Development and validation of a terrestrial biotic ligand model predicting the effect of cobalt on root growth of barley (Hordeum vulgare)

A Biotic Ligand Model was developed predicting the effect of cobalt on root growth of barley (Hordeum vulgare) in nutrient solutions. The extent to which Ca(2+), Mg(2+), Na(+), K(+) ions and pH independently affect cobalt toxicity to barley was studied. With increasing activities of Mg(2+), and to a lesser extent also K(+), the 4-d EC50(Co2+) increased linearly, while Ca(2+), Na(+) and H(+) activities did not affect Co(2+) toxicity. Stability constants for the binding of Co(2+), Mg(2+) and K(+) to the biotic ligand were obtained: logK(CoBL)=5.14, logK(MgBL)=3.86 and logK(KBL)=2.50. Limited validation of the model with one standard artificial soil and one standard field soil showed that the 4-d EC50(Co2+) could only be predicted within a factor of four from the observed values, indicating further refinement of the BLM is needed.     

Effect of cations on copper toxicity to wheat root: implications for the biotic ligand model

The extent to which calcium, magnesium, sodium, potassium and hydrogen ions independently mitigate Cu rhizotoxicity to wheat (Triticumaestivum) in nutrient solutions was examined. Increasing activities of Ca(2+) and Mg(2+) but not Na(+), K(+) and H(+) linearly increased the 2 d EC50 (as Cu(2+) activity), supporting the concept that some cations can compete with Cu(2+) for binding the active sites at the terrestrial organism-solution interface (i.e., the biotic ligand, BL). According to the biotic ligand model (BLM) concept, the conditional stability constants for the binding of Cu(2+), Ca(2+) and Mg(2+) to the BL were derived from the toxicity data. They were 6.28, 2.43 and 3.34 for logK(CuBL), logK(CaBL) and logK(MgBL), respectively. It was calculated that on average 43.6% of BL sites need to be occupied by Cu(2+) to induce 50% root growth inhibition. Using the estimated parameters, a BLM was successfully developed to predict Cu toxicity for wheat as a function of solution characteristics.     

Atmospheric input of elements to forest ecosystems: a method of estimation using artificial foliage placed above rain collectors

Usefulness of a method of artificial foliage was tested for estimation of total ionic inputs from the atmosphere to forest ecosystems, as well as of processes relevant to ionic fluxes through tree canopies: uptake, leaching, passive flow. The studies were performed in Norway spruce and European beech stands in Karkonosze Mountains (Poland), in 1995-97. Artificial leaves of increasing leaf area index: 0, 2, 6 and 12 m(2) m(-2 )were placed above standard rain collectors. It has been found that total atmospheric fluxes of H(+), NH(4)(+), Ca(2+), Mg(2+), Pb(2+), NO(3)(-) and SO(4)(2-) rose as surface area of the foliage increased. This was especially true for nitrate, sulphate and ammonium. No such relationship was found for K(+), Na(+), Zn(2+), Cd(2+), Cu(2+) and PO(4)(3-). The increase in anion fluxes exceeded that in neutralising cations (NH(4)(+), Na(+), K(+), Mg(2+), Ca(2+)) and led to progressive rainwater acidification with the increase in the foliage area. An analysis of net canopy exchange (atmospheric input-throughfall flux) has shown that SO(4)(2-), PO(4)(3-), Na(+), Ca(2+) and Cu(2+) flowed passively through the tree crowns; NH(4)(+), NO(3)(-), Zn(2+), Cd(2+) and occasionally Pb(2+) were efficiently absorbed, whereas K(+) was leached from the canopies. Beech was more effective in modifying ionic pool from the atmosphere than spruce. This related to H(+) (greater absorption) and Mg(2+) (greater leaching). It has been demonstrated that the results concerning trends in net canopy exchange and produced by the simple method of artificial foliage are comparable to more sophisticated techniques of the measurements. This proves the method to be useful.     

Stemflow chemistry of urban street trees

pH and ion concentrations (Na(+), K(+), Mg(2+), Ca(2+), NO(-)(3)) in the stemflow of the evergreen broad-leaved tree, Ilex rotunda, planted in the median strip of a highway and nitrogen oxides concentration in the air in an urban site were compared with a suburban site in Fukuoka city, Japan. The annual average of the nitrogen oxides concentration in the air was higher and NO(-)(3) concentration in the stemflow at the urban site was higher or similar compared with the suburban site. However, the annual average of pH in the stemflow at the urban site was higher than at the suburban. The annual average cation concentrations in the stemflow at the urban site were higher than at the suburban except Na(+). In particular, K(+) and Ca(2+) were higher throughout the measurement period. Therefore, higher pH in the urban stemflow was probably due to neutralization by higher concentrations of K(+), Mg(2+) and Ca(2+).     

Atmospheric deposition to the edge of a spruce forest in Denmark

Atmospheric deposition was measured during 1 year at the forest edge of a Norway spruce stand in Denmark. Inside the forest the deposition of H(+), Ca(2+), Mg(2+), Na(+), K(+), Cl(-), NO(3)(-), NH(4)(2) and SO(4)(2-) with canopy throughfall varies with the distance from the forest edge. The deposition at the edge is found to be 10-20 times as high as deposition to an open field and 2-8 times as high as deposition inside the stand. An exponential decrease in deposition as a function of the distance from the forest edge is found. Increased deposition of K(+) and non-sea salt Mg(2+), which mainly originates as a result of leaching from the needles may be explained by a larger leaf area index (LAI) at the forest edge. Deposition of particulate substances, especially Na(+), Cl(-), Mg(2+) and to some extent SO(4)(2-), NH(4)(+) and NO(3)(-) is increased much more than the LAI, which we believe to be caused by changes in wind movements at the forest edge.     

Ionic composition of PM(10) in the area of Thessaloniki,Greece

Airborne particulate matter (PM(10)) was collected from July 1997 to July 1998 at three locations in the city of Thessaloniki. PM(10) samples were analyzed for Cl(-), NO3(-), SO4(2-), Ca(2+), Mg(2+), Na(+), K(+) and NH4(+). The average PM(10) concentrations were found similar in all three sites with higher values in cold period. The ionic content comprised the 17-23% of the PM(10) mass and sulfate made up the 35-38% of the PM(10) ionic content with an average concentration of 4.80-7.26 microg m(-3). Good correlation was found for SO4(2-) and NO3(-) with Ca(2+), Mg(2+) and Cl(-). Two factors were found to influence the variance of ionic constituents in PM(10) by using factor analysis. Data evaluation considering wind direction showed that higher PM(10) and other ionic concentrations are associated with calm conditions, suggesting influences of local sources.     

Study on the photocatalytic degradation of glyphosate by TiO(2) photocatalyst

In this paper, the photocatalytic degradation of glyphosate selected as the deputy of organic pollutant in aqueous solution with TiO(2) powder as a photocatalyst has been studied. The effects of various parameters, such as the amount of the photocatalyst, illumination time, initial pH value, electron acceptors, metal ions, and anions on the photocatalytic degradation of glyphosate were investigated. From the studies, the best condition for the effect of the parameters on the photocatalytic degradation of glyphosate was obtained. The results show that the optimum amount of the photocatalyst used is 6.0 g l(-1) for the photocatalytic reactions. The photodegradation efficiency of glyphosate increases with the increase of the illumination time. With the addition of Fe(3+), Cu(2+), H(2)O(2), K(2)S(2)O(8) or KBrO(3), the photocatalytic degradation of glyphosate is accelerated. However, with the addition of Na(+), K(+), Mg(2+), Ca(2+), Zn(2+), Co(2+) and Ni(2+), or with the addition of trace amounts of Cl(-), Br(-), SO(4)(2-), there are no obvious effects on the reactions. Acidic or alkaline mediums are favorable for the photocatalytic degradation of glyphosate. The possible roles of the additives on the reactions and the possible mechanisms of effect were discussed.     

Throughfall chemistry in a spruce chronosequence in southern Poland

The chemical composition of throughfall and canopy leaching, as well as the acid neutralizing capacity and alkalinity depended on the age of Norway spruce (Picea abies Karst) stands and season of the year. A higher amount of sulphur and strong acids was deposited to the soil in the older age classes. Concentrations of SO(4)(2)(-), K(+), H(+), Mn(2+), Fe(2+) and Zn(2+) in throughfall were higher than in bulk precipitation in any season. This suggests that these ions were washed out or washed from the surface of needles and/or barks. The other ions NO(3)(-), NH(4)(+), Ca(2+) and Mg(2+) were retained by the canopy, in particular Ca(2+) and Mg(2+) during the growing season in young stands. Principal component analysis identified five factors responsible for the data structure and suggested the major anthropogenic emission sources were acidic emission (SO(4)(2)(-)+NO(3)(-)), heavy metals-dust particles (Fe(2+)+Mn(2+)+Zn(2+)), ammonium (NH(4)(+)) and H(+), while the natural-origin emission was mineral dust (Na(+)+K(+)+Ca(2+)+Mg(2+)).     

Sub-chronic effect of neem based pesticide (Vepacide) on acetylcholinesterase and ATPases in rat.

Acetylcholinesterases (AChE), Na(+)-K+, Mg2+ and Ca(2+)-ATPases were monitored in rat brain when treated orally with 80, 160 and 320 mg/kg of Vepacide, an active ingredient from neem seed oil, daily for 90 days. Brain AChE, Na(+)-K+ and Ca(2+)-ATPases were inhibited whereas Mg(2+)-ATPase levels were enhanced in both the sexes after 45 and 90 days of treatment. The relative sensitivities of these ATPases to Vepacide indicated that Ca(2+)-ATPase being more sensitive than Na(+)-K(+)-ATPase in both the sexes. The magnitude of Ca(2+)-ATPase inhibited by this compound was higher than that of brain AChE. It appears to be sexual dimorphism in the alterations of brain AChE, Na(+)-K+ and Mg(2+)-ATPases by Vepacide with females being significant when compared with males. After 28 days of post treatment the alterations observed were approached to those of controls both in male and female rats showing reversal of the toxicity. These results indicated that the ATPases were potently inhibited by Vepacide and seemed to be its precise target among the enzyme studied. This can be used as biochemical marker of exposure to this neem derived product.     

Effects of ozone on foliar leaching in Norway spruce (Picea abies L. Karst): confounding factors due to NOx production during ozone generation

Previous experiments with conifers fumigated with O(3), produced by air-operated electric discharge ozonators, have provided evidence that O(3) increases the leaching of NO(3)(-), NH(4)(+), K(+), Ca(2+), Mg(2+) and some other cations from needles, when the trees are treated with acid mist. This evidence has provided the foundation of the ozone-acid mist hypothesis of spruce decline. We report experiments with Norway spruce saplings fumigated with purified and unpurified O(3). The results show that the accumulation of NO(3)(-) in the needles arises from the rapid deposition of N(2)O(5) and HNO(3) formed from N(2) in the ozonator. An increase in removal of NH(4)(+), Na(+), Ca(2+), Mg(2+), Zn(2+) and Mn(2+) from the needles during soaking in H(2)SO(4), pH3, was also observed, which was related to the increase in NO(3)(-) but was independent of O(3) concentration. It is concluded that results of previous experiments cited in support of the ozone-acid mist hypothesis arose from effects which were at least partly caused by N(2)O(5) produced as a contaminant, and were incorrectly attributed to ozone. Other effects, such as growth stimulations, visible symptons, enhanced frost sensitivity, and infestation by pests or pathogens, which have been attributed to O(3) generated by electric discharge in air, should be interpreted with caution. Future experiments with ozone must eliminate this problem by either using O(2)-driven ozonators, or by purifying the output from air-driven ozonators using cold and/or water traps.     

Throughfall chemistry and canopy interactions in a Sitka spruce plantation sprayed with six different simulated polluted mist treatments

Throughfall chemistry was studied in a mature Sitka spruce plantation in order to investigate canopy interactions, such as nitrogen absorption, cation leaching, and neutralization of rainfall passing through the canopy. The plantation had been exposed to six different simulated mist treatments including N (NH(4)NO(3)) and S (H(2)SO(4) at pH 2.5) in four replicated blocks since 1996. Throughfall and rainfall were collected from May to September 2000. The results showed that 30-35% of the applied N was retained by the canopy. There were linear relationships between the loss of H(+) and increased K(+), Mg(2+) and Ca(2+) deposition through the canopy. However these increases in K(+), Mg(2+) and Ca(2+) deposition accounted for only about 50% of total neutralization of the acidity. The relationship between the anion deficits in throughfall and the loss of H(+) implied that weak organic acid anions were involved in the neutralization of the acidity in throughfall.     

Effect of anions and cations on cadmium sorption kinetics from aqueous solutions by chitin: experimental studies and modeling

The effect of ions, including Na(+), Mg(2+), Ca(2+), Cl(-), SO(4)(2-) and CO(3)(2-), at various initial concentrations, on the kinetics of cadmium sorption by chitin was studied at 25 degrees C and free initial pH solution in batch conditions. The presence of these ions in solution was found to inhibit the uptake of cadmium by chitin to different degrees: sodium and chloride ions have no significant effect. For Mg(2+), Ca(2+), SO(4)(2-) and CO(3)(2-) ions, the effects ranged from a large inhibition of cadmium by Ca(2+) and CO(3)(2-) to a weak inhibition by Mg(2+) and SO(4)(2-). These results indicate that the uptake sites of these ions are the same. No ion was found to enhance cadmium uptake. The results also showed that the kinetics of sorption are best described by a pseudo second-order expression than a first or second-order model.     

Rainwater chemistry at the summit and southern flank of the Itatiaia massif, Southeastern Brazil

Wet deposition and related rainwater chemistry were studied at the Itatiaia massif, on which is settled the Itatiaia National Park (INP). Samples were simultaneously collected on a weekly basis over 12 months, using automated wet and dry samplers, at the INP-Headquarters (INP-Hq; altitude=820 m) and the Itatiaia Plateau (It-Pt; altitude=2460 m). Conductivity, pH, Na(+), K(+), Mg(2+), Ca(2+), NH(4)(+), Cl(-), NO(3)(-) and SO(4)(2-) were determined in 36 rainwater samples. Volume-weighted mean (VWM) pH was lower at the INP-Hq (4.9) than at the It-Pt (5.3). Very strong correlation between Cl(-) and Na(+) was found for the INP-Hq (r=0.99). At the Itatiaia massif, SO(4)(2-), NO(3)(-), and NH(4)(+) comprised together about 60% of the total inorganic ions and appear to exert the major control on rainwater pH.     

Chemical characterization of rainwater at Singapore

A short term study of the chemical composition of rainwater was carried out from November 1999 to October 2000 in Singapore. The rainwater was typically acidic with a mean pH of 4.2. Sulfate was the most abundant ion and comparable to the results reported for other industrialized regions. The concentrations of major ions (NH(4)(+), Ca(2+), K(+), Na(+), Mg(2+), SO(4)(2+), NO(3)(2-), Cl(-), HCOO(-), CH(3)COO(-)) varied monthly. Results show that local meteorological conditions influence the chemical compositions to a significant extent. The pollutants in rainwater were derived from long range and local (industry and traffic) sources.     

Phytotoxicity of nickel in a range of European soils: influence of soil properties, Ni solubility and speciation

We investigated the influence of soil properties on Ni toxicity to barley root and tomato shoot growth, using 16 European soils. The effective concentration of added Ni causing 50% inhibition (EC(50)) ranged from 52 to 1929mgkg(-1) and from 17 to 920mgkg(-1) for the barley and tomato test, respectively, representing 37- and 54-fold variation among soils. Soil cation exchange capacity was the best single predictor for the EC(50). The EC(50) based on either the Ni concentration or free Ni(2+) activity in soil solution varied less among soils (7-14 fold) than that based on the total added Ni, suggesting that solubility of Ni is a key factor influencing its toxicity to plants. The EC(50) for free Ni(2+) activity from the barley test decreased with increasing pH, indicating a protective effect of protons. The results can be used in the risk assessment of Ni in the terrestrial environment.     

Changes in hematological and serum biochemical values in jundiá Rhamdia quelen due to sub-lethal toxicity of cypermethrin

Jundiá (Rhamdia quelen, Quoy and Gaimard), a South American teleostean fish, was exposed to sub-lethal concentrations of cypermethrin (30% and 45% of the 48-h LC(50) value of 0.265 ppm) for 2, 4 or 8 days. Serum biochemical and hematological values and behavioral changes were studied. The 30% LC(50), 0.08 ppm, produced significant increases in Mg(2+), P, K(+), creatinine, urea, glucose, cholesterol, aspartate aminotransferase and alkaline phosphatase levels, and reduction in total proteins and triglycerides in serum. The 45% LC(50), 0.12 ppm, produced significant increase in Na(+), Mg(2+), P, K(+), creatinine, urea, glucose, cholesterol, and alkaline phosphatase, and reduction in triglycerides and alanine aminotransferase levels in serum. At this concentration, the fish showed behavior changes such as hyper-excitability, asphyxia, and widening of mouth and operculum. The hematological values remained normal, except for hemoglobin concentrations and the mean corpuscular hemoglobin concentration, which increased with exposure to 0.08 ppm and 0.12 ppm cypermethrin. Results of the present work show that biochemical analysis of serum can be useful to detect incipient cypermethrin intoxication of the shoal.     

The dissolution kinetics of major elements in municipal solid waste incineration bottom ash particles

Leaching and tracer experiments in batches at L/S 20 were performed with 3-month-old MSWI bottom ash separated into eight different particle sizes. The time-dependent leaching of major elements (Ca(2+), K(+), Na(+), Cl(-) and SO(4)(-2)) was monitored for up to 747 h. Physical properties of the particles, the specific surface (BET), pore volume and pore volume distribution over pore sizes (BJH) were determined for all particle classes by N(2) adsorption/desorption experiments. Some common features of physical pore structure for all particles were revealed. The specific surface and the particle pore volume were found to be negatively correlated with particle size, ranging from 3.2 m(2)/g to 25.7 m(2)/g for the surface area and from 0.0086 cm(3)/g to 0.091 cm(3)/g for the pore volume. Not surprisingly, the specific surface area was found to be the major material parameter that governed the leaching behavior for all elements (Ca(2+), K(+), Na(+), Cl(-) and SO(4)(-2)) and particle sizes. The diffusion resistance was determined independently by separate tracer (tritium) experiments. Diffusion gave a significant contribution to the apparent leaching kinetics for all elements during the first 10-40 h (depending on the particle size) of leaching and surface reaction was the overall rate controlling mechanism at late times for all particle sizes. For Ca(2+) and SO(4)(-2), the coupled effect of diffusion resistance and the degree of under-saturation in the intra particle pore volume was found to be a major rate limiting dissolution mechanism for both early and late times. The solubility control in the intra particulate porosity may undermine any attempt to treat bottom ash by washing out the sulfate. Even for high liquid/solid ratios, the solubility in the intra-particular porosity will limit the release rate.     

Ca(2+) -dependent plant response to Pb(2+) is regulated by LCT1

Tobacco plants transformed with TaLCT1 were cultured on Knop's medium with modified calcium concentrations (0.01-3 mM) in the presence of Pb(2+), and in soil contaminated by lead. A 4-5 microM Pb(2+) administered in the presence of 1 mM Ca(2+) inhibited the root growth of transgenic plants to much lesser degree than of control plants, whereas in the presence of 3mM Ca(2+) no differences were found between the studied lines. The reduction of Pb(2+) toxicity in the presence of 1 mM Ca(2+) was not accompanied by a change in the lead tissue concentration. However, when Ca(2+) level in the medium was lowered to 0.01 mM, several fold higher root/shoot Pb ratio in transgenic plants was observed, twofold increase in the total amount of metal accumulated, and lower concentration of Pb in the xylem sap. Results suggest the involvement of TaLCT1 in the regulation of Ca-dependent Pb-detoxification, and under conditions of low calcium in lead uptake and distribution.     

The synaptosomal membrane bound ATPase as a target for the neurotoxic effects of pyrethroids,permethrin and cypermethrin

Pyrethroids are used widely as insecticides both in agriculture and in households. A cellular target of pyrethroids is the sodium channel in the membrane. In the present study, the activity of the membrane bound integral protein ATPase was studied as a biomarker for the membrane effect of the pyrethroids permethrin and cypermethrin. Male Sprague-Dawley rats were used for cerebral synaptosome preparation. The isolation of synaptosomes was performed with the Percoll gradient method. Both total ATPase and Mg(2+) activated ATPase were studied by determining inorganic phosphate liberated from the substrate ATP. One hour exposure to permethrin (Biokill) and cypermethrin (Ripcord) insecticide products affected ATPase activities. The activity of Na(+), K(+) ATPase decreased dose-dependently in 10-50 microM concentrations of permethrin, and Mg(2+) activated ATPase increased over twofold in the same concentrations of the active components. The effect of the cypermethrin compound Ripcord was not clearly dose-dependent. The activity of total ATPase was almost entirely lost in the concentrations of 100 microM of permethrin and cypermethrin. The results support the idea that membrane ATPases are one target of the neurotoxic effect of pyrethroid compounds.