This work examines the rates of bioremediation during a landfarming process. A field study was performed using three types of soil, which were contaminated with two different hydrocarbon concentrations: 20,000 and 50,000 ppm of total petroleum hydrocarbons (TPH). They were subjected to landfarming under the action of different treatments, based on the provision of irrigation, aeration by rototilling, fertilizer, and surfactant. The biodegradation of TPH, considering concentration and families of hydrocarbon compounds (including polycyclic aromatic hydrocarbons, PAHs), was precisely measured for a period of 486 days. The results show how biodegradation rates depend on soil texture, initial contamination level, and type of amendment. Thus, the combination of fertilizer, irrigation, and aeration was the best treatment for treating the soil contaminated with 20,000 ppm of TPH (TPH final concentrations were reduced to a range of 49 to 62% depending on the soil texture). In the case of parcels contaminated with 50,000 ppm of TPH, the most effective treatment combined the supply of fertilizer, surfactant, irrigation, and aeration (TPH final concentrations were reduced to a range of 47 to 63%, depending on the soil texture). The best biodegradation results are obtained for soils with coarser textures and using the treatment with fertilizer, irrigation, and aeration. In addition, the application of surfactant did not imply a significant improvement in the level of biodegradation of hydrocarbons in soil contaminated with 20,000 ppm of TPH, whereas in soils contaminated with 50,000 ppm of TPH, it played a leading role.
A preliminary study was carried out in Rome (Italy) to assess the potential role of atmospheric deposition in trace element contamination in urban vegetable gardens relative to human health risk from crop consumption.
Materials and methods
Two sites were selected on the basis of previously known contamination issues. Atmospheric deposition, parent material, soils properties affecting trace element mobility, and various anthropogenic inputs were considered. Soil samples were taken at depth from two points in each garden, within 5 cm of sampled crops. Inputs and crops were sampled and analysed for As and Pb content. A rain and dust gauge was set up in each garden for the duration of 93 days (late spring to late summer) for atmospheric deposition sampling.
Results and discussion
Atmospheric deposition influx was high at both sites (2.22 and 2.32 As and 2.67 and 3.42 Pb μg m?3 day?1). Soil pH was between 6.70 and 7.57 and texture varied from loamy sand to clay loam (3.4 to 31.9 % clay content). CEC ranged between 21.6 and 54.2 meq/100 g within rooting depth, rising almost commensurately with soil organic carbon (SOC) content (1.87–8.37 %). Somewhat high total soil Pb content (80.8–522.7 ppm) contrasted with negligible exchangeability and crop content (<0.01 ppm). Total soil As (17.0–32.0 ppm) corresponded with exchangeable and crop As for one site in one of the gardens. Leaves evinced high As accumulation levels (16.0–41.2 ppm) in all crops. High amounts of atmospheric Pb combined with negligible amounts of extractable Pb and Pb plant tissue content point to particulate inhalation and ingestion as a main health threat in the case of Pb. In contrast, food intake seems to be of greater concern relative to high As contamination. Greater soil As solubility may be explanatory, but the mostly low amounts of extractable As and the high atmospheric As suggest an airborne route being playing an important role.
Conclusions
Preliminary results suggest that research on trace element contamination in urban gardens should consider atmospheric deposition as a major contributing source.
Evaluate the efficiency of Populus alba clone Villafranca in the uptake and translocation of Zn from contaminated soils.
Materials and methods
The effects of 48 days of zinc treatment (Znt) on the growth and the photosynthetic activities of P. alba L. clone Villafranca were studied using ZnSO4 (375 ppm per unit of soil dry weight) added in sand and peat moss substrate at the beginning of the treatment (T0) and again after 30 days (T1) in order to reach a target Zn concentration of 375 ppm at T0 and 750 ppm at T1 per unit of soil dry weight.
Results and discussion
Zn uptake in the different organs was analyzed after 30 (T1) and 48 days (T2) from the beginning of treatment, showing the following order: root ? leaves ≥ woody cutting = stem. The leaf area increased by 12 % in comparison to control plants at the end of second treatment (48 days). Cutting radial growth showed a high synchronicity in the growth rate fluctuation among control and Znt plants, but a higher increase in radial diameter of Znt cutting was observed starting from day 38 (after 8 days of second Znt) reaching after 48 days 38 % higher than control plants.
Conclusions
Although our data of leaf Zn concentration were in the range usually reported as toxic for plants, Villafranca clone in Znt substrate were unaffected in terms of net CO2 assimilation and stomatal conductance to water vapor.
Triclosan (TCS, 5-chloro-2-(2,4-dichlorophenoxy) phenol) an antimicrobial compound used in a range of household products, is an emerging hydrophobic organic contaminant, that may be incorporated into soil through the application of biosolids. The present study assessed the bioavailable fraction of TCS in a soil-biosolid system using wheat (Triticum aestivum) plant assays and a predictive extraction method using a solution of hydroxypropyl-β-cyclodextrin (HPCD) to determine if it was a reliable surrogate for this bioassay.
Materials and methods
Three soils were obtained from the central region of Chile (Cuesta Vieja, Polpaico, and Taqueral). Biosolid was obtained from a regional wastewater treatment plant. The soils were amended with biosolids at different rates (30, 60, 90, and 200 Mg ha-1). The TCS concentration was determined in biosolids, soil, and plant samples via gas chromatography coupled with mass spectrometry (GC-MS).
Results and discussion
The total TCS concentration in the biosolids was 5.45 mg kg-1. The results of the TCS extraction from the wheat plants (roots and shoots) indicated that TCS was primarily found in the roots. TCS uptake by the plant varied based on soil properties. The predictive capability of the HPCD extraction was assessed using a simple linear correlation test for TCS concentration in wheat plants.
Conclusions
The study yielded a linear relationship, which demonstrated the validity of the chemical method as a biosimulation technique.
The strong role that soil polyphenols play in soil organic matter (SOM) formation affects soil carbon sequestration. N deposition, which comes from man-made fertilizer, influences plant growth and soil biochemical properties therefore greatly regulates soil polyphenol metabolism. The objective of this experiment was to understand the effect of fertilizer form and rate on soil polyphenol dynamics as well as to understand the potential relationship between soil phenols and C accumulation.
Materials and methods
Urea, rapeseed cake, and chicken manure, respectively, referred as N, B, and F in the text, were applied at three rates (low N, medium N, and high N, referred as 1, 2, and 3 in the text, respectively); plots without fertilization were set as control (CK, for short). Seasonal dynamics of soil total polyphenol (Tp) and bound polyphenol (Bp) concentrations were monitored. Polyphenol oxidase (PPO), peroxidase (POD), and soil fluorescein diacetate (FDA) hydrolysis activities, all factors relevant to polyphenol metabolism, were measured simultaneously. The relationship between soil polyphenols and soil C concentration was also determined.
Results and discussion
N-fertilization altered the seasonal change pattern and the accumulation level of soil Tp and Bp, which possibly resulted from the enhancement of soil microbial activities and the change of soil nutrient status. Positive linear correlation was observed between soil Tp and TC (total C) contents, which means fertilization could influence C accumulation through affecting the metabolism of soil polyphenols. Soil chemical characteristics and enzyme activities that relate to soil polyphenol metabolism were influenced by fertilization as well. Mitigated TC increment was observed in most fertilization treatments mainly due to the increased SOM decomposition rate.
Conclusions
Our findings reveal the important role of soil phenols played in C accumulation in a tea plantation due to the significant, positive linear relationship between soil Tp and TC. Long-term studies, combined with soil microorganism community structure, soil humification, and tea leaf litter decomposition experiments, are necessary for fully understanding the role that polyphenols play in soil C cycle.
The synthetic soil based bioremediation approach as reasonable and sustainable practice at the farming level where desired bioremediation could be established at lower cost.
Materials and methods
Metal-tolerant bacteria from different environmental field samples, (a) a municipal dump site, (b) an agricultural field and (c) sludge of electro-plating industries, were screened and characterized. Bioremediation of metal contaminants through isolated bacteria was compared under two different conditions, synthetic soil and basic minimal media containing copper, cobalt and nickel.
Results and discussion
The pollutants arising from industrial effluents are imparting a huge negative impact on agricultural land. Microbes are predominant in heavy metal-contaminated sites, which signifies as a potential opportunity for the researchers towards bioremediation. Three bacterial species showed high metal tolerance; 16S ribosomal DNA (rDNA) analysis revealed that the organisms were Proteus vulgaris strain, Stenotrophomonas sp. and Bacillus thuringiensis. Percentage removal of metals was also analysed under different concentrations and pH.
Conclusions
The current tested methods are helpful in streamlining the natural compliance of fragile elements and its uptake into the microbial system under in vitro and in situ conditions.
Data management strategies of pyrolysis results and NMR acquisition modes were examined in humic acids (HAs) from control soils and fire-affected soils. The information supplied by dipolar dephasing (DD) 13C NMR spectroscopy and Curie-point pyrolysis were used to assess chemical structures hardly recognizable and measurable, or of unclear interpretation, when using 13C NMR under standard acquisition pulses (cross-polarization/magic angle spinning, CPMAS).
Materials and methods
The HAs were isolated from two forest soils under Pinus halepensis and Pinus sylvestris in control and burned sites affected by medium or severe-intensity wildfires. For NMR analyses, during DD acquisition conditions, a 180° 13C pulse was inserted to minimize phase shifts. Curie-Point pyrolysis was carried out at 510 °C for 5 s, and the pyrolysis fragments were analyzed by GC/MS. The total abundances of the major pyrolysis products were compared by an update of the classical Van Krevelen’s graphical-statistical approach, i.e., as surface density values in the space defined by the compound-specific H/C and O/C atomic ratios.
Results and discussion
The DD 13C NMR experiments displayed significant differences in the HA spectral profiles as regards to the standard CPMAS 13C NMR acquisition conditions, mainly in the chemical shift region of alkyl structures as well as for tannin- or carbohydrate-like O-alkyl structures. In fact, the comparison between DD and CPMAS solid-state NMR suggested shortening of alkyl chains and generation of carbohydrate-derived, unsaturated structures—viz. furans—which adds to the aromatic domain. Pyrolytic results showed fire-induced specific changes in HAs chemical structure and its molecular diversity. The changes were evident in the location and sizes of the different clusters of pyrolysis compounds defined by their atomic ratios.
Conclusions
The DD 13C NMR provided specific information on the fate of aliphatic structures and the origin of unsaturated HA structures, which could be helpful in differentiating “inherited” from “pyrogenic” aromatic structures. This is further confirmed by the analysis of the molecular assemblages of pyrolytic products, which showed accumulation of condensed polyaromatic domains in the HAs after the high-intensity fire, accompanied by a recalcitrant alkyl hydrocarbon domain. Medium-intensity fire led to aromaticity increase due to a selective accumulation of lignin-derived phenols concomitant to the depletion of aliphatic hydrocarbon constituents.
The present paper concerns the distribution and mobility of heavy metals (Cu, Pb, Zn and Fe) in the soils of some abandoned mine sites in Italy and their transfer to wild flora.
Materials and methods
Soils and plants were sampled from mixed sulphide mine dumps in different parts of Italy, and the concentrations of heavy metals were determined.
Results and discussion
The phytoremediation ability of Salix species (Salix eleagnos, Salix purpurea and Salix caprea), Taraxacum officinale and P?lantago major for heavy metals and, in particular, zinc was estimated. The results showed that soils affected by mining activities presented total Zn, Cu, Pb and Fe concentrations above the internationally recommended permissible limits. A highly significant correlation occurred between metal concentrations in soils.
Conclusions
The obtained results confirmed the environmental effects of mine waste; exploring wild flora ability to absorb metals, besides metal exploitation, proved a useful tool for planning possible remediation projects.
