Pesticide and agro-ecological transition: assessing the environmental and human impacts of pesticides and limiting their use

Environmental Science and Pollution Research -     

Experimental study and modeling of the transfer of zinc in a low reactive sand column in the presence of acetate

Nowadays, it is necessary to understand and identify the reactions governing the fate of heavy metals introduced into the environment with low complexing organic compounds, particularly when they are transferred through soils in urban areas. In this work the concomitant influence of pH and acetate on the fate of zinc on siliceous sand was studied in batch and non-saturated column experiments. Total zinc concentrations varied between 2 and 20 mg/l, and total acetate concentrations were fixed at 22, 72, 132, and 223 mM to obtain solution pHs of 4, 5, 6 and 7, respectively. Natural sand (diameter, 0.3-2 mm), mainly constituted of silica, was used. In batch adsorption experiments, zinc adsorption is insignificant at pH 4, low and linear at pH 5, and increasingly nonlinear, of the Langmuir type, at pH 6 and 7 indicating near-saturation conditions of surface sites at these high pH values. In column experiments, Zn retardation increases and the maximum outlet concentration of Zn decreases with rising pH and acetate concentrations. Previous column tracer experiments revealed the occurrence of regionalized water transport in the column. Modeling these data was based on a non-electrostatic approach. Batch and column data modeling was based on the PHREEQC code that allows concomitant resolution of chemical speciation and regionalized water transport. The speciation calculation indicates that the ZnAcetate+ species is the dominant Zn species in the solutions used. Batch experimental curves are correctly modeled assuming the formation of the three surface species triple bond SiOZn+, triple bond SiOH-Zn Acetate+ and triple bond SiO-Zn(Acetate)2-. The column data could be adequately modeled assuming a two-region water transport and the formation of the same three species with the same thermodynamic constants determined in the batch experiments. The hypothesis of the modeling leads to a slight overestimation of the quantities of zinc eluted (10%) at pH 6 and 7, mostly in the desorption phase. These results show that the methodology used facilitates the correct modeling of both batch and transport experiments and formulation of the hypothesis on the interactions between the low reactive sand and a complex solution.     

用低空间分辨率的新近卫星图像对东南亚岛屿的森林覆被进行制图

本研究提供了东南亚岛屿亚区用空间低分辨率(1km)SPOT植被卫星图像对热带森林覆被进行制图的一个实例.卫星镶嵌图像源自1998～2000年卫星图像.通过非监督数字分类对森林覆被进行制图.然后将制图结果与一些亚区挑选的森林图进行对比,表明该图不仅具有提供森林面积范围和分布等基础资料的潜力,而且还可以提供亚区中森林大面积变化的信息.我们发现,从该亚区森林图所得到的森林面积估计与FAO搜集的数据相似.结果表明,如果毁林以目前或以前的速度继续进行,那么在不远的将来,东南亚现存的木材资源丰富、生物多样性高的许多热带森林可能消失.     

Sulphonated aromatic pollutants

Many synthetic sulphonated aromatic compounds are used as starting material to produce dyes and pigments, or are released as by-products in the effluents of the textile and dye industry. A large number of these chemicals are poorly biodegradable and cannot be eliminated by classical wastewater treatment plants. To limit the impact of these pollutants on the environment, new processes, based on the use of higher plants (constructed wetlands or hydroponic systems), are under development. Detergents and surfactants are essential for both industrial and domestic applications, the most important family being the alkylbenzene sulphonates. Originally, the alkyl side chains were branched and thus recalcitrant to biodegradation. Therefore, they have been replaced by linear alkylbenzene sulphonates. Although more acceptable, present formulations still have adverse environmental and toxic effects. In this context, phytoremediation appears to be a promising approach to remove these compounds from contaminated soils and waters.     

New Approaches to Creative Conservation on Farms in South-west England

This paper reports findings from research which sought to examine the characteristics and the behaviour of farms which participate in environmentally friendly farming schemes and initiatives. In contrast with some earlier work in other regions, a wide variety of farmers in the south-west sample had an active level of sympathy or interest in conservation issues, which, despite the broad and at times inaccurate conservation definitions employed by the farmers, led some to spend generously on creative activities, especially woodland planting. However, the importance of geographical influences was paramount, with creative conservation activity almost always undertaken on comparatively poorer land. Poorer land was always most suitable for conservation work, whether that work be done for cosmetic or holistic reasons.     

Copper, Copper Mining Effluents and Grazing as Potential Determinants of Algal Abundance and Diversity in Northern Chile

We experimentally tested threealternative hypotheses to explain the low algaldiversity and abundance in an intertidal zonereceiving the effluents of the copper mine El Salvadorin northern Chile. Our results demonstrated thatalgae were able to grow at the levels of dissolvedcopper detected in coastal waters of the area. Duringthe assays, growth and regeneration in several red,green and brown adult algae and juvenile Lessonia nigrescens were normal at copper levels of150 g L^-1 or, in some cases, higher. Wealso found that the coastal sea water mixed with theeffluent was not lethal to algae, although in somecases minor effects on growth were detected. Theseresults indicate that today's low algal diversity andabundance can not be explained by the current copperlevels in the area nor by the effect of the effluent.Exclusion of grazers, however, resulted in a fastcolonization by various algal species. This, togetherwith atypically high grazer density at the areas underthe influence of the effluent, strongly suggests thatherbivory, a factor not directly related to the miningoperation, is likely to be responsible for the lowalgal diversity and abundance in the studied locality.     

Pedestrian crossing decision-making: A situational and behavioral approach

Among road users, pedestrians are those whose continued trajectory is the less constrained by the environment and by the regulation rules. Consequently, the choice of where, when and how to cross roads are more or less conforming with the awaited behavior. Proceeding with an experimental approach, from observations of pedestrian crossings to the modeling of the decision-making process, a categorization of both environments and of pedestrian behavior is proposed.