Earth before life

Background

A recent study argued, based on data on functional genome size of major phyla, that there is evidence life may have originated significantly prior to the formation of the Earth.

Results

Here a more refined regression analysis is performed in which 1) measurement error is systematically taken into account, and 2) interval estimates (e.g., confidence or prediction intervals) are produced. It is shown that such models for which the interval estimate for the time origin of the genome includes the age of the Earth are consistent with observed data.

Conclusions

The appearance of life after the formation of the Earth is consistent with the data set under examination.

Reviewers

This article was reviewed by Yuri Wolf, Peter Gogarten, and Christoph Adami.     

Survival of the fittest before the beginning of life: selection of the first oligonucleotide-like polymers by UV light

Background  

A key event in the origin of life on this planet has been formation of self-replicating RNA-type molecules, which were complex enough to undergo a Darwinian-type evolution (origin of the "RNA world"). However, so far there has been no explanation of how the first RNA-like biopolymers could originate and survive on the primordial Earth.     

Genetic analysis of the effect of zinc deficiency on Arabidopsis growth and mineral concentrations

Aims

Zinc deficiency is a common micronutrient deficiency in plants growing in many different regions of the world and is associated with disturbances in uptake and accumulation of mineral nutrients. Despite many published data on physiological factors affecting ion accumulation in Zn deficient plants, there is very little information about the genetic factors underlying this. We aim to identify genetic loci involved in mineral accumulation and plant performance under Zn deficiency.

Methods

Genetic loci were identified using the genetically segregating Ler × Cvi recombinant inbred line (RIL) population grown under Zn deficient conditions. Lines were analysed for the concentrations of Zn, Fe, Mn, K, Ca, Mg, P, Cu, S and Al in shoot dry matter. The same was done for the same lines grown under Zn sufficient conditions.

Results

We found considerable heritable variation for most mineral concentrations. In general, there was a positive correlation between mineral concentrations. For Zn only condition-dependent QTLs were identified, while for most other mineral concentrations both condition-dependent and -independent QTLs were identified. Several QTLs co-localize, including co-localization to loci controlling shoot biomass and to mineral concentration loci found previously in this and other RIL populations.

Conclusions

There are different genetic loci controlling Zn accumulation under deficient and sufficient Zn supply. Only for few minerals, their accumulation is controlled by Zn-supply-specific loci.     

Effects of life events and stress on neutrophil functions in elderly men

Background

Psychological stress or life events might significantly decrease neutrophil function in elderly individuals and lead to infectious diseases. However, relationships between these factors have not been examined in detail. We investigated the relationships between neutrophil function measured using the nitroblue tetrazolium (NBT) reduction test and measurements of psychological stress and life events among 81 men aged over 60?years.

Results

The numbers and scores for life events were significantly higher (p?Conclusions Chronic psychological stress due to life events decreases neutrophil functions among elderly men.     

Exergy-based accounting for land as a natural resource in life cycle assessment

Purpose

In life cycle assessment (LCA), literature suggests accounting for land as a resource either by what it delivers (e.g., biomass content) or the time and space needed to produce biomass (land occupation), in order to avoid double-counting. This paper proposes and implements a new framework to calculate exergy-based spatial explicit characterization factors (CF) for land as a resource, which deals with both biomass and area occupied on the global scale.

Methods

We created a schematic overview of the Earth, dividing it into two systems (human-made and natural), making it possible to account for what is actually extracted from nature, i.e., the biomass content was set as the elementary flow to be accounted at natural systems and the land occupation (through the potential natural net primary production) was set as the elementary flow at human-made systems. Through exergy, we were able to create CF for land resources for these two different systems. The relevancy of the new CF was tested for a number of biobased products.

Results and discussion

Site-generic CF were created for land as a resource for natural systems providing goods to humans, and site-generic and site-dependent CF (at grid, region, country, and continent level) were created for land as a resource within human-made systems. This framework differed from other methods in the sense of accounting for both land occupation and biomass content but without double-counting. It is set operationally for LCA and able to account for land resources with more completeness, allowing spatial differentiation. When site-dependent CF were considered for land resources, the overall resource consumption of certain products increased up to 77 % in comparison with site-generic CF-based data.

Conclusions

This paper clearly distinguished the origin of the resource (natural or human-made systems), allowing consistent accounting for land as a resource. Site-dependent CF for human-made systems allowed spatial differentiation, which was not considered in other resource accounting life cycle impact assessment methods.     

Addressing the effect of social life cycle assessments

Purpose

In the recently published ??Guidelines for social life cycle assessment of products??, it is stated that the ultimate objective of developing the social life cycle assessment (SLCA) is to promote improvements of social conditions for the stakeholders in the life cycle. This article addresses how the SLCA should be developed so that its use promotes these improvements.

Methods

Hypotheses of how the use of SLCA can promote improvement of social conditions in the life cycle are formulated, after which theories and empirical findings from relevant fields of research are used to address the validity of these hypotheses.

Results

Three in some cases potentially overlapping SLCA approaches are presented, assumed to create a beneficial effect in the life cycle in different ways. However, empirical and theoretical findings show that the beneficial effects proposed to arise from the use of each of these three approaches may all be problematic. Some of these problems may be mitigated through methodological modifications.

Conclusions

Given the significant problems in relation to creating an effect through the use of the SLCAs, and given the significant practical problems in applying the SLCAs, it is questioned whether the development of SLCA is a fruitful approach for improving social conditions in the product life cycle.     

Ecodesign of PVC packing tape using life cycle assessment

Purpose

Polymer materials play an important role in the improvement and quality of life. However, due to their persistence in the environment, polymer materials may be harmful to the ecosystems. According to the European Directive on Packaging and Packaging Waste, management of these wastes should include prevention of their generation as a priority. The main motivation for employing ecodesign of a product is to reduce both raw material consumption and waste generation through a good initial design.

Methods

In this study, life cycle assessment (LCA) was applied to the design of printed PVC plastic packing tape in order to reduce its environmental impact. LCA software GaBi4.4^® was used to determine the PVC packing tape life cycle stage with the highest environmental impacts.

Results and discussion

LCA results showed that PVC film manufacture was the stage with the highest impact. It was therefore reasonable to assume that packing tape manufactured with material other than PVC could have reduced environmental impact, and LCA was used to evaluate this hypothesis. When using Kraft paper or polypropylene plastic packing tape, the weighted impacts were reduced by 36.3 and 39.9 %, respectively.

Conclusions

PVC plastic packing tape has been redesigned with the aim of reducing waste and raw material consumption. LCA results showed that a suitable option for reducing life cycle environmental impact is to use alternative film materials. Kraft paper and polypropylene plastic packing tape were found to give lower values of almost all environmental impact indexes and normalized and weighted impacts.     

Montmorillonite protection of an UV-irradiated hairpin ribozyme: evolution of the RNA world in a mineral environment

Background

The hypothesis of an RNA-based origin of life, known as the "RNA world", is strongly affected by the hostile environmental conditions probably present in the early Earth. In particular, strong UV and X-ray radiations could have been a major obstacle to the formation and evolution of the first biomolecules. In 1951, J. D. Bernal first proposed that clay minerals could have served as the sites of accumulation and protection from degradation of the first biopolymers, providing the right physical setting for the evolution of more complex systems. Numerous subsequent experimental studies have reinforced this hypothesis.

Results

The ability of the possibly widespread prebiotic, clay mineral montmorillonite to protect the catalytic RNA molecule ADHR1 (Adenine Dependent Hairpin Ribozyme 1) from UV-induced damages was experimentally checked. In particular, the self-cleavage reaction of the ribozyme was evaluated after UV-irradiation of the molecule in the absence or presence of clay particles. Results obtained showed a three-fold retention of the self-cleavage activity of the montmorillonite-protected molecule, with respect to the same reaction performed by the ribozyme irradiated in the absence of the clay.

Conclusion

These results provide a suggestion with which RNA, or RNA-like molecules, could have overcame the problem of protection from UV irradiation in the RNA world era, and suggest that a clay-rich environment could have favoured not only the formation of first genetic molecules, but also their evolution towards increasingly complex molecular organization.

     

Isotopic fractionation of Zn in tomato plants suggests the role of root exudates on Zn uptake

Aims

Phytosiderophore-chelated Zn can be absorbed in grasses. Root exudates of dicotyledonous plants can mobilize soil Zn but it is unclear how this affects Zn bioavailability. Stable Zn isotope shifts can indicate exudate-facilitated Zn uptake, since complexation of Zn²⁺ by organic ligands in solution yields a small, but detectable, enrichment of the heavy Zn isotope due to thermodynamic fractionation.

Methods

Tomato seedlings were grown in resin-buffered nutrient solution in which free Zn²⁺ concentrations are buffered, in a factorial design of two Zn levels and two solution volumes. The latter factor allowed altering the exudate concentrations in the solution. Dissolved Cu concentrations in the resin buffered system were used as a sensitive index of metal mobilization resulting from root activity. In addition, seedlings were grown in Zn deficient soil with and without Zn addition.

Results

The dissolved Cu concentration increased with Zn deficiency and was highest at the lowest solution volume, suggesting metal mobilization by root exudates. At low Zn supply, Zn in the plant was enriched in heavy Zn (⁶⁶Zn) and this was most pronounced at small solution volume. Similarly, Zn deficiency in soil enriched tomato shoot Zn with heavy isotope in this plant.

Interpretation

Zinc deficiency increases the contribution of Zn-exudate complexes, which are enriched in the heavy isotope compared to the free ion, to Zn uptake by transporting Zn from the bulk solution or soil to the roots where they likely dissociate and release Zn²⁺.     

Service life of the dwelling stock in Spain

Purpose

Service life of buildings is an essential parameter to evaluate its operational impact in life cycle assessment (LCA). Although most studies assume building service life about 75 to 100 years since no reliable data are available, its accurate quantification is still an unresolved work. To avoid wrong generalizations, the determination of the service life of buildings according to the characteristics of every region is required.

Methods

Life table, a methodology traditionally used in demographic studies, has been used in this paper to estimate the service life of buildings. This methodology has been applied to the dwelling stock of Spain for each of its 19 regions. Data acquisition and sources have been pointed out. The building obsolescence has been considered in the moment that they are in a ruinous state.

Results and discussion

Life table of buildings showed that the average service life of a residential building constructed in 2001 in Spain was expected to be 80 years. Significant different results of service life among regions were found, from 54 years for a building in Ceuta to 95 years in La Rioja. It also showed that 50 % of total Spanish dwellings are younger than 30 years, and they are expected to reach the ruinous state in 2063 to 2081.

Conclusions

Life table applied to buildings allows determining their service life. Its quantification is based on the buildings census, given by official institutions. Building census has to consider the year of construction and the state of conservation of the building to be applied in buildings' life table. Building service life can be used in LCA, renovation and deconstruction of the building stock, and future construction and demolition debris management.     

Energy-dispersive X-ray fluorescence spectrometry as a tool for zinc, iron and selenium analysis in whole grain wheat

Background and aims

Crop biofortification programs require fast, accurate and inexpensive methods of identifying nutrient dense genotypes. This study investigated energy-dispersive X-ray fluorescence spectrometry (EDXRF) for the measurement of zinc (Zn), iron (Fe) and selenium (Se) concentrations in whole grain wheat.

Methods

Grain samples were obtained from existing biofortification programs. Reference Zn, Fe and Se concentrations were obtained using inductively coupled plasma optical emission spectrometry (ICP-OES) and/or inductively coupled plasma mass spectrometry (ICP-MS). One set of 25 samples was used to calibrate for Zn (19–60?mg?kg^–1) and Fe (26–41?mg?kg^–1), with 25 further samples used to calibrate for Se (2–31?mg?kg^–1 ). Calibrations were validated using an additional 40–50 wheat samples.

Results

EDXRF limits of quantification (LOQ) were estimated as 7, 3 and 2?mg?kg^–1 for Zn, Fe, and Se, respectively. EDXRF results were highly correlated with ICP-OES or -MS values. Standard errors of EDXRF predictions were ±2.2?mg Zn kg^–1, ±2.6?mg Fe kg^–1, and ±1.5?mg Se kg^–1.

Conclusion

EDXRF offers a fast and economical method for the assessment of Zn, Fe and Se concentration in wheat biofortification programs.     

Review and downscaling of life cycle decision support tools for the procurement of low-value products

Purpose

In this article, we analyze how environmental aspects can be derived from life cycle management instruments for procurement decisions of low-value products. For our analysis, we chose the case of operating room textiles. The review includes the life cycle management instruments: life cycle assessment, environmental labels, and management systems applied within the textile industry. We do so in order to identify the most important environmental decision criteria based on which the procurer of low-value products can decide for the most environmentally friendly option.

Methods

We conducted a systematic literature search in the relevant literature databases. We critically evaluate the identified life cycle assessment studies for sound methodology, verifiability, completeness, and actuality. Based on this review, we analyze and compare the results of the three most comprehensive studies in more detail and derive the most important environmental aspects of operating room textiles. In a second step, we extend the operational perspective via the strategic perspective, namely environmental management systems and further existing life cycle instruments such as eco-labels. We then synthesize the gathered information into a decision vector. Finally, we discuss how the gathered data can be further exploited and give suggestions for a more sophisticated assessment.

Results and discussion

The review of the existing life cycle assessments on operating room textiles showed that procurers should not base their decisions exclusively on existing life cycle assessments. In addition to problems such as methodological weakness, incompleteness, outdated data, and poor verifiability, the information provided is far too complex to prepare procurement decisions regarding low-value products. Furthermore, the results for the textiles assessed in the existing life cycle assessments are not necessarily transferrable to the textiles considered by the procurer because of restrictive assumptions. Therefore, it is necessary to downscale the available information and synthesize it in an applicable decision support tool. Our decision vector consists of the key environmental aspects water, CO₂, energy, and waste and is completed by environmental management systems, eco-labels, and the countries of origin that matters for environmental and social aspects as well.

Conclusions

The decision vector supports procurers when considering environmental aspects in procurement decisions and provides a mechanism for balancing the information between overcomplexity and oversimplification. Therefore, it should be the basis for future development of an eco-label for operating room textiles.     

Evaluating the Sustainability SWOT as a streamlined tool for life cycle sustainability assessment

Purpose

From a management perspective, there are two main issues in the life cycle sustainability assessment framework which require further work: (1) the approaches to quicken the resource-consuming inventory and assessment process and (2) the easy-to-understand communication of the results. This study aims at contributing to these needs for quicker and cost-efficient ways to draft strategies that include the life cycle perspective and encompasses all three dimensions of sustainability in an easily communicable way. The focus of the study is on a streamlined, rapid assessment the tool proposed by Pesonen (2007) called the Sustainability SWOT (Strengths, Weaknesses, Opportunities, Threats) and on the empirical testing of whether or not it is understood in the corporate world and if it leads to concrete changes in either strategic- or operative-level activities.

Methods

The data for the research were empirically collected from a survey targeted to representatives of organizations having used the Sustainability SWOT within the last 5 years. The primary findings, i.e., the generated changes or improvements, were reflected in the various levels of cooperation in a network (along the value chain, in end users, in the institutional framework).

Results and discussion

The results of the analyses of both the usability of the Sustainability SWOT in business as well as the suggested assessment framework leading to any actual changes were promising. It is encouraging that the streamlined approach tailored according to the logic of business decision-makers (i.e., inclusion of the SWOT) is able to find the acceptance and understanding of that vital group. Remarkably, many changes were initiated—not only at an operative level but also at a strategic level and in the entire value chain—by carrying out an exercise such as the Sustainability SWOT.

Conclusions

The Sustainability SWOT has proven to be usable and able to generate changes and improvements along the value chain and, in some cases, in the institutional context as well.     

Biofortification of zinc in wheat grain by the application of sewage sludge

Background and aims

Increasing the concentrations of the essential micronutrient Zn in staple crops like grain is desirable for human nutrition. We investigated the long-term ability of municipal treatment works sewage sludge, liquid sewage sludge and ZnCO₃ applied to soils to increase Zn in in wheat grain (Triticum aestivum L.) in a number of field experiments conducted on different soils.

Methods

We used six long-term field experiments that were set up on contrasting soils in England and the target applications were built up between 1994 and 1997. Topsoil samples and harvested grain samples were taken and air dried in 1999, 2001, 2003 and 2005. Relationships between grain Zn concentrations and soil properties and changes with time were examined.

Results

Wheat grain Zn concentrations increased with soil Zn concentrations in a similar log-log relationship with all of the Zn sources tested. Comparing total or extractable Zn in soil as explanatory factors showed little benefit of using extractable Zn measurements to predict grain concentrations over total Zn. Additional factors such as soil pH or organic carbon did not explain much more of the variation in grain Zn in our experiments. However, grain Zn concentrations did not respond at all at a site with pH 7.7.

Conclusions

Sewage sludge applications to soil can increase grain Zn concentrations for at least 2 to 8?years after application and has similar effectiveness to ZnCO₃.     

Analysis of the link between a definition of sustainability and the life cycle methodologies

Purpose

It has been claimed that in order to assess the sustainability of products, a combination of the results from a life cycle assessment (LCA), social life cycle assessment (SLCA) and life cycle costing (LCC) is needed. Despite the frequent reference to this claim in the literature, very little explicit analysis of the claim has been made. The purpose of this article is to analyse this claim.

Methods

An interpretation of the goals of sustainability, as outlined in the report Our Common Future (WCED 1987), which is the basis for most literature on sustainability assessment in the LCA community, is presented and detailed to a level enabling an analysis of the relation to the impact categories at midpoint level considered in life cycle (LC) methodologies.

Results

The interpretation of the definition of sustainability as outlined in Our Common Future (WCED 1987) suggests that the assessment of a product's sustainability is about addressing the extent to which product life cycles affect poverty levels among the current generation, as well as changes in the level of natural, human and produced and social capital available for the future population. It is shown that the extent to which product life cycles affect poverty to some extent is covered by impact categories included in existing SLCA approaches. It is also found that the extent to which product life cycles affect natural capital is well covered by LCA, and human capital is covered by both LCA and SLCA but in different ways. Produced capital is not to any large extent considered in any of the LC methodologies. Furthermore, because of the present level of knowledge about what creates and destroys social capital, it is difficult to assess how it relates to the LC methodologies. It is also found that the LCC is only relevant in the context of a life cycle sustainability assessment (LCSA) if focusing on the monetary gains or losses for the poor. Yet, this is an aspect which is already considered in several SLCA approaches.

Conclusions

The current consensus that LCSA can be performed through combining the results from an SLCA, LCA and LCC is only partially supported in this article: The LCSA should include both an LCA and an SLCA, which should be expanded to better cover how product life cycles affect poverty and produced capital. The LCC may be included if it has as a focus to asses income gains for the poor.     

Inclusion of discard assessment indicators in fisheries life cycle assessment studies. Expanding the use of fishery-specific impact categories

Purpose

The main purpose of this article is to propose specific discard indexes for their development in fisheries life cycle assessment (LCA). The objective of these is to characterize and standardize discards in worldwide fisheries.

Methods

The global discard index (GDI) is intended to be an easily understood index whose use is extendible to any fishery in the world. It is presented as a dynamic index that aims to characterize and standardize discard rates between fisheries by direct comparison with the global discard rates reported periodically by FAO. Furthermore, a simplified approach excluding characterization is presented for scenarios in which the data quality linked to discards is poor. Two additional indicators, survival rate of discards and slipping, are proposed to improve the reporting and quantification of biomass waste by fishing vessels.

Results

GDI implementation, together with two other fishery-specific impact categories, showed remarkable differences in the environmental impacts of several fishing fleets when compared with the obtained results for conventional impact categories. Results for the conventional categories were strongly influenced by the energy use in the fishery, while results obtained for fishery-specific categories presented variable trends due to the dependence on a wider range of factors. GDI inclusion favored direct comparison with worldwide average discard rates on a time scale basis, from a wet weight or a net primary productivity perspective, depending on the selected approach.

Conclusions

Proposed indicators achieved the important objective of integrating discard data as a fishery-specific impact in fishery LCAs, increasing the benefits of implementing LCA in fisheries assessment. Specific advantages of these indicators include assessing changes in capture and landing composition, evaluating the selectivity of the fishing gears, and monitoring the behavior of fisheries in a normalized context respect to other fisheries. GDI was identified as an adequate methodological improvement for regular use in fisheries LCA. Future developments GDI include its harmonization for inclusion in damage assessment.     

Contributions of root uptake and remobilization to grain zinc accumulation in wheat depending on post-anthesis zinc availability and nitrogen nutrition

Background and aims

Whether root Zn uptake during grain filling or remobilization from pre-anthesis Zn stores contributes more to grain Zn in wheat is subject to an on-going debate. This study investigated the effects of N nutrition and post-anthesis Zn availability on the relative importance of these sources.

Methods

Durum wheat plants were grown in nutrient solution containing adequate Zn (0.5?μM) and three different N levels (0.5; 1.5; 4.5?mM). One third of the plants were harvested when they reached anthesis. One half of the remaining plants were grown to maturity with adequate Zn, whereas the Zn supply to the other half was discontinued at anthesis. Roots, straw and grains were harvested separately and analyzed for Zn and N.

Results

Depending on the N supply, Zn remobilization from pre-anthesis sources provided almost all of grain Zn when the Zn supply was withheld at anthesis; otherwise up to 100?% of grain Zn could be accounted for by Zn taken up post-anthesis. By promoting tillering and grain yield and extending the grain filling, higher N supply favored the contribution of Zn uptake to grain Zn accumulation.

Conclusion

Remobilization is critical for grain Zn accumulation when Zn availability is restricted during grain filling. However, where root uptake can continue, concurrent Zn uptake during grain development, favored by higher N supply, overshadows net remobilization.     

Metal concentration and metal mass of metallicolous, non metallicolous and serpentine Noccaea caerulescens populations, cultivated in different growth media

Aims

Evaluate the genetic and environmental variability of metal concentration and metal mass of Noccaea caerulescens, from metalliferous (MET), non metalliferous (NMET) and serpentine (SERP) soils.

Methods

18 populations were cultivated in 18 different growth conditions, such as a soil mine tailing, soils amended with zinc (Zn), cadmium (Cd) and nickel (Ni) salts (in mixtures or in monometallic salts) and a hydroponic solution with two Zn concentrations.

Results

MET populations had Zn concentrations lower than NMET and SERP in the different soils but higher Cd mass (the product of aerial biomass and foliar metal concentration). SERP had the highest Ni concentration and Ni mass values. The addition of Cd or Ni to a Zn-contaminated soil significantly decreases Zn concentration. In hydroponics, MET and NMET had equivalent Zn concentrations but these were three times higher than those obtained in soil experiments. Zn mass of NMET was significantly lower than MET with the latter having Zn mass values largely above those obtained in mine soil.

Conclusions

Results showed a large heterogeneity of responses among populations depending on the substrate used, and it was not possible to correctly assign a single population to its accurate origin with only one experiment. Finally, data on metal concentration obtained in culture soils are closer to those in field soils than those from hydroponics so that they could give a more accurate information on the accumulating capacity of Noccaea caerulescens and its use in phytoextraction of metals in field conditions.