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1.
In this study, seven types of first‐order and one‐variable grey differential equation model (abbreviated as GM (1, 1) model) were used to forecast hourly roadside particulate matter (PM) including PM10 and PM2.5 concentrations in Taipei County of Taiwan. Their forecasting performance was also compared. The results indicated that the minimum mean absolute percentage error (MAPE), mean squared error (MSE), root mean squared error (RMSE), and maximum correlation coefficient (R) was 11.70%, 60.06, 7.75, and 0.90%, respectively when forecasting PM10. When forecasting PM2.5, the minimum MAPE, MSE, RMSE, and maximum R‐value of 16.33%, 29.78, 5.46, and 0.90, respectively could be achieved. All statistical values revealed that the forecasting performance of GM (1, 1, x(0)), GM (1, 1, a), and GM (1, 1, b) outperformed other GM (1, 1) models. According to the results, it revealed that GM (1, 1) was an efficiently early warning tool for providing PM information to the roadside inhabitants.  相似文献   

2.
Evapotranspiration (ET) is one of the basic components of the hydrologic cycle and is essential for estimating irrigation water requirements. In this study, an artificial neural network (ANN) model for reference evapotranspiration (ET0) calculation was investigated. ANNs were trained and tested for arid (west), semi‐arid (middle) and sub‐humid (east) areas of the Inner Mongolia district of China. Three or four climate factors, i.e. air temperature (T), relative humidity (RH), wind speed (U) and duration of sunshine (N) from 135 meteorological stations distributed throughout the study area, were used as the inputs of the ANNs. A comparison was conducted between the estimates provided by the ANNs and by multilinear regression (MLR). The results showed that ANNs using the climatic data successfully estimated ET0 and the ANNs simulated ET0 better than the MLRs. The ANNs with four inputs were more accurate than those with three inputs. The errors of the ANNs with four inputs were lower (with RMSE of 0·130 mm d?1, RE of 2·7% and R2 of 0·986) in the semi‐arid area than in the other two areas, but the errors of the ANNs with three inputs were lower in the sub‐humid area (with RMSE of 0·21 mm d?1, RE of 5·2% and R2 of 0·961. For the different seasons, the results indicated that the highest errors occurred in September and the lowest in April for the ANNs with four inputs. Similarly, the errors were higher in September for the ANNs with three inputs. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

3.
Özgür Kişi 《水文研究》2009,23(2):213-223
This paper reports on investigations of the abilities of three different artificial neural network (ANN) techniques, multi‐layer perceptrons (MLP), radial basis neural networks (RBNN) and generalized regression neural networks (GRNN) to estimate daily pan evaporation. Different MLP models comprising various combinations of daily climatic variables, that is, air temperature, solar radiation, wind speed, pressure and humidity were developed to evaluate the effect of each of these variables on pan evaporation. The MLP estimates are compared with those of the RBNN and GRNN techniques. The Stephens‐Stewart (SS) method is also considered for the comparison. The performances of the models are evaluated using root mean square errors (RMSE), mean absolute error (MAE) and determination coefficient (R2) statistics. Based on the comparisons, it was found that the MLP and RBNN computing techniques could be employed successfully to model the evaporation process using the available climatic data. The GRNN was found to perform better than the SS method. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

4.
Ambient concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) were measured at 51 sampling points by passive sampling technique in Kocaeli, an important industrial city in Turkey. Samples were analyzed by UV‐spectrophotometry for NO2 and O3 and by ion chromatography for SO2, respectively. Concentrations of SO2, NO2, and O3 were determined to investigate their spatial distribution and source characterization. The sampling campaigns revealed an average concentration of 8 µg/m3 (max. 82 µg/m3) for SO2, and 14 µg/m3 (max. 40 µg/m3) for NO2, in summer; while average winter concentrations were 25 µg/m3 (max. 61 µg/m3) for SO2, and 50 µg/m3 (max. 100 µg/m3) for NO2. The maximum ozone concentrations were determined to be 86 µg/m3 in summer and 61 µg/m3 in winter downwind of the source areas of the precursor pollutant emissions. The results showed that NO2 and SO2 concentrations in industrial and urban areas were two to four times higher compared with rural areas in the summer and winter. In the light of the information obtained from the spatial interpolation of the pollutant concentrations, a selection of appropriate locations for continuous monitoring was suggested according to the European Community (EU) directives.  相似文献   

5.
Soil moisture has a pronounced effect on earth surface processes. Global soil moisture is strongly driven by climate, whereas at finer scales, the role of non‐climatic drivers becomes more important. We provide insights into the significance of soil and land surface properties in landscape‐scale soil moisture variation by utilizing high‐resolution light detection and ranging (LiDAR) data and extensive field investigations. The data consist of 1200 study plots located in a high‐latitude landscape of mountain tundra in north‐western Finland. We measured the plots three times during growing season 2016 with a hand‐held time‐domain reflectometry sensor. To model soil moisture and its temporal variation, we used four statistical modelling methods: generalized linear models, generalized additive models, boosted regression trees, and random forests. The model fit of the soil moisture models were R2 = 0.60 and root mean square error (RMSE) 8.04 VWC% on average, while the temporal variation models showed a lower fit of R2 = 0.25 and RMSE 13.11 CV%. The predictive performances for the former were R2 = 0.47 and RMSE 9.34 VWC%, and for the latter R2 = 0.01 and RMSE 15.29 CV%. Results were similar across the modelling methods, demonstrating a consistent pattern. Soil moisture and its temporal variation showed strong heterogeneity over short distances; therefore, soil moisture modelling benefits from high‐resolution predictors, such as LiDAR based variables. In the soil moisture models, the strongest predictor was SAGA (System for Automated Geoscientific Analyses) wetness index (SWI), based on a 1 m2 digital terrain model derived from LiDAR data, which outperformed soil predictors. Thus, our study supports the use of LiDAR based SWI in explaining fine‐scale soil moisture variation. In the temporal variation models, the strongest predictor was the field‐quantified organic layer depth variable. Our results show that spatial soil moisture predictions can be based on soil and land surface properties, yet the temporal models require further investigation. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

6.
The feasibility of polynomial chaos expansion (PCE) and response surface method (RSM) models is investigated for modelling reference evapotranspiration (ET0). The modelling results of the proposed models are validated against the M5 model tree and multi-layer perceptron neural network (MLPNN) methods. Two meteorological stations, Isparta and Antalya, in the Mediterranean region of Turkey, are inspected. Various input combinations of daily air temperature, solar radiation, wind speed and relative humidity are constructed as input attributes for the ET0. Generally, the modelling accuracy is increased by increasing the number of inputs. Including wind speed in the model inputs considerably increases their accuracy in modelling ET0. Mean absolute error (MAE), root mean square error (RMSE), agreement index (d) and Nash-Sutcliffe efficiency (NSE) are used as comparison criteria. The PCE is the most accurate model in estimating daily ET0, giving the lowest MAE (0.036 and 0.037 mm) and RMSE (0.047 and 0.050 mm) and the highest d (0.9998 and 0.9999) and NSE (0.9992 and 0.9996) with the four-input PCE models for Isparta and Antalya, respectively.  相似文献   

7.
Jun Xiao  Fei Zhang  Zhangdong Jin 《水文研究》2016,30(25):4855-4869
Hydrochemistry methods were used to decipher the weathering and geochemical processes controlling solute acquisition of river waters in the dry season in the middle Loess Plateau (MLP), one of the most severely eroded areas and turbid riverine systems in the world. River waters were neutral to slightly alkaline with pH varying from 7.6 to 9.6. The total dissolved solids decreased from northwest to southeast with a mean value of 804 mg/l, much higher than the global average and other large rivers in China. Ternary diagram showed that river waters were dominated by Na+, HCO3?, and Cl? with the main water‐type of HCO3?–Cl?–Na+. Saturation index values, Mg2+, Ca2+, and HCO3? analyses indicated the preferential Ca2+ removal by calcite precipitation. Gibbs plots and stoichiometry plots indicated that the dissolved solutes were mainly derived from rock weathering with minor anthropogenic and atmospheric inputs. Samples in the northwestern basin are also influenced by evaporation. A forward model of mass budget calculation showed that, owing to high soluble characteristics, evaporite dissolution was a major feature of river waters and contributed 41% to the total dissolved cations on average, while carbonate and silicate weathering contributed 28%,and 25% on average, respectively. Besides evaporite dissolution, cation exchange is also responsible for the high concentrations of Na+ in river water. Spatial variations showed that evaporite dissolution and silicate weathering were higher in the northern basin, whereas carbonate weathering was higher in the southern basin. Different from most rivers in the world, the physical erosion rates (varying from 117.7 to 4116.6 t/km2y) are much higher than the chemical weathering rates (varying from 3.54 to 6.76 t/km2y) in the MLP because of the loose structure of loess and poor vegetation in the basin. In the future, studies on comparison of water geochemistry in different seasons and on influence of different types of land use and soil salinization on water geochemistry, denudation rates, and water quality should be strengthened in the MLP. These results shed some lights on processes responsible for modern loess weathering and also indicate the importance of time‐series sampling strategy for river water chemistry. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

8.
Ambient air polycyclic aromatic hydrocarbon (PAH) samples were collected at a suburban (n = 63) and at an urban site (n = 14) in Izmir, Turkey. Average gas‐phase total PAH (∑14PAH) concentrations were 23.5 ng m?3 for suburban and 109.7 ng m?3 for urban sites while average particle‐phase total PAH concentrations were 12.3 and 34.5 ng m?3 for suburban and urban sites, respectively. Higher ambient PAH concentrations were measured in the gas‐phase and ∑14PAH concentrations were dominated by lower molecular weight PAHs. Multiple linear regression analysis indicated that the meteorological parameters were effective on ambient PAH concentrations. Emission sources of particle‐phase PAHs were investigated using a diagnostic plot of fluorene (FLN)/(fluorine + pyrene; PY) versus indeno[1,2,3‐cd]PY/(indeno[1,2,3‐cd]PY + benzo[g,h,i]perylene) and several diagnostic ratios. These approaches have indicated that traffic emissions (petroleum combustion) were the dominant PAH sources at both sites for summer and winter seasons. Experimental gas–particle partition coefficients (KP) were compared to the predictions of octanol–air (KOA) and soot–air (KSA) partition coefficient models. The correlations between experimental and modeled KP values were significant (r2 = 0.79 and 0.94 for suburban and urban sites, respectively, p < 0.01). Octanol‐based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. However, overall there was a relatively good agreement between the measured KP and soot‐based model predictions.  相似文献   

9.
Groundwater is an especially important freshwater source for water supplies in the Maku area of northwest Iran. The groundwater of the area contains high concentrations of fluoride and is, therefore, important in predicting the fluoride contamination of the groundwater for the purpose of planning and management. The present study aims to evaluate the ability of the extreme learning machine (ELM) model to predict the level of fluoride contamination in the groundwater in comparison to multilayer perceptron (MLP) and support vector machine (SVM) models. For this purpose, 143 water samples were collected in a five-year period, 2004–2008. The samples were measured and analyzed for electrical conductivity, pH, major chemical ions and fluoride. To develop the models, the data set—including Na+, K+, Ca2+ and HCO3 ? concentrations as the inputs and fluoride concentration as the output—was divided into two subsets; training/validation (80% of data) and testing (20% of data), based on a cross-validation technique. The radial basis-based ELM model resulted in an R 2 of 0.921, an NSC of 0.9071, an RMSE of 0.5638 (mg/L) and an MABE of 0.4635 (mg/L) for the testing data. The results showed that the ELM models performed better than MLP and SVM models for prediction of fluoride contamination. It was observed that ELM models learned faster than the other models during model development trials and the SVM models had the highest computation time.  相似文献   

10.
Air quality has been deteriorated seriously in urban areas as a result of increasing anthropogenic activities. Meteorological conditions affect air pollution levels in the urban atmosphere significantly due to their important role in transport and dilution of the pollutants. This paper aims to investigate usability of some promising statistical methods for examining the impacts of metrological factors on SO2 and PM10 levels. Data were collected from city centre of Kocaeli in winter periods from 2007 to 2010 as pollutant concentrations increase in winters due to expanding combustion facilities. Results of bivariate correlation analysis showed that humidity and rainfall have remarkable negative correlations with the pollutants. Multiple linear regression models and artificial neural network (ANN) models were used to predict next day's PM10 and SO2 levels. In regression models calculated R2 values were 0.89 and 0.75 for PM10 and SO2, respectively. Among the various architectures, single layer networks provided better performance in ANN applications. Highest R2 values were obtained as 0.89 and 0.69 for PM10 and SO2, respectively, by using appropriate networks.  相似文献   

11.
The effect of present-day and future NOx emissions from aircraft on the NOx and ozone concentrations in the atmosphere and the corresponding radiative forcing were studied using a three-dimensional chemistry transport model (CTM) and a radiative model. The effects of the aircraft emissions were compared with the effects of the three most important anthropogenic NOx surface sources: road traffic, electricity generation and industrial combustion. From the model results, NOx emissions from aircraft are seen to cause an increase in the NOx and ozone concentrations in the upper troposphere and lower stratosphere, and a positive radiative forcing. For the reference year 1990, the aircraft emissions result in an increase in the NOx concentration at 250 hPa of about 20 ppt in January and 50 ppt in July over the eastern USA, the North Atlantic Flight Corridor and Western Europe, corresponding to a relative increase of about 50%. The maximum increase in the ozone concentrations due to the aircraft emissions is about 3-4 ppb in July over the northern mid-latitudes, corresponding to a relative increase of about 3-4%. The aircraft-induced ozone changes cause a global average radiative forcing of 0.025 W/m2 in July. According to the ANCAT projection for the year 2015, the aircraft NOx emissions in that year will be 90% higher than in the year 1990. As a consequence of this, the calculated NOx perturbation by aircraft emissions increases by about 90% between 1990 and 2015, and the ozone perturbation by about 50-70%. The global average radiative forcing due to the aircraft-induced ozone changes increases by about 50% between 1990 and 2015. In the year 2015, the effects of the aircraft emissions on the ozone burden and radiative forcing are clearly larger than the individual effects of the NOx surface sources. Taking chemical conversion in the aircraft plume into account in the CTM explicitly, by means of modified aircraft NOx emissions, a significant reduction of the aircraft-induced NOx and ozone perturbations is realised. The NOx perturbation decreases by about 40% and the ozone perturbation by about 30% in July over Western Europe, the eastern USA and the North Atlantic Flight Corridor.  相似文献   

12.
Laccase from the white‐rot fungus Pleurotus florida, produced under solid‐state fermentation conditions, was used for the decolorization of reactive dye Remazol Brilliant Blue R (RBBR). RBBR was decolorized up to 46% by P. florida laccase alone in 10 min. In the presence of N‐hydroxybenzotriazole (HBT), the rate of decolorization was enhanced 1.56‐fold. Central composite design of response surface methodology with four variables namely, dye, enzyme, redox mediator concentrations, and time at five levels was applied to optimize the RBBR decolorization. The predicted optimum level of variables for maximum RBBR decolorization (87%) was found to be 52.90 mg L?1 (RBBR), 1.87 U mL?1 (laccase), 0.85 mM (HBT), and 7.17 min (time), respectively. The validation results showed that the experimental value of RBBR decolorization (82%) was close to the predicted one. The disappearance of C–N and C–X groups, and a small shift in N–H groups in Fourier‐transform infra red (FTIR) spectroscopy confirms the degradation of RBBR chromophore by laccase enzyme. The phytotoxicity of RBBR was considerably reduced after the treatment with laccase. RBBR decolorization kinetics; Km and Vmax were calculated to be 145.82 mg L?1 and 24.86 mg L?1 min, respectively.  相似文献   

13.
Three techniques for obtaining soil water solutions (gravitational and matrical waters extracted using both in situ tension lysimeters and in vitro pressure chambers) and their later chemical analysis were performed in order to know the evolution of the soil‐solution composition when water moves down through the soil, from the Ah soil horizon to the BwC‐ or C‐horizons of forest soils located in western Spain. Additionally, ion concentrations and water volumes of input waters to soil (canopy washout) and exported waters (drainage solutions from C‐horizons) were determined to establish the net balance of solutes in order to determine the rates of leaching or retention of ions. A generalized process of sorption or retention of most components (even Cl?) was observed, from the soil surface to the C‐horizon, in both gravitational and matrical waters, with H4SiO4, Mn2+, Na+, and SO42? being the net exported components from the soil through the groundwater. These results enhance the role of the recycling effect in these forest soils. The net percentages of elements retained in these forest soils, considering the inputs and the outputs balance, were 68% K+, 85% Ca2+, 58% Mg2+, 7% Al3+, 5% Fe3+, 34% Zn2+, 57% Cl?, and 20% NO3?, and about 75% of dissolved organic carbon was mineralized. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
The performance of one pilot‐scale and two full‐scale membrane bioreactors (MBR) were evaluated based on the control of main operational parameters, composition of microbial community and pathogens concentration in the treated outlet. Plants were designed for 0.75 m3/day (A), 60 m3/day (B) and 30 m3/day (C). Inlet and outlet samples were monitored for chemical oxygen demand (COD), biological oxygen demand, total suspended solids, ammonia nitrogen concentration (NH4–N), nitrate nitrogen concentration, total Kjeldahl nitrogen, total phosphorus and phosphate phosphorus concentration concentrations. Plants showed good COD removal: 91.9% for Plant A, 97.8% for Plant B and 94.2% for Plant C. The targeted nitrogenous ion was NH4–N due to the requirements for outlet limits. NH4–N removal was moderate for Plant A (73.3%) and Plant B (86.1%) and excellent for Plant C (>99%). Excellent phosphorus removal was achieved by Plant A (average outlet concentration was 0.7 mg/L, efficiency 84.7%). Unsatisfactory results for phosphorus removal were achieved at the full‐scale plants due to operational problems. The dependency between the extracellular polymeric substances increase and decreasing mixed liquor volatile suspended solids for both lab and full‐scale plants was confirmed. Soluble microbial product concentrations were reduced by 65–68% after coagulant dosage for Plant A. Outlets from the MBR plants were monitored for the presence of pathogens (thermotolerant coliforms, Escherichia coli, intestinal Enterococci and culturable microorganisms at 22 and 37°C). The treated effluent from Plant A, B and C met Czech national legislation regarding reuse criteria (standards) for environment, irrigation and swimming purposes. Plants B and C were not able to achieve requirements for potable water and personal hygiene quality standards.  相似文献   

15.
Estimation of daily evapotranspiration (ET) over cloudy regions highly desires models which rely on meteorological data only. Notwithstanding, the conventional crop coefficient (Kc) method requires detailed knowledge of geo/biophysical properties of the coupled land-vegetation system, precipitation, and soil moisture. Six Eddy Covariance (EC) towers in Iowa, California and New Hampshire of the USA (covering corn, soybeans, prairie, and deciduous forest) were selected. Investigation on 6 years (2007–2012) 15-min micrometeorological records of these sites revealed that there is an indubitable strong interaction between relative humidity (RH), reference ET (ETo), and actual ET at different timescales. This allowed to bypass the need for the non-meteorological inputs and express Kc as a second-order polynomial function of RH and ETo, the ambient regression evapotranspiration model (AREM). The coefficients of the empirical function are crop-specific and may require calibration over different soil types. The mean absolute percentage error (MAPE) of the regression against daily EC observations was 17% during the growing season, and 32% throughout the year with root mean square error (RMSE) of 0.74 mm day−1 and coefficient of determination of 0.71. The model was fully operational (MAPE of 34% and RMSE of 0.82 mm day−1) over the four Iowan sites based on inputs from local weather stations and NLDAS-2 forcing data of NASA. AREM was capable of capturing the dynamics of ET at 15-min and daily timescales irrespective of varying complexities associated with biophysical, geophysical and climatological states.  相似文献   

16.
《水文科学杂志》2013,58(1):253-265
Abstract

Measurements of dielectric permittivity and electrical conductivity were taken in a saline gypsiferous soil collected from southern Tunisia. Both time domain reflectometry (TDR) and the new WET sensor based on frequency domain reflectometry (FDR) were used. Seven different moistening solutions were used with electrical conductivities of 0.0053–14 dS m?1. Different models for describing the observed relationships between dielectric permittivity (K a ) and water content (θ), and bulk electrical conductivity (EC a ) and pore water electrical conductivity (EC p ) were tested and evaluated. The commonly used K a –θ models by Topp et al. (1980) and Ledieu et al. (1986) cannot be recommended for the WET sensor. With these models, the RMSE and the mean relative error of the predicted θ were about 0.04 m3 m?3 and 19% for TDR and 0.08 m3 m?3 and 54% for WET sensor measurements, respectively. Using the Hilhorst (2000) model for EC p predictions, the RMSE was 1.16 dS m?1 and 4.15 dS m?1 using TDR and the WET sensor, respectively. The WET sensor could give similar accuracy to TDR if calibrated values of the soil parameter were used instead of standard values.  相似文献   

17.
In this study, it was aimed to characterize temporal variations of air pollutants for determining contribution to pollution episodes and to obtain correlations between these pollutants. With this aim we used data analysis for measured sulfur dioxide (SO2), particulate matter (PM, black fume and PM10), nitrogen oxides (NOx), ozone (O3), carbon monoxide (CO), methane (CH4), and non‐methane hydrocarbons (NMHC) recorded in Kocaeli, one of the most industrilizated cities of Turkey. Pollutant concentrations were the results of continuous and semi‐automatic measurements. Semi‐automatic measurements of SO2 and PM (black fume) were enclosing period from 1987 to 2008 whereas continuous monitoring of all pollutants included years of 2007–2009. In the first stage of the study daily, monthly, annual, and seasonal variations of pollution were researched. Annual average concentrations were compared with limits set by Air Quality Protection Regulation (AQPR), Air Quality Evaluation and Management Regulation (AQEMR), World Health Organization (WHO), European Union (EU), and National Ambient Air Quality Standards (USEPA). In the following stage relationships between pollutants such as NO2–O3, NOx–CO, NOx–NMHC, and NOx–SO2 were investigated and correlation coefficients were determined as 0.87, 0.56, 0.51, and 0.69, respectively. R2 values of regression models developed from these correlations were 0.78, 0.56, 0.34, and 0.72, respectively. Vehicle density of the traffic was evaluated with NOx–O3 emissions and decrease was seen in NOx emissions due to decreasing vehicle density at weekends whereas O3 concentrations increased. These correlations enable prediction of the parameters that cannot be measured which is important for providing improvement in early warning systems.  相似文献   

18.
In this study, a new strain of microorganism Shewanella putrefaciens was used for biofiltration of a pyridine laden air stream in a corn‐cob packed biotrickling filter. In the biotrickling filter tested with S. putrefaciens, the maximum removal of pyridine is determined to be 100% at less than the average inlet concentration of 0.653 g m–3 and more than 93% at a higher average inlet concentration of 1.748 g m–3 (phase VIII) with an empty bed residence time (EBRT) of 106 s. However, when the biotrickling filter was operated at a low EBRT of 53 s and almost the same average inlet concentration of 1.752 g m–3 (phase VII), the removal level attained was not greater than 85%. The maximum elimination capacity (EC) of the biotrickling filter was 102.34 g m–3h–1 at an inlet pyridine load of 119.62 g m–3h–1 with an EBRT of 53 s in phase VII. The maximum deviation of the EC from the 100% conversion line varied from 0.257 to 10.166% when going from phase I to VIII. Kinetic analysis showed that the maximum removal rate, rmax, and saturation constant, Ks, values for pyridine were calculated as 0.24 g m–3h–1 and 6.44 g m–3, respectively, with a correlation coefficient, R2, of 0.9939 and a standard deviation of error of 23.94%. The information contained herein indicates that the corn‐cob packed biotrickling filter inoculated by S. putrefaciens should provide excellent performance in the removal of gaseous pyridine.  相似文献   

19.
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   

20.
Based on measured stream nitrogen concentrations at outlets of 12 small sub‐areas (1·3–54·7 km2) in a largely forested catchment during the base flow period, we investigated the influences of discharges and different catchment characteristics on stream nitrogen concentration. Our field surveys were carried out during the 11‐month's period from April 2001 to February 2002 and the correlations between nitrogen concentrations and catchment characteristics were studied. The results showed that the vegetation cover was strongly correlated to total nitrogen (TN) and nitrate + nitrite ? nitrogen (NOx‐N) concentrations. That is, the TN and NOx‐N concentrations had positive correlations with mean normalized difference vegetation cover index (NDVI) of each sub‐area during dormant seasons (mean NDVI < 0 · 70) and had negative correlations during the growing season (mean NDVI ≥ 0 . 70). The significance of catchment characteristics to TN and NOx‐N concentrations was ranked as vegetation cover > soil > topography > land use, and the best models can account for 55–64% of the variance of TN and NOx‐N concentrations. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

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