四川省环境饮水的^3H水平,分布及评价

本文报道了四川省20市、地、州的环境饮水(自来水、井水及部分江河、湖库、泉水)中之~3H辐射水平、变化规律与分布特点,对其影响因素进行了简要探讨和评价。 3H(氚)是氢的唯一放射性同位素,发射低能炖β粒子,在许多生产和研究领域得到了日益广泛的应用。它是核燃料循环中可能对环境产生较大影响的核素之一,更是未来的能源——可控热核反应堆可能对环境产生影响的主要核素。因此,氚是人们进行核环境评价时感兴趣的主要放射性核素之一。事实上氚,是水体中含量最高的放射性核素。因此,氚在环境水中的现状,以及对氚进行有效的监测监督,已成为人们十分关注的问题。     

Effect of Light on Biodegradation of Estrone, 17β‐Estradiol,and 17α‐Ethinylestradiol in Stream Sediment

Biodegradation of [A‐ring ¹⁴C] Estrone (E1), 17β‐estradiol (E2), and 17α‐ethinylestradiol (EE2) to ¹⁴CO₂ was investigated under light and dark conditions in microcosms containing epilithon or sediment collected from Boulder Creek, Colorado. Mineralization of the estrogen A‐ring was observed in all sediment treatments, but not epilithon treatments. No difference in net mineralization between light and dark treatments was observed for ¹⁴C‐E2. Net mineralization of ¹⁴C‐E1 and ¹⁴C‐EE2 was enhanced in light treatments. Extents of ¹⁴CO₂ accumulation and rates of mineralization were significantly greater for E2 than E1 under dark conditions, but were comparable under light conditions. These results indicate substantial differences in the uptake and metabolism of E1 and E2 in the environment and suggest biorecalcitrance of E1 relative to E2 in light‐limited environments. The extent of ¹⁴CO₂ accumulation and rate of mineralization for EE2 in dark treatments were less than half of that observed for E2 and generally lower than for E1, consistent with previous reports of EE2 biorecalcitrance. However, ¹⁴CO₂ accumulation and rates of mineralization were comparable for EE2, E2, and E1 under light conditions. These results indicate photoactivation and/or phototransformation/photodegradation processes can substantially enhance heterotrophic biodegradation of estrogens in sunlit environments and may play an important role in estrogen transport and attenuation.     

Effect of Cry3Bb transgenic corn and tefluthrin on the soil microbial community: biomass, activity, and diversity

Transgenic Bt corn expressing the Cry3Bb insecticidal protein active against corn rootworm (CRW) (Diabrotica spp.; Coleoptera: Chrysomelidae) was released for commercial use in 2003 and is expected to be widely adopted. Yet, the direct and indirect risks to soil microorganisms of growing this CRW-resistant Bt corn versus applying insecticides to control the rootworm have not been assessed under field conditions. The effects of CRW Bt corn and the insecticide tefluthrin [2,3,5,6-tetrafluoro-4-methylbenzyl (Z)-(1RS)-cis-3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclopropanecarboxylate] on soil microbial biomass, activity (N mineralization potential, short-term nitrification rate, and soil respiration), and bacterial community structure as determined by terminal restriction fragment length polymorphism (T-RFLP) analysis were assessed over two seasons in a field experiment. Bt corn had no deleterious effects on microbial activity or bacterial community measures compared with the non-transgenic isoline. The T-RFLP analysis indicated that amplifiable bacterial species composition and relative abundance differed substantially between years, but did not differ between rhizosphere and bulk soils. The application of tefluthrin also had no effect on any microbial measure except decreased soil respiration observed in tefluthrin-treated plots compared with Bt and non-transgenic isoline (NoBt) plots in 2002. Our results indicate that the release of CRW Bt corn poses little threat to the ecology of the soil microbial community based on parameters measured in this study.