Pb/Ca ion exchange on kaolinite clay modified with phosphates

Purpose  

Pollution of soils by heavy metal ions has attracted global concern because of the subsequent translocation into food chain which when taken up to a certain level can cause serious health problems. The influence of preadsorbed calcium by kaolinite clay modified with orthophosphate and tripolyphosphate reagents on the mobility of Pb²⁺ in kaolinitic soil system is studied. This is with the view to understand the fate of Pb²⁺ in phosphate-fertilized kaolinitic soils that are subsequently limed.     

A laboratory investigation of microbe-inducing CdCO<Subscript>3</Subscript> precipitate treatment in Cd<Superscript>2+</Superscript> contaminated soil

Background, aim and scope  

This paper discusses a method investigating the reduction of free heavy metal cation contents in soil through the use of microbe-inducing precipitate (MIP).     

Availability of polycyclic aromatic hydrocarbons in aging soils

Purpose  

The soil contamination by hydrophobic organic contaminants (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), poses great threats to human health and ecological security and attracts worldwide concerns. The total HOC concentrations overestimate its available fraction to the soil biota. Increased understanding of the availabilities of PAHs in soil environment will have considerable benefits for their risk assessment and be very instructive to food safety and remediation strategies in contaminated sites. However, the availability of PAHs in aging soils and particularly the correlations of the availabilities with their forms in soils have yet to be elucidated. In this work, the availabilities of PAHs in aging soils were evaluated using a sequential mild extraction technique.     

Germination of 151-year old <Emphasis Type="Italic">Acacia</Emphasis> spp. seeds

A collection of seeds from five Acacia species was made in Egypt in 1856. Since then, the seeds have been stored at room temperature in different Swedish museums. Due to the extreme longevity within the seeds of Acacia and related species, germination tests were performed on the now 151-year old seed. Seeds of two of the five species tested germinated. The first, Acacia farnesiana (L.) Willd., had two seeds germinate, and Acacia melanoxylon R. Br. ex Ait. f. had one seed germinate. In addition, DNA was extracted from the aged seed and DNA preservation was analyzed. Four of the tested species displayed well preserved DNA, whereas DNA from Albizia lebbeck (L.) Benth. showed signs of degradation. The 151-year longevity of the Acacia seeds is among the longest of dry-stored seeds reported. Several independent studies now report on extreme survival capacity for Acacia and related genera suggesting that these genera are suitable for studies on the characteristics of seeds with long storage performance. The results also demonstrate that herbaria and seed collections stored in museums and institutional depositories can be alternate sources of plants genetic material and should be given conservation attention.     

Phosphorus adsorption and desorption behavior on sediments of different origins

Purpose  

The aim of this study was to assess phosphorus-retention (P_ret) capacities via P adsorption (P_ads) and desorption (P_des) by sediments collected from six different sources associated with various origins, physical, and chemical characteristics.     

Evaluation of the Accuracy of Diagnostic Tests From Repeated Measurements Without a Gold Standard

A model is presented to evaluate the accuracy of diagnostic tests from data from individuals that are repeatedly tested in time. Repeated measurements from three diagnostic tests for foot-and-mouth disease, applied to vaccinated and experimentally infected cattle, were analyzed. At any time the true disease status of the individuals was unknown, i.e., no gold standard was available. The model allows for correlation between repeated test results, in consequence of the underlying structure for the unknown true disease status, but also by the distribution of the test results conditional upon true disease status. The model also allows for dependence between the different diagnostic tests conditional upon true disease status. Prior information about the structure of the prevalence and the specificity of the tests was incorporated in a Bayesian analysis. Posterior inference was carried out with Markov chain Monte Carlo. Simulated data were analyzed to gain insight into the performance of the posterior Bayesian inference. The simulated data are typical for the expensive and, therefore, modestly sized infection experiments that are conducted under controlled conditions.     

Agent-Based Inference for Animal Movement and Selection

Contemporary ecologists often find themselves with an overwhelming amount of data to analyze. For example, it is now possible to collect nearly continuous spatiotemporal data on animal locations via global positioning systems and other satellite telemetry technology. In addition, there is a wealth of readily available environmental data via geographic information systems and remote sensing. We present a modeling framework that utilizes these forms of data and builds on previous research pertaining to the quantitative analysis of animal movement. This approach provides additional insight into the environmental drivers of residence and movement as well as resource selection while accommodating path uncertainty. The methods are demonstrated in an application involving mule deer movement in the La Sal Range, Utah, USA. Supplemental materials for this article are available online.     

Holocene sediment accretion in the Trinity River delta,Texas, in relation to modern fluvial input

Purpose  

This study uses sediment cores to quantify Holocene sedimentation rates in the Trinity River delta, Texas. An important question is whether modern fluvial sediment input from the Trinity River is adequate to sustain sedimentation in the delta, thereby combating subsidence and further wetland loss. Our objective was to quantify sedimentation rates within the delta in order to assess whether the delta is in- or out-of-phase with modern sediment delivery rates.     

Bioaccumulation of ivermectin from natural and artificial sediments in the benthic organism <Emphasis Type="Italic">Lumbriculus variegatus</Emphasis>

Purpose  

Although ivermectin is a widely used lipophilic parasiticide, data on its potential bioaccumulation in aquatic invertebrates are scarce. In this study, bioaccumulation patterns of radiolabeled ³H-ivermectin from sediments into tissues of the sediment-dwelling worm Lumbriculus variegatus were investigated and assessed.     

Arbuscular mycorrhizal association is beneficial for growth and detoxification of xenobiotics of barley under drought stress

Background, aim, and scope  

Plant growth and productivity under abiotic stresses such as water shortage or pollution are major problems which currently worry scientists in the field of food production and plant health. Since the intensification of livestock production with its associated increased demand for fodder has encouraged farmers to rely more heavily on chemical fertilizers, very often, municipal waste and wastewater sludge is considered a possible source of plant nutrients, although it might carry a significant amount of anthropogeneous pollutants. The extent to which plants react to drought, as well as how pollutants are taken up or how they act on plants, might depend on rhizosphere processes such as mycorrhizal symbioses. Therefore, it seemed timely to investigate plant defense reactions in the presence of arbuscular mycorrhizal fungi (AMF) toward a possible dangerous sewage sludge pollutant under the influence of drought.