Conceptual Framework of Tourism Carrying Capacity for a Tourism City： Experiences from National Parks in the United States

There is no universally-accepted definition of tourism carrying capacity(TCC).Numerical TCC focuses on use level and is considered as"a magic number"of the saturation point for tourism.There are several reasons why numerical tourism capacity is inadequate.Alternatively,tourism capacity can be defined in terms of limits of acceptable change,which shifts the focus from"how much use is too much"to"how much change is acceptable".This article proposes an improved conceptual framework for evaluating carrying capacity for the tourism city based on approaches used in US national parks,which consider the impact of human use on a city's economic,environmental/resource,and socio-cultural conditions.Based on the basic data of indicator values and relevant standards,the framework monitors the current indicators and predicts future indicator values; it can also be used to assess and predict TCC.     

Alteration of acetylcholinesterase activity in Semele solida (MOLLUSCA: SEMELIDAE) as a biochemical response to coastal anthropogenic impact

Acetylcholinesterase (AChE) activity was analyzed as a molecular marker indicative of exposure to organophosphorus pesticide residues in individuals of the endemic clam species Semele solida in selected coastal locations of Chile's VIII Region. AChE activity was assayed in clams from (i) Penco Beach near the mouth of the Andalién River (Concepción Bay), (ii) Lenga Beach, near the mouth of the Lenga Estuary (San Vicente Bay), and (iii) Coliumo Beach, near the mouth of the Coliumo Estuary (Coliumo Bay). We also analyzed variations in protein content of clam hemolymph, and variability in the activity of AChE in relation to the sizes of the individual clams sampled. Collection of the clams was done using routine methods, during the spring of 2005, the period during which the use of pesticides is typically intensified in the surrounding forestry and agriculture. The results showed no significant correlation of AChE activity with either the size of the clam, or with the concentration of proteins in the hemolymph. The lowest AChE activity was observed in clams from mouth of the Andalién River (187.5 ± 34.9 Umin^?1) which was significantly less than that measured in specimens collected near the mouth of the Coliumo Estuary and the mouth of the Lenga Estuary. A very close relation was observed between the degree of anthropogenic inputs, ocean dynamics, and alterations in AChE activity in S. solida. This clam appears to be a useful indicator species, and AChE activity a sensitive marker for the presence of xenobiotics.     

Low dose effects and non-monotonic dose responses for endocrine active chemicals: Science to practice workshop: Workshop summary

A workshop was held in Berlin September 12–14th 2012 to assess the state of the science of the data supporting low dose effects and non-monotonic dose responses (“low dose hypothesis”) for chemicals with endocrine activity (endocrine disrupting chemicals or EDCs). This workshop consisted of lectures to present the current state of the science of EDC action and also the risk assessment process. These lectures were followed by breakout sessions to integrate scientists from various backgrounds to discuss in an open and unbiased manner the data supporting the “low dose hypothesis”. While no consensus was reached the robust discussions were helpful to inform both basic scientists and risk assessors on all the issues. There were a number of important ideas developed to help continue the discussion and improve communication over the next few years.     

Local to regional emission sources affecting mercury fluxes to New York lakes

Lake-sediment records across the Northern Hemisphere show increases in atmospheric deposition of anthropogenic mercury (Hg) over the last 150 years. Most of the previous studies have examined remote lakes affected by the global atmospheric Hg reservoir. In this study, we present Hg flux records from lakes in an urban/suburban setting of central New York affected also by local and regional emissions. Sediment cores were collected from the Otisco and Skaneateles lakes from the Finger Lakes region, Cross Lake, a hypereutrophic lake on the Seneca River, and Glacial Lake, a small seepage lake with a watershed that corresponds with the lake area. Sediment accumulation rates and dates were established by ²¹⁰Pb. The pre-anthropogenic regional atmospheric Hg flux was estimated to be 3.0 μg m⁻² yr⁻¹ from Glacial Lake, which receives exclusively direct atmospheric deposition. Mercury fluxes peaked during 1971–2001, and were 3 to more than 30 times greater than pre-industrial deposition. Land use change and urbanization in the Otisco and Cross watersheds during the last century likely enhanced sediment loads and Hg fluxes to the lakes. Skaneateles and Glacial lakes have low sediment accumulation rates, and thus are excellent indicators for atmospheric Hg deposition. In these lakes, we found strong correlations with emission records for the Great Lakes region that markedly increased in the early 1900s, and peaked during WWII and in the early 1970s. Declines in modern Hg fluxes are generally evident in the core records. However, the decrease in sediment Hg flux at Glacial Lake was interrupted and has increased since the early 1990s probably due to the operation of new local emission sources. Assuming the global Hg reservoir tripled since the pre-industrial period, the contribution of local and regional emission sources to central New York lakes was estimated to about 80% of the total atmospheric Hg deposition.     

超声气升式环流反应器降解乐果水溶液的动力学研究

采用超声气升式环流反应器(UALR),以臭氧气体为氧化剂,以有机磷农药乐果为典型污染物,研究其降解反应动力学规律.通过对乐果降解过程的表观动力学研究,发现乐果在单独超声辐射(不通入气体,即臭氧)、臭氧(O3)氧化和超声气升式环流反应器(UALR/O2)协同下的降解均符合表观一级动力学.在乐果初始质量浓度为50 mg/L、溶液初始pH为6.0、反应液体积80 mL、超声声强0.5W/cm2、O3流量200 L/h、温度20℃、处理时间4h的条件下,采用超声(US)、O3和UALR/O3工艺,乐果的去除率分别为27%、15%和90%,乐果降解的速率常数增强因子可达到4.816.进一步从UALR/O3系统中存在US、O3和羟基自由基(·OH)协同作用的降解机理,推导出了简化的机理动力学模型.     

天津市大气颗粒物中有机标识物粒径分布的季节特征

为探讨采暖季和非采暖季大气颗粒物中有机标识组分的粒径分布特征,识别其来源,于2018年5月至2019年4月在天津采集分粒径颗粒物,利用GC-MS对9个粒径段颗粒物中17种多环芳烃(PAHs)、20种正构烷烃(n-Alkanes)和7种藿烷(hopanes)进行分析,并通过有机标识物及特征比值的方法探讨其主要来源.结果表明:非采暖季的四环多环芳烃Pyr、Ba A、Chr和五环多环芳烃BbF、Ba P呈3峰分布,其余PAHs呈双峰分布,采暖季的低环PAHs呈双峰分布,中高环PAHs近似单峰分布.根据PAHs特征比值发现,非采暖季的燃煤源和交通源是PAHs的主要贡献源,采暖季PAHs受燃煤源的影响更显著.非采暖季的正构烷烃中C29呈单峰分布,C27、C31、C32和C33近似单峰分布,其余正构烷烃呈双峰分布,采暖季的正构烷烃均呈双峰分布.根据正构烷烃碳优势指数(CPI)和主碳峰数(C_max)发现,人为源是正构烷烃的主要来源,非采暖季受自然源的影响大于采暖季,自然源排放的正构烷烃倾向于富集在粗颗粒物上,人为源排放的正构烷烃则更倾向于富集在细颗粒物上.藿烷在粗粒径段和细粒径...     

典型工业园污染源羰基化合物排放特征研究

选取中国华东地区某工业园新区典型行业企业进行现场采样,利用PFPH衍生化-GC/MS联用技术进行羰基化合物(CBCs)的组成特征和含量水平检测,研究其排放特征。结果表明,在该工业园新区内共检出22种CBCs,各化合物的质量浓度为0.008~239.4μg/m~3,各企业CBCs总质量浓度均值为(437.62±64.45)μg/m~3,工业污染源排放贡献率由高至低顺序依次为涂料制造橡胶制造医药制造化学品制造金属制造电子元件制造。根据各物质化学反应活性及大气化学寿命,获得该工业园新区典型的CBCs分子标志物为甲醛、乙醛、丙酮、丙醛、2-丁酮、丁醛、己醛、环己酮和苯甲醛,它们占总CBCs含量的80.01%,其中乙醛含量最高,质量浓度均值高达(95.42±71.48)μg/m3。最后,建立了6种典型工业污染源CBCs成分谱。     

全氟辛烷磺酸对斑马鱼肝脏影响机制的代谢组学研究

为探究全氟辛烷磺酸(PFOS)对水生动物肝脏的慢性毒性毒害机制,寻找其肝脏慢性毒性相关的潜在标志物,运用气相色谱-质谱联用仪代谢组学方法研究暴露于PFOS中斑马鱼肝脏内源性代谢物的变化,寻找显著性差异代谢物及相关通路。实验分为4组:对照组及PFOS浓度分别为10、100、250μg·L~(-1)的实验组,每组20尾斑马鱼,实验时长40 d。结果显示,与对照组相比,PFOS浓度为10μg·L~(-1)的斑马鱼肝脏中筛选出4种发生显著性变化的代谢物,分别为牛磺酸、磷酸乙酰胺、β-D-葡萄糖、油酸,涉及4条代谢通路,即牛磺酸和亚牛磺酸代谢、鞘脂代谢、甘油磷脂代谢、糖酵解或葡萄糖生成。100μg·L~(-1)浓度组的斑马鱼肝脏中筛选出5种,包括牛磺酸、β-D-葡萄糖、棕榈酸、油酸、胆固醇,涉及5条代谢通路,即原代胆汁酸生物合成、牛磺酸和亚牛磺酸代谢、类固醇生物合成、类固醇激素生物合成、糖酵解或葡萄糖生成。250μg·L~(-1)浓度组的斑马鱼肝脏中筛选出5种,即牛磺酸、β-D-葡萄糖、乳酸、甘油-3-磷酸、磷酸乙酰胺,涉及5条代谢通路:牛磺酸和亚牛磺酸代谢、甘油磷脂代谢、甘油脂代谢、鞘脂代谢、糖酵解或葡萄糖生成。根据筛选出的差异代谢物生理功能和其涉及代谢通路分析,推测PFOS主要通过影响牛磺酸和亚牛磺酸代谢、糖酵解或葡萄糖生成及一些脂类代谢从而对斑马鱼肝脏产生毒性效应,其中牛磺酸、葡萄糖与油酸这3种代谢物可作为斑马鱼受PFOS胁迫肝脏代谢异常的潜在标记物。     

Molecular approaches to microbiological monitoring: fecal source detection

Molecular methods are useful both to monitor natural communities of bacteria, and to track specific bacterial markers in complex environments. Length-heterogeneity polymerase chain reaction (LH-PCR) and terminal restriction fragment length polymorphism (T-RFLP) of 16S rDNAs discriminate among 16S rRNA genes based on length polymorphisms of their PCR products. With these methods, we developed an alternative indicator that distinguishes the source of fecal pollution in water. We amplify 16S rRNA gene fragments from the fecal anaerobic genus Bacteroides with specific primers. Because Bacteroides normally resides in gut habitats, its presence in water indicates fecal pollution. Molecular detection circumvents the complexities of growing anaerobic bacteria. We identified Bacteroides LH-PCR and T-RFLP ribosomal DNA markers unique to either ruminant or human feces. The same unique fecal markers were recovered from polluted natural waters. We cloned and sequenced the unique markers; marker sequences were used to design specific PCR primers that reliably distinguish human from ruminant sources of fecal contamination. Primers for more species are under development. This approach is more sensitive than fecal coliform assays, is comparable in complexity to standard food safety and public health diagnostic tests, and lends itself to automation and high-throughput. Thus molecular genetic markers for fecal anaerobic bacteria hold promise for monitoring bacterial pollution and water quality.