Assessment of the levels of DDT and DDE in soil and blood samples from Tabasco, Mexico

In Mexico, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) was used until the year 2000, principally in agriculture and anti-paludal program health campaigns. The southeastern region of Mexico was an important area of malaria, and from 1957 DDT was applied indoors every 6?months, with a coverage of 2?g/m². The current study was performed in Tabasco, a Mexican state located in the southeastern region of Mexico. DDT and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (DDE) were analyzed by gas chromatography/mass spectrometry. In general, low levels were found in household outdoor samples; the levels of DDT ranged from not detectable to 0.048?mg/kg, and of DDE from 0.001 to 0.068?mg/kg. An important finding was that, in all communities where DDT in blood was analyzed, exposure to DDT was found, indicating both past and present exposure. Although the levels found in this study were lower than other studies in Mexico, there is a need to evaluate whether the people living in the study area are at risk.     

Disruption of thyroid hormone binding to sea bream recombinant transthyretin by ioxinyl and polybrominated diphenyl ethers

A number of chemicals released into the environment share structural similarity to the thyroid hormones (THs), thyroxine (T(4)) and triiodothyronine (T(3)) and it is thought that they may interfere with the thyroid axis and behave as endocrine disruptors (EDs). One of the ways by which such environmental contaminants may disrupt the TH axis is by binding to TH transporter proteins. Transthyretin (TTR) is one of the thyroid hormone binding proteins responsible for TH transport in the blood. TTR forms a stable tetramer that binds both T(4) and T(3) and in fish it is principally synthesized in the liver but is also produced by the brain and intestine. In the present study, we investigate the ability of some chemicals arising from pharmaceutical, industrial or agricultural production and classified as EDs, to compete with [I(125)]-T(3) for sea bream recombinant TTR (sbrTTR). Ioxinyl, a common herbicide and several polybrominated diphenyl ethers were strong inhibitors of [I(125)]-T(3) binding to TTR and some showed even greater affinity than the natural ligand T(3). The TTR competitive binding assay developed offers a quick and effective tool for preliminary risk assessment of chemicals which may disrupt the thyroid axis in teleost fish inhabiting vulnerable aquatic environments.     

Halophyte vegetation influences in salt marsh retention capacity for heavy metals

We analysed concentrations of Cu, Cd and Pb in above and belowground tissues of the halophyte species Halimione portulacoides and Spartina maritima, as well as in sediments and pore water between the roots in a Tagus estuary salt marsh (Portugal). From these results we calculated the pools of metals in the compartments mentioned above. Relative percentages of accumulation in each pool were also determined. Our aim was to determine how the type of vegetation in the salt marsh affects overall metal retention capacity of the system. It was concluded that areas colonised by H. portulacoides are potential sources of Cu, Cd and Pb to the marsh ecosystem, whereas areas colonised by S. maritima are more effective sinks at least for Cu and Cd. Consequently, S. maritima seems to contribute more effectively to the stabilisation of metals in salt marsh sediments, reducing their availability to the estuarine system.     

Effects of different quinoid redox mediators on the removal of sulphide and nitrate via denitrification

The impact of different quinoid redox mediators on the simultaneous conversion of sulphide and nitrate in a denitrifying culture was evaluated. All quinones evaluated, including anthraquinone-2,6-disulphonate (AQDS), 2-hydroxy-1,4-naphthoquinone and 1,2-naphthoquinone-4-sulphonate (NQS) were reduced by sulphide under abiotic conditions. NQS showed the highest reduction rate by sulphide (132 μmol h⁻¹) and promoted the maximum rate of sulphide oxidation (87 μmol h⁻¹) by denitrifying sludge, which represents an increase of 44% compared to the control lacking quinones. The reduced form of AQDS (AH₂QDS) served as an electron donor for the microbial reduction of nitrite and N₂O, which represents the first demonstration of hydroquinones supporting the microbial reduction of denitrifying intermediates. The results taken as a whole suggest that some quinones may significantly increase the rate of removal of S and N under denitrifying conditions.     

Status and trends of terrestrial arthropod abundance and diversity in the North Atlantic region of the Arctic

Ambio - The Circumpolar Biodiversity Monitoring Programme (CBMP) provides an opportunity to improve our knowledge of Arctic arthropod diversity, but initial baseline studies are required to...     

Effects of a soil organic amendment on metal allocation of trees for the phytomanagement of mining-impacted soils

Environmental Geochemistry and Health - The suitable application of phytomanagement by phytostabilisation using plant tree species in metal-polluted soils requires an assessment of the fate of...     

Comparison of modeling with empirical calculation of diffuse and fugitive methane emissions in a Spanish landfill

One of the most significant environmental problems arising from landfills is the emission of methane into the atmosphere. In this study, methane emissions from a currently in-use Spanish landfill were modeled as well as being experimentally measured using a two-step method. The first step involved a qualitative walkover survey to detect where gases were being emitted on the surface of the landfill. The second stage comprised a quantitative analysis of these surface methane emissions at a selected number of points on the landfill surface using a specially designed flux chamber. The statistical analysis of the data obtained was based on the Sichel function and resulted in an average emission rate of 74.9 g·m^?2·day^?1, with 27.8 and 202.1 g·m^?2·day^?1 as the lower and upper limits of the 95% confidence interval, respectively. The total emission for the landfill, with an emitting surface of 335,000 m², is 9.16 × 10³ ton/yr. These values have been compared with those from three different models, with the model results being above the calculated mean emissions measured at the landfill, but below the upper confidence limit at 95%.

Implications: One of the main environmental problems arising from the presence of landfills is the emission of biogas (which mainly contains methane and carbon dioxide) into the atmosphere. Several experimental methods as well as models have been developed to quantify these emissions. In this work, the authors have compared the results obtained using experimental measurements with those provided by some local and international models using the default parameters proposed. The results obtained from the experimental method are in accordance with those provided by the models, although the models could be slightly overestimating these emissions.     

Fate of domoic acid ingested by the copepod <Emphasis Type="Italic">Acartia clausi</Emphasis>

Two important issues in the studies of harmful algae include ecological role of the toxic compounds and their fate through the food web. The aims of this study were to determine whether the production of domoic acid is a strategy evolved to avoid predation and the role of copepods in the fate of this toxic compound through the food web. The copepod Acartia clausi was fed with single and mixed cultures of the toxic diatom Pseudo-nitzschia multiseries and the non-toxic diatom Pseudo-nitzschia delicatissima. Ingestion rate as a function of diatom abundance was the same for the toxic and non-toxic Pseudo-nitzschia species, indicating no selective feeding behaviour against P. multiseries. The toxins ingested by the copepods did not affect mortality, feeding behaviour, egg production and egg hatching of the copepods. Copepods assimilated the 4.8% of the total domoic acid ingested. Although the amount of toxins daily detoxificated by the copepods was 63.6%, the copepods accumulated domoic acid in their tissues. We conclude that domoic acid is not toxic for copepods and, probably for this reason, this toxin does not act as feeding deterrent for copepods. However, even though the production of domoic acid has apparently not evolved to deter predation, copepods may play an important role on the fate of this toxic compound through the marine food web.