The influence of arsenic speciation (AsIII & AsV) and concentration on the growth, uptake and translocation of arsenic in vegetable crops (silverbeet and amaranth): greenhouse study

We examined arsenic (As) uptake by vegetable crops (amaranth, Amaranthus gangeticus, and silverbeet, Beta vulgaris) as affected by As speciation (As^III and As^V) and their concentrations in nutrient solution. Amaranth and silverbeet were grown in a nutrient solution containing four levels of arsenate (As^V): 0, 1, 5, and 25 mg As/l and three levels of arsenite (As^III): 0, 5, 10 mg As/l. Both As^V and As^III are phytotoxic to these crops with the latter being five times more toxic. Amaranth treated with As^III exhibited As toxicity symptoms within 48 h of exposure and was close to death within 1 week. However, As^V treatment did not show clear toxicity symptoms other than wilting and yield reduction at the highest dose rate of 25 mg As^V/l. The main mechanism used by vegetable crops to tolerate As^V is probably avoidance—limiting As transport to shoots and increasing As accumulation in the root system. When As^V was added to the nutrient solution, the uptake of As in shoots increased and, at the highest dose (25 mg As^V/l), 60 μg As/g DW (3.6 mg/kg FW) accumulated in the edible portion, which exceeds the WHO recommended limit for food stuffs (2 mg/kg FW) as the water contents of the crops were 94%. It is therefore important to determine the nature of the As species and their bio-accessibility. Iron treatment with 0.5 mg NaFe(III)EDTA/l dose decreased silverbeet As uptake by 45% given its affinity to bind As at the root surface or root rhizosphere and so restrict As translocation to the shoots.     

Vermiculture and waste management: study of action of earthworms Elsinia foetida, Eudrilus euginae and Perionyx excavatus on biodegradation of some community wastes in India and Australia

The practice of vermiculture is at least a century old but it is now being revived worldwide with diverse ecological objectives such as waste management, soil detoxification and regeneration and sustainable agriculture. Earthworms act in the soil as aerators, grinders, crushers, chemical degraders and biological stimulators. They secrete enzymes, proteases, lipases, amylases, cellulases and chitinases which bring about rapid biochemical conversion of the cellulosic and the proteinaceous materials in the variety of organic wastes which originate from homes, gardens, dairies and farms. The process is odour free because earthworms release coelomic fluids in the decaying waste biomass which has anti-bacterial properties which kills pathogens. The species used in India were Indian blue (Perionyx excavatus), African night crawler (Eudrilus euginae) and the Tiger worm (Elsinia foetida). E. foetida was used in Australia. E. euginae was found to have higher feeding, growth and biodegradation capacity compared to other two species.Earthworm action was shown to enhance natural biodegradation and decomposition of wastes (60–80 percent under optimum conditions), thus significantly reducing the composting time by several weeks. Within 5 to 6 weeks, 95–100 percent degradation of all cellulosic materials was achieved. Even hard fruit and egg shells and bones can be degraded, although these may take longer.     

Development of a Methodology for Selecting Criteria and Indicators of Sustainable Forest Management: A Case Study on Participatory Assessment

This paper describes an application of multiple criteria analysis (MCA) in assessing criteria and indicators adapted for a particular forest management unit. The methods include: ranking, rating, and pairwise comparisons. These methods were used in a participatory decision-making environment where a team representing various stakeholders and professionals used their expert opinions and judgements in assessing different criteria and indicators (C&I) on the one hand, and how suitable and applicable they are to a forest management unit on the other. A forest concession located in Kalimantan, Indonesia, was used as the site for the case study. Results from the study show that the multicriteria methods are effective tools that can be used as structured decision aids to evaluate, prioritize, and select sets of C&I for a particular forest management unit. Ranking and rating approaches can be used as a screening tool to develop an initial list of C&I. Pairwise comparison, on the other hand, can be used as a finer filter to further reduce the list. In addition to using these three MCA methods, the study also examines two commonly used group decision-making techniques, the Delphi method and the nominal group technique. Feedback received from the participants indicates that the methods are transparent, easy to implement, and provide a convenient environment for participatory decision-making.     

一种改进的多学习教与学优化算法

针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。     

Role of microbes,metabolites and effector compounds in host–microbiota interaction: a pharmacological outlook

Environmental Chemistry Letters - Microbial cells react with intestinal surfaces and produce enzymes and metabolites that influence human health, host metabolism and immunity. Gut...     

Predictive modelling of piezometric head and seepage discharge in earth dam using soft computational models

Environmental Science and Pollution Research - Predictions of pore pressure and seepage discharge are the most important parameters in the design of earth dams and assessing their safety during the...     

Assisted phytostabilization of Pb-spiked soils amended with charcoal and banana compost and vegetated with Ricinus communis L. (Castor bean)

Environmental Geochemistry and Health - A greenhouse experiment was performed to elucidate the potency of Prosopis juliflora charcoal (PJC) and banana waste compost (BWC) to improve soil fertility...     

Development of a modular vapor intrusion model with variably saturated and non-isothermal vadose zone

Environmental Geochemistry and Health - Human health risk assessment at hydrocarbon-contaminated sites requires a critical evaluation of the exposure pathways of volatile organic compounds...     

Sorption and bioavailability of arsenic in selected Bangladesh soils

The bioavailability of arsenic (As) in the soil environment is largely governed by its adsorption–desorption reactions with soil constituents. We have investigated the sorption–desorption behaviour of As in four typical Bangladeshi soils subjected to irrigation with As-contaminated groundwater. The total As content of soils (160 samples) from the Laksham district ranged from <0.03 to approximately 43 mg kg⁻¹. Despite the low total soil As content, the concentration of As in the pore water of soils freshly irrigated with As-contaminated groundwater ranged from 0.01 to 0.1 mg l⁻¹. However, when these soils were allowed to dry, the concentration of As released in the pore water decreased to undetectable levels. Remoistening of soils to field moisture over a 10-day period resulted in a significant (up to 0.06 mg l⁻¹) release of As in the pore water of soils containing >10 mg As kg⁻¹ soil, indicating the potential availability of As. In soils containing <5 mg As kg⁻¹, As was not detected in the pore water. A comparison of Bangladeshi soils with strongly weathered long-term As-contaminated soils from Queensland, Australia showed a much greater release of As in water extracts from the Australian soils. However, this was attributed to the much higher loading of As in these Australian soils. The correlation of pore water As with other inorganic ions (P, S) showed a strongly significant (P < 0.001) relationship with P, although there was no significant relationship between As and other inorganic cations, such as Fe and Mn. Batch sorption studies showed an appreciable capacity for both As^V and As^III sorption, with As^V being retained in much greater concentrations than As^III.