Comparing aquatic risk assessment methods for the photosynthesis-inhibiting herbicides metribuzin and metamitron

Three different risk assessment procedures are described that aim to protect freshwater habitats from risks of the photosynthesis-inhibiting herbicides metribuzin and metamitron. These procedures are (1) the first-tier approach, based on standard toxicity tests and the application of an assessment factor, (2) the Species Sensitivity Distribution (SSD) approach, based on laboratory tests with a wider array of species and the application of a statistical model to calculate the HCx (the Hazardous Concentration for x% of the species), and (3) the model ecosystem approach, based on the evaluation of treatment-related effects in field enclosures. A comparison of the risk assessment procedures reveals that the first-tier approach is the most conservative for metamitron and metribuzin, and that HC5 values (and even HC10 values) based on acute EC50 values of algae and aquatic vascular plants may be used to derive maximum permissible concentrations for single applications. For both compounds these HC5 values were very similar to the ecological threshold concentrations in the enclosure studies. In contrast to model ecosystem experiments, however, HCx values based on lab toxicity tests do not provide information on the recovery potential of sensitive endpoints and on indirect effects, which may be important for regulatory decision-making. In the enclosure study, indirect effects of metribuzin on invertebrate populations were observed at an exposure concentration that was approximately 20 times lower than the corresponding HC5 value based on lab toxicity data for aquatic invertebrates.     

Haloacetic acids in the aquatic environment. Part II: ecological risk assessment

Haloacetic acids (HAAs) are environmental contaminants found in aquatic ecosystems throughout the world as a result of both anthropogenic and natural production. The ecological risk posed by these compounds to organisms in freshwater environments, with a specific focus on aquatic macrophytes, was characterized. The plants evaluated were Lemna gibba, Myriophyllum spicatum and M. sibiricum and the HAAs screened were monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA). Laboratory toxicity data formed the basis of the risk assessment, but field studies were also utilized. The estimated risk was calculated using hazard quotients (HQ), as well as effect measure distributions (EMD) in a modified probabilistic ecological risk assessment. EMDs were used to estimate HAA thresholds of toxicity for use in HQ assessments. This threshold was found to be a more sensitive measure of low toxicity than the no observed effect concentrations (NOEC) or the effective concentration (EC10). Using both deterministic and probabilistic methods, it was found that HAAs do not pose a significant risk to freshwater macrophytes at current environmental concentrations in Canada, Europe or Africa for both single compound and mixture exposures. Still, HAAs are generally found as mixtures and their potential interactions are not fully understood, rendering this phase of the assessment uncertain and justifying further effects characterization. TCA in some environments poses a slight risk to phytoplankton and future concentrations of TFA and CDFA are likely to increase due to their recalcitrant nature, warranting continued environmental surveillance of HAAs.     

2013年1月南京强霾时期大气细颗粒物污染特征分析

2013年1月,南京经历了一次重大持续性灰霾污染过程。利用在线气体及气溶胶监测系统和扫描电迁移率颗粒物粒径谱仪,通过研究颗粒物质量浓度,主要水溶性无机离子浓度,不同时段颗粒物的数谱分布及其日变化分布,二次气溶胶及黑碳与能见度的相关性等多个方面,较为全面地分析了重霾时期大气细颗粒物的污染特征。     

COMPARISON OF DESIGN STORM CONCEPTS USING CONTINUOUS SIMULATION WITH SHORT DURATION STORMS1

ABSTRACT: The objectives of this paper were to test the ability of various design storm distributions to simulate the actual rainfall pattern and to compare the runoff rates used in the design of stormwater management devices in the State of Florida using continuous simulation approach. The analyses were performed for four gaged stations to evaluate the applicability of design storm distributions in different parts of the State of Florida. The approach used in this study compared the peak runoff rates from design storms based on the various distributions to those that would result from actual rainfall events. A series of continuous runoff rates were developed through the use of actual fifteen-minute recorded rainfall data, Horton type infiltration decay and recovery rate, and a continuous simulation model. The runoff rates were analyzed using frequency distributions to obtain peak runoff rates associated with different return periods based on the assumption that the continuous simulation approach closely predicts the actual runoff rates from the gaged stations. The results show that the behavior of the design storm distributions varies for different watershed characteristics in different parts of the state. The study also suggests that in general the Florida Department of Transportation and the Suwanne River Water Management (FDOT/ SRWMD) distributions appeared to agree with the continuous simulation results.     

2000~2011年深圳湾及邻近水域颗粒有机物的来源和时空分布

依据2000~2011年每月一次的调查资料,简要描述和讨论了深圳湾及邻近水域中颗粒有机物(POM)质量浓度的时空分布,并结合盐度和叶绿素a (Chl a)实测数据探讨POM的来源和滞留时间.结果表明深圳湾的POM质量浓度和陆源质量分数分别约为4.2mg/L,79%,而伶仃洋东部沿岸的分别约为1.9mg/L,42%.深圳湾和伶仃洋东部沿岸中现存浮游植物颗粒有机物(PPOM):Chl a比率分别约为92,54g/g,由此估算的PPOM质量浓度分别为0.8,0.2mg/L左右.依据浮游植物生产力和累计海源POM估算的POM滞留时间在深圳湾中为1~5d,而在伶仃洋东部沿岸中约为10d.研究期间伶仃洋东部沿岸POM质量浓度的年际变化略呈上升趋势,从1.7mg/L上升至2.0mg/L;深圳湾POM质量浓度在2000~2005年呈上升趋势,从3.0mg/L上升至5.5mg/L,在2006~2011年则呈下降趋势,从5.4mg/L下降至3.0mg/L.     

太湖水体多环芳烃生态风险的空间分布

以太湖梅梁湾、贡湖湾和胥口湾水体多环芳烃(PAHs)含量水平为基础,通过物种敏感度分布曲线计算三湖湾水体PAHs对水生生物的潜在危害比例,以此表征PAHs对太湖三湖湾水体的生态风险,并对其空间分布特征进行讨论.结果表明:PAHs对太湖三湖湾水体的生态风险大小依次是:Flua(1.1641%),Phe(0.2206%),Pyr(0.1633%),BaP(0.0175%),Ant(0.0021%),Flu(0.0005%), Ace(0.0000%),∑7PAH的联合生态风险(3.0954%)大于单体PAHs的生态风险. Ant, BaP和∑7PAH对梅梁湾(0.0209%,0.1237%和4.1018%)的生态风险显著高于贡湖湾(0.0023%,0.0085%,3.0414%)和胥口湾(0.0002%,0.0015%,2.3899%)(P0.05);Flu和Phe对胥口湾(0.0004%,0.1553%)的生态风险显著低于梅梁湾(0.0011%,0.2999%)和贡湖湾(0.0009%,0.2681%)(P0.05);Pyr和Flua对梅梁湾(0.3268%,1.7156%),贡湖湾(0.1697%,1.2386%)和胥口湾(0.1044%,0.8339%)水生生物的生态风险具有显著性差异(P<0.05).空间分布表明:梅梁湾西北部PAHs的生态风险最大,贡湖湾北部次之,胥口湾最小.     

An Analysis of the Wind Energy Potential of Elazig,Turkey

Abstract

In this study, the wind energy potential of Elazig is statistically analyzed based on hourly measured wind speed data over the five-year period from 1998 to 2002. The probability density distributions are derived from cumulative distribution functions. Two probability density functions are fitted to the measured probability distribution on a yearly basis. The wind energy potential of the location is studied based on the Weibull and Rayleigh distributions. It was found that the numerical values of both Weibull parameters (k and c) for Elazig vary over a wide range. The yearly values of k range from 1.653 to 1.878 with an average value of 1.819, while those of c are in the range of 2.757–2.994 m/s with an average value of 2.824 m/s. In addition, yearly mean wind speed and mean power density of Elazig is found as 2.79 m/s and 38.76 W/m², respectively. The wind speed distributions are represented by Weibull distribution and also by Rayleigh distribution, with a special case of the Weibull distribution for k = 2. As a result, the Rayleigh distribution is found to be suitable to represent the actual probability of wind speed data for Elazig.     

On the use of correlated beta random variables with animal population modelling

We give reasons why demographic parameters such as survival and reproduction rates are often modelled well in stochastic population simulation using beta distributions. In practice, it is frequently expected that these parameters will be correlated, for example with survival rates for all age classes tending to be high or low in the same year. We therefore discuss a method for producing correlated beta random variables by transforming correlated normal random variables, and show how it can be applied in practice by means of a simple example. We also note how the same approach can be used to produce correlated uniform, triangular, and exponential random variables.     

鄱阳湖微囊藻毒素时空分布格局及其与理化和生物因子的关系

本文分别于2012年4月(春季)、8月(夏季)、10月(秋季)和2013年1月(冬季)在鄱阳湖进行了4次野外调查和样品采集,采用超高效液相色谱-串联质谱仪(UPLC-MS/MS)对鄱阳湖水柱中常见的3种微囊藻毒素(MC-RR、MC-YR和MCLR)的质量浓度进行定量分析,探寻了微囊藻毒素(microcystins,MCs)质量浓度的时空变化规律及其与湖泊环境理化因子和生物因子之间的关系.结果表明,MC-RR是鄱阳湖MCs的主要毒素种类.胞内微囊藻毒素(intracellular MCs,IMCs)与微囊藻生物量(r=0.47,P0.01)、颤藻生物量(r=0.68,P0.01)、蓝藻生物量(r=0.56,P0.01)、Chl-a(r=0.28,P0.01)之间均具有显著的正相关关系,但与鱼腥藻生物量之间没有明显的相关关系(P0.05),这说明微囊藻和颤藻是鄱阳湖微囊藻毒素的主要产毒藻类.IMCs与水温(r=0.51,P0.01)、透明度(r=0.69,P0.01)、Fe(r=0.43,P0.01)和Zn(r=0.43,P0.01)之间均呈现显著的正相关关系,与TN(r=-0.44,P0.01)、TP(r=-0.29,P0.01)、NO-2-N(r=-0.28,P0.05)、NH+4-N(r=-0.33,P0.05)、Ca(r=-0.34,P0.01)和Mg(r=-0.35,P0.05)均呈现显著的负相关关系,但与pH、PO3-4-P、NO-3-N、电导率、高锰酸盐指数、Cu离子之间的相关关系不显著(P0.05),这说明光照强度(透明度反映)、氮、磷、水温是控制鄱阳湖微囊藻毒素产生的重要因子,金属离子Ca、Mg、Fe、Zn在一定程度上能影响微囊藻毒素的产生.鄱阳湖IMCs和胞外微囊藻毒素(extracellular MCs,EMCs)呈现相似的季节变化趋势,即夏季最高,其次为秋季,冬季和春季较低.鄱阳湖IMCs的空间分布整体上呈现东部湖汊群、松门山周围以及蚌湖和蚌湖进入鄱阳湖的入湖口较高,其它区域较低的趋势,而EMCs的高值区位于松门山周围和蚌湖及其入湖口.     

延河流域降雨侵蚀力时空分布特征

降雨侵蚀力(R)反映了降水引起土壤水蚀的潜在能力,其时空分布规律定量研究是进行土壤侵蚀预报的基础.利用延河流域22个雨量站24a逐日降雨资料,分析了该区降雨侵蚀力的时空分布特征.结果表明,降雨侵蚀力与降雨量、侵蚀性降雨量具有一致的年内年际变化趋势.降雨侵蚀力年内变化为单峰型,集中分布在5～9月,占全年R值的91.61%.降雨侵蚀力多年平均值为1580.58MJ.mm.(hm2.h.a)-1,最高值(1981年)为2417.70MJ.mm.(hm2.h.a)-1,最低值(1999年)仅585.29MJ.mm.(hm2.h.a)-1,年际间变化为中等变异,变异系数为0.32.烧房砭站多年平均R值最大,为2190.33MJ.mm.(hm2.h.a)-1,镰刀湾和杨山站多年平均R值最小,分别为1151.37MJ.mm.(hm2.h.a)-1和1146.87MJ.mm.(hm2.h.a)-1.R值与侵蚀性降雨量具有一致的空间分布格局,北部雨量站R值年际变化呈现轻微的增加趋势,其它站点R值年际变化相对呈现出轻微的减少趋势,总体上延河流域降雨侵蚀力呈现下降趋势,趋势系数为-0.004.