有机氯农药在岩溶区上覆土壤中的垂直迁移特征及对地下水的影响

选取典型表层岩溶泉域内的土壤剖面和表层岩溶泉水为研究对象,采用气相色谱(GC-μECD)对土壤和地下水中的有机氯农药(organochlorine pesticides,OCPs)进行定量分析,研究了有机氯农药在岩溶区上覆土壤中的垂直迁移以及对地下水的影响.结果表明,研究区所有土壤剖面中,HCHs和DDTs均有检出.HCHs和DDTs的含量范围分别为:0.77~18.3 ng·g-1(平均5.16 ng·g-1)和0.34~226 ng·g-1(平均16 ng·g-1).研究区土壤中的HCHs和DDTs峰值主要出现在土壤亚表层.在一年的观测期间,4个表层岩溶泉中均有HCHs和DDTs检出.泉水中HCHs和DDTs的含量范围分别为:2.09~60.1 ng·L-1(平均12 ng·L-1)和N.D~79.8 ng·L-1(平均9.16 ng·L-1).后沟泉、柏树湾泉、兰花沟泉的HCHs和DDTs含量以及水房泉中的HCHs含量均呈现出雨季高于旱季的特点.泉水中的HCHs、DDTs含量与泉域内土壤中的HCHs、DDTs含量并没有很好的对应关系.研究表明,TOC、土壤含水量、黏粒含量、p H均对后沟泉域土壤中有机氯农药垂直迁移产生抑制作用,致使后沟泉域土壤中有机氯农药含量虽然在4个泉域中最高,但泉水中的含量却最低.而在水房泉泉域,这4个因素对有机氯农药的垂直迁移均没有抑制作用,因此水房泉泉域土壤中有机氯农药含量虽然最低,但泉水中有机氯农药的含量却较高.     

Effects of elevated atmospheric CO2 concentration and temperature on the soil profile methane distribution and diffusion in rice-wheat rotation system

The aim of this experiment was to determine the impacts of climate change on soil profile concentrations and diffusion effluxes of methane in a rice–wheat annual rotation ecosystem in Southeastern China. We initiated a field experiment with four treatments:ambient conditions(CKs), CO_2 concentration elevated to ~ 500 μmol/mol(FACE),temperature elevated by ca. 2°C(T) and combined elevation of CO_2 concentration and temperature(FACE + T). A multilevel sampling probe was designed to collect the soil gas at four different depths, namely, 7 cm, 15 cm, 30 cm and 50 cm. Methane concentrations were higher during the rice season and decreased with depth, while lower during the wheat season and increased with depth. Compared to CK, mean methane concentration was increased by 42%, 57% and 71% under the FACE, FACE + T and T treatments, respectively, at the 7 cm depth during the rice season(p 0.05). Mean methane diffusion effluxes to the 7 cm depth were positive in the rice season and negative in the wheat season, resulting in the paddy field being a source and weak sink, respectively. Moreover, mean methane diffusion effluxes in the rice season were 0.94, 1.19 and 1.42 mg C/(m~2·hr) in the FACE,FACE + T and T treatments, respectively, being clearly higher than that in the CK. The results indicated that elevated atmospheric CO_2 concentration and temperature could significantly increase soil profile methane concentrations and their effluxes from a rice–wheat field annual rotation ecosystem(p 0.05).     

基于病毒宏基因组学鉴定水环境中噬菌体携带的新型耐药基因及其耐药特点分析

水环境作为耐药基因的存储库，为耐药基因的水平转移和新型耐药基因的产生提供重要场所.但到目前为止，对水环境中病毒携带耐药基因的特征及其功能还知之甚少.因此以南四湖和东平湖为研究对象，利用病毒宏基因组学结合体外实验的方法探讨水环境中病毒携带新型耐药基因的情况及其耐药特点.通过分析病毒基因组的片段（reads）和重叠群（contigs），鉴定出多种耐药基因，包括AAC（6’）、Qnr A、Van Y、Vat和β-内酰胺酶基因.值得关注的是，通过核心序列比对和进化分析，挖掘出两种噬菌体携带的新型β-内酰胺酶基因bla_NSDPV-1和bla_NSVM-1.最小抑菌浓度试验表明，这两种编码新型β-内酰胺酶的耐药基因对临床常用头孢类和碳青霉烯类抗生素具有一定的耐药性.综上所述，水环境中噬菌体很可能在新型耐药基因的产生和耐药基因散播中起着重要的作用.另外，病毒宏基因组学结合体外实验是发现噬菌体携带新型耐药基因的重要方法.