Effects of high ammonium level on biomass accumulation of common duckweed Lemna minor L.

Growing common duckweed Lemna minor L. in diluted livestock wastewater is an alternative option for pollutants removal and consequently the accumulated duckweed biomass can be used for bioenergy production. However, the biomass accumulation can be inhibited by high level of ammonium (NH₄ ⁺) in non-diluted livestock wastewater and the mechanism of ammonium inhibition is not fully understood. In this study, the effect of high concentration of NH₄ ⁺ on L. minor biomass accumulation was investigated using NH₄ ⁺ as sole source of nitrogen (N). NH₄ ⁺-induced toxicity symptoms were observed when L. minor was exposed to high concentrations of ammonium nitrogen (NH₄ ⁺-N) after a 7-day cultivation. L. minor exposed to the NH₄ ⁺-N concentration of 840 mg l^?1 exhibited reduced relative growth rate, contents of carbon (C) and photosynthetic pigments, and C/N ratio. Ammonium irons were inhibitory to the synthesis of photosynthetic pigments and caused C/N imbalance in L. minor. These symptoms could further cause premature senescence of the fronds, and restrain their reproduction, growth and biomass accumulation. L. minor could grow at NH₄ ⁺-N concentrations of 7–84 mg l^?1 and the optimal NH₄ ⁺-N concentration was 28 mg l^?1.     

Sensitivity analysis of source regions to PM2.5 concentration at Fukue Island,Japan

The authors analyze the sensitivities of source regions in East Asia to PM_2.5 (particulate matter with an aerodynamic diameter of ≤2.5 µm) concentration at Fukue Island located in the western part of Japan by using a regional chemical transport model with emission sensitivity simulations for the year 2010. The temporal variations in PM_2.5 concentration are generally reproduced, but the absolute concentration is underestimated by the model. Chemical composition of PM_2.5 in the model is compared with filter sampling data in spring; simulated sulfate, ammonium, and elemental carbon are consistent with observations, but mass concentration of particulate organic matters is underestimated. The relative contribution from each source region shows the seasonal variation, especially in summer. The contribution from central north China (105°E–124°E, 34°N–42°N) accounts for 50–60% of PM_2.5 at Fukue Island except in summer; it significantly decreases in summer (18%). Central south China (105°E–123°E, 26°N–34°N) has the relative contribution of 15–30%. The contribution from the Korean Peninsula is estimated at about 10% except in summer. The domestic contribution accounts for about 7% in spring and autumn and increases to 19% in summer. We also estimate the relative contribution to daily average concentration in high PM_2.5 days (>35 μg m^?3). Central north China has a significant contribution of 60–70% except in summer. The relative contribution from central south China is estimated at 46% in summer and about 30% in the other seasons. The contributions from central north and south China on high PM_2.5 days are generally larger than those of their seasonal mean contributions. The domestic contribution is smaller than the seasonal mean value in every season; it is less than 10% even in summer. These model results suggest that foreign anthropogenic sources have a substantial impact on attainment of the atmospheric environmental standard of Japan at Fukue Island.

Implications: The contribution from several source regions in East Asia to PM_2.5 concentration at Fukue Island, a remote island located in the western part of Japan and close to the Asian continent, is estimated using a three-dimensional chemical transport model. The model results suggest that PM_2.5 that is attributed to foreign anthropogenic sources have a larger contribution than that of domestic pollution and have a substantial impact on attainment of the atmospheric environmental standard of Japan at Fukue Island.     

环境工艺方法论研究——利用自然法

利用自然法是开发环境工艺技术的一般方法。本文对利用自然法在环境工程工艺中的应用进行了总结,并且论述了其哲学内涵。     

Arsenic, cadmium, and lead in California cropland soils: role of phosphate and micronutrient fertilizers

Phosphate and micronutrient fertilizers contain potentially harmful trace elements, such as arsenic (As), cadmium (Cd), and lead (Pb). We investigated if application of these fertilizer increases the As, Cd, and Pb concentrations of the receiving soils. More than 1000 soil samples were collected in seven major vegetable production regions across California. Benchmark soils (no or low fertilizer input) sampled in 1967 and re-sampled in 2001 served as a baseline. Soils were analyzed for total concentrations of As, Cd, Pb, P, and Zn. The P and Zn concentrations of the soils were indicators of P fertilizer and micronutrient inputs, respectively. Results showed that the concentrations of these elements in the vegetable production fields in some production areas of California had been shifted upward. Principal component analysis and cluster analysis showed that the seven production areas could be sorted into three categories: (i) enrichment of As, Cd, and Pb, which was associated with the enrichment of P and Zn in one of the seven areas surveyed; (ii) enrichment of As, which was associated with enrichment of Zn in two of the seven areas surveyed; and (iii) no remarkable correlation between enrichment of As, Cd, and Pb and enrichment of P and Zn in the other four areas surveyed.     

Tissue-dependent distribution and accumulation of chlorobenzenes by vegetables in urban area

Five seasonal vegetables from three growing sites in Hangzhou city, Zhejiang Province, were studied for the levels of four chlorobenzenes(CBs): o-dichlorobenzene (o-DCB), p-dichlorobenzene (p-DCB), m-dichlorobenzene (m-DCB), and 1,2,4-trichlorobenzene (1,2,4-TCB). Samples of each vegetable from each site were subdivided into leaves, stems, and roots, and these subsamples were analyzed separately for the levels of accumulated CBs. Relations between the levels of CBs in vegetables with the total organic carbon (TOC) of the soil, the lipid content of the vegetable, and the physicochemical properties of CBs were established. Results showed that o-DCB, p-DCB, m-DCB, 1,2,4-TCB were present in all vegetables analyzed. For spinaches (Spinacia oleracea), Chinese cabbages (Brassica rapa var. pekinensis), and celery (Apium graveolens var. dulce), the highest level of CBs was with roots, followed by leaves. While for radishes (Raphanus sativus), and carrots (Daucus carota subsp. sativus), the highest level was with leaves, followed by stems. The accumulation of CBs was found to have a good correlation with the plant-tissue lipid content, the contaminant air-water Henry's coefficient (H), the contaminant octanol-water partition coefficient (K(ow)), and the physiological characteristics of the vegetables.     

基于水足迹的流域生态补偿标准模型研究

流域水资源是一种公共物品,其系统的整体性以及资源外部性等特征要求各相关区域应共同承担环境保护.如何衡量各区域水资源开发利用与环保投入的关系,建立合理的生态补偿标准模型,已成为流域管理研究领域普遍关注的问题.本文运用水足迹理论和方法,界定流域水足迹内涵,通过反映流域沿岸各区域水生态服务耗费情况判断分析水生态系统安全状态,提出流域生态补偿标准计量流程及不同情况下的流域生态补偿标准测算模型,从而客观、准确地量化流域生态补偿额度,为管理者正确分析和解决流域各区域间利益冲突提供科学的决策依据与支持.同时本文以碧流河为案例,收集并分析了2002-2006年间碧流河沿岸各行政区水足迹和环保投入情况,理清各区域生态系统状态及相互关系,计算补偿标准,进而验证模型的可行性.     

基于模糊规则的社会力模型改进研究

针对社会力模型人员作用范围系数进行优化,基于模糊规则改进模型中人员作用范围,使其成为受到疏散速度、疏散人员间距共同影响的动态参数,使模型中人员可通过自身模糊经验判断实际速度、人员交互距离状态来确定心理期望作用范围。仿真结果符合真实疏散特性,证明了人员作用范围系数受人员运动状态的动态影响,并提供参考模糊规则制定原则。     

九曲桥行人运动实验与模拟研究

公共场所中的人群疏散是行人疏散动力学研究中的重要内容。基于九曲桥行人运动观测实验对转角区域的行人运动特征进行研究,并利用人员疏散模拟软件Pathfinder模拟了因激励作用所导致的行人速度提高对通行效率的影响。结果表明,由于行人的停留、拍照行为导致转角内区域出现了明显的行人变换走道现象;行人在转角内区域出现的停留、超越行为导致行人速度出现大幅度波动,最低速度约为0.2 m/s,最高速度约为0.7 m/s;与转角后区域相比,行人密度变化对转角内区域的行人速度的影响更小,单位流量的影响更大;由于观测实验中行人停留、拍照等行为的存在,相同密度下转角后区域行人运动速度、单位流量均低于P&M平直通道模型;适当的激励作用有助于减轻行人拥堵,提高通行效率,当行人速度达到较高水平后效果不再显著。     

Fenton法处理垃圾渗滤液过程中有机物分子质量分布和荧光特性

采用Fenton氧化工艺对上海某垃圾填埋场垃圾渗滤液进行处理. 提取和分离了Fenton氧化前后腐殖酸组分(富里酸、胡敏酸),运用凝胶色谱法和三维荧光光谱技术对Fenton氧化前后各物质的分子质量分布和有机物荧光特性进行了研究. 结果表明:Fenton反应可使ρ(BOD₅)/ρ(COD_Cr)从0.011提高到0.285. 通过分子质量分布和三维荧光特性的测量可知,造成这种可生化性提高的原因是Fenton反应使垃圾渗滤液中有机物的分子质量降低,其中对高分子质量胡敏酸的去除以及对富里酸分子质量的降低起到了关键作用.