Remediation of lead-, arsenic-, and cesium-contaminated soil using consecutive washing enhanced with electro-kinetic field

Purpose

Extensive deposition of Pb, As, and Cs in soils may damage ecosystems and human’s health. Soil washing is the most conventional remediation method, and its efficiency depends on metal solubility in soil. This study aims to optimize operating variables of electro-kinetic field (EKF)-enhanced soil washing procedures.

Materials and methods

Soil samples from a Mississippi River Delta rice field were homogeneously spiked with Pb, As, and Cs, and contaminated soil was aged for 3 months. The remediation involved a first stage electro-kinetic process, followed by a soil washing procedure. Soil pH changes under EKF were studied. Effects of citric acid and reversed EKF were investigated for alleviating possible alkaline precipitation. In the washing procedure, soil washing time and cycles with different extractants were examined. The overall EKF-enhanced soil washing efficiencies were discussed as well.

Results and discussion

The implement of EKF offered an acidic soil environment around the anode areas for solubilizing metal(loid)s. Combined with EKF, citric acid was more conductive to desorb metal(loid)s. In addition, the reversed EKF effectively alleviated metal(loid) precipitation caused by alkalization in the first stage cathode areas. The EKF significantly enhanced metal(loid) extractions in the anode area of soils using Na₂EDTA, CaCl₂, and citric acid at pH of 2. The most preferable removal of Pb (80–98 %), As (48–63 %), and Cs (10–13 %) was achieved with three extractants. CaCl₂ and citric acid were proved to be suitable alternatives to Na₂EDTA for Pb extraction. A washing process of 2 h extraction with double washing cycles was optimized.

Conclusions

Soil washing time and cycles were major factors governing the metal(loid) removal from soil. Washing process of 2 h extraction with double cycles was optimized for further extraction based on higher washing efficiency. The EKF effectively improved washing efficiency while some electrical parameters need further studies for cost performance consideration.

     

Spatio-temporal variability of drought characteristics across Pakistan

Climate change in Pakistan has a great impact on the spatial and temporal variation of precipitation and ultimately alters the frequency and duration of droughts. In this study, spatial and temporal trend analyses of precipitation and droughts were observed at 58 meteorological stations across Pakistan from 1981 to 2018. The existing trend analysis methods were evaluated to address the issue of serial correlation in the climatic data. Results of precipitation analysis showed significant decreasing trends in winter (November, December) and significant increasing trends were observed in summer (June and September) at a confidence level of 95 percent. The magnitude of the precipitation trends showed the highest variation during summer season and the least variation in winter season. Rotated Principal Component (RPC) analysis showed the severe droughts (high positive loading) in southeastern side (Sindh province) of Pakistan due to lack of summer rains. Furthermore, variance correction approaches are identified as the most suitable in coping with the effect of serial correlation. The highest drought frequencies were observed in the southern areas of Pakistan and the drought events are expected to occur more frequently in the late winter, early spring, and early autumn, while droughts were expected to occur least frequently in summer.

     

The Effect of Salicylic Acid On Photosynthetic Characteristics,Growth Attributes,and Some Antioxidant Enzymes On Parsley (Petroselinum crispum L.) Under Salinity Stress

Gesunde Pflanzen - Parsley (Petroselinum crispum L.) is widely used in food, medicine, cosmetics, and pharmaceutical industries. This research was conducted to determine the effect of six...     

Preparation of glucosamine from exoskeleton of shrimp and predicting production yield by response surface methodology

Chitin was prepared from Persian Gulf shrimp (Metapenaeus monoceros), and then, the obtained chitin was hydrolyzed by hydrochloric acid solutions. The production yield of glucosamine hydrochloride from chitin was optimized, and the effect of three factors (acid concentration, acid to chitin ratio, and reaction time) was investigated. A Box-Behnken design by Minitab software created 12 reactions with different conditions. Each reaction was performed in two replicates. Response surface methodology was used for predicting the glucosamine preparation. The optimum conditions for glucosamine hydrochloride preparation were 30 and 37% hydrochloric acid, 9:1 (v/w) acid solution to solid ratio, and 4 h of reaction time. Time ratio and time acid concentrations were the effective factors on the yield.     

Metabolism of DDT and related compounds in cell suspension cultures of soybean (Glycine max L.) and wheat (Triticum aestivum L.)

Cell suspension cultures of wheat and soybean were incubated with [¹⁴C]-1,1,1-trichloro-2,2-bis-(4-chlorophenyl)ethane (DDT), [¹⁴C]-1,1-dichloro-2,2-bis-(4-chlorophenyl)ethene (DDE), and [¹⁴C]-2,2-bis-(4-chlorophenyl)acetic acid (DDA) under standardized conditions. Polar metabolites were formed in yields of 1–2.5% in the cases of DDT and DDE, and of 56% in the case of DDA. A nonpolar metabolite was only observed in the case of DDT in soybean. This metabolite was identified as DDE on the basis of cochromatography and mass spectroscopy. By the same methods DDA was identified as a major polar DDT metabolite of both soybean and wheat. The further conversion of DDA to hexose esters was demonstrated by chromatographic and mass spectroscopic comparison with synthetic DDA-β-d-glucopyranosyl tetraacetate. These studies suggest the metabolic sequence, DDT → DDA → DDA-hexose ester.     

Electrospun titanium dioxide nanofibers: Fabrication,properties and its application in photo-oxidative degradation of methyl orange (MO)

In this study, we synthesed two kind of TiO₂ nanomaterial (nanoparticles and nanofiber) for photocatalitic degradation of methyl orange (MO) as pollutant. TiO₂ nanoparticles were synthesized by sol-gel technique using titanium (IV) isopropoxide as precursor. Polyvinyl acetate (PVAc)/TiO₂ hybrid nanofibers were fabricated by combining sol-gel process with electrospinning technology, which consisted of PVAc as organic segment and TiO₂ as inorganic part. Crystalline phase of TiO₂ nanomaterials was investigated by X-ray diffraction (XRD). The XRD results show that the TiO₂ nanomaterials crystallize in anatase with some rutile phase and these consist of titanium dioxide nano-crystals. The surface structures of TiO₂ nanomaterials were examined using scanning electron microscopy (SEM). SEM scanning revealed that the nanoparticle and nanofibrous structure was formed. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the chemical structures of the PVAc/TiO₂ hybrid nanofibers. The FTIR analysis indicated the newly formed associated hydrogen bond because of the hybrid effect between PVAc and TiO₂ sol. Finally, The photooxidative decomposition of methylene blue by using the titania nanomaterials was examined and compared.     

Binding,fractionation, and distribution of Cs,Co, and Sr in a US coastal soil under saturated and field capacity moisture regimes

Purpose

The concerns of the public on safe handling of nuclear energy power facilities have increased due to the recent nuclear plant accidents in Japan and others. Cesium, cobalt, and strontium are a few of the major radionuclides released from nuclear power plant accidents. The objectives of this study are to investigate binding, distribution, fractionation, and transformation of cesium (Cs), cobalt (Co), and strontium (Sr) in a US coastal soil under saturated paste (SP) and field capacity (FC) moisture regimes.

Materials and methods

There are four major nuclear power plants in the coast region around the northern Gulf of Mexico where coastal soil often undergoes soil moisture change. A coastal soil was taken from the middle region of these major nuclear power plants and spiked with different concentrations of cesium, cobalt, and strontium salts. The sequential selective dissolution technique was used to investigate the transformation and fractionations of these metals in the coastal soils affected by moisture regime, a key factor in the coastal environment.

Results and discussion

The adsorption kinetics showed that both Co and Sr reached the adsorption plateau even after 5 h of adsorption, indicating a fast initial adsorption process in the coastal soil. Cesium, cobalt, and strontium were dominantly presented in the soluble and exchangeable form (EXC) (Cs?>?Co and Sr), which linearly increased with the addition levels, possessing the high bioavailability, mobility, and ecotoxicity. Saturated regime significantly reduced the soluble and exchangeable form compared to field capacity moisture regime.

Conclusions

The current study provides the fundamental understanding for designing the cost-effective remediation technology to remediate these metals in coastal soil by targeting on the soluble and exchangeable forms and better prepare the USA for future potentially nuclear power plant accidents.

     

Physiological effects of psyllid (Paratrioza cockerelli) on potato

Feeding by psyllid nymphs causes “Psyllid yellows,” a characteristic yellowing of shoots which results in a dramatic loss of tuber yield. If psyllid infestation is not controlled, the onset of shoot yellowing and growth reductions can occur within two weeks. When insecticides are applied after yellowing, recovery of plants often is not complete. In this study comparisons were made of the physiology and growth of tops and tubers of recovered and permanently injured potatoes of the cultivars ‘Denali,’ ‘Kennebec,’ and ‘Norgold Russet.’ Permanently injured plants senesced rapidly, developed less shoot growth, aerial tubers and shortened and thickened internodes. They had lower tuber yields than plants that recovered. Permanently injured ‘Denali’ developed shoots on old flowering stems. In permanently injured plants of all cultivars, the tubers were small and badly misshapen but numbers increased. In recovered ‘Kennebec’ plants tubers were also misshapen, but were of average size. Tubers of recovered ‘Denali’ and ‘Norgold Russet’ were of acceptable shape. In samplings made during tuber growth, dry weight percentages of total soluble sugars, sucrose and glucose of tubers from permanently injured plants were found to be the same as those of recovered plants. In all cultivars, starch percentages of tubers from permanently injured plants were higher than that of the recovered, but the pattern of carbohydrate content changes was similar for permanently injured and recovered cultivars.     

Effect of exogenous application of free polyamines on physiological disorders and yield of ‘Kaleh-Ghoochi’ pistachio shoots (Pistacia vera L.)

Pistachio trees exhibit some physiological disorders such as abscission of inflorescence buds, fruit abscission, the production of blank, non-split, early-split and deformed nuts. Since the occurrence of these disorders is closely related to the yield, the effect of free polyamine treatments on these disorders and the yield was investigated in two consecutive years (“on” and “off” years). Free polyamine treatments were applied one week before and also two weeks after full bloom. Results showed that Spermine (Spm), unlike Putrescine (Put), decreased the physiological disorders of pistachio and also increased the yield. Free polyamine treatments did not affect the percentage of early-split nuts. Spermidine (Spd) decreased the percentage of both fruit abscission and deformed nuts but did not affect the yield. In both the “on” and “off” years the effect of Spm and Spd was greatly dependent on both the time of application and the concentrations used. Results of free polyamine analysis showed that exogenous application of these compounds, especially two weeks after full bloom, increased the free polyamine contents of shoots in both “on” and “off” years confirming the absorption of free polyamines via spray application in pistachio crop. Exogenous application of Spm two weeks after full bloom decreased the abscission of inflorescence buds in “on” year supporting the idea that free polyamines could trigger the abscission process of inflorescence buds. Since Spm decreased the percentage of blank, non-split and deformed nuts, it seems that Spm dominantly plays a key role in the growth and development of pistachio nuts.     

Molecular characterization of the wild relatives of safflower (Carthamus tinctorius L.) in Turkey as revealed by ISSRs

In the present study, we used 39 plant samples representing six Carthamus taxa collected from different regions of Turkey: 11 of C. dentatus, 5 of C. glaucus, 18 of C. lanatus, 3 of C. persicus, 1 of C. tenuis subsp. tenuis and 1 of C. tenuis subsp. gracillimus. On these samples, we screened nine ISSR markers for polymorphic products. We generated 151 polymorphic bands. In a dendrogram based on these ISSR bands, the first branch was C. tenuis subsp. gracillimus, then C. persicus formed the second group. The rest of the taxa were grouped in two clusters: the first included C. lanatus, C. tenuis subsp. tenuis and C. glaucus, and the second included C. dentatus. Within the first cluster, C. tenuis subsp. tenuis and C. glaucus grouped together and then united to C. lanatus. Representatives of the same taxa consistently clustered together. Also within species, the groupings were generally concordant with their geographical distributions.