with DL and CM singly and in combination reduce Cu solubility and its inhibitory effects on soil enzyme activities.

Mobility and distribution of arsenic in contaminated mine soils and its effects on the microbial pool

Three soils, coming from a former mining site and characterized by a different degree of pollution, were analysed in terms of Arsenic (As) content, using three different analytical approaches, and its distribution in various soil fractions. The effect of As on soil microbial biomass (size, respiration and microbial quotients) was also analysed. Total arsenic concentration between soil fractions was significantly different and ranged from 189 to 4357mgkg(-1), indicating a high level of pollution. Soil sequential fractioning showed that more than 60 percent of total As was bound to Fe-Al oxides, suggesting a minor availability and environmental risk regardless the total concentration of As in the sample. On the contrary, water soluble As fraction showed a significant difference among the three samples. The largest water soluble As concentration was found in the sample with intermediate total As amount. As far as microbial biomass is concerned, it was found that bioavailable As negatively impacted microbial metabolism in terms of basal and cumulative respiration, and microbial quotients, suggesting a strong selection within microbial pool.

Immobilized Inocula of White-Rot Fungi Accelerate both Detoxification and Organic Matter Transformation in Two-Phase Dry Olive-Mill Residue

The potential use for agronomic purposes of dry olive-mill residue (DOR), solid waste from the olive oil two-phase extraction process, might be impaired by its phytotoxicity. Although fungal treatments can detoxify DOR, long times are required for these processes. The objective of this study was to assess whether the addition of immobilized fungal inocula to DOR might improve colonization rates, thus reducing the time necessary for its detoxification and bioconversion. Inocula of Panus tigrinus CBS 577.79 and Phlebia sp. DABAC 9 immobilized on either chopped maize stalks or polyurethane sponge (PS) led to higher removals of both phenols and phytotoxicity from DOR than free inocula after 4 weeks of incubation. Best dephenolization (85%) was with PS-immobilized Phlebia sp., the use of which reduced germinability inhibition of Lepidium sativum and Lactuca sativa by 80 and 71.4%, respectively. Regardless of the type of inoculant, a low degree of humification was obtained.

Hyperspectral Visible and Near-Infrared Determination of Copper Concentration in Agricultural Polluted Soils

The objective of this research was to develop a hyperspectral imaging system for estimating copper concentration in soils as an alternative to standard chemical analyses and to evaluate the analytical accuracy of the system using the visible–near-infrared and near-infrared regions. Hyperspectral imaging is a complex technology providing elevated information content. This work was carried out on air-dried <2-mm soil fraction contaminated by adding 20 mL of copper sulfate at concentrations ranging from 0 to 1000 mg of copper per kg of soil. The samples were scanned in random order and with orientation using visible–near-infrared and near-infrared spectrophotometers. A range of partial least squares regression models derived from the spectral arrays were tested on their ability to predict copper concentration. Significant correlations between predicted and known chemical concentrations were achieved with a correlation coefficient of 0.93 for the visible–near-infrared and 0.77 for the near infrared.

Hyperspectral Visible–Near Infrared Determination of Arsenic Concentration in Soil

The development of rapid techniques, such as hyperspectral spectrophotometry, for investigating arsenic (As) soil contamination could be of great value with respect to conventional methods. This study was conducted to detect As concentrations in artificially polluted soils (from 25 to 1045 mg kg−1) through hyperspectral visible–near infrared spectrophotometry and to compare two multivariate statistical regression analyses: partial least squares and support vector machines. The correlation coefficient r is greater in the partial least squares in both model (0.93%) and test (0.87%) with respect to support vector machines (0.88% for the model and 0.82% for the test). The most important model variables extracted from the variable importance in projection scores resulted the absorption peaks at 580, 660, 715, and 780 nm. Bands in the visible spectra are not directly associated to As, but the metalloid can interact with the main spectrally active components of soil permitting to multivariate statistical models to screen As concentrations.

Arsenic uptake and partitioning in grafted tomato plants

Arsenic is a toxic and cancerogenic metalloid that poses a threat to food crop consumption. Previous studies have shown that grafting vegetables onto certain rootstocks may restrict the uptake of some toxic metals, such as cadmium, lead, and so on, but these studies did not investigate the uptake of arsenic. The aim of this work was to determine the following: i) if grafting can influence and reduce arsenic translocation in the root and/or aerial organs; ii) how tomato plants irrigated with arsenic-enriched nutrient solution (100 μg·L-1) accumulate this metalloid; and iii) if arsenic poses a potential risk to fruit quality. We found that differences in plant growth and the qualitative traits of fruits were mainly related to the adopted rootstock rather than to the addition of arsenic. Grafting influenced metalloid accumulation in roots and its translocation from roots to shoots and fruits. Tomato plants accumulated arsenic in their roots, and only a small portion was translocated to shoots and fruits, making the risk for human consumption negligible. Therefore, the uptake of this toxic element and its translocation are influenced by the rootstock utilized.

A Multi-biological Assay Approach to Assess Microbial Diversity in Arsenic (As) Contaminated Soils

ABSTRACT Microbial genetic, structural and functional diversity was assessed in response to arsenic (As) pollution in a former gold mine soil. Ester-linked fatty acid methyl ester (EL-FAME), quantitative PCR (qPCR), denaturating gradient gel electrophoresis (DGGE), enzyme activities and MicroResp techniques were used. Multivariate analysis showed that As bioavailability in soil was an important driver affecting microbial diversity. Microbial biomass assessed by EL-FAMEs and qPCR generally decreased under higher bioavailable As, as well as enzyme activities and C substrate utilization. Conversely, actinomycetes and fungal biomass increased along with total As content suggesting the selection of more resistant species.

Fungal Community Structure and As-Resistant Fungi in a Decommissioned Gold Mine Site

Although large quantities of heavy metal laden wastes are released in an uncontrolled manner by gold mining activities with ensuing contamination of the surrounding areas, there is scant information on the mycobiota of gold-mine sites. Thus, the present study was aimed to describe the fungal community structure in three differently As- and Hg-polluted soils collected from the Pestarena decommissioned site by using Illumina® metabarcoding. Fungal richness was found to increase as the contamination level increased while biodiversity was not related to the concentrations of inorganic toxicants. Within the phylum Zygomigota which, irrespective of the contamination level, was predominant in all the soils under study, the most abundant genera were Mucor and Mortierella. The relative abundances of Basidiomycota, instead, tended to raise as the contamination increased; within this phylum the most abundant genera were Cryptococcus and Pseudotomentella. The abundance of Ascomycota, ranging from about 8 to 21%, was not related to the contamination level. The relative abundances of those genera (i.e., Penicillium, Trichoderma, and Chaetomium), the cultivable isolates of which exhibited significant As-resistance, were lower than the set threshold (0.5%). Mass balances obtained from As-exposure experiments with these isolates showed that the main mechanisms involved in counteracting the toxicant were accumulation and, above all, volatilization, the respective extents of which ranged from 0.6 to 5.9% and from 6.4 to 31.2% in dependence of the isolate.

Arsenic in Soil: Availability and Interactions with Soil Microorganisms

Arsenic (As) is a naturally occurring element in the Earth’s crust, commonly found as a trace constituent of rocks, soils, sediments, water, and biota. However natural and anthropogenic processes can increase its content in groundwater, soils, and sediments to toxic levels. Concentration of total As in soils does not necessarily represent its biological availability or potential toxicity measures which are much more important for assessing possible environmental impacts. Soil microorganisms may be involved in As pollution issues in an active and passive way at the same time. They can induce environmental As bioavailability due to chemical–biochemical processes, microbial mediated, that favor its release in water-soluble forms or more mobile (As III). Conversely, soil microbial biomass can be deeply affected in its size, functions, and diversity by the concentration of this ion in soil solution and impact in this way soil functioning.

Influence of organic management on As bioavailability: Soil quality and tomato As uptake

The research studied the effects of organic vs. conventional management of soil quality and tomato yield quality, cultivated in a geogenic arsenic contaminated soil. The chemical and biochemical properties were analyzed to evaluate soil quality, arsenic mobility and its phyto-availability, as well as arsenic accumulation in the tomato plant tissues and if tomatoes cultivated in arsenic rich soil represents a risk for human health. A general improvement of tomato growth and soil quality was observed in the organic management, where soil organic carbon increased from 1.24 to 1.48% and total nitrogen content. The arsenic content of the soil in the organic management increased from 57.0 to 65.3 mg kg-1, probably due to a greater content of organic matter which permitted the soil to retain the arsenic naturally present in irrigation water. An increase of bioavailable arsenic was observed in the conventional management compared to the organic one (7.05 vs 6.18 mg kg-1). The bioavailable form of metalloid may affect soil microbial community structure assessed using El-FAME analysis. The increase of the total arsenic concentration in the organic management did not represent a stress factor for soil microbial biomass carbon (Cmic), which was higher in the organic management than in the conventional one (267 vs. 132 μg Cmic g-1). Even if the organic management caused an increase of total arsenic concentration in the soil due to the enhanced organic matter content, retaining arsenic from irrigation water, this management mitigates the arsenic uptake by tomato plants reducing the mobility of the metalloid.