Importance of competition mechanisms in successive invasions by polyphagous tephritids in La Reunion

Understanding the strength and modes of interspecific interactions between introduced and resident species (native or previously introduced) is necessary to predict invasion success. We evaluated different mechanisms of interspecific competition among four species of polyphagous fruit flies (Diptera: Tephritidae) from the island of La Reunion: one endemic species, Ceratitis catoirii, and three exotic species, C. capitata, C. rosa, and Bactrocera zonata, that have successively invaded the island. Larval competition experiments, i.e., co-infestations of the same fruit, and behavioral interference experiments measuring the ability of one female to displace another from a fruit, were performed among all pairs of the four species. We observed asymmetric and hierarchical interactions among species in both larval and adult interference competition. In agreement with the hypothesis that invasion is competition-limited, the competitive hierarchy coincided with the temporal sequence of establishment on the island, i.e., each newly established species tended to be competitively dominant over previously established ones.     

The fitting of general force-of-infection models to wildlife disease prevalence data

Researchers and wildlife managers increasingly find themselves in situations where they must deal with infectious wildlife diseases such as chronic wasting disease, brucellosis, tuberculosis, and West Nile virus. Managers are often charged with designing and implementing control strategies, and researchers often seek to determine factors that influence and control the disease process. All of these activities require the ability to measure some indication of a disease's foothold in a population and evaluate factors affecting that foothold. The most common type of data available to managers and researchers is apparent prevalence data. Apparent disease prevalence, the proportion of animals in a sample that are positive for the disease, might seem like a natural measure of disease's foothold, but several properties, in particular, its dependency on age structure and the biasing effects of disease-associated mortality, make it less than ideal. In quantitative epidemiology, the "force of infection," or infection hazard, is generally the preferred parameter for measuring a disease's foothold, and it can be viewed as the most appropriate way to "adjust" apparent prevalence for age structure. The typical ecology curriculum includes little exposure to quantitative epidemiological concepts such as cumulative incidence, apparent prevalence, and the force of infection. The goal of this paper is to present these basic epidemiological concepts and resulting models in an ecological context and to illustrate how they can be applied to understand and address basic epidemiological questions. We demonstrate a practical approach to solving the heretofore intractable problem of fitting general force-of-infection models to wildlife prevalence data using a generalized regression approach. We apply the procedures to Mycobacterium bovis (bovine tuberculosis) prevalence in bison (Bison bison) in Wood Buffalo National Park, Canada, and demonstrate strong age dependency in the force of infection as well as an increased mortality hazard in positive animals.     

Mercury accumulation in soils and plants in the Almadén mining district, Spain: one of the most contaminated sites on Earth

Although mercury (Hg) mining in the Almadén district ceased in May 2002, the consequences of 2000 years of mining in the district has resulted in the dissemination of Hg into the surrounding environment where it poses an evident risk to biota and human health. This risk needs to be properly evaluated. The uptake of Hg has been found to be plant-specific. To establish the different manners in which plants absorb Hg, we carried out a survey of Hg levels in the soils and plants in the most representative habitats of this Mediterranean area and found that the Hg concentrations varied greatly and were dependent on the sample being tested (0.13–2,695 μg g⁻¹ Hg). For example, the root samples had concentrations ranging from 0.06 (Oenanthe crocata, Rumex induratus) to 1095 (Polypogon monspeliensis) μg g⁻¹ Hg, while in the leaf samples, the range was from 0.16 (Cyperus longus) to 1278 (Polypogon monspeliensis) μg g⁻¹ Hg. There are four well-differentiated patterns of Hg uptake: (1) the rate of uptake is constant, independent of Hg concentration in the soil (e.g., Pistacia lentiscus, Quercus rotundifolia); (2) after an initial linear relationship between uptake and soil concentration, no further increase in Hg_plant is observed (e.g., Asparagus acutifolius, Cistus ladanifer); (3) no increase in uptake is recorded until a threshold is surpassed, and thereafter a linear relationship between Hg_plant and Hg_soil is established (e.g., Rumex bucephalophorus, Cistus crispus); (4) there is no relationship between Hg_plant and Hg_soil (e.g., Oenanthe crocata and Cistus monspeliensis). Overall, the Hg concentrations found in plants from the Almadén district clearly reflect the importance of contamination processes throughout the study region.     

Simulation of germination of pioneer species along an experimental drought gradient

The germination of ten plant species from the Iberian Peninsula was assessed along a water deficit gradient between -0. 1652 (moist) and -0.4988 MPa (dry) of osmotic potential, created by addition of increasing concentrations of polyethylene glycol (PEG 6000) to distilled water in which plants were grown hydroponically. The level and rate of germination of Daucus carota and Thapsia villosa significantly decreased with decreasing psi. Seeds of Dactylis glomerata and Dittrichia viscosa had positive germination responses to low osmotic potentials; germination of Epilobium hirsutum was not affected by osmotic potential. Germination of Medicago arabica, Cynosurus cristatus, Cistus ladanifer and Cistus albidus, was no favored by the addition of polyethylene glycol (PEG). Germination of Foeniculum vulgare and Thapsia villosa was inhibited by PEG.     

水质对UV/H2O2降解17α-乙炔基雌二醇（EE2）的影响

采用UV/H₂O₂间歇式光氧化反应器,研究了溶液pH值、腐殖酸及水中常见阴离子HCO₃^-、NO₃^-、CO₃^2-、Cl^-和SO₄^2-对UV/H₂O₂工艺降解17α-乙炔基雌二醇(EE2)的影响.结果表明,UV/H₂O₂工艺可以有效地去除水中的EE2,光降解过程符合一级反应动力学模型.双氧水投加量为5 mg/L时,在14W低压汞灯照射下,EE2在自来水和蒸馏水中的光降解一级反应速率常数为0.063 0min^-1和0.132 4min^-1.溶液中的腐殖酸和阴离子HCO₃^-、NO₃^-、Cl^-、SO₄^2-对EE2的光降解反应有抑制作用,4种阴离子浓度为5 mmol/L时,抑制作用依次为HCO₃^->SO₄^2->Cl^->NO₃^-,HCO₃^-可使光降解速率常数降低到50%.自来水中的光降解速率常数低于蒸馏水中的光降解速率常数是水中多种离子影响的结果.     

Binding of Pb(II) in the system humic acid/goethite at acidic pH

The study of Pb(II) binding to the system humic acid/goethite in acidic medium is reported in the present paper. From a macroscopic point of view, we have constructed the experimental sorption isotherms (using atomic absorption spectroscopy) and compared them with the prediction of the additivity rule. It is found that this system presents positive deviations, that is, the amount sorbed is about an order of magnitude higher than predicted. Apart from this, microscopic and structural aspects have also been studied using in situ and ex situ infrared spectroscopy. These results suggest that the presence of Pb(II) increases the amount of humic acid bound to the oxide. It is proposed that proton displacement due to the interaction between humic substances and the oxide, along with the formation of ternary complexes with the Pb(II) cation bridging the oxide and the humic substances (Type A complexes), cause the deviation from additivity.     

Degradation of the pharmaceutical metronidazole via UV, Fenton and photo-Fenton processes

Degradation rates and removal efficiencies of Metronidazole using UV, UV/H2O2, H2O2/Fe2+, and UV/H2O2/Fe2+ were studied in de-ionized water. The four different oxidation processes were compared for the removal kinetics of the antimicrobial pharmaceutical Metronidazole. It was found that the degradation of Metronidazole by UV and UV/H2O2 exhibited pseudo-first order reaction kinetics. By applying H2O2/Fe2+, and UV/H2O2/Fe2+ the degradation kinetics followed a second order behavior. The quantum yields for direct photolysis, measured at 254 nm and 200-400 nm, were 0.0033 and 0.0080 mol E(-1), respectively. Increasing the concentrations of hydrogen peroxide promoted the oxidation rate by UV/ H2O2. Adding more ferrous ions enhanced the oxidation rate for the H2O2/Fe2+ and UV/H2O2/Fe2+ processes. The major advantages and disadvantages of each process and the complexity of comparing the various advanced oxidation processes on an equal basis are discussed.     

Effects of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool

The aim of our study was to determine the impact of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool. An indoor swimming pool was equipped with two medium-pressure UV lamps. We collected eight samples of water daily over a four-weeks period and measured total and free chlorine, pH, water temperature, bacteriological parameters, total organic carbon and trihalomethanes. During the first week, which served as control, medium-pressure UV lamps were turned off. During the next three weeks, medium-pressure UV lamps were kept on 24 h per day. The third week, we reduced the level of the injected chlorine into water, and the last week we also reduced the water renewal volume by 27%. Our results showed that bacteriological parameters remained within allowable french limits. When medium-pressure UV lamps were kept on, total, free and active chlorine levels were significantly increased (P<0.001), whereas combined chlorine level were significantly decreased (P<0.001 and P<0.05, respectively). The levels of chloroform and bromodichloromethane were significantly increased when medium-pressure UV lamps were kept on (P<0.001), whereas chlorodibromomethane and bromoform levels significantly decreased (P<0.05 and P<0.001, respectively). The additional formation of chloroform and bromodichloromethane may be explained by the increase in active chlorine and by radicalizing mechanisms initiated by UV radiation.     

Enantiomeric fractions and congener specific determination of polychlorinated biphenyls in eggs of predatory birds from Doñana National Park (Spain)

The content of 30 polychlorinated biphenyls (PCBs) and the enantiomeric fractions of 10 chiral PCBs were determined in 17 infertile eggs from three different predatory bird species collected in Do?ana National Park (DNP, Spain) in the period 1999-2000. The highest PCB concentration was found in eggs from red kites (0.52-110 microg/g on a fresh weight basis, f.w.) followed by buzzard (0.08-13 microg/g f.w.) and booted eagle (0.10-1.5 microg/g f.w.). Seventy-five percent of the red kite eggs had PCB levels above 4.7 microg/g f.w., which is associated in the literature with reproductive failure. This could be related to the fact that red kite populations have decreased by more than 50% in the last five years in DNP. PCBs # 138, 153, and 180 were the most abundant in all cases. This is the first time that atropisomers of 10 chiral PCBs (PCBs # 45, 84, 91, 95, 132, 135, 136, 149, 174, and 176) in predatory bird eggs have been performed. The enantiomeric fractions (EFs) for most PCBs investigated were non-racemic (EF not = 0.5), ranging from 0.05 to 0.95. The results suggested that predatory birds, mainly red kite species, are highly polluted by PCBs, and PCBs # 95, 132, 135, 136, and 174 strongly deviate from the racemic-mixture values.