Effects of natural zeolites on ryegrass growth and bioavailability of Cd,Ni, Pb,and Zn in an Albanian contaminated soil

Purpose

The use of eco-friendly and cost-effective adsorbent materials in the remediation of soils contaminated by potentially toxic elements (PTE) is a sustainable way of reducing the transfer of these elements into the food chain. However, an evaluation of the potential of natural zeolites to immobilize toxic elements in contaminated soils was required to enable their efficient use.

Materials and methods

The effect of natural zeolite (Stilbite-Stellerite) from the Munella area (Northern Albania), added at rates ranging from 1.25 to 10 % w/w on a contaminated soil was investigated in a greenhouse pot experiment with ryegrass (Lolium multiflorum L.) and by selective extractions. PTE availability for plants was assessed either as their accumulation in plant tissue or by DTPA-extraction. Oral bio-accessibility was estimated by the in vitro PBET method and the mobility and consequent potential risk of leaching by the USEPA TLCP method. The effect of zeolites on soil properties (pH, electrical conductivity-EC, organic C, and total N) was also investigated. A five steps sequential extraction procedure (SEP) was applied to investigate the immobilization mechanism.

Results and discussion

The addition of 2.5% w/w of natural zeolites caused a significant decrease of PTE mobility, but to observe a significant reduction of DTPA-extractable metals, it was necessary to reach 10% addition rate. In contrast, plant growth showed a gradual increase with addition rate and a corresponding decrease of concentration of PTE in plant tissue. Correlation between DTPA-extractable PTE and their concentration in both root and shoot plant tissue was rather poor. Human hazard due to soil ingestion (PBET method) changed only for Cu and Zn in the gastric phase with 1.25 and 5% addition rate respectively, whereas decreased for Cu and Zn at 5% rate in the Intestinal phase. The results of SEP support the hypothesis that the main mechanism involved in metals fixation are as follows: (1) insolubilization by pH rise, (2) adsorption on Fe/Mn oxides (3) increase of cation exchange retention, (4) organic complexation.

Conclusions

The results of this work suggest that the addition of natural zeolites from the Munella area (AL) is a sustainable practice to reduce the environmental impact of PTE contaminated soils, but an assessment on the longevity of their immobilization need to be evaluated in the long-term perspectives.

     

Induction of wheat and maize glutathione S-transferase by some herbicide safeners and their effect on enzyme activity against butachlor and terbuthylazine

The expression of glutathione S-transferase (GST) activity in wheat and maize shoots was investigated in response to treatments with the herbicide safeners benoxacor, cloquintocet-mexyl, fenchlorazole-ethyl, fenclorim, fluxofenim and oxabetrinil. These safeners significantly enhanced the GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB) as a 'standard' substrate, with the exception of oxabetrinil in maize. The enhancements of GST (CDNB) activity were found to be concomitant with increases in V(max) (the reaction rate when the enzyme is fully saturated by the substrate) in wheat following cloquintocet-mexyl and fenchlorazole-ethyl treatments, and in maize following fenchlorazole-ethyl treatment. Otherwise, decreases in V(max) were observed in wheat and maize following fenclorim and fluxofenim treatments. With the exception of oxabetrinil, all the safeners significantly reduced the apparent K(M) (the substrate concentration required for 50% of maximum GST activity) of both wheat and maize GST. The V(max) and K(M) variations following safener treatments are discussed in terms of an increased expression of GST enzymes and an increased affinity for the CDNB substrate. The activity of wheat and maize GST was also assayed towards butachlor and terbuthylazine respectively; the results indicate the ability of cloquintocet-mexyl, fenchlorazole-ethyl and fluxofenim to enhance the enzyme activity in wheat and of benoxacor and fenchlorazole-ethyl to do so in maize.     

Occurrence, prevalence and molecular diversity of banana streak viruses in Cuba

Banana streak viruses (BSV) belong to the genus Badnavirus of the family Caulimoviridae. They cause banana streak disease on banana and plantains worldwide. The recent detection of BSV in Cuba has prompted a nationwide research effort focused on the occurrence, prevalence and diversity of BSV species on dessert type banana on the island. Indexing by multiplex immunocapture-PCR (M-IC-PCR) performed on samples collected throughout the country showed that the overall prevalence of Banana streak OL virus, Banana streak GF virus and Banana streak IM virus is low in Musa acuminata genotypes in Cuba. However, the prevalence of BSV species Mysore (BSMYV) was surprisingly high in samples of cv Yangambi km5 collected from distinct and distant locations. The presence in Cuba of an as yet unreported BSV species was also investigated, showing that Banana steak VN virus is also present in Musa acuminata genotypes.     

Experimental infection with H1N1 European swine influenza virus protects pigs from an infection with the 2009 pandemic H1N1 human influenza virus

The recent pandemic caused by human influenza virus A(H1N1) 2009 contains ancestral gene segments from North American and Eurasian swine lineages as well as from avian and human influenza lineages. The emergence of this A(H1N1) 2009 poses a potential global threat for human health and the fact that it can infect other species, like pigs, favours a possible encounter with other influenza viruses circulating in swine herds. In Europe, H1N1, H1N2 and H3N2 subtypes of swine influenza virus currently have a high prevalence in commercial farms. To better assess the risk posed by the A(H1N1) 2009 in the actual situation of swine farms, we sought to analyze whether a previous infection with a circulating European avian-like swine A/Swine/Spain/53207/2004 (H1N1) influenza virus (hereafter referred to as SwH1N1) generated or not cross-protective immunity against a subsequent infection with the new human pandemic A/Catalonia/63/2009 (H1N1) influenza virus (hereafter referred to as pH1N1) 21 days apart. Pigs infected only with pH1N1 had mild to moderate pathological findings, consisting on broncho-interstitial pneumonia. However, pigs inoculated with SwH1N1 virus and subsequently infected with pH1N1 had very mild lung lesions, apparently attributed to the remaining lesions caused by SwH1N1 infection. These later pigs also exhibited boosted levels of specific antibodies. Finally, animals firstly infected with SwH1N1 virus and latter infected with pH1N1 exhibited undetectable viral RNA load in nasal swabs and lungs after challenge with pH1N1, indicating a cross-protective effect between both strains.     

Eocene Patagonia fossils of the daisy family

Fossil capitula and pollen grains of Asteraceae from the Eocene of Patagonia, southern Argentina, exhibit morphological features recognized today in taxa, such as Mutisioideae and Carduoideae, that are phylogenetically close to the root of the asteracean tree. This fossil supports the hypothesis of a South American origin of Asteraceae and an Eocene age of divergence and suggests that an ancestral stock of Asteraceae may have formed part of a geoflora developed in southern Gondwana before the establishment of effective dispersal barriers within this landmass.     

Artificial neural networks as a tool for plant identification: a case study on Vietnamese tea accessions

Seventeen tea accessions belonging to Chinese (Camellia sinensis), Assamic (C. sinensis var. assamica), and Shan tea (C. sinensis var. pubilimba) groups, which are either commercially planted or new promising tea germplasm, were morphologically described at Phu Tho province (Viet Nam) and assessed for their diversity. Fourteen phyllometric parameters were qualitatively and quantitatively investigated using digital image analysis. The accessions were then discriminated by a dedicated artificial neural network for univocal plant identification and a hierarchical cluster analysis was performed in order to build a dendrogram reporting the relationships among them. Results proved the diversity of investigated tea morphotypes from Phu Tho province based on a morphological screening. More, the artificial neural network was able to perform a correct identification for almost all the accessions using simple dedicated instruments.