Changes in sea urchin populations after the destruction of kelp beds

In St. Margaret's Bay, Nova Scotia, Canada, there are large areas in which sea urchins (Strongylocentrotus droebachiensis) have eliminated beds of kelp (Laminaria spp.). Sites were identified where destruction of kelp beds had taken place 1, 2, 3, 3.5 and 4 years ago. With increase of time since kelp disappearance, the sea urchins showed decreased growth rate, reduced gonad size, but an increase in numbers resulting from high recruitment rates in the first two years after kelp bed destruction. These sea urchin populations, by their browsing, effectively prevent the regeneration of kelp. There is, as yet, no evidence of the sea urchin populations being starved out to allow the kelp to return.     

松花江中游(哨口-松花江村段)水中有毒有机物污染研究

1983—1990年,在松花江中游(哨口—松花江村)138公里江段中,进行七次五断面追踪水团采样,采用高分子微球GDX—502吸附富集,GC定性定量,GC/MS定性验证。依据有机物检出率、毒性持久性、有点源排放、分析方法适用等因素,筛选出65种主要有毒有机物。化合物总浓度逐年降低,石油烷烃、芳烃浓度增加;属致癌致变性化合物21种,EPA优测物21种,建议的优先控制黑名单20种;有点源排入的占90％以上,污染源来自吉化主要入江污水口;封冰期比其它水文期污染增强;该江段污染特征为氯代链烃、氯代苯类、硝基芳烃种类多、浓度高,应为重点控制对象。     

吐鲁番盆地水资源利用对策初探

就干旱缺水的吐鲁番盆地水资源利用问题提出了一些建议。     

On-board measurements of gaseous pollutant emission characteristics under real driving conditions from light-duty diesel vehicles in Chinese cities

A total of 15 light-duty diesel vehicles(LDDVs) were tested with the goal of understanding the emission factors of real-world vehicles by conducting on-board emission measurements. The emission characteristics of hydrocarbons(HC) and nitrogen oxides(NOx) at different speeds, chemical species profiles and ozone formation potential(OFP) of volatile organic compounds(VOCs) emitted from diesel vehicles with different emission standards were analyzed. The results demonstrated that emission reductions of HC and NOxhad been achieved as the control technology became more rigorous from Stage I to Stage IV. It was also found that the HC and NOxemissions and percentage of O2 dropped with the increase of speed, while the percentage of CO2 increased. The abundance of alkanes was significantly higher in diesel vehicle emissions, approximately accounting for 41.1%–45.2%, followed by aromatics and alkenes. The most abundant species were propene,ethane, n-decane, n-undecane, and n-dodecane. The maximum incremental reactivity(MIR)method was adopted to evaluate the contributions of individual VOCs to OFP. The results indicated that the largest contributors to O3 production were alkenes and aromatics, which accounted for 87.7%–91.5%. Propene, ethene, 1,2,4-trimethylbenzene, 1-butene, and1,2,3-trimethylbenzene were the top five VOC species based on their OFP, and accounted for 54.0%-64.8% of the total OFP. The threshold dilution factor was applied to analyze the possibility of VOC stench pollution. The majority of stench components emitted from vehicle exhaust were aromatics, especially p-diethylbenzene, propylbenzene, m-ethyltoluene, and p-ethyltoluene.     

Optimizing emission inventory for chemical transport models by using genetic algorithm

Air pollutant emission inventory is an important input parameter for chemical transport models (CTMs). Since great uncertainties exist in the emission inventory, further improvements and refinements are required. In this paper, genetic algorithm (GA), a global search and optimization method, was applied to optimize the emission inventory for the Models-3/Community Multiscale Air Quality (CMAQ) model. An emission optimizing system based on GA was developed and embedded to the CMAQ through the design of several core modules, which implemented the basic functions such as emission adjusting, GA population initializing, CMAQ results evaluating and GA operating. Hypothetical and real-data experiments were respectively performed to examine the validity of GA for emission calibrating. GA showed good performance in both experiments and was always able to find the global minimum. The emission optimizing system was then used to calibrate seasonal PM₁₀ emission inventories of Beijing. Results revealed that PM₁₀ emission in Beijing was underestimated in 2002, an average of 62.74% higher adjustment factor should be imposed on the original emission in target months of different seasons. With the calibrated emission inventories, CMAQ model errors were decreased by 6.46% on average in different seasons. It was concluded that GA was a promising search technique in calibrating emission inputs for CTMs.     

Potential of flavonoids as anti-Alzheimer’s agents: bench to bedside

Environmental Science and Pollution Research - Developing therapies for neurodegenerative diseases are challenging because of the presence of blood–brain barrier and Alzheimer being one of...     

华山地区PM2.5中无机离子垂直分布特征

2016年夏季在华山山腰及山脚设两个采样点（垂直高程相差约700 m）,运用大流量采样器进行每4 h 1次PM_2.5样品采集,对其无机离子进行分析,探讨其浓度、组成、垂直变化、日变化及酸度的特征.结果表明：采样期间,华山山腰及山脚的PM_2.5分别为：（46.9±38.2）μg·m^-3和（76.0±44.3）μg·m^-3,PM_2.5中无机离子分别为：（16.6±15.7）μg·m^-3和（24.0±15.0）μg·m^-3.两个点位无机离子浓度依次为：SO₄^2- > NO₃^- > NH₄⁺ > Ca²⁺.SO₄^2-、NO₃^-、NH₄⁺为主要组分,占华山山腰及山脚大气PM_2.5总离子质量浓度的89%和85%.线性回归分析显示：PM_2.5中的NH₄⁺在华山山腰主要以（NH₄）₂SO₄和NH₄NO₃的形式存在,而在华山山脚主要以NH₄HSO₄和NH₄NO₃的形式存在.华山山腰和山脚PM_2.5及其离子呈现出不同的日变化特征：山腰在12：00~16：00出现峰值,主要是因为边界层抬升和山谷风输送地表污染物的缘故;山脚则分别在白天08：00~12：00和夜晚00：00~04：00出现双峰值,这主要是由于早高峰交通排放增加和夜间大型载货卡车流量增大所致.利用阴阳离子当量平衡法及ISORROPIA Ⅱ模型进一步探讨了PM_2.5酸度特征,结果表明：华山山脚PM_2.5的酸度（pH=2.9±2.0）强于山腰（pH=3.2±2.3）.