Trace elements bioavailability to <Emphasis Type="Italic">Triticum aestivum</Emphasis> and <Emphasis Type="Italic">Dendrobaena veneta</Emphasis> in a multielement-contaminated agricultural soil amended with drinking water treatment residues

Purpose

The in situ stabilization of multielement-contaminated agricultural soils has limited effectiveness when using common single amendments. This study examined the use of drinking water treatment residues (WTR), based on (hydr)oxides of Fe, Al, or Mn, as a cost-effective solution to optimize the immobilization of metals (Cd, Pb, Zn) and As.

Materials and methods

Trace elements (TE) bioavailability was assessed under semi-controlled conditions in a pot study cultivating winter wheat (Triticum aestivum L. cv. Tiger) until maturity. An Fe-based WTR and a Mn-based WTR, applied at rates of 0.5 and 1% (m/m), were related to effects of lime marl (LM) application. Additionally, a bioassay with earthworms (Dendrobaena veneta) was conducted. Both bioassays were compared with measurements of NH₄NO₃-soluble, diffusive gradients in thin film (DGT)-available and soil solution TE concentrations, representing well-established surrogates for mimicking the bioavailable element fractions in soil.

Results and discussion

The application of the Fe-based WTR reduced As accumulation in vegetative wheat tissues (by up to 75%) and earthworms (by up to 41%), which corresponded with the findings from soil chemical analyses and improved plant growth and earthworm body weight. However, As concentrations in cereal grains were not affected, Cd or Pb accumulation by wheat was not mitigated, and Zn uptake was enhanced. By contrast, the Mn-based WTR effected the greatest reduction in Pb uptake, and lowered Cd transfer to wheat grain (by up to 25%). Neither the NH₄NO₃-soluble nor DGT-available concentrations matched with Cd and Zn accumulation in plants or earthworms, indicating interferences due to competition for binding sites according to the biotic ligand model.

Conclusions

The results obtained in this study suggest that a bioassay with key species prior to field application should be mandatory when designing in situ stabilization options. The application of WTR to an agricultural soil strongly affected TE bioavailability to plants and earthworms. Low application rates tended to improve biomass production of biota. Higher application rates involved risks (e.g., P fixation, TE inputs), and none of the amendments tested could immobilize all targeted elements.

     

Using delayed luminescence to characterize humic acids from lake sediments

Purpose

Using the delayed luminescence (DL) method, the photoluminescent properties of humic acids (HA) extracted from lake sediments were analyzed. Delayed luminescence is a promising technique for characterizing HA and other forms of organic matter of various origins. But information is insufficient regarding both its optimal operating conditions and also those environmental factors that control the chemical constitution of samples, which affects patterns of delayed luminescence.

Materials and methods

The research material was HA from lake sediments. Humic acid extractions were carried out using the method developed by the International Humic Substances Society. Studies on excitation and recording of DL intensity of HA solutions were carried out with the use of a specially designed device for continuous recording of photo-induced luminescence. The DL was excited with a monochromatic light at multiple wavelengths.

Results and discussion

The DL intensity depended on the wavelength of the exciting light. The highest DL intensity was obtained with excitation by blue light, the lowest DL intensity was observed with excitation by red light. Statistically significant differences among DL intensity were observed in the examined humic acids. These differences may be evidence of the variable quantitative and qualitative contributions of photoluminophores to the structure of the studied HA molecules as well as their different photochemical reactivities. For the blue- and green-excited DL intensity, statistically significant positive correlations were obtained with the elemental atomic ratio O:H and CQ coefficient. For the red-excited DL intensity, statistically significant positive correlations were obtained with the C and H content and H:C, C:N atomic ratios, while negative correlations were obtained with the free radical concentration.

Conclusions

Delayed luminescence depended on the wavelength of the exciting light. The DL intensity excited by blue and green light was different than the red light-excited DL intensity. The DL depended on the primary composition of sediments and the properties and structure of HA too. The grouping of HA showed that the HA formed in organic matter-poor, silicate-rich sediments had greater DL emission than did those extracted from sediments that were enriched in organic matter.

     

Improving Estimates of Fried’s Index from Mating Competitiveness Experiments

Sterile insect technique (SIT) and incompatible insect technique (IIT) are current methods for biological control of insect populations. Critical to the successful implementation of these biocontrol programs is quantifying the competitiveness of sterile/incompatible male insects for female mates relative to wildtype males. Traditionally, entomologists measure this mating competitiveness through a quantity known as Fried’s Index. We establish that Fried’s Index is mathematically equivalent to the mating competitiveness coefficient that features in many population models used in SIT/IIT programs. Using this insight, we propose a new approach for estimating Fried’s Index from mating competitiveness experiments. We show that this approach offers greater precision and accuracy than the traditional approach that is currently used in many studies. This is demonstrated using both simulation experiments and by analysing real experimental data. To facilitate uptake of the proposed method, we also provide an R package that can be used to easily analyse data from mating competitiveness experiments.     

Genetic variation among highly endangered <Emphasis Type="Italic">Bacopa monnieri</Emphasis> (L.) Pennell from Southern India as detected using RAPD analysis

Randomly amplified polymorphic DNA (RAPD) fingerprinting approach was applied to assess genetic diversity in different accessions of rejuvenating and intellect-promoting ancient ayurvedic medicinal herb Bacopa monnieri (L.) Pennell collected from four Southern Indian states, along with in vitro micropropagated samples maintained in the laboratory for 5 years. With the 10 analyzed primers, 110 distinct bands, in the size range of 250–870 bp were observed, and among which 14 (12.72%) were polymorphic. Among the random primers used, only OPD 02 generated highest percentage of polymorphism with 30.77. Whereas OPD 08 generated a maximum of 18 amplified bands, but with only 1% polymorphism. Cluster analysis done on the basis of similarity co-efficient generated from RAPD profiles indicated all the accessions were divided into two sub-groups based on genetic distances under one major cluster. Major cluster is only the lone loose group of the Bm.2 collected from Kerala (KER) and in vitro micropropagated plant (IVMP) maintained in the lab. The other sub-group consisted of Bm.1 and Bm.3 collected from Tamil Nadu (TN) and Andhra Pradesh (AP) respectively, which are genetically similar and showed similarity with accessions from Karnataka Bm.4 (KK). These two sub-groups were joined together at 0.66 genetic distance level. Overall, the levels of genetic similarity within the accessions varied from 0.24 to 0.80, the matrix ranged from 0.36 to 0.80, with a mean value of 0.68 indicating genetic similarity at low level.     

Comparison of phosphorus fractions and alkaline phosphatase activity in sludge,soils, and sediments

Purpose  

The land application or disposal of sewage sludge generally leads to phosphorus (P) loss in aquatic environments and often results in eutrophication. The nature of P fractions plays a key role in the transport of P within the environment, and alkaline phosphatase is important for the transformation of the P fractions. The objective of this study was to assess the P fractions and alkaline phosphatase activity in sewage sludge, soils, and sediments, in order to effectively evaluate their P bioavailability and mobility.     

Zinc fractions and availability to soybeans in representative soils of Northeast China

Purpose  

Limited information exists about the zinc (Zn) status of major soils in northeast China, and their ability to supply Zn to soybeans. This study aims to establish the critical concentrations of Zn in soil for plant growth, to characterize the Zn forms in soil, to correlate the concentration of various Zn forms with Zn uptake by soybeans, and to identify the most effective means of Zn application.     

Use of partition and redistribution indexes for heavy metal soil distribution after contamination with a multi-element solution

Purpose  

Tessier's sequential extraction method is usually used to study metal parting among different phases in soils. The main objective of this study was to determine the redistribution of trace metals which were added simultaneously to a sandy loam soil by use of the fractional distribution and reduced partition indexes and the risk of assessment code (RAC).     

A Population-Size Model for Protein Spot Detection in Proteomic Studies

In proteomic studies, a population of proteins are often examined on a gel using a technique called two-dimensional gel eletrophoresis. The technique separates the protein population into individual protein spots on a two-dimensional gel by isoelectric charge and molecular weight. The resulting gel images are then processed by a software system for spot detection and subsequent analysis. The performance of a spot-detection program is evaluated by the total number of spots that are detected. A popular spot-detection program uses the “master–slave” approach, where all spots on “slave images” are subsets of the spots on the “master image.” We argue that this approach potentially misses a large proportion of proteins and propose a model that quantifies the lack of performance. We provide nonparametric estimators for the protein population size and the expected number of proteins to be detected if a “fusion-gel” approach was used. Using the data from a rat liver proteome study, we estimate that more than half of the protein population is missed by the master–slave approach.     

Optimal Design of Dilution Experiments Under Volume Constraints

The paper develops methods to construct a one-stage optimal design of dilution experiments under the total available volume constraint typical for biomedical applications. We consider various design criteria based on the Fisher information both in Bayesian and non-Bayesian settings and show that the optimal design is typically one-atomic meaning that all the dilutions should be of the same size. The main tool is variational analysis of functions of a measure and the corresponding steepest descent-type numerical methods. Our approach is generic in the sense that it allows for inclusion of additional constraints and cost components, like the cost of materials and of the experiment itself.