Dry deposition velocity estimates of SO2 from models and measurements over a deciduous forest in winter

Measurements were made of concentrations and vertical flux densities (using the eddy correlation technique) for SO₂ over a deciduous forest during March and April 1990. These were compared with estimates of dry deposition velocities, obtained from resistance analogue models that employ measured meteorological data as input. The models include: (1) the dry deposition module that forms part of a larger Eulerian air quality model, known as ADOM (Acid Deposition and Oxidant Model), (2) a modified version of ADOM and (3) a new parameterization for R _c . The observations yielded V _d values of about 0.5 cm s^?1 for the daytime and 0.1 cm s^?1 at night. ADOM's estimates were much larger, averaging about 3.0 cm s^?1 during the daytime and about 2.0 cm s^?1 at night. When the ADOM canopy resistance was increased by modifying its formulation, the modified dry deposition estimates were slightly larger during the day than at night, averaging about 0.5 cm s^?1. The new parameterization for R _c yielded smaller V _d estimates with no diurnal variation. An attempt is made to relate the observed diurnal cycle of the dry deposition velocity to meteorological parameters.     

Olive oil mill wastewater treatment using a chemical and biological approach

Olive oil mill wastewaters (OMW) are recalcitrant to biodegradation for their toxicity due to high values of chemical oxygen demand (COD), biological oxygen demand (BOD), and phenolic compounds. In the present study OMW, collected in southern Italy, were subjected first to a chemical oxidative procedure with FeCl3 and then to a biological treatment. The latter was performed in a pilot plant where mixed commercial selected bacteria, suitable for polyphenols and lipid degradation, were inoculated. The effect of treatments was assessed through COD removal, reduction of total phenols, and decrease of toxicity using primary consumers of the aquatic food chain (the rotifer Brachionus calyciflorus and the crustacean Daphnia magna). The results showed that the chemical oxidation was efficacious in reducing all parameters analyzed. A further decrease was found by combining chemical and biological treatments.     

Acid deposition and forest nutrient imbalances: A modeling approach

Leaching of nutrients in areas with high acid deposition could be one of the causes to the nutritional imbalance observed in the tree leaf biomass in these areas. A simulation model is developed in order to study the interaction between soil and vegetation in acidified forests. A tree growth model, based on the nutrient productivity concept, is supplemented with soil processes to form an integrated plant-soil model containing the most important soil processes for acidification. The model is able to link decreased Mg availability in the soil and reduced growth caused by Mg deficiency. Simulation results show that the time and pH at which the stand will start to experience Mg deficiency is dependent on quantity and type of acid deposition, growth rate of the stand, initial base saturation and initial fraction of Mg on the cation exchange complex. The total amount of Mg initially present is not decisive for the time at which Mg deficiency will appear. The conceptual idea of nutrient imbalances in forest stands caused by acid deposition induced leaching is supported by this model.     

Eddy correlation measurements of dry deposition fluxes using a tunable diode laser absorption spectrometer gas monitor

An instrument package, based on a tunable diode laser absorption spectrometer and comprehensive micrometeorological instrumentation, has been successfully developed for making dry deposition flux measurements, using eddy correlation techniques. Preliminary results from the field testing and evaluation of the instrument package at a rural location are presented. Low deposition velocities were measured for NO₂ and SO₂ to snow.     

Dry deposition velocity of O3 over a vineyard obtained from models and observations: The 1991 California ozone deposition experiment

Measurements were made of concentrations and flux densities (using the eddy correlation technique) for O₃ over a vineyard for 20 days during July and August 1991. These were compared with modelled dry deposition velocities (V _d), using (a) a module in the air quality model known as ADOM (Acid Deposition and Oxidant Model), which was modified to apply over a specific site, (b) a version of the ADOM module that employs a modified canopy resistance and (c) versions of ADOM which use two new canopy resistance formulations that are referred to as Wesely and Massman, respectively. The Massman parameterization is valid only locally since it was tuned to the site's ozone data. Here it is used as a benchmark for model comparisons. The observed V _dhad an average value of about 0.5 cm s^?1 during the day and about 0.2 cm s^?1 at night. Compared to the modified ADOM, the new parameterizations yielded results that were in better agreement with the observations at night. During the daytime, the original ADOM and the Wesely estimates were much larger than the observations, the Massman values were slightly smaller, and the modified ADOM showed a better agreement. We speculate that the underestimation of the Massman V _dvalues during the day may have been caused by the ADOM aerodynamic resistance rather than the Massman canopy resistance. It is hypothesized that the original ADOM module and its modified version may need a revised aerodynamic or an additional canopy resistance at night in order to bring the estimates closer to the observations.     

A canopy budget model to assess atmospheric deposition from throughfall measurements

A canopy exchange model is presented which allows atmospheric deposition to be estimated from longterm throughfall and precipitation measurements. For a forest in the Netherlands, the combination of throughfall measurements and this model resulted in deposition estimates which were similar to deposition estimates derived from micrometeorological measurements and inferential modeling, deposition of NOy being the only exception. Unfortunately, several basic assumptions in the canopy exchange model are not properly evaluated, which up to now limits its application. Suggestions are made on how the model can be improved.     

Field determination of sorptivity as a function of water content using a tension infiltrometer

Sorptivity for tension wetting in the field was determined and weighted-mean diffusivity calculated. Both tension sorptivity and weighted-mean diffusivity could be described by an exponential function of the form aexp(bθ) where θ is either mean water content or dimensionless water content and a and b are parameters. This relation was valid for an initial water content between 0.016 and 0.047 m³ m^?3 and a final water content between 0.154 and 0.316 m³ m^?3. Tension sorptivity was more strongly correlated with average water content than dimensionless water content. However, in the case of weighted-mean diffusivity, the correlations with both dimensionless water content and average water content were almost the same.     

Compatible measurements of volumetric soil water content using a neutron probe and Diviner 2000 after field calibration

Field calibrations for a neutron probe and a capacitance sensor (Diviner 2000) for measuring the soil water content of a shrinking–swelling clay soil were substantially different from commonly used default values. Using our field calibrations, the two instruments estimated similar changes in the cumulative water content of a soil profile (0–1 m depth) over one growing season.     

Urban wet deposition nitrate: A comparison to non-urban deposition

The concentration of nitrate in both wet and dry deposition has both increased historically and currently, and recently parallels emissions in NO_x. Since NO_x is produced in amounts comparable to SO₂, it is an important contributor to acid deposition, and is produced in higher amounts in urban areas due to concentrated sources. Prior to this study, national acid deposition monitoring networks in the United States have been and remain established in non-urban areas. This research study consisted of a comparison of precipitation sampling and analysis of wet deposition nitrate and pH for each deposition event in each of two urban sites over a 15 mo period. Also, a comparison of urban data and data generated at a nearby non-urban NADP site was made by examination of both monthly and seasonal data. This research suggests that national monitoring programs should consider inclusion of urban and non-urban monitoring sites in order to achieve a more representative regional assessment.     

Systemic acquired resistance in crop protection: from nature to a chemical approach

Plant natural resistance to potential parasites is regulated by two fundamental mechanisms: the "nonhost" and the "gene-for-gene" resistance, respectively. The latter is relevant when a cultivar resistant (R) gene product recognizes an avirulence gene product in the attacking pathogen and triggers an array of biochemical reactions that halt the pathogen around the site of attempted invasion. To cope with virulent pathogens, plants may benefit by some temporary immunity after a challenge triggering such an array of defense reactions, following a localized necrotizing infection as a possible consequence of a hypersensitive response (HR). This process, mediated by accumulation of endogenous salicylic acid (SA), is called systemic acquired resistance (SAR) and provides resistance, to a certain extent even against unrelated pathogens, such as viruses, bacteria, and fungi, for a relatively long-lasting period. SAR may be more potently activated in plants pretreated with chemical inducers, most of which appear to act as functional analogues of SA. This review summarizes the complex aspects of SAR as a way to prevent crop diseases by activating the plants' own natural defenses. The following outline is taken: (1) introduction through the historical insight of the phenomenon; (2) oxidative burst, which produces high levels of oxygen reactive species in a way similar to the inflammation state in animals and precedes the HR to the pathogen attack; (3) SAR as a coordinate action of several gene products leading to the expression of defenses well beyond the time and space limits of the HR; (4) jasmonic acid (JA) and ethylene as other endogenous factors mediating a different pathway of induced resistance; (5) pathogenesis related proteins (PR proteins) de novo synthesized as specific markers of SAR; (6) exogenous inducers of SAR, which include both synthetic chemicals and natural products; (7) the pathway of signal transduction between sensitization by inducers and PR expression, as inferred by mutageneses, a process that is still, to a large extent, not completely elucidated; (8) prospects and costs; (9) final remarks on the state-of-the-art of the topic reflecting the chemical view of the author, based on the more authoritative ones expressed by the authors of the reviewed papers.     

A new approach to determining water stable aggregation

Abstract

A new method is introduced to measure water stability of soil aggregates. The wrist‐action shaker is a simple, inexpensive tool that provides highly accurate data for the assessment of soil erodibility. Three soils from Hawaii (two Oxisols and one Vertisol) with different mineralogies, management histories, and potassium (K)‐factors were examined in this study. Six indices of water stable aggregation were determined after rapid immersion of air‐dry aggregates, followed by gentle wet‐sieving. Single‐sieve indices of percent water stable aggregates (WSA) < 0.063 mm, > 0.25 mm, and > 1.00 mm, were highly correlated. Additionally, these indices were highly correlated with three multiple sieve indices, namely geometric mean aggregate diameter (GMAD), arithmetic mean aggregate mass diameter (MAMD), and the coarse‐to‐fine index (CFI = % WSA > 1.00 mm / % WSA < 0.063 mm). Analysis of WSA data indicated that the relative soil erodibility ranking, from high to low, would be: Lualualei Vertisol > Molokai Oxisol > Kaneloa Oxisol. Discriminant analysis using GMAD and % WSA > 1.00 mm correctly classified 55 of 56 soil samples into their respective soil series.     

Investigation of thermal decomposition as the kinetic process that causes the loss of crystalline structure in sucrose using a chemical analysis approach (part II)

High performance liquid chromatography (HPLC) on a calcium form cation exchange column with refractive index and photodiode array detection was used to investigate thermal decomposition as the cause of the loss of crystalline structure in sucrose. Crystalline sucrose structure was removed using a standard differential scanning calorimetry (SDSC) method (fast heating method) and a quasi-isothermal modulated differential scanning calorimetry (MDSC) method (slow heating method). In the fast heating method, initial decomposition components, glucose (0.365%) and 5-HMF (0.003%), were found in the sucrose sample coincident with the onset temperature of the first endothermic peak. In the slow heating method, glucose (0.411%) and 5-HMF (0.003%) were found in the sucrose sample coincident with the holding time (50 min) at which the reversing heat capacity began to increase. In both methods, even before the crystalline structure in sucrose was completely removed, unidentified thermal decomposition components were formed. These results prove not only that the loss of crystalline structure in sucrose is caused by thermal decomposition, but also that it is achieved via a time-temperature combination process. This knowledge is important for quality assurance purposes and for developing new sugar based food and pharmaceutical products. In addition, this research provides new insights into the caramelization process, showing that caramelization can occur under low temperature (significantly below the literature reported melting temperature), albeit longer time, conditions.     

The conservation value of farmland ponds: Predicting water beetle assemblages using vascular plants as a surrogate group

Ponds are among the most diverse and yet threatened components of freshwater biodiversity. The conservation of ponds would greatly benefit from the identification of surrogate taxa in preliminary assessments aimed at detecting ponds of potentially high biodiversity value. Here, we used predictive co-correspondence analysis (Co-CA) to quantify the strength of plant species composition and plant community types in predicting multivariate patterns in water beetle assemblages, based on data from 54 farmland ponds in Ireland. The predictive accuracy of a number of environmental variables as well as that of plant diversity (species richness and evenness) was calculated using predictive canonical correspondence analysis (CCA-PLS). The study ponds supported over 30% of the Irish water beetle fauna (76 species), with five species having some form of IUCN Red List Status in Ireland, as well as 67 wetland plant species, including a nationally rare one. Co-CA showed that plant species composition had a positive predictive accuracy, which was significantly higher compared to that of data at the plant community type level. Although environmental variables showed a higher predictive capacity compared to that of plant species composition, the difference was not significant. Explanatory CCA analyses showed that plants and beetles both responded to the same subset of environmental conditions, which explained approximately 18% of the variation in both plant and beetle species composition. Regional differences as well as permanency, substratum, and grazing intensity affected the composition of both plant and beetle assemblages. These findings have important implications in conservation planning. First, wetland plants can be effectively used as a surrogate taxon in the identification of conservation-priority ponds. Second, conservation strategies aimed at maintaining and enhancing pond biodiversity should be based on considerations on plant species composition.     

The role of silvicultural systems and forest types in preventing soil erosion processes in mountain forests: a methodological approach using cesium-137 measurements

Purpose

Forests play a key role in providing protection against soil erosion. Particularly, the role of vertical forest structure in increasing rainfall interception capacity is crucial for mitigating raindrop impact and reducing splash and rill erosion. For this reason, studies on the relationships between forest structures, the past management, and the observed rates of soil loss are needed. In the last few decades, importance was given to the use of cesium-137 (¹³⁷Cs) as radioactive tracer to estimate soil erosion rates. The ¹³⁷Cs technique is linked to the global fallout of bomb-derived radiocesium which occurred during a period extending from the mid 1950s to the late 1970s.

Materials and methods

The ¹³⁷Cs technique, providing long-term retrospective estimates, could be related to forest treatments applied during the last decades in different sites, also considering the tree species composition. This approach could be useful to compare the effect of different canopy cover and biomass on soil erosion rates related to different tree species. In the work proposed here, a study area dominated by pine and beech high forests located in the Aspromonte Mountains (Calabria, Italy) was selected. The measurements, related to forest structural traits, focusing on canopy cover and biomass, and also on management approaches and forest types, are compared with rates of soil erosion provided by ¹³⁷Cs.

Results and discussion

The overall results suggest that the minimum values of soil loss are documented in areas with higher canopy cover and biomass evidencing the protective effect provided by forests against soil erosion. Also, techniques based on the use of tracers like ¹³⁷Cs proved to be helpful to select the best forest management options useful to optimize the protective role of forests, with the aim to reduce erosion processes in a long-term perspective.

Conclusions

The experiment indicates that care must be taken when new silviculture treatments are planned. These findings are in agreement with what documented by other authors in similar environments but need further studies to confirm the effectiveness of using ¹³⁷Cs in different forest ecosystems.

     

The development of a new approach for establishing a core collection using multivariate analyses with tulip as case

A methodology is developed for the establishment of a core collection based on phenotypic data. A case is worked out for the tulip cultivar collection of the Hortus Bulborum, consisting of approximately 1000 cultivars. The methodology is based on cluster analysis of phenetic characters, selection of cultivars from the resulting clusters according to a combination of the proportional and genetic diversity dependent strategies, optimisation of the selection, and validation by means of principal component analysis and by the diversity indices of Nei and Shannon & Weaver. A core collection with 104 cultivars (approx. 10%: CORE-1) did not give a sufficient representation of the existing diversity. A set of 152 cultivars (approx. 15%: CORE-2) showed a far better representation. The variation in resistance levels for Fusarium is almost completely represented in CORE-2. Although a set of 200 cultivars (approx. 20%: CORE-3) reached a nearly complete representation of the total diversity, a better representation of the resistance levels was not achieved. The newly presented methodology for defining a core collection appears to be a useful approach. The included steps for optimising and validating the choice of accessions makes it a reliable and broadly applicable method.     

Interspecies calibration of heavy-metal concentrations in nine mosses and lichens:-Applicability to deposition measurements

The study describes a method for including nine alternative moss and lichen species in heavy-metal air-pollution surveys based on concentrations in one of the species. Iron, Cu, Zn, Pb, Ni and Cd concentrations have been measured in Dicranum polysetum, Hylocomium splendens, Hypnum cupressiforme, Pleurozium schreberi, Pohlia nutans, Cladonia rangiferina, Hypogymnia physodes, Pseudevernia furfuracea and Usnea filipendula from 57 sites in coniferous woodland surrounding a brass foundry in Sweden. Concentrations vary decidedly between species. The mosses frequently show higher concentrations than the lichens. The use of different monitor species in a deposition survey without interspecies calibration is not advised. Calibration factors for concentrations in different species can be calculated from the mean concentrations in each species. With the help of the factors, concentrations in a species not found in a certain site can be estimated from concentrations measured in any of the other species sampled. The applicability of the reported calibration factors to surveys in other regions is discussed. Where these factors are not applicable, local calibration factors for indicator species of interest can be set up using the method presented.     

A guidance for the assessment and evaluation of sediment quality a German Approach based on ecotoxicological and chemical measurements

The recommendations presented in this paper use an integrated hierarchical approach combining toxicological, chemical and ecological information to assess and evaluate the quality of sediments. For this reason, biological methods, in combination with the tools of chemical analysis, are given priority when examining the quality of the sediment to establish adverse effects. The trigger is the biotest, instead of chemical methods commonly used. The individual methods are presented for a German approach and can be adopted to other countries by applying ISO, OECD methods. Support is provided on how to best integrate data generated using different assessment tools. Keywords: Bioassays; biological and chemical analysis; ecotoxicology; integrated assessment; sediment assessment; sediment quality; stepwise strategy     

Evaluation of the spatial pattern of surface soil water content of a karst hillslope in Southwest China using a state-space approach

This study aims to evaluate the effects of soil physicochemical properties and environmental factors on the spatial patterns of surface soil water content (SWC) based on the state-space approach and linear regression analysis. For this purpose, based on a grid sampling scheme (10 m × 10 m) applied to a 90 m × 120 m plot located on a karst hillslope of Southwest China, the SWC at 0–16 cm depth was measured 3 times across 130 sampling points, and soil texture, bulk density (BD), saturated hydraulic conductivity (K_s), organic carbon (SOC), and rock fragment content as well as site elevation (SE) were also measured at these locations. Results showed that the distribution pattern of SWC could be more successfully predicted by the first-order state-space models (R² = 67.5–99.9% and RMSE = 0.01–0.14) than the classic linear regression models (R² = 10.8–79.3% and RMSE = 0.11–0.24). The input combination containing silt content (Silt), K_s, and SOC produced the best state-space model, explaining 99.9% of the variation in SWC. And Silt was identified as the first-order controlling factor that explained 98.7% of the variation. In contrast, the best linear regression model using all of the variables only explained 79.3% of variation.