亚热带典型流域C、N沉降季节变化特征及其耦合输出过程

大气湿沉降是流域生态系统水体中碳氮的重要来源,对生态系统的健康及稳定性有很大的影响。通过对江西千烟洲典型亚热带流域降雨过程的碳、氮湿沉降和径流过程的季节性动态特征进行监测分析,探讨流域沉降、径流输出的C、N耦合及平衡关系。结果表明:千烟洲香溪流域降雨径流中碳氮浓度明显低于雨水,流域大气降水中DOC浓度和TN浓度呈极显著正相关关系。香溪河流域常规水体C:N均值为2.81,远低于根据Redfield比率得出的适宜浮游生物生长的C:N(6.6左右),说明外源性N输入导致该流域水体环境处于N过量的状态,长期输出会提高下游鄱阳湖水系的营养化程度。降雨过程对流域碳输入输出平衡影响较小,对氮输入输出平衡的影响较大。流域湿沉降DOC年输入量为69.41 kg hm-2a-1,TN湿沉降通量为77.23 kg hm-2a-1,碳氮沉降水平受区域降雨量及空气污染情况控制。香溪流域生态系统截留的沉降TN占当地氮肥年均使用量的33.13%,大气降水对亚热带流域生态系统的大量营养物质输入不容忽视。     

亚热带典型流域C、N沉降季节变化特征及其耦合输出过程

大气湿沉降是流域生态系统水体中碳氮的重要来源,对生态系统的健康及稳定性有很大的影响。通过对江西千烟洲典型亚热带流域降雨过程的碳、氮湿沉降和径流过程的季节性动态特征进行监测分析,探讨流域沉降、径流输出的C、N耦合及平衡关系。结果表明:千烟洲香溪流域降雨径流中碳氮浓度明显低于雨水,流域大气降水中DOC浓度和TN浓度呈极显著正相关关系。香溪河流域常规水体C∶N均值为2.81,远低于根据Redfield比率得出的适宜浮游生物生长的C∶N(6.6左右),说明外源性N输入导致该流域水体环境处于N过量的状态,长期输出会提高下游鄱阳湖水系的营养化程度。降雨过程对流域碳输入输出平衡影响较小,对氮输入输出平衡的影响较大。流域湿沉降DOC年输入量为69.41 kg hm~(-2)a~(-1),TN湿沉降通量为77.23 kg hm~(-2)a~(-1),碳氮沉降水平受区域降雨量及空气污染情况控制。香溪流域生态系统截留的沉降TN占当地氮肥年均使用量的33.13%,大气降水对亚热带流域生态系统的大量营养物质输入不容忽视。     

土地利用方式和社会经济对大伙房水库上游河流水质空间异质性的影响

根据2012 年8-9 月大伙房水库上游河流水体采样数据, 利用GIS 技术和地统计学方法, 分析了水质指标TN、TP、NH4⁺-N、COD_cr、BOD₅、pH、DO 和硅酸盐的空间变异特征, 并运用冗余分析的方法识别不同土地利用方式和社会经济状况对河流水质的影响。研究结果表明, 大伙房上游河流水质指标在空间分布上存在较大差异, 浑河(清原段)水质状况优于社河和苏子河, 靠近库区及库区周边小支流水质状况变差。TN、TP、NH4⁺-N、BOD₅ 和DO 的结构比大于75%, 说明其空间变化主要由随机性因素引起的, 硅酸盐结构比较小, 说明其受结构性因素影响显著。土地利用和社会经济的影响在大伙房上游水质空间分布占有重要份额, 其中土地利用能解释流域水质变异的16.2%, 具体表现为TN 和NH4⁺-N 含量与草地所占比例呈显著负相关, 与耕地所占比例呈显著正相关。TP、COD_cr、BOD₅、pH和硅酸盐含量与林地所占比例呈显著负相关, 与水域面积、建设用地和未利用地所占比例呈显著正相关。社会经济能解释大伙房上游水质变异的12.1%, 主要表现为水体TN、TP 含量与人均GDP 呈正相关, COD_cr 和BOD₅ 含量与工业比重呈正相关。因此, 合理配置土地类型、调控工业、农业和服务业等产业结构将在流域水生态管理中起到重要作用。     

广州流溪河氮磷浓度的季节变化和空间分布特征

广州市流溪河横跨北回归线,是典型的热带-亚热带过渡区河流。为了解该河流的营养盐分布特征,设置了20个采样点,于2015年2月至2017年2月进行季节性采样,共开展了8次水质监测,利用多元统计方法分析了主要营养盐(氮和磷)的季节动态和空间分布,并探讨影响营养盐时空分布的主要因素。结果表明:TN和TP的浓度范围分别为0.29~11.88 mg·L~(-1)与0.01~0.59 mg·L~(-1),TN浓度枯水期高于丰水期,总体上受降雨量的调节和河水稀释效应的影响; TP浓度丰水期高于枯水期,总体上受降雨量的调节及外源输入的影响; TN与TP在枯水期具有相似的季节变化特征,而在丰水期季节变化特征差异大;NO_3~--N和TN浓度的空间变化趋势相似,分为三个区段:流溪河水库上游的中值区河段,流溪河水库下游到街口大桥处的低值区河段和街口大桥下游的高值区河段,流溪河上游的两座大型水库对营养盐的滞留是导致其空间差异的主要因素之一; NH_4~+-N和TP浓度沿流域上游至下游总体上呈上升的趋势;三级河流氮和磷浓度显著高于一级河流和二级河流,河流氮、磷浓度与土地利用类型显著相关,建筑用地、裸露地和耕地所占比例的扩大会增加水体中TP、NH_4~+-N和NO_3~--N的浓度,而增加林地面积有助于水土保持和减少水体中氮、磷浓度。因此,上游水库的调节和下游城镇地区增加林地面积等方式对改善流溪河水质具有积极作用。     

厦门后溪水质与流域景观特征沿城乡梯度的变化分析

基于河流水质观测数据和Landsat 8影像数据,分析厦门后溪2013至2017年干季和湿季的水质时空变化特征,研究沿城乡梯度河流水质变化与流域景观特征的关系。结果表明:后溪上游(饮用水水源地水体)和下游(景观水体)溶解氧(DO)分别符合《地表水环境质量标准(GB3838—2002)》Ⅱ类标准和Ⅴ类标准,但是总氮(TN)和总磷(TP)有不同程度的超标,其中TN的超标比例较高。后溪上游土地利用类型中70%以上为林地,具有涵养水源、保护水质的作用;下游建设用地和耕地比重增加,TN、TP和叶绿素a (Chl a)显著高于上游。耕地和建设用地是提高TN、TP和Chl a等水质参数的主要土地利用类型,斑块密度、香农多样性指数和源汇景观指数与各水质指标也显著相关。冗余分析表明,流域景观特征可解释70%以上水质变化,对TN和TP的影响在湿季更大,而对Chl a的影响在干季较大。土地利用组成、配置、距离、高程和坡度对流域水质均有较大影响,其中土地利用组成对Chl a的影响较大,而景观指数则对TN和TP的影响较大。因此,在流域尺度加强土地利用的规划与综合管理,通过减少和控制地表径流面源污染的途径在一定程度上可降低人类活动对水质的不良影响。     

海河流域水体沉积物碳、氮、磷分布与污染评价

从全流域尺度上研究海河流域水体沉积物碳、氮、磷元素含量与分布特征,对研究海河流域水环境污染现状具有重要意义.本研究采集海河流域河流与水库163个表层沉积物(0～10 cm)样品,测定沉积物有机碳(TOC)、总氮(TN)、总磷(TP)的含量,运用有机指数与有机氮方法评价沉积物污染状况.结果表明: 海河流域沉积物TOC、TN、TP含量具有较大的空间异质性,下游平原区明显高于山区,北四河下游平原、黑龙港及运东平原含量较高,永定河山区、北三河山区、滦河流域含量相对较低,河流沉积物TOC含量显著高于水库沉积物,而TN、TP含量与水库沉积物没有显著差异.TN与TOC、TP含量呈显著正相关(r=0.704,P<0.01;r=0.250,P<0.01).全流域有机指数总体属于“较清洁”水平,北四河下游平原总体已接近有机污染水平.全流域有机氮总体处在“尚清洁”水平,北四河下游平原、黑龙港及运东平原流域存在有机氮污染.海河流域河流、水库沉积物具有相似的污染强度.沉积物C/N平均值为12.71,表明TOC多来源于藻类等浮游动植物,其次是高等植物,水库C/N值比河流高,陆源物质输入对水库沉积物TOC的贡献比对河流大.     

巢湖叶绿素a浓度的时空分布及其与氮、磷浓度关系

基于巢湖水体2002~2007年水质监测资料,对叶绿素a浓度的分布、动态及与TN、TP的关系进行了统计分析。巢湖叶绿素a浓度与TN、TP的浓度分布存在明显的空间差异,西半湖叶绿素a浓度全年高于20μg/L,TN为1.94~3.84mg/L,TP为0.20~0.42mg/L;东半湖叶绿素a浓度全年小于5.5μg/L,TN为0.95~1.83mg/L,TP为0.08~0.14mg/L。在东半湖,叶绿素a含量与TN呈不明显的正线性关系,当TP浓度较低时,叶绿素a随TP的增加小幅上升,但是当TP>0.15mg/L时,叶绿素a随TP的增加而明显上升;在西半湖,当水体TN<5.8mg/L或者TP<2.0mg/L时,叶绿素a含量与TN、TP关系为正线性关系,当TN在5.8~9.4mg/L或者TP介于0.2~0.3mg/L间时,叶绿素a含量与TN、TP关系为不显著的负线性关系,当TP浓度>0.3mg/L时,叶绿素a含量与TP关系又为正线性关系。西半湖叶绿素a浓度的变化可能是藻类生物活动与沉积物及水体中营养盐的相互作用结果。在治理巢湖富营养化时,应优先控制西半湖的磷元素。     

浑河河岸带六种草本植物氮、磷含量特征

通过实地采样方法,测定了大伙房水库上游浑河河岸带水蒿(Artemisia selengensis)、狼牙委陵菜(Potentilla cryptotaeniae)、水金凤(Impatiens noli-tangere)、茵陈蒿(Artemisia capillaries)、金盏银盘(Bidens biternata)、桃叶蓼(Polygonum persicaria)6种草本植物在7、8和9月根、茎和叶的总氮(TN)、总磷(TP)含量.结果表明:浑河上游6种草本植物TN含量为5.10～45.06 mg· g-1,TP含量为1.60～18.01 mg·g-1,氮/磷比平均值为2.68,范围0.92 ～6.14,显示出该地区P过剩;不同植物之间、同种植物不同器官中的TN、TP含量有显著性差异.综合考虑,水金凤中TN、TP含量高于其他5种植物,可以作为以水体修复为目的的河岸带植被恢复的备选植物.     

富营养水体中总氮与总磷比对苦草生长的影响

在室外受控实验条件下,研究了富营养水体中不同氮磷比(TN/TP)(12.5∶1、25∶1、50∶1)对苦草(Vallisneria spiralis)生长的影响.结果表明:当TN/TP为25∶1时,苦草的生长状态最好,苦草生物量的增长率最大,分别高于TN/TP为12.5∶1和50∶1时的54%和31%;当TN/TP为25∶1时,附着生物尤其是附着藻类的生长状态最差,对苦草生长的不利影响最小;可见,富营养水体中适宜于苦草生长的TN/TP为25∶1;TN/TP为25∶1这一比例的应用具有相对性,当水体营养浓度低于限制水平时,该比例适用,如果水体中营养盐浓度超过限制水平时,该比例则不适用.     

二球悬铃木凋落叶分解初期对水体总氮和总磷的影响研究

为研究凋落叶在小型水体分解初期对水体N、P含量变化的影响, 在实验室内模拟了秋季二球悬铃木(Platanus acerifolia)凋落叶在水体中短期分解的过程, 研究了不同质量凋落叶分解对水体总氮(TN)、总磷(TP)的影响。结果表明: 二球悬铃木凋落叶中磷(P)在10 h内淋溶作用明显, 水体TP含量在10 h内持续上升; 而凋落叶质量不同, 氮(N)快速淋溶时间不同, 1-2 g凋落叶发生在6 h内, 3 g凋落叶在24 h内持续释放N。二球悬铃木凋落叶在水体分解4 d过程中, 均表现为N、P的整体释放, 但N、P变化特征不同, 1-2 g凋落叶水体中TN峰值出现在48 h, 3 g凋落叶峰值在72 h; 而TP峰值分别为10 h(1 g)、72 h(2 g)和96 h(3 g)。随凋落叶质量增加, 水体TN、TP含量升高且差异显著, 1 g、2 g和3 g凋落叶水体中的TN含量平均值分别为0.217 mg·L–1、0.475 mg·L-1和0.644 mg·L–1, TP含量平均值分别为0.132 mg·L–1、0.192 mg·L–1和0.302 mg·L–1。二球悬铃木凋落叶水体TP显著高于白蜡凋落叶水体TP, TN波动变化但整体上也高于白蜡落叶水体。      

密云水库的浮游植物群落结构与密度

 1998年的调查研究显示,密云水库库区水体的浮游植物群落为硅藻(Bacillariophyta)—绿藻(Chlorophyta)型,细胞密度为358.76×104·L-1。湖泊的营养特征为浮游植物响应型。1988～1998年库区水体总氮增长48.7％,总磷增长31.2％,浮游植物细胞密度增长41.7％,库区水体已为中营养,并出现了富营养型浮游植物指示种类,例如斜生栅藻(Scenedesmus obliquus(Turp)．Kütz．),铜绿微囊藻(Microcystis aeruginosa Kütz．),湖泊色球藻(Chroococcus limneticus Lemm．)。水体向富营养化发展趋势明显。应加强水环境保护,增加密云水库流域植被覆盖度,净化、涵养水源,以保证密云水库向北京市供水的质量和数量。     

Nutrient leaching and settling rate characteristics of the faeces of Atlantic salmon (Salmo salar L.) and the implications for modelling of solid waste dispersion

The present study determined the settling velocity and leaching rates of carbon and nitrogen from the faecal matter of Atlantic salmon (Salmo salar L.) fed two commercial diets, high energy (HE) and standard, in three separate experiments (December, March and May) which coincided with winter, spring and summer. Faecal settling velocities for individual samples were in the range of 3.7–9.2 cm s^?1. There were significant differences (P < 0.05) in settling velocities among the three experiments, with lowest velocities measured in faecal samples collected in winter and highest velocities measured in samples collected in summer. There were no significant differences (P > 0.05) in faecal settling velocity among fish fed the different diet types. Faecal nutrient content in the different treatment groups prior to leaching was 269–318 mg g^?1 for carbon and 28–37 mg g^?1 for nitrogen. Both carbon and nitrogen contents were higher in faeces from fish fed the standard diet than in fish fed the HE diet (P < 0.05). Thus the use of HE diets resulted in a 12% reduction in faecal carbon content and an 8% reduction in faecal nitrogen when compared with standard diets. There were no consistent differences in faecal carbon among samples collected during the three experiments; however, significant differences in faecal nitrogen content were detected in samples collected on the three different occasions. Leaching of faecal carbon and faecal nitrogen ranged between 4–14% and 9–16% of the original amount, respectively, after 2.5‐min immersion in sea water, although there was no further significant (P > 0.05) leaching after this time. No significant difference in nutrient leaching rate was found in faeces of fish fed HE and standard diets, and no significant differences in leaching rates were apparent among samples collected at different times of the year. These values suggest there may be an overestimation by dispersion models of the amount of nutrients entering seabed sediments. The amount of nutrients leaching from faeces may also have an important role in nutrient flux in the water column.     

Nutrient release from swamp water,Cyperus papyrus L. organs and swamp sediments

Nitrogen and phosphorus releases from swamp water,Cyperus papyrus plant organs and papyrus swamp sediments were investigated over five weeks. The release of nutrients by dissolution of decomposing organic matter was very important for the swamp water under the prevailing anaerobic conditions. Large amounts of nutrients were found in the incubation water with plant organs and sediments within the first 48 hours. Leaching of the nutrients from the plant organs and sediment caused high initial values. Subsequently decomposition of the organic material caused slight changes in the nutrient levels in the water. Probably denitrification played a role in the nitrogen dynamics, while phosphorus was mineralized.     

Nutrient limitation of phytoplankton in a central Arizona reservoir

The influence of added nutrients nitrogen, phosphorus and carbon on the phytoplankton of a small recreational reservoir in central Arizona was investigated during the summer, 1974. Polyethylene bags were used to isolate lake water and the natural populations for the addition of nitrogen, phosphorus and carbon individually and in combination. A large increase in phytoplankton numbers, extractable chlorophyll, pH and dissolved oxygen occurred only in bags to which both nitrogen and phosphorus were added, suggesting that both nitrogen and phosphorus levels were limiting to the primary producers. Little alteration in species composition resulted from the addition of the above nutrients.     

东太湖四角菱（Trapa quadrispinosa）生长特性

通过室外受控实验,研究了在不同沉积物类型及不同水体营养水平条件下东太湖四角菱的生长特性.结果表明:沉积物类型对菱的各项生长指标均有显著影响.在营养相对丰富的湖泥中,菱的相对生长率、同化根与吸收根的生物量以及株高增长率分别为相对贫瘠的岸泥的4.3、2.4、7.3、2.5倍,菱盘直径增长率在湖泥中为16.5%,在岸泥中则为负增长(-13.2%).水体营养盐浓度升高在一定程度上也促进了菱的生长,而且营养盐浓度(尤其是磷)升高对菱生长的促进作用在岸泥中要比在湖泥中显著得多.探讨了沉积物类型与水体营养水平对菱生长的作用机理,并认为水体富营养化的加剧及湖泊沼泽化所造成的氮、磷等营养物质在沉积物中的大量积累是东太湖菱种群迅速扩张的重要原因之一.     

Characteristics of nutrient release from sediments under different flow conditions

Contaminated sediments, as a secondary pollution source in rivers and lakes, are of critical importance to water quality. More and more attention thus has been paid to understand the release mechanisms of nutrients from river sediments, especially in estuary and water transfer areas. In this work, flume experiments were conducted to measure the release characteristics of total dissolved phosphorus (TDP) and nitrogen (TDN) from sediments collected from a river bed near Lake Tai under various flow conditions. The release of TDP and TDN was the most dramatic in the initial 30 min, then slowed down from 30 to 60 min, and finally achieved equilibria. Total amount of TDP and TDN released and their equilibrium concentrations were all significantly increased with the increase of flow rate, but slow down after a critical velocity was reached, which could be described as a Logarithmic relationship. A process-based mathematical model was established to describe the distribution of nutrients in the water columns and model simulations matched experimental data well. The re-suspension of sediments induced by flow rate higher than the threshold, is the dominant process affecting nutrient release from sediments.     

Transporting Nutrients from Sediments: Nitrogen and Carbon as Indicators to Measure Scavenging Ability of a Detritivorous Fish, Liza haematocheila

Synopsis The redlip mullet, Liza haematocheila, is a common species in polyculture as a scavenger in China. Feeding on detritus, redlip mullet transports nutrients from sediments up into the water column and converts them into forms that can be utilized by phytoplankton and affects the relative abundance of detritus and dissolved inorganic nutrients to phytoplankton, zooplankton and other fishes. We used nitrogen and carbon as the indicators in this study to measure the scavenging ability, which means intake of nitrogen or carbon by redlip mullet, and the loss of nutrients. Temperature and body weight significantly affected growth nitrogen, faecal nitrogen and faecal carbon. At a certain temperature, the proportion of growth nitrogen or growth carbon increased while the proportion of excretion nitrogen or respiration carbon decreased with increasing body weight.     

Nitrogen and phosphorus accumulation and cycling by Nymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae)

In 1980, the seasonal changes in nitrogen and phosphorus concentration of various plant parts of Nymphoides peltata (Gmel.) O. Kuntze, together with aspects of nitrogen and phosphorus cycling by this species were studied in an oxbow lake of the river Waal (The Netherlands). The nitrogen and phosphorus stores of the water, seston, sediment and macrophyte compartments were assessed each month.The underground Nymphoides structures had high nitrogen and phosphorus concentrations before and after the main growing season, while during summer the aboveground plant parts had high nutrient contents. Nymphoides peltata accumulated maximum amounts of nitrogen (334 mmol m⁻²) and phosphorus (56.6 mmol m⁻²) in July. The upper layers of the bottom appeared to be an enormous nutrient reservoir (94–99% of total) of which the largest part was not directly available to Nymphoides. Nutrient uptake from the sediments by N. peltata is suggested by the fact that the bottom and/or interstitial water of the sample station devoid of rooted macrophytes, contained higher concentrations of nitrogen and phosphorus than that of the Nymphoides stands. The annual flux of nutrients from Nymphoides to the detritus compartment was estimated to be ca. 1200 mmol nitrogen and 164 mmol phosphorus per m² of littoral. During breakdown of the detritus there was a relatively fast net conversion of organically bound nitrogen and phosphorus to inorganic forms, especially at higher temperatures.Nymphoides has the potential to function as an important nitrogen and phosphorus pump, which regenerates sediment nutrients.     

陕北黄土区生物结皮条件下土壤养分的积累及流失风险

分析了陕北黄土高原典型流域生物结皮的形成和发育对土壤养分的积累效应,同时对生物结皮条件下土壤养分的流失风险进行评价.结果表明：生物结皮生长发育后能够迅速增加结皮层及2 cm土层的养分含量,但对深层土壤影响较小;退耕0～20年间结皮层的养分含量与退耕年限之间的关系可用指数函数（y=a［b-exp(-cx)］）拟合,其中有机质、全氮和碱解氮在退耕20年间的增加速度变化不大,而全磷、速效磷和速效钾在退耕初期增加迅速,后期增加缓慢;自然发育生物结皮对土壤养分的年均净贡献量为：有机质50.15 g·m^-2、全氮1.95 g·m^-2、全磷0.44 g·m^-2、碱解氮164.33 mg·m^-2、速效磷9.64 mg·m^-2和速效钾126.21 mg·m^-2,人工培育条件下生物结皮发育更快,对养分尤其是速效养分的贡献速率更高;生物结皮条件下养分含量的提高增加了养分流失风险,尤其是养分随泥沙流失大幅度增加,生物结皮增加的养分中平均有39.06%随泥沙流失,仅有60.94%得以保留.总之,生物结皮可迅速、全面增加表层土壤养分,但同时会加大养分流失风险.尽管如此,土壤养分的净增加量仍相当可观,显示生物结皮具有较好的土壤养分积累效应.     

水动力条件下藻类动态模拟

藻类动态变化是其内部生理特征和外部驱动因素综合作用的结果。除了藻类自身生理因素及光、温度、营养盐等因素,水动力作用使底泥发生再悬浮所造成的营养盐的内源释放对藻类的影响也非常重要。1999年5月8日~6月24日在太湖湖泊生态系统研究站大型生态实验槽中进行了模拟水动力条件下的太湖藻类动态实验,并应用国外先进的PHREEQC软件从生物化学和生态动力学角度建立了藻类生态动力学模型。模型不仅考虑了氮循环及磷循环,还考虑了水动力条件引起的内源释放问题,根据2003年4月26~4月30日在河海大学环形水槽所做的底泥释放实验结果建立了水流和各形态氮磷营养盐释放的定量化关系。由于目前太湖的野外监测资料存在较明显的时空不一致性,模型参数率定的精度受到了较大影响。从室内模拟实验出发,通过对生态槽实验结果的模拟,确定和验证了模型的各参数值,计算结果显示模拟值能较好地拟合实验测量值,表明所建藻类生态动力学模型能较好地描述藻类及各种营养盐的动态变化,这对揭示藻类“水华”暴发机理有一定的意义。