Potential phytotoxicity of diquat accumulated by aquatic plants and sediments

The adsorption and desorption of Reglone A^R to freshwater algae, Myriophyllum spicatum and a soil-sand mixture, singly and in combination was examined to investigate the potential for phytotoxicity of diquat residues in aquatic sediments. The diquat adsorption capacity of the aquatic plants ranged from 0.6 to 2.4 mg diquat g dry wt^?1. Forty to seventy percent of the adsorbed diquat could be desorbed with 5 M ammonium chloride. The adsorption capacity of the soil system was about 2.5 mg diquat g dry wt^?1 and approximately 35% of this diquat could be desorbed. Reglone^R inhibited the growth of blue-green algae (Anabaena flos-aquae and Anacystis nidulans) at concentrations greater than 0.03 ppm. Eukaryotic algae were less sensitive, growth of Navicula pelliculosa was inhibited at concentrations exceeding 0.3 ppm and Chlorella vulgaris was unaffected by 3 ppm Reglone. In the presence of soil, growth inhibition by Reglone was eliminated. Reglone was added to a water-soil mixture system at levels up to 334 ppm to simulate chronic usage. Anabaena flos-aquae or Lemna sp. were used to bioassay the availability of the diquat adsorbed to this soil system. Significant growth inhibition of both bioassay plants was observed in soil treated with 33.4 ppm Reglone and the 334 ppm treatment was lethal. These experiments suggest that residual phytotoxicity becomes apparent in this soil system at about 7% of the diquat adsorption capacity. The Reglone adsorption-desorption isotherm of a natural, organic lake sediment was measured to predict the number of Reglone treatments at the recommended application rate before residual phytotoxicity would become apparent.     

Effect of the carbamate pesticide Sevin on the intestinal absorption of some nutrients in the teleost fish,Channa Punctatus

The effect of four concentrations (0.1, 1, 10, and 100 ppm) of Sevin on the rate of uptake of two sugars (glucose and fructose) and an aminoacid (tryptophan) by the intestine of the fresh water snake-head fish,Channa punctatus has been investigated. All four concentrations of the pesticide decreased the rate of transport of the three nutrients. No direct relationship could be established between the concentration of Sevin in the medium and decrease in the rate of transport of nutrients, although, increase in the concentration of Sevin reduced the absorption of nutrients by the intestine to a greater extent. Experiments conductedin vivo andin vitro showed that in both cases the pesticide decreased the brush border enzyme activity.     

A Comprehensive Study of Deep Catalytic Oxidation of Benzene, Toluene, Ethyl Acetate, and their Mixtures over Pd/ZSM-5 Catalyst: Mutual Effects and Kinetics

Reaction behaviors and kinetics of catalytic oxidation of benzene, toluene, and ethyl acetate with feed concentrations in the range of 700–5,000 ppm over Pd/ZSM-5 catalyst were investigated. Results for single components show that ethyl acetate (T ₅₀?=?190–200°C) is more easily oxidized than benzene (T ₅₀?=?215–225°C) and toluene (T ₅₀?=?225–235°C). The conversion of ethyl acetate was increased with the increase of its feeding concentration, while the opposite behaviors were observed for benzene and toluene as their conversion rates were decreased with the increase of the inlet concentration. Different behaviors were observed in catalytic oxidation of volatile organic compound (VOC) multi-components, the presence of benzene or toluene inhibits the conversion of ethyl acetate, and the aromatic hydrocarbons inhibit each other in all cases. Ethyl acetate possesses obvious inhibitory effect on benzene oxidation, while it is interesting to note that ethyl acetate has a promotion effect on toluene conversion. The kinetic data were fitted by the Power-law and Mars–van Krevelen kinetic models. The fitting result shows that the Power-law model is more suitable for predicting the conversion of benzene than the other VOCs, and the Mars–van Krevelen model can accurately express the reaction rate of all investigated VOCs.     

Catalytic Oxidation of Volatile Organic Compounds by 13X Zeolite Coated with nZnO in Presence of UV and Ozone at High Bed Temperature

Catalytic oxidation of benzene, toluene, and ethylbenzene (BTE) on virgin zeolite, nZnO-coated zeolite, with and without UV?+?O₃, at 300 °C bed temperature was investigated using laboratory experiments. The coating was done at three weight ratios of Zn (estimated Zn content in nZnO) to zeolite (0.2:1.0, 0.5:10, 1.0:1.0). The coated adsorbents were examined by scanning electron microscopy, wavelength dispersive X-ray spectroscopy, and Brunauer Emmett Teller analyses. In the catalytic oxidation experiments, the adsorbents were first saturated with BTE by purging an air stream containing a mixture of BTE at 5 ppm each for 28 min. Introduction of UV?+?O₃ on the coated 13X zeolite (0.5:1.0) bed improved the average removal efficiency (RE) of benzene, toluene, and ethylbenzene (with inlet concentration of 5 ppm each) to 68.7, 90.0, and 99.6%, respectively, from the corresponding values of 57.3, 79.9, and 98.5% when no UV?+?O₃ was used. An increase in the coating weight ratio from 0.2:1.0 to 0.5:1.0 had produced a higher RE for benzene only, while a further increase to 1.0:1.0 witnessed a decrease in RE for all three compounds, and more for benzene. Avg RE of BTE decreased with the increase in their inlet concentrations, more significantly for an increase from 5 to 50 ppm and less noticeable for a further increase to 100 ppm. The final oxidation products and intermediate products in the outlet streams from the oxidation and thermal desorption were analyzed which showed predominant compositions of CO₂ followed by BTE and some levels of CO and other volatile organic compounds.     

Mirex incorporation in the environment: Toxicity in two soil macroarthropods and effects on soil community respiration

The KD (knockdown dosage) and LD (lethal dosage) values of mirex were determined for the land isopod Armadillidium vulgare and the soil millipede Oxidus gracilis by feeding with a diet containing different concentrations of technical mirex powder. KD₅₀ and LD₅₀ values for A. vulgare at 10 days exposure were 11.6 ppm and 35.2 ppm, respectively; and for O. gracilis, 5.4 ppm and 198.7 ppm, respectively. The isopod A. vulgare was less susceptible to mirex poisoning as symptomized by knockdown behavior but was killed sooner than the millipede O. gracilis. Poisoned animals showed increased O₂ uptake after two to three days of feeding on mirex diet presumably due to increased muscular activity as induced by elevated oxidative metabolism. Technical mirex showed a significant effect on soil community respiration at 100 ppm concentration after 24 h but no change was observed at the higher concentrations of 500 and 1000 ppm. The addition of mirex as fire ant baits at the rate of 1:100, 1 : 1000, and I :10 000 bait to soil ratio also did not affect soil community respiration, but 02 uptake was nevertheless elevated due to the microbial population (bacteria and fungi) that immediately invaded the bait material.     

Non-target effects of a carbamate and the proteins avidin and aprotinin on in vitro development of a bacterial feeding nematode

A 24-well plate trial was conducted to determine the effects of conventional (oxamyl) and transgenic (avidin and aprotinin) insect control chemicals on the non-target bacterial-feeding nematode Bursilla sp. (Rhabditidae: Nematoda). Treatments were added to agar as pure oxamyl, avidin from egg whites or aprotinin from bovine lung, which was then inoculated with the bacteria Xanthamonas campestris as a food source for the nematodes. Oxamyl was toxic to the nematodes at a concentration of 400 ppm, significantly decreasing adult survival, egg laying and consequent progeny development and survival. The 400 ppm concentration of oxamyl also had a significant negative effect on bacterial growth in two of three experiments. Avidin is a biotin-binding protein and concentrations of 100 and 400 ppm significantly decreased the number of progeny produced by first generation nematodes through an effect on egg development. This effect was not significant (P>0.05) at either 10 or 25 ppm. This is the first report of avidin affecting nematode egg development and suggests a role for biotin in this process. Avidin had no effect on visual bacterial growth. Aprotinin is a protease inhibitor and concentrations up to 400 ppm had no significant effect on nematode development or bacterial growth. These lab-based findings need to be further investigated using plants producing avidin and aprotinin, growing in field soil in order to quantify their impact on environmental processes such as decomposition.     

Inhibitory effects of SO2 on biofiltration of aldehydes

Biofiltration is a suitable method for eliminating volatile biodegradable organic chemical from waste gases. However, if substances inhibiting microbiological activity are present in the waste gas, biofiltration efficiencies will be poor. Results are presented on inhibition of biofiltration by SO₂. Inhibition was observed first in a pilot scale experiment on odor abatement in a food processing factory. Then it was shown in laboratory scale experiments that SO₂. concentrations less than 10 ppm have no measurable effect. A concentration of 40 ppm results in 60% inhibition but original efficiency can be restored when the SO₂ supply is shut off. A concentration of 100 PPM of SO₂ results in complete and permanent inhibition.     

Effects of nutrient supply and below-ground herbivory by Diaprepes abbreviatus L. (Coleoptera: Curculionidae) on citrus growth and mineral content

Three-year-old citrus trees were grown in the greenhouse to study the effects of fertilizer concentration and root herbivory on plant growth and mineral concentration. In separate experiments, sour orange (Citrus aurantium L.) and Swingle citrumelo (C. paradisi Macf. × Poncirus trifoliate L.) plants were treated with a complete fertilizer diluted to provide 25, 100, 200, or 400 ppm N and grown for 7 weeks with or without Diaprepes abbreviatus L. larvae. Increased fertilizer concentration increased the shoot mass and the shoot:root ratio of both sour orange and Swingle citrumelo. Root herbivory also increased the shoot:root ratio by depressing root growth more than shoot growth. Effects of root herbivory on growth were consistent across the four levels of fertilizer concentration, indicating that tolerance is not a function of nutrient status. For both rootstocks, concentrations of nitrogen in roots and leaves increased with fertilizer concentration, and C:N ratios decreased. In sour orange, root herbivory most strongly affected the concentration of carbon in roots, whereas in Swingle citrumelo, root herbivory most strongly affected leaf nitrogen. In general, herbivory reduced mineral concentrations of roots but the strength, and sometimes the direction, of herbivore effects varied significantly among fertilizer treatments. This research indicates that application of excess, balanced fertilizer is unlikely to offset growth reductions due to root herbivory by D. abbreviatus, and suggests that supplementation of specific nutrients may be of value.     

Effect of fluoride on axenic cultures of diatoms

Algal bioassay studies on the effect of F concentrations on diatoms Nitzschia palea (freshwater) and Amphora coffeaeformis (brackishwater) were conducted in the laboratory. Significant enhancement of growth occurred in N. palea at F concentrations between 10 and 110 mg L^?1. In A. coffeaeformis statistically significant stimulation occurred at 70 mg L^?1 F and above 90 mg L^?1 F the growth declined. The results indicate that the diatom N. palea and A. coffeaeformis can tolerate high F concentration.     

Studies of toxic effects of Hg(II) on Pistia stratiotes

The uptake of Hg(II) and toxicity effect of the metal on some biochemical parameters in Pistia stratiotes L. were studied. The uptake of Hg(II) by the plants gradually increased with increase in concentration of Hg(II) in the culture medium. Maximum accumulation of Hg(II) was noted within 1 day. Maximum removal (about 90%) of Hg(II) was recorded below 20 ppm Hg(II). Accumulation of Hg(II) in roots was about four times higher than that in shoots. At 20 ppm, Hg(II) promoted senescence of Pistia plants by decreasing chlorophyll, protein, RNA, dry weight and activities of catalase and protease as well as increasing free amino acid content, peroxidase activity and the ratio of acid to alkaline pyrophosphatase activity over control values. At Hg concentrations below 20 ppm, these constituents were least affected.     

Evaluation of bioremediation and detoxification potentiality of Aspergillus niger for removal of hexavalent chromium in soil microcosm

Aspergillus niger isolated from soil of leather tanning effluent had higher activity to remove chromium then the other fungal isolates. The potency of A. niger was evaluated in shake flask culture by absorption of chromium at pH 6, temperature 30 °C. The toxicity of chromium evaluated in petriplates and soil microcosm seed bioassay test had indicated increase in toxicity with the higher concentration of chromate. A. niger introduced in soil microcosm (40% moisture content) with different concentration of chromate (250, 500, 1000, 1500 and 2000 ppm) removed more than 70% chromium in soil contaminated by 250 and 500 ppm of chromate. However, chromium-contaminated soil (2000 ppm of potassium chromate) mixed with compost (5% and 10%) significantly removed chromium in presence of fungus, A. niger. The results of chromate toxicity in the wheat plants revealed that the peroxidases was induced due to increase of metal stress which was reversed in soil microcosm amended with compost.     

Determination of linear response in the detection of aroma compounds by atmospheric pressure ionization-mass spectrometry (API-MS)

Linearity and detection thresholds of atmospheric pressure ionization-mass spectrometry (API-MS) were determined for 11 aroma compounds in air at concentrations ranging from 50 ppb to approximately 450 ppm (moles of volatile per mole of air). In most cases, the protonated molecular ion (i.e., m/z = M + 1) was the base peak throughout the range; however, some compounds showed an increase in fragmentation at lower concentrations. Detection limits varied greatly (from 50 ppb to 14 ppm) depending upon the aroma compound being measured. The linear range was also strongly dependent upon the aroma compound, with values ranging from <10-fold change in concentration to >4000-fold change in concentration depending upon the volatile being studied. The two volatiles with poor detection thresholds also exhibited the smallest linear range. Most compounds had linear ranges of >200. There was no apparent relationship between gas-phase basicity and either detection limit or linear range.     

Effect of Copper(II), Lead(II), and Zinc(II) on Growth and Sporulation of Halophytophthora from Taiwan Mangroves

This study evaluated the effect of lead (Pb(II)), zinc (Zn(II)) and copper (Cu(II)) on growth and sporulation of four Halophytophthora species (Halophytophthora vesicula, Halophytophthora elongata, Halophytophthora spinosa var. lobata, and an oogonia-producing Halophytophthora sp.) isolated from different mangrove sites in Taiwan. Results show that all isolates grew well or even better at 1 ppm concentration of the heavy metals tested. Growth of all test isolates was totally inhibited at 500 ppm, except for H. spinosa var. lobata exposed to Zn(II). For sporulation, all isolates produced moderate to abundant zoosporangia or oogonia at 1 ppm Pb(II) and Zn(II). Production of zoosporangia by H. vesicula, H. elongata and H. spinosa var. lobata was significantly affected or totally inhibited at 1 ppm Pb(II) and Zn(II) and all concentrations of Cu(II). Abnormal oogonia were produced by Halophytophthora sp. at 10 ppm Cu(II) and 100 ppm of the three heavy metals. In general, Cu(II) and Zn(II) were found to be the most toxic, and the least toxic was Pb(II). H. spinosa var. lobata was the most tolerant to all the heavy metals, while H. vesicula and H. elongata were the most sensitive. Results of this study shows that increased concentrations of Pb(II), Cu(II), and Zn(II) in the mangrove environment can significantly affect growth and impair normal reproduction of Halophytophthora species.     

不同二氧化碳浓度处理对棉花生长发育和产量形成的影响

借助于OTC-1型开顶式气室进行了700ppm、500ppm和自然条件下二氧化碳浓度对棉花影响的模拟诊断试验，结果表明：二氧化碳浓度升高，特别是二氧化碳浓度倍增对棉花生育进程、生物量和产量等均有明显的正效应。     

紫茎泽兰叶片凋落物对入侵地4 种草本植物的化感作用

为了明确紫茎泽兰叶片凋落物对入侵地草本植物的化感作用, 研究了不同浓度紫茎泽兰叶片凋落物水提液对入侵地草本植物多年生黑麦草、白三叶、辣子草和紫花苜蓿种子萌发和幼苗生长的影响, 同时结合土培试验研究了叶片凋落物在入侵地土壤中的化感作用。结果表明, 除多年生黑麦草外, 水提液对其他3 种草本植物种子萌发均产生了显著的化感抑制作用, 且水提液的浓度越高抑制效果越强; 低浓度水提液对紫花苜蓿和辣子草的幼苗生长存在显著化感促进作用, 高浓度的水提液对除多年生黑麦草外的其他3 种植物幼苗的生长存在显著化感抑制作用, 水提液对多年生黑麦草幼苗生长的影响不显著; 土壤中按照50 g·kg^-1的比例添加叶片凋落物后, 显著抑制了白三叶的生长, 而添加活性炭后, 白三叶的单株生物量相对于未添加活性炭的处理增加71.25%, 进一步证实叶片凋落物在土壤中的化感抑制作用。这说明外来入侵植物紫茎泽兰可能通过其叶片凋落物在入侵地土壤中降解, 释放化感物质, 抑制伴生植物的种子萌发和幼苗生长, 为自身创造有利的生长环境, 实现其成功入侵和扩张。     

Sugarmill effluent effects on growth,photosynthetic pigments and nutrient uptake in wheat seedlings in aqueous vs. soil medium

Germination, seedling growth, concentrations of photosynthetic pigments and nutrient uptake inTriticum vulgare L. (Var. W-H-147) were studied in response to sugarmill effluent application (10% concentration) in aqueous Vs. soil medium. The effluent rich in various nutrients showed particularly high concentration of sodium. Germination was not affected by the effluent treatment. Seedling growth was reduced significantly by the effluent in aqueous medium, but not in soil. The effluent treatment increased the concentrations of various pigments, however, the pigment ratios got changed in the aqueous medium only. The uptake of nitrogen, magnesium and carbon by the seedlings decreased while that of calcium, sodium and phosphorus increased in effluent treated plants, the changes being more marked in aqueous medium except for phosphorus. In the effluent treated plants, uptake of potassium and chloride increased in aqueous medium, hut decreased sharply in soil.     

Phytotoxicity of organic acids as influenced by montmorillonite,hydroxy‐Al montmorillonite and phosphate fertilization

Abstract

The germination and growth of wheat seedlings were studied at pH 5.5 in liquid growth media with organic acids in concentrations ranging from 800 to 1200 ppm, before and after interaction of the organic acids with montmorillonite and hydroxy‐Al montmorillonite. Germination was not affected by the organic acids, but subsequent growth was dependent on the kind and concentration of organic acid in the growth medium. Acetic acid was more inhibitory than citric acid. Gallic acid polymerized at pH 5.5 and was phytotoxic at 1200 ppm. Interaction of organic acids with montmorillonite and hydroxy‐Al montmorillonite reduced the concentration of organic acids in solution by adsorption. Despite this reduction in concentration the phytotoxicity of the growth media was enhanced after the interaction. This was caused by the dissolution of surface Al and the effect was more pronounced in cases where hydroxy‐Al interlayered montmorillonite was the adsorbent. Additions of P as KH₂PO₄ alleviated the phytotoxicity of organic acids but not the associated Al toxicity. The amount of P lost by adsorption or precipitation was dependent on the form of Al in the growth media.     

Volatile organic compounds in water and sediment from the Morava and the Danube Rivers (Slovakia) using purge and trap injection and gas chromatography

Purge and trap injector (PTI) with high resolution gas chromatography (HRGC) was used to determine the concentration levels of volatile organic compounds (VOCs) in water and sediments from the Morava and the Danube Rivers. Thus the average concentrations of volatile n-alkanes (C₆-C₁₃) in water and sediments were found to be 0.02—1.33 μg/l and 0.04–105 μg/kg wet weight respectively. While the average concentrations of volatile aromatics in water and sediments were found to be 0.07–3.62 μg/l and 0.08–290 μg/kg wet weight respectively. In general different concentration levels were found at different locations, and at different time periods. With PTI-HRGC small sample size (5–20 ml) of water and (10–20 g) of sediments were used to analyse the VOCs in a simple, rapid method, with low background contamination since the system is completely closed. Relatively higher concentrations of VOCs were found in water and sediment samples from the Morava in comparison with those from the Danube, and higher concentration levels were found in spring time than in summer time.     

Arsenic Uptake from Arsenic-Contaminated Water Using Hyperaccumulator Pteris vittata L.: Effect of Chloride, Bicarbonate, and Arsenic Species

High As groundwater normally contained high concentrations of Cl^? and HCO ₃ ^? . This study examined the effects of Cl^?, HCO ₃ ^? , and As species on As uptake by hyperaccumulator Pteris vittata. Plants were exposed hydroponically to 5.0?mg/L As(III) or As(V) in the presence of 0, 0.5, 1, 2, 5, 10, and 20?mM of Cl^? or HCO ₃ ^? for 10?days. Addition of high Cl^? concentrations (>10?mM) slightly inhibited P. vittata growth (biomass), while generally had no significant effect on plant As uptake. High solution pH resulted in reduced plant growth and As uptake, which attributed to the inhibitory effects in HCO ₃ ^? treatments with the high pH of the high HCO ₃ ^? concentration. It was speculated that addition of HCO ₃ ^? (<20?mM) would have no significant effect on plant growth and As uptake. The inhibitory effect of HCO ₃ ^? on As translocation was less apparent in the As(III) solutions than the As(V) solutions. For the high As groundwater with As(III) as the predominant species, high pH, instead of high concentrations HCO ₃ ^? and Cl^?, was expected to inhibit As uptake. The results suggested that optimum plant growth and maximum As hyperaccumulation could be achieved by adjusting solution pH in the growth media (around 7.2).     

Response of freshwater alga Scenedesmus to triazine herbicides

The effect of three triazine herbicides namely, Gardoprim, Gesapax and Igran on the freshwater alga, Scenedesmus sp., was studied. Growth rate, chlorophyll (a) content, and ratio of chlorophylls (a/b) tend to decrease as the concentration of herbicides in the bioassay media was increased. The inhibitory effect of the studied herbicides was in the following the order: Igran > Gesapax > Gardoprim. Obtainable results reflect the relation between chemical structure and toxicity even within a chemically related group of herbicides. Uptake of the studied compounds by Scenedesmus algal cells decreased as the concentration of herbicides in the media was increased. The pH of the bioassay media showed gradual increase as algal growth proceeded, whereas in media containing inhibitory levels of the triazines, the pH value was unaffected. Microscopical examinations of Scenedesmus in all tested cultures showed marked morphological changes. In the case of inhibitory concentrations, the unicellular forms increased in numbers compared to Scenedesmus in the normal four-cell state. Statistical analysis revealed that significant relation existed between herbicide concentrations and chlorophyll content.