水华对沉积物中氮的转化和去除的影响

湖泊富营养化和水华暴发已经成为突出的环境问题之一,了解水华对湖泊氮素的转化和去除的影响,对于削减湖泊氮负荷至关重要.本文研究了水华对沉积物中氮转化和氮转化相关功能基因的影响,并采用结构方程模型分析了水华影响湖泊中氮转化和去除的途径.结果表明,与厌氧氨氧化相比,反硝化作用是太湖沉积物氮削减的主要途径,对沉积物中总溶解性氮去除率的解释度为42. 3%.水华可以直接造成沉积物中TDN和TOC量的增加,提高厌氧氨氧化菌、nir S和nir K的基因丰度,并且间接提高沉积物中氨氮和硝酸盐的浓度,通过增强厌氧氨氧化和反硝化过程加速沉积物中氮的去除.     

水华束丝藻对汞的吸附-解吸特征

通过室内模拟实验,探究不同丰度的活、死水华束丝藻对Hg²⁺的吸附动力学特征和等温吸附模型以及解吸特征。结果表明,水华束丝藻对Hg²⁺有较好的吸附效果,能在短时间内吸附大量Hg²⁺,120 min左右达到吸附平衡,且活藻对Hg²⁺的吸附效果比死藻好;活藻和死藻吸附Hg²⁺的动力学过程符合准一级、准二级动力学模型,且准二级动力学模型拟合效果更好;活、死水华束丝藻对Hg²⁺的吸附分别符合Langmuir模型、D-R模型,最大吸附量分别为2.07×10^-2 ng/（10⁶ cells）、3.56×10^-2 ng/（10⁶ cells）;水华束丝藻对Hg²⁺的单位吸附量随着藻丰度的增加而减少,吸附总量随着藻丰度的增加而增加。反应初期（0～5 min）,活、死水华束丝藻对Hg²⁺进行生物吸附,吸附速度快且效率高;随后活藻依靠新陈代谢将Hg²⁺转移至细胞内进行生物富集,因而活藻的单位吸附量高于死藻。活藻和死藻对Hg²⁺的解吸量随藻丰度的增加而增加,且死藻变化更明显。     

沉水植被对河流温室气体释放减缓作用研究

为揭示沉水植物生态修复在减缓河流温室气体释放方面的作用,在浙江省嘉善县选择盛家湾（有沉水植物）和东龙港（无沉水植物）2条河流,利用扩散模型法对其水体CO₂、CH₄、N₂O释放通量进行24 h连续监测,并进行对比分析。结果表明：2条河流除盛家湾水体在16:00表现为CO₂吸收外,其余监测时间内3种气体均呈过饱和状态,表现为向大气释放温室气体,24 h内比较,有沉水植物的盛家湾可减少89%的温室气体释放。将气体释放通量与环境因子进行相关性分析发现,盛家湾水体CO₂释放通量与水温、pH、溶解氧浓度呈显著负相关,与氧化还原电位呈显著正相关,N₂O释放通量与水温、pH、溶解氧浓度呈显著正相关,与氧化还原电位呈显著负相关;东龙港水体CO₂释放通量与水温呈显著正相关,CH₄释放通量与水温、溶解氧浓度呈显著正相关,N₂O释放通量与水温呈显著正相关。

     

分层异重流对香溪河浮游植物叶绿素a空间分布的影响

基于三峡水库香溪河库湾汛期（2017年8月4—10日）水动力、气象和藻类漂移监测数据,运用数理统计方法,分析汛期香溪河浮游植物叶绿素a（Chla）浓度空间分布特征及其影响因素,探究分层异重流背景下藻类的水平输移和垂向掺混作用过程。结果表明：1)汛期香溪河库湾水动力具有明显的分层异重流特性,监测期间雷诺数均大于4 000,水体呈现紊流状态,对藻类的运动输移产生水平输运和垂向掺混2种影响。2)表层藻类水平漂移速度受到风速和水流流速的影响,响应关系式为V_藻=0.035V_风+0.461V_水+0.034 (R²=0.917,P<0.01)。3)分层异重流对高浓度藻细胞库湾原水的稀释作用和环流对高浓度藻细胞的携带作用,导致水柱Chla总浓度呈直线下降趋势,此时干流水体从中上层倒灌进库湾,上游来水以底部顺坡异重流方式流向河口,在中上游相遇形成环流,在库湾中部倒灌水体一分为二,分别从底部和表层输出库湾,Chla浓度分布特征为表层>底层>中层;当倒灌水体与库湾原水形成环流并从底部输出库湾时,Chla浓度分布特征为表层>中层>底层或者中层>底层>表层。因此,Chla浓度的水平分布主要受到风速和异重流的水平流速的影响,而垂向分布受到异重流所形成的水体循环模式的影响。     

An Adaptive‐Management Framework for Optimal Control of Hiking Near Golden Eagle Nests in Denali National Park

Abstract: Unintended effects of recreational activities in protected areas are of growing concern. We used an adaptive‐management framework to develop guidelines for optimally managing hiking activities to maintain desired levels of territory occupancy and reproductive success of Golden Eagles (Aquila chrysaetos) in Denali National Park (Alaska, U.S.A.). The management decision was to restrict human access (hikers) to particular nesting territories to reduce disturbance. The management objective was to minimize restrictions on hikers while maintaining reproductive performance of eagles above some specified level. We based our decision analysis on predictive models of site occupancy of eagles developed using a combination of expert opinion and data collected from 93 eagle territories over 20 years. The best predictive model showed that restricting human access to eagle territories had little effect on occupancy dynamics. However, when considering important sources of uncertainty in the models, including environmental stochasticity, imperfect detection of hares on which eagles prey, and model uncertainty, restricting access of territories to hikers improved eagle reproduction substantially. An adaptive management framework such as ours may help reduce uncertainty of the effects of hiking activities on Golden Eagles.     

Projected Climate Impacts for the Amphibians of the Western Hemisphere

Abstract: Given their physiological requirements, limited dispersal abilities, and hydrologically sensitive habitats, amphibians are likely to be highly sensitive to future climatic changes. We used three approaches to map areas in the western hemisphere where amphibians are particularly likely to be affected by climate change. First, we used bioclimatic models to project potential climate‐driven shifts in the distribution of 413 amphibian species based on 20 climate simulations for 2071–2100. We summarized these projections to produce estimates of species turnover. Second, we mapped the distribution of 1099 species with restricted geographic ranges. Finally, using the 20 future climate‐change simulations, we mapped areas that were consistently projected to receive less seasonal precipitation in the coming century and thus were likely to have altered microclimates and local hydrologies. Species turnover was projected to be highest in the Andes Mountains and parts of Central America and Mexico, where, on average, turnover rates exceeded 60% under the lower of two emissions scenarios. Many of the restricted‐range species not included in our range‐shift analyses were concentrated in parts of the Andes and Central America and in Brazil's Atlantic Forest. Much of Central America, southwestern North America, and parts of South America were consistently projected to experience decreased precipitation by the end of the century. Combining the results of the three analyses highlighted several areas in which amphibians are likely to be significantly affected by climate change for multiple reasons. Portions of southern Central America were simultaneously projected to experience high species turnover, have many additional restricted‐range species, and were consistently projected to receive less precipitation. Together, our three analyses form one potential assessment of the geographic vulnerability of amphibians to climate change and as such provide broad‐scale guidance for directing conservation efforts.     

Sorption‐desorption kinetics of some organochlorine insecticides in silt‐water suspensions

Kinetic (batch) sorption and desorption experiments for some organochlorine insecticides in silt‐water suspensions are described. The effect of possible experimental artifacts on the results is examined. The influence of the silt/water ratio on the linear sorption coefficient and on the “nonextractable”; solute fraction is determined. The sorption process is described in terms of some kinetic models.     

Role of competition in phytoplankton population for the occurrence and control of plankton bloom in the presence of environmental fluctuations

Termination of harmful algal blooms (HABs) and coexistence of phytoplankton–zooplankton populations are of great importance to human health, ecosystem, environment, tourism and fisheries. In this paper, we propose a three component model consisting of non-toxic phytoplankton (NTP), toxin producing phytoplankton (TPP) and zooplankton (Z). The growth of zooplankton species is assume to reduce due to toxic chemicals released by TPP population. We have extended the model proposed by Chattopadhyay et al. [Chattopadhyay, J., Sarkar, R.R., Pal, S., 2004. Mathematical modelling of harmful algal blooms supported by experimental findings. Ecol. Comp. 1, 225–235] by including competition terms between TPP and NTP. We observe the effect of competition factors both in the presence and absence of the environmental fluctuation. From our field as well as model analysis we observe that competition helps in the coexistence of the species, but if the effect of competition is very high on the TPP population, it results in planktonic bloom. It is shown that the coexistence equilibrium loses its stability when the competition coefficient crosses a critical value and resulting Hopf-bifurcation around the positive equilibrium depicting oscillations phenomena of the populations.     

对熏烟扩散模式应用的探讨

工程上应用的大气污染物扩散模式中 ,熏烟模式由于其非定常性而与其他扩散模式有很大的区别。正确处理模式中各参数及变量的相互关系才能客观地反映污染物对环境影响的结果。本研究通过对熏烟模式的非定常性和各参数、变量相互关系的分析 ,提出了正确使用该模式的方法