Invisible homelessness: anonymity,exposure, and the right to the city

The city of Denver, Colorado recently outlawed camping in all open space. Part of a broad effort to accelerate the profit potential of prime urban land through real estate speculation and commerce, the camping ban has dislocated homeless people from the city’s marginal spaces. Based on ethnographic fieldwork and archival research in Denver, this article develops a tripartite approach to public space—prime, everyday, and marginal—to analyze challenging ways in which people who are homeless in Denver must now manage their exposure to others in everyday public spaces. In addition to eliminating places of hard-won safety and security, this singular new code disrupts hygiene, mobility, and sociability routines, thus throwing already precarious lives into further disarray by rendering housing status visible. To demonstrate how everyday social justice springs from interaction between different people co-present in public space, we foreground the voices of Denver’s homeless people, those most impacted by quality of life laws. Evicting individuals from marginal spaces and rendering them visibly homeless in everyday and prime spaces, the ban deprives them of a fundamental right to the city: anonymity.     

Socioeconomic characteristics and crash injury exposure: A case study in Florida using two-step floating catchment area method

The objective of this study is to investigate the exposure of different population groups to severe injury crash hotspots using an empirical-Gaussian two-step floating catchment area (EG-2SFCA) method based on roadway network distances and a socioeconomic-based weighting approach. This is performed by developing a special form of a crash-to-population ratio index that incorporates the severe crash hotspots relative to the locations of populations they might impact. While identifying these hotspots, four different age groups are considered: 17 and younger, 18 to 21, 22 to 64 and 65 and older. For each age group, severe crash hotspots are identified based on the roadway network and the number of severely injured crash occupants that belong to the specific age group. Using these age-specific crash hotspots and the EG-2SFCA method, communities that were exposed to elevated crash injury risk (crash injury exposure) have been identified. Furthermore, from a residential perspective, a socioeconomic analysis is conducted in order to develop a socioeconomics-based crash injury exposure measure. This measure assesses the exposure of different socioeconomic groups to the risk of being injured. Results demonstrated by applying this measure in the Tampa Bay region, FL show that different population groups are under varying risk of being injured depending on their residential location. The developed approach has the potential to be a social fairness measure able to be applied by agencies, which could enhance the well-being of communities that are subject to elevated injury risk.     

黄河口及其附近海域沉积物中As的粒度校正(Ⅱ)

本文着重讨论利用沉积物外比表面校正法对黄河口及其附近沉积物中As进行粒度校正,并与上文讨论的≤16μm粒径外推校正法及中值粒径校正法进行了比较,结果外比表面法被认为是较为合理的。同时还提出利用单位外表面积沉积物活性As含量作为沉积物中As的评价标准,并可以推广到沉积物中其他污染物质的研究中去。     

Embayment characteristic time and biology via tidal prism model

Transport time scales are often offered by scientists, and accepted by ecologists, as qualitative indicators of the susceptibility of ecological components within an embayment. However, rigorous quantitative methods were never presented to confirm this intuition. Transport time scales in water bodies are classically based on their physical and chemical aspects rather than their ecological and biological character. The direct connection between a physical time scale and an ecological effect has to be investigated in order to quantitatively relate a transport time scale to ecology. This concept is presented here with some general guidelines and clarifying examples. To be able to relate physical time scales to biological processes, a simple tidal prism model is developed that calculates temporal changes in concentration and the related exposure. This approach provides a quick method to calculate the characteristic time for transport in a large number of embayments, which can also help in classification endeavors.     

张八岭地区岩群出露年代研究

暴露岩石中宇生核素的浓度与暴露年代、侵蚀速率相关,暴露年代和侵蚀速率可相互求证,但两者均为未知数时,可求算出最大侵蚀速率和最小暴露年代。据此得出张八岭地区的最大侵蚀速率为7 12m/Ma,最小暴露年代为(85700±1500)a,这一年代远小于统一夷平面的形成年代(7～3 6Ma),造成这种差距的主要原因是:①张八岭地区侵蚀速率大,岩石中宇生核素的浓度较早达到平衡,即达到该地区的测年上限;②采样地区曾被土壤覆盖,造成计算年代值过于年轻。     

西南地区未来极端降水增加将导致其人口暴露风险加剧

基于CN05.1观测数据和一套经过降尺度偏差校正处理的模式(NEX-GDDP-CMIP6)数据,结合泰勒图、GEV极值拟合等方法,综合评估了模式对西南地区极端降水变化的模拟性能,并系统分析了未来西南地区不同重现期的极端降水演变趋势及其人口暴露度变化。结果表明,NEX-GDDP-CMIP6模式及其集合(N-CMIP6-MME)能够较好地再现观测极端降水的时空变化特征,且多模式集合结果优于大多数单个模式。未来西南地区绝大多数区域的降水和极端降水将持续增加,十年一遇、二十年一遇极端降水事件也呈增加趋势,使得未来西南地区人口暴露于不同重现期极端降水的风险进一步增加。相比十年一遇,重现期为20 a的极端降水事件增加速度更快,增加范围更广,模式一致性也更高,对应的人口暴露度增加幅度更大。到2050年左右,在SSP1-2.6、SSP2-4.5、SSP3-7.0和SSP5-8.5情景下二十年一遇的RX1day(RX5day)分别增加了175.2%(148.9%)、216.0%(162.4%)、210.9%(156.8%)和274.3%(207.1%),对应人口暴露度分别增加了129.1%(118.8%...     

微波消解-化学蒸气发生-原子荧光光谱法同时测定铁矿石中的痕量砷和汞

采用HCl-HNO3混合酸(体积比1∶1)微波消解铁矿样品,在消解后的样品母液中直接加入硫脲-抗坏血酸,预还原五价砷为三价砷,消除铁和其他共存离子对砷、汞测定的干扰,采用化学蒸气发生-双道原子荧光光谱法同时测定铁矿石中的痕量砷和汞。结果表明5%的HCl-HNO3混合酸(体积比1∶1)、20 g/L硼氢化钾溶液能有效保证砷、汞双元素的同时测定,制备的砷、汞标准使用溶液在2～5℃下密闭保存,在245 d内具有稳定性。砷的检出限为0.085μg/L,汞的检出限为0.008μg/L。通过分析5个铁矿石有证标准物质,测定As的相对标准偏差为0.9%～5.5%,回收率为77.7%～105.4%,检测值与标准值吻合;测定Hg的相对标准偏差为1.1%～3.7%,回收率为86.2%～113.2%。本方法是以牺牲汞元素的检出限来实现砷、汞两元素的同时测定,是建立在砷、汞单独测定基础上的一种快速检测方法,经全国不同地区9家实验室采用5个标准样品进行协同实验验证,能够满足日常分析要求。     

砷的水地球化学及其环境效应

砷在水环境中的迁移和富集可以产生严重的砷污染，砷在自然水系中主要以无机砷酸盐（AsO4^3-）和亚砷酸盐（AsO3^3-）两种形式存在，而砷的有机化合物的含量一般都很低，砷酸盐在富氧化性的水体中占优势，而亚砷酸盐则富集于还原性水体中，水体中As3 和As5 的相对含量主要受氧化还原条件和一些吸附一解吸平衡过程控制，As3 类比As5 类的毒性强得多，而无机砷化合物比有机砷化合物的毒性大，在pH值为5－6时，As^5 不易被还原成气态AsH3，而s^3 却能定量地被还原出来，根据这一性质，可完成水体中As3 和As5 的测定，砷在饮用水中的安全阀值仅为10ug/L，水体中高砷的危害可以通过水质净化予在消除或降低，铁的化学沉淀和吸附法，石灰软化法，活性氧化铝净化法和逆流渗透法等都可以有效地去除或降低饮用水中砷的含量。     

断续流动-氢化物发生-双道原子荧光光谱法测定地下水中的微量砷汞

采用断续流动进样氢化物发生-双道原子荧光光谱法测定地下水中的砷、汞,确定仪器的最佳条件,考察了酸度,预还原剂和还原剂用量和载流流速的影响以及共存元素的干扰情况,在选定的条件下,砷的检出限0.0109μg/L,相对标准偏差为1.10%,回收率为95.7～102.2,汞的检出限0.0023μg/L,相对标准偏差0.87%,回收率为95.5～103.0.     

铁盐絮凝法对阳宗海湖泊水体的除砷效果及底泥的稳定性考察

2008年,昆明阳宗海受到严重砷污染,砷浓度高达0.134 mg/L。项目组充分考虑其受污染水体容量大、砷浓度低的实际情况,提出了安全、廉价、高效的FeCl3絮凝法治理方案。实验室小试结果表明,提出的FeCl₃絮凝法对As(Ⅲ)及As(V)均有理想的去除效果,并且湖水中大量存在的阴离子HCO^-₃可使治理过程中水体pH值基本保持不变。因此该方案摒弃了文献普遍报道所需要的预氧化及调节pH值的工艺步骤,将固体FeCl₃·6H₂O溶解、用湖水稀释后通过喷洒船将最终浓度为1%左右的FeCl₃水溶液喷洒到湖面上,使湖水中的AsO^3-₄及AsO^-₂与FeCl₃水解过程产生的Fe(OH)3胶体絮凝形成稳定的沉淀物被固定于底泥中。在对阳宗海进行降砷工程化治理期间,2009年11月-2010年9月砷浓度从0.117 mg/L快速下降到0.021 mg/L并可持续达到Ⅱ-Ⅲ类水标准(<0.05 mg/L),总除砷率高达 82.05%。沉积物中的As绝大部分以残渣态的形式被固定在沉积物中,生态风险很低。