大鹏湾中溶解态总氮和总磷的多年调查结果分析

依据2000—2010年每月1次的调查资料,简要描述和讨论大鹏湾海水中溶解态总氮（DTN）和溶解态总磷（DTP）质量浓度的空间分布和时间变化。结果表明由于受到香港和深圳陆源排放的影响,DTN和DTP质量浓度在吐露港和沙头角附近水域1年4季都较高。DTN和DTP的平均质量浓度分别为0.21和0.03 mg.L-1,比溶解态无机氮（DIN）和溶解态无机磷（DIP）的高1倍以上,表明大鹏湾海水中溶解态有机氮（DON）和溶解态有机磷（DOP）分别是DTN和DTP的主要赋存形态。平均DTN/DTP原子比〉16,反映了大鹏湾海水中磷可能是海洋浮游生物生长繁殖的限制因素。夏季,由于南海北部陆架低温、高盐和高营养盐底层水潜入湾内,底层DTN和DTP质量浓度明显高于其他季节。11年调查期间,DTN质量浓度的年际变化趋势平稳,DTP质量浓度的年际变化呈较明显的下降趋势,而DTN/DTP原子比的年际变化呈较明显的上升趋势。     

Hydrochemistry and dissolved nutrient flux of two small catchment rivers, south-western India

This paper deals with the water chemistry and dissolved nutrient flux of two small mountainous and heavily dammed rivers—Periyar and Chalakudy—of Kerala on the south-west coast of India. The lower reaches of these rivers are affected by sea-water ingression from the Arabian Sea during the non-monsoon season. Human interference through agriculture, urbanization, and industrialization in the lower and middle stretches of the river basins induces marked concentration variations in the hydro-chemical parameters. Except for N & P, all other chemical constituents exhibit high values during the non-monsoon season. Industrial contaminants in specific locations of the Periyar river reduce the pH to lower levels. Nutrients in the two rivers reveal marked seasonal and regional concentration variations. During the monsoon season, dissolved inorganic nitrogen (DIN) predominates over dissolved organic nitrogen (DON), but the reverse trend is observed during the non-monsoon season. The Periyar river shows higher average concentrations of DIN (monsoon 801 μg l^-1 and non-monsoon 292 μg l^-1) than Chalakudy river (monsoon 478 μg l^-1 and non-monsoon 130 μg l^-1). Dissolved inorganic phosphorus (DIP) has lower average values in the monsoon season (Periyar river, 38 μg l^-1; Chalakudy river, 42 μg l^-1) than dissolved organic phosphorus (DOP) values (Periyar river, 107 μg l^-1; Chalakudy, 62 μg l^-1). The rivers show a marked difference in nutrient flux due to its difference in water discharge/basin characteristics and point/non-point sources of contaminants. The flux rates of DIN, DIP, and DOP during the monsoon are higher than during the non-monsoon season, while those of dissolved silicon (DSi), dissolved Fe (DFe), and DON are lower. On average, the Periyar river discharges 4953 t y^-1 of DIN and 1626 t y^-1 of DON to the coastal waters, and the corres-ponding values of the Chalakudy river are 772 t y^-1 and 596 t y^-1. The Periyar and Chalakudy rivers discharge 245 t y^-1 and 70.8 t y^-1 of DIP, respectively. The total flux of DOP is considerably higher (Periyar river 703 t y^-1 and Chalakudy river 101 t y^-1). The discharge of DSi into the Periyar river (40 193 t y^-1) is nearly five times higher than that in the Chalakudy river (8275 t y^-1). The discharges of DFe through the Periyar and Chalakudy rivers are 257 t y^-1 and 36.7 t y^-1, respectively. To sum up, this study addresses the water quality and nutrient flux of two tropical rivers and discusses the impact of urbanization and industrialization on river-water quality.     

Pretreatment for dissolved organic nitrogen testing by gas stripping

ABSTRACT

Total dissolved nitrogen (TDN), including dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON), is of significant importance in aquatic systems due to its roles in numerous environmental processes, such as nutrients for agriculture activities, sources for lake and estuary eutrophication, and one of the major factors contributing to disinfection byproduct formation. The distribution and impact of DIN on these processes are relatively well-understood; however, information on DON is extremely limited, as there is no direct method for its quantification. DON is conventionally determined by subtracting DIN from TDN. However, significant errors may be introduced if DIN is the predominant species in samples with high concentrations of TDN. In order to deal with this challenge, pretreatment method for nitrogen gas stripping was investigated using 56 water samples collected from various ecosystems. The results indicated that after nitrogen gas stripping pretreatment, removal % of ammonia nitrogen (NH₃–N) was more than 87.5%, and the ratios of removal of NH₃–N/removal of TDN (β) were over 86.5% for most of 56 samples with high [NH₃–N], indicating a high efficiency for removal of NH₃–N, and that NH₃–N was the predominant nitrogen species removed for the samples with high [NH₃–N]. Therefore, nitrogen gas stripping is an appropriate pretreatment method for DON testing when NH₃–N is the dominant inorganic nitrogen species.     

Examining the coupling of carbon and nitrogen cycles in Appalachian streams: the role of dissolved organic nitrogen

Although regional and global models of nitrogen (N) cycling typically focus on nitrate, dissolved organic nitrogen (DON) is the dominant form of nitrogen export from many watersheds and thus the dominant form of dissolved N in many streams. Our understanding of the processes controlling DON export from temperate forests is poor. In pristine systems, where biological N limitation is common, N contained in recalcitrant organic matter (OM) can dominate watershed N losses. This recalcitrant OM often has moderately constrained carbon:nitrogen (C:N) molar ratios (approximately 25-55) and therefore, greater DON losses should be observed in sites where there is greater total dissolved organic carbon (DOC) loss. In regions where anthropogenic N pollution is high, it has been suggested that increased inorganic N availability can reduce biological demand for organic N and therefore increase watershed DON losses. This would result in a positive correlation between inorganic and organic N concentrations across sites with varying N availability. In four repeated synoptic surveys of stream water chemistry from forested watersheds along an N loading gradient in the southern Appalachians, we found surprisingly little correlation between DON and DOC concentrations. Further, we found that DON concentrations were always significantly correlated with watershed N loading and stream water [NO3-] but that the direction of this relationship was negative in three of the four surveys. The C:N molar ratio of dissolved organic matter (DOM) in streams draining watersheds with high N deposition was very high relative to other freshwaters. This finding, together with results from bioavailability assays in which we directly manipulated C and N availabilities, suggests that heterotrophic demand for labile C can increase as a result of dissolved inorganic N (DIN) loading, and that heterotrophs can preferentially remove N-rich molecules from DOM. These results are inconsistent with the two prevailing hypotheses that dominate interpretations of watershed DON loss. Therefore, we propose a new hypothesis, the indirect carbon control hypothesis, which recognizes that heterotrophic demand for N-rich DOM can keep stream water DON concentrations low when N is not limiting and heterotrophic demand for labile C is high.     

Plant diversity, CO2, and N influence inorganic and organic N leaching in grasslands

In nitrogen (N)-limited systems, the potential to sequester carbon depends on the balance between N inputs and losses as well as on how efficiently N is used, yet little is known about responses of these processes to changes in plant species richness, atmospheric CO2 concentration ([CO2]), and N deposition. We examined how plant species richness (1 or 16 species), elevated [CO2] (ambient or 560 ppm), and inorganic N addition (0 or 4 g x m(-2) x yr(-1)) affected ecosystem N losses, specifically leaching of dissolved inorganic N (DIN) and organic N (DON) in a grassland field experiment in Minnesota, USA. We observed greater DIN leaching below 60 cm soil depth in the monoculture plots (on average 1.8 and 3.1 g N x m(-2) x yr(-1) for ambient N and N-fertilized plots respectively) than in the 16-species plots (0.2 g N x m(-2) x yr(-1) for both ambient N and N-fertilized plots), particularly when inorganic N was added. Most likely, loss of complementary resource use and reduced biological N demand in the monoculture plots caused the increase in DIN leaching relative to the high-diversity plots. Elevated [CO2] reduced DIN concentrations under conditions when DIN concentrations were high (i.e., in N-fertilized and monoculture plots). Contrary to the results for DIN, DON leaching was greater in the 16-species plots than in the monoculture plots (on average 0.4 g N x m(-2) x yr(-1) in 16-species plots and 0.2 g N x m(-2) x yr(-1) in monoculture plots). In fact, DON dominated N leaching in the 16-species plots (64% of total N leaching as DON), suggesting that, even with high biological demand for N, substantial amounts of N can be lost as DON. We found no significant main effects of elevated [CO2] on DIN or DON leaching; however, elevated [CO2] reduced the positive effect of inorganic N addition on DON leaching, especially during the second year of observation. Our results suggest that plant species richness, elevated [CO2], and N deposition alter DIN loss primarily through changes in biological N demand. DON losses can be as large as DIN loss but are more sensitive to organic matter production and turnover.     

洞庭湖浮游植物增长的限制性营养元素研究

近20年水质监测资料表明,洞庭湖水体富营养化日趋严重。洞庭湖水体主要污染物为氮和磷,而营养盐赋存形态及其含量对浮游植物生长的影响在洞庭湖尚未见报道。2011年9月至2012年8月对洞庭湖浮游植物生物量及主要营养盐赋存形态与含量进行监测,同时利用藻类增长的生物学（NEB）评价方法对限制浮游植物增长的营养盐进行了研究,并分析了浮游植物生物量与各营养元素之间的相关性。结果表明：洞庭湖主要污染物总氮（TN）和总磷（TP）的年平均值分别为1.90 mg·L-1和0.093 mg·L-1,溶解态无机氮（DIN）平均占ρ（TN）比例为87%,溶解态总磷（DTP）平均占ρ（TP）比例为70%。洞庭湖水体中,DIN是TN的主要贡献者,且不同形态DIN的贡献大小依次为ρ（NO3--N）〉ρ（NH4＋-N）〉ρ（NO2--N）;磷形态组成中,TP主要以溶解反应性磷（SRP）存在。春季洞庭湖水体中ρ（TN）、ρ（TP）较高,这一结果可能源于春季面源污染。洞庭湖水体中ρ（Chla）与氮显著正相关,与磷显著负相关。NEB 实验结果表明氮对洞庭湖浮游植物生长有明显的促进作用,其幅度随氮浓度的增加而加强,而磷对浮游植物的生长影响不大,有时出现抑制作用,硝态氮与磷之间不存在交互作用。因此,氮可能是洞庭湖浮游植物增长的主要限制性营养因子,这一研究暗示在洞庭湖富营养化控制过程中应特别注重氮的控制。     

Nutrients uptake and growth of Ulva lactuca (Linnaeus, 1753) in grey mullet (Mugil cephalus) wastewater versus natural estuarine water

This study investigates the capability of Ulva lactuca to grow in an integrated system, aiming to optimise the needing of resources and to decrease the ecological impact of wastewater. The nutrients uptake and the growth of U. lactuca in Mugil cephalus wastewater (WW) were evaluated and compared with U. lactuca cultivated in estuarine water (EW). Fresh thalli of U. lactuca were cultivated for 10 days in 5?L cylindrical tanks, 3 replicates per treatment. The uptake of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP), as well as the biomass yield and specific growth rate of U. lactuca, were assessed every two days. At the end of the experiment, U. lactuca resulted in a higher assimilation of DIN in EW (95.7?±?0.3%, mean?±?SE) than in wastewater (68.7?±?1.0%) (p?80%), as well as in the biomass yield and specific growth rate. This study demonstrates the efficiency of U. lactuca in the assimilation of DIN and DIP from M. cephalus WW, contributing to reduce the release of dissolved inorganic nutrients in the natural environment.     

Effects of nitrogen and phosphorus enrichement on in vivo symbiotic zooxanthellae of Pocillopora damicornis

The reef coral Pocillopora damicornis (Linnaeus) was grown for 8 wk in four nutrient treatments: control, consisting of ambient, unfiltered Kaneohe Bay seawater [dissolved inorganic nitrogen (DIN, 1.0 M) and dissolved inorganic phosphate (DIP, 0.3 M)]; nitrogen enrichment (15 M DIN as ammonium); phosphorus enrichment (1.2 M DIP as inorganic phosphate); and 15 M DIN+1.2 M DIP. Analyses of zooxanthellae for C, N, P and chlorophyll a after the 8 wk experiment indicated that DIN enrichment increased the cellular chlorophyll a and excess nitrogen fraction of the algae, but did not affect C cell^-1. DIP enrichment decreased both C and P cell^-1, but the decrease was proportionally less for C cell^-1. the response of cellular P to both DIN and DIP enrichment appeared to be in the same direction and could not be explained as a primary effect of external nutrient enrichment. The observed response of cellular P might be a consequence of in situ CO₂ limitation. DIN enrichment could increase the CO₂ (aq) demand by increasing the net production per unit area. DIP enrichment could slow down calcification, thus decreasing the availability of CO₂ (aq) in the coral tissue.Hawaii Institute of Marine Biology Contribution No. 920     

Bioremediation of aquaculture wastewater from Mugil cephalus (Linnaeus, 1758) with different microalgae species

Current aquaculture practices have a detrimental impact on the environment, in particular due to the release of high concentration of nitrogen and phosphorus that can induce eutrophication. This study investigates and compares the capacity of three microalgae species Tetraselmis suecica, Isochrysis galbana and Dunaliella tertiolecta, in the bioremediation of grey mullet Mugil cephalus wastewater. The experiment was conducted in batch conditions for 7 days using completely mixed bubble column photobioreactors. After two days, T. suecica and D. tertiolecta were able to remove more than 90% of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP), whereas I. galbana removed only 32% and 79% of DIN and DIP, respectively. A higher biomass yield resulted for T. suecica (603?±?34?mg/L, mean?±?SE). This study confirms the potential to employ T. suecica in an Integrated Multi-Trophic Aquaculture system for bioremediation of wastewater and identifies D. tertiolecta as another valid candidate species. Moreover, these species can growth in unsterilized culture media, and this reduces energy consumption, costs and efforts.     

Land use change and nitrogen enrichment of a Rocky Mountain watershed.

Headwater ecosystems may have a limited threshold for retaining and removing nutrients delivered by certain types of land use. Nitrogen enrichment was studied in a Rocky Mountain watershed undergoing rapid expansion of population and residential development. Study sites were located along a 30-km transect from the headwaters of the Blue River to Lake Dillon, a major source of drinking water for Denver, Colorado. Ground water in residential areas with septic systems showed high concentrations of nitrate-N (4.96 +/- 1.22 mg/L, mean +/- SE), and approximately 40% of wells contained nitrate with delta15N values in the range of wastewater. Concentrations of dissolved inorganic nitrogen (DIN) in tributaries with residential development peaked during spring snowmelt as concentrations of DIN declined to below detection limits in undeveloped tributaries. Annual export of dissolved organic nitrogen (DON) was considerably lower in residential streams, suggesting a change in forms of N with development. The seasonal delta15N of algae in residential streams was intermediate between baseline values from undeveloped streams and stream algae grown on wastewater. Between 19% and 23% of the annual N export from developed tributaries was derived from septic systems, as estimated from the delta15N of algae. This range was similar to the amount of N export above background determined independently from mass-balance estimates. From a watershed perspective, total loading of N to the Blue River catchment from septic and municipal wastewater (2 kg x ha(-1) x yr(-1)) is currently less than the amount from background atmospheric sources (3 kg x ha(-1) x yr(-1)). Nonetheless, nitrate-N concentrations exceeded limits for safe drinking water in some groundwater wells (10 mg/L), residential streams showed elevated seasonal patterns of nitrate-N concentration and ratios of DIN to total dissolved phosphorus, and seasonal minimum concentrations of nitrate-N in Lake Dillon have increased exponentially to 80 microg/L over the last decade from an initial value near zero. Results suggest that isotopic ratios in autotrophs can be used to detect and quantify increases in N enrichment associated with land use change. The biotic capacity of headwater ecosystems to assimilate increases in inorganic N from residential development may be insufficient to prevent nitrogen enrichment over considerable distances and multiple aquatic ecosystems downstream.     

Automated procedure for determination of dissolved organic nitrogen and phosphorus in aquatic environments

A method is described for estimating dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in aquatic environments. The method is based on ultraviolet oxidation under successive acid and alkaline conditions, and uses continuous-flow techniques. A number of pure organic nitrogen compounds were tested in the concentration range 2 to 40 g-at Nl^-1. At the 10 g-at Nl^-1 level, recovery ranged from 60 to 100% in deionized water, and from 40 to 80% in seawater (30 S). In general, recovery decreased with increasing nitrogen concentration. For pure organic phosphorus compounds, recovery ranged from 73 to 100% at the 5 g-at Pl^-1 level. An application of the method to the surface water of a clay pond along the Atlantic coast of France for a period of 72 h under natural irradiance revealed very strong diel variations of dissolved organic nitrogen, but no significant trends for dissolved organic phosphorus.     

热带滨海区不同土地利用背景下土壤溶解性有机氮的组成与粒径分布特征

溶解态有机氮(DON)是土壤中活跃的氮库,其生态环境行为与它的化学组成和粒径分布密切相关。为评估热带滨海区不同土地利用方式对不同粒径中土壤溶解性有机氮组成特征的影响,从水稻田、橡胶园、菜园和果园采集土壤样品,通过一系列微滤和超滤(0.7,0.45,0.2,0.1μm,100,10,1 kDa)对土壤溶解性有机氮分级,并使用连续流动分析仪、三维荧光光谱和红外光谱研究了滤液中溶解态有机氮、无机氮的含量及荧光组分和有机官能团特征。结果表明,4种土地利用背景下土壤DON值的范围为5.25-10.88 mg·kg^-1,其大小顺序为水稻>菜园>果树>橡胶,且DON与溶解性总氮(DTN)的比值范围为26.08%-67.11%,其中橡胶土最高,水稻土最低;不同粒径下4种土地利用类型土壤DON主要集中在<100 kDa的粒径中,其值范围为4.85-9.48 mg·kg^-1,占全量的85.89%-92.41%。三维荧光光谱(3D-EEMs)及平行因子分析表明,4种土地利用背景下土壤DON含有两种类腐殖质组分及一种类蛋白质组分,且以类腐殖质组分为主,占比54.00%-77.67%;类蛋白组分对土地利用变化敏感,且随着粒径的减小,类蛋白组分占比增加,在<1 kDa组分中比例最高。红外光谱结果表明,4种土地利用背景下土壤DON主要在6个位置有相似的吸收峰,包含3410 cm^-1、1636 cm^-1、1402 cm^-1、1138-1035 cm^-1、673 cm^-1、602 cm^-1,不同土地利用背景下各吸收峰的透光度不同,强度最大的吸收来自游离的胺类N-H伸缩振动;水稻、菜园土壤DON芳香物质含量较高,结构较复杂。了解DON的组成与粒径分布对土地利用的响应,对进一步研究其生态环境行为具有重要意义。     

施肥对不同肥力春玉米田土壤溶解性有机质的影响

选取辽河灌区不同肥力水平春玉米（Zea mays ssp. mays L.）农田土壤为研究对象,通过连续3年田间定位试验,采用三维荧光光谱法分析了不同层次土壤溶解性有机质组分含量,研究施肥对不同肥力农田土壤溶解性有机质组分（DOM、DOC、DON、DOP）的影响,分析土壤DOM及其组分的土壤肥力效应。结果表明,施肥使高（产量12.75±0.75 t·hm^-2）、中（产量10.50±0.75 t·hm^-2）、低（产量8.25±0.75 t·hm^-2）产田土壤DOM的∑Fex/em分别增加了2.84%、3.56%和-1.52%,平均增加了1.08%,土壤w（DOC）分别增加了20.43%、16.43%和-29.11%,平均增加了9.36%,土壤w（DOP）分别增加了-22.87%、10.30%和4.15%,平均增加了-3.39%,土壤 w（DON）分别增加了-20.63%、6.97%和-8.41%,平均增加了-7.54%。施肥显著增加中产田土壤中w（DOM）,中产田底层（20-40 cm）和高产田表层（0-10 cm）、中层（10-20 cm）土壤w（DOC）,中产田中层和低产田表层土壤w（DOP）,中产田中层土壤w（DON）。施肥增加了低产田土壤FI值（荧光指数）,降低了高产田土壤FI值,施肥增加了高产田土壤HIX（腐殖化指数）,降低了中低产田土壤HIX。施肥显著增加中产田土壤DOM组分含量,降低高、低产田土壤DOM组分含量。施肥主要增加10-20 cm土壤DOM组分含量,耗损20-0 cm土壤DOM组分。施肥促进高产田土壤DOM陆源化,低产田土壤DOM生物源化,施肥使中低产田土壤DOM腐殖化程度降低。施肥不仅是土壤DOM的重要来源,同时通过影响微生物及作物根系活力促进土壤DOM的耗损,因农田土壤质地的差异,施肥对土壤DOM的影响不同。DOM荧光强度与产量呈显著正相关,具有土壤肥力指示作用。     

Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

In this paper we investigate the seasonal autochthonous sources of dissolved organic carbon (DOC) and nitrogen (DON) in the euphotic zone at a station in the upper Chesapeake Bay using a new mass-based ecosystem model. Important features of the model are: (1) carbon and nitrogen are incorporated by means of a set of fixed and varying C:N ratios; (2) dissolved organic matter (DOM) is separated into labile, semi-labile, and refractory pools for both C and N; (3) the production and consumption of DOM is treated in detail; and (4) seasonal observations of light, temperature, nutrients, and surface layer circulation are used to physically force the model. The model reasonably reproduces the mean observed seasonal concentrations of nutrients, DOM, plankton biomass, and chlorophyll a. The results suggest that estuarine DOM production is intricately tied to the biomass concentration, ratio, and productivity of phytoplankton, zooplankton, viruses, and bacteria. During peak spring productivity phytoplankton exudation and zooplankton sloppy feeding are the most important autochthonous sources of DOM. In the summer when productivity peaks again, autochthonous sources of DOM are more diverse and, in addition to phytoplankton exudation, important ones include viral lysis and the decay of detritus. The potential importance of viral decay as a source of bioavailable DOM from within the bulk DOM pool is also discussed. The results also highlight the importance of some poorly constrained processes and parameters. Some potential improvements and remedies are suggested. Sensitivity studies on selected parameters are also reported and discussed.     

Nutrient budget of the lagoonal waters in an open central South Pacific atoll (Tikehau,Tuamotu, French Polynesia)

Nutrient concentrations were measured in the lagoon and surrounding oceanic waters of Tikehau Atoll (Tuamotu Archipelago, French Polynesia) from 1984 to 1987. The atoll-mass effect alters the nutrient profiles: turbulent vertical mixing of the waters along the deeper slopes of the atoll induces nitrogen and phosphorus enrichment of the surface layer. Nutrient concentrations varied with year and month of sampling; except for ammonium, inorganic nutrient levels were lower inside the lagoon than in the surrounding oceanic waters. Nitrogen, phosphorus and silica budgets were calculated by mean differences in nutrient concentrations recorded between lagoon and oceanic surface waters and by the waterexchange rate through the passage linking the lagoon and oceanic waters and the reef-flat spillways. Particulate and dissolved organic nitrogen and ammonium are exported from the lagoon to the open ocean through the westward passage. The nitrogen budget is not balanced by the nitrate input from oceanic waters and the organic nitrogen and ammonium output from lagoonal waters. Nitrogen fixation would appear to constitute another source of nitrogen for lagoonal waters. The phosphorus budget is largely balanced by phosphate input from the oceanic waters and organic phosphorus output from the lagoon waters. The oceanic waters became impoverished in silicate during their crossing of the atoll reef edge and their residence in the lagoon. The atoll constitutes a source of nitrogen for the surrounding oceanic waters.     

淡水水体溶解有机氮对有毒藻种的生物有效性

溶解有机氮（Dissolved organic nitrogen,DON）是多数天然水体中溶解氮的主要组成部分。天然水体DON是许多微生命体包括有毒藻种的氮营养源,在供水安全以及水体富营养化等方面的生态环境效应不容忽视。文章系统地介绍了淡水水体DON含量与来源、生物有效性与估算方法,以及对有毒藻种生长的影响。DON的来源是影响水体中DON含量动态特征的关键因素。DON来源包括陆地径流,植物碎屑,土壤淋溶液,沉积物释放,大气沉降,藻类、大型植物、细菌与细胞死亡或自我分解,微型及大型浮游动物捕食和排泄、分泌物释放等。研究表明约有12％～72％的DON可迅速被生物所利用,具显著差异,究其原因可能是其来源组成、化学本质（分子质量与极性）、测试生物组成、是否有细菌作用等因素造成的。不同藻种具有不同氮源利用能力,DON对藻类生长具有直接或间接的作用,并可能影响藻类群落结构（有毒藻类成为优势种）。考虑到水环境保护与饮用水安全供水的重要性,未来研究应重视淡水水体DON生物有效性与其化学本质的揭示,尤其是对有毒藻种。     

Application of a 15N tracer method to the study of dissolved organic nitrogen uptake during spring and summer in Chesapeake Bay

The dissolved organic nitrogen (DON) pool in marine waters contains a diverse mixture of compounds. It is therefore difficult to accurately estimate planktonic uptake of DON using the limited number of radiolabeled compounds commercially available. We describe a method to estimate DON uptake rates using ¹⁵N-labeled DON recently released from phytoplankton. To make ¹⁵N-labeled DON, we incubated surface water with ¹⁵NH ₄ ⁺ and then isolated the DON, including any recently released DO¹⁵N, with ion retardation resin. This DON was then added to a freshly collected water sample from the same environment to quantify the rate of DON uptake. The technique was applied to investigate rates of DON uptake relative to inorganic nitrogen in the mesohaline Chesapeake Bay during May 1990 and August 1991. The May experiment took place after the spring bloom, and rates of DON uptake [ranging from 0.31 to 0.53 g-atom (g-at) Nl^-1 h^-1] often exceeded rates of NH ₄ ⁺ and NO ₃ ^- uptake combined. The rates of DON uptake at this time were higher than estimated bacterial productivity and were not correlated with bacterial abundance or bacterial productivity. They were, however, correlated with rates of NO ₃ ^- uptake. In May, we estimate that only 7 to 32% of DON uptake was a result of urea utilization. In contrast, in August, when regenerated nutrients predominate in Chesapeake Bay, rates of DON uptake (ranging from 0.14 to 0.51 g-atom Nl^-1 h^-1) were an average of 50% of the observed rates of NH ₄ ⁺ uptake. Consistent with the May experiment, rates of DON uptake were not correlated with bacterial production. A sizable fraction of DON uptake, however, appeared to be due to urea utilization; rates of urea uptake, measured independently, were equivalent to an average of 74% of the measured rates of DON uptake. These findings suggest that, during both periods of study, at least a fraction of the measured DON uptake may have been due to utilization by phytoplankton.     

淡水水体溶解有机氮对有毒藻种的生物有效性

溶解有机氮(Dissolved organic nitrogen,DON)是多数天然水体中溶解氮的主要组成部分。天然水体DON是许多微生命体包括有毒藻种的氮营养源,在供水安全以及水体富营养化等方面的生态环境效应不容忽视。文章系统地介绍了淡水水体DON含量与来源、生物有效性与估算方法,以及对有毒藻种生长的影响。DON的来源是影响水体中DON含量动态特征的关键因素。DON来源包括陆地径流,植物碎屑,土壤淋溶液,沉积物释放,大气沉降,藻类、大型植物、细菌与细胞死亡或自我分解,微型及大型浮游动物捕食和排泄、分泌物释放等。研究表明约有12%～72%的DON可迅速被生物所利用,具显著差异,究其原因可能是其来源组成、化学本质(分子质量与极性)、测试生物组成、是否有细菌作用等因素造成的。不同藻种具有不同氮源利用能力,DON对藻类生长具有直接或间接的作用,并可能影响藻类群落结构(有毒藻类成为优势种)。考虑到水环境保护与饮用水安全供水的重要性,未来研究应重视淡水水体DON生物有效性与其化学本质的揭示,尤其是对有毒藻种。     

The development of a multi-species algal ecodynamic model for urban surface water systems and its application

An ecodynamic model that can simulate four phytoplankton species has been developed to deal with the unique characteristics of urban river systems which has manmade river profile, flow controlled by gates, severe eutrophication status, and fragile aquatic ecosystem. The ecodynamic model was developed referencing two typical models: the water quality simulation model WASP and ecological model CAEDYM. The model can simulate 11 state variables: dissolved oxygen, carbonaceous biochemical oxygen demand, ammonia nitrogen, nitrate nitrogen, organic nitrogen, inorganic phosphorus, organic phosphorus and four phytoplankton species with zooplankton as a boundary condition. The ecodynamic model was applied to Sihai section of the Beijing urban river system, where serious algal blooms broke out in recent years. The dominant phytoplankton species are Cyanophyta, Chlorophyta, Bacillariophyta, and Cryptophyta. Site-specific data on geometry, meteorology, pollution sources, and existing ecosystem parameters were collected and used for model calibration and verification The model results mimic observed trends of water quality and phytoplankton species succession and can be used for forecasting algal blooms as well as assessment of river management measures.     

Growth of marine planktonic diatoms on inorganic and organic nitrogen

A study was conducted to determine if coastal diatoms from eutrophic waters (Werribee, Port Phillip Bay, Australia) are able to grow better than diatoms from oligotrophic waters (Bass Strait, Australia) on organic nitrogen compounds as their principal nitrogen sources. Eight clones of marine planktonic diatoms, belonging to 5 species (Skeletonema costatum, Asterionella japonica, Nitzschia closterium, Coscinodiscus sp., and Fragilaria sp.), were incubated with inorganic (either nitrate or ammonia) or organic (either urea, uric acid, alanine, aspartic acid, glutamic acid, glycine, serine, threonine, or valine) nitrogen sources and growth response was measured under high and low light intensities. All clones grew well on the organic as well as thorganic nitrogen compounds under both light regimes. Intraspecific differences were not great, as no appreciable difference was noted between clones from oligotrophic and eutrophic waters. The two negatively-charged amino acids, aspartic and glutamic acids, were somewhat less effective in supporting growth of some clones than were the other amino acids. Virtually all of the dissolved organic nitrogen (DON) compounds tested were utilizable for algal growth. Further, all clones appeared able to utilize at least some natural DON (uncharacterized) for cell division; in 1980, DON represented 97% of total nitrogen in Bass Strait and 83% of total nitrogen in Werribee waters. The results are consistent with previous findings on algal utilization of certain DON compounds and indicate comparable abilities of cells from oligotrophic and eutrophic coastal waters to assimilate these nutrients.Publication No. 307 in the Ministry for Conservation, Victoria, Environmental Studies Series