Hydrocarbon concentrations in water and sediments from UK marine waters,determined by fluorescence spectroscopy     

R.J. Law 《Marine pollution bulletin》1981,12(5):153-157

Between January 1978 and September 1979 samples of subsurface (1 m) water and surface sediment were collected from sites in the North Sea, English Channel, Irish Sea and a number of estuarine areas. These have been analysed by fluorescence spectroscopy (UVF) in order to provide information on the levels of hydrocarbons generally present in UK marine waters.Total hydrocarbon concentrations (THCs) of water samples ranged from 1.1–74 μg l.^?1 Ekofisk crude oil equivalents, all values greater than 3.5 μg l.^?1 occurring inshore. In offshore areas the mean THCs were: 1.3 μg l.^?1 in the northern North Sea, 1.5 μg l.^?1 in the western Channel, 2.5 μg l.^?1 in the eastern Channel and southern North Sea, and 2.6 μg l.^?1 in the Irish Sea.THCs of sediment samples ranged from 0.27–340 μ g^?1 dry weight Ekofisk crude oil equivalents, the highest concentration being in the Queen's Channel, the main entrance to the River Mersey.  相似文献   

Chemical Speciation of Vanadium in Coal Bottom Ash     

Firat Aydin  Abdurrahman Saydut  Beniz Gunduz  Isil Aydin  Candan Hamamci 《洁净——土壤、空气、水》2012,40(4):444-448

Chemical speciation of vanadium is important to understand the true nature of this element in the environment as well as its biochemical pathways. Sample pretreatment, preparation, and chemical speciation methods were applied for vanadium in coal bottom ash here. Two‐stage microwave acid digestion was used to preparation of samples. Determination of vanadium was performed using inductively coupled plasma‐optical emission spectrometry (ICP‐OES). Speciation of vanadium was carried out using a seven‐step sequential extraction procedure of the coal bottom ash each releasing species of vanadium: Water soluble, exchangeable, carbonate, reducible, oxidizable, sulfide, and residual fractions. Total vanadium concentration in the coal bottom ash is 701 mg kg^?1 d.w. The most abundant form of vanadium in coal bottom ash is residual fraction of vanadium (196 mg kg^?1 d.w.). Relative abundances of the remaining vanadium fractions in coal bottom ash are as follows: Reducible (176 mg kg^?1 d.w.) > sulfide (176 mg kg^?1 d.w.) > carbonate (85 mg kg^?1 d.w.) > oxidizable (50 mg kg^?1 d.w.) > water soluble (10.6 mg kg^?1 d.w.) > exchangeable (9.0 mg kg^?1 d.w.).  相似文献   

Aerial flux of particulate hydrocarbons to the Chesapeake Bay Estuary     

David B Webber 《Marine pollution bulletin》1983,14(11):416-421

Bulk hydrocarbon deposition rates have been measured over a 15 month period at four stations in south-eastern Virginia surrounding the lower Chesapeake Bay. A nearly linear trend of atmospheric particulate deposition was recorded. Deposition rates at the urban station (195 μg m^?2 day^?1) were aproximately three times greater than those recorded for nonurban and coastal locations (mean value 69 μg m^?2 day^?1). The increased levels at the urban location were attributed to localized source inputs. Anthropogenic hydrocarbons accounted for approximately 50% of the total deposition at all stations. Significant biogenic inputs were indicated by the odd/even n-alkane distribution. A minimum flux to the water surface, based on mean nonurban deposition rates (24 mg yr^?1), indicated an annual particulate hydrocarbon flux of +275 metric tons. Little information is available for the comparison of additional source inputs; however, the data reported here indicate that the aerial deposition of hydrocarbons is of the same order of magnitude as the input from municipal wastewater facilities and accidental discharge and is a potentially significant source of hydrocarbon pollution to the Chesapeake Bay Estuary.  相似文献   

Acute toxicity of platinum to coho salmon (Oncorhynchus kisutch)     

Paul F. Ferreira  Richard E. Wolke 《Marine pollution bulletin》1979,10(3):79-83

The effects of short-term exposure to tetravalent platinum on survival, opercular movement and post-treatment growth of coho salmon fry (Oncorhynchus kisutch) was investigated. Employing a static water acute toxicity bioassay with platinum as PtCl₄2HCl·6 H₂O, at 8.5±0.2°C, and a water hardness of 55.9±3.5 mg l.^?1 (as CaCo₃), the 24, 48, and 96-h LC₅₀ values were 15.5, 5.2, and 2.5 mg Pt⁴⁺ l.^?1 respectively.Rates of opercular movement for fish exposed to platinum increased with increasing concentrations to a level of 1.0 mg l.^?1. No further significant increases were evident above this level. Hypoactivity of fish exposed to 0.3 mg l.^?1 and higher was evident during the acute toxicity bioassay and much of the post-treatment study. Post-treatment rate of growth for fish exposed to sublethal concentration of platinum for 96 h was less than that of the controls.All organs examined histopathologically were within normal ranges with the exception of the gills and olfactory organ. Lesions in fish exposed to concentration of 0.3 mg l.^?1 and higher were characterized by branchial epithelial hypertrophy and hyperplasia, and necrosis of olfactory epithelial cells.  相似文献   

Effect of parental hypoxic exposure on embryonic development of the offspring of two serpulid polychaetes: Implication for transgenerational epigenetic effect     

J.Y.S. Leung  S.G. Cheung  J.W. Qiu  P.O. Ang  J.M.Y. Chiu  V. Thiyagarajan  P.K.S. Shin 《Marine pollution bulletin》2013

Sperm production and motility, fecundity, and egg size, complexity and viability of serpulid polychaetes Hydroides elegans and Hydroides diramphus after 2-week treatment to hypoxia (2 mg O₂ l⁻¹) was compared with those under normoxia (6 mg O₂ l⁻¹). Despite reduced fecundity, the effect of parental hypoxic exposure on gamete quality was not discernible for both species. However, regardless of their subsequent dissolved oxygen environment, eggs spawned by H. elegans after hypoxic exposure were found to have lower fertilization success, slower embryonic development and a significantly higher yield of malformed embryos than those with a parental normoxic treatment. In contrast, neither fertilization success nor rate of embryonic development was affected for H. diramphus. The results implied that hypoxia was a potential stress reducing the recruitment of H. elegans through non-adaptive epigenetic effect, whereas H. diramphus was a more tolerant species to survive hypoxic events.  相似文献   

Effects of chronic exposure to dispersed oil on selected reproductive processes in adult blue mussels (Mytilus edulis) and the consequences for the early life stages of their larvae     

Baussant T  Ortiz-Zarragoitia M  Cajaraville MP  Bechmann RK  Taban IC  Sanni S 《Marine pollution bulletin》2011,62(7):1437-1445

Mussels (Mytilus edulis) were continuously exposed to dispersed crude oil (0.015-0.25 mg/l) for 7 months covering the whole gamete development cycle. After 1 month exposure to 0.25 mg oil/l, the level of alkali-labile phosphates (ALP) and the volume density of atretic oocytes in female gonads were higher than those in the gonads of control females, indicating that oil affected the level of vitellogenin-like proteins and gamete development. Spawning of mussels was induced after 7 months oil exposure. Parental oil exposure did not affect subsequent fertilization success in clean seawater but this was reduced in 0.25 mg oil/l. Parental exposure to 0.25 mg oil/l caused both slow development and a higher percentage of abnormalities in D-shell larvae 2 days post-fertilization; reduced growth 7 days post-fertilization. These effects were greatly enhanced when larval stages were maintained at 0.25 mg oil/l. Similar studies are warranted for risk assessment prognosis.  相似文献   

Biodegradation of Petroleum Hydrocarbons by Pseudomonas putida Strain MHF 7109     

Dipty Singh  Madhusudan H. Fulekar 《洁净——土壤、空气、水》2010,38(8):781-786

Pseudomonas putida MHF 7109 has been isolated and identified from cow dung microbial consortium for biodegradation of selected petroleum hydrocarbon compounds – benzene, toluene, and o‐xylene (BTX). Each compound was applied separately at concentrations of 50, 100, 250, and 500 mg L^?1 in minimal salt medium to evaluate degradation activity of the identified microbial strain. The results indicated that the strain used has high potential to degrade BTX at a concentration of 50 mg L^?1 within a period of 48, 96, and 168 h, respectively; whereas the concentration of 100 mg L^?1 of benzene and toluene was found to be completely degraded within 120 and 168 h, respectively. Sixty‐two percent of o‐xylene were degraded within 168 h at the 100 mg L^?1 concentration level. The maximum degradation rates for BTX were 1.35, 1.04, and 0.51 mg L^?1 h^?1, respectively. At higher concentrations (250 and 500 mg L^?1) BTX inhibited the activity of microorganisms. The mass spectrometry analysis identified the intermediates as catechol, 2‐hydroxymuconic semialdehyde, 3‐methylcatechol, cis‐2‐hydroxypenta‐2,4‐dienoate, 2‐methylbenzyl alcohol, and 1,2‐dihydroxy‐6‐methylcyclohexa‐3,5‐dienecarboxylate, for BTX, respectively. P. putida MHF 7109 has been found to have high potential for biodegradation of volatile petroleum hydrocarbons.  相似文献   

Effect of Zinc,Copper and Mercury on Channa marulius (HAMILTON)     

B. S. Khangarot 《洁净——土壤、空气、水》1981,9(6):639-649

Static bioassay acute toxicity tests of Zinc, Copper and Mercury were conducted to determine the median lethal concentrations (LC₅₀s) of a freshwater teleost Channa marulius (HAM .) The 96 h LC₅₀ and 95% confidence limits for Zn²⁺ were 25.61 (24.13 … 27.12) mg/l; 0.90 (0.80 … 1.038) mg/l; for Cu²⁺ and 0.314 (0.257 … 0.371) mg/l for Hg²⁺. However, these values decreased at 240 h of exposure and were: 21.09 (18.29 … 24.60) mg Zn²⁺/l; 0.66 (0.568 … 0.841) mg Cu²⁺/l; and 0.131 (0.103 … 0.158) mg Hg²⁺/l. The relative potency ratio of Zn/Hg, Zn/Cu and Cu/Hg suggests that fish were most sensitive to Hg, followed by Cu and Zn ions. The acute toxicities of mixtures of Zn²⁺?Cu²⁺; Zn²⁺?Hg²⁺, Cu²⁺?Hg²⁺ and Zn²⁺?Cu²⁺?Hg²⁺ up to 48 h of exposure were also investigated. The additive index and ranges for Zn²⁺?Cu²⁺ were ?0.241 (-0.577 … 0.054); 0.056 (-0.269 … 0.475) for Zn-Hg; 0.285 (-0.043 … 0.718) for Cu-Hg; and -0.542 (-1.215 … 0.005) for Zn-Cu-Hg. All the mixtures tested showed a greater than additive toxicity because index ranges overlapped zero.  相似文献   

Temperature and toxicity of DDT to sea mullet (Mugil cephalus L.)     

J.H. Powell  D.R. Fielder 《Marine pollution bulletin》1982,13(7):228-230

Sea mullet (Mugil cephalus) were exposed to aqueous suspensions of tech-DDT in seawater, salinity $\text{29.5±0.5‰}$. The 48 h LC₅₀ calculated from these static bioassays ranged from 0.042 to 0.056 mg l.^?1 DDT. Median survival times were then estimated at 15, 20, 25 and 30°C using the upper level of the 48 h LC₅₀ range of concentrations, i.e. 0.056 mg l.^?1. Results indicated that an increase in temperature produced a decrease in toxicity. However, 25°C was the only temperature at which the increase in survival time was statistically significant. Size differences within experimental fish did not contribute to MST.  相似文献   

Der Einfluß von Erdölkohlenwasserstoffen auf die Primärproduktion des Donauplanktons     

J. Tomajka 《洁净——土壤、空气、水》1985,13(5):615-618

Danube river water samples were saturated with mineral oil, and then the primary production (gross) was determined by means of the light-dark bottle method (oxygen) in situ at depths of 0.1… 1.5 m in comparison with untreated samples. Samples were exposed for half a solar day alternately during the first and second half-days. Investigations carried out between March and October for periods of 14 days showed a mean production of 2.56 g · m^?2d^?1 O₂, which was reduced by 36% due to 12.6 mg/l hydrocarbons. Production decreases with the water depth from 6.2 to 0.9 mg · l^?1d^?1 0₂, whereas the inhibition by hydrocarbons increases from 31 to 41%.  相似文献   

Oil pollution on the Egyptian Red Sea coast     

Rifaat G.M. Hanna 《Marine pollution bulletin》1983,14(7):268-271

A simple weighing method using carbon tetrachloride as solvent was used to survey the dissolved hydrocarbon and tarball levels in the area of the Egyptian Red Sea coast. The area of investigation covers the coastal area from Ras-Gharib down to the port of Qosier during the period from September 1979 to February 1981. This survey confirms the presence of extensive oil pollution in the area, especially at Ras-Gharib and Ras-Shukhair. Minimum concentrations were obtained at Ghardaqa where no dissolved hydrocarbons were detected (i.e. less than 10 μg l^?1) in 1979–1980 but an increase to 20 μg l^?1 in 1981 was recorded. The high levels of pollution recorded in the southern part of the Gulf of Suez are related to the presence of the offshore oil fields, most of which are located at Ras-Gharib.  相似文献   

The impact of pipe flow in riparian peat deposits on nitrate transport and removal     

Alan R. Hill 《水文研究》2012,26(20):3135-3146

The effect of preferential flow in soil pipes on nitrate retention in riparian zones is poorly understood. The characteristics of soil pipes and their influence on patterns of groundwater transport and nitrate dynamics were studied along four transects in a 1‐ to >3‐m deep layer of peat and marl overlying an oxic sand aquifer in a riparian zone in southern Ontario, Canada. The peat‐marl deposit, which consisted of several horizontal layers with large differences in bulk density, contained soil pipes that were generally 0.1 to 0.2 m in diameter and often extended vertically for 1 to >2 m. Springs that produced overland flow across the riparian area occurred at some sites where pipes extended to the peat surface. Concentrations of NO₃^?–N (20–30 mg L^?1) and dissolved oxygen (DO) (4–6 mg L^?1) observed in peat pipe systems and surface springs were similar to values in the underlying sand aquifer, indicating that preferential flow transported groundwater with limited nitrate depletion. Low NO₃^?–N concentrations of <5 mg L^?1 and enriched δ¹⁵N values indicated that denitrification was restricted to small areas of the peat where pipes were absent. Groundwater DO concentrations declined rapidly to <2 mg L^?1 in the peat matrix adjacent to pipes, whereas high NO₃^?–N concentrations of >15 mg L^?1 extended over a larger zone. Low dissolved organic carbon values at these locations suggest that supplies of organic carbon were not sufficient to support high rates of denitrification, despite low DO conditions. These data indicate that it is important to develop a greater understanding of pipes in peat deposits, which function as sites where the transport of large fluxes of water with low biogeochemical reaction rates can limit the nitrate removal capacity of riparian zones. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Some effects of sub-lethal concentrations of copper on a marine copepod     

M. Moraitou-Apostolopoulou  G. Verriopoulos 《Marine pollution bulletin》1979,10(3):88-92

Laboratory experiments were carried out to the influence of different concentrations of copper in feeding and respiratory rates, fecundity and longevity of the marine planktonic copepod Acartia clausi, taken from a polluted and a clean area of the Saronic gulf (Greece). In the range of copper concentrations 0.001 to 0.01 mg l.^?1, all tested activities of the animals coming from the clean region seem affected. Feeding acitity, longevity and fecundity showed a progressive reduction from 0.001 to 0.01 mg l.^?1 On the other hand oxygen consumption rates showed a continuous increase at the same range of concentrations.The pollution-adapted population of Acartia seems more resistant to sub-lethal copper stress. Although longevity and respiration were affected in all concentrations used (the reaction was of the same kind as for the animals from the clean region), ingestion rate was not affected at 0.001 mg l.^?1 decreasing at higher concentrations. The fecundity of the pollution-adapted population is higher than that of the clean area, shows a slight increase at 0.001 and 0.0025 mg l.^?1 dropping about to the control animals fecundity level at 0.01 mg l.^?1  相似文献   

The solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site,southern Chile     

Geertrui Y. P. Uyttendaele  Andrs Iroum 《水文研究》2002,16(13):2521-2536

Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44′S, 73°10′W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca²⁺ l^?1, 0·13 mg K⁺ l^?1, 0·11 mg Mg²⁺ l^?1 and <0·08 mg NH₄–N l^?1), except for sodium (1·10 mg l^?1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO₃–N l^?1, total flux 6·3 kg NO₃–N ha^?1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l^?1) for all events. Stream‐flow pH was 6·3 and conductivity was 28·3 μs. Stream‐water chemistry was also dominated by sodium (2·70 mg l^?1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l^?1). The solute budget indicated a net loss of 3·8 kg Na⁺ ha^?1 year^?1, 5·4 kg Mg²⁺ ha^?1 year^?1, 1·5 kg Ca²⁺ ha^?1 year^?1 and 0·9 kg K⁺ ha^?1 year^?1, while 4·9 kg NO₃–N ha^?1 year^?1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO₃–N ha^?1 year^?1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na⁺ ha^?1 year^?1, 21·5 kg K⁺ ha^?1 year^?1, 5·1 kg Mg²⁺ ha^?1 year^?1) compared with the secondary native forest site (24·7 kg Na⁺ ha^?1 year^?1, 18·9 kg K⁺ ha^?1 year^?1 and 4·4 kg Mg²⁺ ha^?1 year^?1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca²⁺ ha^?1 year^?1) compared with the pine stand (12·6 kg Ca²⁺ ha^?1 year^?1). Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Acute toxicity of copper to sea catfish     

Craig W. Steele 《Marine pollution bulletin》1983,14(5):168-170

Sea catfish (Arius felis) were exposed to aqueous solutions of reagent grade cupric chloride in artificial seawater ($\text{30.0±2.0‰}$, 21–23°C) in four static bioassays. The 24, 48, 72 and 96 h LC₅₀ were calculated and found to be 5.43, 4.17, 3.57 and 2.40 mg l.^?1 copper, respectively. Experimental concentrations of copper producing subtle behavioral changes in this species correspond to less than 0.3% of the 72 h LC₅₀. Based on this comparison with literature values, a new, maximum ‘safe’ concentration for copper in marine waters of 0.01 mg l.^?1 is proposed.  相似文献   

Ultrasound Accelerated Oxidation of Organic Dyes by a Micron‐Sized Copper/Peroxomonosulfate System     

Chaorong Liu  Jing Zhang  Qingguo Wang  Peng Zhou  Sikui Hu 《洁净——土壤、空气、水》2020,48(2)

Experiments on the degradation of acid orange 7 (AO7) using micron‐sized zero‐valent copper (ZVC) are conducted in acidic aqueous solution under ultrasonic (US) irradiation. The US/ZVC/peroxymonosulfate (PMS) process for AO7 degradation is significantly better than that of an independent system. Based on the characterization of ZVC, it is observed that the corrosion speed of ZVC increases after ultrasound, owing to which a greater amount of Cu⁺ (0–3.03 mg L^?1) and Cu²⁺ are produced. Exposure to US irradiation increases the available surface area of the catalysts to generate many new reactive sites for the degradation process. The AO7 degradation rate after the addition of a new copper reagent—neocuproine hemihydrate—from 6.33% to 100% proved that Cu⁺ is the main activator of PMS. Results indicated that free radicals (OH^? and SO₄^??) act as activators of PMS in the process. And higher ultrasound power, lower solution pH, and a larger ZVC dose are favorable for AO7 removal.  相似文献   

A confirmation of the correlation between hydrocarbons and chlorophyll a in the upper euphotic zone     

Adam Zsolnay 《Marine pollution bulletin》1979,10(4):107-108

The average hydrocarbon content found in 14 water samples from the euphotic zone off Northwest Africa was 4.4 μg l.^?1 with no extreme values. The average chlorophyll $\text{a}$ content was 1.9 μg l.^?1. The data fit a model proposed in a previous paper (Zsolnay, 1977). The resulting equation was $\text{HC}\text{= ?2.7 + 4.82}\text{Ch}\text{?0.942}\text{Ch}{}^2$ and could explain 59% of the variance in the hydrocarbon distribution. This indicates a correlation that is significant at the 0.002 level.  相似文献   

The surface geochemical exploration of oil and gas in the Gangbatong-Ya’anxiang and the Dongqiao-Nam Co of the Qinghai-Tibet region     

Bo Xiong  XianQing Li  YiBin Li  Qing Tan 《中国科学D辑(英文版)》2009,52(1):69-76

Due to the complexity of geological background and the adverseness of natural geographical environment in the Qinghai-Tibet Plateau, it is very difficult to carry out petroleum geological study in this region. The Qinghai-Tibet Plateau is the only blank space of petroleum exploration on a large scale. The authors carried out the surface geochemical exploration of oil and gas in the Gangbatong-Ya’anxiang and Dongqiao-Nam Co of the Qinghai-Tibet region. Based on the data of actual detection and experiments in the studied area, the characteristics of concentration and profile distribution of the main geochemical exploration indicators (total adsorbed hydrocarbon, altered carbonate, thermal released mercury, etc.) were discussed. The origin of hydrocarbon was also discussed. Moreover, the oil and gas potential of different sections in the Qiangtang Basin and the Biru Basin were evaluated, which could provide references for the exploration and prediction of oil and gas in this region. The concentrations of total adsorbed hydrocarbons in the Ya’anxiang of Suoxian County-Zadong of Baqing County and the Jiecha-Dangxiong of Anduo County in the Qinghai-Tibet region are high, averaging 312.64 μL·kg^?1 and 164.36 μL·kg^?1. Their altered carbonate concentrations are relatively low, averaging 0.11% and 0.56%. Their concentrations of thermal released mercury are relatively high, averaging 13.09×10^?9 and 1.94×10^?9. Geochemical exploration results in fact reflect hydrocarbon information in the underground, which are mainly petroleum associated gas and over-matured cracking gas. The Jiecha-Charenluma and the Xiamaya’ertong-Suoba sections in the Qiangtang Basin are the most favorable ones for oil and gas and the Ekou-Zadong section is relatively favorable one, while the Nam Co and the Zigetangcuo-Dongqiao sections in the Biru Basin are the favorable ones for oil and gas, and the Jiang Co-Nading Co and the Ya’anxiang-Ya’ertong sections are relatively favorable ones.  相似文献   

Beaver dams along an agricultural stream in southern Ontario,Canada: their impact on riparian zone hydrology and nitrogen chemistry     

Alan R. Hill  Tim P. Duval 《水文研究》2009,23(9):1324-1336

The hydrology and nitrogen biogeochemistry of a riparian zone were compared before and after the construction of beaver dams along an agricultural stream in southern Ontario, Canada. The beaver dams increased surface flooding and raised the riparian water table by up to 1·0 m. Increased hydraulic gradients inland from the stream limited the entry of oxic nitrate‐rich subsurface water from adjacent cropland. Permeable riparian sediments overlying dense till remained saturated during the summer and autumn months, whereas before dam construction a large area of the riparian zone was unsaturated in these seasons each year. Beaver dam construction produced significant changes in riparian groundwater chemistry. Median dissolved oxygen concentrations were lower in riparian groundwater after dam construction (0·9–2·1 mg L^?1) than in the pre‐dam period (2·3–3·9 mg L^?1). Median NO₃‐N concentrations in autumn and spring were also lower in the post‐dam (0·03–0·07 mg L^?1) versus the pre‐dam period (0·1–0·3 mg L^?1). In contrast, median NH₄‐N concentrations in autumn and spring months were higher after dam construction (0·3–0·4 mg L^?1) than before construction (0·13–0·14 mg L^?1). Results suggest that beaver dams can increase stream inflow to riparian areas that limit water table declines and increase depths of saturated riparian soils which become more anaerobic. These changes in subsurface hydrology and chemistry have the potential to affect the transport and transformation of nitrate fluxes from adjacent cropland in agricultural landscapes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Zur Rolle der Stickstoffixation im Stoffhaushalt eines geschichteten Sees     

H. Rnicke  K. Bahr 《洁净——土壤、空气、水》1983,11(3):295-307

In the dimict lake Arend (5.1 km², 146 hm³, 49.5 m z_max), nitrogen is production-limiting with concentrations below the detection limit during the production period. Phytoplankton achieves biomasses of up to 18 mg/l fresh matter, essential contributions being made by Aphanizomenon with 2 mg/l and Anabaena with up to 10 mg/l. Nitrogen fixation was measured by the ethine reduction technique (acetylene reduction) during periods of the occurrence of heterocystforming Cyanophyceae and achieved peak values up to 6.59 μg N² · h^?1 · l^?1 or 14.87 m^?2 · h^?1 g N₂ · m^?2 · h^?1. The rates of fixation show a safe correlation with the biomass of heterocyst-containing Cyanophyceae (r = 0.88), their development beginning at values below the N : P-ratio of 2.66.  相似文献