Geostatistics for assessing the efficiency of a distributed physically‐based water quality model: application to nitrate in the Seine River     

Edwige Polus  Nicolas Flipo  Chantal de Fouquet  Michel Poulin 《水文研究》2011,25(2):217-233

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Collocation of hydrological and biological attenuation of nitrate in an urban stream          下载免费PDF全文

Trevor Klein  Laura Toran 《水文研究》2016,30(17):2948-2957

The hydrologic and biogeochemical processes that control nutrient export in urban streams are not well understood. Attenuation can occur by tributary dilution, groundwater discharge, and biological processing both in the water column and the hyporheic zone. A wastewater treatment plant on Pennypack Creek, an urban stream near Philadelphia, PA, provided high nitrate concentrations for analysis of downstream attenuation processes. Longitudinal sampling for an 8‐km reach revealed decreases in nitrate concentration of 2 mg l^?1 at high flow and 4.5 mg l^?1 during low flow. During high flow, δ¹⁵N‐NO₃ increased from 9.5 to 10.5‰ and during low flow increased from 10.1 to 11.1‰. Two reaches were sampled at fine spatial intervals (approximately 200 m) to better identify attenuation processes. Mixing analysis indicated that groundwater discharge and biological processing both control nitrate concentration and isotope signatures. However, fine‐scaled sampling did not reveal spatially discrete zones; instead, these processes were occurring simultaneously. While both processes attenuate nitrate, they have opposite isotope signatures, which may have muted changes in δ¹⁵N‐NO₃. At high flow, a decrease in Cl/NO₃ ratios helped distinguish groundwater discharge occurring along both finely sampled reaches. At low flow, biological processing seemed to be occurring more extensively, but the δ¹⁵N‐NO₃ signature was not consistent with either a single process or a sequential combination of groundwater dilution and biological nitrate attenuation. The collocation of processes makes it more difficult to assess biological processing hot spots and predict how urbanization and subsequent stream restoration influence nitrate attenuation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Condensation water in heritage touristic caves: Isotopic and hydrochemical data and a new approach for its quantification through image analysis     

Cristina Liñán  José Benavente  Yolanda del Rosal  Iñaki Vadillo  Lucía Ojeda  Francisco Carrasco 《水文研究》2021,35(5):e14083

Condensation water is a major factor in the conservation of heritage caves. It can cause dissolution of the rock substrate (and the pigments of rock art drawn on it) or covering thereof with mineral components, depending on the chemical saturation degree of the condensation water. In show caves, visitors act as a source of CO₂ and thus modify the microclimate, favouring negative processes that affect the conservation of the caves. In spite of their interest, studies of the chemical composition of this type of water are scarce and not very detailed. In this work we present research on the condensation water in the Nerja Cave, one of the main heritage and tourist caves in Europe. The joint analysis of isotopic, hydrochemical, mineralogical and microbiological data and the use of image analysis have allowed us to advance in the knowledge of this risk factor for the conservation of heritage caves, and to demonstrate the usefulness of image analysis to quantify the scope of the possible corrosion condensation process that the condensation water could be producing on the bedrock, speleothem and rock art. To our knowledge, this application of image analysis (relative to the condensation water in caves) is the first one of this type that has been documented.  相似文献   

金华地区夏秋大气中过氧乙酰硝酸酯的污染特征     

孙鑫  唐倩  邹巧莉  金玲玲  宋清川  徐达  田旭东 《南京气象学院学报》2020,12(6):721-728

过氧乙酰硝酸酯（PAN）是由VOCs和NO_x的光化学反应生成的一种典型二次污染物,比O₃更适合作为光化学污染的指示剂.2019年6—10月对浙江中部盆地金华市大气中PAN进行了在线监测,并对影响其体积分数变化的因素进行了分析,同时还分析了一次典型的光化学污染过程.结果表明,观测期间PAN的平均体积分数为0.656×10^-9,最高体积分数为4.348×10^-9,日均体积分数水平在0.130×10^-9~2.203×10^-9之间.PAN日变化特征显著,9月为明显的双峰变化,其他月份均为单峰.受气象条件的影响,夏季的污染程度显著低于秋季.9月27—30日典型污染时段内,PAN的小时均值是整个观测期均值的2.8倍,污染以本地积累为主.前体物浓度水平差异与去除机制的不同是影响PAN和O₃相关性的重要因素,此外NO/NO₂的比值是影响PAN生成速率的重要因素,PAN的峰值基本出现在NO/NO₂比值较低的时段.在生成PAN的VOCs物种中,丙烷、乙烷和间/对二甲苯所占比例较大.  相似文献   

海水中胶体有机碳的测定──高温燃烧法和紫外/过硫酸钾法的比较   总被引：5，自引：0，他引：5  

王江涛  赵卫红  谭丽菊  张正斌 《海洋学报》2000,22(2):65-70

利用切向超滤(cross-flow ultrafiltration)技术对海水中胶体有机碳(COC)和真溶解有机碳(UOC)进行了分离,并分别用高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳进行了测定。测定结果表明,切向超滤能定量分离海水中的胶体有机碳,高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳的测定结果没有明显的系统误差,表明这两种方法的氧化效率基本相同,胶体粒子的存在,对紫外/过硫酸钾法的氧化效率没有显着影响。  相似文献   

A sensor package for the simultaneous determination of nanomolar concentrations of nitrite, nitrate, and ammonia in seawater by fluorescence detection   总被引：2，自引：0，他引：2  

Robert T. Masserini Jr.  Kent A. Fanning 《Marine Chemistry》2000,68(4):1421

A fluorescence-based chemistry has been developed for the detection of nitrite and nitrate (as excess nitrite following reduction of nitrate to nitrite). Detection limits are 4.6 and 6.9 nM, respectively. The technique capitalizes on the triple bond between the two nitrogen atoms within the diazonium ion formed via the well-known reaction between an acidified nitrite sample and an aromatic primary amine. Fluorescence of π-electrons within this bond allows this reaction to be probed with standard fluorescence spectroscopy. Reverse Flow Injection Analysis (rFIA) is used to correct for background fluorescence from leachates and naturally occurring dissolved organic matter (DOM). Comparisons of samples analyzed for nitrite with this technique and with a highly-sensitive chemiluminescent method [Braman, R.S., Hendrix, S.A., 1989. Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium (III) reduction with chemiluminescence detection. Analytical Chemistry, 61 (24) 2716–2718] showed excellent agreement between the two methods (slope=0.9996 and r²=0.9956). These fluorescent nitrite and nitrate + nitrite chemistries were coupled in a sensor package with a modified version of a fluorescent ammonia chemistry [Jones, R.D., 1991. An improved fluorescence method for the determination of nanomolar concentrations of ammonia in natural waters, Limnology and Oceanography. 36(4) 814–819], which also has a nanomolar detection limit. The throughput rate of the fully automated three-channel instrumentation is 18 samples per hour. A field experiment demonstrated the capability of the nutrient sensor package to determine horizontal gradients in nitrate, nitrite, and ammonia in oligotrophic surface waters.  相似文献   

Temporal variability of temperature-nitrate relationship in a coastal region     

殷建平  林立  王友绍  杜建伟 《中国海洋湖沼学报》2014,32(4):879-885

The inverse relationship between nitrate and temperature （N-T relationship） has been used to estimate new production from remotely sensed sea surface temperature at the regional or global scale of oceans. This study aimed to develop a time-series model of the N-T relationship from automated, continuous hourly observations over two years on the coast of Halifax, Canada. The model demonstrated time-series variability of the N-T relationship at a coastal station on the Nova Scotia Shelf, with adjusted R2=0.999 4 and RMSE=0.025 7. The maximum residual value was 0.077. The annual temperature variations described a sine curve, and daily, weekly, and monthly variations fluctuated within the normal ranges, controlled by the local climate. The annual variation of nitrate concentration formed nearly a sine curve. Heavy or long- lasting rainfall increased nitrate concentration by 4 to 30-fold in 24 h, and then the increased nitrogen was quickly depleted by phytoplankton growth in 10 to 48 h. In general, biological activity was a key factor in causing nitrate concentration change, dependent mainly on seawater temperature. The power function of the N-T relationship observed in our study area could be used to quickly estimate sea surface nitrate concentration, in combination with temperature data obtained by remote sensing.  相似文献   

Nitrate transport in the unsaturated zone: a case study of the riverbank filtration system Karany,Czech Republic     

Frantisek Buzek  Renata Kadlecova  Ivana Jackova  Zdena Lnenickova 《水文研究》2012,26(5):640-651

Nitrate transport in the unsaturated zone of a riverbank filtration (RBF) system in Karany, Czech Republic, was studied. Previous study of the system estimated RBF recharge as 60% riverbank filtrate and 40% local groundwater contaminated by nitrates. Nitrate concentrations observed in RBF recently cannot be explained by simple groundwater contamination and a new conception of groundwater recharge is suggested. A two‐component model based on water ¹⁸O data modelled recharge of local groundwater. One component of groundwater recharge is rainfall and irrigation water moving through the unsaturated zone of the Quaternary sediments in piston flow. The second component is groundwater from the Cretaceous deposits with a free water table. Both the components of groundwater recharge have different nitrate concentrations, and resulting contamination of groundwater depends on the participation of water from Quaternary and Cretaceous deposits. Nitrates' origins and their mixing in the subsurface were traced by ¹⁵N data. Nitrate transport from the unsaturated zone is important and time variable source of groundwater contamination. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Study of colloidal phosphorus variation in estuary with salinity   总被引：1，自引：0，他引：1  

CHEN Ding  ZHENG Airong  CHEN Min 《海洋学报(英文版)》2010,29(1):17-25

The variation of colloidal phosphorus with salinity in estuary was studied in this paper, which was compared with those of particle and truly dissolved phosphorus with the purpose of ˉnding out the similarities and di?erences between their behaviors in the estuary. Distribution patterns of phospho- rus in particle, colloidal and truly dissolved phase at di?erent salinities and their relationships with suspended particulate matter were also studied to understand the transformation and transporta- tion of colloidal phosphorus in estuarine area. The result showed that the concentrations of total colloidal phosphorus, organic colloidal phosphorus and inorganic colloidall phosphate all descended from river-end to sea-end, illustrating their terrigenous source. Ratios of organic to total colloidal phosphorus decreased with salinity's increment, indicating that organic phosphorus was in°uenced by scavenging process of colloid more signiˉcantly as compared with inorganic phosphate. Both of the phosphorus variation tendencies and the proportion between organic and inorganic phosphorus in colloidal phase was similar with that in truly dissolved phase while di?erent from that in particle phase.  相似文献   

Tracing groundwater nitrate sources in the Dakar suburban area: an isotopic multi‐tracer approach     

M. Diédhiou  S. Cissé Faye  O. C. Diouf  S. Faye  A. Faye  V. Re  S. Wohnlich  F. Wisotzky  U. Schulte  P. Maloszewski 《水文研究》2012,26(5):760-770

The Dakar region is a mega city with multiple contaminant sources from urban expansion as well as industrial and agricultural activities. The major part of the region is underlain by unconfined sandy aquifer, which is vulnerable to contaminants derived from human land use. At present, the contaminated groundwater which extends over a large area in the suburban zone of Thiaroye poses a threat to the future of this valuable resource, and more specifically, a health threat. This study focuses on nitrate pollution occurrences and associated processes using nitrate isotope data (¹⁵N_NO3, ¹⁸O_NO3) combined with environmental isotopic tracers (¹⁸O, ²H, and ³H). Samples from 36 wells were collected to determine the level, distribution, and sources of contamination in relation to land use. Results indicate that shallow groundwater in the urbanized area of Thiaroye shows distinct evidence of surface contamination with nitrate as much as 300 mg/l NO₃^?. In rural area not serviced by water supply distribution network, much higher NO₃^? contents were found in few wells due to household and livestock feedlots. In most groundwater samples δ¹⁵N values ranged from + 10 to + 22‰, indicative of predominantly human and animal wastes. This was confirmed by environmental isotope data which suggest a mixture of polluted recharge waters. By using the dual δ¹⁵N vs δ¹⁸O as well as δ¹⁵N vs NO₃^? approach, denitrification may occur to some extent but it is blurred by mixing with new infiltrated nitrates and cycling derived from continuous leaky septic system. Results suggest that nitrate contamination of the aquifer is a consequence of unregulated urbanisation (homemade latrines), continuing contaminant transfer in shallow water depth where aerobic conditions prevail. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献