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1.
The results of a comparison between chemical water quality determinants and river water fluorescence on the River Tyne, NE England, demonstrate that tryptophan‐like fluorescence intensity shows statistically significant relationships between nitrate, phosphate, ammonia, biochemical oxygen demand (BOD) and dissolved oxygen. Tryptophan‐like fluorescence intensity at the 280 nm excitation/350 nm emission wavelength fluorescence centre correlates with both phosphate (r = 0·80) and nitrate (r = 0·87), whereas tryptophan‐like fluorescence intensity at the 220 nm excitation/350 nm emission wavelength centre correlates with BOD (r = 0·85), ammonia (r = 0·70) and dissolved oxygen (r = ?0·65). The strongest correlations are between tryptophan‐like fluorescence intensity and nitrate and phosphate, which in the Tyne catchment derive predominantly from point and diffuse source sewage inputs. The correlation between BOD and the tryptophan‐like fluorescence intensity suggests that this fluorescence centre is related to the bioavailable or labile dissolved organic matter pool. The weakest correlations are observed between tryptophan‐like fluorescence intensity and ammonia concentration and dissolved oxygen. The weaker correlation with ammonia is due to removal of the ammonia signal by wastewater treatment, and that with dissolved oxygen due to the natural aeration of the river such that this is not a good indicator of water quality. The observed correlations only hold true when treated sewage, sewerage overflows or cross connections, or agricultural organic pollutants dominate the water quality—this is not true for two sites where airport deicer (propylene glycol, which is non‐fluorescent) or landfill leachate (which contains high concentrations of humic and fulvic‐like fluorescent DOM) dominate the dissolved organic matter in the river. Mean annual tryptophan‐like fluorescence intensity agrees well with the General Water Quality Assessment as determined by the England and Wales environmental regulators, the Environment Agency. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

2.
Andy Baker 《水文研究》2002,16(16):3203-3213
There is a need to be able to differentiate the dissolved organic matter (DOM) fraction in river waters. Research in the 1970s and 1980s has attempted to utilize both absorbance and fluorescence to distinguish between DOM fractions in river waters, but both were limited by the available technology. Total organic carbon content has, therefore, been widely used as a standard method of measuring DOM concentration, although it has little power to differentiate DOM fractions. Recent advances in fluorescence spectrophotometry enable rapid and optically precise analysis of DOM. Here, we show how a combination of both fluorescence and absorbance can be used to discriminate statistically between spatial variations of DOM in tributaries in a small catchment of the Ouseburn, NE England. The results of the discriminant analysis suggest that about 70% of the samples can be correctly classified to its tributary. Discriminant function 1 explains 60·8% of the variance in the data and the fulvic‐like fluorescence intensity has the largest absolute correlation within this function; discriminant function 2 explains a further 21·5% of the variance and the fulvic‐like fluorescence emission wavelength has the largest absolute correlation within this function. The discriminant analysis does not correctly classify all tributaries every time, and successfully discriminates between the different tributaries 70% of the time. Occasions when the tributary waters are less well discriminated are due to either episodic pollution events (at two sites) or due to tributaries that have strong seasonal trends in spectrophotometric parameters, which allows the sites to be misclassified. Results suggest that spectrophotometric techniques have considerable potential in the discrimination of DOM in rivers. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

3.
Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability at high‐temporal resolution to evaluate river carbon budgeting, river water health by detecting episodic pollution and to determine short‐term variations in chemical and ecological function. The authors report a 2‐week experiment performed on DOM sampled from Bournbrook, Birmingham, UK, an urban river for which spectrophotometric (fluorescence, absorbance), physiochemical (dissolved organic carbon [DOC], electrical conductivity, pH) and isotopic (D/H) parameters have been measured at hourly frequency. Our results show that the river had sub‐daily variations in both organic matter concentration and characteristics. In particular, after relatively high‐magnitude precipitation events, organic carbon concentration increased, with an associated increase in intensity of both humic‐like and tryptophan‐like fluorescence. D/H isotopic ratio demonstrates different hydrological responses to different rainfall events, and organic matter character reflects this difference. Events with precipitation < 2 mm typically yielded isotopically heavy water with relatively hydrophilic DOM and relatively low specific absorbance. Events with precipitation > 2 mm had isotopically lighter water with higher specific absorbance and a decrease in the proportion of microbially derived to humic‐like fluorescence. In our heavily urbanized catchment, we interpret these signals as one where riverine DOM is dominated by storm sewer‐derived ‘old’ organic matter at low‐rainfall amounts and a mixed signal at high‐precipitation amounts where ‘event’ surface runoff‐derived organic matter dominate during storm sewer and combined sewer overflow routed DOM. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

4.
Frequent heavy rainfalls during the East Asian summer monsoon drastically increase water flow and chemical loadings to surface waters. A solid understanding of hydroclimatic controls on watershed biogeochemical processes is crucial for water quality control during the monsoon period. We investigated spatio‐temporal variations in the concentrations and spectroscopic properties of dissolved organic matter (DOM) and the concentrations of trace metals in Hwangryong River, Korea, during a summer period from the relatively dry month of June through the following months with heavy rainfall. DOM and its spectroscopic properties differed spatially along the river, and also depended on storm and flow characteristics around each sampling time. At a headwater stream draining a forested watershed, the concentrations (measured as dissolved organic carbon (DOC)), aromaticity (measured as specific UV absorbance at 254 nm), and fulvic acid‐ and protein‐like fluorescence of DOM were higher in stormflow than in baseflow waters. DOC concentrations and fluorescence intensities increased along the downstream rural and urban sites, in which DOC and fluorescence were not higher in stormflow waters, except for the ‘first flush’ at the urban site. The response of DOM in reservoir waters to monsoon rainfalls differed from that of stream and river waters, as illustrated by storm‐induced increases in DOM aromaticity and fulvic‐like fluorescence, and no significant changes in protein‐like fluorescence. The results suggest that surface water DOM and its spectroscopic properties differentially respond to changes in hydroclimatic conditions, depending on watershed characteristics and the influence of anthropogenic organic matter loadings. DOC concentrations and intensities of spectroscopic parameters were positively correlated with some of the measured trace metals (As, Co, and Fe). Further research will be needed to obtain a better understanding of climate effects on the interaction between DOM and trace metals. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

5.
Amount and composition of dissolved organic matter (DOM) were evaluated for multiple, nested stream locations in a forested watershed to investigate the role of hydrologic flow paths, wetlands and drainage scale. Sampling was performed over a 4‐year period (2008–2011) for five locations with drainage areas of 0.62, 3.5, 4.5, 12 and 79 ha. Hydrologic flow paths were characterized using an end‐member mixing model. DOM composition was determined using a suite of spectrofluorometric indices and a site‐specific parallel factor analysis model. Dissolved organic carbon (DOC), humic‐like DOM and fluorescence index were most sensitive to changes with drainage scale, whereas dissolved organic nitrogen, specific UV absorbance, Sr and protein‐like DOM were least sensitive. DOM concentrations and humic‐like DOM constituents were highest during both baseflow and stormflow for a 3.5‐ha catchment with a wetland near the catchment outlet. Whereas storm‐event concentrations of DOC and humic DOM constituents declined, the mass exports of DOC increased with increasing catchment scale. A pronounced dilution in storm‐event DOC concentration was observed at peak stream discharge for the 12‐ha drainage location, which was not as apparent at the 79‐ha scale, suggesting key differences in supply and transport of DOM. Our observations indicate that hydrologic flow paths, especially during storms, and the location and extent of wetlands in the catchment are key determinants of DOM concentration and composition. This study furthers our understanding of changes in DOM with drainage scale and the controls on DOM in headwater, forested catchments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

6.
Dissolved organic matter (DOM) is integral to fluvial biogeochemical functions, and wetlands are broadly recognized as substantial sources of aromatic DOM to fluvial networks. Yet how land use change alters biogeochemical connectivity of upland wetlands to streams remains unclear. We studied depressional geographically isolated wetlands on the Delmarva Peninsula (USA) that are seasonally connected to downstream perennial waters via temporary channels. Composition and quantity of DOM from 4 forested, 4 agricultural, and 4 restored wetlands were assessed. Twenty perennial streams with watersheds containing wetlands were also sampled for DOM during times when surface connections were present versus absent. Perennial watersheds had varying amounts of forested wetland (0.4–82%) and agricultural (1–89%) cover. DOM was analysed with ultraviolet–visible spectroscopy, fluorescence spectroscopy, dissolved organic carbon (DOC) concentration, and bioassays. Forested wetlands exported more DOM that was more aromatic‐rich compared with agricultural and restored wetlands. DOM from the latter two could not be distinguished suggesting limited recovery of restored wetlands; DOM from both was more protein‐like than forested wetland DOM. Perennial streams with the highest wetland watershed cover had the highest DOC levels during all seasons; however, in fall and winter when temporary streams connect forested wetlands to perennial channels, perennial DOC concentrations peaked, and composition was linked to forested wetlands. In summer, when temporary stream connections were dry, perennial DOC concentrations were the lowest and protein‐like DOM levels the highest. Overall, DOC levels in perennial streams were linked to total wetland land cover, but the timing of peak fluxes of DOM was driven by wetland connectivity to perennial streams. Bioassays showed that DOM linked to wetlands was less available for microbial use than protein‐like DOM linked to agricultural land use. Together, this evidence indicates that geographically isolated wetlands have a significant impact on downstream water quality and ecosystem function mediated by temporary stream surface connections.  相似文献   

7.
Dissolved organic matter (DOM) concentration and composition in riverine and stream systems are known to vary with hydrological and productivity cycles over the annual and interannual time scales. Rivers are commonly perceived as homogeneous with respect to DOM concentration and composition, particularly under steady flow conditions over short time periods. However, few studies have evaluated the impact of short term variability (<1 day) on DOM dynamics. This study examined whether diurnal processes measurably altered DOM concentration and composition in the hypereutrophic San Joaquin River (California) during a relatively quiescent period. We evaluated the efficacy of using optical in situ measurements to reveal changes in DOM which may not be evident from bulk dissolved organic carbon (DOC) measurement alone. The in situ optical measurements described in this study clearly showed for the first time diurnal variations in DOM measurements, which have previously been related to both composition and concentration, even though diurnal changes were not well reflected in bulk DOC concentrations. An apparent asynchronous trend of DOM absorbance and chlorophyll‐a in comparison to chromophoric dissolved organic matter (CDOM) fluorescence and spectral slope S290–350 suggests that no one specific CDOM spectrophotometric measurement explains absolutely DOM diurnal variation in this system; the measurement of multiple optical parameters is therefore recommended. The observed diurnal changes in DOM composition, measured by in situ optical instrumentation likely reflect both photochemical and biologically‐mediated processes. The results of this study highlight that short‐term variability in DOM composition may complicate trends for studies aiming to distinguish different DOM sources in riverine systems and emphasizes the importance of sampling specific study sites to be compared at the same time of day. The utilization of in situ optical technology allows short‐term variability in DOM dynamics to be monitored and serves to increase our understanding of its processing and fundamental role in the aquatic environment. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

8.
Dissolved organic carbon export from a cutover and restored peatland   总被引：1，自引：0，他引：1  
High demand for horticultural peat has increased peatland drainage and peat extraction in Canada. The hydrology and carbon cycling of these cutover peatlands is greatly altered, necessitating active restoration efforts to permit the regeneration of Sphagnum mosses and the re‐establishment of natural peatland function. The effect of peatland extraction and restoration on the export of dissolved organic carbon (DOC) was examined for three successive seasons (May to October, 1999 to 2001) at two different sites (cutover and restored) in eastern Québec. A shift towards higher DOC concentrations was observed following peatland extraction (maximum: 182·6 mg L?1) and concentrations remained high post‐restoration (maximum: 191·0 mg L?1). The cutover site exported more DOC than the restored site in all three study seasons. The highest exports occurred during the wettest year (1999), with cutover and restored site export of 10·3 and 4·8 g m?2, respectively. In 2000, 8·5 g C m?2 was released from the cutover site, while the restored site released less than half that amount (3·4 g C m?2). In 2001, the restored site released about the same amount of DOC as in the previous year (3·5 g C m?2), while the cutover site load dropped to 6·2 g C m?2. Both sites were net exporters of DOC in all years. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

9.
Absorbance at 360 nm was measured on 44 filtered streamwater samples of different dissolved organic matter (DOM) contents. A regression equation of DOM on absorbance predicted DOM with a standard error of estimate of 1.26 mgl?1, Use of a published equation relating dissolved organic carbon (DOC) to absorbance gave DOC values for the samples which were consistent with measured DOM. The method offers considerable potential for rapid quantification of dissolved organic matter concentrations in streamwater.  相似文献   

10.
亚热带河口区水库DOC和DIC浓度时空变化特征   总被引：1，自引：0，他引：1  
杨平  唐晨  陆苗慧  张林海  Yang Hong  仝川  吕敏 《湖泊科学》2021,33(4):1123-1137
沿海水库汇聚并埋藏着大量的碳,是全球碳循环的重要区域.水体溶解有机碳(DOC)和溶解无机碳(DIC)的生物地球化学行为是水库碳循环研究的重要组成部分,对其系统生物过程和生态环境变化具有重要的影响.为了解亚热带河口区文武砂水库表层水体DOC和DIC的时空分布特征,本研究于2018年11月、2019年3月和6月分别对库区表层水进行多空间点位采样分析.结果表明,研究期间,文武砂水库表层水体DOC和DIC浓度变化范围分别介于0.10～21.13和0.38～34.94 mg/L,其均值分别为(4.09±0.18)和(15.83±0.24) mg/L,最大值分别出现在夏季和秋季;空间分布趋势,整体表现为北库区南库区,且由库区周边的浅水区向库区中心的深水区域呈现出递减的趋势;浮游植物光合作用强度是影响库区DOC和DIC浓度的季节变化的重要因素,而外源污染输入强度是引起库区DOC和DIC浓度空间变化的重要因素.本文结果扩展对水库碳循环的认知,对提高水库水质也提供了有益参考.  相似文献   

11.
The bioavailability of predegraded dissolved organic matter (DOM) from a humic-rich, boreal river to estuarine bacteria from the Baltic Sea was studied in 39-day bioassays. The river waters had been exposed to various degrees of bacterial degradation by storing them between 0 and 465 days in dark prior to the bioassay. The resulting predegraded DOM was inoculated with estuarine bacteria and the subsequent changes in DOM quantity and quality measured. During the incubations, dissolved organic carbon (DOC) and oxygen concentrations decreased, indicating heterotrophic activity. Coloured DOM was degraded less than DOC, indicating a selective utilization of DOM, and humic-like fluorescence components increased during the incubations. The amount of DOC degraded was not affected by the length of DOM predegradation. The percentage of bioavailable DOC (%BDOC) was higher in experiment units with added inorganic nitrogen and phosphorus than without addition (on average 13.5 % and 9.0, respectively), but had no effect on the degradation of fresh, non-predegraded, DOC (%BDOC 12.0 %). Bacterial growth efficiency (BGE) was highest (65 ± 2 %) in the units with fresh DOM, and lowest in units with predegraded DOM and no added inorganic nutrients (11 ± 4 %). The addition of inorganic nutrients increased the BGE of predegraded DOM units by an average of 28 ± 4 %. There was no significant effect on BGE by length of predegradation after the initial drop (<3 months). This study suggests that both the length of predegradation and the inorganic nutrient status in the receiving estuary has consequences to carbon cycling and will determine the amount of terrestrial-derived DOC being ultimately assimilated into marine food webs.  相似文献   

12.
The flux of fluvial carbon from the terrestrial biosphere to the world's oceans is known to be an important component of the global carbon cycle, but within this pathway, the flux and return of carbon to the river network via sewage effluent has not been quantified. In this study, monitoring data from 2000 to 2016 for the dissolved organic carbon (DOC) concentration, biochemical oxygen demand, and chemical oxygen demand of the final effluent of sewage treatment works from across England were examined to assess the amount of DOC contributing to national‐scale fluvial fluxes of carbon. The study shows that the median concentration of DOC in final effluent was 9.4 compared with 4.8 mg C/L for all surface waters for the United Kingdom over the study period and that the DOC in final effluent significantly declined over the study period from 11.0 to 6.4 mg C/L. Rivers receiving sewage effluent showed a significant, on average 19%, increase in DOC concentration downstream of sewage discharges. At the scale of the United Kingdom, the flux of DOC in final effluent was 31 ktonnes C/year with a per capita export of 0.55 kg C/year and compared with an average annual flux of DOC from the United Kingdom of 859 ktonnes C/year, that is, only 3.6% of national‐scale flux. The lability of this DOC was limited, with only 7.4% loss of final effluent DOC concentration over in‐stream residence times of up to 5 days. The direct decline in DOC concentration from sewage treatment works was not large enough on its own to explain the declines observed in DOC concentration in U.K. rivers at their tidal limit.  相似文献   

13.
为了揭示湖滨带土地利用与覆被改变对土壤有机碳库及生态功能的影响,本文选取了巢湖湖滨带（北岸）9个典型样方,分析和比较了表层（0~30 cm）土壤有机碳组分特征以及相关酶的活性.结果表明,巢湖湖滨带不同采样点土壤总有机碳（TOC）含量变化范围为2.88~11.2 g/kg,平均含量为9.12 g/kg,其中原生芦苇（Phragmites australis）湿地土壤TOC含量最高（11.2 g/kg）,而芦苇群落消失后形成的荒滩土壤TOC含量最低,仅为2.88 g/kg.表征湖滨带湿地缓冲性能的土壤阳离子交换量（CEC）也以原生芦苇湿地土壤为最高,并与TOC含量呈现明显正相关.湖滨带表层土壤溶解性有机碳（DOC）和易氧化有机碳（EOC）含量变化范围分别为150~370 mg/kg和1.7~5.2 g/kg,其变化幅度明显高于TOC,其中DOC含量各采样点差异最为显著.除多酚氧化酶外,次生水柳林（Homonoia riparia Lour.）表层土壤几种酶的活性较原生芦苇湿地土壤皆有所上升,特别是蔗糖酶活性增加幅度最为明显.受人类活动干扰较大的湖滨绿地公园和人工草滩土壤过氧化氢酶、脲酶和蔗糖酶酶活性普遍显著低于原生芦苇湿地.除多酚氧化酶外,土壤中几种酶活性与土壤有机碳组分EOC和DOC含量均呈现显著的正相关,其中蔗糖酶活性与DOC含量之间相关系数最高（r=0.907）,其相关性均达到极显著水平.土壤溶解性有机碳和蔗糖酶可以作为表征因土地利用与覆被变化导致湖滨带湿地退化以及生态恢复效果的敏感性指标.  相似文献   

14.
To establish the influence of the cyanobacterial bloom collapse on the characteristics of dissolved organic carbon (DOC) in Lake Taihu, high-molecular-weight dissolved organic matter (HMW-DOM), with sizes between 1 kDa and 0.5 μm, were collected using cross-flow ultrafiltration, from three different eutrophic regions. Isolated HMW-DOM was further characterized by atomic carbon to nitrogen ratio and neutral sugars composition by gas chromatography and mass spectrometry. The results indicated that the cyanobacterial cell lysis induced by nitrate depletion is the likely mechanism for DOC release. The relatively high DOC level was associated with the high chlorophyll a concentration in Meiliang Bay, one of the most eutrophic bays in the northern part of the lake. However, no significant correlations were observed between chlorophyll a concentration and HMW-DOC concentration during the demise of the cyanobacterial bloom in Lake Taihu. No significant differences were found in the HMW-DOC concentration among the three sampling sites, which were selected to represent different eutrophic status. However, a significant difference in the HMW-DOC concentration was found between October 2009 and January 2010 in all three sampling sites (p = 0.02). The HMW-DOC release may be attributed to the cyanobacterial cell lysis after the peak of summer bloom. The similarity in neutral sugar composition between the HMW-DOM and cyanobacterial exopolysaccharides suggests that the cyanobacterial bloom is the source of HMW-DOM. However, the significant correlation between the carbon to nitrogen ratio in HMW-DOM and chlorophyll a concentration was only observed in Meiliang Bay, which implies that apart from the cyanobacteria-derived DOC, a fraction of DOC was from riverine input. The decline of the cyanobacterial bloom also changed the overall DOM pool, leading to a shift in the component of HMW-DOM from a C-enriched material to an N-enriched material, as revealed by the variation in the carbon to nitrogen ratios. Overall, these results demonstrate that the quantitative and qualitative DOM is affected by the post-cyanobacterial bloom in Lake Taihu.  相似文献   

15.
在博斯腾湖选取了13个点位,于2012年5、8、10月测定表层和底层水体中的颗粒有机碳、溶解有机碳、颗粒有机氮和叶绿素a含量.结果显示颗粒和溶解有机碳在表层水体中的浓度与底层相近.博斯腾湖水体中颗粒有机碳的季节变化十分明显,其平均浓度从春季(0.64 mg/L)到夏季(0.71 mg/L)变化不大,但在秋季变化十分显著(浓度达1.58 mg/L).其中西北湖区和湖心区颗粒有机碳的季节变化最明显,东部湖区颗粒有机碳的季节变化相对较小.博斯腾湖水体的颗粒有机碳在春、秋两季主要来自外源输入,在夏季受水体中浮游生物的影响较大.博斯腾湖水体中溶解有机碳也具有一定的季节变化,夏季浓度(平均为9.3 mg/L)略低于春、秋两季(平均为10.3 mg/L).溶解有机碳在河口区的季节变化最强,其夏季浓度明显偏低,主要是由于开都河河水的稀释作用.总体上,博斯腾湖水体中溶解有机碳浓度的变化主要受外部因素的影响.  相似文献   

16.
Fluorescence and UV‐VIS techniques were employed for the investigation of natural organic matter (NOM) of a tropical lake. The relationships of absorbance/dissolved organic carbon (A/DOC), fluorescence intensity/dissolved organic carbon (FI/DOC), fluorescence ratio (FR), and peak wavelength with the highest intensity (PW) were used to distinguish the pedogenic or aquagenic origin of NOM. The values of FR, PW and A285/DOC of high waters (HW) or flooded period samples and of low waters (LW) period samples of the dry season, except for September 2002, confirm the predominance of pedogenic material. The spectra of water were similar to the standard fulvic acid (FA), and the spectra of FA from the lake were similar to the nearby soils, indicative of pedogenic predominance. The results confirm that the dissolved NOM of Patos Lagoon – MS (Brazil), in all sampling periods, predominantly consisted of humic substances (FA) of pedogenic origin.  相似文献   

17.
Water draining from a large agricultural catchment of 1 110 km2 in southwest France was sampled over an 18‐month period to determine the temporal variability in suspended sediment (SS) and dissolved (DOC) and particulate organic carbon (POC) transport during flood events, with quantification of fluxes and controlling factors, and to analyze the relationships between discharge and SS, DOC and POC. A total of 15 flood events were analyzed, providing extensive data on SS, POC and DOC during floods. There was high variability in SS, POC and DOC transport during different seasonal floods, with SS varying by event from 513 to 41 750 t; POC from 12 to 748 t and DOC from 9 to 218 t. Overall, 76 and 62% of total fluxes of POC and DOC occurred within 22% of the study period. POC and DOC export from the Save catchment amounted to 3090 t and 1240 t, equivalent to 1·8 t km?2 y?1 and 0·7 t km?2 y?1, respectively. Statistical analyses showed that total precipitation, flood discharge and total water yield were the major factors controlling SS, POC and DOC transport from the catchment. The relationships between SS, POC and DOC and discharge over temporal flood events resulted in different hysteresis patterns, which were used to deduce dissolved and particulate origins. In both clockwise and anticlockwise hysteresis, POC mainly followed the same patterns as discharge and SS. The DOC‐discharge relationship was mainly characterized by alternating clockwise and anticlockwise hysteresis due to dilution effects of water originating from different sources in the whole catchment. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

18.
Concentrations of both aluminium (Al) and dissolved organic carbon (DOC) in stream waters are likely to be regulated by factors that influence water flowpaths and residence times, and by the nature of the soil horizons through which waters flow. In order to investigate landscape‐scale spatial patterns in streamwater Al and DOC, we sampled seven streams draining the Hubbard Brook valley in central New Hampshire. We observed considerable variation in stream chemistry both within and between headwater watersheds. Across the valley, concentrations of total monomeric aluminium (Alm) ranged from below detection limits (<0·7 µmol l−1) to 22·3 µmol l−1. In general, concentrations of Alm decreased as pH increased downslope. There was a strong relationship between organic monomeric aluminium (Alo) and DOC concentrations (R2 = 0·92). We observed the highest Alm concentrations in: (i) a watershed characterized by a steep narrow drainage basin and shallow soils and (ii) a watershed characterized by exceptionally deep forest floor soils and high concentrations of DOC. Forest floor depth and drainage area together explained much of the variation in ln Alm (R2 = 0·79; N = 45) and ln DOC (R2 = 0·87; N = 45). Linear regression models were moderately successful in predicting ln Alm and ln DOC in streams that were not included in model building. However, when back‐transformed, predicted DOC concentrations were as much as 72% adrift from observed DOC concentrations and Alm concentrations were up to 51% off. This geographic approach to modelling Al and DOC is useful for general prediction, but for more detailed predictions, process‐level biogeochemical models are required. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

19.
Fred Worrall  Tim Burt 《水文研究》2005,19(9):1791-1806
The dissolved CO2 concentration of stream waters is an important component of the terrestrial carbon cycle. This study reconstructs long‐term records of dissolved CO2 concentration for the outlets of two large catchments (818 and 586 km2) in northern England. The study shows that:
  • 1. The flux of dissolved CO2 from the catchments (as carbon per catchment area), when adjusted for that which would be carried by the river water at equilibrium with the atmosphere, is between 0 and 0·39 t km−2 year−1 for the River Tees and between 0 and 0·65 t km−2 year−1 for the River Coquet.
  • 2. The flux of dissolved CO2 is closely correlated with dissolved organic carbon (DOC) export and is unrelated to dissolved CO2 export from the headwaters of the study catchments.
  • 3. The evasion rate of CO2 from the rivers (as carbon per stream area) is between 0·0 and 1·49 kg m−2 year−1, and calculated in‐stream productions of CO2 are estimated as between 0·5 and 2·5% of the stream evasion rate.
  • 4. By mass balance, it is estimated that 8% of the annual flux of DOC is lost within the streams of the catchment.
The study shows that the loss of CO2 from the streams of the Tees catchment is between 3·1 and 7·5 kt year−1 (as carbon) for the River Tees, which is the same order as annual CH4 flux from peats within the catchment and approximately 50% of the net CO2 exchange to the peats of the catchment. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

20.
郑达燕  刘睿  张柳柳  郑财贵  张静 《湖泊科学》2023,35(4):1343-1358
三峡库区拥有目前世界上规模最大的水利枢纽工程,自投入使用以来,为长江流域提供了丰富的水源及电力,促进了经济的发展,但同时也对该区域的生态环境造成了严重的冲击。澎溪河流域作为三峡库区长江流域干流的典型回水区和消落带,是众多学者研究三峡库区生态环境变化的重点区域。为探究不同时空尺度下土地利用对河流溶解性有机质（DOM）的影响,以澎溪河流域为研究对象,基于紫外-可见光谱分析和三维荧光光谱矩阵-平行因子分析,结合河段缓冲区、河岸带缓冲区及子流域3种空间尺度的二级土地利用类型,解析了旱雨季水体DOM的组成及来源特征,并采用相关分析和冗余分析方法探讨了3种空间尺度下土地利用方式对旱雨季水体DOM的多时空尺度影响。结果表明：（1）旱季水体DOM荧光组分以陆源类腐殖质所占比例更大,雨季水体DOM荧光组分以富里酸贡献为主。（2）流域内陆源输入和内源产生对水体DOM丰度均有贡献,雨季较旱季水体DOM的陆源性更强,自生源特征较弱。（3）土地利用在雨季和子流域尺度下对水体DOM的影响更显著,其中,雨季子流域尺度下,土地利用指数对水体DOM参数的解释率为90.35%。（4）不同土地利用方式对水体DOM产生的影响...  相似文献   

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