Phosphorus fractions and adsorption characteristics of floodplain sediments in the lower reaches of the Hanjiang River, China

The phosphorus fractions and adsorption characteristics of seven floodplain sediment samples collected in the lower reaches of China’s Hanjiang River were studied. Most phosphorus fractions showed a marked downstream increase in response to point-source inputs from urban areas. Total phosphorus (TP) contents in the sediments ranged from 603.68 to 945.25 mg.kg⁻¹. Inorganic phosphorus (IP) was the major component of TP, and calcium-bound phosphorus (Ca–P) was the major fraction of IP. The distribution characteristics of the phosphorus contents were affected by sediment grain size and hydrodynamic conditions. The maximum phosphorus adsorption capacities (Q _max) and the half-saturation concentration (k) were obtained using an improved Langmuir model. Native adsorbed exchangeable phosphorus content (w _NAP) and the zero-equilibrium phosphorus concentration value (c _EPC0) were subsequently calculated. The effects of sediment grain size, temperature, and disturbance on the phosphorus adsorption isotherms were also studied. The results showed that phosphorus adsorption on floodplain sediments was primarily chemisorption; the particle concentration effect played a more important role at a disturbance intensity of 150 r.min⁻¹ (on a shaker table) than at 100 r.min⁻¹.     

饮用水源致癌风险早期预警SNPs监测技术

综述了饮用水源污染致癌早期预警的单核苷酸多态性(single nucleotide polymorphisms,SNPs)检测技术,内容包括SNPs技术及其应用研究领域,癌症敏感基因与SNPs,饮用水源致癌早期预警SNPs监测技术等。该技术的应用对于早期诊断、预警、预防、控制饮用水源污染致癌,保护人体健康,保障后代生命安全,具有现实意义。     

Subcellular distribution op neurotoxic esterase activity in lamb and mouse brain

Abstract

Brain tissue samples of nice (7.5 g from 25 mouse brains and lamb (25 g) were homogenized and subcellular fractions prepared in order to assay the distribution of neurotoxic esterase (NTE) activity. The specific inhibitor, N,N‐diisopropylphosphorodiamidic fluoride (mipafox) was synthesized and purified. Maximum specific activity of NTE was reached in the microsomal fraction (110,000 g) while the enzyme activity in the soluble fraction (110,000 g) was extremely low. This subcellular distribution of NTE activity in mammal brains is an original contribution. Brain microsomal fraction is suggested to be a more reliable source for the highest activity of NTE. The specific activity of NTE of lamb brain was much higher than that of mouse brain. This night help interpretation of the characteristic species variation in susceptibility to NTE inhibitors which are known to be potent delayed neurotoxic agents.     

巢湖表层沉积物中重金属的分布特征及其污染评价

以巢湖表层沉积物为研究对象,利用BCR连续提取法研究了沉积物中Cr、Co、Ni、Cu、Cd、Zn、V和Pb等8种重金属元素的分布特征,同时运用潜在风险指数法和地累积指数法综合评价了巢湖沉积物中重金属的生态风险。结果表明,巢湖沉积物中的重金属含量在空间上表现出东西高、中间低的分布特征。巢湖表层沉积物中Cr、Co、Ni、V和Cu 5种重金属都主要以残渣态为主,Zn和Cd主要以弱酸提取态为主,Pb以可还原态为主,同时,Co和Cu 2种元素的可交换态及可还原态含量占有较高比例,具有潜在危害性。相关性分析显示,Cr、Cu、Pb、Ni、Zn和Cd 6种重金属元素的来源和分布可能具有相似性,Co和V 2种重金属元素具有相似的地球化学行为且其主要来源可能与其他几种重金属不同。潜在生态风险指数评价结果表明,巢湖表层沉积物中8种重金属元素构成的生态危害顺序为:Cd>Pb>Co>Cu>Ni>Zn>V>Cr,Cd具有高的生态危害等级,其他7种重金属元素均为低生态危害等级。地累积指数法评价结果表明:巢湖沉积物重金属元素的富集程度为Cd>Zn>Pb>Co>Cu>V>Ni>Cr,Cr属于清洁级别,Co、Cu、V和Ni处于轻度污染水平,Zn和Pb处于偏中度污染,Cd达到了重污染水平。     

利用蒸散比和气温模拟藏北高寒草甸的光能利用效率

光能利用效率(light use efficiency,LUE)是指初级生产力与植被冠层吸收的光合有效辐射(absorbed photosynthetically active radiation,APAR)之比,对LUE的准确定量化模拟是定量化模拟初级生产力的基础。研究利用一个基于通量观测的LUE模型(EC-LUE)模拟了2004-2005年藏北高寒草甸的LUE,该模型的参数只有蒸散比(Evaporative Fraction,EF)和气温(air temperature,T_a),EF和T_a分别为最大光能利用效率(maximum light use efficiency,LUE_max)的水分和温度胁迫因子,在研究中LUE_max取0.85 g C/MJ。EF和T_a对LUE_max的胁迫作用存在两种方式:连乘方式和最小限制因子方式,这两种方式模拟的光能利用效率分别记为LUE_multipEC和LUE_minEC,并与通量观测数据估算的LUE(LUE_EC)进行了比较。结果表明,LUE_minEC显著高估了LUE_EC,而LUE_EC和LUE_{multipEC差异不显著;LUEmultipEC和LUEminEC分别解释了89%以上LUEEC的季节变化;EF显著地解释了土壤表层含水量、 比湿,且在一定程度上解释了相对湿度的季节变化;相对于水分胁迫因子,温度胁迫因子更能够解释LUEEC的季节变化。因此,EC-LUE模型可以定量化高寒草甸LUE的季节变化,同时EF可以定量化高寒草甸生态系统水分状况的季节变化。}     

原生滩涂植被演替带土壤Cd形态分布及其生态风险评价

为了解原生滨海滩涂不同植被演替带土壤镉(Cd)的含量特征、赋存形态及生态风险,以盐城地区原生滨海滩涂为研究对象,利用BCR 3步提取法分析了不同植被演替带土壤Cd的含量及赋存形态,并采用平均沉积物质量基准系数法(SQG-Q)和风险评价准则(RAC)对Cd的潜在生态风险进行了初步评价。结果表明,原生滩涂土壤中总Cd(CdT)含量在2.21~3.61 mg·kg~(-1)之间,远高于江苏沿海土壤Cd背景值和国家土壤环境质量三级标准;不同植被演替带间,CdT含量表现为互花米草滩碱蓬滩芦苇滩光滩;SQG-Q系数显示该地区土壤CdT处于中等风险,互花米草滩风险相对较高;总体上原生滩涂土壤中可还原态Cd比例较低(12.8%),而酸溶态、可氧化态、残渣态三者差异不大(分别为28.2%、29.8%,29.2%);互花米草滩和芦苇滩酸溶态Cd比例(30.5%、37.0%)显著高于碱蓬滩和光滩(28.2%、20.6%),而残渣态Cd(21.5%、20.9%)则显著低于碱蓬滩和光滩(41.5%、45.6%);RAC评价结果显示,滩涂土壤Cd总体上呈现中等风险,而互花米草滩和芦苇滩达到高风险。以上结果显示,原生滨海滩涂土壤Cd已存在一定的生态风险,其中互花米草滩风险相对较高,随着互花米草的扩张及围垦面积的扩大,其重金属风险值得关注。     

温度对外源性重金属镉在土-水界面间形态转化的影响

通过室内培养试验、采用逐级提取法研究了不同温度(-30℃、10℃、30℃)对土壤中不同剂量外源重金属镉形态转化的影响。结果表明:在30℃和10℃条件下外源加入土壤中的镉以交换态为主,且在30℃条件下镉的活性要强于10℃。在-30℃条件下,当土壤中镉总量较高时,冷冻导致镉在短期内存在形态以残渣态为主,而在培养后期交换态镉的分配系数较大;当土壤中镉总量较低时冷冻过程使镉活性增强,交换态镉的分配系数较大。冷冻过程中有机质结合态镉的含量未检测出来,说明有机质与镉的螯合作用减弱。土壤中镉含量越多,非残渣态镉的相对含量也随之增高,镉的毒性相对也增强。     

风沙土不同有机组分对氨氮的解吸特征影响

采用平衡解吸法研究了风沙土不同有机组分对氨氮的解吸特征影响。结果表明,去除腐殖质后的风沙土氨氮解吸比例增加（由0.58增加到0.68）,同时,解吸迟滞性指数显著降低（由0.067降低到0.021）,说明腐殖质是影响风沙土氨氮解吸特征的重要因素;氨氮在轻组有机组分上的表面分配作用吸附是导致解吸比例增大,解吸迟滞性指数减小的原因;重组有机组分中的紧结态腐殖质（胡敏素）对氨氮的解吸起关键作用,它不但解吸比例较低（Dr=0.23）,而且解吸迟滞性指数较大（TⅡ=0.458）;氨氮在紧结态和稳结态腐殖质所形成的团聚体颗粒微孔隙中的不可逆吸附是导致解吸比例降低、解吸迟滞性指数增大的根本原因;考查土壤对氨氮的解吸特征不但要考虑有机质的含量,更要考虑有机质的存在形态,它也是影响土壤氨氮解吸特征的重要因素,轻组有机组分、重组有机组分及重组有机组分中的稳结态加紧结态腐殖质（HⅡ＋HⅢ组）和紧结态腐殖质（HⅢ组）携载的吸附态氨氮进入水体后,对上覆水体的扩散通量可分别按其饱和吸附量的0.94、0.58、0.33和0.23倍估算。     

土壤环境中镉、锌形态转化的探讨

论述了土壤中镉、锌的形态分布,讨论了影响土壤环境中Cd、Zn形态转化的因素和物质,如pH、石灰、有机质和其它一些离子和它们的影响机制,为治理土壤重金属污染提供理论依据。     

Investigation into atmospheric deposition through precipitation studies at New Delhi (India)

Rain water samples were collected during the monsoon of 1994, using automatic wet-only and manual bulk collectors at a height of 30 m above the ground at the National Physical Laboratory, New Delhi. The average pH of the rain water was 5.7 and its chemical composition was dominated by NH₄ and SO₄. The free acidity of the rain water was found to be due to S04 rather than N03 and it was mainly neutralized by NH₄ and Ca. Calculation of sea salt fraction and enrichment factor revealed that this site is free for marine influence. On an average the bulk samples had 13% higher concentration than that of wet-only samples which may be due to the deposition of soil-derived particles during the 24 h period of exposure. The higher neutralization factors of Ca and Mg in bulk samples and highest dry deposition rates for Ca in comparison to other components, indicated the positive interference of dust particles in neutralization.