Effect of Aloe Vera wastes on physico-chemical properties and microbiological activity in soils

The aim of the present study was to explore the potential for using aloe vera wastes as amendment for soil to improve its fertility. Soil was exposed to four concentrations of aloin (rich in HAP) for 0, 7, 14 and 28 days. Physico-chemical parameters were analyzed: soil Ph, organic matter (OM), nitrogen, phosphorus, and cation exchange capacity (CEC). The activity of seven enzymes implicated in the C, N and S cycles were measured. Microbial Biomass was determined by the method of substrate induced respiration. BiologEcoplates (Biolog Inc., Hayward, CA) were used to estimate soil microbial functional diversity. Our findings suggested a decrease on phosphorus and nitrogen content and an increase on CEC after aloin addition. Also, a decrease on microbial biomass and enzymes activities was observed, except for FDA. Ecoplates results demonstrate a decrease on microbial activities depending on the incubation time. Moreover, our results indicated that bacterial communities of the tested soils have more affinity to consume substrates as Amino acids and polymers. Our results should be carefully considered in view of the agriculture waists reuse for a sustainable agricultur

Impact of heavy metal contamination on oxidative stress of Eisenia andrei and bacterial community structure in Tunisian mine soil

International audienceThe aims of this work were firstly to study the effect of heavy metal-polluted soils from Tunisian mine on earth-worm biochemical biomarkers and on bacterial communities and therefore to analyze the interaction between earth worms and bacterial communities in these contaminated soils. For this purpose, we had introduced earthworm Eisenia andrei in six soils: one from mine spoils and five from agricultural soils, establishing a gradient of contamination. The response of worms to the presence of heavy metal was analyzed at the biochemical and transcriptional levels. In a second time, the impact of worm on bacterial community structure was investigated using automated ribosomal intergenic spacer analysis (ARISA) fingerprinting. An impact of heavy metal-contaminated soils on the oxidative status of E. andrei was observed, but this effect was dependent of the level of heavy metal contamination. Moreover, our results demonstrate that the introduction of earthworms E. andrei has an impact on bacterial community; however, the major change was observed in the less contaminated site. Furthermore, a significant correlation between earthworm oxidative status biomarkers and bacterial community structure was observed, mainly in the mine spoils. Therefore, we contribute to a better understanding of the relationships between epigenic earthworms and bacterial communities in heavy metal-contaminated soils

Biomarker responses of Eisenia andrei to a polymetallic gradient near a lead mining site in North Tunisia

Eisenia andrei earthworms were exposed for 7 and 14 days to six samples of soil taken from around an abandoned lead (Pb) mine and characterized by different levels of metal contamination (S6-S1, this latter being the most contaminated soil). The organisms were analyzed for metal bioaccumulation and for biological parameters as biomarkers of stress (lysosomal membrane stability; lipofuscin lysosomal content; lysosomal/cytoplasmic volume ratio) and genotoxicity (Micronucleus frequency). Chemical analysis showed the loads of Pb, Cd, Zn, and Cu in the worms following exposure. Among the stress biomarkers, lysosomal membrane stability was significantly affected in the coelomocytes of the earthworms exposed already 7 days to different contaminated soils. Organisms exposed for 14 days to S1 showed in the cells of the chloragogenous tissue, a particularly relevant increase in lipofuscin, a biomarker of oxidative stress, and an increase in the lysosome/cytoplasm volume ratio, indicating stressful condition at the tissue level. Moreover, in the same conditions, a decrease in total body weight was observed. At the longer exposure time, the coelomocytes of worms exposed to S1, S2, and S3 (soils with higher metal concentrations) showed a significant increase in micronuclei (MNi) frequency. Expressions of the P21 and topoisomerase genes, which are involved in DNA repair, showed significant up-regulation in the cells of worms exposed to S1, S2, S3, S4 and to a less extend S6. This may indicate that the worms were only able to successfully reduce the level of DNA damage in S4 and S5 if considering MN frequency data. The biomarker data was integrated by the Earthworm Expert System, allowing an objective interpretation of the complex biological data and clearly defining the areas in which the presence of chemicals is toxic for the edaphic organisms

Biochar amendment alleviates heavy metal phytotoxicity of Medicago sativa grown in polymetallic contaminated soil: Evaluation of metal uptake, plant response and soil properties

Air pollution and soil contamination have caused major environmental damage in the industrial complex of Gabes. This study aimed to evaluate the abilities of biochar to modify soil properties and assess the adaptation of alfalfa (Medicago sativa L.) plants in contaminated soils from the Gabes Region. The experiment was executed with soil samples from three sites (S1, S2 and S3) located at different distances from the industrial zone of Gabes. Additionally, a control soil was included for comparison. Pot experiments were performed under controlled conditions, with or without biochar. After 60 days, the accumulation of heavy metals in plants (roots, shoots and nodules) was determined. Moreover, oxidative stress biomarkers, such as malondialdehyde (MDA) content, glutathione-S-transferase (GST) and catalase (CAT), were evaluated. Soil microbiological properties, including bacterial functional diversity and fluorescein diacetate hydrolytic (FDA) activity, were analyzed, along with soil chemical properties. Our results revealed that biochar supplementation can improve microbial functions and cation-exchange capacity (CEC), thereby increasing the availability of nutrients to plants. Interestingly, the application of biochar resulted in decreased concentrations of copper (Cu) and zinc (Zn) in plants, which may be attributed to a reduction in their bioavailability in the soil. The accumulation of heavy metals in alfalfa organs was positively correlated with the levels of MDA and antioxidant enzymes in both leaves and roots. In this study, the addition of biochar reduced the antioxidant mechanisms of alfalfa and mitigated the negative effects of metals, resulting in a positive impact on growth and chlorophyll content. Our data highlights the beneficial effects of biochar on enhancing crop productivity and remediating contaminated soil

Ecotoxicity of trace elements to chicken GALLUS gallus domesticus exposed to a gradient of polymetallic-polluted sites.

Mining activity may cause heavy metal accumulation, which threatens human and animal health by their long-term persistence in the environment. This study aims to assess the impact of polymetallic pollution on chicken (Gallus domesticus) from old lead mining sites in northeast of Tunisia: Jebel Ressas (JR). Samples of soil and chickens were collected from five sites being ranked along a gradient of heavy metal contamination. Heavy metal loads were evaluated in soil samples and in chicken liver and kidney. Biochemical evaluation of oxidative stress parameters termed as Catalase (CAT), Glutathione-S-Transferase (GST), and Malondialdehydes (MDA) accumulation was monitored. Metallothionein protein level was assessed as a specific response to heavy metals. DNA alteration was achieved using MNi frequency in the investigated tissues. Finally, the evaluation of gene expression levels of CAT, GST, mt1, mt4, P53, bcl2, caspase3 and DNA-ligase was performed. Our data showed the highest loads of Cd, Cu, Zn and Pb in tissues of animals from site 3, being more pronounced in kidney. Biochemical data suggested a significant increase in antioxidant enzymes activities in all sites respect to control except in site 3 were CAT and GST were inhibited. DNA alteration was observed in all tissues being very pronounced in animals from site 3. Overall, transcriptomic data showed that genes involved in apoptosis were up-regulated in animals exposed to the most contaminated soils. Our data suggest that chicken and selected biomarkers offer a suitable model for biomonitoring assessment of heavy metals transfer through the food web in mining sites. Finally, the obtained results of heavy metals accumulation and related alterations should be carefully considered in view of the controversial relationship between distribution and toxicology of contaminants in exposed organisms

Biochar application mitigates salt stress on maize plant: Study of the agronomic parameters, photosynthetic activities and biochemical attributes

Climate change had caused many threats soil ecosystem, among them, soil salinity. Thus several strategies are suggested to mitigate this issue. In this context, biochar is known as a potent amendment able to alleviate the salt stress on the crops. Thus, the aim of the present investigation is to assess the impact of two salt levels (C1: 1.25 and C2: 2.5 g l−1) and two biochar rates (B1:50 g kg−1; B2: 100 g kg−1) on the agronomic, biochemical and physiological responses of maize plants (Zea mays L.). Our results revealed firstly an increase in maize biomass under salinity stress and in presence of 50g of biochar, indicating the important role of biochar in mitigating salt toxicity. Also, B1 biochar rate attenuated salt-induced oxidative stress by increasing glutathion-S-transferase (GST) and catalase (CAT) activities. Also, biochar increased chlorophyll b (Chlb) in plants treated with salt water. Overall, it can be concluded that biochar may be a useful strategy to reduce the harmful effects of salinity. However, biochar rates must be carefully used in saline soils to ameliorate plant development and reduce the toxicity of salt stress