Physiological aspects of vetiver grass for rehabilitation in abandoned metalliferous mine wastes

Physiological aspects of why vetiver grass (Vetiveria zizanioides L.) can be tolerant to heavy metals and be used as an alternative method for rehabilitation of abandoned metalliferous mine wastelands have been investigated. The results showed that high proportions of lead and zinc (Pb/Zn) tailing greatly inhibited the leaf growth, dry matter accumulation, and photosynthesis of leaves, but stimulated the accumulation of proline and abscisic acid (ABA), and enhanced the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), implying that different mechanisms to detoxify active oxygen species (AOS) existed in different parts of plants. Physiological responses to heavy metal treatments differed greatly between roots and shoots. Nitrogen fertilizer application could greatly alleviate the adverse effects of high proportions of Pb/Zn tailing on vetiver grass growth.     

接枝羧基淀粉对贵金属离子吸附性能研究

研究了接枝羧基淀粉（ＩＳＣ）对贵金属离子Ａｇ（Ⅰ）,Ｐｄ（Ⅱ）、Ｐｔ（Ⅳ）的静态吸附性能和选择性及介质的ＰＨ对其吸附性能的影响,利用接枝羧基淀粉与Ａｇ（Ⅰ）形成螯合物的红外光谱和Ｘ－射线光电子能谱数据（ＸＰＳ）探讨了其吸附作用机理。     

荧光染色法测定活性污泥中的活性生物量

活性污泥中活性微生物量是表征污染物去除能力的重要指标。探索了荧光染色法直接检测活性细菌的原理和测定方法,结果表明,大肠杆菌、唾液链球菌和铜绿假单胞杆菌的活菌细胞浓度与荧光光强的线性相关度都超过0.95;在惰性颗粒物浓度为20 mg/L到60 mg/L的范围内,其对荧光光强的影响可通过线性关系修正;搅拌速度为1 000 r/min且搅拌10 min时前处理效果最好。     

碳源投加方式对SBR工艺脱氮速率的影响

为了提高生物反应器的脱氮效率,研究采用SBR处理模拟生活污水,利用醋酸钠作为碳源,考察碳源投加方式对脱氮速率的影响。结果表明,当温度为10~15℃,进水COD为330~550 mg/L时,采用不同的碳源投加方式,COD去除率均高于95%。进水一次投加2.4 g碳源,COD平均反应速率为5.3 mg/(g·h),平均反硝化速率为0.28 mg/(g·h)。进水、反应器运行3 h时分别投加1.2 g碳源,COD平均反应速率为6.89 mg/(g·h),平均反硝化速率为0.37 mg/(g·h)。进水、反应6 h时分别投加1.2 g碳源,COD平均反应速率为6.50 mg/(g·h),平均反硝化速率为0.52 mg/(g·h)。进水投加1.2 g碳源、反应器运行3 h和6 h时分别投加0.6 g醋酸钠碳源,COD平均反应速率为6.2 mg/(g·h),平均反硝化速率为0.39 mg/(g·h)。分次投加碳源能够提高COD反应速率和TN去除率,同时保持较高的硝化反硝化速率。     

工业烟气净化系统的风量平衡调节及数值模拟应用研究

为了对某钢铁集团烧结机尾气净化系统的风量平衡进行调节,提出了利用Fluent仿真软件对通风管道内部流场进行数值模拟,在主管和部分支管上设置节流管、调节管径的改进措施。风量模拟结果表明,通风管道的原风量存在严重的不平衡性,吸尘点的风量不平衡率高达75.0%,在部分管道增加节流管可以有效调整管道的风量不平衡性,调整后吸尘点风量的不平衡率为18.8%;对于压力损失较大、风量偏小的管道,可通过管径调节使其风量基本达到设计要求;Fluent仿真软件的风量模拟值与现场实测值有较高的吻合性,数值模拟方法可以为工业烟气净化系统的改造提供参考依据。不仅能够为前期工程设计提供帮助,大大节省工程调试费用,缩短工期,并有助于风量不平衡管道的调节和改造。     

臭氧氧化处理养猪场厌氧沼液

实验在MAP沉淀处理的基础上,采用臭氧氧化技术对养猪场厌氧沼液进行处理。研究了氧化过程中臭氧的投加量、反应时间对沼液pH、COD和UV254的去除效果、沼液可生化性、氮形态转化的影响。结果表明,在臭氧氧化过程中,随着反应时间的延长,沼液pH呈逐渐下降的趋势。在臭氧投加量为6 mg/L、反应时间为40 min时,COD和UV254去除率达到最大,分别为21.7%和60%。此外,臭氧氧化能把BOD5/COD的比值从0.24提高为0.41,有效提高了沼液的可生化性。在臭氧投加量为6 mg/L、反应时间为2 h时,TN的浓度基本维持在370~410 mg/L之间,氨氮浓度随时间呈现先升高后降低的变化趋势,且最终维持在132.7 mg/L,然而,硝态氮浓度反而升高了近一倍,由此可见,臭氧氧化不能完全脱氮,只能使氮从一种形态转化为另一种形态。     

Algae community and trophic state of subtropical reservoirs in southeast Fujian, China

Background,

aim, and scope Fujian reservoirs in southeast China are important water resources for economic and social sustainable development, although few have been studied previously. In recent years, growing population and increasing demands for water shifted the focus of many reservoirs from flood control and irrigation water to drinking water. However, most of them showed a rapid increase in the level of eutrophication, which is one of the most serious and challenging environmental problems. In this study, we investigated the algae community characteristics, trophic state, and eutrophication control strategies for typical subtropical reservoirs in southeast Fujian.

Materials and methods

Surface water samples were collected using polyvinyl chloride (PVC) plastic bottles from 11 Fujian reservoirs in summer 2010. Planktonic algae were investigated by optical microscopy. Water properties were determined according to the national standard methods.

Results and discussion

Shallow reservoirs generally have higher values of trophic state index (TSI) and appear to be more susceptible to anthropogenic disturbance than deeper reservoirs. A total of 129 taxa belonging to eight phyla (i.e., Bacillariophyta, Chlorophyta, Chrysophyta, Cryptophyta, Cyanophyta, Euglenophyta, Pyrrophyta, Xanthophyta) were observed and the most diverse groups were Chlorophyta (52 taxa), Cyanophyta (20 taxa), Euglenophyta (17 taxa), Chrysophyta (14 taxa). The dominant groups were Chlorophyta (40.58%), Cyanophyta (22.91%), Bacillariophyta (21.61%), Chrysophyta (6.91%). The species richness, abundance, diversity, and evenness of algae varied significantly between reservoirs. TSI results indicated that all 11 reservoirs were eutrophic, three of them were hypereutrophic, six were middle eutrophic, and two were light eutrophic. There was a strong positive correlation between algal diversity and TSI at P?4-N, NO _x -N, TP, and chlorophyll a were significant environmental variables affecting the distribution of algae communities. The transparency and chlorophyll a were the strongest environmental factors in explaining the community data. Furthermore, the degradation of water quality associated with excess levels of nitrogen and phosphorus in Fujian reservoirs may be impacted by interactions among agriculture and urban factors. A watershed-based management strategy, especially phosphorus control, should be developed for drinking water source protection and sustainable reservoirs in the future.

Conclusion and recommendations

All investigated reservoirs were eutrophicated based on the comprehensive TSI values; thus, our results provided an early warning of water degradation in Fujian reservoirs. Furthermore, the trophic state plays an important role in shaping community structure and in determining species diversity of algae. Therefore, long-term and regular monitoring of Euglenophyta, Cyanophyta, TN, TP and chlorophyll a in reservoirs is urgently needed to further understand the future trend of eutrophication and to develop a watershed-based strategy to manage the Cyanophyta bloom hazards.     

Characterization of real-world activity, fuel use, and emissions for selected motor graders fueled with petroleum diesel and B20 biodiesel

Motor graders are a common type of nonroad vehicle used in many road construction and maintenance applications. In-use activity, fuel use, and emissions were measured for six selected motor graders using a portable emission measurement system. Each motor grader was tested with petroleum diesel and B20 biodiesel. Duty cycles were quantified in terms of the empirical cumulative distribution function of manifold absolute pressure (MAP), which is an indicator of engine load. The motor graders were operated under normal duty cycles for road maintenance and repair at various locations in Wake and Nash Counties in North Carolina. Approximately 3 hr of quality-assured, second-by-second data were obtained during each test. An empirical modal-based model of vehicle fuel use and emissions was developed, based on stratifying the data with respect to ranges of normalized MAP, to enable comparisons between duty cycles, motor graders, and fuels. Time-based emission factors were found to increase monotonically with MAP. Fuel-based emission factors were mainly sensitive to differences between idle and non-idle engine operation. Cycle average emission factors were estimated for road "resurfacing," "roading," and "shouldering" activities. On average, the use of B20 instead of petroleum diesel leads to a negligible decrease of 1.6% in nitric oxide emission rate, and decreases of 19-22% in emission rates of carbon monoxide, hydrocarbons, and particulate matter. Emission rates decrease significantly when comparing newer engine tier vehicles to older ones. Significant reductions in tailpipe emissions accrue especially from the use of B20 and adoption of newer vehicles.     

土壤水溶态铜对小白菜的毒害效应及其预测模型

土壤中铜(Cu)重金属的生物毒性/有效性主要取决于它们在土壤液相中含量和土壤溶液的性质。探寻土壤有效态Cu的生物毒害效应,表征量化其与土壤溶液性质关系,可为土壤Cu的环境风险评价提供参考。选取17种典型农田土壤,探讨了有效态Cu(土壤孔隙水以及CaCl_2浸提态)对小白菜生长的毒性效应及其预测模型。结果表明:土壤孔隙水中Cu对小白菜生长10%抑制的毒性阈值值(EC_(10))和50%抑制的毒性阈值(EC_(50)),最大值与最小值相差为14.7和14.6倍;同样,对于CaCl_2提取态Cu的EC_(10)和EC_(50),最大值与最小值相差12.7和7.7倍,表明土壤溶液性质对水溶性Cu对小白菜的毒性阈值影响很大。建立了土壤溶液的重要因子(溶解性有机碳、土壤溶液pH值、电导率、全硫含量、Ca~(2+)、Mg~(2+)、K~+、Na~+)和水溶性Cu阈值之间的多元回归关系,结果显示,土壤溶液性质可以较好地预测水溶性Cu对小白菜的毒性阈值。同时,土壤溶液中Mg~(2+)、K~+和S的含量是控制孔隙水中Cu对小白菜生长毒性的最重要因子,单一的S能分别解释34%的EC_(10)变异,K~+解释26%的EC_(50)变化。本研究结果可为陆地环境中水溶性Cu的风险评价提供基础。     

Theoretical study on the formation mechanism of polychlorinated dibenzothiophenes/thianthrenes from 2-chlorothiophenol molecules

Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes(PCDT/TAs),sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans(PCDD/Fs), has been well-documented to occur via radical–radical coupling reactions from chlorinated thiophenol precursors. However, the current understanding of the formation mechanism of PCDT/TAs is exclusively limited to the inherent point of view that chlorothiophenoxy radicals act as the only required intermediates for PCDT/TAs. This study investigates reaction pathways for the formation of PCDT/TAs involving two new types of radical species, i.e., substituted phenyl radicals and substituted thiophenoxyl diradicals. Taking 2-chlorothiophenol(2-CTP) as a model compound for chlorothiophenols,we found that apart from the mostly discussed chlorothiophenoxy radicals, substituted phenyl radicals and substituted thiophenoxyl diradicals could also be readily formed via the reaction of 2-CTP with H radicals. Furthermore, direct self-and cross-coupling of these radicals can result in the formation of PCDT/TAs, including 1-monochlorothianthrene(1-MCTA), 1,6-dichlorothianthrene(1,6-DCTA), 4,6-dichlorodibenzothiophene(4,6-DCDT)and 1,6-dichlorodibenzothiophene(1,6-DCDT). The pathways proposed in this work are proven to be both thermodynamically and kinetically favorable. Particularly, comparisons were made between the formation mechanisms of sulfurated and oxygenated dioxin systems from an energetic point view, showing that replacing oxygen with sulfur atoms greatly reduces the activation barriers of the rate-controlling steps involved in the PCDT/TA formation processes compared with those involved for PCDD/Fs. The calculated results in this work may improve our understanding of the formation mechanism of PCDT/TAs from chlorothiophenol precursors and should be informative to environmental scientists.