Bioaccumulation of lead and the influence of chelating agents in Catla catla fingerlings

Lead is a widespread element and one of the persistent and cumulative pollutants of the environment. The present study deals with the bioaccumulation of lead and the influence of chelating agents, meso 2,3-dimercaptosuccinic acid (DMSA), D-Penicillamine and CaNa₂EDTA in reducing the concentration of lead on the selected organs of Catla catla fingerlings for both acute and chronic exposures by using ICP-AES. It is inferred from the present findings that there was a correlation between environmental conditions and the heavy metal contents of the fish. The highest concentration of lead is found in kidney tissues and the lowest in muscle tissues. The accumulation pattern of lead in the selected organs of Catla catla is: kidney > liver > gill > brain > muscle. Also, it has been found that the treatment of chelating agents, DMSA, D-Penicillamine and CaNa₂EDTA reduces the concentration of lead significantly for both acute and chronic exposures. The results also show that DMSA is the most effective chelator of lead in reducing the body burden of C. catla fingerlings. The observed data further indicate that C. catla could be suitable for monitoring organisms to study the bioavailability of water-bound metals in freshwater habitats.     

Evaluation of boron removal from water by hydrotalcite-like compounds

Layered double hydroxides (LDHs) or hydrotalcite (HT)-like compounds with different kinds of metal ions (Mg-Al and Mg-Fe) in the brucite-like sheets were prepared and their adsorption properties were studied in the boron removal from aqueous solution under laboratory conditions. The hydrotalcites were synthesized by the coprecipitation method and were characterized by chemical analyses, X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and specific surface area measurements (BET). The affinity of these materials with a mixture of B(OH)(3) and B(OH)(4)(-) was studied as a function of contact time, initial pH of the solutions, HT quantity and B concentration (adsorption isotherms). It was found that 120 min is enough time for the equilibrium state to be reached in boron adsorption. Boron removal was independent of the initial pH of the solutions because of the high buffering capacity of the LDHs. On the other hand, the adsorption capacity increases with increasing the adsorbent quantity. The adsorption isotherms, described by the Langmuir model, are of L-type, suggesting that B(OH)(4)(-) is adsorbed preferentially on HT-like materials. Besides, Mg-Al hydrotalcites showed higher adsorption capacity than Mg-Fe. We proposed that in Mg-Al hydrotalcites, the boron removal occurs by both adsorption on external surface and ion exchange, whereas for Mg-Fe it occurs only by surface adsorption. After treatment of a solution containing 5.2 mgBl(-1) with Mg-Al hydrotalcites the final boron concentration reached the recommended limit by WHO for drinking water (0.5 mgl(-1)).     

巴西雨林自然保护区河流中杀虫剂残毒:对水生生物和人类健康的影响评价

1998年11月、1999年3月和2000年元月分别在巴西雨林自然保护区河流的水体、沉积物和鱼体中检测杀虫剂残毒,每种杀虫剂浓度与基于急性毒性测试的生态毒理基准进行了比较,并且还与规定标准进行比较,以确定它们对水生生物和人类潜在影响的程度.在所有的7个调查地点都检测出杀虫剂及其代谢产物,在水体以及沉积物样品中检测出总共27种杀虫剂及其代谢物的残毒,鱼类富集其中某些最持久稳固的残毒.水体和沉积物中检测出的杀虫剂残毒浓度表明水生生物保护的问题需要引起重视,水体中的几种杀虫剂含量超过了巴西以及欧盟当局规定的指标,表明对人类的健康也有影响.     

Hormetic effect of glyphosate on Urochloa decumbens plants

Abstract

Urochloa decumbens plants may be reached by herbicide drift from applications of glyphosate from neighboring areas or by variations during applications. Considering the different phenological stages and size of plants in these areas, the amount of active ingredient that reaches the plants probably varies. The objective of this study was to evaluate the effects of the application of different doses of glyphosate on U. decumbens plants. Two greenhouse experiments were conducted with two replications at different times. The first experiment evaluated the biological response of U. decumbens plants to glyphosate doses (0, 2.81, 5.63, 11.25, 22.5, 45, 90, 180, 360, 720, and 1,440?g a.e. ha^?1), with six replications. The second experiment evaluated the response of U. decumbens plants to the application of a selected low dose of 11.25?g a.e. ha^?1. Evaluations of injury were performed at 0, 7, 14, and 21?days after application, and dry weight of plants was determined for each evaluation period. U. decumbens plants increased in dry weight when using the glyphosate dose of 11.25?g a.e. ha^?1. However, plants had different responses to the application of this low dose. It can promote both stimulation and inhibition of plant growth.     

Mercury in two fish species from the Paraná river floodplain, Paraná, Brazil

Total mercury concentrations were measured in dorsal muscle tissue of two edible fish species, Prochilodus scrofa 'curimba' and Pseudoplatystoma corruscans 'pintado', respectively detritivorous and carnivorous. Fish species were sampled monthly between February 1993 and January 1994 and bimonthly between April 1994 and February 1995 in three subsystems of Paraná river' system (Ivinhema River/Lake Patos; Baía River/Lake Guaraná and Paraná River/Cortado Channel), between Paraná and Mato Grosso do Sul. Total mercury was determined by HNO3/H2SO4/V2O5 digestion, SnCl2 reduction, and vapour generation method analysis (CGCH 900), adapted to Atomic Absorption Spectrometer (CGAA 7000 ABC). The mean mercury concentrations varied from 82.0 to 310.5 ng g(-1) and from 68 to 294.4 ng g(-1) in 'curimbas' and 'pintados', respectively. Mercury level increases in sexually mature 'curimbas'. Mercury values detected do not exceed the prevailing criteria for issuance of fish consumption advisories (< 500 ng g(-1)).     

Allelopathic potential and systematic evaluation of organic extracts from Canavalia ensiformis leaves (Jack beans)

This article describes the assessment of possible allelopathic potential of organic extracts obtained from leaves of Canavalia ensiformis under laboratory conditions. Furthermore, a systematic evaluation of these extracts was carried out using specific protocols developed in capillary electrophoresis (CE) to determine some groups of secondary metabolites. After the identification and quantification of compounds, the effects of compounds on germination of some common weeds was investigated, which are becoming a real problem in pastures in the state of Pará, Brazil.     

An evaluation of fishery co-management experience in an Amazonian black-water river (Unini River,Amazon, Brazil)

We evaluated the implementation of a fishing agreement, which was created by negotiation among all users of the resources as a co-management strategy because its definition was a result of meetings between all users of the resources. The fishing agreement was implemented in Unini River, a tributary of the right bank of Negro River. Our approach was based on the perception of the people who live in that area, called ribeirinhos. The management strategy was based on spatial distribution of the different types of fishing. We used two logistic regression models to identify the variables which are important to determine the previous concordance and satisfaction with the agreement. First, we analyzed the initial effort to implement the agreement. The variable that influenced the decision of support for the agreement and satisfaction with the results of agreement in both models was the distance from the interviewee’s residence to the sport fishing area. The results showed that the perception of improvement in well-being of the communities and structured social organization are crucial for the success of the co-management strategy.     

Environmental monitoring of water resources around a municipal landfill of the Rio Grande do Sul state,Brazil

Environmental Science and Pollution Research - In Brazil, landfills are commonly used as a method for the final disposal of waste that is compliant with the legislation. This technique, however,...     

Effect of impeller type and agitation on the performance of pilot scale ASBR and AnSBBR applied to sanitary wastewater treatment

The objective of this work was to assess the effect of agitation rate and impeller type in two mechanically stirred sequencing batch reactors: one containing granulated biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam (denominated AnSBBR). Each configuration, with total volume of 1 m³, treated 0.65 m³ sanitary wastewater at ambient temperature in 8-h cycles. Three impeller types were assessed for each reactor configuration: flat-blade turbine impeller, 45°-inclined-blade turbine impeller and helix impeller, as well as two agitation rates: 40 and 80 rpm, resulting in a combination of six experimental conditions. In addition, the ASBR was also operated at 20 rpm with a flat-blade turbine impeller and the AnSBBR was operated with a draft tube and helix impeller at 80 and 120 rpm. To quantify how impeller type and agitation rate relate to substrate consumption rate, results obtained during monitoring at the end of the cycle, as well as the time profiles during a cycle were analyzed. Increasing agitation rate from 40 rpm to 80 rpm in the AnSBBR improved substrate consumption rate whereas in the ASBR this increase destabilized the system, likely due to granule rupture caused by the higher agitation. The AnSBBR showed highest solids and substrate removal, highest kinetic constant and highest alkalinity production when using a helix impeller, 80 rpm, and no draft tube. The best condition for the ASBR was achieved with a flat-blade turbine impeller at 20 rpm. The presence of the draft tube in the AnSBBR did not show significant improvement in reactor efficiency. Furthermore, power consumption studies in these pilot scale reactors showed that power transfer required to improve mass transfer might be technically and economically feasible.