长江口两种仔稚鱼网具的采集效率比较

为获得更为准确的数据,提高对长江口鱼类早期资源评估的准确度,本研究同时采用方形网(网口为1.0 m×2.0 m,网目1.0 mm,网衣长5.5 m)和标准网(网口为直径0.8 m圆形,网目0.5 mm,网衣长3.5 m)于2014年4—7月在长江口邻近海域采集仔稚鱼样本,分析比较这2种网具所采集仔稚鱼种类和数量差异,从而选择更适宜采集长江口水域仔稚鱼的采样网具。结果表明:1方形网采集到51种仔稚鱼,多于标准网的37种,两种网具的共有种类有34种,主要优势种组成没有明显差异;24月,前弯曲期仔鱼较多,它们个体小,容易从网眼滤出,导致网目较小的标准网的样品平均密度高于方形网;35—7月,方形网的样本平均密度高于标准网,但样本中仔稚鱼个体发育阶段组成有明显不同。标准网样本中前弯曲期仔鱼占多数,体形为细长形的日本鳀和鳅虎鱼的前弯曲期仔鱼平均密度高于方形网;方形网样品中后弯曲期仔鱼占优势,小黄鱼、日本鳀和鳅虎鱼等优势种的后弯曲期仔鱼平均密度均高于标准网。总体而言,方形网所采集仔稚鱼种类和数量的效果优于标准网;对于细长体形种类(如日本鳀),需结合不同网具以便采集到全部发育阶段个体,而体形较宽种类(如小黄鱼)可仅以方形网采集。     

基于GIS的雪崩对冰湖风险性评估——以喜马拉雅山科西河流域为例

雪崩是冰湖风险性评估的因子之一,借鉴欧美发展起来的雪崩模型,在冰湖溃决洪水频发的喜马拉雅山地区开展雪崩对冰湖风险性评估研究具有重要意义。基于ICIMOD IKONOS DEM和Landsat-TM数据,利用GIS方法提取了研究区雪崩形成的海拔、平面曲率、坡度和地表覆盖类型等估算因子,根据Av=(Al+Fy)×S×Rg模型估算了研究区潜在雪崩形成区域,并应用GIS方法和α-β模型估算了雪崩的传播路径。结果表明:潜在雪崩不易形成的"低"值多分布在谷底及地表覆盖类型为密林的山坡上,而"高"、"较高"值多分布在坡度为30°~50°、地表类型以裸岩或草地为主的山坡和冰川上,这些分布符合雪崩形成的客观实际;分析判断发现研究区内"高"值区域,也就是潜在雪崩形成区共有98处,其中有10处能够进入冰湖,对这些冰湖的稳定性造成风险,这意味着在分析研究区所有冰湖的溃决风险性时,只有受到潜在雪崩影响的9个冰湖需要考虑雪崩因素,其余冰湖在冰湖溃决诱因筛选中无需考虑雪崩因子。     

城市土地利用效益与城市化耦合协调发展研究——以武威市凉州区为例

土地利用效益和城市化的耦合关系对于土地紧缺的干旱区内陆河流域绿洲城市的发展至关重要。以武威市凉州区为例,利用耦合协调度模型、灰色关联分析模型等分析其城市土地利用效益与城市化耦合协调发展关系。结果表明:2002—2012年,武威市凉州区土地利用的社会效益、经济效益和生态效益以及人口城市化、经济城市化、社会城市化、空间城市化和生活方式城市化指数均呈现明显的增加趋势。研究区土地利用效益值、城市化指数以及城市土地利用效益和城市化的综合评价指数呈现出线性递增的特征,且土地利用效益值增长速率快于城市化指数。土地利用效益和城市化的耦合协调系数从0.273 6提高至0.907 0,耦合协调状态由中度失调逐渐转为优质协调,耦合协调阶段可分为失调衰退—过渡—协调发展3个时期。城市土地利用效益和城市化发展之间存在相互驱动关系,即土地利用的经济效益对城市化产生的驱动影响较显著,城市化则主要从社会(人口)因素和经济因素两方面对土地利用效益产生驱动影响。研究结果对石羊河流域绿洲城市乃至干旱区绿洲城市的发展有一定的借鉴意义。     

Comparison of three evapotranspiration models with eddy covariance measurements for a Populus euphratica Oliv. forest in an arid region of northwestern China

The accurate estimation of evapotranspiration(ET) in arid regions is important for improving the water use efficiency of vegetation. Based on successive observations from May to October of 2014, we estimated the ET of a Populus euphratica Oliv. forest during the growing season in an extremely arid region using the PM(Penman-Monteith), SW(Shuttleworth-Wallace) and SSW(an improved canopy transpiration model) models. Estimated ET values were compared with those of the eddy covariance measurements. Results indicated that the actual ET of the P. euphratica forest was always overestimated by the PM model. The accuracy of the SW model was higher than that of the PM model. However, some data were not easily obtained because of the complicated structure of the SW model. The newly proposed SSW model gave the most accurate ET values, and its accuracy was higher at hourly than at daily time scale. In conclusion, the SSW model is more suitable for sparse vegetation system at large scales in extremely arid regions.     

Concentrations and isotopic characteristics of atmospheric reactive nitrogen around typical sources in Beijing,China

With rapid economic growth in China,anthropogenic reactive nitrogen(Nr) emissions have more than doubled over the last two or three decades.Atmospheric Nr pollution is an environmental concern in China especially in megacities such as Beijing.In order to identify the impact of emission sources on atmospheric Nr pollution,we measured atmospheric Nr concentrations and their isotopic composition(δ~(15)N) dynamics at three typical sites:landfill,pig farm and road traffic sites in Beijing from April 2010 to March 2011.Passive samplers were used for monitoring ammonia(NH_3) and nitrogen dioxide(NO_2),two major Nr species,while their δ~(15)N values were measured by a diffusion method combined with mass spectrometer approach.The raw water pool of the landfill and fattening house of the pig farm were important NH_3 sources with mean NH_3 concentrations being 2,829 and 2,369 μg/m~3,respectively,while the road traffic site was a minor NH_3 source(10.6 μg/m~3).NH_3 concentrations at sites besides the landfill and roads were high in summer and low in winter due to the annual variation of temperature and the change of emission source intensity.In contrast,the NH_3 concentrations inside the pig farm house were high in winter and low in summer,for the barn windows were open in summer and closed in winter.The mean NO_2 concentrations were 89.8,32.9 and 23.0 μg/m~3 at the road traffic,the landfill and pig farm sites,respectively.Due to vehicle fuel combustion,NO_2 concentration at the road traffic was the highest among the three sources,and the road traffic was a main NO_2 emission source.PM10,p NH4+ and p NO3– concentrations in particulate matter were higher in summer than in winter(except PM10 for the pig farm).The δ~(15)NH_3 values ranged from –19.14‰ to 7.82‰,with an average of –0.05‰ for the landfill site,and the lowest values were observed in June and July.The δ~(15)NH_3 values for the pig farm site ranged from –29.78‰ to –14.05‰ with an average of –24.51‰,and the δ~(15)NH_3 values were more negative in summer than in the other seasons.The δ~(15)NO_2 values were –9.63‰ to 7.04‰ with an average of –3.72‰ for the road traffic site.The δ~(15)NO_2 values were more negative in summer than those in the other seasons.The different δ~(15)N values for the various Nr species in different sources may serve as important indicators for identifying atmospheric Nr sources in megacities.The results may also provide the theoretical basis for research on the atmospheric N deposition and its sources.     

基于参数移植法的SWAT模型模拟嘉陵江无资料地区径流

该文选用嘉陵江中游9个中小流域,基于参数移植方法(距离相近法、属性相似法、综合相似法)探求分布式水文模型SWAT在嘉陵江中游无资料地区径流模拟的适用性。3个有资料试验流域模拟结果显示,参数移植法的模拟精度NS、R2平均值大于0.8,径流模拟精度较好,表明基于参数移植法的SWAT模型在研究区域具有一定的适用性,同时综合相似法(0.66NS0.93)的径流模拟结果优于距离相近法(0.65NS0.93)和属性相似法(0.65NS0.92),另研究表明参证流域个数对参数移植的结果有较大影响,多个参证流域参数移植效果消除单个参证流域参数移植结果的不确定性。     

黄河三角洲芦苇湿地不同水期土壤-植被重金属分布特征

ICP-AES法研究了黄河三角洲湿地平水期(4月)、丰水期(8月)和枯水期(10月)土壤和植被重金属(Hg,Cu,Zn,Pb,Cd和Cr)含量分布特征,并分析了土壤和植被重金属含量的关系。结果表明:(1)黄河三角洲芦苇湿地表土和底泥Hg,Cu,Zn平均含量变化呈递减趋势,依次表现出:平水期丰水期枯水期,不同时期土壤重金属Hg,Cu,Zn含量均表现为表土底泥;黄河三角洲芦苇湿地表土和底泥Pb,Cd和Cr平均含量变化呈递增趋势,依次表现出:枯水期丰水期平水期,并且不同时期土壤重金属Pb,Cd和Cr含量均表现为底泥表土,局部有所波动,综合分析可知,黄河三角洲芦苇湿地平水期的Hg,Cu,Zn污染最严重,枯水期Pb,Cd和Cr污染最严重;(2)黄河三角洲芦苇湿地表土重金属Hg,Cu,Zn含量高于底泥,表土重金属Pb,Cd和Cr含量低于底泥;(3)黄河三角洲芦苇湿地植被重金属Hg,Cu,Zn,Pb,Cd和Cr含量均显著高于土壤(p0.05),说明植被的吸收作用在土壤重金属污染中起着关键作用;(4)主成分分析表明黄河三角洲芦苇湿地土壤中Hg和Zn含量、植被中Pb和Cd的含量变化是黄河三角洲芦苇湿地的重金属污染主要影响因子;相关性分析表明,植被体内的重金属含量主要来自和依赖于土壤重金属含量,同时植被对于土壤各重金属的吸收也保持一定的独立性。     

安徽省淮河流域湿地土壤养分流失及水质动态研究

以淮河流域(安徽段)湿地为研究区域,连续3a(2012—2014年)在野外调查和室内分析的基础上,采用定点实地调查、土壤和水质采样相结合的方法,研究了不同水期(平水期、丰水期和枯水期)淮河流域湿地土壤养分流失、水质动态及湿地植被多样性特征,并运用冗余分析(RDA)和偏相关分析手段揭示不同水期淮河流域湿地植被多样性与环境因子之间的关系。结果表明:(1)淮河流域湿地植被Shannon-Wiener多样性指数(H)、Pielou均匀度指数(J_P)、Margalef种类丰富度指数(d_(Ma))在丰水期达到最高,平水期和枯水期较低,基本表现为丰水期枯水期平水期,Simpson优势度指数(D)基本表现为平水期枯水期丰水期。(2)不同水期土壤pH、电导率、全盐和总孔隙度在0—40cm剖面上变化趋势基本一致,不同水期土壤pH随土层深度的增加而增加,电导率和全盐含量呈先降低后增加趋势,土壤总孔隙度呈降低趋势。(3)随着水期的变化,土壤DP、K~+、SEP和SEK呈增加趋势,在枯水期达到峰值,平水期最低,基本表现为枯水期丰水期平水期,土壤DP、K~+和SEK增加幅度逐渐增加,而土壤SEP增加幅度逐渐减小,以SEK含量波动较大。(4)水温、TN、TP、BOD5和CODCr呈一致的变化规律,随水期的变化呈先增加后降低趋势,透明度呈"V"字形变化规律,基本表现为平水期枯水期丰水期。(5)偏相关分析显示,不同水期淮河流域湿地植被多样性均与透明度呈极显著的负相关(P0.01),透明度能够反映出淮河湿地植被多样性及水质状况,影响平水期和枯水期植被多样性主要因子为BOD5浓度和CODCr浓度,影响丰水期植被多样性主要因子为TN浓度和TP浓度。     

白龙江上游5种典型灌木林枯落物蓄积量及持水特性

采用野外实地观测与室内浸水法,对白龙江上游5种典型灌木林(荚蒾、甘肃柳、中华柳、箭竹、绣线菊)林地枯落物的蓄积量、持水量、持水率和吸水速率进行了研究。结果表明:5种典型灌木林林地枯落物蓄积量大小依次为箭竹林甘肃柳林荚蒾林中华柳林绣线菊林。5种灌丛类型枯落物半分解层的持水量均高于未分解层,中华柳未分解层持水量最高,箭竹半分解层持水量最高,绣线菊未分解层和半分解层持水量都是最小,整个枯落层最大持水量大小为中华柳箭竹荚蒾甘肃柳绣线菊;5种典型灌丛林不同分解程度枯落物的持水量与浸水时间存在对数关系,其吸水速率与浸水时间呈幂函数关系。     

模拟降雨入渗对岷江流域红壤坡面产流产沙的影响

采用室内模拟降雨研究了不同降雨强度和坡度对岷江流域红壤坡面降雨入渗、产流产沙的影响。结果表明:在不同降雨强度下,随坡度的增加,初始产流时间趋于提前;随降雨强度的增大,产流时间提前,降雨强度对初始产沙时间的影响大于坡度变化的影响。在同一坡度条件下,径流强度随降雨强度的增加而增加,平均入渗率随降雨强度的增加表现为先增大后减小的趋势。50mm/h降雨强度下,径流强度和坡面平均入渗率在降雨后20min开始趋于稳定;75mm/h降雨强度下,径流强度和坡面平均入渗率在降雨后15min开始趋于稳定;100mm/h降雨强度下,径流强度和坡面平均入渗率在降雨后10 min开始趋于稳定,径流强度和平均入渗率趋于稳定的时间均随雨强的增大而明显提前,各个时刻的径流强度和入渗率的稳定值在降雨过程中并不稳定,表现为随降雨强度和坡度的增大,波动愈剧烈。坡面产沙量随坡度和降雨强度的增大而增大,当坡度由5°增大到10°时,产沙量急剧增加;当坡度由10°增加到30°时,产沙量增速趋缓,侵蚀产沙量没有出现临界坡度。坡面产流强度和入渗率随时间的变化关系分别服从幂函数和对数函数规律,不同降雨强度下的径流深和产沙量也呈现出显著的正线性关系。