Dioselina Álvarez-Bernal

Accumulation and hazard assessment of mercury to waterbirds at Lake Chapala, Mexico.

Lake Chapala is the largest tropical lake in Mexico. The objectives of this study were to determine bioaccumulation of Hg in fish and to evaluate the potential impacts of Hg in the diet of aquatic birds, particularly the American white pelican (AWPE), in Lake Chapala. Hg concentrations in three fish species ranged from 0.021 to 0.568 μg/g wet weight. Mercury in fish was positively and significantly correlated with total fish length (R2=0.44, P<0.05). The δ15N values in fish were significantly correlated with Hg concentrations in Chapala and the San Antonio Reservoir (R2=0.69, P<0.001 and R2=0.40, P<0.001, respectively). However, Hg concentrations in bird feathers were not significantly different between years, among locations, or among species. Hg concentrations in fish from Lake Chapala were within values reported in many parts of the world. The Hg (mean range of 2.75 to 4.54 μg/g dw) and δD (mean range of -62‰ to -11‰) values in bird feathers suggested a wide pattern of exposure for highly migratory AWPE and egrets, although birds with lower δD values in feathers appeared to have greater concentrations of Hg than those with higher δD values. Contaminant exposure in aquatic birds in Chapala during the breeding season should be monitored next to better determine the potential effects of Hg on resident aquatic birds.

Emission of N2O from polycyclic aromatic hydrocarbons contaminated soil at different water contents added with vermicompost.

Vermicompost is typically applied to improve soil quality, but can be used to remediate hydrocarbon-contaminated soils. Little information is available on how contamination and subsequent bioremediation with vermicompost affects emissions of N2O and CO2, important greenhouse gases. A sandy loam soil with different water contents (40%, 60%, 80% and 100% of water holding capacity (WHC)) was contaminated with phenanthrene, anthracene and benzo(a)pyrene and amended with or without vermicompost to stimulate remediation of soil. Emissions of N2O and CO2, and concentrations of inorganic N (ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−)) were determined in a laboratory incubation experiment after 0h, 5h, 24h, 72h and 168h. The cumulative CO2 production rate was significantly larger in soil incubated at 60%WHC and 80%WHC compared to soil incubated at 40% and 100%WHC. Addition of vermicompost increased production of CO2 and N2O. Addition of PAHs increased production of CO2 when water content of soil was at 60%WHC and production of N2O when water content of soil was at 80% WHC. Addition of PAHs induced immobilization of inorganic N and inhibited nitrification as the concentration of NH4+ and NO2− in soil contaminated with PAHs was larger than in unamended soil while the concentration of NO3− was lower. It was found that contamination of soil with PAHs increased emissions of N2O and CO2 and biostimulation of autochthonous microflora with organic material to remediate those soils further increases production of N2O and CO2. These findings indicate that trace gas emissions should be included in estimations of the environmental impact of contamination of soil and their subsequent bioremediation.

Space-Time Modeling of the Electrical Conductivity of Soil in a Geothermal Zone

ABSTRACT The aim of this study was to generate models to predict the salinity of the soils in the geothermal zone which is located in Michoacán, México, over space and time. Systematic sampling was performed at locations 400 m apart with a sampling period every 48 days. At each site, two soil samples, from depths of 0–30 cm and 30–60 cm, were collected and analysed in laboratory. Regression-Kriging was used to make spatial predictions of the electrical conductivity of soil (ECs). Spherical and Gaussian theoretical models fit the experimental semivariograms. The results showed that the soil samples ranged from slightly saline (2.1–4 dS m−1) to strongly saline (8.1–16 dS m−1). In addition, the ECs was greater at a depth of 30–60 cm than it was at a depth of 0–30 cm. The ECs decreased from more than 8.0 dS m−1 to less than 4.0 dS m−1 after the first sampling period.

Improvement of saline soils with Vicia sativa L. from a semiarid region

Bragantia, Campinas, v. 77, n. 3, p.501-509, 2018 ABSTRACT: In the Cienega de Chapala region of the state of Michoacan, Mexico, forage crops form a major pillar for traditional livestock systems. In this region, high soil salinity due to poor groundwater quality is a common problem. Thus, the objective of this research was to evaluate the potential of the forage species Vicia sativa L. for improved saline soil in a greenhouse and non-leaching conditions over the course of 90 days. In this experiment, three levels of NaCl salinity were tested: 5.3, 7.12 and 10.8 dS·m–1. Samples of soil were analyzed for electrical conductivity of the saturation paste extract (ECe), soluble and interchangeable cations (Na+, K+, Ca2+ and Mg2+) content. Then, the forage species Vicia sativa L were divided into three categories (leaf, stem, and root) and their shoot biomass production and Na+, K+, Ca2+ SOIL AND PLANT NUTRITION Article

Determination of Phenolic Compounds and the Antioxidant Capacity of Ximenia parviflora Benth. var. parviflora (Olacaceae) Fruit by High-Performance Liquid Chromatography with Diode Array Detection

ABSTRACT The total phenolic and flavonoid content, phenolic composition, and in vitro antioxidant capacity of ethanolic extracts of Ximenia parviflora Benth. var. parviflora fruits collected at Zinaparo, Michoacan (in central Mexico) were determined. Fruit extracts present a high scavenging activity of 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis[3-ethylbenzothiazoline-6-sulfonic acid] radicals (71.49 ± 0.11% and 85.00 ± 1.29% inhibition, respectively). The four phenolic compounds identified in fruit extracts by high-performance liquid chromatography with diode array detection were gallic acid, chlorogenic acid, caffeic acid, and quercetin. X. parviflora fruits may be used as a starting material for the extraction of high value antioxidant phenolic compounds with potential applications in the pharmaceutical and dietary supplement industries.

Determination and quantification of phenolic compounds in methanolic extracts of Solanum ferrugineum (Solanaceae) fruits by HPLC-DAD and HPLC/ESI-MS/TOF

ABSTRACT Solanum ferrugineum Jacq. is a wild species that in previous analysis reported a significant antioxidant capacity. The aim of our research was to determine total phenolic content (TPC) and total flavonoid content (TFC), and the phenolic composition by HPLC-DAD and HPLC/ESI-MS/TOF of methanolic extracts of S. ferrugineum fruits, collected from Paredones, Jiquilpan, and Fray Dominguez, Pajuacarán in the Mexican state of Michoacán. TPC and TFC were determined by the spectrophotometric Folin–Ciocalteu reagent and the AlCl3 method, respectively. TPC in S. ferrugineum fruit [31.41 ± 0.91 mg gallic acid equivalent/g dry tissue (DT)] was similar to those reported for Turkey berry (Solanum torvum Sw.) and eggplant (Solanum melongena L.) fruits. The TFC values of S. ferrugineum fruits (29.14 ± 4.99 mg catechin equivalent /g DT) corresponded to 80.24% of the TPC. Eight phenolic compounds (PC) were identified by HPLC analysis. The main PC identified in S. ferrugineum fruits were chlorogenic acid, caffeic acid, p-coumaric acid, gallic acid, quercetin, and kaempferol. S. ferrugineum fruits could be used as a starting material for the extraction of high-value PC with potential applications. GRAPHICAL ABSTRACT