Induced development of oxytetracycline tolerance in bacterial communities from soil amended with well-aged cow manure.

The use of animal manure as organic fertilizer is a common agricultural practice that can improve soil health and crop yield. However, antibiotics and their metabolites are often present in animal manure and, hence, in manure-amended soil. The aim of this study was to assess the induced development of oxytetracycline (OTC) tolerance in soil bacterial communities as a result of the addition of OTC to soil amended with well-aged cow manure. To this purpose, soil amended with well-aged cow manure was repeatedly - three times - spiked with different OTC concentrations (0, 2, 20, 60, 150, and 500 mg OTC kg-1 dry weight soil, each time) according to a pollution-induced community tolerance (PICT) assay. The PICT detection phase was conducted in Biolog EcoPlatesTM in the presence of the following OTC concentration gradient in the wells: 0, 5, 20, 40, 60, and 100 mg L-1. For all treatments, the application of OTC in the PICT selection phase resulted in lower values of bacterial metabolic activity (i.e., lower values of average well color development) in the PICT detection phase. A significant increase in OTC tolerance was observed in soil bacterial communities that had been exposed three times to ≥ 20 mg OTC kg-1 DW soil during the PICT selection phase. In general, higher levels of OTC exposure during the PICT selection phase resulted in bacterial tolerance to higher OTC concentrations during the PICT detection phase, pointing to a dose-dependent induced tolerance. It is important to (i) rationalize the amount of antibiotics administered to livestock, and (ii) treat properly the antibiotic-containing manure before its application to agricultural soil as fertilizer.

Reduction of the resistome risk from cow slurry and manure microbiomes to soil and vegetable microbiomes.

In cow farms, the interaction between animal and environmental microbiomes creates hotspots for antibiotic resistance dissemination. A shotgun metagenomic approach was used to survey the resistome risk in five dairy cow farms. To this purpose, 10 environmental compartments were sampled: 3 of them linked to productive cows (fresh slurry, stored slurry, slurry-amended pasture soil); 6 of them to non-productive heifers and dry cows (faeces, fresh manure, aged manure, aged manure-amended orchard soil, vegetables-lettuces and grazed soil); and, finally, unamended control soil. The resistome risk was assessed using MetaCompare, a computational pipeline which scores the resistome risk according to possible links between antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and human pathogens. The resistome risk decreased from slurry and manure microbiomes to soil and vegetable microbiomes. In total (sum of all the compartments), 18,157 ARGs were detected: 24% related to ansamycins, 21% to multidrugs, 14% to aminoglycosides, 12% to tetracyclines, 9% to ß-lactams, and 9% to macrolide-lincosamide-streptogramin B. All but two of the MGE-associated ARGs were only found in the animal dejections (not in soil or vegetable samples). Several ARGs with potential as resistome risk markers (based on their presence in hubs of co-occurrence networks and high dissemination potential) were identified. As a precautionary principle, improved management of livestock dejections is necessary to minimize the risk of antibiotic resistance.

From phytoremediation of soil contaminants to phytomanagement of ecosystem services in metal contaminated sites.

Since the emergence of phytoremediation, much research has focused on its development for (i) the removal of metals from soil and/or (ii) the reduction of metal bioavailability, mobility, and ecotoxicity in soil. Here, we review the lights and shades of the two main strategies (i.e., phytoextraction and phytostabilization) currently used for the phytoremediation of metal contaminated soils, irrespective of the level of such contamination. Both strategies face limitations to become successful at commercial scale and, then, often generate skepticism regarding their usefulness. Recent innovative approaches and paradigms are gradually establishing these phytoremediation strategies as suitable options for the management of metal contaminated soils. The combination of these phytotechnologies with a sustainable and profitable site use (a strategy called phytomanagement) grants value to the many benefits that can be obtained during the phytoremediation of metal contaminated sites, such as, for instance, the restoration of important ecosystem services, e.g. nutrient cycling, carbon storage, water flow regulation, erosion control, water purification, fertility maintenance, etc.

Early gene expression in Pseudomonas fluorescens exposed to a polymetallic solution.

The molecular response of Pseudomonas fluorescens cells exposed to a mixture of heavy metals remains largely unknown. Here, we studied the temporal changes in the early gene expression of P. fluorescens cells exposed to three doses of a polymetallic solution over two exposure times, through the application of a customized cDNA microarray. At the lowest metal dose (MD/4), we observed a repression of the Hsp70 chaperone system, MATE and MFS transporters, TonB membrane transporter and histidine kinases, together with an overexpression of metal transport (ChaC, CopC), chemotaxis and glutamine synthetase genes. At the intermediate metal dose (MD), several amino acid transporters, a response regulator (CheY), a TonB-dependent receptor and the mutT DNA repair gene were repressed; by contrast, an overexpression of genes associated with the antioxidative stress system and the transport of chelates and sulfur was observed. Finally, at the highest metal dose (4MD), a repression of genes encoding metal ion transporters, drug resistance and alginate biosynthesis was found, together with an overexpression of genes encoding antioxidative proteins, membrane transporters, ribosomal proteins, chaperones and proteases. It was concluded that P. fluorescens cells showed, over exposure time, a highly complex molecular response when exposed to a polymetallic solution, involving mechanisms related with chemotaxis, signal transmission, membrane transport, cellular redox state, and the regulation of transcription and ribosomal activity.

cDNA microarray assessment of early gene expression profiles in Escherichia coli cells exposed to a mixture of heavy metals.

Many contaminated sites are characterized by the presence of different metals, thus increasing the complexity of toxic responses in exposed organisms. Within toxicogenomics, transcriptomics can be approached through the use of microarrays aimed at producing a genetic fingerprint for the response of model organisms to the presence of chemicals. We studied temporal changes in the early gene expression profiles of Escherichia coli cells exposed to three metal doses of a polymetallic solution over three exposure times, through the application of cDNA microarray technology. In the absence of metals, many genes belonging to a variety of cellular functions were up- and down-regulated over time. At the lowest metal dose, an activation of metal-specific transporters (Cus and ZraP proteins) and a mobilization of glutathione transporters involved in metal sequestration and trafficking was observed over time; this metal dose resulted in the generation of ROS capable of stimulating the transcription of Mn-superoxide dismutase, the assembly of Fe-S clusters and the synthesis of cysteine. At the intermediate dose, an overexpression of ROS scavengers (AhpF, KatG, and YaaA) and heat shock proteins (ClpP, HslV, DnaK, and IbpAB) was observed. Finally, at the highest dose, E. coli cells showed a repression of genes related with DNA mutation correctors (MutY glycopeptidases).

Biological remediation treatments improve the health of a mixed contaminated soil before significantly reducing contaminant levels.

The remediation of mixed contaminated soil is challenging as it often requires actions to minimize metal-induced risks while degrading organic contaminants. Here, the effectiveness of different bioremediation strategies, namely, rhizoremediation with native plant species, mycoremediation with Pleurotus ostreatus spent mushroom substrate, and biostimulation with organic by-products (i.e., composted sewage sludge and spent mushroom substrate), for the recovery of a mixed contaminated soil from an abandoned gravel pit was studied. The combination of biostimulation and rhizoremediation led to the most significant increase in soil health, according to microbial indicator values. The application of composted sewage sludge led to the highest reduction in anthracene and polychlorinated biphenyls concentrations. None of the strategies managed to decrease contamination levels below regulatory limits, but they did enhance soil health. It was concluded that the biological remediation treatments improved soil functioning in a short time, before the concentration of soil contaminants was significantly reduced.

Organic amendment treatments for antimicrobial resistance and mobile element genes risk reduction in soil-crop systems.

Agricultural fertilization with organic amendments of animal origin often leads to antibiotic resistance dissemination. In this study, we evaluated the effect of different treatments (anaerobic digestion, biochar application, ozonation, zerovalent iron nanoparticle application, and spent mushroom substrate addition) on the resistome in dairy cow manure-derived amendments (slurry, manure, and compost). Anaerobic digestion and biochar application resulted in the highest reduction in antibiotic resistance gene (ARG) and mobile genetic element (MGE) gene abundance. These two treatments were applied to cow manure compost, which was then used to fertilize the soil for lettuce growth. After crop harvest, ARG and MGE gene absolute and relative abundances in the soil and lettuce samples were determined by droplet digital PCR and high-throughput qPCR, respectively. Prokaryotic diversity in cow manure-amended soils was determined using 16S rRNA metabarcoding. Compared to untreated compost, anaerobic digestion led to a 38% and 83% reduction in sul2 and intl1 absolute abundances in the soil, respectively, while biochar led to a 60% reduction in intl1 absolute abundance. No differences in lettuce gene abundances were observed among treatments. We conclude that amendment treatments can minimize the risk of antibiotic resistance in agroecosystems.

Mycoremediation with Agaricus bisporus and Pleurotus ostreatus growth substrates versus phytoremediation with Festuca rubra and Brassica sp. for the recovery of a Pb and γ-HCH contaminated soil.

Mycoremediation with mushroom growth substrates can be used for the recovery of mixed contaminated soils due to the benefits derived from the physicochemical characteristics of the substrates, the activity of extracellular enzymes secreted by the fungi, and the presence of the fungal mycelia. The objective of this work was to assess the potential of Agaricus bisporus and Pleurotus ostreatus growth substrates (inoculated mushroom substrates vs. spent mushroom substrates) for the mycoremediation of soils co-contaminated with lead and lindane (γ-HCH). We compared the efficiency of these mycoremediation strategies with the phytoremediation with Brassica spp. Or Festuca rubra plants, in terms of both reduction in contaminant levels and enhancement of soil health. An enhanced soil health was achieved as a result of the application of mycoremediation treatments, compared to phytoremediation and control (untreated) treatments. The application of P. ostreatus inoculated substrate led to the most significant reduction in γ-HCH concentration (up to 88.9% compared to corresponding controls). In the presence of inoculated mushroom substrate, P. ostreatus fruiting bodies extracted more Pb than Brassica spp. Or F. rubra plants. Mycoremediation with P. ostreatus growth substrates appears a promising strategy for the recovery of the health of soils co-contaminated with Pb and γ-HCH.

Agricultural Soils Amended With Thermally-Dried Anaerobically-Digested Sewage Sludge Showed Increased Risk of Antibiotic Resistance Dissemination.

The application of sewage sludge (SS) to agricultural soil can help meet crop nutrient requirements and enhance soil properties, while reusing an organic by-product. However, SS can be a source of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), resulting in an increased risk of antibiotic resistance dissemination. We studied the effect of the application of thermally-dried anaerobically-digested SS on (i) soil physicochemical and microbial properties, and (ii) the relative abundance of 85 ARGs and 10 MGE-genes in soil. Soil samples were taken from a variety of SS-amended agricultural fields differing in three factors: dose of application, dosage of application, and elapsed time after the last application. The relative abundance of both ARGs and MGE-genes was higher in SS-amended soils, compared to non-amended soils, particularly in those with a more recent SS application. Some physicochemical parameters (i.e., cation exchange capacity, copper concentration, phosphorus content) were positively correlated with the relative abundance of ARGs and MGE-genes. Sewage sludge application was the key factor to explain the distribution pattern of ARGs and MGE-genes. The 30 most abundant families within the soil prokaryotic community accounted for 66% of the total variation of ARG and MGE-gene relative abundances. Soil prokaryotic α-diversity was negatively correlated with the relative abundance of ARGs and MGE-genes. We concluded that agricultural soils amended with thermally-dried anaerobically-digested sewage sludge showed increased risk of antibiotic resistance dissemination.

Antibiotic Resistance in Agricultural Soil and Crops Associated to the Application of Cow Manure-Derived Amendments From Conventional and Organic Livestock Farms.

The application of organic amendments to agricultural soil can enhance crop yield, while improving the physicochemical and biological properties of the recipient soils. However, the use of manure-derived amendments as fertilizers entails environmental risks, such as the contamination of soil and crops with antibiotic residues, antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs). In order to delve into these risks, we applied dairy cow manure-derived amendments (slurry, fresh manure, aged manure), obtained from a conventional and an organic farm, to soil. Subsequently, lettuce and wheat plants were grown in the amended soils. After harvest, the abundance of 95 ARGs and MGE-genes from the amended soils and plants were determined by high-throughput qPCR. The structure of soil prokaryotic communities was determined by 16S rRNA amplicon sequencing and qPCR. The absolute abundance of ARGs and MGE-genes differed between treatments (amended vs. unamended), origins of amendment (conventional vs. organic), and types of amendment (slurry vs. fresh manure vs. aged manure). Regarding ARG-absolute abundances in the amendments themselves, higher values were usually found in slurry vs. fresh or aged manure. These abundances were generally higher in soil than in plant samples, and higher in wheat grain than in lettuce plants. Lettuce plants fertilized with conventional amendments showed higher absolute abundances of tetracycline resistance genes, compared to those amended with organic amendments. No single treatment could be identified as the best or worst treatment regarding the risk of antibiotic resistance in soil and plant samples. Within the same treatment, the resistome risk differed between the amendment, the amended soil and, finally, the crop. In other words, according to our data, the resistome risk in manure-amended crops cannot be directly inferred from the analysis of the amendments themselves. We concluded that, depending on the specific question under study, the analysis of the resistome risk should specifically focus on the amendment, the amended soil or the crop.

Impact of metal pollution and Thlaspi caerulescens growth on soil microbial communities.

Soil microorganisms drive critical functions in plant-soil systems. As such, various microbial properties have been proposed as indicators of soil functioning, making them potentially useful in evaluating the recovery of polluted soils via phytoremediation strategies. To evaluate microbial responses to metal phytoextraction using hyperaccumulators, a microcosm experiment was carried out to study the impacts of Zn and/or Cd pollution and Thlaspi caerulescens growth on key soil microbial properties: basal respiration; substrate-induced respiration (SIR); bacterial community structure as assessed by PCR-denaturing gradient gel electrophoresis (DGGE); community sizes of total bacteria, ammonia-oxidizing bacteria, and chitin-degrading bacteria as assessed by quantitative PCR (Q-PCR); and functional gene distributions as determined by functional gene arrays (GeoChip). T. caerulescens proved to be suitable for Zn and Cd phytoextraction: shoots accumulated up to 8,211 and 1,763 mg kg(-1) (dry weight [DW]) of Zn and Cd, respectively. In general, Zn pollution led to decreased levels of basal respiration and ammonia-oxidizing bacteria, while T. caerulescens growth increased the values of substrate-induced respiration (SIR) and total bacteria. In soils polluted with 1,000 mg Zn kg(-1) and 250 mg Cd kg(-1) (DW), soil bacterial community profiles and the distribution of microbial functional genes were most affected by the presence of metals. Metal-polluted and planted soils had the highest percentage of unique genes detected via the GeoChip (35%). It was possible to track microbial responses to planting with T. caerulescens and to gain insight into the effects of metal pollution on soilborne microbial communities.

Effects of liming on soil properties and plant performance of temperate mountainous grasslands.

The application of lime or liming materials to acid-soil grasslands might help mitigate soil acidity, a major constraint to forage productivity in many temperate mountainous grasslands. Nowadays, in these mountainous grasslands, it is essential to promote agricultural practices to increase forage yield and nutritive value while preserving biodiversity and agroecosystem functioning. Two different field experiments were conducted in the Gorbeia Natural Park, northern Spain: (i) one in a calcareous mountainous grassland (Arraba) and (ii) the other in a siliceous mountainous grassland (Kurtzegan) to study the effects of a single application of two liming products, i.e. 2429 kg lime (164.3% CaCO(3)) ha(-1) and 4734 kg calcareous sand (84.3% CaCO(3)) ha(-1), applied one month before the beginning of the sheep grazing season (May-October), on soil chemical (pH, organic C, total N, C/N ratio, %Al saturation, Olsen P, exchangeable K(+) and Ca(2+)) and biological parameters (dehydrogenase, beta-glucosidase, urease, acid phosphatase and arylsulphatase activity) as well as on botanical diversity (graminoids, forbs, shrubs) and forage yield and nutritive value (crude protein, modified acid detergent fibre, digestibility). Untreated control plots were also included in the experiment. Soil sampling was carried out at the end of the sheep grazing season (6 months after liming treatment), while botanical composition was determined one year after treatments application. Although no increase in soil pH was observed in Arraba, liming significantly increased dehydrogenase activity (an indicator of soil microbial activity) by 30.4 and 86.7% at Arraba and Kurtzegan site, respectively. Liming treatments significantly improved forage yield and nutritive value in Arraba but not in Kurtzegan. Furthermore, no differences in soil biological quality, evaluated using the "treated-soil quality index" as proposed in this work, were observed between treated and untreated soils, and between the two different lime treatments (lime, calcareous sand). It was concluded that, in acid-soil temperate mountainous grasslands, moderate liming treatments have no negative short-term effects either on soil quality or botanical composition, while resulting in improvements in forage yield and nutritive value under some conditions.

Keep and promote biodiversity at polluted sites under phytomanagement.

The phytomanagement concept combines a sustainable reduction of pollutant linkages at risk-assessed contaminated sites with the generation of both valuable biomass for the (bio)economy and ecosystem services. One of the potential benefits of phytomanagement is the possibility to increase biodiversity in polluted sites. However, the unique biodiversity present in some polluted sites can be severely impacted by the implementation of phytomanagement practices, even resulting in the local extinction of endemic ecotypes or species of great conservation value. Here, we highlight the importance of promoting measures to minimise the potential adverse impact of phytomanagement on biodiversity at polluted sites, as well as recommend practices to increase biodiversity at phytomanaged sites without compromising its effectiveness in terms of reduction of pollutant linkages and the generation of valuable biomass and ecosystem services.

Long-term phytomanagement with compost and a sunflower - Tobacco rotation influences the structural microbial diversity of a Cu-contaminated soil.

At a former wood preservation site contaminated with Cu, various phytomanagement options have been assessed in the last decade through physicochemical, ecotoxicological and biological assays. In a field trial at this site, phytomanagement with a crop rotation based on tobacco and sunflower, combined with the incorporation of compost and dolomitic limestone, has proved to be efficient in Cu-associated risk mitigation, ecological soil functions recovery and net gain of economic and social benefits. To demonstrate the long-term effectiveness and sustainability of phytomanagement, we assessed here the influence of this remediation option on the diversity, composition and structure of microbial communities over time, through a metabarcoding approach. After 9 years of phytomanagement, no overall effect was identified on microbial diversity; the soil amendments, notably the repeated compost application, led to shifts in soil microbial populations. This phytomanagement option induced changes in the composition of soil microbial communities, promoting the growth of microbial groups belonging to Alphaproteobacteria, many being involved in N cycling. Populations of Nitrososphaeria, which are crucial in nitrification, as well as taxa from phyla Planctomycetacia, Chloroflexi and Gemmatimonadetes, which are tolerant to metal contamination and adapted to oligotrophic soil conditions, decreased in amended phytomanaged plots. Our study provides an insight into population dynamics within soil microbial communities under long-term phytomanagement, in line with the assessment of soil ecological functions and their recovery.

Evaluation of the efficiency of a phytostabilization process with biological indicators of soil health.

A phytostabilization process that combined the addition of a synthetic (Calcinit + urea + PK14% + calcium carbonate) or organic (cow slurry) amendment with Lolium perenne L. growth was used to remediate a mine soil moderately contaminated with Zn, Pb, and Cd. The reduced toxicity caused by both amendments allowed the establishment of a healthy L. perenne vegetation cover that had a positive influence on soil properties, increasing the biomass, activity, and functional diversity of the soil microbial community. The beneficial effects of phytostabilization on soil properties were more accentuated in organically amended than in synthetically amended soils. Root-to-shoot translocation factors were smaller in amended versus control plants, indicating a reduction in the risk of metals entering the food chain through phytostabilization. The sensitivity, rapid response, and integrative character of biological indicators of soil health make them valuable tools for assessing the efficiency of metal phytostabilization processes.

Application of sewage sludge to agricultural soil increases the abundance of antibiotic resistance genes without altering the composition of prokaryotic communities.

The application of sewage sludge as soil amendment is a common agricultural practice. However, wastewater treatment plants, sewage sludge and sewage sludge-amended soils have been reported as hotspots for the appearance and dissemination of antibiotic resistance, driven, among other factors, by selection pressure exerted by co-exposure to antibiotics and heavy metals. To address this threat to environmental and human health, soil samples from a long-term (24 years) field experiment, carried out to study the impact of thermally dried and anaerobically digested sewage sludge (at different doses and frequencies of application) on agricultural soil quality, were investigated for the presence of genes encoding antibiotic resistance (ARGs) and mobile genetic elements (MGEs). Sewage sludge-induced changes in specific soil physicochemical and microbial properties, as indicators of soil quality, were also investigated. The application of sewage sludge increased the total concentration of copper and zinc in amended soils, but without affecting the bioavailability of these metals, possibly due to the high values of soil pH and organic matter content. Soil microbal quality, as reflected by the value of the Soil Quality Index, was higher in sewage sludge-amended soils. Similarly, the application of sewage sludge increased soil microbial activity and biomass, as well as the abundance of ARGs and MGE genes, posing a risk of dissemination of antibiotic resistance. In contrast, the composition of soil prokaryotic communities was not significantly altered by the application of sewage sludge. We found correlation between soil Cu and Zn concentrations and the abundance of ARGs and MGE genes. It was concluded that sewage sludge-derived amendments must be properly treated and managed if they are to be applied to agricultural soil.

The microbiota of technosols resembles that of a nearby forest soil three years after their establishment.

Technosols can be used to rehabilitate degraded land and reuse wastes. Ideally, these newly formed soils should also fulfil the main soil functions. In this study, initially, we characterized the physicochemical and microbial properties of different formulations and their ingredients (i.e., dirt from a waste recovery plant, recycled bentonite, sewage sludge). When these technosols were then used for the rehabilitation of a quarry, the evolution of such properties was monitored for three consecutive years. Physicochemical and microbial properties were compared to those of a reference soil from a nearby forest. Diversity and composition of prokaryotes and eukaryotes were determined using 16S and 18S rRNA amplicon sequencing. Three years after establishment, as much as 78.8% and 63.9% of the prokaryotic and eukaryotic orders, respectively, were shared between the technosols and the reference forest soil. Although technosols initially showed lower values of CO2 emission, compaction and functional diversity (Biolog EcoPlates™), at the end of the study these values were similar to those observed in the reference forest soil. It was concluded that the microbiota of the studied technosols resembles that of the nearby forest soil after just three years of establishment.

The impact of nanoscale zero-valent iron particles on soil microbial communities is soil dependent.

The application of nanoscale zero-valent iron particles (nZVI) for the remediation of contaminated sites is very promising. However, information concerning the ecotoxicity of nZVI on soil microbial communities and, hence, soil quality, is still scarce. We carried out a three-month experiment to evaluate the impact of the application of different concentrations of nZVI (from 1 to 20 mg g DW soil-1) on soil microbial properties in a clay-loam versus a sandy-loam soil. Data on microbial biomass (total bacteria and fungi by qPCR, microbial biomass carbon), activity (ß-glucosidase, arylsulphatase and urease activities), and functional (Biolog Ecoplates™) and structural (ARISA, 16S rRNA amplicon sequencing) diversity evidenced that the sandy-loam soil was more vulnerable to the presence of nZVI than the clay-loam soil. In the sandy-loam soil, arylsulphatase activity and bacterial abundance, richness and diversity were susceptible to the presence of nZVI. The high content of clay and organic matter present in the clay-loam soil may explain the observed negligible effects of nZVI on soil microbial properties. It was concluded that the impact of nZVI on soil microbial communities and, hence, soil quality, is soil dependent.

Effects of chelates on plants and soil microbial community: comparison of EDTA and EDDS for lead phytoextraction.

Most studies on chelate-induced phytoextraction have focused on EDTA-mediated Pb phytoextraction. But EDTA and the formed EDTA-Pb complexes have low biodegradability and high solubility in soil, resulting in an elevated risk of adverse environmental effects. EDDS is an easily biodegradable chelating agent that has recently been proposed as an environmentally sound alternative to EDTA. Consequently, a greenhouse experiment, using a completely randomized factorial design with four replications, was carried out to compare the potential of EDTA and EDDS for chelate-induced Pb phytoextraction with Cynara cardunculus, as well as to investigate the toxicity of these two chelates to both cardoon plants and soil microorganisms. The effects of chelate addition on soil microbial communities were studied through the determination of a variety of biological indicators of soil quality such as soil enzyme activities, basal and substrate-induced respiration, potentially mineralizable nitrogen, and community level physiological profiles. EDTA was much more efficient than EDDS for the enhancement of root Pb uptake and root-to-shoot Pb translocation. In a soil polluted with 5000 mg Pb kg(-1), as a result of the addition of 1 g EDTA kg(-1) soil, a value of 1332 mg Pb kg(-1) DW shoot was obtained. EDDS application resulted in a shoot Pb accumulation of only 310 mg kg(-1)DW. Plants treated with EDDS showed lower values of biomass than those treated with EDTA. EDDS proved to be rapidly degraded, and less toxic to the soil microbial community in control non-polluted soils. Pb-polluted EDDS-treated soils showed significantly higher values of basal and substrate-induced respiration than those treated with EDTA. Although EDDS had a lower capacity to enhance Pb phytoextraction than EDTA, it has the advantage of rapid biodegradation.

Data on the selection of biostimulating agents for the bioremediation of soil simultaneously contaminated with lindane and zinc.

The bioremediation of contaminated soil often involves the addition of organic/inorganic amendments and mobilizing agents (e.g. surfactants, detergents), in order to stimulate the growth and degrading activity of soil microbial populations and increase contaminant bioavailability. For this data article we carried out an experiment to select biostimulating agents for the bioremediation of soil simultaneously contaminated with lindane (HCH, 10 mg kg-1 DW soil) and Zinc (Zn, 1500 mg kg-1 DW soil). To this purpose, a factorial design was used to test the effect of three organic amendments (i.e. hen manure, composted horse manure, cow slurry) and three mobilizing agents (i.e. sodium dodecylbenzenesulfonate (SDS), rhamnolipids and Tween-80) on the reduction of total HCH and bioavailable Zn concentration in soil. Similarly, the effect of the addition of cyclohexane, as chemical inducer of HCH degradation, was also studied. The addition of SDS, rhamnolipids and Tween-80 significantly reduced HCH concentration in soil, regardless of the presence of other biostimulating agents. When added individually, the three organic amendments (hen manure, composted horse manure, cow slurry) significantly reduced bioavailable Zn concentration in soil. These data provide useful information for the bioremediation, through biostimulation, of soils simultaneously contaminated with HCH and Zn.