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1.
ABSTRACT: The hypotheses that fish survival probabilities may be lower (1) at less than peak operating turbine efficiency; (2) at deeper entrainment depth; and (3) with the deployment of extended‐length intake guidance screens, are not supported by results on yearling chinook salmon smolts (Oncorhynchus tshawytscha) at Lower Granite Dam, Snake River, Washington. Estimated 96 h survival probabilities for the six test conditions ranged from 0.937 to 0.972, with the highest survival at turbine operating towards the lower end of its efficiency. A blanket recommendation to operate all Kaplan type turbines within ± 1 percent of their peak efficiency appears too restrictive. Cavitation mode survival (0.946) was comparable to that at peak operating efficiency mode (0.937), as was the survival between upper (0.947) and mid depths (0.937). Survival differed only slightly among three turbine intake bays at the same depth (0.937 to 0.954), most likely due to differential flow distribution. Extended‐length intake fish guidance screens did not reduce survival. However, the sources of injury somewhat differed with depth; probable pressure and shear‐related injuries were common on fish entrained at mid‐depth, and mechanically‐induced injuries were common at upper depth. Operating conditions that reduce turbulence within the turbine environment may enhance fish survival; however, controlled experiments that integrate turbine flow physics and geometry and the path entrained fish traverse are needed to develop specific guidance to further enhance fish passage survival.  相似文献   

2.
ABSTRACT: Seventy-three in situ primary productivity experiments over a six-month period in hypereutrophic Onondaga Lake near Syracuse, New York, demonstrated variations in the light saturation parameter, Ip, which in part describes the interaction between productivity and light. Substantial variations in Ip were observed (coefficient of variation = 60 percent). Variations in Ip were significantly correlated (greater than 99 percent confidence level) with temperature (°C). An Arrhenius-type relationship (Ip= 1.312 × 1.088 (T-20)) accounted for approximately 37 percent of the variation in Ip and may be appropriate for other systems dominated by green algae.  相似文献   

3.
Phase change materials (PCMs) that can store and release heat energy over the temperature range from 363 to 393 K are crucial for solar absorption cooling, and it is worthy to seek new solid-liquid PCMs candidates that melt and crystallize in this temperature range. In this paper, (E)-3-m-tolylbut-2-enoic acid (mTBEA) was applied as a PCM candidate. Its thermal energy storage properties and thermal stability were systematically investigated. The results showed that mTBEA melted at 382.9 ± 0.5 K and crystallized at about 364 K, with a melting enthalpy (ΔfusH) of 138.4 ± 6.9 J g?1 and showed good long-term cyclic stability and thermal stability. The supercooling of mTBEA was stabilized at about 20 K, indicating that the conservation condition of melted mTBEA could be simple. In addition, the melted mTBEA could release all the absorbed thermal energy upon crystallizing. Besides, mTBEA exhibited good thermal stability for it to be applied as PCM. Hence, mTBEA is a promising PCM candidate for solar absorption cooling. Furthermore, the heat capacity of mTBEA was measured by modulated temperature differential scanning calorimetry (MTDSC) over the temperature range from 198.15 to 431.15 K, and the molar thermodynamic functions, [HT-H298.15]m and [ST-S298.15]m, were calculated based on the fitted molar heat capacity data.  相似文献   

4.
Abstract

In this study, the wind energy potential of Elazig is statistically analyzed based on hourly measured wind speed data over the five-year period from 1998 to 2002. The probability density distributions are derived from cumulative distribution functions. Two probability density functions are fitted to the measured probability distribution on a yearly basis. The wind energy potential of the location is studied based on the Weibull and Rayleigh distributions. It was found that the numerical values of both Weibull parameters (k and c) for Elazig vary over a wide range. The yearly values of k range from 1.653 to 1.878 with an average value of 1.819, while those of c are in the range of 2.757–2.994 m/s with an average value of 2.824 m/s. In addition, yearly mean wind speed and mean power density of Elazig is found as 2.79 m/s and 38.76 W/m2, respectively. The wind speed distributions are represented by Weibull distribution and also by Rayleigh distribution, with a special case of the Weibull distribution for k = 2. As a result, the Rayleigh distribution is found to be suitable to represent the actual probability of wind speed data for Elazig.  相似文献   

5.
Epigeic earthworms (Oligochaeta) have been appeared as key organisms to convert organic waste resources into value-added products, i.e., vermicompost and worm biomass. The assessment of reproduction potential of composting earthworm may be beneficial for large-scale earthworm production. Although, the waste minimizing potential of Perionyx excavatus and Perionyx sansibaricus is well proved, but little information is available about their fecundity rate. In this study, the efforts have been made to explore the growth and reproduction biology of P. excavatus and P. sansibaricus, using cattle waste solid as culture substrate, under laboratory conditions. Earthworms were weighed weekly and number of cocoons produced per week assessed. Biomass productions, fecundity, maturation, natality all were significantly different between P. excavatus and P. sansibaricus. The highest mean individual biomass was 767.7 ± 18.4 mg and 612.6 ± 20.6 mg, respectively in P. sansibaricus and P. excavatus. However, the highest cocoon numbers occurred in P. excavatus (492.3 ± 13.6), significantly higher than P. sansibaricus (269.6 ± 17.1). Fecundity was slightly different in both species: 1.38 ± 0.77 cocoons adult worm−1 week−1 (P. excavatus) and 1.58 ± 0.74 cocoons adult worm−1 week−1 (P. sansibaricus). The hatchling success rate (%) was highest in P. excavatus. Overall natality (juveniles adult−1 week−1) was highest in P. sansibaricus (1.52) than P. excavatus (1.26), which suggests that P. sansibaricus may be a better candidate for rapid propagation of earthworms in cattle waste solid.  相似文献   

6.
ABSTRACT: Algorithms for Landsat MSS digital data are needed to reduce the necessity of calibrating each Landsat scene if these data are to be useful in monitoring programs for surface suspended sediments. In this study digital data were extracted from 16 Landsat Multispectral Scanner (MSS) scenes collected between March 1987 and August 1988 over Enid Reservoir in North Central Mississippi. These data were converted to radiance and reflectance data for comparison with field measurements of surface suspended sediment concentrations. Concentrations ranged from 2 to 168 mg/1 during the study with only four greater than 100 mg/l. Linear and polynomial regression analyses were used to relate the surface suspended sediment concentrations with radiance and reflectance. Reflectance in MSS band 2 (0.6 to 0.7 μm) and MSS band 3 (0.7 to 0.8 μm) were best related to the surface suspended sediment concentrations with coefficients of determination accounting for 71 percent and 68 percent of the variation in the data, respectively. Regressions with radiance data accounted for 36 percent (band 2) or less of the variation. Logarithmic transformations of either reflectance or sediment concentrations increase the coefficients of determination for MSS band 2 reflectance data to 81 percent. Regressions between the ratio of MSS band 1 to MSS band 2 reflectances and concentrations also accounted for 80 percent of the variation. An equation Loge SS (mg/l) = 9.21R½+ 2.71R½2 + 8.45, where S is surface suspended sediment concentrations and R1/2 is the ratio of MSS band 1 to MSS band 2 reflectances, provided the best fit to the data with a coefficient of determination of 0.82. This equation is essentially the same as an algorithm proposed by Topliss et at. (1990), for estimating surface suspended sediment concentrations in Canadian coastal waters. These equations for Enid Reservoir and Canadian waters suggest that it may be possible to develop an algorithm for widespread use for estimating surface suspended sediments.  相似文献   

7.
Regression relationships were developed between summer mean total phosphorus (P) concentrations in near-surface water and both chlorophyll a concentrations and Secchi disc transparency for Puget Sound region lakes. Total P concentrations in the lakes studied ranged from 7 to 66 μ/L. The relationship between total P and chlorophyll a, based on data from 69 lakes, explained 57 percent of the variance in chlorophyll a. Predicted chlorophyll a concentrations and 95 percent confidence intervals ranged from 1 +3-0.5μg/L for 7 μg/L P to about +35-10μ/L for 66 μ/L P. The relationship between total P and Secchi disc, based on data from 71 lakes, explained 53 percent of the variance in Secchi disc. Predicted Secchi disc transparencies and 95 percent confidence intervals ranged from 5.5 +5.5-3.0 m for 7 μ/L P to 1.4 +1.5-0.7 m for 66 μ/L P.  相似文献   

8.
Rock riprap is one of the most widely used erosion control methods for protecting embankments, levees, spillways, and instream structures subjected to overtopping flow conditions. At least 21 stone‐sizing relationships exist to determine the median stone size of a protective riprap layer based on the results of 96 overtopping, laboratory experiments. Test parameters include median stone size, slope, unit discharge, coefficient of uniformity, and riprap layer thickness. A regression analysis was performed relating the observed median stone size to the predicted median stone size to each of the 21 relationships, yielding a coefficient of determination (R2) and percent error for the full spectrum of data. Zonal (partial spectrum of rock sizes) and complexity analyses were also conducted for each relationship. It was resolved that the Khan and Ahmad, and Chang relationships best aligned with the composite dataset. The predictive expressions by Olivier, Hartung and Scheuerlein, Knauss, Maynord, Abt and Johnson, and Siebel yield a noteworthy second tier of stone‐sizing relationships for overtopping conditions.  相似文献   

9.
ABSTRACT: Snails, Goniobasis livescens (Menke), were exposed to acutely sublethal concentrations of p-nitrophenol and the lampricide, 3-triflourmethyl-4 nitrophenol(TFM), and then to acutely lethal thermal shocks. The same species were also exposed to acutely sublethal concentrations of zinc followed by exposure to acutely lethal concentrations of p-nitrophenol; and to acutely sublethal concentrations of TFM followed by exposure to acutely lethal concentrations of zinc. Brown trout, Salmo trutta, were exposed to acutely sublethal concentrations of TFM and then to an acutely lethal thermal shock. Results of these experiments indicate that prior exposure to acutely sublethal toxicant concentrations may reduce survival time for a subsequent exposure to acutely lethal concentrations of a second toxicant (e.g., snails exposed to Zn++ then p-nitrophenol) but neither prior or concomitant exposure to acutely sublethal toxicant concentrations insures that the median survival time for a lethal exposure will be significantly altered (e.g., snails exposed to 0.2 × 48 hour LC50 for TFM then Zn++). However, some acutely sublethal concentrations of a toxicant may significantly alter survival time of snails to a lethal concentration of a different toxicant (e.g., exposure to 0.4 × 48 hour LC50 TFM then a lethal dose of Zn++). The brown trout exposed to an acutely sublethal concentration of TFM and then an acutely lethal thermal shock did have significantly altered survival patterns.  相似文献   

10.
Understanding temperatures used by hibernating bats will aid conservation and management efforts for many species. A limestone mine with 71 km of passages, used as a hibernaculum by approximately 30,000 bats, was visited four times during a 6-year period. The mine had been surveyed and mapped; therefore, bats could be precisely located and temperatures (T s) of the entire hibernaculum ceiling accurately mapped. It was predicted that bats should hibernate between 5 and 10°C to (1) use temperatures that allow a near minimal metabolic rate, (2) maximize the duration of hibernation bouts, (3) avoid more frequent and prolonged arousal at higher temperatures, (4) avoid cold and freezing temperatures that require an increase in metabolism and a decrease in duration of hibernation bouts or that could cause death, and (5) balance benefits of a reduced metabolic rate and costs of metabolic depression. The distribution of each species was not random for location (P < 0.000) or T s (P < 0.000). Myotis sodalis (Indiana bat) was most restricted in areas occupied, hibernating in thermally stable yet cold areas ( = 8.4 ± 1.7°C); 99% associated with cement block walls and sheltered alcoves, which perhaps dampened air movement and temperature fluctuations. Myotis lucifugus (little brown myotis) hibernated in colder, more variable areas ( = 7.2 ± 2.6°C). Myotis septentrionalis (northern myotis), Pipistrellus subflavus (eastern pipistrelle), and Eptesicus fuscus (big brown bat) typically hibernated in warm, thermally stable areas ( = 9.1 ± 0.2°C, = 9.6 ± 1.9°C, and = 9.5 ± 1.5°C, respectively). These data do not indicate that hibernacula for M. sodalis, an endangered species, should be manipulated to cool below 5°C.  相似文献   

11.
ABSTRACT: Vertical attenuation of photosynthetically active radiation (PAR) in clear waters of central Florida theoretically can vary almost 50 percent during a sunny summer day as a result of changing solar elevation. We used a simple formula to partially adjust the attenuation coefficient in Tampa Bay and Charlotte Harbor for changing solar elevation of the direct beam and then used multiple regression analysis to estimate the relative contribution of different water properties or constituents to the adjusted attenuation coefficient, kadj. Color, on an average, was responsible for 18 percent of kadj, chlorophyll a for 21 percent, nonchiorophyll suspended matter for 55 percent, and seawater for the remaining 6 percent. In both estuaries, kadj increased with decreasing salinity as a result of freshwater runoff adding color, suspended matter, and nutrients. Nutrients affected attenuation by stimulating phytoplankton growth and increasing concentrations of chlorophyll a. Reduced nutrient loading to upper Tampa Bay (Hilisborough Bay) in the early to mid-1980's appears to have decreased concentrations of chlorophyll a, increased water clarity, and increased seagrass recolonization. Assuming other attenuating substances remained unchanged, the decrease in the average concentration of chlorophyll a from 30 to 15 μg L?1 would correspond to an increase in the depth of light penetration necessary for seagrass survival (>10 percent incident light) from 1.0 to 1.5 m, which, on a relatively flat sea bed (slope of 2 m/km), would increase the area potentially available for seagram recolonization by 0.25 km2/km of shoreline.  相似文献   

12.
ABSTRACT: Resolution of the input GIS data used to parameterize distributed‐parameter hydrologic/water quality models may affect uncertainty in model outputs and impact the subsequent application of model results in watershed management. In this study we evaluated the impact of varying spatial resolutions of DEM, land use, and soil data (30 × 30 m, 100 × 100 m, 150 × 150 m, 200 × 200 m, 300 × 300 m, 500 × 500 m, and 1,000 × 1,000 m) on the uncertainty of SWAT predicted flow, sediment, NO3‐N, and TP transport. Inputs included measured hydrologic, meteorological, and watershed characteristics as well as water quality data from the Moores Creek watershed in Washington County, Arkansas. The SWAT model output was most affected by input DEM data resolution. A coarser DEM data resolution resulted in decreased representation of watershed area and slope and increased slope length. Distribution of pasture, forest, and urban areas within the watershed was significantly affected at coarser resolution of land use and resulted in significant uncertainty in predicted sediment, NO3‐N, and TP output. Soils data resolution had no significant effect on flow and NO3‐N predictions; however, sediment was overpredicted by 26 percent, and TP was underpredicted by 26 percent at 1,000 m resolution. This may be due to change in relative distribution of various hydrologic soils groups (HSGs) in the watershed. Minimum resolution for input GIS data to achieve less than 10 percent model output error depended upon the output variable of interest. For flow, sediment, NO3‐N, and TP predictions, minimum DEM data resolution should range from 30 to 300 m, whereas minimum land use and soils data resolution should range from 300 to 500 m.  相似文献   

13.
Soil erosion from agricultural land use runoff is a major threat to the sustainability of soil composition and water resource integrity. Sugarcane is an important cash and food security crop in South Africa, subjected to an intensive soil erosion, and consequently, severe land degradation. This study aimed to investigate soil erosion and associated soil and cover factors under rainfed sugarcane, in a small catchment, KwaZulu‐Natal, South Africa. Three replicated runoff plots were installed at different slope positions (down, mid and upslope) within cultivated sugarcane fields to monitor soil erosion during the 2016–2017 rainy season. On average, annual runoff (RF) was significantly greater from 10 m2 plots with 1163.77 ± 2.63 l/m/year compared to 1 m2 plots. However, sediment concentration (SC) was significantly lower in 10 m2 (0.34 ± 0.04 g/l) compared to 1 m2 (6.94 ± 0.24 g/l) plots. The annual soil losses (SL) calculated from 12 rainfall events was 58.36 ± 0.77 and 8.84 ± 0.20 t/ha from 1 m2 and 10 m2 plots, respectively. The 1 m2 plot, SL (2.4 ± 1.41 ton/ha/year) in the upslope experienced 33% more loss than the midslope and 50% more loss than the downslope position. SL was relatively lower from the 10 m2 plots than the 1 m2 plots, which is explained by high sediment deposition at the greater plot scale. SL was negatively correlated with the soil organic carbon stocks (r = ?0.82) and soil surface cover (r = ?0.55). RF decreased with the increase of slope gradient (r = ?0.88) and soil infiltration rate (r = ?0.87). There were considerable soil losses from cultivated sugarcane fields with low organic matter. These findings suggest that to mitigate soil erosion, soil organic carbon stocks and vegetation cover needs to be increased through appropriate land management practices, particularly in cultivated areas with steep gradients.  相似文献   

14.
The Potential Use of Chicken-Drop Micro-Organisms for Oil Spill Remediation   总被引:2,自引:0,他引:2  
An examination of chicken-drop micro-organisms for oil spill remediation is presented in this work. The chicken droppings contained aerobic heterotrophs (1.2×108 CFU g–1), total fungi (3.4×104 CFU g–1) and crude oil (transniger pipeline crude, TNP) degrading bacteria (1.5×106 CFU g–1). The crude oil degraders were identified as species of Micrococcus, Bacillus, Pseudomonas, Enterobacter, Proteus, Klebsiella, Aspergillus, Rhizopus, and Penicillium. Pseudomonas aeruginosa CDB-06 and species of Bacillus CDB-08 and Penicillium CDF-10 degraded the crude oil at exceedingly high rates. Pseuedomonas aeruginosa CDB-06 degraded 65.5 percent of the crude oil after 16 days, while Bacillus sp. CDB-08, and Penicillium sp. CDF-10 degraded 65.3 percent, and 53.3 percent, respectively of the crude oil over the same period. The chicken droppings also had a pH 7.3, 18.5 percent moisture content, 2.3 percent total nitrogen, and 0.5 percent available phosphorus. Addition of oil polluted soil (10 percent (v/w) pollution level) with chicken droppings enhanced degradation of the crude oil in the soil. 68.2 percent of the crude oil was degraded in the soil amended with chicken droppings, whereas only 50.7 percent of the crude oil was degraded in the unamended soil after 16 days. The amendment raised the acidic reaction (pH 5.7) of the oil-polluted soil to alkaline (pH 7.2) within 16 days. Chicken droppings could, therefore, be used in an integrated oil pollution abatement program.  相似文献   

15.
ABSTRACT: Alum treatment of a shallow lake, with mean depth 2 m and area 137 ha, curtailed internal loading of P for at least one ear. Mean summer total P and chl a decreased from 76 and 27μg l?1, respectively, in 1978 before treatment. to 29 and 14 μ l?1, while mean summer Sed transparency increased from 1.6 to 2.2 m and blue green algae were no longer dominant. Macrophyte biomass and distribution retuned during the post-alum year, 1980-1981, to previous levels after a 1979 four-month lake level drawdown had reduced biomass by 84 percent The improved transparency, resulting from the decrease in chl a following treatment, could encourage greater biomass of macrophytes in the deeper area of the lake. Recovery of macrophyte biomass to predrawdown levels may restore internal loading of P through enrichment of deep water sediments during winter dieback and decomposition.  相似文献   

16.
Textile mill waste can be vermicomposted if it is mixed in the range of 20–30% with cow dung. This article reports the effect of inoculation, of nitrogen fixing Azotobacter chroococcum strain; Azospirillum brasilense strain and phosphate solubilizing Pseudomonas maltophila, on nitrogen and phosphorus content of vermicomposts prepared from cow dung (CD) and cow dung spiked textile mill sludge (CD + STMS). The CD vermicompost was more supportive to the growth and multiplication of all the three bacteria than CD + STMS vermicompost. In Azotobacter chroococcum treated vermicomposts maximum nitrogen content was recorded between 45 and 60 days [CD␣vermicompost (25.9 ± 0.45 g kg−1) and CD + STMS vermicompost (20.6 ± 0.62 g kg−1)] followed by Azospirillum brasilense inoculation [CD vermicompost (19.4 ± 0.60 g kg−1) and CD + STMS vermicompost (18.6 ± 0.17 g kg−1)]. Phosphorus content in Pseudomonas maltophila inoculated CD vermicompost was 20.8 ± 0.20 g kg−1 and CD + STMS vermicompost was 13.4 ± 0.45 g kg−1 after 75th day of inoculation.  相似文献   

17.
ABSTRACT: A hydroelectric lake on the Oconee River in central Georgia was sampled on a quarterly basis for four years to determine the impact of three insecticides on the pesticide loading of fish. The insecticides carbofuran (2,3,-dihydro-2,2-dimethyl-7-benzofuranyl methyl-carbamate), fenvalerate [cyano(3-phenoxyphenyl)methyl 4-chloro alpha (1-methylethyl)benzeneacetate], and azinphosmethyl [0,0-Dimethyl S-(4-oxo-1,2,3-benzotriazin-3-(4H)-ylmethyl phosphorodithioate] were used to control cone and seed insects on a pine seed orchard that is adjacent to Lake Oconee. Fish populations in areas of the lake that receive runoff from treated and untreated portions of the seed orchard were sampled using gill nets. Water and fish samples were collected monthly in 1981–1983 and quarterly in 1984. Species collected included carp (Cyprinus carpio), sucker (Catostomus spp., Erimyzon spp., Moxostoma spp., Minytrema spp.), bass (Micropterus spp.), channel catfish (Ictalurus punctatus), spotted gar (Lepisosteus spp.), and bluegill sunfish (Lepomis macrochirus). Few carbofuran residues (< 7 percent of fish samples contained detectable residues) and no azinphosmethyl or fenvalerate residues were detected despite measured inputs into the lake after insecticide application. Persistent agricultural insecticides including dieldrin, lindane, DDT, and toxaphene were detected in 32, 36, 58, and 83 percent of sampled fish, respectively. Screening for 20 other insecticides resulted in no detection of residues at a detection limit of 30–100 μg kg-1.  相似文献   

18.
Waste from wastewater treatment plants (WWTP) for Helianthus annuus L. production may be a viable solution to obtain biodiesel. This study achieved two objectives: assess the agronomical viability of waste (wastewater and sludge) from the Alcázar de San Juan WWTP in central Spain for H. annuus L. production; use H. annuus L. seeds grown in this way to obtain biodiesel. Five study plots, each measuring 6 m × 6 m (36 m2), were set up on the agricultural land near the Alcázar de San Juan WWTP. Five fertilizer treatment types were considered: drinking water, as the control; treated wastewater; 10 t ha?1 of air-dried sewage sludge; 20 t ha?1 of air-dried sewage sludge; 0.6 t ha?1 of commercial inorganic fertilizer. Soil, irrigation water, sewage sludge, crop development and fatty acid composition in achenes oil were monitored. The 20 t ha–1 dose of sewage sludge proved effective to grow H. annuus L. with similar results to those grown with a commercial fertilizer. However, precautions should be taken when irrigating with wastewater because of high salinity and nutrient deficiency. Sunflower oil was composed mostly of linoleic and oleic acid. The remaining fatty acids were linolenic, estearic, nervonic, palmitoleic, and palmitic.  相似文献   

19.
ABSTRACT: Models for the prediction of chlorophyll a concentrations were developed and tested using data on 223 Florida lakes. A statistical analysis showed that the best model was log (Chl a) =?2.49 + 0.269 log (TP) + 1.06 log (TN) or log (Chl a) =?2.49 + 1.06 log (TN/TP) + 1.33 log (TP) where Chl a is the chlorophyll a concentration (mg m-3), TP is the total phosphorus concentration (mg m-3) and TN is the total nitrogen concentration (mg m-3). The model yields unbiased estimates of chlorophyll a concentrations over a wide range of lake types and has a 95 percent confidence interval of 29–319 percent of the calculated chlorophyll a concentrations. Other models, especially the published Dillon-Rigler and Jones-Bachmann phosphorus-chlorophyll models, are less precise when applied to Florida lakes. The data support the hypothesis that nitrogen is an important limiting nutrient in hypereutrophic lakes.  相似文献   

20.
ABSTRACT: A free water surface (FWS) constructed wetland was installed at a dairy in Glendale, Arizona, to study the potential of such a wetland to remove nitrogen (N) from wastewater. The study objectives were: (1) to determine N removal from the wastewater, and (2) to evaluate N accumulation in soil and plant tissues. The system consisted of eight cells (70 × 9 × 1.5 m) planted with Typha domingensis, Scirpus validus, and Phragmites australis. The four cells in series were lined with plastic, and the four cells in a parallel series were lined with clay. Cells received approximately 180 m3/d of partially treated dairy effluent. Plant tissues and soil samples were collected above and below ground from 24 locations during one year. Total N removal from wastewater was about 17 percent. Clay‐lined cells accumulated more N in the soil and less N in plant biomass compared with plastic lined cells. Plant biomass accounted for approximately 60 percent of total N accumulated in cells with dense plant communities. Ninety percent of accumulated soil N was organic. Total N accumulated in soil reached a maximum (1,100 mg/kg) eight months after the introduction of wastewater.  相似文献   

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