Analysis of the evolution of gross alpha and gross beta activities in airborne samples in Valencia (Spain).

Gross alpha (Aα) and gross beta activities (Aß) were measured weekly in the airborne of the Universitat Politècnica de Valencia campus (in the east of Spain) during the period 2009-2015 (7 years). The geometric mean values of weekly Aα and Aß were 0.53·10-4 Bq m-3 and 5.77·10-4 Bq m-3, respectively; with an average ratio Aα/Aß of 0.097. This study highlights the heterogeneity of gross alpha and gross beta activities depending on the different periods of the year. Data show seasonal variations with the highest activity in summer months and the lowest one in winter months. Several atmospheric factors were considered in order to explain this intra-annual variation (wind speed, temperature, relative humidity, precipitations, dust content and prevailing wind directions). Multiple Linear Regression Analysis were performed in order to obtain information on significant atmospheric factors that affect gross α and gross ß variability, which could be useful in identifying meteorological or atmospheric changes that could cause deviations in gross α and gross ß activity depending on the seasons considered. Models obtained explain more than 60% of variability for global data, and also for winter and spring-autumn months. However, more research is needed to explain gross α and gross ß variability in summer months, because the atmospheric factors considered in the MLR explain less than 35% of variability.

Effect of Trichoderma-enriched organic charcoal in the integrated wood protection strategy.

The gradual elimination of chromium from wood preservative formulations results in higher Cu leaching and increased susceptibility to wood decay fungi. Finding a sustainable strategy in wood protection has become of great interest among researchers. The objective of these in vitro studies was to demonstrate the effect of T-720-enriched organic charcoal (biochar) against five wood decay basidiomycetes isolated from strongly damaged poles. For this purpose, the antagonistic potential of Trichoderma harzianum (strain T-720) was confirmed among other four Trichoderma spp. against five brown-rot basidiomycetes in dual culture tests. T-720 was genetically transformed and tagged with the green fluorescent protein (GFP) in order to study its antagonistic mechanism against wood decay basidiomycetes. It was also demonstrated that T-720 inhibits the oxalic acid production by basidiomycetes, a well-known mechanism used by brown-rot fungi to detoxify Cu from impregnated wood. Additionally, this study evaluated the effect of biochar, alone or in combination with T-720, on Cu leaching by different preservatives, pH stabilization and prevention of wood decay caused by five basidiomycetes. Addition of biochar resulted in a significant Cu binding released from impregnated wood specimens. T-720-enriched biochar showed a significant reduction of wood decay caused by four basidiomycetes. The addition of T-720-enriched biochar to the soil into which utility poles are placed may improve the efficiency of Cr-free wood preservatives.

Integrated control of wood destroying basidiomycetes combining Cu-based wood preservatives and Trichoderma spp.

The production of new generation of wood preservatives (without addition of a co-biocide) in combination with an exchange of wood poles on identical sites with high fungal inoculum, has resulted in an increase of premature failures of wood utility poles in the last decades. Wood destroying basidiomycetes inhabiting sites where poles have been installed, have developed resistance against wood preservatives. The objective of the in vitro studies was to identify a Trichoderma spp. with a highly antagonistic potential against wood destroying basidiomycetes that is capable of colonizing Cu-rich environments. For this purpose, the activity of five Trichoderma spp. on Cu-rich medium was evaluated according to its growth and sporulation rates. The influence of the selected Trichoderma spp. on wood colonization and degradation by five wood destroying basidiomycetes was quantitatively analyzed by means of dry weight loss of wood specimens. Furthermore, the preventative effect of the selected Trichoderma spp. in combination with four Cu-based preservatives was also examined by mass loss and histological changes in the wood specimens. Trichoderma harzianum (T-720) was considered the biocontrol agent with higher antagonistic potential to colonize Cu-rich environments (up to 0.1% CuSO4 amended medium). T. harzianum demonstrated significant preventative effect on wood specimens against four wood destroying basidiomycetes. The combined effect of T. harzianum and Cu-based wood preservatives demonstrated that after 9 months incubation with two wood destroying basidiomycetes, wood specimens treated with 3.8 kg m-3 copper-chromium had weight losses between 55-65%, whereas containers previously treated with T. harzianum had significantly lower weight losses (0-25%). Histological studies on one of the wood destroying basidiomycetes revealed typical decomposition of wood cells by brown-rot fungi in Cu-impregnated samples, that were notably absent in wood specimens previously exposed to T. harzianum. It is concluded that carefully selected Trichoderma isolates can be used for integrated wood protection against a range of wood destroying basidiomycetes and may have potential for integrated wood protection in the field.