Total mercury content found in edible tissues of top predator fish from the Gulf of California,Mexico

Fish at the top of the food chain bioaccumulate and biomagnify toxic metals including mercury (Hg), at a higher rate than nonpredatory fish. However, although some top predator fish species are important in the human diet, the risks for consumers in Mexico are difficult to evaluate due to the scarce baseline information available. In the present article, data on the total mercury (THg) concentrations found in edible tissues of different species of sharks, rays, large pelagic fishes and groupers from the Gulf of California are presented and compared with national and international health guidelines. During 2003 and 2004, 73 shark dorsal tissue samples, 52 ray samples, 66 large pelagic fish samples and 16 grouper samples were collected at different sites along the Gulf of California. Samples were digested in a microwave system and analyzed by cold vapor atomic absorption spectrophotometry. Thirty samples (14%) showed concentrations of Hg above the national statutory limit of 1?mg?kg^?1, from which 25 samples were sharks and 3 were large pelagic fishes. A positive correlation was found between the natural log of THg [ln(THg)] and total length (TL cm) in species of sharks, rays and groupers. The Teacapán estuary in Sinaloa was detected as a possible source of Hg into the Gulf of California due to historic mining in the watershed. Mean Hg concentrations exceeded the regulatory limit of 1?mg?kg^?1 in the following highly commercial shark species: smooth hammerhead, pelagic thrasher, pacific sharpnose shark, dusky shark, scalloped hammerhead, and whitenose shark, in that order. It is recommended that preventive food advisories be issued with respect to these species until further investigations are conducted.     

Preparation of CuO/SiO<Subscript>2</Subscript> and photocatalytic activity by degradation of methylene blue

A photocatalyst based on CuO/SiO₂ was prepared, and evaluated for the degradation of methylene blue in aqueous medium. The photocatalyst was obtained by calcination method of copper salt, in the presence of silica. The characterization by XRD, FTIR, and TPR techniques confirmed the formation of CuO as active phase. SEM studies showed CuO deposited on the surface of SiO₂. By ESI-MS, it was demonstrated that the degradation of methylene blue occurs through successive hydroxylations. Photodegradation assays showed that CuO/SiO₂ was efficient for degradation, and that the material worked better in the presence of UV light.     

Relation between pesticide exposure and intrauterine growth retardation

The increased use of organophosphorus insecticides in agriculture and their widespread existence in the environment poses a potential health hazard. To determine the relationship between exposure to pesticides and intrauterine growth retardation (IUGR), live newborns from singleton pregnancies, with (n = 79) and without (n = 292) IUGR were studied. During the gestational period the mothers were living in agricultural communities in the state of Chihuahua, Mexico. Exposure to agrochemical products was evaluated. A significant association between the history of positive exposure to pesticides (i.e. the women themselves or their newborns who showed acetylcholinesterase activity levels lower than 20%) and the presence of IUGR was found. The proportions of exposure in the cases were 18% and 8% in the control group; the adjusted OR (fat free mass, anti-cytomegalovirus antibodies and placental weight) was 2.33 (p = 0.04).     

RNAi-mediated silencing of vitellogenin gene function turns honeybee (Apis mellifera) workers into extremely precocious foragers

The switch from within-hive activities to foraging behavior is a major transition in the life cycle of a honeybee (Apis mellifera) worker. A prominent regulatory role in this switch has long been attributed to juvenile hormone (JH), but recent evidence also points to the yolk precursor protein vitellogenin as a major player in behavioral development. In the present study, we injected vitellogenin double-stranded RNA (dsVg) into newly emerged worker bees of Africanized genetic origin and introduced them together with controls into observation hives to record flight behavior. RNA interference-mediated silencing of vitellogenin gene function shifted the onset of long-duration flights (>10 min) to earlier in life (by 3–4 days) when compared with sham and untreated control bees. In fact, dsVg bees were observed conducting such flights extremely precociously, when only 3 days old. Short-duration flights (<10 min), which bees usually perform for orientation and cleaning, were not affected. Additionally, we found that the JH titer in dsVg bees collected after 7 days was not significantly different from the controls. The finding that depletion of the vitellogenin titer can drive young bees to become extremely precocious foragers could imply that vitellogenin is the primary switch signal. At this young age, downregulation of vitellogenin gene activity apparently had little effect on the JH titer. As this unexpected finding stands in contrast with previous results on the vitellogenin/JH interaction at a later age, when bees normally become foragers, we propose a three-step sequence in the constellation of physiological parameters underlying behavioral development. David Santos Marco Antonio and Karina Rosa Guidugli-Lazzarini contributed equally to the present study.     

Valorization of EVA waste from footwear industry as natural aggregates substitutes in mortar: the effect of granulometry

Journal of Material Cycles and Waste Management - The increased consumption of polymers and the consequent generation of waste requires the development of efficient recycling strategies. In this...     

Performance of mortars with PET

Journal of Material Cycles and Waste Management - The massive amount of plastic production inevitably leads to huge levels of pollution and, consequently, is threatening the environment and...     

Dynamics of phosphorus and phytate-utilizing bacteria during aerobic degradation of dairy cattle dung

During organic wastes degradation, P is transformed which may affect its availability. In this study, the dynamics of P and the occurrence of phytate-utilizing bacteria (PUB) were evaluated during aerobic degradation of dairy cattle dung in laboratory-scale reactors for 105 d. The results showed an increase of water-soluble inorganic P (Pi) (from 570 to 1890 mg kg(-1)) and biomass P (from 390 to 870 mg kg(-1)) during the initial 40 d. After this period, water-soluble Pi remained constant (around 1500 mg kg(-1)) and biomass P decreased (around 220 mg kg(-1)) probably due to the decrease of easily available C in dung. Under the acidic conditions in the first 20 d there was an increase in concentration of Al (25 mg kg(-1)) and Fe (27 mg kg(-1)) ions. These ions were no longer detectable in the alkaline conditions occurring after 40 d. In the same period, the Ca concentration increased (from 1170 to 2370 mg kg(-1)) and chemical speciation revealed permanent association of Ca ions with Pi. Sequential P fractionation showed a decrease of organic P in NaHCO(3), NaOH and HCl fractions and an increase of residual P (25-52% with respect to total P). Analysis by (31)P NMR also showed a decrease (from 14% to 1.6%) of phytic acid content during final experimental period (60 and 105 d). The bacteriological analysis revealed various PUB involved in degradation of the dung. Two morphotypes, genetically characterized as Enterobacter and Rahnella, which were dominant under higher content of residual P, showed strong utilization of phytate in vitro.     

Relative influence of the dissolved humic material on the solid-phase extraction efficiency of pesticides from environmental water

The effect of organic matter on the solid-phase extraction (SPE) efficiency for pesticides belonging to different chemical groups (urea-derivatives, carbamates and triazines) and having different polarities, was simultaneously studied for the first time in pure and simulated water samples. SPE was carried out in precolumns packed with C18 silica or styrene-divinylbenzene copolymer PLRP-S phases on-line coupled to high performance liquid chromatography (HPLC) analysis. Retention factors in water (k'_W) were estimated for 25 compounds and used for the calculation of the theoretical breakthrough volume (Vb_T) in pure water. Experimental breakthrough volumes (Vb_E) were first determined using purified and deionized water as the matrix for selected compounds having Vb_T < 500 mL; then, the same water with an added humic acid sodium salt (HA) at 0.4–5.6 mg/L of dissolved organic carbon (DOC) content, was used as the matrix for compounds having VbE < 500 mL in pure water. Several polar pesticides showed negative linear or logarithmic Vb_E curves depending on HA content; their recoveries were also determined in environmental samples having low dissolved organic carbon values, between 0.5–6.4 mg/L. A similar behavior was observed for these compounds in simulated and natural water samples, where DOC concentration and the percolated volume (Vp) mainly determine the solute recoveries values. However, the variation of recoveries as a function of DOC content could be negative or null depending on the two examined conditions (Vp lower or larger than Vb_E in pure water). Results demonstrated that breakthrough volume must always be considered to correctly interpret the participation of dissolved humic material on the SPE efficiency of organic micropollutants in water.     

Primary colonization and breakdown of igneous rocks by endemic, succulent elephant trees (Pachycormus discolor) of the deserts in Baja California, Mexico

Trees growing in rocks without soil are uncommon. In two arid regions in Baja California, Mexico, field surveys found large numbers of rock-colonizing elephant trees (Pachycormus discolor (Benth.) Coville ex Standl. (Mexican name: copalquin) growing in igneous rocks (granite and basalt) as primary colonizers without the benefit of soil or with a very small amount of soil generated by their own growth. Many adult trees broke large granite boulders and were capable of wedging, growing in, and colonizing rocks and cliffs made of ancient lava flows. This is the first record of a tree species, apart from the previously recorded cacti, capable of primary colonization of rocks and rock rubble in hot deserts.     

Accumulation fatty acids of in Chlorella vulgaris under heterotrophic conditions in relation to activity of acetyl-CoA carboxylase,temperature, and co-immobilization with Azospirillum brasilense

The relation between fatty acid accumulation, activity of acetyl-CoA carboxylase (ACC), and consequently lipid accumulation was studied in the microalgae Chlorella vulgaris co-immobilized with the plant growth-promoting bacterium Azospirillum brasilense under dark heterotrophic conditions with Na acetate as a carbon source. In C. vulgaris immobilized alone, cultivation experiments for 6 days showed that ACC activity is directly related to fatty acid accumulation, especially in the last 3 days. In co-immobilization experiments, A. brasilense exerted a significant positive effect over ACC activity, increased the quantity in all nine main fatty acids, increased total lipid accumulation in C. vulgaris, and mitigated negative effects of nonoptimal temperature for growth. No correlation between ACC activity and lipid accumulation in the cells was established for three different temperatures. This study demonstrated that the interaction between A. brasilense and C. vulgaris has a significant effect on fatty acid and lipid accumulation in the microalgae.