土壤中滴滴涕的来源·风险与修复

DDT禁用几十年后,土壤中DDT的历史残留依然存在,同时新兴污染源使土壤中DDT污染状况有所改变。有关DDT的毒理学、健康风险评估研究也有了新的进展。综述了近年土壤中DDT的来源、毒性及健康风险最新研究成果,在此基础上介绍了较成熟的被DDT污染土壤的修复技术,为土壤中DDT的管控工作提供技术支持。     

Resistance to DDT in the mosquito fish,Gambusia affinis

Mosquito fish from waters near cotton fields that have had a long history of treatment with chlorinated hydrocarbon pesticides exhibited a marked resistance to DDT compared with fish from areas which had had no past exposure to insecticides.     

Carbonic anhydrase interaction with DDT, DDE, and dieldrin

The active site of various carbonic anhydrases is not blocked by DDT. DDE, or dieldrin. Impairment of catalytic efficiency can only be documented in opalescent test solutions in which the insecticides are present in excess of their solubility limit. These slowly forming precipitates occlude enzyme from solution and furnish a physical explanation of the supposed inhibition. The amounts occluded depend, among other things, on the conformational and topographical characteristics of the particular carbonic anhydrase molecules.     

Quantum phase transition in organic charge-transfer complexes

A phase transition in an organic charge-transfer complex, which originates from the neutral-ionic valence instability, can be tuned toward zero kelvin with use of external pressure or chemical modification as a control parameter. The phase diagram and observed dielectric behaviors are typical of quantum paraelectricity, yet this zero-kelvin transition point namely, the quantum critical point, accompanies large quantum fluctuation of the molecular charge, as demonstrated by the molecular vibrational mode spectra. The result indicates that the pi-electron transfer between donor and acceptor molecules is coupled with the zero-point lattice dynamics around the quantum critical point.     

DDT in the biosphere: where does it go?

The worldwide pattern of movement of DDT residues appears to be from the land through the atmosphere into the oceans and into the oceanic abyss. Calculations based on the fragmentary data available on. rates of movement and sizes of various pools of DDT residues lead to the conclusion that concentrations in the atmosphere and in the mixed layer of the oceans lag by only a few years behind the amounts of DDT used annually throughout the world. A model suggests that maximum concentrations of DDT residues occurred in air in 1966 and will occur in the mixed layer of the oceans in 1971. The biota probably contains in total less than 1/30 of 1 year's production of DDT during the mid-1960's, a very small amount in proportion to the total potentially available. The reason for the biota's failure to absorb larger quantities and to be affected much more severely is unclear. The analysis suggests that mere good fortune has protected man and the rest of the biota from much higher concentrations, thus emphasizing the need to determine the details of the movement of DDT residues and other toxins through the biosphere and to move swiftly to bring world use of such toxins under rational control based on firm knowledge of local and worldwide cycles and hazards.     

DDT tissue retention: sudden rise induced by the addition of aldrin to a fixed DDT intake

The oral administration of aldrin to male and female beagles, whose diet already included a fixed, regular oral dosage of DDT, resulted in a dramatic rise in the concentrations of DDT, DDE, and DDD in blood and fat.     

DDT: interaction with nerve membrane conductance changes

The falling phase of action potentials of lobster giant axons is prolonged by DDT; finally a plateau phase is produced like cardiac action potentials. In axons poisoned with DDT, peak transient (sodium) currents associated with step depolarizations are turned off very slowly, and steady-state (potassium) currents are markedly suppressed. These two changes would cause the prolongation of action potentials and are considered the major ionic mechanisms of DDT action.     

Dechlorination of DDT in frozen blood

Dechilorination of a commercial mixture of o, p'-DDT and p, ppDDT to p, p'-DDD and p, p'-DDE occiurs in avian blood stored at-20 degrees C, indicatinig nonenzymalic degradation. The subsequent disappearance of these two metabolites suggests conversion to other metabolites which cannot be detected by gas chromatography with an electron-captutre detector.