Imazaquin adsorbed on pillared clay and crystal violet-montmorillonite complexes for reduced leaching in soil

Ground water pollution due to herbicide leaching has become a serious environmental problem. Imazaquin [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)quinoline-3-carboxylic acid] is an herbicide used to control broadleaf weeds in legume crops. Imazaquin is negatively charged at the basic pH of calcareous soils and exhibits high leaching potential in soils. Our aim was to design formulation of imazaquin to reduce herbicide leaching. Imazaquin sorption on pillared clay (PC) and crystal violet (CV)-montmorillonite complexes was studied. The CV-montmorillonite complexes become positively charged with adsorption of CV above the cation exchange capacity (CEC) of montmorillonite, and thus can sorb imazaquin. The Langmuir equation provides a good fit to isotherms of imazaquin sorption on PC and CV-montmorillonite complexes, but for charged complexes an equation that combines electrostatics with specific binding was preferred. Maximal imazaquin sorption was 17.3 mmol kg-1 for PC and 22.2 mmol kg-1 for CV-montmorillonite complexes. The extents of imazaquin desorption into water were 21% for PC and 5% for CV-clay complexes. The presence of anions decreased imazaquin sorption on both sorbents in the sequence phosphate > acetate > sulfate. Reduction of imazaquin sorption by the anions and the extent of its desorption in electrolyte solutions were higher for PC than for CV-clay complexes. Leaching of imazaquin from CV-montmorillonite formulations through soil (Rhodoxeralf) columns was two times less than from PC formulations and four times less than that of technical imazaquin. The CV-montmorillonite complexes at a loading above the CEC appear to be suitable for preparation of organo-clay-imazaquin formulations that may reduce herbicide leaching significantly.     

Immediate and unexplained fetal death during mid-trimester amniocentesis

Immediate and unexplained fetal death during mid-trimester amniocentesis for prenatal diagnosis was found to be an uncommon though real phenomenon. A survey of programmes in the United States detected 5 cases from 7524 at 4 centres. Postmortem examination was not helpful and a neurogenic mechanism is postulated. Awareness of this phenomenon and routine pre- and post-amniocentesis ultrasound monitoring may clarify the actual prevalence and etiology.     

EMPHASIS ON DISTRIBUTION: STRATEGIES FOR SMALL SCALE WATER RESOURCES DEVELOPMENT IN THAILAND1

This paper discusses strategies for the development of water resources, emphasizing the delivery of reliable water supplies, for both domestic and production purposes, to every village and to every farmer. This necessitates a shift of emphasis from the construction of large storage reservoirs to the construction, operation, and maintenance of water distribution systems capable of reaching the largest number of farms, and a shift from projects that benefit the few, to projects that benefit the many. Water distribution in this context takes on three interrelated meanings: a geographical meaning, a technical meaning, and an economic meaning. The geographical meaning focuses on the spatial distribution of the recipient population as a key to identifying the proper distribution of water projects in physical space. The technical meaning relates to the physical distribution of water through canal systems to the farmers' fields. The economic meaning refers to the equitable distribution of benefits from water projects. The paper provides an illustration of the need for an emphasis on distribution, using the state of development of water resources in northeast Thailand as an example, with a proposed program for the further development of these resources. The northeast, the poorest region in the country, has been recognized by the Government of Thailand as a priority area for accelerated regional development efforts.