Effects of long-term nitrogen addition and precipitation changes on CH4 flux in an alpine steppe北大核心CSCD

土壤是甲烷(CH4)重要的源和汇.氮沉降和降水格局变化正在急剧改变土壤碳循环,进而可能对土壤CH4通量造成深刻影响.高寒生态系统是巨大的碳库,对氮沉降和降水变化十分敏感.然而,目前多数研究集中在短期实验上,缺乏对长期氮沉降和降水变化背景下CH4通量的响应及其调控因素的认识.以青藏高原高寒草原为研究对象,在2013年搭建模拟氮沉降和降水格局改变实验平台.基于静态箱–气相色谱法测定2020年生长季(5-10月)土壤CH4通量.结果显示,高寒草原土壤呈CH4的汇.氮添加没有显著改变生长季和植物生长高峰CH4通量.然而,降水变化显著改变了生长季和植物生长高峰CH4通量,其中降水增加(+50%降水)降低了CH4的吸收(分别为–16%和–45%),降水减少(–50%降水)增强了CH4的吸收(分别为+73%和+33%).进一步研究发现,与植物属性和功能基因丰度相比,土壤环境因子主导了CH4通量变化(解释率>90%).其中CH4通量与土壤含水量和温度显著正相关,与土壤pH显著负相关.综上所述,在未来全球变化情景下,降水格局改变更能调节青藏高原高寒草原CH4通量的变化.(图6表1参37)     

Empirical likelihood confidence intervals for adaptive cluster sampling

Adaptive cluster sampling (ACS) is an efficient sampling design for estimating parameters of rare and clustered populations. It is widely used in ecological research. The modified Hansen-Hurwitz (HH) and Horvitz-Thompson (HT) estimators based on small samples under ACS have often highly skewed distributions. In such situations, confidence intervals based on traditional normal approximation can lead to unsatisfactory results, with poor coverage properties. Christman and Pontius (Biometrics 56:503–510, 2000) showed that bootstrap percentile methods are appropriate for constructing confidence intervals from the HH estimator. But Perez and Pontius (J Stat Comput Simul 76:755–764, 2006) showed that bootstrap confidence intervals from the HT estimator are even worse than the normal approximation confidence intervals. In this article, we consider two pseudo empirical likelihood functions under the ACS design. One leads to the HH estimator and the other leads to a HT type estimator known as the Hájek estimator. Based on these two empirical likelihood functions, we derive confidence intervals for the population mean. Using a simulation study, we show that the confidence intervals obtained from the first EL function perform as good as the bootstrap confidence intervals from the HH estimator but the confidence intervals obtained from the second EL function perform much better than the bootstrap confidence intervals from the HT estimator, in terms of coverage rate.     

Assessment of urban air pollution and it's probable health impact

The present study deals with the quantitative effect of vehicular emission on ambient air quality during May 2006 in urban area of Lucknow city. In this study SPM, RSPM, SO2, NOx and 7 trace metals associated with RSPM were estimated at 10 representative locations in urban area and one village area for control. Beside this, air quality index (AQI), health effects of different metals and mortality were assessed. The 24 hr average concentration of SPM, RSPM, SO2 and NOx was found to be 382.3, 171.5, 24.3 and 33.8 microg m(-3) respectively in urban area and these concentrations were found to be significantly (p < 0.01) higher by 94.8, 134.8, 107.4 and 129.6% than control site respectively The 24 hr mean of SPM and RSPM at each location of urban area were found to be higher than prescribed limit of National Ambient Air Quality Standard (NAAQS) except SPM for industrial area. The 24 hr mean concentration of metals associated with RSPM was found to be higher than the control site by 52.3, 271.8, 408.9, 75.81, 62.7, 487.54 and 189.5% for Fe, Cu, Pb, Zn, Ni, Mn and Cr respectively. The inter correlation of metals Pb with Mn, Fe and Cr; Zn with Ni and Cr; Ni with Cr; Mn with Fe and Cu with Cr showed significant positive relation either at p < 0.05 or p < 0.01 level. Metals Pb, Mn and Cr (p < 0.01) and Cu (p < 0.05) showed significant positive correlation with RSPM. These results indicate that ambient air quality in the urban area is affected adversely due to emission and accumulation of SPM, RSPM, SO2, NOx and trace metals. These pollutants may pose detrimental effect on human health, as exposure of these are associated with cardiovascular and respiratory diseases, neurological impairments, increased risk of preterm birth and even mortality and morbidity.     

中美垃圾场渗滤液中的金属成分变化的调研

主要对2000～2004年美国佛罗里达州中部的5个垃圾场中垃圾渗滤液的金属离子成分进行统计分析,从中发现锑(Sb)、砷(As)、铬(Cr)、铁(Fe)、镍(Ni)、钠(Na)、钒(V)、硒(Se)等8种金属在渗滤液中的质量浓度超过EPA地表及饮用水标准,其中比较严重的是As,Fe和Na,每年都超EPA标准.推测该地区地表或地下水体被As,Fe,Na污染的可能性很大.对其他还未列入监控标准的金属也做了来源及危害分析.同时与国内某垃圾场渗滤液中的金属成份进行了比较,结果显示该垃圾场渗滤液只有汞(Hg)超国家V类水体标准,但还在美国EPA容许范围内.     

Catastrophe and the life span of coral reefs

A strong earthquake in the western Caribbean in 2009 had a catastrophic impact on uncemented, unconsolidated coral reefs in the central sector of the shelf lagoon of the Belizean barrier reef. In a set of 21 reef sites that had been observed prior to the earthquake, the benthic assemblages of 10 were eradicated, and one was partially damaged, by avalanching of their slopes. Ecological dynamics that had played out over the previous 23 years, including the mass mortalities of two sequentially dominant coral species and a large increase in the cover of an encrusting sponge, were instantaneously rendered moot in the areas of catastrophic reef-slope failure. Because these prior dynamics also determined the benthic composition and resilience of adjacent sections of reef that remained intact, the history of disturbance prior to the earthquake will strongly influence decadal-scale recovery in the failed areas. Geological analysis of the reef framework yielded a minimum return time of 2000-4000 years for this type of high-amplitude event. Anthropogenic degradation of ecosystems must be viewed against the backdrop of long-period, natural catastrophes, such as the impact of strong earthquakes on uncemented, lagoonal reefs.     

New aspect in seagrass acclimation: leaf mechanical properties vary spatially and seasonally in the temperate species Cymodocea nodosa Ucria (Ascherson)

Seagrasses may acclimate to environmental heterogeneity through phenotypic plasticity. In contrast to leaf morphology, which has been a central point in seagrass acclimation studies, plasticity in leaf biomechanics and fibre content is poorly understood, despite being crucial in plant ecological performance, especially regarding physical forces. We hypothesised that mechanical traits (e.g. breaking force, strength, toughness, and stiffness) and fibre content of seagrass leaves vary as morphology does under differential environments. Cymodocea nodosa was seasonally monitored at three locations around Cádiz Bay (southern Spain) with hydrodynamic regime as the most noticeable difference between them. Leaves showed plasticity in both morphology and mechanical traits, with wave-exposed individuals presenting short but extensible and tough leaves. Leaf fibre content was invariant along the year and with little spatial variability. Cross-sectional area rather than material properties or fibre content differentiates leaf mechanical resistance. Seagrass capacity to thrive under a range of mechanical forces may be dictated by their plasticity in morpho-biomechanical traits, a key element for the hydrodynamical performance and, hence, for species colonisation and distribution.     

The solid-phase controls on the mobility of heavy metals at the Copper Cliff tailings area, Sudbury, Ontario, Canada

The Copper Cliff Tailings Disposal Area, located near Sudbury, Ontario, covers an area of approximately 2200 ha and constitutes more than 10% of the total area of all mine tailings in Canada. The area has been utilized since 1936, receiving sulphide-containing tailings from the Inco Sudbury operations. Field measurements of pore-gas oxygen and carbon dioxide in the vadose zone indicate that sulphide oxidation has progressed to depths of 1.6 m to 1.7 m within the tailings. The oxidation of sulphide minerals within the vadose zone, and the accompanying dissolution of carbonate and aluminosilicate minerals within these tailings releases SO₄, Fe(II) and other metals to the pore water. In the vadose and saturated zones, concentrations of Fe and Ni exceed 10100 mg/l and 2210 mg/l, respectively. These high concentrations of dissolved metals are attenuated by a series of precipitation, coprecipitation and adsorption reactions. The precipitation of secondary sulphate and hydroxide phases also create hardpan layers at or near the oxidation front. Geochemical modelling of the pore-water chemistry suggests that pH-buffering reactions are occurring within the shallow oxidized zones, and that secondary-phase precipitation is occurring at or near the underlying hardpan and transition zones. Mineralogical study of the tailings confirmed the presence of jarosite, gypsum and goethite within the shallow tailings, suggesting that these phases are controlling the dissolved concentrations of Fe, SO₄ and Ca. Extraction experiments conducted on the tailings solids indicate that the constituents contained in the water-soluble fraction of the shallow, weathered tailings are derived from the original pore water and the dissolution of highly soluble phases such as gypsum. The acid-leachable fraction of the weathered tailings accounts for up to 25% of the heavy metals, and the reducible fraction may contain up to 100% of the heavy metals within the shallow, weathered tailings. Based on the pore water profiles and the geochemistry of the tailings solids, a relative mobility scale of Fe=Mn=Ni=Co>Cd Zn>Cr=Pb>Cu can be determined.     

Occurrence of perfluorinated organic acids in the North and Baltic seas. Part 1: distribution in sea water

Purpose  

Due to their high water solubilities and mobilities, persistent, polar perfluorinated compounds (PFCs) such as perfluorinated carboxylates and sulfonates are likely to end up in the oceans. In part 1 of this study, their distribution in North and Baltic Sea water is reported, being of special interest because these seas are surrounded by highly industrialized countries with high population densities.