Validation of chemical speciation model of inorganic arsenic in river waters with mobilisation processes

Abstract

The thermodynamic model of inorganic arsenic (acid–base, complexation, precipitation and redox equilibria) was validated with results obtained in arsenic mobilisation processes taking place in several river sediment samples of the Basque Country (North of Spain). Natural waters in contact with the sediment were collected at each sampling point, together with the sediment samples. These waters were analysed and then used as the extractant in the mobilisation studies. Considering pH, redox potential and total concentration values of the main cations and anions, the stoichiometric equilibrium constant were computed for each river water situation. The activity coefficient values of the inorganic arsenic species were estimated by means of the Modified Bromley Methodology (MBM). Both water and sediment for each sampling site were used in the mobility experiments, and the results were compared with the theoretical predictions of the thermodynamic model extrapolated to the chemical conditions of the sampling point. Moreover, a correlation analysis was also performed taking into account all the data and sampling sites; these results were also discussed and compared with the theoretical speciation obtained from the basic model of inorganic arsenic.     

Uncertainty associated with river health assessment in a varying environment: The case of a predictive fish-based index in France

Sensitive biological measures of river ecosystem quality are needed to assess, maintain or restore ecological conditions of water bodies. Since our understanding of these complex systems is imperfect, decision-making requires recognizing uncertainty. In this study, a new predictive multi-metric index based on fish functional traits was developed to assess French rivers. Information on fish assemblage structure, local environment and human-induced disturbances of 1654 French river sites was compiled. A Bayesian framework was used to predict theoretical metric values in absence of human pressure and to estimate the uncertainty associated with these predictions. The uncertainty associated with the index score gives the confidence associated with the evaluation of site ecological conditions.Among the 228 potential metrics tested, only 11 were retained for the index computation. The final index is independent from natural variability and sensitive to human-induced disturbances. In particular, it is affected by the accumulation of different degradations and specific degradations including hydrological perturbations. Predictive uncertainty is globally lower for IPR+ than for underlying metrics.This new methodology seems appropriate to develop bio-indication tools accounting for uncertainty related to reference condition definition and could be extended to other biological groups and areas. Our results support the use of multi-metric indexes to assess rivers and strengthen the idea that examination of uncertainty could contribute greatly to the improvement of the assessment power of bio-indicators.     

Using the Ecological Risk Index Based on Combined Watershed and Administrative Boundaries to Assess Human Disturbances on River Ecosystems

Efforts at the restoration of river ecosystems are needed not only in local habitats but are also important in terrestrial regions. Large-scale assessment of human activities can be useful in integrated watershed management. In this study, we modified the Ecological Risk Index (ERI) by considering the spatial distribution of human activities in China's Haihe River Basin (HRB). The stressor factors of human activities included population, impervious surface, cattle, agricultural land use, industry, fertilizers, pesticides, water conservation facilities, and roads. A total of 423 assessment units in the HRB were created by combining watershed and administrative boundaries to analyze the spatial distribution of human activities. Two index options, the ERI (including all stressors) and the ERI-D (excluding reservoirs and sluices), were examined for different management objectives. All the stressors and both ecological risk indices (ERI and ERI-D) were ranked in four levels: low, moderate, high, and very high. Our study demonstrated that the ERI and ERI-D can provide an overview of the spatial pattern of human stressors related to river ecosystems across a large geographic region. The approach developed in this study is useful for prioritizing management actions in targeted areas.     

How Subchronic and Chronic Health Effects can be Neglected for GMOs, Pesticides or Chemicals

Chronic health effects are increasing in the world such as cancers, hormonal, reproductive, nervous, or immune diseases, even in young people. During regulatory toxicological subchronic tests to prevent these on mammalian health, prior commercialization of chemicals, including pesticides and drugs, or GMOs, some statistically significant findings may be revealed. This discussion is about the need to investigate the relevant criteria to consider those as biologically significant. The sex differences and the non linear dose or time related effects should be considered in contrast to the claims of a Monsanto-supported expert panel about a GMO, the MON 863 Bt maize, but also for pesticides or drugs, in particular to reveal hormone-dependent diseases and first signs of toxicities.     

Aquatic macrophyte breakdown in an Appalachian river

Weight loss from Podostemum ceratophyllum, Elodea canadensis, Potamogeton crispus, Justicia americana, and Typha latifolia was measured by exposing air dried leaf material in 15 cm² nylon mesh bags (3 mm octagonal openings). Breakdown rates for these species were 0.037, 0.026, 0.02l, 0.016, and 0.007 day^–1, respectively. In general, these rates are much faster than reported rates of tree leaf breakdown in streams. Shredders accounted for 35% of the macroinvertebrates found on the leaf bags. However, macroinvertebrate densities on the aquatic macrophyte tissue were well below densities commonly found on leaf bags in small streams. The rapid breakdown of aquatic macrophytes in the New River suggests that organic matter from this source may constitute a significant pulse in the annual energy dynamics of the river.     

管网雨水补给河道用水的人工湿地水质净化流程研究

中国北方部分地区水资源短缺,河道干涸,但夏季雨水资源潜力丰富。虽径流受到一定污染,但较于生活污水和工业废水,其污染程度更低,成分更简单。雨水通过低运行成本的人工湿地净化系统,可以实现较好的净化效果,满足河道景观需求和生态补水。城市管网雨水承载能力过重的城市边缘区,建设更新过程中进行雨污分流制度,更适于采用人工水质净化的方式将城市雨水管网中的雨水进行就近消纳,减轻城市雨水管网压力,并利用表面负荷率（ALR）来确定并校核人工湿地面积。在综合现在人工水质净化主流程预处理单元、人工湿地单元和消毒存储单元3个环节的基础上,以低运营成本、低管理成本、最优净水量为指向,引入物联网技术智能管控系统,行程具有能控制各级出水水质监测、多级管控、净水生态功能与游览景观功能相结合等多重优点的人工水质净化全流程,达到符合河道水质标准的净化效果。该流程为缓解北方城镇河道缺水现状、解决城市雨洪问题提供新思路。     

基于地理探测器的岷江中下游地区植被NPP时空格局演变及其驱动力研究

植被净初级生产力作为反映植被生态系统对气候变化响应的重要指标,是长期以来备受世界各国关注的焦点问题。论文以岷江中下游地区为研究区域,基于2000—2015年MODIS NPP数据,结合同年期海拔、气温、降水、土地利用类型等,运用地理探测器等模型方法,诊断植被NPP分布的主要驱动力,并揭示了不同时段的驱动力决定力的变化。结果表明:(1)2000—2015年岷江中下游植被NPP平均值为513.93gC/m~2;植被年均NPP最大值出现在2000年石棉县北部硗碛藏族乡的林地分布区,为1876gC/m~2,最小值出现在2005年五通桥区中部竹根镇的平原旱地分布区,最小值为26.98gC/m~2;植被NPP具有较强的时空分异性,NPP总量变化除了受NPP强度影响外,植被覆盖总面积是其另外主要的影响因素。(2)影响植被NPP分布的主导因素包括气温、海拔、土地利用等,各因素对NPP分布的决定力存在明显差异。(3)不同时间植被NPP空间分布的驱动力存在明显差异,主要表现在其变化受人类扰动的影响越来越强烈。刻画岷江中下游植被NPP时空演变,并揭示其主要驱动力,可为研究区生态安全预警和生态补偿提供数据支撑和辅助决策。     

富平石川河的生态修复

自国家提出构建山水林田湖草生命共同体以来,已启动第三批山水林田湖草生态保护修复工程试点申报,但一些工程设计缺乏整体性,造成“真破坏”和“伪生态”的现象时有发生.本研究以石川河综合整治项目为例,针对石川河乱采乱挖河道砂石,工业污染,附近村民焚烧垃圾造成气、水和土污染极其严重,生态、人居环境持续恶化,鱼虾绝迹,污水横流,垃圾成堆等问题,采用重建生态河道、恢复生态、景观重塑、土地平整、PE复合土工膜、土壤修复等技术构建山水林田湖草生命共同体,并分析了生态、经济和社会效益,通过项目实施,为石川河流域提供了洁净的土壤环境、稳定的土体结构,有效改善了生态环境,提高了生活质量,实现生产发展、生态良好,不断满足社会发展建设美丽乡村的需要,同时为构建流域山水林田湖草生命共同体提供理论依据和实践支撑.     

城镇快速发展对河流温室气体溶存及扩散通量的影响——以重庆市黑水滩河流域场镇为例

场镇发展是西南山区城镇发展的重要模式,且大部分场镇沿河分布,快速城镇发展给河流水环境及生物地化过程带来了一系列影响,然而其对河流温室气体排放时空格局的影响及机制尚不清楚。选择流域场镇发展特征明显的黑水滩河为研究对象,于2014年9月、12月、2015年3月、6月,对流域内干、支流水体温室气体浓度及扩散通量进行分析,旨在阐明流域场镇式发展下河流温室气体排放时空特征及关键驱动因素。研究结果表明,黑水滩河干、支流水体年均二氧化碳分压(pCO_2)及甲烷(CH_4)、一氧化二氮(N_2O)浓度均处于过饱和状态,是大气温室气体的净排放源;流域内干、支流水体流经不同场镇区前后水体碳、氮、磷及叶绿素a含量均不同程度增加,从上游向下游呈现明显的污染累积;水体溶存pCO_2\\CH_4\\N_2O浓度及扩散通量在不同场镇前后也呈现显著增加的趋势,三种温室气体扩散通量平均增幅分别为25.88%、55.22%、99.64%;河流水体pCO_2与N_2O浓度及通量秋季高于其他季节,CH_4浓度及扩散通量春季最高,秋季次之,夏、冬季最低,温室气体浓度及排放的季节变化主要受温度和降雨格局共同影响。相关分析表明,pCO_2与水温和pH关系密切,而水体CH_4和N_2O浓度与水体碳、氮、磷等生源要素均呈显著的正相关关系,水体CH_4与N_2O浓度对生源要素输入极为敏感,流域场镇发展带来的河流污染负荷的增加可能对水体CH_4与N_2O排放产生明显的激发效应。本研究认为,山区河流流域内沿河串珠状场镇分布对河流水体生源要素及其他理化性质产生累积影响,进而改变了水体温室气体的产生与排放时空格局。