Solar photocatalytic degradation of some hazardous water-soluble pesticides at pilot-plant scale

The technical feasibility and performance of photocatalytic degradation of six water-soluble pesticides (cymoxanil, methomyl, oxamyl, dimethoate, pyrimethanil and telone) have been studied at pilot-plant scale in two well-defined systems which are of special interest because natural solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. TiO(2) photocatalysis tests were performed in a 35L solar pilot plant with three Compound Parabolic Collectors (CPCs) under natural illumination and a 75L solar pilot plant with four CPC units was used for homogeneous photocatalysis tests. The initial pesticide concentration studied was 50 mg L(-1) and the catalyst concentrations employed were 200 mg L(-1) of TiO(2) and 20 mg L(-1) of iron. Both toxicity (Vibrio fischeri, Biofix) and biodegradability (Zahn-Wellens test) of the initial pesticide solutions were also measured. Total disappearance of the parent compounds and nearly complete mineralization were attained with all pesticides tested. Treatment time, hydrogen peroxide consumption and release of heteroatoms are discussed.     

碳酸钙表面改性剂磷酸酯的合成及其在塑料体系中的应用

本文在较佳合成条件下合成了不同碳链长度的烷基磷酸酯表面活性剂，并对产物进行了表征。该产品用于轻质碳酸钙的改性，当用量为2．5％（改性剂／碳酸钙质量比）时，可明显改善塑料填料CaCO3的表面性能及填充性能，对软PVC体系的加工性能及力学性能有明显的改善作用。且单酯改性的加工性能优于相同碳链长度的双酯。     

Insecticide resistance and synergism in Brazilian populations of Sitophilus zeamais (Coleoptera: Curculionidae)

Insecticide resistance to three organophosphate (chlorpyrifos-methyl, malathion and pirimiphos-methyl) and three pyrethroid (cypermethrin, deltamethrin and permethrin) insecticides was surveyed in nine field-collected populations of the maize weevil from six Brazilian States and contrasted with a standard susceptible population and a DDT and pyrethroid resistant population. Bioassay tests were carried out in glass vials (20 ml) impregnated with dried insecticide residue and the resistant populations were recognized by using discriminating concentrations established from LC₉₅s estimated for a standard susceptible population. Four field-collected populations had reduced susceptibility to cypermethrin (64-77% mortality) and to chlorpyrifos-methyl (76-77% mortality). All populations were susceptible to malathion and pirimiphos-methyl and only the DDT and pyrethroid resistant check showed resistance to all pyrethroids. Concentration-mortality curves showed non-significant levels of insecticide resistance in the field-collected populations and moderate (10-100-fold) to very high levels (>1000-fold) of resistance to pyrethroids in the DDT and pyrethroid resistant population. Results from insecticide bioassays with synergists (diethyl maleate, piperonyl butoxide, and triphenyl phosphate) suggested a major involvement of esterase as the cypermethrin resistance mechanism, while no clear result was obtained for chlorpyrifos-methyl. Synergism results provide support for target site resistance to pyrethroids in the DDT and pyrethroid resistant population used in this study.     

Clef topo-toxicity by cubic representations of organophosphates

The present article studies a series of organophosphate analog molecules used as pesticides. The study involves calculations of some of the most relevant connectivity indices (as Wiener Index, Topological Efficiency Index, Novel Topological Efficiency Index) for the two-dimensional graphs of the studied molecules obtained through the classic QSAR rules. A cubic system with nodes, conceived for packing/superposing the vertices of the studied graphs led to different adjacencies of the vertices in the packed graphs, so to new connectivity indices, named three-dimensional connectivity indices. The new connectivity indices prove better correlation properties with aspects as toxicity and biological activity as enzyme inhibitors (expressed as lethal doses or inhibitory concentrations) than the two-dimensional indices thus the cubic mode of the topological study of molecular graphs could represent a variant of initial in silico studies for determining in analog series the molecules with best activities or improved toxicological characteristics.     

Dietary intake of pesticides: State of Kuwait total diet study

The State of Kuwait conducted a total diet study (TDS) to determine the dietary intakes of selected pesticides. This paper reports the results of this study. A national food consumption survey was performed and core food lists for different population groups were established representing the total diet of the Kuwaiti population. Food items (table-ready) were purchased/prepared and analysed for their contents of organophosphate/organochlorine carbamate, benzimidazole and phenylurea pesticides according to the US FDA Pesticide Analytical Manual (PAM I). Dietary intakes of these pesticides are presented for 19 population groups, which range from infants to elderly adults. The intakes of selected population groups are compared with representative findings from the US FDA/TDS and data published from other countries. In general, the average daily intakes were well below acceptable limits, but higher than those reported from developed countries.