水中天然含氮有机物的形成、迁移转化及分布

天然含氮有机物是水环境中的重要组成部分,其在天然水体中的形态及分布对环境质量有显著影响.本文围绕水中天然含氮有机物在氮循环中的地位、迁移转化以及其在国内主要水域中的分布情况,对天然含氮有机物的研究现状进行了梳理.我国不同水域中溶解性含氮有机物(DON)浓度相差较大;其中水体中DON浓度一般在1.0 mg·L^-1以下;沉积物中DON浓度通常为几十至几百mg·kg^-1.水体DON以分子量<1 kDa的有机物为主,主要成分是尿素、氨基酸等物质.沉积物DON以分子量<1 kDa和>30 kDa的有机物为主,其中前者主要由芳构化程度较高的氨基酸等小分子有机物构成,后者以腐殖质类为主.水体中部分胺类物质本身具有一定毒性,游离氨基酸等DON还是卤乙腈、卤代酰胺、卤代硝基甲烷、卤化氰和亚硝胺等含氮消毒副产物的重要前体物.由于水体中许多含氮有机物具有生物可利用性,有机氮可能是引起水体富营养化的重要原因之一.     

Removal of organic matter and disinfection by-products precursors in a hybrid process combining ozonation with ceramic membrane ultrafiltration

The performance of an integrated process including coagulation, ozonation, ceramic ultrafiltration (UF) and biologic activated carbon (BAC) filtration was investigated for the removal of organic matter and disinfection by-products (DBPs) precursors from micro-polluted surface water. A pilot scale plant with the capacity of 120 m³ per day was set up and operated for the treatment of drinking water. Ceramic membranes were used with the filtration area of 50 m² and a pore size of 60 nm. Dissolved organic matter was divided into five fractions including hydrophobic acid (HoA), base (HoB) and neutral (HoN), weakly hydrophobic acid (WHoA) and hydrophilic matter (HiM) by DAX-8 and XAD-4 resins. The experiment results showed that the removal of organic matter was significantly improved with ozonation in advance. In sum, the integrated process removed 73% of dissolved organic carbon (DOC), 87% of UV₂₅₄, 77% of trihalomethane (THMs) precursors, 76% of haloacetic acid (HAAs) precursors, 83%of trichloracetic aldehyde (CH) precursor, 77% of dichloroacetonitrile (DCAN) precursor, 51% of trichloroacetonitrile (TCAN) precursor, 96% of 1,1,1-trichloroacetone (TCP) precursor and 63% of trichloronitromethane (TCNM) precursor. Hydrophobic organic matter was converted into hydrophilic organic matter during ozonation/UF, while the organic matter with molecular weight of 1000–3000 Da was remarkably decreased and converted into lower molecular weight organic matter ranged from 200–500 Da. DOC had a close linear relationship with the formation potential of DBPs.     

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.     

Detecting N-nitrosamines in water treatment plants and distribution systems in China using ultra-performance liquid chromatography-tandem mass spectrometry

N-nitrosodimethylamine (NDMA) and several other N-nitrosamines have been detected as disinfection by-products in drinking waters in many countries around the world. An ultra-performance liquid chromatographytandem mass spectrometry method with solid phase extraction sample preparation was developed to study the occurrence of N-nitrosamines in several water treatment plants and distribution systems in China. Isotope labeled N-nitrosodi-n-propylamine-d14 (NDPA-d14) was selected as the internal standard for quantification. The solid phase extraction procedures including pH, enrichment process and MS/MS parameters including capillary voltage, cone gas flow, cone voltage, collision energy were optimized to give average recoveries of 26% to 112% for nine N-nitrosamine species. The instrument detection limits were estimated to range from 0.5 to 5 ??g·L^?1 for the nine N-nitrosamine species. NDMA and several other N-nitrosamines were found at fairly high concentrations in several water treatment plants and distribution systems. NDMA was found in all locations, and the highest concentrations in cities B, G, T, and W were 3.0, 35.7, 21.3, and 19.7 ng·L^?1, respectively. A wide range of N-nitrosamines concentrations and species were observed in different locations. Higher concentrations of N-nitrosamines were detected in distribution systems that were further away from the treatment plants, suggesting that the contact time between the residual disinfectant and natural organic matter may play an important role in the formation of these compounds.     

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.     

Occurrence and removal of N-nitrosodimethylamine and its precursors in wastewater treatment plants in and around Shanghai

Six wastewater treatment plants （WWTPs） were investigated to evaluate the occurrence and removal of N-nitrosodimethylamine （NDMA）, NDMA formation potential （FP） and four specific NDMA precursors, dimethylamine （DMA）, trimethylamine （TMA）, dimethyl- formamide （DMFA） and dimethylaminobenzene （DMAB）. DMA and tertiary amines with DMA functional group commonly existed in municipal wastewater. Chemically enhanced primary process （CEPP） had no effect on removal of either NDMA or NDMA FP. In WWTPs with secondary treatment processes, considerable variability was observed in the removal of NDMA （19%-85%） and NDMA FP （16%-76%）, moreover, there was no definite relationship between the removal of NDMA and NDMA FP. DMA was well removed in all the six surveyed WWTPs; its removal efficiency was greater than 97%. For the removal of tertiary amines, biologic treatment processes with nitrification and denitrification had better removal efficiency than conventional activated sludge process. The best removal efficiencies for TMA, DMFA and DMAB were 95%, 68% and 72%, respectively. CEPP could remove 73% of TMA, 23% of DMFA and 36% of DMAB. After UV disinfection, only 17% of NDMA was removed due to low dosage of UV was applied in WWTP. Although chlorination could reduce NDMA precursors, NDMA concentration was actually increased after chlorination.     

Investigation into the content and formation of trihalomethanes and molecular change of dissolved organic matter from a typical water plant in south China

Trihalomethanes (THMs) are a class of disinfection by-products that were proved to have adverse effects to human health. Investigation into its content change and molecular composition variation of its main precursor, which is believed to be dissolved organic matter (DOM) during water purification process, can help understand the formation mechanism of THMs and optimize the processes in drinking water treatment plant (DWTP). This is of great significance to ensure the safety of urban water supply. In this study, detailed changes of THMs’ content and formation potential were determined during the water purification process in summer and winter at a typical DWTP in south China. Specific molecular composition changes of DOM were also characterized by ultrahigh-resolution mass spectrometry, to comprehensively study its correlation with the formation of THMs in different water processing units and seasons. The result showed that chlorination will cause drastic changes of water quality and a sharp increase in the concentration of THMs (18.7 times in summer and 13.9 times in winter). Molecular-level characterization of DOM indicates that a range of lignin-like substance with lower O/C (<?0.5) and H/C (<?1.25) vanished and considerable amount of protein-like and tannins-like substance with higher H/C (>?1.25) and O/C (>?0.5) was formed after chlorination. Analysis of Cl-containing products demonstrated that a bulk of CHOCl₁ and CHOCl₂ compounds with moderate molecular weights were formed in both winter and summer. However, the newly formed CHOCl₁ molecules showed a relatively higher mass weight in summer (>?500 Da) compared to winter (300–500 Da). Seasonal differences also emerged in the result of correlation between the trihalomethanes formation potential and total organic carbon. The correlation coefficient in summer (0.500) was lower than that in winter (0.843). The results suggested that the exhaustive reaction and contribution of DOM to THMs may vary in different seasons.

     

黄浦江原水中各类有机物在铝盐混凝过程中的去除效果

通过XAD-8/XAD-4吸附树脂联用技术将黄浦江微污染原水中溶解性有机物分为疏水酸、非酸疏水物质、弱疏水物质及亲水物质4类有机物,研究了铝盐混凝工艺对黄浦江水中4类有机物的去除效果.硫酸铝在最佳混凝条件下,即投加量为8 mg·l~(-1)(以Al计),pH=5.5时,水中的DOC和UV_(254)的去除率分别达到23%和32%.有机物的亲疏水性对混凝工艺有较大影响,混凝法倾向于优先去除水中疏水性有机物,而疏水性有机物的酸碱性对混凝工艺没有明显影响,酸性和非酸类疏水物质均能破混凝工艺所去除.疏水酸是水中最主要的三氯甲烷类消毒副产物的前体物质,混凝工艺对于三氯甲烷类消毒副产物有良好的控制作用,总体减少了 39%的生成量.而不同类的有机物之间,混凝工艺对消毒副产物控制效果不同,其中对疏水酸的控制三氯甲烷消毒副产物的效果最好,减少了63%的生成量,亲水物质的控制效果最差,三氯甲烷生成量仪减少了3%.疏水酸表现出比亲水物质更强的生物毒性,混凝工艺能明显降低原水的毒性.     

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。     

Nutrient balance in the ecosystem of the North Western Adriatic Sea

The effects of biological processes on dissolved inorganic nutrients, dissolved organic nitrogen (DON) and phosphorus (DOP) are considered in the north western Adriatic Sea. The budgets of these nutrients, which represent the sum of production and consumption processes in comparison to advection, are discussed with regard to dissolved inorganic nitrogen ( 15 N labelled) uptake, which basically indicates the biological demand of this fraction of nitrogen by phytoplankton community. The presented data show that, although important, the continental input of dissolved inorganic nitrogen (DIN), mainly nitrate, is utilised and recycled within the coastal marine environment (budget of m 15 r µmol-N·dm m 3 ). In fact, during four cruises (June, 1996; February, 1997; June, 1997; February, 1998), phytoplankton production was mainly driven by regenerated nutrients ( f h 0.4). Regarding dissolved inorganic phosphorus (DIP), the negative budgets observed in most cases (down to m 0.4 r µmol-P·dm m 3 ) confirm, above all, its scarce availability in this basin. Recycling processes rather than continental inputs regulate the availability of this nutrient. In addition, the comparison between DIN and DIP budgets indicates that, in this ecosystem, dissolved inorganic phosphorus is recycled faster than nitrogen through the living particulate and dissolved organic pools. As a consequence of biological activities, a strong production of dissolved organic nitrogen (DON) can occur in summer (up to +22 r µmol-N·dm m 3 ) while DOP shows a more independent behaviour both with respect to its accumulation in the environment and to the observed nitrogen variations.     

预处理＋超滤技术处理饮用水

在查阅了大量的国内外文献资料基础上，主要介绍了超滤技术及预处理应用于饮用水净化的研究。尽管超滤是一种去除病原微生物（病原菌、病毒和病原原生动物）有效的消毒工艺，但因它的截留分子量比较高，去除天然有机物相对无效。试验证明，适当的预处理可使超滤膜不仅能去除天然水中大量颗粒状物质，同时也可去除溶解性有机物及THMFP。     

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。     

珠江水质和含氮消毒副产物的时空变化

研究区域是珠江广东省段的3条干流(西江、北江、东江)及交汇处(广州),目标是研究分析2年内29个采样点的常规水质指标的时空变化及溶解性有机氮(dissolved organic nitrogen,DON)对于消毒副产物生成势(specific disinfection byproduct formation potential,SDBPFP)的影响.结果表明,对于常规水质指标浓度而言,在时间上,西江、北江、东江三者基本无变化,但交汇处有稍微的变化,一般在7、10月份浓度偏高;在空间上,各干流及交汇处沿径流方向浓度呈逐渐增大趋势,且交汇处水质指标的浓度普遍高于干流.水体的PO34-浓度、总氮(total nitrogen,TN)浓度最高分别超出《国家地表水环境质量》Ⅴ类水质标准10倍、4倍.溶解性有机碳(dissolved organic carbon,DOC)浓度与UV254呈良好的线性关系,R2=0.901;但DON与卤乙腈(halogenacetonitrile,HANs)浓度的线性关系较差,R2为0.440.卤乙腈生成势(specific halogen acetonitrile formationpotential,SHANFP)与DOC/DON比值基本无线性关系.     

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.     

Huminstoffe in Sedimentporenwässern ausgewählter Bundeswasserstraßen

Humic substances are an important component of organic carbon in natural waters. Their character and properties are determined by the sources and the processes of their origin. Humic substances are not exclusively refractory compounds, but they are involved in several transformation processes in the water. It is not possible to directly analyze humic substances, therefore several methods were applied for their characterization. The presented LC-OCD-technique is a size-exclusion-chromatography with online UV- and carbon detection. Carbon fractions, e.?g. humic substances were differentiated by their molecular size. The portion of humic substances in sediment porewaters of the rivers Elbe, Rhine, Danube, Oder, Müritz-Elde-Waterway was determined. With only a few exceptions it ranges from 50 to 67?% of the dissolved organic carbon. The high molecular weight fraction accounts for 10 to 34?%, and the fraction of the low molecular weight substances was from 7 to 37?%. The ratio between the spectral absorption coefficient (254?nm) and the organic carbon is called SUVA (L/mg × m) and is an inidicator of the proportion of unsaturated bonds in the humic substances. Both high molecular herbal components (e.?g. cellulose, lignin) and biological degradiation products (e.?g. amino acids, sugar) are involved in sediment porewater transformation and degradiation processes. This demonstrates the distribution of the dissolved organic carbon between the fractions.     

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。     

Using regression models to evaluate the formation of trihalomethanes and haloacetonitriles via chlorination of source water with low SUVA values in the Yangtze River Delta region,China

The purpose of this study was to develop the multiple regression models to evaluate the formation of trihalomethanes (THMs) and haloacetonitriles (HANs) during chlorination of source water with low specific ultraviolet absorbance (SUVA) in Yangtze River Delta, China. The results showed that the regression models of THMs exhibited good accuracy and precision, and 86–97 % of the calculated values fell within ±25 % of the measured values. While the HANs models showed relatively weak evaluation ability, as only 75–83 % of the calculated values were within ±25 % of the measured values. The organic matter [dissolved organic carbon (DOC) or UV absorbance at 254 nm] and bromide exerted the most important influence on the formation of HANs. While for THMs, besides the organic matter and bromide, reaction time was also a key factor. Comparing the models for total THMs (T-THMs) in this study with others revealed that the regression models from the low SUVA waters may have low DOC coefficients, but high bromide coefficients as compared with those from the high SUVA waters.     

Significant increase of assimilable organic carbon (AOC) levels in MBR effluents followed by coagulation,ozonation and combined treatments: Implications for biostability control of reclaimed water

• Annual AOCs in MBR effluents were stable with small increase in warmer seasons. • Significant increase in AOC levels of tertiary effluents were observed. • Coagulation in prior to ozonation can reduce AOC formation in tertiary treatment. • ∆UV₂₅₄ and SUVA can be surrogates to predict the AOC changes during ozonation. As water reuse development has increased, biological stability issues associated with reclaimed water have gained attention. This study evaluated assimilable organic carbon (AOC) in effluents from a full-scale membrane biological reactor (MBR) plant and found that they were generally stable over one year (125–216 µg/L), with slight increases in warmer seasons. After additional tertiary treatments, the largest increases in absolute and specific AOCs were detected during ozonation, followed by coagulation-ozonation and coagulation. Moreover, UV₂₅₄ absorbance is known to be an effective surrogate to predict the AOC changes during ozonation. Applying coagulation prior to ozonation of MBR effluents for removal of large molecules was found to reduce the AOC formation compared with ozonation treatment alone. Finally, the results revealed that attention should be paid to seasonal variations in influent and organic fraction changes during treatment to enable sustainable water reuse.     

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.     

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。