Influence of humic acid on adsorption and desorption of atrazine, hydroxyatrazine, deethylatrazine, and deisopropylatrazine onto a clay-rich soil sample

Adsorption and desorption properties of atrazine and some of its metabolites, hydroxyatrazine (AT-OH), deethylatrazine (DEA), and deisopropylatrazine (DIA), were studied with a clay-rich soil sample (clay content of 53%). A part of this soil was treated with humic acid (Soil-HA) to assess the influence of this important component of natural organic matter on adsorption and desorption processes. This study was performed using the batch approach with 1.0 g of soil, or Soil-HA, in 5.0 mL of 0.010 mol L(-)(1) CaCl(2) solution containing the herbicide and the metabolites in a concentration range between 0.010 and 5.0 mg L(-)(1). After 24 h of contact time, the suspensions were centrifuged and the four compounds were quantified in the supernatant phases by high-performance liquid chromatography. The adsorption and desorption data of both Soil and Soil-HA were properly fitted by the linearized Freundlich equation. For the untreated soil, the adsorption affinity order evaluated as a function of the K(f) values was AT-OH > AT > DIA > DEA, while desorption followed the order DEA > DIA approximately AT > AT-OH. The presence of humic acid increased significantly the adsorption of all compounds, following the same affinity order observed for the untreated soil. Increase in adsorption was especially high for AT-OH and AT. On the other hand, the dealkylated metabolites, DEA and DIA, were more easily desorbed from the Soil-HA sample, suggesting that natural organic matter facilitates the leaching of these compounds. Desorption order in the presence of humic acid was DEA > DIA > AT > AT-OH.     

Adsorption of atrazine, hydroxyatrazine, deethylatrazine, and deisopropylatrazine onto Fe(III) polyhydroxy cations intercalated vermiculite and montmorillonite

This paper describes the modification of the clay minerals vermiculite (VT) and montmorillonite (MT) by intercalating Fe(III) polymers of different [OH(-)]:[Fe(III)] ratios with the aim of removing atrazine (AT) and its metabolites deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (ATOH) from aqueous solution. An enhancement of adsorption capacity was observed for both intercalated clay minerals in comparison to the potassium-saturated materials (KVT or KMT). The results showed that different [OH(-)]:[Fe(III)] molar ratios had a small influence on the adsorption capacity, as well as in the basal spacing, BET surface area, and porosity. For the lowest initial concentrations of AT, DIA, and ATOH (0.050 mg L(-)(1)) studied, the modified VT adsorbed almost 80% of AT and DIA, while ATOH was removed at concentration levels below the detection limit of the technique, implying in at least 99.5% of sorption. Weak interaction between intercalated VT and DEA was observed, although a significant adsorption enhancement occurred in comparison to KVT. Within a 24 h interval, desorption of AT and DIA in aqueous medium reached levels close to 20% of the amount initially adsorbed, while for ATOH only 3% of the adsorbed compound was desorbed. The adsorption capacity of the Fe(III)-intercalated VT decreased after the first adsorption/desorption cycle, implying that the material is not suitable for reutilization. The intercalated MT was a powerful sorbent for AT, DEA, DIA, and ATOH, removing all of these chemicals from solution almost quantitatively (sorption greater than 99.5%), even at initial concentrations as high as 1.0 mg L(-)(1). Additionally, desorption of AT, ATOH, and DIA in water was not measurable up to the tube corresponding to the initial concentration of 1.0 mg L(-)(1), suggesting strong irreversible binding of these compounds to the intercalated MT materials. Desorption of DEA from the intercalated MT was between 5 and 30%. Unlike what was observed for VT, the intercalated MT materials were recyclable, keeping an excellent performance when reutilized.     

Human impact and slope dynamics evolutionary trends in the monoclinal relief of Adriatic area of central Italy

The present work deals with a large area of the Marche–Abruzzi monoclinal relief which is made up of a clayey sediment succession with sandy–conglomeratic levels alternating at varying stratigraphic heights. The east-verging monocline was generated by an intense Quaternary tectonic uplifting. It differs approximately in the west-east and in the southern directions forming three wide morphostructures. The deep fluvial down-cutting disjointed the monoclinal relief into a succession of high hills which give the area a typical cuesta morphology, with fronts facing the western quadrants.     

Nine months postpartum weight retention predictors for Brazilian women

OBJECTIVE: To identify factors potentially associated with weight retention measured 9 months after childbirth. DESIGN: Prospective study with four follow-up waves in time (0.5, 2, 6 and 9 months postpartum). SETTING: Rio de Janeiro, Brazil. SUBJECTS AND METHODS: Two hundred and sixty-six Brazilian women of childbearing age. Analysis was based on hierarchical logistic regression. The dependent variable was weight retention and was defined as the difference between weight at 9 months postpartum and pre-pregnancy weight, with a dichotomised cut-off at 7.5 kg. Covariates included demographic and socio-economic data, obstetric history, anthropometric data, and data on the infant. These data were grouped in blocks and ordered according to their influence on the dependent variable. RESULTS: Of the women studied, 19.2% presented weight retention values > or =7.5 kg. According to the logistic regression analysis, the following variables remained associated with weight retention > or =7.5 kg: total family income, difficulty or inability to read a letter, age category > or =30 years, age at first childbirth <23 years, gestational weight gain > or =12 kg, body fat at baseline > or =30% and infant birth weight <3500 g. Infant hospitalisation was only marginally significant. CONCLUSIONS: Determinant factors identified by the analysis highlight the need for nutritional intervention policies during pregnancy and in the first months postpartum as a way of minimising obesity and the diseases resulting from it.     

Relative condition factor and parasitism in anostomid fishes from the floodplain of the Upper Paraná River, Brazil

Individuals of four species of Leporinus were captured in the floodplain of the Upper Paraná River and their metazoan parasites were collected. Fifty-eight taxa of ectoparasites and endoparasites were recorded: 31 in Leporinus lacustris, 32 in Leporinus friderici, 28 in Leporinus obtusidens and 25 in Leporinus elongatus. The aim of this paper was to study the relationship between the host's condition and the parameters of infrapopulations and infracommunities. The health of the host was represented by the relative condition factor (Kn). Richness and number of individuals in the infracommunities of ectoparasites covariated with the Kn of the hosts in one species of fish. Some infrapopulations of ectoparasites covariated negatively and/or the mean Kn of parasitized individuals was lower than those without parasites. The abundance in some infrapopulations of endoparasites covariated positively with the Kn and/or the mean Kn of parasitized fish was better. These results may be related to different transmission strategies used by ecto and endoparasites.     

Urban sustainable agriculture: The paradox of the chinampa system in Mexico City

Agriculture and Human Values - Although the chinampa agriculture in Mexico City is considered an historical sustainable farming system,there have been few studies on its current status. This paper...     

Planting time as a tactic to manage the small rice stink bug, Oebalus poecilus (Hemiptera, Pentatomidae), in Rio Grande do Sul, Brazil

Field studies throughout the year focused on the life history of the small rice stink bug, Oebalus poecilus, in southern Brazil. In addition, laboratory experiments examined the bug's life cycle and photoperiodic responses. Adults remain dormant during most of the year. Although activity is restricted to the period between November and March, four generations can develop in each rice-growing season, and populations can reach economically harmful levels. Late-planted rice, however, escapes attack because diapause is induced during early March. The results indicate that delaying and restricting the time of rice planting can be an effective pest management tactic in Rio Grande do Sul, because it results in asynchrony between the pest and the crop.     

Neoliberal restructuring, neoregulation, and the Mexican poultry industry

The US poultry industry based on flexible accumulation has been advanced as the model of agro-industrial development for agrifood globalization. Similarly, Mexico has been presented as a noteworthy example of the negative effects of neoliberal restructuring associated with the globalization project. In this paper we use both of these assertions as points of departure to guide an investigation of the case of the restructuring of the Mexican poultry industry. Informed by a commodity systems analysis, archival data and key informant interviews are used to generate an overview of the history of the poultry industry in Mexico. A sociology of agrifood theoretical framework informed by regimes theory is employed to analyze the events of the case. We conclude that neoregulation related to the IMF and NAFTA restructuring in Mexico facilitated the diffusion of the US model of poultry production.     

How learning to read changes the cortical networks for vision and language

Does literacy improve brain function? Does it also entail losses? Using functional magnetic resonance imaging, we measured brain responses to spoken and written language, visual faces, houses, tools, and checkers in adults of variable literacy (10 were illiterate, 22 became literate as adults, and 31 were literate in childhood). As literacy enhanced the left fusiform activation evoked by writing, it induced a small competition with faces at this location, but also broadly enhanced visual responses in fusiform and occipital cortex, extending to area V1. Literacy also enhanced phonological activation to speech in the planum temporale and afforded a top-down activation of orthography from spoken inputs. Most changes occurred even when literacy was acquired in adulthood, emphasizing that both childhood and adult education can profoundly refine cortical organization.