Phototransformation of oxamyl in aqueous solution

The photolysis of the N methyl carbamate pesticide oxamyl (Z isomer) has been studied in aqueous solution. Continuous irradiation at mainly λ = 254 and λ > 290 nm has been performed to characterise the pesticide photochemical behaviour in water at pH = 6.0. Upon monochromatic irradiation, the phototransformation quantum yield was evaluated to be roughly constant, with a value of 0.54 ± 0.08. Upon polychromatic irradiation, a photochemical efficiency has been estimated to be 0.5 ± 0.1 by using phenol as a reference compound. Two main degradation products were identified: the isomer (E) of oxamyl and the nitrile derivative (N,N-dimethyl-2-nitrilo-acetamide). The photolysis of the oximino derivative, an hydrolysis product of oxamyl, was also studied. Upon irradiation at 254 nm, the quantum yield of phototransformation was found to be 0.28. A unique photoproduct was detected: it corresponds to the (E) isomer of the oximino derivative. For prolonged irradiations, a photostationary state was reached between the oximino and its (E) isomer. From kinetics data, the removal of oxamyl and of the oximino derivative during a UV disinfection step used in drinking water production was calculated to be 45 and 13%, respectively.     

Modelling habitat overlap among sympatric mesocarnivores in southern Illinois,USA

Few researchers have developed large-scale habitat models for sympatric carnivore species. We created habitat models for red foxes (Vulpes vulpes), coyotes (Canis latrans) and bobcats (Lynx rufus) in southern Illinois, USA, using the Penrose distance statistic, remotely sensed landscape data, and sighting location data within a GIS. Our objectives were to quantify and spatially model potential habitat differences among species. Habitat variables were quantified for 1-km² buffered areas around mesocarnivore sighting locations. Following variable reduction procedures, five habitat variables (percentage of grassland patches, interspersion–juxtaposition of forest patches, mean fractal dimension of wetland patches and the landscape, and road density) were used for analysis. Only one variable differed (P < 0.05) between red fox and coyote sighting areas (road density) and bobcat and coyote sighting areas (mean fractal dimension of the landscape). However, all five variables differed between red fox and bobcat sighting areas, indicating considerable differences in habitat affiliation between this pair-group. Compared to bobcats, red fox sightings were affiliated with more grassland cover and larger grassland patches, higher road densities, lower interspersion and juxtaposition of forest patches, and lower mean fractal dimension of wetland patches. These differences can be explained by different life history requirements relative to specific cover types. We then used the Penrose distance statistic to create habitat models for red foxes and bobcats, respectively, based on the five-variable dataset. An independent set of sighting locations were used to validate these models; model fit was good with 65% of mesocarnivore locations within the top 50% of Penrose distance values. In general, red foxes were affiliated with mixtures of agricultural and grassland cover, whereas bobcats were associated with a combination of grassland, wetland, and forest cover. The greatest habitat overlap between red foxes and bobcats was found at the interface between forested areas and more open cover types. Our study provides insight into habitat overlap among sympatric mesocarnivores, and the distance-based modelling approach we used has numerous applications for modelling wildlife–habitat relationships over large scales.     

Photocatalytic degradation of the diuron pesticide

The occurrence of chlorinated pesticides in wellwaters is a major problem of public health in Ivory Coast and other African countries. Here, we studied the photocatalytic degradation of the pesticide diuron in aqueous solution in presence of two commercial TiO₂ catalysts, P25 and PC500. The capacity of diuron adsorption at the TiO₂ surface is lower for both photocatalysts. The efficiency of photocatalytic degradation of diuron, it is higher using P25 Degussa than PC500 Millenium TiO₂ catalyst.     

Regeneration status of mangrove forests in Mida Creek,Kenya: a compromised or secured future?

The structure and regeneration patterns of Mida Creek mangrove vegetation were studied along belt transects at 2 forest sites of Mida Creek (3 degrees 20'S, 40 degrees 00'E): Uyombo and Kirepwe. Based on the species importance values, the dominant mangrove tree species in Mida were Ceriops tagal (Perr.) C. B. Robinson and Rhizophora mucronata Lamk. Tree density varied from 1197 trees ha(-1) at Kirepwe to 1585 trees ha(-1) at Uyombo and mean tree height was higher at the former site compared to the latter. The size-class structure at both localities of Mida showed the presence of more small trees than large ones. Spatial distribution pattern of adults and juveniles varied greatly between sites and they showed a close to uniform pattern (Morisita's Index I0 < 1) for trees, but a tendency to random distribution (I0 = 1) for juveniles. The present paper shows that unmanaged but exploited mangroves do not necessarily disappear, but change qualitatively from locally preferred R. mucronata to the less preferred C. tagal. Whereas the effects of this change on the ecological function of the mangrove cannot be estimated yet, the economical function of the mangrove has evidently weakened.     

Prioritizing Pacific Salmon Stocks for Conservation

Over 300 native stocks of Pacific salmon, steelhead, and coastal cutthroat trout (Oncorhynchus spp.) are at risk of extinction in the Pacific Northwest. With only limited resources available for conservation and recovery, prioritization of these stocks may become necessary if meaningful measures are to be implemented. We propose criteria by which prioritization may be guided. First, we rank stocks for risk of extinction, either by population viability analysis or by a set of surrogate measures. Then we rank stocks for biological consequences of extinction, using sets of questions designed to establish the genetic and evolutionary consequences and the ecological consequences if a stock were to become extinct. Together, these rankings allow stocks to be prioritized for a range of possible actions, with those stocks at highest risk and bearing the greatest biological consequences of extinction receiving attention first. Application of the prioritization process to 20 Pacific anadromous salmonid stocks worked as intended, although data limitations are considerable. The process is most likely to work successfully when applied to many stocks on which data exist, when several experts carry out the prioritization, and when the results are peer reviewed.     

Impact of Lime and Ash Applications on Soil Solution Chemistry of an Acidified Podzolic Soil

Soil solution samples were taken from two sites (Horröd and Hasslöv) in the south part of Sweden to evaluate how soil solution chemistry responded to different treatmentswith dolomite and wood ash. At Horröd, samples were taken four years after application of wood ash, 4.28 ton ha^-1 and dolomite, 3.25 ton ha^-1. At Hasslöv dolomite, 3.45 ton ha^-1 and 8.75 ton ha^-1 was applied and samples were taken 15 yr later. It was found that treatment with dolomite at one site (Hasslöv) resulted in higher pH values (<2 pH units) and higher nitrification. It was also found at this site that the total Al and the inorganic Al concentrations decreased with dolomite treatment. The Ca, Mg, DOC, Fe, SO₄ ^2- and Cl^- concentrations, mainly in the topsoil, were found to be higher at both sites, following dolomite treatment; Ca and Mg concentrations were 2–8 times higher (<820 M) than in controls (<70 M). Wood ash was found to have less impact. The PO₄ concentration in the O2 horizon at Hasslöv decreased due to dolomite-treatment. ANOVA (Analyse of Variance) and PLS (Partial Least Square) were used to evaluate the data from the two sites.     

Phenanthrene sorption to structurally modified humic acids

Several studies emphasize the importance of soil organic matter characteristics in hydrophobic contaminant sorption and outline the strong dependence of sorption on organic matter aromaticity. In this study, the role of organic matter aromaticity in phenanthrene sorption was investigated using humic acids (HAs) from compost, peat, and soil that were structurally modified by bleaching, hydrolysis, oximation, and subcritical water extraction. The HAs were characterized with cross polarization magic angle spinning carbon-13 nuclear magnetic resonance (CPMAS 13C NMR) spectroscopy and used in batch equilibrations with phenanthrene. Bleaching substantially reduced the aromaticity of the samples whereas the other treatments increased the relative aromaticity. Phenanthrene sorption increased, even though there was a substantial reduction in sorbent aromaticity with some samples. The HAs that exhibited comparable CPMAS 13C NMR spectra and aromaticity did not behave similarly with respect to phenanthrene sorption. When the sorption data (K(oc) values) were correlated to sample aromaticity, the correlation coefficients (r2) did not exceed 0.39. Comparisons with the atomic H to C ratio provided slightly better r2 values (up to 0.54). This study demonstrates that macroscopic sorbent characteristics could not explain the observed phenanthrene sorption coefficients, aliphatic structural components of HAs can contribute appreciably to phenanthrene sorption, and organic matter physical conformation may regulate access to organic matter structures. Therefore, the use of only macroscopic sorbent properties, such as aromaticity, to predict and rationalize sorption values cannot solely be used to explain the behavior of organic contaminants in soil environments.     

Effects of oxide coating and selected cations on nitrate reduction by iron metal

Under anoxic conditions, zerovalent iron (Fe(0)) reduces nitrate to ammonium and magnetite (Fe3O4) is produced at near-neutral pH. Nitrate removal was most rapid at low pH (2-4); however, the formation of a black oxide film at pH 5 to 8 temporarily halted or slowed the reaction unless the system was augmented with Fe(2+), Cu(2+), or Al(3+). Bathing the corroding Fe(0) in a Fe(2+) solution greatly enhanced nitrate reduction at near-neutral pH and coincided with the formation of a black precipitate. X-ray diffractometry and scanning electron microscopy confirmed that both the black precipitate and black oxide coating on the iron surface were magnetite. In this system, ferrous iron was determined to be a partial contributor to nitrate removal, but nitrate reduction was not observed in the absence of Fe(0). Nitrate removal was also enhanced by augmenting the Fe(0)-H2O system with Fe(3+), Cu(2+), or Al(3+) but not Ca(2+), Mg(2+), or Zn(2+). Our research indicates that a magnetite coating is not a hindrance to nitrate reduction by Fe(0), provided sufficient aqueous Fe(2+) is present in the system.     

Pools and Fluxes of Cations,Anions and Doc in Two Forest Soils Treated With Lime and Ash

The effect of liming and ash treatment on pools, fluxes and concentrations of major solutes was investigated at two forestedsites (Norway spruce) in S. Sweden. One site was treated 15 yrprior to sampling (Hasslöv-Hs; dolomite: 3.45 and 8.75 t ha^-1) and the other 4 yr before (Horröd-Hd; dolomite: 3.25 t ha^-1; wood ash: 4.28 t ha^-1). Effects of limingwere most pronounced in the O horizon solutions where higher pH,elevated Ca (120–700 M) and Mg (50–600 M) were observed as compared to control plots. The impact on the mineralsoil was more moderate. Soil solution concentrations were combined with modelled hydrological flow to calculate mass flows,which largely followed the trends of the solution composition. Liming also resulted in large increases of both exchangeable Caand Mg as well as effective cation exchange capacity (CEC_E;2–5 times the controls). The base saturation (BS%) was raised to 60–100% in the O horizon while in the mineral soil elevated values were only seen at the Hs site (20–60%; down to 10–15 cm depth for 8.75 t ha^-1). Ash treatment did notaffect either the soil solution nor the exchangeable pool to thesame extent as lime. In general, the impact at the Hd site was less pronounced especially in the mineral soil, which might be due to shorter treatment time (4 vs. 15 yr) and also differentthickness of the O horizon. Budget calculations for Ca and Mg originating from the lime showed that a major part of the Ca (40–100%) was retained in the top 30 cm of the soil, of which30–95% was present in the O horizon. The mobility of Mg wasgreater and it was estimated that a significant part had been leached from the profile (30 and 50 cm depth) after 15 yr. Increased mass flows of NO₃ ^- due to nitrification resulting from liming at the Hs site were calculated in the range120–350 mmol m^-2 yr^-1 (or 1.2–3.5 kmol ha^-1 yr^-1). There was significant leaching of Al (25–60 mmol m^-2 yr^-1), of which about 70% was inorganic, in thelower B horizon at both sites with no influence of liming.     

Mercury and organochlorine content of Dipper Cinclus cinclus eggs in south-west Ireland: trends during 1990-1999

A sample of 124 deserted/infertile dipper (Cinclus cinclus) eggs was collected in south-west Ireland during six seasons (1990-1994 and 1999) and analysed for mercury and organochlorines. Mercury was detected in three of the 6 years but no trend was observed. DDT occurred above the limit of detection in only two eggs, one each in 1993 and 1994. In contrast, two derivatives of DDT (DDE and TDE) were found much more commonly. DDE occurred in over 87% of eggs, while TDE contamination was less widespread and reached a maximum of 60% in 1993, with none detected in 1991 or 1999. There was no trend in occurrence of DDE or TDE across years. PCB contamination was present consistently over the 10-year period, with little change in the proportion of contaminated eggs collected over time. In all years, the lowest recorded occurrence of total PCBs was 69% expressed on a formulation basis as Arochlor 1254. PCB congeners 138, 153 and 180 dominated. The congener pattern was similar across years with the exception of 1990 when congener 118 dominated. A distinct trend of high values of contaminants was observed in 1990 and 1993. In 1990, PCB 118 was the dominant contaminant, while in 1993, HEOD, DDE, PCB 138 and PCB 153 were primary contributors to the observed result. Other contaminants (HCB, PCB 101, gamma-HCH, PCB 170 and PCB 180) showed little obvious patterns between years and occurred at relatively low levels. No pattern was observed in contaminants when eggs were grouped according to river or altitude. These data provide a baseline for organochlorine contamination levels in Irish freshwater ecosystems against which future trends can be assessed.