增温和锌复合作用对菠菜富集多环芳烃的影响

目前有关增温和重金属复合作用对植物富集疏水性有机物的影响研究还鲜有报道.本文通过构建土壤-大气-植物密闭微宇宙,分析土壤、大气和植物中多环芳烃（Polycyclic aromatic hydrocarbons,PAHs）的浓度及土壤中PAHs降解菌基因的拷贝数,进而探究增温（+6℃）和锌胁迫（100~600 mg·kg^-1）及两者复合作用对菠菜富集4种氘代PAHs及其致癌风险的影响.结果表明,增温使菠菜根部中PAHs的浓度降低了1.5%~20.4%,这是由于增温促进了土壤中PAHs的生物降解,进而导致PAHs自由溶解态浓度降低;另外,增温也降低了根部脂肪的含量,从而降低PAHs在根部的富集作用.然而,菠菜根部中PAHs的浓度随土壤中锌浓度的增加而增加,且增加比例为1.2%~91.7%,这主要是因为锌抑制了土壤中PAHs的降解,进而增加了PAHs的自由溶解态浓度;另外,锌胁迫还增加了菠菜根部细胞膜的通透性,进而促进根部吸收PAHs.增温和锌胁迫条件下,菠菜茎叶中PAHs的浓度分别降低了7.3%~51.1%和增加了3.0%~76.9%,与对根部富集PAHs的影响一致,这归因于茎叶中的PAHs主要来源于根部的向顶运输而非大气的茎叶吸收.增温和锌复合作用对菠菜富集PAHs具有拮抗作用,这是因为两者对土壤中PAHs的生物降解具有相反的影响.在无外源PAHs输入下,增温和锌胁迫分别会降低和增加PAHs的总致癌风险.     

纳米二氧化钛对三价砷在大型蚤体内累积与毒性的影响

nTiO₂（纳米二氧化钛）可作为其吸附污染物的运输载体而影响污染物在生物体内的累积与毒性,为明晰nTiO₂吸附As（Ⅲ）（三价砷）后作为As的运输载体对水生物体内As累积与毒性的影响,以大型蚤（Daphnia magna）为受试生物,通过室内培养试验,研究了不同nTiO₂浓度、As（Ⅲ）不同暴露水平相互作用下蚤体中As与Ti的累积含量、毒性及其潜在作用机制.结果表明,nTiO₂可在30 min内吸附As（Ⅲ）至平衡,其中2、20 mg/L的nTiO₂对75 μg/L As（Ⅲ）的吸附率分别可达31.38%、51.84%,蚤体内As的累积含量分别为对照组的2.9和3.8倍,表明nTiO₂可作为运输载体提高As（Ⅲ）在大型蚤体内的累积;但不同As暴露水平下蚤体As和Ti含量的相关关系表明,nTiO₂作为载体的运输作用可能会因As暴露水平的增加而减弱.另外,nTiO₂虽然作为运输载体提高了As（Ⅲ）在大型蚤体内的累积,但并未增加As（Ⅲ）对大型蚤的毒性.添加2、20 mg/L的nTiO₂后,As（Ⅲ）对大型蚤的24 h IC₅₀（半抑制浓度）分别从0.93 mg/L增至2.53和2.97 mg/L,表明nTiO₂降低了As（Ⅲ）对大型蚤的毒性.研究显示,nTiO₂虽增加了As（Ⅲ）在大型蚤体内的累积,但却降低了As（Ⅲ）对大型蚤的毒性,这有利于对nTiO₂及其复合重金属污染风险的深入认识.      

Aerobic N2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

Nitrous oxide (N₂O) is a potent greenhouse gas that can be emitted during biological nitrogen removal. N₂O emission was examined in a multiple anoxic and aerobic process at the aeration rates of 600 mL/min sequencing batch reactor (SBR_L) and 1200 mL/min (SBR_H). The nitrogen removal percentage was 89% in SBR_L and 71% in SBR_H, respectively. N₂O emission mainly occurred during the aerobic phase, and the N₂O emission factor was 10.1% in SBR_L and 2.3% in SBR_H, respectively. In all batch experiments, the N₂O emission potential was high in SBR_L compared with SBR_H. In SBR_L, with increasing aeration rates, the N₂O emission factor decreased during nitrification, while it increased during denitrification and simultaneous nitrification and denitrification (SND). By contrast, in SBR_H the N₂O emission factor during nitrification, denitrification and SND was relatively low and changed little with increasing aeration rates. The microbial competition affected the N₂O emission during biological nitrogen removal.     

硒与硫单一及交互作用对小白菜生长及硒生物有效性的影响

用土培盆栽试验研究了硫酸盐、硒酸盐单一及交互作用对小白菜生长及其硒生物有效性的影响.结果表明,单施硒时,适量硒(≤1.0 mg·kg~(-1))能促进小白菜地上部的生长,表现为小白菜株高和地上部干重分别较不施硒对照处理增加了8.4%和22.1%(p0.05),但高剂量硒(≥2.5 mg·kg~(-1))却抑制其生长,小白菜株高和地上部干重分别较对照减少了0.4%、14.2%(2.5 mg·kg~(-1)Se)和15.8%、50.3%(5.0 mg·kg~(-1)Se).小白菜的根系对硒酸盐的胁迫更为敏感,单施硒处理小白菜根长和地下部干重均低于对照处理,且抑制作用随外源硒添加量的增加而增大,外源硒添加量为1.0、2.5、5.0 mg·kg~(-1)处理的小白菜的根长和地下部干重分别较对照下降了20.5%、28.3%、49.4%和29.2%、24.2%、58.5%.施硫能减缓硒对小白菜的胁迫,表现为相同硒剂量下,小白菜根长、地上和地下部干重均随外源硫剂量的增大而增加.另外,施硫处理小白菜叶绿素含量均显著高于相同硒剂量下的无硫处理,过氧化物酶活性却相反.相同硫剂量下,小白菜硒含量随外源硒添加量的增大而显著增大(p0.05),且地上部对硒的吸收和富集能力均显著大于地下部(p0.05).与此不同,施硫显著抑制小白菜对硒的吸收与富集(p0.05),小白菜地上、地下部硒含量和富集系数(BCFSe-shoot、BCFSe-root)均随外源硫剂量的增大而减小.小白菜生物量与其体内硒含量、硒富集系数呈显著负相关.由此可见,硫酸盐是通过抑制硒吸收和富集及调控小白菜自身的生理代谢来减缓硒酸盐对小白菜生长的胁迫.硫酸盐与硒酸盐的相互作用受硫剂量、硒剂量及植株部位的影响.     

强化曝气对潜流人工湿地堵塞物分布规律的影响

构建曝气及未曝气潜流人工湿地小试实验系统,研究曝气对人工湿地堵塞物组分及分布规律的影响.结果表明:两系统中堵塞物组成均以无机物为主,曝气对堵塞物累积总量影响不大,但对堵塞物化学组分影响较大,使堵塞物中有机物组分比例降低.未曝气及曝气系统堵塞物平均累积量分别为5.18 mg·g~(-1)及5.21 mg·g~(-1),有机物所占比例分别为28.4%和15.6%.曝气对堵塞物在水平及深度方向的分布影响不大,两系统均表现为底层累积物含量略高于表层,出水端累积物含量略高于进水端.电镜及能谱分析结果显示,受溶解氧因素的影响,两系统中表层填料元素种类均较底层丰富,且曝气系统较未曝气系统丰富.     

Long‐term mercury accumulation in the presence of cadmium and lead in oseochromis aureus (Steindachner)

Abstract

The effects of cadmium and lead on chronic mercury accumulation were investigated in O. aureus. After 140 days’ exposure the accumulation of mercury in the liver, brain, gill filaments, intestine, caudal muscle, spleen, trunk kidney and eye was analysed. The exposure concentrations were 0.05, 0.10 and 0.20 mg/L for mercury alone. O. aureus was also exposed to mixtures of 0.05 mg/L mercury with lead (0.05 mg/L and 0.50 mg/L or cadmium (0.05 mg/L) and 0.10 mg/L mercury with 0.10 mg/L cadmium. In food fish, a knowledge of toxic metal accumulation patterns is of great importance because of their contribution to the human diet and, as fishmeal, to the diet of agricultural animals. The trunk kidney consistently accumulated higher concentrations of mercury than any of the other tissues investigated.     

Accumulation and transportation of copper in different ecotypes of Leersia hexandra Swartz

ABSTRACT

This study used hydroponics with different copper (Cu) concentrations to assess metal accumulation and growth in two different populations of Leersia hexandra Swartz, one obtained from a contaminated area (CP) and the other from a non-contaminated area (NCP). Data demonstrated that Cu exerted a lesser effect on the biomass of CP than NCP. The root and shoot biomass measurements of CP were significantly higher than those noted at NCP. Copper concentration in the tissues of L. hexandra from CP increased markedly correlated with the concentration of metal in the culture solution, and this trend was stronger than that in NCP. Copper concentrations in roots and shoots were significantly higher in CP than NCP. As Cu stress levels in the culture solution rose, the transport coefficient of both populations decreased. Furthermore, the coefficient of CP was significantly higher than NCP. At a Cu concentration of 38.4 mg/L, the transfer factor value of CP is 40% higher than NCP. In summary, CP showed higher accumulation and resistance to Cu compared with NCP.     

NITROGEN ACCUMULATION IN A CONSTRUCTED WETLAND FOR DAIRY WASTEWATER TREATMENT1

ABSTRACT: A free water surface (FWS) constructed wetland was installed at a dairy in Glendale, Arizona, to study the potential of such a wetland to remove nitrogen (N) from wastewater. The study objectives were: (1) to determine N removal from the wastewater, and (2) to evaluate N accumulation in soil and plant tissues. The system consisted of eight cells (70 × 9 × 1.5 m) planted with Typha domingensis, Scirpus validus, and Phragmites australis. The four cells in series were lined with plastic, and the four cells in a parallel series were lined with clay. Cells received approximately 180 m³/d of partially treated dairy effluent. Plant tissues and soil samples were collected above and below ground from 24 locations during one year. Total N removal from wastewater was about 17 percent. Clay‐lined cells accumulated more N in the soil and less N in plant biomass compared with plastic lined cells. Plant biomass accounted for approximately 60 percent of total N accumulated in cells with dense plant communities. Ninety percent of accumulated soil N was organic. Total N accumulated in soil reached a maximum (1,100 mg/kg) eight months after the introduction of wastewater.     

反馈环断裂下的安全知识积累与扩散仿真研究

为了研究个体死亡引发反馈环断裂对安全知识积累和扩散的影响，采用元胞自动机方法，构建了多层次、多状态、多行为的安全知识积累和扩散演化模型。然后运用交替变量控制法进行仿真实验，获取605组数据，并对所得数据进行层次回归分析。研究结果表明:个体死亡会阻碍安全知识积累且会加剧个体间知识差异，同时事故率的增加会提高知识积累机会和个体死亡机会，产生复杂的双向对冲效应；替代者知识水平能够对安全知识积累和扩散产生较大的正向影响，并能削弱个体死亡的负向影响；事故见证者的增加也能够产生一定的正向影响。据此提出“数量型死亡悖论”，并指出促进安全知识积累和扩散的重点方向。     

iTree‐Hydro: Snow Hydrology Update For The Urban Forest Hydrology Model1

Yang, Yang, Theodore A. Endreny, and David J. Nowak, 2011. iTree‐Hydro: Snow Hydrology Update for the Urban Forest Hydrology Model. Journal of the American Water Resources Association (JAWRA) 47(6):1211–1218. DOI: 10.1111/j.1752‐1688.2011.00564.x Abstract: This article presents snow hydrology updates made to iTree‐Hydro, previously called the Urban Forest Effects—Hydrology model. iTree‐Hydro Version 1 was a warm climate model developed by the USDA Forest Service to provide a process‐based planning tool with robust water quantity and quality predictions given data limitations common to most urban areas. Cold climate hydrology routines presented in this update to iTree‐Hydro include: (1) snow interception to simulate the capture of snow by the vegetation canopy, (2) snow unloading to simulate the release of snow triggered by wind, (3) snowmelt to simulate the solid to liquid phase change using a heat budget, and (4) snow sublimation to simulate the solid to gas phase via evaporation. Cold climate hydrology routines were tested with research‐grade snow accumulation and weather data for the winter of 1996‐1997 at Umpqua National Forest, Oregon. The Nash‐Sutcliffe efficiency for open area snow accumulation was 0.77 and the Nash‐Sutcliffe efficiency for under canopy was 0.91. The USDA Forest Service offers iTree‐Hydro for urban forest hydrology simulation through http://www.iTreetools.org .