Root-associated (rhizosphere and endosphere) microbiomes of the Miscanthus sinensis and their response to the heavy metal contamination

The plant root-associated microbiomes, including both the rhizosphere and the root endosphere microbial community, are considered as a critical extension of the plant genome. Comparing to the well-studied rhizosphere microbiome, the understanding of the root endophytic microbiome is still in its infancy. Miscanthus sinensis is a pioneering plant that could thrive on metal contaminated lands and holds the potential for phytoremediation applications. Characterizing its root-associated microbiome, especially the root endophytic microbiome, could provide pivotal knowledge for phytoremediation of mine tailings. In the current study, M. sinensis residing in two Pb/Zn tailings and one uncontaminated site were collected. The results demonstrated that the metal contaminant fractions exposed strong impacts on the microbial community structures. Their influences on the microbial community, however, gradually decreases from the bulk soil through the rhizosphere soil and finally to the endosphere, which resulting in distinct root endophytic microbial community structures compared to both the bulk and rhizosphere soil. Diverse members affiliated with the order Rhizobiales was identified as the core microbiome residing in the root of M. sinensis. In addition, enrichment of plant-growth promoting functions within the root endosphere were predicted, suggesting the root endophytes may provide critical services to the host plant. The current study provides new insights into taxonomy and potential functions of the root-associated microbiomes of the pioneer plant, M. sinensis, which may facilitate future phytoremediation practices.     

Atmospheric NH3 as plant nutrient: a case study with Brassica oleracea

Nutrient-sufficient and nitrate- or sulfate-deprived plants of Brassica oleracea L. were exposed to 4 microl l(-1) NH3 (2.8 mg m(-3)), and effects on biomass production and allocation, N-compounds and root morphology investigated. Nitrate-deprived plants were able to transfer to atmospheric NH3 as nitrogen source, but biomass allocation in favor of the root was not changed by exposure to NH3. NH3 reduced the difference in total root length between nitrate-sufficient and nitrate-deprived plants, and increased the specific root length in the latter. The internal N status, therefore, might be involved in controlling root length in B. oleracea. Root surface area, volume and diameter were unaffected by both nitrate deprivation and NH3 exposure. In sulfate-deprived plants an inhibitory effect of NH3 on root morphological parameters was observed. These plants, therefore, might be more susceptible to atmospheric NH3 than nitrate-deprived plants. The relevance of the present data under field conditions is discussed.     

Above and below ground biomass patterns in arid lands

Regular vegetation patterns have been observed in many arid zones around the word. This particular spontaneous arrangement of the vegetation optimizes the use of the scarce water resources and could be imitated to restore vulnerable ecosystems; at the same time, the patterns of vegetation act as an early warning signal of the fact that fragile ecosystems may suddenly undergo irreversible shifts, thus, they deserve a special attention. The formation of vegetation patterns is the object of many theoretical and experimental studies, nevertheless, in previous works, the interest that is deserved to below ground biomass allocation is minor as compared to the effort that is spent to describe the organization of vegetation above ground.     

The enhancement of photodegradation efficiency using Pt-TiO2 catalyst

The residues from the extraction of lead/zinc (Pb/Zn) ores of most Pb/Zn mines are permanently stored in tailings ponds, which require revegetation to reduce their environmental impact. This can only be done if the main constraints on plant establishment are evaluated. This can readily be done by field and greenhouse studies.

To test this, the properties of different tailings from Lechang Pb/Zn mine located at the north of Guangdong Province in southern China have been studied. Physical and chemical properties including concentrations of metals (Pb, Zn, Cd and Cu) in the tailings and soils collected from different sites have been measured. The results showed that tailings contain low nitrogen (0.016–0.075%), low-organic matter (0.58–1.78%), high salt (3.55–13.85 dS/m), and high total and diethylene–tetramine–pentaacetic acid (DTPA)-extractable metal concentrations (total: 1019–1642 μg g⁻¹ Pb, 3078–6773 μg g⁻¹ Zn, 8–23 μg g⁻¹ Cd, and 85–192 μg g⁻¹ Cu; DTPA-extractable: 59–178 μg g⁻¹ Pb, 21–200 μg g⁻¹ Zn, 0.30–1.5 μg g⁻¹ Cd, and 4.3–12 μg g⁻¹ Cu). Aqueous extracts of tailings/soils (10%, 20% and 30%, w/v) from different sites were prepared for testing their effects on seed germination and root elongation of a vegetable crop Brassica chinensis and a grass species Cynodon dactylon. It was found that root elongation provided a better evaluation of toxicity than seed germination. The ranking of toxicity using root elongation was: high-sulfur tailings>tailingdam>sparsely vegetated tailings>densely vegetated tailings>mountain soil for both plants. This order was consistent with DTPA-extractable Pb contents in the tailings and soils. B. chinensis seedlings were then grown in the mixtures of different proportions of tailings and farm soil for 4 weeks, and the results (dry weights of seedlings) were in line with the root elongation test. All these demonstrated that heavy metal toxicity, especially available Pb, low content of nutrient, and poor physical structure were major constraints on plant establishment and colonization on the Pb/Zn mine tailings.     

The plant-enhanced bio-cathode: Root exudates and microbial community for nitrogen removal

A plant bio-electrochemical system(PBES) was constructed for organic pollutant removal and power generation. The bio-cathode, composed of granular activated carbon(GAC), stainless wire mesh and a plant species(Triticum aestivum L.), was able to catalyze cathodic reactions without any requirement for aeration or power input. During the 60-day-long operation, an average voltage of 516 m V(1000 Ω) and maximum power density(Pmax) of 0.83 W/m~3 were obtained in the PBES. The total nitrogen removal and total organic carbon removal in the PBES were 85% and 97%, respectively. Microbial community analyses indicated that bacteria associated with power generation and organic removal were the predominant species in the bio-cathode, and plant-growth-promoting rhizobacteria were also found in the PBES. The results suggested that the coupling of plants with the GAC cathode may enhance the organicmatter degradation and energy generation from wastewater and therefore provide a new method for bio-cathode design and promote energy efficiency.     

Improving safety and availability of complex systems using a risk-based failure assessment approach

This paper presents a structured risk-based failure assessment (RBFA) approach, which provides a complete solution to avoid repeated and potential failures to improve overall plant safety and availability. Technological advancements and high product demand have encouraged designers to design mega-capacity systems to enhance system utilization and improve revenues. However, these benefits make the systems more complex and thus prone to unnoticed failure. It is an overwhelming task to address all the failures due to the limited resources and time constraints. This leads to substandard and poor quality failure assessments, which cause repeated failures. To address this common industry concern, a four phase RBFA framework is proposed which is not limited to the identification of root cause(s) but also includes other actions such as failure monitoring. The four phases include the plan phase, the assessment phase, the analysis phase and the implementation-tracking phase. These phases cover identification of failure, failure analysis, root cause(s) analysis, and failure monitoring. In this paper, the applicability and advantages of the proposed approach are examined through two real case studies pertaining to bearing failure and drive coupling failure. By implementing the proposed approach, significant improvements have been experienced in the system availability in both the cases.     

Assisted phytoremediation of mixed metal(loid)-polluted pyrite waste: effects of foliar and substrate IBA application on fodder radish

Exogenous application of plant-growth promoting substances may potentially improve phytoremediation of metal-polluted substrates by increasing shoot and root growth. In a pot-based study, fodder radish (Raphanus sativus L. var. oleiformis Pers.) was grown in As-Zn-Cu-Co-Pb-contaminated pyrite waste, and treated with indolebutyric acid (IBA) either by foliar spraying (10 mg L⁻¹), or by direct application of IBA to the substrate (0.1 and 1 mg kg⁻¹) in association, or not, with foliar spraying. With the exception of foliar spraying, IBA reduced above-ground biomass, whilst direct application of IBA to the substrate surface reduced root biomass (−59%). Trace element concentrations were generally increased, but removals (mg per plant) greatly reduced with IBA application, together with greater metal leaching from the substrate. It is concluded that, in our case, IBA had a negative effect on plant growth and phytoextraction of trace elements, possibly due to unsuitable root indoleacetic acid concentration following soil IBA application, the direct chelating effect of IBA and the low microbial activity in the pyrite waste affecting its breakdown.     

Lysimeter Soil Retriever (LSR)—An Application of a New Technique for Retrieving Soils from Lysimeters

In Europe more than 2,500 lysimeters operated by research institutes and industry (Lanthaler 2005). Originally lysimeters were built for investigations of soil water and solutes, nutrient leaching and pesticide degradation (see e.g. Winton and Weber 1996). Currently lysimeters additionally used as a tool for investigations on biological processes, and structural changes of plants, including root distribution, and enzyme activities etc. (see e.g. Dizer et al. 2002; Schloter et al. 2005).     

Building urban gas process safety management (UG-PSM) system: Based on root cause analysis with 160 urban gas accidents in China

Urban safety is significantly impacted by the complexity of urban gas accidents. Although China has put forward the goal of “zero fatalities in accidents” for urban gas, unfortunately, the root causes of the unsound safety culture and imperfect safety management system of urban gas enterprises remain unresolved. Therefore, statistical analysis and 24Model analysis of 160 urban gas accidents in mainland China were performed to investigate the proximate causes of the accidents and the current situation of urban gas safety. The CCPS's risk-based process safety elements were used to identify potential deficiencies in the current urban gas process safety management (UG-PSM). During the analysis, it was observed that insufficient implementation of concealed danger investigation and rectification accounted for 76%, which is the primary proximate cause of urban gas accidents. Stakeholder outreach is the most under-represented competency in urban gas safety management. Based on the results, a novel framework for the UG-PSM system was constructed, and the theory of urban gas safety management was further improved. Furthermore, we evaluated the matching degree between UG-PSM elements and the existing measures of the government, urban gas associations, third-party organizations, and urban gas enterprises. Finally, we analyzed the feasibility, challenges, and development directions of the UG-PSM system. This study establishes a foundation for researchers and practitioners in the future research and practice of urban gas process safety and provides theoretical guidance for preventing high-incidence accidents of urban gas in China.     

Radiocaesium accumulation in stemwood: integrated approach at the scale of forest stands for contaminated Scots pine in Belarus

Twenty years after the Chernobyl accident, root uptake from the surface layers of contaminated forest soils plays a major role in radiocaesium ((137)Cs) transfer to the trees and accumulation in perennial compartments, including stemwood. Trustworthy long-term predictions (modelling) of stemwood contamination with (137)Cs should accordingly be based on a reliable picture of this source-sink relationship. Considering the complexity of the processes involved in (137)Cs cycling in forest stands, elementary ratios like transfer factors (TF) were shown to be not very relevant for that purpose. At the tree level, alternatives like the wood immobilisation potential (WIP) have therefore been proposed in order to quantify the current net (137)Cs accumulation in stemwood. Our objective was here to compare WIP values determined for a series of contaminated forest stands in Belarus with the corresponding pools of (137)Cs available in the soil for root uptake. The comparison reveals that both indices are quite proportional, whatever the forest ecosystem features. This corroborates the relevancy of WIP as an indicator of the current (137)Cs root uptake by the trees, which could accordingly help to improve the existing models of (137)Cs cycling and the long-term management of contaminated forest ecosystems.