A Study on Al(III) and Fe(II) Ions Sorption by Cattle Manure Vermicompost

Cattle manure vermicompost has been used for the adsorption of Al(III) and Fe(II) from both synthetic solution and kaolin industry wastewater. The optimum conditions for Al(III) and Fe(II) adsorption at pH?2 (natural pH of the wastewater) were particle size of ≤250?µm, 1 g/10 mL adsorbent dose, contact time of 4 h, and temperature of 25°C. Langmuir and Freundlich adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R ² values from 0.90 to 0.98. In synthetic solution, the maximum adsorption capacity of the vermicompost for Al(III) was 8.35 mg g^?1 and for Fe(II) was 16.98 mg g^?1 at 25°C when the vermicompost dose was 1 g 10 mL^?1, and the initial adjusted pH was 2. The batch adsorption studies of Al(III) and Fe(II) on vermicompost using kaolin wastewater have shown that the maximum adsorption capacities were 1.10 and 4.30 mg g^?1, respectively, at pH?2. The thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous.     

Enhanced Heavy Metal Phytoextraction from Marine Dredged Sediments Comparing Conventional Chelating Agents (Citric Acid and EDTA) with Humic Substances

Metal (Cu, Mn, Ni, Zn, Fe) concentrations in marine sediment and zooplankton were investigated in Izmir Bay of the Eastern Aegean Sea, Turkey. The study aimed to assess the levels of metal in different environmental compartments of the Izmir Bay. Metal concentrations in the sediment (dry weight) ranged between 4.26–70.8 μg g^?1 for Cu, 233–923 μg g^?1 for Mn, 14.9–127 μg g^?1 for Ni, 25.6–295 μg g^?1 for Zn, 12,404–76,899 μg g^?1 for Fe and 38,226–91,532 μg g^?1 for Al in the Izmir Bay. Maximum metal concentrations in zooplankton were observed during summer season in the inner bay. Significant relationships existed between the concentrations of certain metals (Al, Fe, Mn and Ni) in sediment, suggesting similar sources and/or similar geochemical processes controlling such metals. Higher concentrations of Cu, Zn and percent organic matter contents were found in the middle-inner bays sediments. Based on the correlation matrix obtained for metal data, organic matter was found to be the dominant factor controlling Cu and Zn distributions in the sediment. In general, mean Cu and Zn levels in the bay were above background concentrations in Mediterranean sediments. Zooplankton metal concentrations were similar to sediment distributions.     

Complexation of Cu2+ and Pb2+ by peat and humic acid

The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu²⁺ and Pb²⁺) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb²⁺ than for Cu²⁺ (e.g. at pH = 5 HA gave 0·188 mmol Cu²⁺ g^?1 and 0·564 mmol Pb²⁺ g^?1: peat gave 0·111 mmol Cu²⁺ g^?1 and 0·391 mmol Pb²⁺ g^?1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K₁) for Cu²⁺ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K₁= 2·63, and peat gave log K¹= 4·47 for Cu²⁺). The values for Pb²⁺ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K¹= 3·03 and peat gave log K¹= 3·00 for Pb²⁺). In the peat, Cu²⁺ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb²⁺ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.     

Aluminum retention in a man-made Sphagnum wetland

Runoff from a highway interchange in western Maryland had Al concentrations averaging about 50 mg L^?1, with a maximum of 206 mg L^?1. As an alternative to expensive chemical treatment of this Al-rich water, in August 1984, the drainage was diverted through a 500 m² man-made wetland, constructed from organic peat. For a 10 week period, Al concentrations in water leaving the wetland averaged 1.5 mg L^?1. as compared to Al concentrations at the two major inflows to the wetland of 35.3 and 6.6 mg L^?1. However, effective treatment of the drainage by the wetland was not observed over the entire 27 mo sampling period. Peat chemical analysis indicated that over the 27 mo, total Al concentration in the peat increased from 2375 μg g^?1 to 13 634 μg g^?1. Of this increase 5.5 % was contributed by exchangeable Al, 4.3% by adsorbed Al, 39.8% by organically bound Al, 33.1% by oxide bound Al, and 17.2% by precipitated and residual Al. Changes in Fe, Mn, Ca, Mg, K, and Na chemistry in the peat associated with Al retention are discussed.     

Organo-mineral associations in sandy acid forest soils: importance of specific surface area, iron oxides and micropores

Organo-mineral associations stabilize soil organic matter, though the mechanisms by which they do so are unclear. We used particle-size fractions < 6.3 μm of two soils to examine the importance of Fe oxides, short-range order Al silicates and the surface areas of minerals and micropores on the formation of organo-mineral associations. In the subsoil Fe oxides were most strongly statistically correlated with the mineral-bound organic carbon. We therefore assume that they are the most important substrates for the formation of organo-mineral associations. There is no indication that this is caused by physical protection of organic matter in their micropores (< 2 nm). In the Haplic Podzol, dithionite–citrate–bicarbonate-soluble short-range order Al silicates may also play a role. Fe oxide particles were calculated to offer specific surface areas of ∼ 200 m² g⁻¹ (goethite) and ∼ 800 m² g⁻¹ (ferrihydrite), corresponding to crystal diameters of only a few nm. We assume that the resulting large amount of oxide-specific reactive surface sites (conditionally charged hydroxyl groups) is responsible for their dominant role as sorbents. With maximum C loadings of 1.3 mg C per m² Fe oxide for the Dystric Cambisol and 1.1 mg C per m² Fe oxide + short-range order Al silicates for the Haplic Podzol the subsoils of both soils seem to have reached saturation with respect to organic matter sorption. In contrast to subsoil horizons, organo-mineral associations from topsoils contain much larger amounts of organic matter. Here a larger C loading on Fe oxides or a greater importance of other sorbents in addition to the oxides must be assumed.     

The effect of potassium and humic acid applications on yield and nutrient contents of wheat (Triticum aestivum L. var. Delfii) with same soil properties

Abstract

This study was conducted in the farmer field between the years 2014 and 2015. In this study, 3 doses of potassium (K) (0, 10, and 20?kg da^?1) of K₂SO₄ (50% K₂O) fertilizer and 3 doses of humic acid (HA) (0, 20, and 40?kg da^?1) (85% HA) were used. Increase in the HA dose reflected significant effects on pH, salt, organic matter, phosphorus, magnesium, iron, and manganese contents of the experiment area at p?p?p?p?p?相似文献   

Heat output of the soil biomass

Amending soils with glucose (5 mg g^?1) resulted in an immediate increase in microbial activity and within 30 min the rates of heat output and respiration at 22° C were increased by up to 17.8 and 23.4 times, respectively. The increased rate of heat output remained stable for up to 6 h and there was good correlation with the amount of CO₂ respired. The soil biomass was calculated by the method of Anderson and Domsch (1978). The rate of heat output of the biomass varied in different soils and ranged from 11.5 to 83.7 Jh^?1 g^?1 biomass C. In glucose-amended soils, however, the rate of heat output was much more consistent; the soils were in two groups having between 169–265 Jh^?1g^?1 biomass C or 454–482 J h^?1 g^?1 biomass C, both the latter two soils were from pasture. The increased rate of heat output from the amended soils was lower than expected from the respiration rate and the heat of oxidation of glucose, suggesting that a proportion of the CO₂ respired was from catabolism of substrates other than glucose. Use of ¹⁴C-glucose confirmed that between 57–91% of the CO₂ was derived from the glucose substrate.     

Remediation of Atrazine-contaminated Soil and Water by Nano Zerovalent Iron

Atrazine-contaminated soil may require remediation to mitigate ground and surface water contamination. We determined the effectiveness of nano zerovalent iron (nano ZVI) to dechlorinate atrazine (2-chloro-4ethylamino-6-iso-propylamino-1,3,5-triazine) in contaminated water and soil. This study determined the effects of iron sources, solution pH, Pd catalyst and presence of Fe or Al sulfate salts on the destruction of atrazine in water and soil. Our results indicate nano ZVI can be successfully used to remediate atrazine in water and soil. Aqueous solution of atrazine (30 mg l^?1) was treated with 2% (w/v) of nano ZVI and 5% (w/v) of commercial ZVI. Although, iron dose in nano ZVI treatment was less than that in commercial ZVI treatment, atrazine destruction kinetic rate (k _obs) of nano ZVI treatment (1.39 days^?1) was around seven times higher than that of commercial ZVI treatment (0.18 days^?1). Reductive dechlorination was the major process in destruction of atrazine by nano ZVI. The dechlorination product was 2-ethyl-amino-4-isopropylamino-1,3,5-triazine. Lowering the pH from 9 to 4 increased the destruction kinetic rates of atrazine by nano ZVI. Moreover, nano ZVI/Pd enhanced destruction kinetic rates of atrazine (3.36 day^?1). Pd played the important role as a catalyst during treatment of atrazine by nano ZVI. Atrazine destruction kinetic rates were greatly enhanced in both contaminated water and soil treatments by nano ZVI when sulfate salts of Fe(II), Fe(III) or Al(III) was add with the following order of removal rates: Al (III) (2.23 day^?1) > Fe (III) (2.04 day^?1) > Fe(II) (1.79 day^?1). The same results were found in atrazine-nano ZVI-soil incubation experiments.     

Phosphate,Fe and Mn uptake of N2 fixing red clover and ryegrass from an Oxisol as affected by P and model humic substances application. 1. Plant parameters and soil solution composition

The effect of humic substances on P-availability in soil is still debated. Therefore, the effect of model humic substances synthesized from hydroquinone on P, Fe, and Al solubility in a strong P fixing Oxisol and on P acquisition by red clover and ryegrass was investigated. After 4 months of incubation, P concentration of soil solution had increased by a factor of > 10 at the highest humic level (50 g humics kg^?1 soil), accompanied by a similar increase in Fe and Al concentrations. Soil samples with 0, 10, 30, 50 g humics kg^?1 soil were planted with red clover and ryegrass. Red clover showed a small increase of shoot yield and a moderate increase of P uptake after humics addition. High humics levels increased slightly Fe concentration in the shoots but strongly that of Mn leading to Mn toxicity. Ryegrass showed a strong increase in shoot yield after humics addition of about 150 % at the highest humics level compared to the control without humics. At each humic level, P application (100 mg kg^?1 soil) had no effect on P uptake of red clover and a small effect on P uptake by ryegrass. The relatively small effect of humics and P application on shoot yield of clover compared to grass can be explained by chemical P mobilization of red clover via exudation of citrate (about 12 μmol citrate g^?1 soil). This agrees with the finding that P solubility increased in the soil under red clover but not under ryegrass from the first to the second harvest, indicating that red clover mobilized P.     

Influence of pH and organic substance on the adsorption of As(V) on geologic materials

The adsorption of As(V) on alumina, hematite, kaolin and quartz has been measured as a function of pH (2 to 10), and As concentrations (10^?4 to 10 ^?8 M; in the alumina and kaolin systems only). The effects of sulfate (0 to 80 mg L^?1) and fulvic acid (0 to 25 mg L^?1) were studied. The charge of the solid surface and the As speciation in solution (determined by pH) were the most important chemical parameters affecting the sorption behavior. At pH below PZC of the solid, there was a qualitative correlation between the adsorption and the anion exchange capacity of the solid. For hematite at low pH (below 5) there was a reduction of the adsorption possibly related to the formation of positively charged species. The presence of sulfate or fulvic acid reduced the adsorption.     

Residual metal reactivity of humic acids extracted,from soil amended with sewage sludge

Copper, Fe, and Mn were used as probes to investigate residual metal reactivity for humic acid (HA) samples extracted from a loam soil, either non-amended or amended with anaerobically digested sewage sludge for 4, 5, 6, or 7 yr at 90 t ha^?1. yr^?1. Irrespective of their origin, the HA complexes significant amounts of metal, in forms stable against intense water-leaching, in the order Fe > Cl > Mn. Sludge-amended soil HA adsorbed and retained Fe in amounts greater than HA extracted fron non-amended soil. Metal adsorption occurred mainly by cation-exchange replacement of metals previousl: bound to HA. Water-stable Fe³⁺-HA complexes prepared in the laboratory were partially stable agains H⁺ and metal ion exchange reactions, whereas Cu²⁺ and Mn²⁺ in laboratory-prepared, water-stabl HA complexes were desorbed almost completely by these two reactions. Electron spin resonance spectra indicated that the laboratory-prepared metal-HA complexes had a chemical composition and molecula structure similar to that of indigenous metal-HA complexes, which were stable against all leachin, and cation-exchange treatments. Although the HA samples showed a maximal metal binding (i.e. saturation) as metal loading of the sludge-amended soil increased, they still exhibited a high residua binding capacity for the three metals used as probes.     

Integrative Soil Application of Humic Acid and Sulfur Improves Saline Calcareous Soil Properties and Barley Plant Performance

ABSTRACT

During the 2017 and 2018 seasons, two field experiments were conducted on newly reclaimed saline calcareous soil (7.13 dS m^?1, 16.9% CaCO₃) in the experimental farm of the Faculty of Agriculture, Demo, Fayoum Governorate, Egypt. The current work aimed at identifying the potential positive effects of applied humic acid (HA) and elemental sulfur (S) on some soil properties and barley plant performance. The results showed that the application of HA and/or S at different rates ameliorated the adverse effects of saline calcareous soil conditions and significantly reduced some chemical properties of the soil (e.g., pH, ECe, and CaCO₃%), while soil organic matter (OM%) and some nutrients (e.g., P, Fe, Mn, Cu, and Zn) contents were significantly increased. In addition, the contents of nutrients (e.g., P, Fe, Mn, Cu, and Zn) in barley plant and yielded grain, grain content of N and protein (%), and the performance (e.g., plant height, spike length, grain and straw yields, and weight of 1000-grain) of barley plant were significantly increased with the application of HA and/or S. The best results were obtained through the integrative application of 100 kg HA + 400 kg S ha^?1 to the tested saline calcareous soil. Therefore, the integrative soil application of 100 kg HA + 400 kg S ha^?1 can be recommended for the cultivation and sustainability of crop production in saline calcareous soil, in addition to rationalize the use of mineral fertilizers, which represent a surplus point for the sustainable agriculture system.     

Dissolution of aluminum and iron phosphate by humic acids

Abstract

An investigation was conducted to study the effect of humic (HA) and fulvic acid (FA) on the dissolution of aluminum phosphate (AlPO₄) and iron phosphate (FePO₄), to analyze the dissolution products, and assess their availability to plants. The rate of dissolution was determined by shaking 10 mg of Al‐ or FePO₄ with 0 to 800 mg L^‐1 of HA or FA solutions at pH 7.0 for 0 to 192 hours. The phosphorus (P) concentration was measured in the extracts by spectrophotometry, whereas the nature of P‐humic acid complexes was determined by ³¹P NMR analysis. Availability of dissolution products was studied by growing corn plants in aerated hydroponic solutions receiving treatments of 50 mg Al‐ or FePO₄ and 0 to 800 mg L^‐1 of HA or FA at pH 5.0. The results indicated that the amount of P released by HA or FA increased with time. Humic acid was more effective than FA in dissolving the metal phosphates. The ³¹P NMR analysis showed that the dissolution products contained free orthophosphates and minor amounts of P‐humic acid complexes. This confirms the role of HA as a powerful chelator of Al and Fe, liberating in this way the orthophosphate anions. Corn plants grown in hydroponics, with AlPO₄ or FePO₄ as the source of P, exhibited better growth performance when HA or FA are present.     

Specific sorption of antimony (III) by the hydrous oxides of Mn,Fe, and Al

The hydrous oxides of Mn, Fe, and Al avidly sorbed Sb from μM Sb(OH), solutions, with uptake levelling off as initial Sb concentration increased. Capacity values decreased along the sequence MnOOH > Al(OH)₃ > FeOOH. The amount sorbed by each substrate decreased gradually at pH values > 6. Addition of 0.4M CH₃COONa to the aqueous phase (to minimise retention of weakly bound Sb) had little effect on MnOOH uptake capacity (～160 mmol, kg^?1 at pH < 7) but retention dropped rapidly at higher pH. With the other two substrates (pH 6–7) the calculated capacity values for specific Sb sorption were ～ 45 mmol kg^?1 FeOOH and ～ 33 mmol kg^? Al(OH)₃; about a third of the total capacity values. On these substrates specific Sb sorption tended to peak in the pH 7 to 8 region. The pH response pattern was modified using Sb tartrate sorbate solutions. Factors influencing Sb sorption included substrate surface charge, chemical form of Sb and surface interactions. Formation of a sparingly soluble metal coating was indicated by the uptake plateaus observed when increasing amounts of solid were added to Sb solutions containing acetate.     

稻米和土壤微量元素的空间变异

Consumption of rice is the main source of micronutrients to human in Asia. A paddy field with unknown anthropogenic contamination in Deqing County, Zhejiang Province, China was selected to characterize the spatial variability and distribution of micronutrients in rice grain and soil. A total of 96 paired soil and rice grain samples were collected at harvest. The micronutrients in the soil samples were extracted by diethylenetriamine pentaacetic acid (DTPA). The mean micronutrient concentrations in rice grain were 3.85 μg Cu g-1, 11.6 μg Fe g-1, 39.7 μg Mn g-1, and 26.0 μg Zn g-1. The mean concentrations were 2.54 μg g-1 for DTPA-Cu, 133.5 μg g-1 for DTPA-Fe, 30.6 μg g-1 for DTPA-Mn, and 0.84 μg g-1 for DTPA-Zn. Semivariograms showed that measured micronutrients in rice grain were moderately dependent, with a range distance of about 110 m. The concentrations of the DTPA-extractable micronutrients all displayed strong spatial dependency, with a range distance of about 60 m. There was some resemblance of spatial structure between soil pH and the grain Cu, Fe, Mn, and Zn. By analogy, similar spatial variation was observed between soil organic matter (SOM) and DTPA-extractable micronutrients in the soil. Kriging estimated maps of the attributes showed the spatial distributions of the variables in the field, which is beneficial for better understanding the spatial variation of micronutrients and for potentially refining agricultural management practices at a field scale.     

Physiological responses of rainbow trout Salmo gairdneri exposed to plastic lake inlet and outlet stream waters

In Plastic Lake, Ontario, stocked rainbow trout (Salmo gairdneri) have failed to survive, one endemic fish species has become extinct and annual fish kills included up to five species, but especially pumpkinseeds (Lepomis gibbosus). The potential toxicity of Plastic Lake water was assessed by holding (hatchery) rainbow trout in the major inlet stream, the outlet, and in a portion of the outlet stream acidified to the pH of inlet No. 1. Stress on rainbow trout was assessed by measuring plasma and muscle concentrations of Na ⁺ Cl^?, and K⁺, plus gill A1 concentration. Trout held in Plastic Lake inlet No. 1 showed a rapid loss of plasma Na⁺ from 138 to 85 meq.L^?1and Cl^? from 120 to 75 meq.L^?1 within 24 hr. Gill A1 concentration increased from 20 to 105 μg.g^?1 dry weight. Trout held in the outlet steam showed only slight loss of plasma Na⁺ and Cl^? and no accumulation of Al on the gills. Trout held in the acidified outlet showed a significant loss of ions with plasma Na⁺ depressed from 140 to 115 meq.L^?1 and plasma Cl^? from 125 to 95 meq.L^?1over 24 hr. Gill Al concentration increased from 18 to 30 μg.g^?1 dry weight. The differences in stress response of rainbow trout held in the inlet and acidified outlet are likely due primarily to the difference in Al species concentrations in the two waters.     

DIFFERENTIAL TRANSLOCATION OF 59IRON IN IRON SUFFICIENT AND DEFICIENT SORGHUM PLANTS

Radioactively labeled iron (⁵⁹Fe) was used to study differential uptake in sorghum plants in the recovery stage of chlorosis. Radio-labeled ⁵⁹Fe was supplied through root feeding in nutrient solution experiment (48 hrs, pH 6.2) to non-chlorotic and chlorotic plants. Chlorotic plants were further treated with foliar spray [ferrous sulfate (FeSO₄), FeSO₄ + thiourea (TU), FeSO₄ + citric acid (CA), FeSO₄ + thioglycollic acid (TGA)] to study the uptake of radio-labeled ⁵⁹Fe through root feeding during recovery process of chlorosis. Under iron deficiency, the differential uptake of ⁵⁹Fe was markedly increased in leaves and stem of chlorotic control (-Fe) sorghum plants as compared to non-chlorotic control (+Fe) and foliar sprayed (FeSO₄, FeSO₄ + TU, FeSO₄ + CA, and FeSO₄ + TGA) plants. The lowest uptake of ⁵⁹Fe was observed in younger leaves (24.33 nmol, g^?1 fresh weight h^?1) and stem (1.98 nmol, g^?1 fresh weight h^?1) of non-chlorotic control followed by foliar sprayed plants in comparison to chlorotic control, respectively. Similarly less ⁵⁹Fe uptake was observed in the older leaves of FeSO₄ + CA sprayed (21.70 nmol, g^?1 fresh weight h^?1) plants in comparison to chlorotic control (35.60 nmol, g^?1 fresh weight h^?1). The highest differential ⁵⁹Fe uptake through nutrient medium was in the roots of plants, which were foliar sprayed with FeSO₄ along with TU. The role of iron alone and along with citric acid and thiol compounds is discussed in recovery of chlorosis.     

Acid stress and extinction of a spring-spawning fish population

Investigation of Heeney Lake, 21.7 ha, revealed a small population of white sucker, Catostomus commersoni. Only four age-classes were represented in this normally abundant and long-lived species. By 1984 only one new age-class had been recruited into the population. As these fish spawned in the outlet stream in early spring, the potential toxicity of these waters was assessed at two snow-melt events. Rainbow trout, Oncorhynchus mykiss, of hatchery origin were held in the outlet stream as pH declined from 6.5 to 4.7 during a snow melt, late February. Trout showed a loss of 19% in plasma Na and 24% in Cl concurrent with gill Al concentration increasing from 10 to 250 μg'g^?1 dry wt. At the mid-April snow melt, pH fell to 4.1, and rainbow trout held in the outlet showed a decline in plasma sodium of 42% and gill Al increased from 10 to 415 μg'g^?1 dry wt. Control rainbow trout held in Harp L. at pH 6.3 showed no significant change in plasma and muscle ion concentrations, or in gill Al concentration. White sucker from nearby waters were held in Heeney Lake outlet, late April, and muscle Na and Cl declined significantly as gill Al concentration increased from 11 to 50 μg'g^?1 dry wt during 48 hr exposure. White sucker hekl in Heeney L. outlet, mid-May, showed no significant change in plasma ions. No white sucker have been captured in Heeney L. since 1984 and the population is presumed to be extinct. Acid deposition has declined in recent years but lake and stream pH have not recovered and fish populations may still decline or disappear.     

Localization of aluminum in tissues of fish

The concentrations of Al in fish gills has been used as a measure of fish exposure to this metal in acidified waters. This experiment was designed to determine if other fish tissues also accumulate Al and thus possibly contribute to the cause of death. Rainbow trout (Salmo gairdneri) were exposed to the following fours test conditions for 48 hr or until death: (1) pH 6.8, <0.001 mg.L^?1 Al (n=6); (2) pH 5.2, <0.001 mg₁L^?1 Al (n=2);(3) pH 5.2,1.0 mg.L^?1 Al (n=5); (4) pH 6.8, 1.0 mg.L^?1 Al (n=3). The trout were held in synthetic, low Ca water prior to, and during, experimentation. Esophagus-stomach, gonad, gall bladder, gill (left and right), heart, intestine, kidney, liver, muscle (epaxial), and spleen were digested in a 4:1 mixture of HNO₃:HClO₄ and analyzed by Inductively Coupled Plasma Emission Spectrophotometry. Elevated Al concentrations were found in gill and gastrointestinal tissues. Left and right gills of fish exposed to pH 5.2, 1.0 mg.L^?1 Al were the only tissues found to be significantly different (p<0.01) between the test conditions. The mean total Al concentrations of these test 3 fish, for the left and right gill were 3.61 and 4.33 mg.g^?1 Al dw. The Al concentration in thle gastrointestinal tissues of the fish exposed to pH 6.8 at 1.0 mg.L^?1 Al was greater than that of the control fish, but not statistically significant. These results suggest that the analysis of whole gill remains an effective indicator of Al exposure in fishes at low pH.     

Amendment of hydroponic nutrient solution with humic acid and glutamic acid in tomato (Lycopersicon esculentum Mill.) culture

Abstract

Can humic acid (HA) and glutamic acid (GA), when added to tomato (Lycopersicon esculentum Mill. cv. ‘Hongyangli’) nutrient solution in a hydroponic system, improve growth? Tomato seedlings were grown in six nutrient solutions: (1) control (C), (2) C + 25 mg L^?1 HA (HA1); (3) C + 50 mg L^?1 HA (HA2); (4) C + 100 mg L^?1 GA; (5) HA1 + GA; (6) HA2 + GA. Various biochemical and physiological parameters were measured. HA increased photosynthesis rate and mesophyll conductance. HA did not significantly affect transpiration, stomatal conductance, titratable acidity, or antioxidant activity. In addition, GA improved protein and sugar content, mesophyll conductance and yield. The combination of HA and GA was more effective, especially with 50 mg L^?1 HA. The activity of superoxide dismutase (SOD) and peroxidases (POD) did not change in the presence of HA or GA. Malondialdehyde (MDA) content increased by 30% in HA2 together with GA. HA has a positive effect on tomato hydroponic growth when applied with GA. This expands the use of HA and GA for horticultural commodities in hydroponic systems.