An assessment of carcass counting surveys with increasing time lapse following a simulated fish kill on a small upland stream

A simulated fish kill was conducted on a small upland stream in Northern Ireland by planting out hatchery‐produced brown trout Salmo trutta L. carcasses of various size categories. Standard, post‐fish kill, assessment walkover surveys were conducted over time intervals to determine the number of carcasses visible. The sample variance between individual surveyors was generally low, with good agreement between the observed counts for the three, discrete, size fractions of fish up to 72 hr after the simulated fish kill. Despite low discharge rates, shallow water and good accessibility to the experimental stream, only 52% of the small category fish (<8 cm L_F) were recorded 4 hr after the start of the simulated fish kill. Larger carcasses (>17 cm L_F) were more visible, and >90% were detected 48 hr after the start of the simulated fish kill. After 96 hr, all size fractions of carcasses had reduced significantly, and the variability between replicate surveys increased markedly.     

A stochastic surplus production model in continuous time

Surplus production modelling has a long history as a method for managing data‐limited fish stocks. Recent advancements have cast surplus production models as state‐space models that separate random variability of stock dynamics from error in observed indices of biomass. We present a stochastic surplus production model in continuous time (SPiCT), which in addition to stock dynamics also models the dynamics of the fisheries. This enables error in the catch process to be reflected in the uncertainty of estimated model parameters and management quantities. Benefits of the continuous‐time state‐space model formulation include the ability to provide estimates of exploitable biomass and fishing mortality at any point in time from data sampled at arbitrary and possibly irregular intervals. We show in a simulation that the ability to analyse subannual data can increase the effective sample size and improve estimation of reference points relative to discrete‐time analysis of aggregated annual data. Finally, subannual data from five North Sea stocks are analysed with particular focus on using residual analysis to diagnose model insufficiencies and identify necessary model extensions such as robust estimation and incorporation of seasonality. We argue that including all known sources of uncertainty, propagation of that uncertainty to reference points and checking of model assumptions using residuals are critical prerequisites to rigorous fish stock management based on surplus production models.     

重庆市荣昌区饮用水源地环境评估与管理对策

为保障城镇居民饮水安全,从水源地环境管理状况和水源地水质评价2个方面对环境状况进行评估。结果表明,虽然高升桥饮用水源地综合评估结果为优秀,水质状况较好,但在水源地管理方面仍存在较多问题。针对监测能力、监管能力不足和群众环保意识薄弱等问题,提出了相关对策。     

校园环境噪声监测与评价--以华中师范大学为例

环境噪声是环境质量评价的重要指标。通过噪声监测实验,记录了华中师范大学校园内的噪声污染数据,根据国家标准评估了校园环境噪声状况。试验采用网络剖分法,分别于昼间7:30~10:00和夜间22:00~22:55两个时间段对等效声级进行了测定。实验结果表明:昼间噪声污染更为严重,平均噪声超标率达到26%,夜间噪声污染相对较轻,但噪声超标率也达到19%。校园内不同功能区的噪声来源不同,工程施工产生的噪声是主要的污染源,影响比重达到58%。根据实验结果,校园声环境质量一般,需要对现状提出合理的改进建议。     

我国喀斯特断陷盆地石漠化区植物群落构建机制研究

喀斯特断陷盆地是我国石漠化综合治理8大喀斯特类型中治理成效最低、治理难度最大的区域，面临石漠化严重、干旱频发、植被恢复难等突出问题。文中针对水分是影响喀斯特断陷盆地石漠化治理与植被恢复成效最关键的限制因素，综合分析了国内外水分梯度差异与植物群落构建机制研究动态与发展趋势；提出利用日趋成熟的水分脆弱性评价方法，通过建立基于耦合暴露度、敏感性及适应性的水资源脆弱性评价指标体系，以满足遥感影像分辨率和植物群落调查样地大小的评价单元进行水分脆弱性评估；在建立物种库—功能性状—生境特征数据库的基础上，提出基于功能性状差异进行喀斯特断陷盆地植物群落机制构建的研究方案。提出的研究方案有望解决喀斯特断陷盆地石漠化区水分梯度特征与分布格局、自然植物群落组配规律及其生境特征、水分梯度与生境要素对植物群落特征及功能性状组成的影响规律等关键科学问题，可为不同脆弱生态区植被恢复群落构建机制研究提供重要参考和借鉴。     

山地校园不同下垫面雨水径流重金属污染特征和健康风险评估

[目的] 了解山地校园不同下垫面雨水径流重金属污染特征及雨水径流中重金属元素对于人体的健康风险，为山地海绵城市建设提供径流污染控制参考和人员健康保护基础数据。[方法] 2019年7月22日在重庆交通大学针对屋顶、道路、停车场和广场4种典型的下垫面进行了雨水径流的取样监测，并统计分析场次降雨平均浓度（EMC）、电导率（EC）、钠吸附率（SAR）、危险商（HQ）和危险指数（HI）。[结果] 广场径流过程中重金属元素整体变化波动较大，道路雨水径流的重金属健康风险最大而屋顶健康风险最小；大多重金属污染物在产流后的10 min内出现了降幅，其中Fe和Mn的降幅较大，Zn的降幅中等，Cu的降幅最低；As和Cr是雨水径流中健康风险最高的重金属污染物。[结论] 山地校园重金属污染物冲刷速度较快，人流大的下垫面雨水径流中重金属元素变化波动较大，但健康风险较低；车流大的下垫面雨水径流中重金属元素波动较为稳定，但健康风险较高。     

基于GIS的湖南省滑坡灾害风险和损失评估

[目的] 评估湖南省滑坡发生的风险和损失等级，丰富湖南省滑坡防治理论及方法，为该地减少滑坡灾害提供科学依据。[方法] 基于GIS技术和层次分析法（AHP）以DEM、遥感、气象、岩性、地震点等数据为支撑，分别从危险性评价和易损性评价两方面对湖南省滑坡风险进行评估。[结果] ①湖南省滑坡风险等级大多处于中低风险等级，少部分为较高风险或高风险等级，中度风险等级最多，占全省面积的31.31%，其余依次为较低、较高、低和高风险等级，其比例分别是24.92%，22.09%，13.88%和7.79%；②从空间格局来看，风险性等级整体呈现出中部、东南高，西南、东北低的空间分布特征；③湖南省滑坡损失等级整体呈现出东高西低，局部不均匀的分布特征。[结论] 湖南省滑坡灾害的管理主要应从预防和整治两方面进行，依据各地区常见滑坡类型，制定有针对性的区域差异化防治预案。     

茶园土壤-茶树-茶叶-茶汤中镉转移规律及安全性评价

为论证镉污染土壤种植茶树的安全性与可行性,通过盆钵茶园试验研究了湖南9个主栽茶树品种在不同镉含量土壤中对镉的吸收积累特性和茶汤中镉元素的浸出率。结果表明,在pH值4.1的土壤中,通过根系吸收的镉元素从根系到主干,再到侧枝枝干和茶树叶片的转运过程中,各器官的镉含量依次递减,茶树嫩芽(叶)中镉的富集系数仅0.13~0.24;茶树种植在土壤镉含量低于3.0 mg/kg的土壤中,茶叶没有出现镉超标现象;镉元素在茶汤中的平均浸出率为9.87%,利用膳食暴露风险评估模型对茶叶和茶汤中的镉含量进行风险评估,表明供试茶叶样品中的镉不会对人体健康产生威胁。     

Skating on thin ice: Identifying the need for species‐specific data and defined migration ecology of Rajidae spp.

Skates (class Chondrichthyes; subclass Elasmobranchii; order Rajiformes; family Rajidae) comprise one quarter of extant chondrichthyans, yet have received little attention in the scientific literature likely due to their relatively low economic value and difficulties in species identification. The absence of species‐specific information on catch, life history and migration of skates has often precluded the development of single‐species stock assessments and led to the use of cursory multispecies assessments, which lack the ability to track species‐specific catch and abundance trends. This has resulted in undetected local extirpations, as has been previously reported for common (Dipturus batis, Rajidae), white (Rostroraja alba, Rajidae) and long‐nose (Dipturus oxyrhinchus, Rajidae) skates in the Irish Sea. Here, we (a) use case studies to illustrate how the perception of skate population structure and stock status has historically been masked through multispecies assessment and management practices, (b) review current information on the movement of skates and identify gaps in knowledge, and (c) identify biases associated with the use of various tagging technologies, which have confounded our understanding of movement and migration ecology of skates. Considering that over 40% of extant Rajidae species are listed as “Data Deficient” by the International Union for Conservation of Nature, we illustrate a critical need to broaden the current understanding of skate life history, movement and migration ecology by providing recommendations on the further application of electronic tags and biogeochemical natural tags in movement studies and highlight the benefits that studies using these approaches have for novel management frameworks.