Application of Relaxed Eddy Accumulation Technique to Quantify Hg0 Fluxes Over Modified Soil Surfaces

Fluxes of mercury from a waste repository and from an agricultural field amended with sewage sludge were measured. The measurements were performed by utilising a Relaxed Eddy Accumulation (REA) system synchronously coupled to automated mercury cold vapour atomic fluorescence analysers (CVAFA). The waste repository was severely contaminated and fluxes of between 0.16μg m^?2 h^?1 and 29μg m^?2 h^?1 could be measured. Fluxes at the slightly contaminated agricultural field measured between 8 ng m^?2 h^?1 and 1.9μg m^?2 h^?1. The results showed that the REA-CVAFA system could be used for measurements above both severely-and slightly contaminated soils. The measurements at the chlor-alkali plant showed that temperature was the most important parameter controlling the release of mercury at this site. At the agricultural field, the measurements indicated that both solar radiation and temperature may have influenced the emissions. Most of the mercury added to the field was lost to the atmosphere during the summer season.     

Simultaneous determination of furanocoumarins in infusions and decoctions from "Carapiá" (dorstenia species) by high-performance liquid chromatography

The use of furanocoumarins, which are photosensitizing compounds, combined with exposure to UV-A radiation is a common treatment for vitiligo, psoriasis, and a number of other skin diseases. Although furanocoumarins plus UV-A treatment is highly effective, several studies have shown that exposure to high doses increases the risk to development of cutaneus carcinoma. Several Dorstenia species are used in folk medicine, mainly against skin diseases, because of the presence of biologically active compounds. We present here analysis of the chemical composition of furanocoumarins from infusion and decoction of "Carapiá" (Dorstenia species), which is used in Brazil against several diseases. We have employed high-performance liquid chromatography (HPLC) procedures for the quantitative determination of psoralen, bergapten, and isopimpinellin. The contents of furanocoumarins revealed an insignificant difference between infusion and decoction. Dorstenia tubicina and D. asaroides contained psoralen and bergapten only in the rhizomes, whereas D. vitifolia shows solely isopimpinellin in both rhizomes and aerial parts.     

Mutations associated with pyrethroid resistance in the honey bee parasite Varroa destructor evolved as a series of parallel and sequential events

Journal of Pest Science - Managed honey bees have suffered severe seasonal losses for most of the past 30 years, while at the same time there is a growing need for food crop pollination....     

Two systems for collection of zooplankton for the culture of larval and juvenile fish

Two systems for enrichment and collection of natural Zooplankton in cooling water recipients were developed for rearing fish fry. One system filters-off plankton from the cooling water with rotating dip-nets (diam. 60 cm). The rotation is powered by the kinetic energy of the water and the nets are continuously flushed clean by high-pressure sprays. The water from the nets, being enriched with plankton, is pumped continuously to a grading station where undesirable size fractions are removed, after which the water is distributed to the rearing pens. The system has been tested at a nuclear power station in the south-western part of the Bothnian Sea and found to be promising, with a collection of, on average, 280 g day^–1. The other system is based on attraction using underwater lamps and pumping of organisms into floating rearing pens. The system is automatic and powered by electricity from the grid. The technical performance has been good. The plankton has been size-graded by attaching net baskets around the lamps. At a nuclear power station on the western coast of the central Baltic Sea, the amount collected has, on average, been 45–570 g Zooplankton lamp^–1 night^–1. The collection system is considered to be of use in productive areas with moderate turnover of water. Both systems are in early stages of development and have not reached their full potential. Improvements are proposed and discussed.     

Low pre-death growth rates of oak (<Emphasis Type="Italic">Quercus robur</Emphasis> L.)—Is oak death a long-term process induced by dry years?

• Background and purpose   

A complex interplay between biotic and abiotic factors is believed to be responsible for several oak declines in pedunculate oak (Quercus robur L.). This study aims to clarify the temporal process of oak declines, as well as identifying individual tree and environmental variables that affects growth rate and that may increase the risk of mortality. The study was performed in southern Sweden at three sites.     

Mercury in swedish forest soils and waters — Assessment of critical load

As a result of air pollution, the content of Hg in fish has significantly increased in a large part of Scandinavia and North America. In this paper, the occurence and fluxes of Hg in Swedish forest soils and waters are reviewed and synthesized. The main objective is to describe and evaluate the present transport of anthropogenic Hg from atmospheric deposition, through the terrestrial compartment and running waters to lake basins and also to comprehend the main factors influencing these fluxes. The transportation and distribution. of Hg in forest soils and waters is closely related to the flow of organic matter. The content of Hg in humic matter is higher in southern and central areas compared to the north of the country. Compared to background concentrations, the Hg content has increased in the southern and central part by about a factor of 4–7, while the overall increase in the north is by about a factor of 2 to 3. The increased content of Hg in forest soils may have an effect on organisms and biological processes in the soil. Regarding budget calculations for whole catchment areas and for the mor layer of the soil, a reduction of about 80% from present atmospheric wet deposition must be obtained to reach “critical load” with respect to conditions in Scandinavia.     

The composition of the soil solution as influenced by fertilization and nutrient uptake

The composition of the soil solution in unfertilized and well-fertilized plots of three long-term field experiments has been determined at the beginning and at the end of the growing season. All the plots were manured and the K and P fertilizers given in the autumn before the growth of sugar beet. N was applied in the spring, 3–4 weeks before the first soil sampling.The soil solution was removed at a pressure of 5 atm. The composition and the corresponding osmotic pressure were calculated for the moisture contents at field capacity and wilting point.In spring the salt concentrations, cations + anions, at the field capacity were in the range 91–97 mmoles/l in the fertilized plots. In autumn the concentration had dropped to 13.9–20.3, a decrease of 78–85%. At the wilting point, the concentrations in spring were as high as 211–307 mmoles/l and in autumn 31.5–69 mmoles/l. The corresponding osmotic pressures at field capacity in the spring ranged 2.2–2.3 atm. and at wilting point 5.1–7.4 atm.In spring the unfertilized plots showed concentrations of 16–21 mmoles/l and osmotic pressures of 0.38–0.51 atm., the values decreasing 52–65% during the growing season.It was pointed out that the high soil-solution concentration and osmotic pressure at low moisture contents may lead to an unfavourable effect on root metabolism. Further, the obscuring effect of the varying soil-solution concentration on the relationships between root ion exchange and nutrient uptake by plants has been discussed.     

Links Between Runoff Generation,Climate and Nitrate-N Leaching from Forested Catchments

To assess links between hydroclimatological factors and NO₃ ^- concentrations in streamflow from boreal forests with shallow soils, data from two catchments were analyzed. TOPMODEL was used to calculate the surface runoff fraction, daily dynamics of soil moisture, groundwater levels, and extensions of saturated areas. The stable isotope 18O was used for isotopic hydrograph separation (IHS) during one snowmelt season. Air-temperature and flow increase were the dominating factors explaining annual NO₃ ^-dynamics. Correlation also was found between NO₃ ^- concentrations and the surface runoff fraction. Increased concentrations during times of shallow groundwater were found both during cold and warm periods in one catchment. In the other, shallow groundwater was correlated to decreasing concentrations during cold periods, and increasing concentrations during warm periods. A two component model of event and pre-event water fractions and corresponding NO₃ ^- concentrations was set up for the snowmelt season. Model predictions mirrored NO₃ ^- concentrations during the first five days of the snowmelt. After that, the model overestimated NO₃ ^- concentrations, which indicates retention of NO₃ ^- in the event water fraction, originating from the snowmelt. The highest concentrations occurred during the initiations of flow increase, which indicates flushing of surficial NO₃ ^-.     

Sulfate Adsorption-Desorption in a Swedish Forest Soil

The Forest Roof project at Lake Gårdsjön located on the Swedish Southwest coast near Gothenburg was established to assess the response of the ecosystem following a major reduction in loading of sulfur acidic deposition. The objective of the study was to describe the adsorption-desorption processes of sulfate in Haplorthod soils at the Gårdsjön site. A sequential batch technique was used to sequentially leach the upper three mineral horizons with forest floor leachate containing different concentrations of sulfate. Results showed that adsorption-desorption processes were highly irreversible and hysterestic in nature. Moreover, the soil solution SO₄ ^2-, pH and DOC were interrelated. These findings suggest that improvements in the prediction capability of models for acidified surface waters, lakes and soils are needed. Therefore, existing sulfate models with fully reversible Langmuir or Freundlich approaches need to account for additional irreversible reactions.