Several cover crops (CCs) exert allelopathic effects that suppress weed growth. The aim of the present study was to evaluate the effects of aqueous extracts containing different concentrations 0, ...0.5, 1, 2.5, 5, 7.5 and 10% (
/
) of Brassicaceae CCs (
and of the CCs
and
on germination and early growth of
L. The allelopathic effects were species and concentration-dependent.
, for example, caused the greatest potential to inhibit germination, shoot, radicle length and fresh seedling weight, whereas
and
inhibited germination and early growth of
only at concentrations ≥7.5%. In contrast, no inhibition was observed when aqueous extracts of
and
were added at any of tested concentration. Liquid chromatography-tandem mass spectrometry detected 15 phenolic compounds in Brassicaceae CCs with the highest content (µg/g) of vanillin (48.8), chlorogenic acid (1057), vanilic acid (79), caffeic acid (102.5) and syringic acid (27.3) in
. Our results suggest that
is the most allelopathic CCs and that the fruits of
are the plant organs richest in allelochemicals.
Background and Purpose: Velvetleaf seed longevity and prolonged emergence complicateassessing appropriate time for its control. Estimating biological parameters (base temperature and base water ...potential) is a first step towards development of emergence predictive model for this weed species in summer crops. Since, development of new model is time consuming, the aim of the research was to provide the data set of biological thresholds for Croatian ecotype and then to compare it with Italian velvetleaf thresholds to assess the implementation of AlertInf predictive weed emergence model from Italy to Croatia.
Materials and methods: Laboratory experiments were conducted with 100 seeds per three replicates at seven constant temperatures (4, 8, 12, 16, 20, 24, 28°C) to estimate base temperature (T b ) and at seven water stress levels (0.00, -0.05, -0.10, -0.25, -0.38, -0.50, -0.80, -1.00 MPa) to estimate base water potential (Ψ b ).
Results: The highest germination occurred at temperature > 20°C with 3.6 days and at water stress level >- 0.25 MPa with 4.9 days to complete 50% of germination (t 50 ). The slowest t 50 occurred at 4°C (41.9 days) and < -0.38 MPa (10.1 days). Estimated Croatian velvetleaf biological parameters are: 4.5°C (T b ) and – 0.67 MPa (Ψ b ) with no significant difference compared to Italian ecotype, according to 95% confidence intervals overlapping.
Conclusion: The results indicate that it could be possible to implement AlertInf model from Italy to Croatia for this weed species without additional adjustment. Nevertheless, next step of this implementation should include validation of estimated results in the field conditions.
Key words: invasive weed species, velvetleaf, germination modelling, integrated weed management, base temperature, base water potential
To better manage invasive populations, it is vital to understand the environmental drivers underlying spatial variation in demographic performance of invasive individuals and populations. The ...invasive common ragweed,
Ambrosia artemisiifolia
, has severe adverse effects on agriculture and human health, due to its vast production of seeds and allergenic pollen. Here, we identify the scale and nature of environmental factors driving individual performance of
A. artemisiifolia
, and assess their relative importance. We studied 39 populations across the European continent, covering different climatic and habitat conditions. We found that plant size is the most important determinant in variation of per-capita seed and pollen production. Using plant volume as a measure of individual performance, we found that the local environment (i.e. the site) is far more influential for plant volume (explaining 25% of all spatial variation) than geographic position (regional level; 8%) or the neighbouring vegetation (at the plot level; 4%). An overall model including environmental factors at all scales performed better (27%), including the weather (bigger plants in warm and wet conditions), soil type (smaller plants on soils with more sand), and highlighting the negative effects of altitude, neighbouring vegetation and bare soil. Pollen and seed densities varied more than 200-fold between sites, with highest estimates in Croatia, Romania and Hungary. Pollen densities were highest on arable fields, while highest seed densities were found along infrastructure, both significantly higher than on ruderal sites. We discuss implications of these findings for the spatial scale of management interventions against
A. artemisiifolia
.
A size–strain line‐broadening analysis of the XRPD patterns and Raman spectra for two anatase/brookite (TiO2)‐based nanocomposites with carbon (C) was carried out and the results compared with those ...of a similar sample free of carbon. The crystal structures and microstructures of anatase and brookite, as well as their relative abundance ratio, have been refined from XRPD data by the Rietveld method (the low amount of carbon is neglected). The XRPD size–strain analysis resulted in reliable structure and microstructure results for both anatase and brookite. The experimental Raman spectra of all the samples in the region 100–200 cm−1 are dominated by a strong feature primarily composed of the most intense modes of anatase (Eg) and brookite (A1g). The anatase crystallite sizes of 14–17 nm, estimated by XRPD, suggest the application of the phonon confinement model (PCM) for the analysis of the anatase Eg mode, whereas the relatively large brookite crystallite size (27–29 nm) does not imply the use of the PCM for the brookite A1g mode. Superposition of the anatase Eg mode profile, calculated by the PCM, and the Lorentzian shape of the brookite A1g mode provide an appropriate simulation of the change in the dominant Raman feature in the spectra of TiO2‐based nanocomposites with carbon. Raman spectra measured in the high‐frequency range (1000–2000 cm−1) provide information on carbon in the investigated nanocomposite materials. The results from field‐emission scanning electron microscope (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and nitrogen physisorption measurements support the XRPD and Raman results.
To examine the structure and microstructure of anatase/brookite (TiO2)‐based nanocomposites with carbon (C), two laboratory techniques, X‐ray powder diffraction (XRPD) and Raman scattering, have been applied and reliable results were obtained. For the investigation of carbon, especially when present in small amounts, Raman scattering has an advantage over XRPD.
In this work, Zn(CH3COO)2 ? 2H2O with AgNO3 content from 0 to 6mol% was
solvothermally treated at 120?C for 18 h in the presence of poly(vinyl
pyrrolidone), ethylene glycol and sodium hydroxide. The ...structural,
microstructural and photocatalytic properties of the unmodified and Ag
modified ZnO powders have been investigated by the XRPD, FESEM, TEM, UV-vis,
Raman and BET techniques. The Ag modified samples consist of ZnO nanocrystals
and metallic Ag on the surface. The average crystallite size of all samples
was about 20 nm. The FESEM revealed the uniformity in size and approximately
spherical shape of ZnO nanoparticles. The BET data suggest that all prepared
samples are mesoporous. All prepared samples showed higher photocatalytic
efficiency in the degradation of the Reactive Orange 16 (RO16) azo dye than
the commercial ZnO. In addition, Ag modified ZnO powders, especially those
with 1.5 and 0.75mol%of Ag, were more efficient than the unmodified one.
Nanocrystalline titanium dioxide (TiO
2
) powders have been synthesized by sol–gel method using titanium tetrachloride (TiCl
4
) or tetrabutyl titanate (Ti(OC
4
H
9
)
4
as precursors, different ...alcohols and calcination temperatures in the range from 400 to 650 °C. The photocatalytic activity of as-prepared powders has been tested for the degradation of metoprolol tartrate salt, a selective β-blocker used to treat a variety of cardiovascular diseases, and compared to photocatalytic activity obtained from Degussa P25. Nanosized TiO
2
powders prepared from TiCl
4
and amyl-alcohol, calcined at 550 °C, displayed an activity comparable to Degussa P25, whereas the sample from the same series, calcined at 650 °C, showed higher photocatalytic activity in the whole range of the catalyst loading. Structural, morphological and surface properties of synthesized TiO
2
nanopowders have been investigated by XRD, SEM, EDS and BET measurements, as well as FTIR and Raman spectroscopy, in order to find out the material properties which enable rapid an efficient decomposition of metoprolol under UV radiation.
Previous research indicated that airborne ragweed pollen concentrations may be influenced by weather-related factors. Therefore, the object of this work was to examine the variation in daily pollen ...concentrations during four ragweed pollen seasons (2006–2009) in the highly urban area of Zagreb. Ragweed pollen grains were collected using a Burkard volumetric sampler (N45°49′55″, E15°58′54″). Meteorological data (maximum, minimum and mean temperatures, relative humidity, wind speed, precipitation, atmospheric pressure and irradiance) were related to daily pollen counts during the ragweed pollen season. The ragweed pollen season started around late July in 2007 and 2009, while it started on 15 August in 2006, the year characterized by a cold spring. However, the start dates of the pollen seasons were not related to the accumulation of thermal units. Maximum daily concentration of 363 grains m
−3
was detected on 27 August 2008. Total airborne pollen concentrations ranged from 1188 grains m
−3
in 2007 to 4384 grains m
−3
in the following year, whereas the duration of ragweed pollen season varied from 50 days in 2008 to 72 days in 2007. The peak of the ragweed pollen season varied from 21 days in 2007 to 36 days in 2009 for airborne pollen concentrations ≥20 grains m
−3
and from 1 day in 2007 to 20 days in 2008 for airborne pollen concentrations >80 grains m
−3
. Airborne pollen levels were affected by weather parameters such as temperature, sunshine, relative humidity, precipitation and wind speed in some ragweed pollen seasons in Zagreb, but these responses were inconsistent over the entire investigated period. Our study showed that large year-to-year variations in atmospheric pollen concentrations in Zagreb could not be consistently related to any of the analysed weather parameters.
Mesoporous anatase nanopowders were doped with 0.05−0.5 mol% of W
6+
, in order to obtain more efficient photocatalyst than TiO
2
Degussa P25 in the degradation of amitriptyline (AMI) under simulated ...solar irradiation (SSI). Dominant XRPD peaks were ascribed to anatase phase, with additional peaks which could correspond to brookite, TiO
2
bronze and sodium titanate, Na
2
Ti
9
O
19
. The Raman scattering measurements have confirmed anatase as dominant phase, with broad Raman feature at ~270 cm
−1
possibly related to Ti–O–Na stretching vibration. All W-doped nanopowders have shown enhanced adsorption and higher efficiency in photodegradation of AMI in comparison to TiO
2
Degussa P25 under the same conditions. The catalyst doped with 0.4 mol% of W
6+
, which has shown the highest efficiency in degradation of AMI under SSI, has also been tested in degradation of alprazolam (ALP). The effect of substrate type (AMI and ALP), catalyst loading, and initial substrate concentration on photocatalytic degradation using SSI was examined. The identification of the species responsible for the photocatalytic degradation of AMI and ALP by the catalyst doped with 0.4 mol% of W
6+
was performed in the presence of various scavengers under SSI. The major role in degradation of AMI may be attributed to hydroxyl radicals, whereas superoxide anion radicals, singlet molecular oxygen and hydroxyl radicals contribute to degradation of ALP.
Highlights
Influence of W and Na content on the properties of TiO
2
catalysts synthesized by sol-gel method.
Powders characterized by XRPD, SEM, EDS, BET, Raman, and UV-vis spectroscopy.
Adsorption and photodegradation of amitriptyline and alprazolam under simulated solar irradiation.
Optimal synthesis and W-doping conditions for photocatalytic degradation of amitriptyline found.
Various scavengers used to identify mechanisms of photodegradation of amitriptyline and alprazolam.
The titanium dioxide (TiO2) nanopowders were produced by sol-gel technique
from tetrabutyl titanate as a precursor by varying some parameters of the
sol-gel synthesis like the temperature (500 and ...550 ?C) and the duration of
the calcination (1.5, 2, and 2.5 h). X-ray powder diffraction (XRPD) results
have shown that all synthesized nanopowders are dominantly in anatase phase,
with the presence of a small amount of rutile in samples calcined at 550 ?C.
According to the results obtained by Williamson-Hall method, the anatase
crystallite size was increased with the duration of the calcination (from 24
to 29 nm in samples calcined at lower, and from 30 to 35 nm in samples
calcined at higher temperature). The analysis of the shift and linewidth of
the most intensive anatase Eg Raman mode confirmed the XRPD results. The
analysis of pore structure from nitrogen sorption experimental data described
all samples as mesoporous, with mean pore diameters in the range of 5-8 nm.
Nanopowder properties have been related to the photocatalytic activity,
tested in degradation of the textile dye (C.I. Reactive Orange 16),
carbofuran and phenol.
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