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1.
The fallout radionuclide cesium-137(137 Cs) has been widely employed as a tracer for assessment of soil loss from thick uniform soils;however,few studies have been conducted on thin stony soils on slopes underlain by carbonate rocks which are widely distributed in karst areas.Information derived from 137 Cs measurement of soil samples collected along a carbonate rock slope with thin stony soil where neither soil erosion nor deposition occurred was used to investigate the characteristics of 137 Cs redistribution in a karst area of Southwest China.The results indicated that the 137 Cs inventories of the surface soil on the slope studied were much lower than that of the local 137 Cs reference inventory and the 137 Cs activities were much higher than those on slopes with thick uniform soils.The spatial distribution of 137 Cs inventories was characterized by considerable variation.The high 137 Cs depletion in the stony soil of the slope studied was mainly because a considerable proportion of the fallout input of 137 Cs could be lost with runoff and the dissolution of carbonate particles in the soil promoted the loss of 137 Cs.These demonstrated that the rates of soil loss could not be estimated from the degree of depletion of the 137 Cs inventory relative to the local reference inventory for the thin stony soil of the rocky slope underlain by carbonate rocks in the study area in the way that has been widely used in areas with thick uniform soils.  相似文献   

2.
Soil salinity and hydrologic datasets were assembled to analyze the spatio-temporal variability of salinization in Fengqiu County, Henan Province, China, in the alluvial plain of the lower reaches of the Yellow River. The saline soil and groundwater depth data of the county in 1981 were obtained to serve as a historical reference. Electrical conductivity (EC) of 293 surface soil samples taken from 2 km × 2 km grids in 2007 and 40 soil profiles acquired in 2008 was analyzed and used for comparative mapping. Ordinary kriging was applied to predict EC at unobserved locations to derive the horizontal and vertical distribution patterns and variation of soil salinity. Groundwater table data from 22 observation wells in 2008 were collected and used as input for regression kriging to predict the maximum groundwater depth of the county in 2008. Changes in the groundwater level of Fengqiu County in 27 years from 1981 to 2008 was calculated. Two quantitative criteria, the mean error or bias (ME) and the mean squared error (MSE), were computed to assess the estimation accuracy of the kriging predictions. The results demonstrated that the soil salinity in the upper soil layers decreased dramatically and the taxonomically defined saline soils were present only in a few micro-landscapes after 27 years. Presently, the soils with relatively elevated salt content were mainly distributed in depressions along the Yellow River bed. The reduction in surface soil salinity corresponded to the locations with deepened maximum groundwater depth. It could be concluded that groundwater table recession allowed water to move deeper into the soil profile, transporting salts with it, and thus played an important role in reducing soil salinity in this region. Accumulation of salts in the soil profiles at various depths below the surface indicated that secondary soil salinization would occur when the groundwater was not controlled at a safe depth.  相似文献   

3.
一个新的土壤重金属竞争吸附等温模型   总被引：3，自引：0，他引：3  
A new competitive adsorption isothermal model (CAIM) was developed for the coexistent and competitive binding of heavy metals to the soil surface. This model extended the earlier adsorption isothermal models by considering more than one kind of ion adsorption on the soil surface. It was compared with the Langmuir model using different conditions, and it was found that CAIM, which was suitable for competitive ion adsorption at the soil solid-liquid surface, had more advantages than the Langmuir model. The new competitive adsorption isothermal model was used to fit the data of heavy metal (Zn and Cd) competitive adsorption by a yellow soil at two temperatures. The results showed that CAIM was appropriate for the competitive adsorption of heavy metals on the soil surface at different temperatures. The fitted parameters of CAIM had explicit physical meaning. The model allowed for the calculation of the standard molar Gibbs free energy change, the standard molar enthalpy change, and the standard molar entropy change of the competitive adsorption of the heavy metals, Zn and Cd, by the yellow soil at two temperatures using the thermodynamic equilibrium constants.  相似文献   

4.
Excess calcium(Ca) in soils of semi-arid and arid regions has negative effects on soil structure and chemical properties, which limits the crop root growth as well as the availability of soil water and nutrients. Quantifying the spatial variability of soil Ca contents may reveal factors influencing soil erosion and provide a basis for site-specific soil and crop management in semi-arid regions. This study sought to assess the spatial variability of soil Ca in relation to topography, hydraulic attributes, and soil types for precision soil and crop management in a 194-ha production field in the Southern High Plains of Texas,USA. Soils at four depth increments(0–2, 0–15, 15–30, and 30–60 cm) were sampled at 232 points in the spring of 2017. The Ca content of each sample was determined with a DP-6000 Delta Premium portable X-ray fluorescence(PXRF) spectrometer. Elevation data was obtained using a real-time kinematic GPS receiver with centimeter-level accuracy. A digital elevation model(DEM) was derived from the elevation data, and topographic and hydraulic attributes were generated from this DEM. A generalized least-squares model was then developed to assess the relationship between soil Ca contents of the four layers and the topographic and hydraulic attributes. Results showed that topographic attributes, especially slope and elevation, had a significant effect on soil Ca content at different depths(P 0.01). In addition, hydraulic attributes, especially flow length and sediment transport index(STI), had a significant effect on the spatial distribution of soil Ca. Spatial variability of soil Ca and its relationships with topographic and hydraulic attributes and soil types indicated that surface soil loss may occur due to water or wind erosion, especially on susceptible soils with high slopes. Therefore, this study suggests that the application of PXRF in assessing soil Ca content can potentially facilitate a new method for soil erosion evaluation in semi-arid lands. The results of this study provide valuable information for site-specific soil conservation and crop management.  相似文献   

5.
This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.  相似文献   

6.
Through the long-term plot studies plot studies on the precipitation distribution in the evergreen broad-leaved forest ecosystem in Hangzhou for two years,it was indicated that the pattern of precipitation distribution included larger amounts of penetration water and stemflow and a lower amount of interception water.The results revealed that the main factors to infulence the percentages of penetration and stemflow were the air temperature and the leaf area of the forest.The quantity of seepage through the litter layer was much larger than that through the soil layers which decreased sharply with soil depth.The output of water from the ecosystem by surface runoff and deep infiltration through the soil was much lower,only being 5.20 percent of the rainfall,while the water evapotranspiration loss was as large as more than 90 percent of it.The losses by the soil evaporation and plant evapotranspiration were the largest part of output in this forest ecosystem.  相似文献   

7.
土壤抗生素污染对小麦生长和光合参数的影响   总被引：5，自引：0，他引：5  
Extensive worldwide use of oxytetracycline (OTC),a member of the tetracyclines,has resulted in its accumulation in soils,posing a potential risk to food production and safety.A pair of OTC-sensitive (Heyou 1) and OTC-tolerant (Yannong 21) wheat (Triticum aestivum L.) cultivars was compared hydroponically at 0.01,0.02,0.04,and 0.08 mmol L-1 OTC in terms of wheat growth and photosynthesis.Biomass and shoot length decreased significantly with the addition of OTC,with the decreases in dry biomass and shoot length being 5.61%-13.75% and 3.33%-8.57% larger,respectively,for Heyou 1 than Yannong 21.Photosynthesis of Heyou 1 was suppressed by OTC as indicated by the significant decreases in photosynthetic rate (PN),transpiration rate (TR),and stomatal conductance (GS) and the significant increase in intercellular CO 2 concentrations (CI),at all OTC levels.Stomatal limitation (LS) and water use efficiencies (WUE) of Heyou 1 also increased significantly,but not at 0.08 mmol L-1 OTC.However,photosynthesis of Yannong 21 was suppressed by OTC only at high OTC levels from 0.02 to 0.08 mmol L-1 as indicated by the decreases in PN,GS,TR,and LS;at 0.01 mmol L-1 OTC,PN,CI,GS,and TR significantly increased.It was noted that WUE of Yannong 21 was not affected by OTC addition.The results from this hydroponic test suggested that OTC had a potential risk to crop growth through inhibition of photosynthesis,requiring further confirmation with soil tests.  相似文献   

8.
分形模型在利用颗粒分布数据评价土壤持水性质中的应用   总被引：4，自引：0，他引：4  
LIU Jian-Li  XU Shao-Hui 《土壤圈》2002,12(4):301-308
Soil water retention characteristics are the key information required in hydrological modeling.Frac-tal models provide a practical alternative for indirectly estimating soil water retention characteristics from particle-size distribution data.Predictive capabilities of three fractal models,i.c.,Tylcr-Wheatcraft model,Rieu-Sposito model,and Brooks-Corey model,were fully evaluated in this work using experimental data from an international database and literature.Particle-size distribution data were firstly interpolated into 20 classes using a van Genuchten-type equation.Fractal dimensions of the tortuous pore wall and the pore surface were then calculated from the detailed particle-size distribution and incorporated as a parameter in fractal water retention models.Comparisons between measured and model-estimated water retention cha-racteristics indicated that these three models were applicable to relatively different soil textures and pressure head ranges.Tyler-Whcatcraft and Brooks-Corey models led to reasonable agreements for both coarse-and medium-textured soils,while the latter showed applicability to a broader texture range.In contrast,Rieu-Sposito model was more suitable for fine-textured soils.Fractal models produced a better estimation of water contents at low pressure heads than at high pressure heads.  相似文献   

9.
Ammonium fixation and adsorption experiments were conducted to study the effect of potassium on ammonium fixation into interlasyer of vermiculite and ammonium adsorption at the surface of vermiculite both in the binary (NH4^ -Ca^2 ) and ternary (NH4^ -Ca^2 ) ystems.In the ammonium fixation experiment,5 mmol NH4^ kg^-1 was added alone,or after,before of simultaneously with 5 mmol K^ kg^-1 to the vermiculite (Vermiculite:solution=1:1),and the incubation was conducted for 3 days under constant 20℃，In the adsorption experiment ,after addition of 10 mmol Ca^2 L^-1 as matrix ions ,either,NH4^ alone with a concentration series from 0.1 to 5.0 mmol NH4^ L^-1(binary exchange system of NH4^ and Ca^2 )of NH4^ together with 5 mmol K^ L^-1(ternary exchange system of NH4^ ,K^ and Ca^2 ) was added to vermiculte at a vermiculite to solution ratio of 1:10 for 24-h equlibrium.The results of the fixtion experiment showed that the presence of K^ increased NH4^ fixation for all the treatments,regardless of the addition orders.For ammonium adsorption a linear realtionship between activtiy ratios of NH4^ to Ca^2 and Mg^2 in the equilibrium solutions(ARNH4)and incereases of exchangeable NH4^ at the surface of vermiculite after 24 h equilibrium (△Ex-NH4^ )was shown for almost the whole concentration ranges tested.Compared With the binary system ,the slope of the curve of the ternary system was steeper,indicaitng a more intensive adsorption of NH4^ in the presence of K^ ,It was demonstrated that K^ did not reduce the ammonium fixation into the interlayer and ammonium adsorption at the surface of vermiculite ,which indicated that, under the experimental conditions of this study,K^ did neither occupy the sites for NH4^ -fixation in the interlayer nor the sites for NH4^ -adsorption at the surface of vermiculite.  相似文献   

10.
普通克里格法在土壤有机碳制图中的应用   总被引：1，自引：0，他引：1  
The quantification of the pattern and spatial distribution of soil organic carbon (SOC) is fundamental to understand many ecosystem processes.This study aimed to apply ordinary kriging (OK) to model the spatial distribution of SOC in a selected part of Zambia.A total of 100 soil samples were collected from the study area and analyzed for SOC by determining soil oxidizable carbon using the Walkley-Black method.An automated fitting procedure was followed when modeling the spatial structure of the SOC data with the exponential semivariogram.The results indicated that the short range spatial dependence of SOC was strong with a nugget close to zero.The spatial autocorrelation was high to medium with a nugget to sill ratio of 0.25.The root mean square error of the predictions was 0.64,which represented 58.18％ of the mean observed data for SOC.It can be concluded that the generated map could serve as a proxy for SOC in the region where evidence of spatial structure and quantitative estimates of uncertainty are reported.Therefore,the maps produced can be used as guides for various uses including optimization of soil sampling.  相似文献   

11.
Nickel (Ni) is an ubiquitous, naturally occurring metalthat is associated with metal mining and other industrialactivities. Despite elevated Ni concentrations reportedfor many industrial receiving waters, Ni receives littleresearch attention addressing factors influencing itstoxicity to freshwater fish. This study examined theinfluence of water hardness, pH, and total suspended solids(TSS) in soft, reconstituted water on Ni toxicity to larvalfathead minnows (Pimephales promelas). Increasingwater hardness from 20 to 140 mg L-1 (as CaCO3) reduced acute Ni toxicity by 5-fold (96-h LC50s 0.45 and 2.27 mg Ni L-1, respectively). Low pH had a slight protective effect against Ni toxicity relative to neutral pH conditions. At pH 5.5, the 96-h LC50 was 0.69 mg Ni L-1, compared to 0.54 mg Ni L-1 at pH 7.0. However,Ni toxicity was significantly reduced at pH 8.5 where the 96-h LC50 was 2.21 mg Ni L-1. These results were explainedon the basis of Ni speciation. Total suspended solids also reduced Ni toxicity (expressed as 96-h LC50s) from 0.35 to 1.12 mg Ni L-1 over a TSS range of 10 to 100 mg L-1.This reduction of toxicity due to TSS is significant becausemine effluents often have a combination of elevated TSS andmetals. The ameliorative effect of TSS was not as significantas high hardness or pH probably because there is a TSS threshold, after which physical irritation to fish gills counteracts any protective effect conferred by TSS. This finding is relevant to choices made in design of mine effluenttreatment systems; i.e., there may be an optimum range ofTSS concentrations that protect aquatic biota againsteffects of metals that remain after treatment.  相似文献   

12.
Enrichment ratios (ER) are widely used to predict loss of sorbed nutrients or pesticides with runoff sediment, while ER is frequently neglected in studies which quantify past erosion from global fallout 137Cs losses. The ER of 137Cs (ER- 137Cs) in the soil loss and the subsequent depletion of 137Cs at the soil surface were determined for eight small watersheds (1.6–16.8 ha) with different soils and land use. Due to preferential loss of the clay fraction, the upper 5 mm of the soil surface was significantly depleted of 137Cs after a heavy storm. A total of 31 watershed-events were investigated with soil losses ranging between 1.2 and 480 kg-ha?1 and sediment concentrations between 1.98 and 54.1 g?L?1 The correspondent ER-137Cs (mean: 1.72, range: 0.40–4.95) was positively correlated to the ER of clay, organic carbon, total nitrogen and calcium-acetate-lactate-extractable phosphorus (PCAL). A close correlation between ER-137Cs and ER-PCAL was also found for sediment samples of detention ponds, where most of the ER values were less than 1.0 due to depletion. Therefore, ER-PCAL seems to be a suitable estimate of ER-137Cs for both, erosion and deposition processes. Our findings strongly support the need for considering ER-137Cs, when ,37Cs data are used to assess rates and pattern of soil redistribution. Otherwise, soil loss will be overestimated in a range of about factor 2 in many cases.  相似文献   

13.
Acute exposure of the central stoneroller minnow to sublethal levels of phenol was found to decrease the ability of this species to tolerate hypoxic conditions as indicated by the dissolved oxygen (DO) concentration at which loss of equilibrium occurred. For fishes acclimated at 7.5 °C, loss of equilibrium occurred at progressively higher DO levels as the phenol exposure concentration was increased from 0 to 12 mg phenol L?1. Mean DO concentrations at which loss of equilibrium occurred ranged from 2.33 ± 0.10 mg O2 L?1. for the control group (0 mg phenol L?1. to 2.76 ± 0.14 mg O2 L?1. (at 12 mg phenol L?1. Loss of equilibrium also occurred at progressively higher DO levels in fish acclimated at 23 °C, but only after an initial decrease among the 6 mg phenol L?1. test fish in the loss of equilibrium DO concentration. At 23 °C, loss of equilibrium occurred at DO levels ranging from 1.3 ± 0.09 mg O2 L?1. (6 mg phenol L?1. to 2.33 ± 0.16 mg O2 L?1. (12 mg phenol L?1. These data indicate that acute exposures to sublethal levels of phenol can have significant effects on the ability of the stoneroller minnow to tolerate conditions of low DO, and the results agree with the previously reported relationship between phenol toxicity and DO levels.  相似文献   

14.
Mine tailings can provide a long-term source of environmental contamination. Lead-zinc mine tailings can represent a source of toxic elements-Pb and Zn through mobilization into surface water, and then into downstream rivers. Previous studies have shown that migration of heavy metals can be mitigated by carbonate rock. This research investigates the characterization of heavy metals and sulphur isotope in a downstream river of the Shanshulin Pb-Zn mine, which is located in Guizhou province in China, a typical carbonate area in the world. A slight alkalinity (pH > 8) of the river water is maintained owing to the carbonate rich country rocks. The results of this study show that heavy metals in water can be strongly adsorbed by suspended solids and therefore decrease more quickly than in sediments. Pb and Zn contents in water close to the waste pile are 6780 μg L-1 and 324 μg L-1 (Pb and Zn in water not affected by mine waste piles are only 3.71 μg L-1 and 11.6 μg L-1), respectively, meaning that the water is severely contaminated by the pile. Thirty kilometers downstream Pb and Zn contents in water drop quickly to 3.15 μg L-1 and 16.4 μg L-1. In contrast, Pb and Zn contents in sediment close to the waste pile are 4553 mg kg-1 and 7971 mg kg-1, respectively, and are still high 30 km downstream with measurements of 3334 mg kg-1 and 7268 mg kg-1 , respectively (Pb and Zn contents in sediment not affected by mine waste piles are only 20 mg kg-1 and 120 mg kg-1). This indicates that the impact of tailings on the sediment can be much further than on water. In sediment, Pb exists mostly as carbonate and oxide fractions, Zn mostly as sulfide+organic fraction, and Cu mostly as sulfide+organic, residual and carbonate fractions. Sulphur characteristics indicate that sulphur in sediment originates from mine tailing, soil and suspended solids in other tributaries, whereas sulphur in water originates from mine tailing dissolution, spring water, rain water and dissolution of gypsum. In conclusion, the environmental impact of mine tailing can be indicated by heavy metals content, sulphur content and sulphur isotope of sediment. On the other hand, heavy metal content, sulphur content or sulphur isotope of water are possibly not good indicators for mine impact due to mitigation of carbonate rocks, sorption of heavy metals, as well as interference of gypsum layers.  相似文献   

15.
Phosphorus (P) transfers may accelerate water eutrophication to waters. Increasing awareness of the role of diffuse P sources motivates land managers in different regions of Europe to undertake conservation programs that place emphasis not only on soil conservation but also on water quality and eutrophication risk. Fertilizer applications and wastes are the main sources of dissolved P in Galicia and in the Atlantic regions of Spain. The aim of this study was to assess the temporal changes in concentration of total P (TP), sedimentary P (SP), and total dissolved P (TDP) and suspended solids at the outlet of an agroforestry catchment located in northwestern Spain. The study datasets range from January 1999 to December 2007, with 992 water samples collected. The water-collection strategy was a stratified point sampling involving more frequent collections when flow was high. Phosphorus contents were assessed by inductively coupled plasma (ICP)–mass spectroscopy (MS), and suspended solids were measured by filtration. The content ranges of the different studied P forms and suspended solids were as follows: TDP between 1 and 672 mg L?1, SP between 1 and 1064 mg L?1, TP between 1 and 1111 mg L?1, and suspended solids between 1 and 1044 mg L?1. A few events of intense precipitation with peaks of TP greater than 200 mg L?1 and in some cases even more than 1000 mg L?1 were responsible for most of the P losses in the catchment studied. TP and SP, TP and suspended solids, and SP and suspended solids showed highly significant correlations during the entire study period, evidencing the erosive origin of P in this catchment.  相似文献   

16.
Attempt has been made to study the treatability of printing ink wastewatergenerated from an Indian currency printing press using coagulation-flocculation process. Coagulant agents, viz. ferrous sulphate, ferric chloride, aluminium sulphate and polyaluminium chloride were studied to select the most suitablecoagulant for effective treatment, and attain the optimum coagulant concentration. Cationic polyeletrolyte in conjunction with the most effective coagulant was also studied to assess its effect on floc settleability. Polyaluminium chloride (PAC) was found to be the most efficient coagulant, achieving removals of colour, suspended solids (SS), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of 95.9–96.5%, 96.5–97.0%, 61.3–65.8%and 54.8–61.8%, respectively at an optimum concentration of 1500 mg L-1. Other coagulants, viz. ferrous sulphate, ferric chloride and aluminium sulphate did not show substantial removals of colour, BOD and COD, except suspended solids in comparison to the performance of PAC. Cationic ploylectrolyte in combination with PAC at an optimum concentration of 1500 mg L-1 of PAC and 1.0 mg L-1 of polyelectrolyte further improved the removal efficiency of various parameters studied, in addition to improving the floc settling rate, and reduction in quantity of sludge generation.Effect of rapid mixing intensity expressed as mean temporal velocity gradient (G), and mixing time (t) on flocculation was also investigated. Rapid mixing at an impeller rotational speed (n) of 300 rpm and mixing time (t) of 60 sec indicated good floc formation, which resulted in achieving velocity gradient of 821 s-1, and was found to be an optimum combination. This was also indicated by relatively high settling velocity of sludge formed and low residual colour in the supernatant. However, slow mixing beyond 5 min, adopted after initial optimum rapid mixing, indicated negligible effect on flocculation.  相似文献   

17.
The toxicity of pure phenol, formaldehyde, and industrial wastewater, containing phenol and formaldehyde, from a resin production plant was evaluated using aquatic organisms from different taxonomic groups. Test organisms included mixed bacterial culture, unicellular green algae Scenedesmus quadricauda (Turp.) Breb., crustacea Daphnia pulex de Geer (daphnids), and fish Oncorhynchus mykiss Call, 1990 (rainbow trout). Formaldehyde was found to be more toxic to the mixed bacterial culture (120h EC50 = 34.1 mg L-1), algae (24h EC50 = 14.7 mg L-1), and crustacea (48h EC50 = 5.8 mg L-1) than phenol. Phenol proved to be more toxic to fish (48h LC50 = 13.1 mg L-1) than to the mixed bacterial culture (120h EC50 = 510 mg L-1), algae (24h EC50 = 403 mg L-1), and crustacea (48h EC50 = 25 mg L-1). The toxicity of the industrial wastewater to the mixed bacterial culture, algae, and crustacea was caused mainly by formaldehyde, but for fish the presence of phenol in the wastewater proved to be the significant reason for toxicity. Differences in sensitivity of the selected test organisms were also observed, with fish and crustacea being the most sensitive species.  相似文献   

18.
The effect of increasing chloride content in nutrient solution on nutrient composition in root environment, interaction of nutrients in leaves and yield of greenhouse tomato cv. ‘Grace F1’ grown in rockwool were searched. In Experiment I (2004–2005) the levels of 15, 30, 60, and 90 mg Cl·L?1 but in Experiment II (2006) 30, 60, 90 and 120 mg Cl·L?1 of nutrient solution were tested. The sources of chloride were water (9.6–10.7 mg Cl·L?1) and calcium chloride (CaCl2·2H2O) but the rest of nutrients and sodium in all treatments were on the same levels. It was found that increasing content of chloride from 15 to 60 mg Cl·L?1 enhanced the total and marketable fruit yield. Within the range of 60 to 90 mg Cl·L?1 the yield was on the optimum level but the content of 120 mg Cl·L?1 declined it. Increasing chloride content in the nutrient solutions was reflected in rising of chlorine content in leaves. The concentration of chloride above 60 mg C·L?1 reduced the content of nitrogen but above 90 mg C·L?1 declined the content of calcium, sulfur and zinc in leaves. The antagonism between Cl:N, Cl:Ca: Cl:S and Cl:Zn was appeared. More variable interaction were between Cl:K and Cl:B. At the low levels of chloride, from 15 to 60 mg Cl·L?1, potassium and boron content were decreased but at the higher ones, from 90 to 120 mg·L?1, these nutrients had increasing course. It was not found out the effect of chloride contents on macro and microelement contents in nutrient solution emitted from drippers however their content upraising in root medium (rockwool). The highest increase was found out for Na 95.1 and 64.9 % (Exp. I and II - respectively), next for Ca (76.0, 70.1 %), Cu (62.5 and 71.0 %), Cl (43.6, 24.4), B (33.3, 21.0 %), N-NO3 (30.4, 49.6 %), Zn (29.5, 32.8 %), S-SO4 (25.9, 25.5 %), K (24.5, 24.1 %), Fe (19.8, 19.2 %), Mn (17.5, 21.3 %) and Mg (14.9, 11.7). Advantageous effect of chloride on tomato yield justified the need to introduce for the practice adequate chlorine nutrition, and recommend to maintain 60 to 90 mg Cl·L?1 in nutrient solution. The best yield appeared when content of chlorine in leaves (8th or 9th leaf from the top) was in the range 0.48-0.60 % of Cl in d. m.  相似文献   

19.
Iron(III)(hydr)oxides can dissolve under reducing soil conditions. Simultaneously, oxide-associated inorganic phosphate is released to the soil solution. In this study, the effect of reducing soil conditions on phosphate leaching from transient waterlogging clayey soil is evaluated. We applied glucose solutions (either 100 or 1000 mg glucose-C L-1) at a steady flow rate of 0.63 mm h-1 to a saturated intact column of structured Alfisol (diam. 0.5 m, height 1.0 m). Effluent concentrations of iron(II) and reactive orthophosphate (Pi) increased slightly during 5 d of low glucose application, reaching values of 2.5 mg Fe L-1, and 0.02 mg PO4-P L-1, respectively. During 10 d of high glucose application, the iron(II) concentration increased to 14 mg Fe L-1 and fluctuations in the Pi-concentration between 0.002 and 0.1 mg PO4-P L-1 were observed. The fluctuations in Pi-concentration are ascribed to interactions between progression of the glucose front, and Pi-mobilization/resorption processes at the walls of macropores. The daily P-losses during low and high glucose applications averaged 0.3 mg PO4-P m-2 d-1, and 0.5 mg PO4-P m-2 d-1, respectively. Comparisons with a parallel topsoil study suggest that subsoil exerts a strong control on leaching – probably via resorption – of Pi mobilized in the topsoil.  相似文献   

20.
Luo  Ancheng  Zhu  Jun  Ndegwa  Pius M. 《Water, air, and soil pollution》2002,140(1-4):219-230
A feasibility study with three pre-conditioning times was carriedout to examine the effect of anaerobic pre-treatment on phosphorus removal by aeration. The results showed that solublephosphorus could be decreased from 120 mg L-1 to about40 mg L-1 within one-day aeration. However, soluble phosphorusconcentration was found not affected by pre-conditioning, butmore pH dependent. Anaerobic pre-treatment significantly increased the uptake of phosphorus by microbes indicated by theincrease in concentration of organic phosphorus fraction. The presence of a large proportion of inorganic insoluble phosphorusconsiderably eclipsed the biological removal of soluble phosphorus, which suggested that the solids/liquid separationbefore aeration could be important to improve the biologicaluptake of soluble phosphorus.  相似文献   

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