Assessment of persistent organochlorine pollutants in sediments from Lake Manzala, Egypt

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in surface and core sediment samples collected from Manzala Lake, the largest of the Egyptian coastal lakes. Total concentrations of OCPs and ∑7 PCBs (ICES) in sediments ranged from 0.63 to 31.31 ng/g and 0.26 to 31.27 ng/g, respectively. Geographical distribution indicates that levels of contaminants were significantly higher in areas which are mainly influenced by municipal discharge, indicating significant sources of these compounds in urbanised areas. The composition of DDT and its metabolites suggest old input of DDT. The levels of contaminants in Manzala Lake were similar or lower than those observed in comparable areas worldwide. The profiles of ∑OCPs and ∑PCBs in a core from a site heavily impacted by sewage discharge have highest concentrations in the surface core section indicating recent inputs. Assessment of ecotoxicological risk indicated that sediments in two sites were likely to pose potential biological adverse impact.     

A nested-cell approach for in situ remediation

We characterize the hydraulics of an extraction-injection well pair in arbitrarily oriented regional flow by the recirculation ratio, area, and average residence time in the recirculation zone. Erratic regional flow conditions may compromise the performance of the reactor between a single well pair. We propose an alternative four-well system: two downgradient extraction and two upgradient injection wells creating an inner cell nested within an outer cell. The outer cell protects the inner cell from the influence of regional flow. Compared to a two-well system, the proposed four-well system has several advantages: (1) the recirculation ratio within the nested inner cell is less sensitive to the regional flow direction; (2) a transitional recirculation zone between the inner and outer cells can capture flow leakage from the inner cell, minimizing the release of untreated contaminants; and (3) the size of the recirculation zone and residence times can be better controlled within the inner cell by changing the pumping rates. The system is applied at the Field Research Center in Oak Ridge, Tennessee, where experiments on microbial in situ reduction of uranium (VI) are under way.     

长江中游泥炭湿地有壳变形虫空间分布及其对水化学因子的响应

长江中游高山泥炭湿地在区域生态安全和生物多样性保护方面具有举足重要的地位,有壳变形虫是一类在泥炭湿地表面大量生活的原生动物,它们对环境变化敏感,是环境变化的有效指示器.泥炭湿地的现代生态学调查已经表明,有壳变形虫群落对泥炭的表面湿度和水文条件具有灵敏的响应,但是与其他环境条件如水化学因子的关系尚不明确.本文主要调查了长江中游高山泥炭湿地有壳变形虫群落特征及其对水化学因子的响应,发现Cr和Mn对有壳变形虫的群落组成具有较为明显的影响.有壳变形虫的群落组成在不同湿地间有一定差异,这种空间上的差异分布可能反映了湿地的不同类型、发育阶段和人类活动等信息.有壳变形虫可为湿地的科学管理、动态监测和可持续发展等方面提供有效的指示信息.     

四川剑门关侏罗—白垩系红层分子化石的古环境和古气候意义

利用气相色谱－质谱仪从四川剑门关侏罗－白垩系红层中检测出包括正构烷烃、类异戊二烯烃、长链三环萜、霍烷及甾烷等系列分子化石。分析了这些分子化石的分布特征及其来源，利用分子化石的多项参数（如w(C21^-)/w(C22^ ),w(Pr)/w(Ph),w(Pr)/w(nC17),w(Ph)/w(nC18)，伽马蜡烷指数、甾烷等）对沉积环境的盐度、氧化－还原条件、陆相标志等方面作了探讨。这些分子化石参数证实中侏罗世－早白垩世，剑门关－带的沉积环境应为低盐度淡水、弱氧化的陆相沉积环境，所研究的陆相样品高碳数正构烷烃均以本植物有关的C27，C29为主峰，未出现草本植物的C21主峰，反映了研究区总体格局是一种以木本植物占绝对优势、温暖湿润的气候环境，与红盆发育的气候条件吻合，充分体现了分子化石在恢复古环境、古植被和古气候方面有极大潜力。     

Fe^2＋浓度对Acidithiobacillus ferrooxidans耐铜性的影响

嗜酸性氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans）是铜矿生物冶金中应用最广泛的微生物之一。但在冶金过程中淋滤出来的Cu2＋等重金属逐渐积累,达到一定的浓度后就会抑制A.ferrooxidans的生长,从而降低冶金的效率。本文着重研究了Fe2＋初始浓度对A.ferrooxidans耐铜性的影响。实验中ρ（Cu2＋）变化范围为0～5.0 g/L。结果表明,当ρ0（Fe2＋）为6.7 g/L时,A.ferrooxidans仅在Cu2＋为0～0.4 g/L的体系中能显著地氧化Fe2＋进行生长;当Cu2＋≥0.5 g/L时,A.ferrooxidans生长完全受到抑制。将ρ0（Fe2＋）增加到8.9 g/L,A.ferroox-idans在0.5、1.0、2.0和3.0 g/L Cu2＋的培养基中也能明显氧化Fe2＋,并最终将其完全氧化,Cu2＋对A.ferrooxidans生长抑制作用仅出现在4.0和5.0 g/L Cu2＋的体系中。因此提高体系中亚铁离子的浓度能提高菌体对Cu2＋的耐受力。研究结果对铜矿的生物冶金具有重要意义。     

Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam

Effects of elevated seawater temperature show high spatial heterogeneity and variation within and among coral species. The objective of this study was to investigate how two coral species, Porites lutea and Galaxea fascicularis, from two high latitude reefs differently exposed to chronic disturbance, respond to elevated seawater temperatures. Corals were collected from reefs nearshore (i.e. subjected to high sediment load, higher chlorophyll α concentrations, turbidity etc.) and offshore (i.e. less exposed). The corals were exposed in the lab to gradually increasing temperatures (25.5-33.5?°C) for 72?h after which they were allowed to recover to ambient temperature (25.5?°C) for 24?h. Production and respiration were measured after 24, 48, 72 and 96?h. The results show that P. lutea from nearshore reefs suffered an initial decrease in gross primary production/respiration (GP/R) ratio after 24?h, after only a moderate temperature increase (+2?°C, from 25.5 to 27.5?°C), while there was no difference in GP/R ratio between heat-exposed and controls the other days, indicating that the chronic disturbance in the nearshore reef had no effect on their thermotolerance. Furthermore, P. lutea from the offshore reef showed a decrease in GP/R ratio both after 24?h and 72?h (33.5?°C) of exposure. In comparison, G. fascicularis showed a decrease in GP/R ratio after 48?h, 72?h and 96?h of exposure for the nearshore corals. Also, after 72?h these corals had withdrawn their polyps. There were no differences between heat-treated and controls for the offshore G. fascicularis. This implies that the chronically disturbed G. fascicularis had lower thermotolerance when exposed to a temperature increase. This study, hence, shows that the response of corals to elevated seawater temperature varies with species and environmental background history.     

Using GIS and perceived distance to understand the unequal geographies of healthcare in lower-income urban neighbourhoods

Geographers play important roles in public health research, particularly in understanding healthcare accessibility, utilisation, and individual healthcare experiences. Most accessibility studies have benefited from the increased sophistication of geographic information systems (GIS). Some studies have been enhanced with semi-structured in-depth interviews to understand individual experiences of people as they access healthcare. However, few accessibility studies have explicitly utilised individual in-depth interview data in the construction of new GIS accessibility measures. Using mixed methods including GIS analysis and individual data from semi-structured in-depth interviews, we offer satisfaction-adjusted distance as a new way of conceptualising accessibility in GIS. Based on fieldwork in a predominantly lower-income community in Columbus, Ohio (USA), we find many residents felt neighbourhood healthcare facilities offered low-quality care, which suggested an added perceived distance as they attempt to access high-quality healthcare facilities. The satisfaction-adjusted distance measure accounts for the perceived distance some residents feel as they search for high-quality healthcare in lower-income urban neighbourhoods. In moving beyond conventional GIS and re-conceptualising accessibility in this way, we offer a more realistic portrayal of the issues lower-income urban residents face as they attempt to access high-quality healthcare facilities. The work has theoretical implications for conceptualising healthcare accessibility, advances the mixed-methodologies literature, and argues for a more equitable distribution of high-quality healthcare in urban neighbourhoods.     

湖北清江和尚洞滴水微生物群落随空间和季节的变化

为了考察现代微生物群落对环境因子的响应关系及其在古气候重建中的应用潜力, 利用微生物学传统的培养计数、荧光染色总菌计数和BIOLOG的ECO微平板等技术对湖北省清江和尚洞内不同地点的滴水由内至外进行了空间和季节性的动态监测, 4个滴水点由内向外编号依次为1D、3D、4D和5D.结果证实湖北清江和尚洞洞穴滴水中存在一定数量的微生物.不同样点微生物的代谢活性不同, 1D样品中的微生物群落代谢活性最高, 3D表现出与1D相似的代谢特征, 但平均颜色变化率(AWCD: 微生物对碳源的利用程度, 颜色变化率越高, 表明微生物代谢越旺盛)较1D小, 4D和5D样品在接种24h后平均颜色变化率(AWCD)基本保持不变.对微生物代谢较为旺盛的1D、3D两个样品中不同时间内微生物群落的多样性指数进行分析, 表明洞穴滴水中微生物多样性相对稳定, 随采样季节的变化不大.相对于3D、1D的4个不同季节(采样时间)微生物群落对碳源种类的利用上存在一定差异.1D水样在2006秋季(2006年11月份)、2007春季(2007年5月)和2009年夏季(2009年7月份)微生物群落利用碳源种类上比较接近, 而在2008年初秋(2008年9月)碳源利用种类与前三者的差异明显.与1D相比, 3D的4个不同采样时间的滴水微生物群落在主成分1和主成分2的得分系数比较接近, 群落碳源代谢功能多样性差别不大.这种变化可能反映了不同季节滴水中可溶有机质成分(DOC)的变化及微生物群落成分的变化, 暗示了微生物群落结构变化在指示气候变化应用中的巨大潜力.但微生物群落多样性与代谢功能多样性与气候因子之间的关系尚需深入研究.