Distribution of heavy metals in sediments of the Pearl River Estuary, Southern China: Implications for sources and historical changes

The distribution of heavy metals (Pb, Zn, Cd and As) in sediments of the Pearl River Estuary was investigated. The spatial distribution of heavy metals displayed a decreasing pattern from the turbidity maxima to both upstream and downstream of the estuary, which suggested that suspended sediments played an important role in the trace metal distribution in the Pearl River Estuary. In addition, metal concentrations were higher in the west part of the estuary which received most of the pollutants from the Pearl River. In the sediment cores, fluxes of heavy metals were consistent with a predominant anthropogenic input in the period 1970-1990. From the mid-1990s to the 2000s, there was a significant decline in heavy metal pollution. The observed decline has shown the result of pollution control in the Pearl River Delta. However, it is noteworthy that the metal concentrations in the most recent sediment still remained considerably high. Taken together, the enrichment of heavy metals in sediments was largely controlled by anthropogenic pollution.     

Extinction rate of discovered and undiscovered plants in Singapore

Extinction is a key issue in the assessment of global biodiversity. However, many extinction rate measures do not account for species that went extinct before they could be discovered. The highly developed island city–state of Singapore has one of the best-documented tropical floras in the world. This allowed us to estimate the total rate of floristic extinctions in Singapore since 1822 after accounting for sampling effort and crypto extinctions by collating herbaria records. Our database comprised 34,224 specimens from 2076 native species, of which 464 species (22%) were considered nationally extinct. We assumed that undiscovered species had the same annual per-species extinction rates as discovered species and that no undiscovered species remained extant. With classical and Bayesian algorithms, we estimated that 304 (95% confidence interval, 213–414) and 412 (95% credible interval, 313–534) additional species went extinct before they could be discovered, respectively; corresponding total extinction rate estimates were 32% and 35% (range 30–38%). We detected violations of our 2 assumptions that could cause our extinction estimates, particularly the absolute numbers, to be biased downward. Thus, our estimates should be treated as lower bounds. Our results illustrate the possible magnitudes of plant extirpations that can be expected in the tropics as development continues.     

A method to estimate pre-exploitation population size

Antarctic fur seals (Arctocephalus gazella) were commercially exploited on the subantarctic island of South Georgia for over 100 years and nearly driven to extinction. Since the cessation of harvesting, however, their populations have rebounded, and they are now often considered a nuisance species whose impact on the terrestrial landscape should be mitigated. Any evaluation of their current population requires the context provided by their historic, pre-exploitation abundance, lest ecologists fall prey to shifting baseline syndrome in which their perspective on current abundance is compared only with an altered state resulting from past anthropogenic disturbance. Estimating pre-exploitation abundance is critical to defining species recovery and setting recovery targets, both of which are needed for the International Union for the Conservation of Nature's recent efforts to develop a green list of recovering species. To address this issue, we reconstructed the South Georgia fur seal harvest from 1786 to 1908 from ship logbooks and other historical records and interpolated missing harvest data as necessary with a generalized linear model fit to the historical record. Using an approximate Bayesian computation framework, harvest data, and a stochastic age-structured population model, we estimated the pre-exploitation abundance of Antarctic fur seals on South Georgia was 2.5 million females (95% CI 1.5–3.5 million). This estimate is similar to recent abundance estimates, and suggests current populations, and the ecological consequences of so many fur seals on the island, may be similar to conditions prior to human harvest. Although the historic archive on the fur sealing era is unavoidably patchy, the use of archival records is essential for reconstructing the past and, correspondingly, to understanding the present. Article impact statement: Defining species recovery requires an understanding of baseline population state, which can be estimated through statistical methods.     

区域历史地理研究与国土规划

人口与资源和环境之间的相互关系是一个历史过程。从发生学观点研究特写区域这种关系及其变化规律是区域历史地理研究的核心内容，探索历史上人口与资源和环境之间相互关系的规律及其演化机制，可为区域国土规划与整治中人口、资源与环境发展提供必要的历史借鉴和客观依据。同时，国土规划与整治的现实任务亦为区域历史地理研究提供了发展机遇。     

上海典型燃烧源铅和汞大气排放趋势分析

上海百年来快速的城市化进程导致资源能源的大量消耗,并向城市环境中排放了大量有毒有害污染物.为探寻上海典型燃烧源重金属大气排放历史及趋势,基于上海化石燃料(煤炭和汽油)的历史消耗量及其大气铅(Pb)和汞(Hg)的排放因子,估算了上海主要燃煤部门(燃煤电厂、工业部门和居民生活)和机动车燃油大气Pb和Hg的历史排放量.结果表明,1949~2015年间大气Pb和Hg的燃煤排放量随时间推进均呈现先增长后下降趋势,即1949年解放后快速增长的煤炭消耗和较少的烟尘控制措施使其排放量出现急剧地波动式增长,至20世纪80~90年达到高峰,此后上海采取了各种减排和控制措施,使得目前三大燃煤源的大气Pb和Hg排放量出现大幅度下降.1980~2015年间上海大气Hg的燃煤排放比例一直占据主导地位(87.5%~99.7%).含铅汽油自1997年完全退出上海市场之后,燃煤排放替代其成为大气Pb的主要贡献源(78.2%~83.5%),然而自2005年起随着汽油消耗的急速增长,汽油燃烧排放又成为其主要贡献源(55.5%~79.1%).     

事故致因理论对自主系统开发与安全运行的启示

在现代工业中,自主智能系统处在创新与探索阶段。由于先验知识的缺乏,其自身所带来的风险问题,越发得到学术界与工业界的关注。本文对于如何应用国际主流的事故致因理论以提高自主系统开发与运营的安全性进行了探讨。指出,现有的事故致因理论可用来从不同角度识别已知风险源,提高对未知风险源的警惕性,并通过描述事故场景,来辅助设计技术安全屏障与运行策略提高自主系统的安全性。为更好的理解自主系统如何会做出错误或不恰当决策,需对现有事故致因理论未涉及到的脑科学与认知心理学进一步的探讨与研究。     

Loss of Large Predatory Sharks from the Mediterranean Sea

Abstract:  Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead ( Sphyrna spp.), blue ( Prionace glauca ), mackerel ( Isurus oxyrinchus and Lamna nasus ), and thresher sharks ( Alopias vulpinus ) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.     

Historical perspectives on contemporary human–environment dynamics in southeast Africa

The human communities and ecosystems of island and coastal southeast Africa face significant and linked ecological threats. Socioecological conditions of concern to communities, governments, nongovernmental organizations, and researchers include declining agricultural productivity, deforestation, introductions of non-native flora and fauna, coastal erosion and sedimentation, damage to marine environments, illegal fishing, overfishing, waste pollution, salinization of freshwater supplies, and rising energy demands, among others. Human–environment challenges are connected to longer, often ignored, histories of social and ecological dynamics in the region. We argue that these challenges are more effectively understood and addressed within a longer-term historical ecology framework. We reviewed cases from Madagascar, coastal Kenya, and the Zanzibar Archipelago of fisheries, deforestation, and management of human waste to encourage increased engagement among historical ecologists, conservation scientists, and policy makers. These case studies demonstrate that by widening the types and time depths of data sets we used to investigate and address current socioecological challenges, our interpretations of their causes and strategies for their mitigation varied significantly.     

Explaining implementation deficits through multi-level governance in the EU's new member states: EU limits for arsenic in drinking water in Hungary

This paper uses a multi-level governance lens to explore a case of non-compliance with EU legislation in Hungary and expands historical institutionalist explanations of EU laggards. Despite adopting the European Union's (EU's) limit of 10 ppb arsenic in drinking water, parts of Hungary do not comply. To explain this deficit, the paper examines the match between discourse incorporated into policy and held by policy actors in Hungary. Multiple points of mismatch are found that influence implementation because of governance structures, adding specificity to explanations of ‘goodness of fit’ between EU and national policy.     

中国城市饮用水法的历史发展及其启示

近年来中国城市饮用水事件频发,威胁着城市饮用水安全,直接关系着公民的生命权和健康权.然而,中国有关城市饮用水的规定散见于相关法律、行政法规及环境、水利、卫生、建设等部门制定的规章中,还没有一部完整意义上的城市饮用水法.城市饮用水法历经四个历史阶段的发展,仍然只关注于城市饮用水某个阶段的发展.因此,城市饮用水法应加强城市饮用水各个阶段的管理,建立城市饮用水全过程控制法律制度.