Insignificant acute toxicity of TiO2 nanoparticles to willow trees

Background, aim, and scope  

Manufactured nanoparticles (MNP) are expected to increase in production in near future. In response, their environmental fate and effects are intensively studied. Phytotoxicity of some types of nanoparticles has been observed for annual species in the seed germination and root elongation test. Yet, no results of toxicity tests with trees have been reported. Woody species, dominant in many ecosystems, may be vulnerable in particular due to the large porous wood compartment.     

Mobility of trace metals associated with urban particles exposed to natural waters of various salinities from the Gironde Estuary, France

Background, aim and scope  Urban systems are hot spots of environmental pollution caused by manifold anthropogenic activities generating traffic-related, industrial and domestic emissions. Besides air, soil and groundwater pollution, pollution of surface water systems is of major concern because they are often (ab)used to export waste of various consistence out of urban areas and become contaminated on varying scales. The Gironde Estuary (southwest France) is affected by various anthropogenic contaminations derived from historic polymetallic pollution mainly due to former mining and ore-treatment and, additionally, from agriculture and urban areas. Although detailed knowledge is available on the impact of mining and anthropogenic activities on the water quality of the Gironde Estuary, almost nothing is known on the urban impact, even though the Garonne Branch which is one tributary of the Gironde system crosses the large urban agglomeration of Bordeaux. The present work links urban geochemistry and estuary research and aims at evaluating the mobility of potentially toxic trace elements (Cd, Cu, Zn, V, Co, Mo, Pb) associated with urban particles under estuarine conditions owing to the particles' role as potential vectors transporting urban pollutants into the estuary. For this, environmentally available fractions of trace elements in representative urban particles (urban dust, road sediment, riverbank sediment, construction materials) from the city of Bordeaux were extracted by natural estuarine waters of varying salinities and compared to commonly applied HNO₃ extractions. Materials and methods  For the assessment of the urban particles' contribution to the pollution of the Gironde/Garonne system, various particle types were sampled in Bordeaux: road sediments, urban bulk deposition, construction materials (concrete, asphalt, tile and gravel) and flood sediments. Potentially environmental available fractions of Cd, Cu, Zn, V, Co, Mo and Pb were extracted by means of concentrated HNO₃, estuarine freshwaters and waters of two different salinities (S = 15 and S = 31). Analysis of trace elements was carried out by means of quadrupole inductively coupled plasma-mass spectrometry. Furthermore, single particles from road sediments were characterised with scanning electron microscopy (SEM). Results  SEM analysis clearly showed that some particles contained fairly high concentrations of potentially toxic trace elements. Extractions of materials investigated by varying acidities and salinities documented that the potentially bioavailable fractions extracted by concentrated HNO₃ may cover wide concentration ranges. Natural estuarine waters of various salinities (S = 0.5; S = 15; S = 31) extracted high proportions of Co, Ni, Cu, Zn and Cd from urban particles, especially for high-salinity water (S = 31). Extractions with freshwater revealed the lowest concentrations of desorbed trace elements. Particulate Mo, Pb and V showed similar or lower mobility in saline water compared with freshwater, depending on the sample type. Discussion  Trace element mobility in estuarine waters varied according to the type of urban particles and depended on salinity for Co, Ni, Cu, Zn and Cd. This is of high importance for towns located directly at the coast or for cities like Bordeaux, where water courses crossing the agglomerations are connected to saline water masses. Since trace elements desorbed from particles in saline waters may become highly bioavailable, they bear a potential risk for organisms. Comprehensive studies on the behaviour of urban particles in estuarine waters and the related potential environmental impact are still missing. Conclusions  Saline waters mobilise relatively high amounts of Co, Ni, Cu, Zn and Cd from urban particles suggesting considerable metal fluxes from riverine urban systems into coastal waters. Although estimates of trace metal inputs by urban bulk deposition (urban dust) and other types of urban particles are preliminary for Bordeaux and may bear important uncertainties due to several assumptions and extrapolation to the annual timescale, the orders of magnitude are probably realistic. Thus, these fluxes are not negligible and need (1) further and improved observation and (2) to be taken into account in both mass budgets at the estuary scale and emission control strategies. Recommendations and perspectives  New approaches combining geochemical and mineralogical characterisation of single urban particle types help identify their role in metal emission into the environment and develop potential limitation strategies (e.g. the ban of priority pollutants in tyres, etc.). Therefore, prioritisation of urban particle sources in terms of fluxes, reactivity of associated pollutants and feasibility of emission reduction is strongly recommended. Coastal cities should integrate extractions of urban particles with saline water into their environmental monitoring programs owing to the fact that saline conditions might cause efficient desorption of potentially toxic trace elements. In continental cities, winter salting is likely to induce intense mobilisation of metals from road sediments that may then reach the aquatic environment, instead of being retained in runoff decantation reservoirs followed by subsequent disposal/treatment with road sediments. However, also particles from continental cities reach coastal waters via rivers and have to be assessed with respect to trace metal desorption under various salinities. There is a strong need for the quantification of fluxes and for the identification of carrier phases and reactivity of metals exported from urban areas to aquatic systems.     

Understanding the mechanisms of soil water repellency from nanoscale to ecosystem scale: a review

Journal of Soils and Sediments - Soil water repellency (SWR) can interrupt water infiltration that may decline plant growth and potentially trigger soil erosion. Until now research has been mainly...     

QTLs for malting flavour component associated with pre-harvest sprouting susceptibility in barley (Hordeum vulgare L.)

Lipoxygenase (LOX) is a key factor affecting quality of beer in terms of foam stability and flavour. Low LOX content is a desirable trait for malting quality. A doubled haploid (DH) population was made from a cross of Australian malting barley Stirling and Canadian malting barley Harrington and mapped with 513 molecular markers. The 120 DH lines with their parents were planted in field trials and the harvested grains were micro-malted for analysis of LOX content in two consecutive years. LOX content was controlled by both genetic effects and environment conditions. Three QTLs were consistently detected. One QTL flanked by the markers E6216 and SCssr03907 at the telomere region of chromosome 5HL contributed 39% of genetic variation in LOX content. The second QTL close to the centromere region of chromosome 5H accounted for 17% of genetic variation. A minor QTL on chromosome 2H explained 6% of genetic variation but was significant in both years. The Australian variety Stirling contributed to higher LOX content for the three QTLs. The two QTLs mapped at chromosome 5H for LOX content coincided with the QTLs for seed dormancy/pre-harvest sprouting from the same population. The pre-harvest sprouting susceptible alleles were associated with low LOX content, which indicated that the low LOX QTL from the Canadian malting barleys are only useful in the barley growing areas where the pre-harvest sprouting risk is low. New genetic sources for low LOX should be exploited in different germplasm with different mechanisms.     

Scoring of the extent and intensity of carp (Cyprinus carpio) skin changes made by cormorants (Phalacrocorax carbo sinensis): relationship between morphometric and histological indices

Cormorants cause damage to fish in aquaculture not only by consuming large number of fish but also by wounding them. Quantification of the actual damage in fish induced by wounding is important for reliable estimations of the overall loss in aquaculture caused by cormorants. In this study, specimens of mirror and scaly carp (Cyprinus carpio L.) injured by attacks of great cormorant (Phalacrocorax carbo L.) were collected from the ??E?ka?? fish farm in Serbia. Surfaces of superficial and open subepithelial wounds (expressed as a percent of the total body surface), estimated by computer-assisted image analysis, had mean values 10.66?±?1.86 and 0.85?±?0.90, respectively. Histological evaluation of wounds was performed by two scoring systems: system proposed by Bernet et al. (J Fish Dis 22:25?C34, 1999) and modified system described by Wahli et al. (Aquaculture 225:371?C386, 2003). The most frequent histopathological changes were disturbed epidermal structure and surface cell morphology and increased number of club cells (on more than 75% of specimens); increased number of melanocytes and their distribution in different layers in dermis; and enlarged hypodermis (more than 80% of samples) and myolysis (50% of samples). Comparison of wounds?? surfaces (surface of superficial injures) and histopathological changes, estimated by two scoring systems, revealed significant positive correlation. Bernet??s scoring system showed higher correlation coefficients, when compared with the modified Wahli??s scoring system.     

Annual variation in predation and dispersal of Arolla pine (Pinus cembra L.) seeds by Eurasian red squirrels and other seed-eaters

Seed predation and dispersal are key processes in the survival and distribution of plant species. Many animals cache seeds for later consumption, and, failing to recover some of these seeds, act as seed dispersers, influencing post-dispersal seed and seedling survival. Both animal and plant benefit from scatterhoarding and natural selection of seed characteristics and adaptations of seed predators (and dispersers) is one of the most important examples of co-evolution and mutualism. We studied the producer–consumer Arolla pine (Pinus cembra)–red squirrel (Sciurus vulgaris) system in a subalpine forest in the Italian Alps. Arolla pine produced large seed-crops (masting) at irregular intervals, followed by years with poor or moderate seed production. Squirrel density fluctuated in synchrony with the food resource, eliminating the time-lag normally present when resources are produced in pulses. In all years except 2009 (a mast-crop year), all Arolla pine cones were harvested (their seeds consumed and/or cached) by September to late October by different species. Both squirrels and nutcrackers (Nucifraga caryocatactes) fed on seeds, and their relative pre-dispersal predation rates (on cones in the canopy) differed between years. Overall, nutcrackers consumed more seeds between July and October than squirrels, but in 1 year squirrels took the largest number of seeds. Pre-dispersal seed predation by squirrels tended to be lower in years with large seed-crop size and there was a positive correlation, over the entire study period, between density of recovered hoards and Arolla pine seed density of the previous year. We conclude that (i) squirrels and nutcrackers are important pre-dispersal seed predators and seeds dispersers; (ii) squirrels are also post-dispersal seed predators, and (iii) the proportion of cached seeds consumed by squirrels increased with the size of the Arolla pine seed-crop, suggesting that red squirrel is a conditional mutualistic scatterhoarder of Arolla pine seeds.     

Prediction of yield and the contribution of legumes in legume-grass mixtures using field spectrometry

Productivity and botanical composition of legume-grass swards in rotation systems are important factors for successful arable farming in both organic and conventional farming systems. As these attributes vary considerably within a field, a non-destructive method of detection while doing other tasks would facilitate more targeted management of crops and nutrients in the soil–plant–animal system. Two pot experiments were conducted to examine the potential of field spectroscopy to assess total biomass and the proportions of legume, using binary mixtures and pure swards of grass and legumes. The spectral reflectance of swards was measured under artificial light conditions at a sward age ranging from 21 to 70 days. Total biomass was determined by modified partial least squares (MPLS) regression, stepwise multiple linear regression (SMLR) and the vegetation indices (VIs) simple ratio (SR), normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and red edge position (REP). Modified partial least squares and SMLR gave the largest R ² values ranging from 0.85 to 0.99. Total biomass prediction by VIs resulted in R ² values of 0.87–0.90 for swards with large leaf to stem ratios; the greatest accuracy was for EVI. For more mature and open swards VI-based detection of biomass was not possible. The contribution of legumes to the sward could be determined at a constant biomass level by the VIs, but this was not possible when the level of biomass varied.     

Analyses of stand structure as a tool for silvicultural decisions — a case study in a Quercus petraea — Sorbus torminalis stand

The study applies structural indices using the example of an oak (Quercus petraea (Matt.) Liebl.) — chequer tree (Sorbus torminalis (L.) Crantz) stand in order to derive recommendations for the silvicultural treatment of Chequer trees. The investigated stand, located in the northern part of Bavaria, comprises eight tree species and four shrub species. Various indices were used to analyse the stand structure and the crown coverage frequency. It was shown that chequer trees, which are presently of high economic interest, are strongly oppressed in the upper layer and almost completely missing in the lower layers of the stand. The possible reasons for this finding and alternatives for the further management of the stand are discussed. Persistent and repeated thinnings in order to ensure sufficient crown development of the chequer trees seem to be essential for their survival.     

Taking it to the next level: Trophic transfer of marker fatty acids from basal resource to predators

Fatty acid (FA) analysis is used increasingly to investigate the trophic structure of soil animal food webs as the technique allows separation of the role of detrital resources such as bacteria, fungi and plant material for consumer nutrition. The applicability of FAs as biomarkers for different diets has been verified for Collembola and Nematoda. However, for the analysis of whole food webs it is crucial to know whether marker FA are valid for different taxa and whether they are transferred along the food chain to higher trophic levels, i.e. predators. Top-predators are integrators of lower level energy fluxes in food webs; therefore analysis of their FAs may allow to identify trophic pathways and to separate bacterial vs. fungal based energy channels. Chilopoda and Arachnida are among the main predators in soil food webs. Our aim was to test the applicability of marker FAs for these two predator taxa and to verify the trophic transfer of marker FAs of different basal resources via first order consumers into predators, i.e. over three trophic levels. Therefore, we investigated the transfer of FAs from different basal resources [fungi (Chaetomium globosum), plant leaf litter (Tilia europaea), Gram-positive (Bacillus amyloliquefaciens) and Gram-negative bacteria (Stenotrophomonas maltophilia)] via Collembola (Heteromurus nitidus) as first order consumers into predators [Lithobius forficatus (Chilopoda) and Pardosa lugubris (Arachnida)]. Fatty acid profiles of predators of food chains with different basal resources differed significantly. Marker FAs of basal resources were clearly detectable in predators, suggesting that FA analysis allows to separate trophic channels of soil food webs. By reflecting basal resources, FAs of predators allow tracking energy/resource fluxes through the food web and thereby clarifying the relative importance of bacterial vs. fungal vs. plant resources for soil animal food webs.