Plant-accelerated dissipation of phenanthrene and pyrene from water in the presence of a nonionic-surfactant

Plant-accelerated dissipation of phenanthrene and pyrene in water in the presence of a nonionic-surfactant (Brij35) was studied. The mechanisms involved were evaluated, based on the investigation of plant uptake of these compounds from water with Brij35. The presence of ryegrass (Lolium multiflorum Lam) clearly enhanced the dissipation of tested PAHs in water with 0-296 mg l(-1) Brij35. The first-order rate constants (K), calculated from the first-order kinetic models for these PAH degradation (all significant at P < 0.05, n=8), of phenanthrene and pyrene in the presence of ryegrass were 16.7-50% and 47.1-108% larger than those of plant-free treatments, whereas half-lives (T1/2) of the former were 14.3-33.4% and 32.0-52.0% smaller than the latter, respectively. However, the promotion of PAH dissipation by ryegrass was found to significantly decrease with increasing Brij35 concentrations. In the range of 0-296 mg l(-1), low concentrations (< or = 74.0 mg l(-1)) of Brij35 generally enhanced plant uptake and accumulation of phenanthrene and pyrene, based on the observed plant concentrations and accumulated amounts of these chemicals from water. In contrast, Brij35 at relatively high concentrations (> or = 148 mg l(-1)) markedly restricted plant uptake of these PAHs. Plant accumulation of phenanthrene and pyrene accounted for 6.21-35.0% and 7.66-24.3% of the dissipation enhancement of these compounds from planted versus unplanted water bodies. In addition, plant metabolism was speculated to be another major mechanism of plant-accelerated dissipation of these PAHs in water systems. Results obtained from this study provided some insight with regard to the feasibility of phytoremediation for PAH contaminated water bodies with coexisted contaminants of surfactants.     

Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action

We evaluated wheat straw biochar produced at 450 °C for its ability to influence bioavailability and persistence of two commonly used herbicides (atrazine and trifluralin) with different modes of action (photosynthesis versus root tip mitosis inhibitors) in two contrasting soils. The biochar was added to soils at 0%, 0.5% and 1.0% (w/w) and the herbicides were applied to those soil-biochar mixes at nil, half, full, two times, and four times, the recommended dosage (H₄). Annual ryegrass (Lolium rigidum) was grown in biochar amended soils for 1 month. Biochar had a positive impact on ryegrass survival rate and above-ground biomass at most of the application rates, and particularly at H₄. Within any given biochar treatment, increasing herbicide application decreased the survival rate and fresh weight of above-ground biomass. Biomass production across the biochar treatment gradient significantly differed (p < 0.01) and was more pronounced in the case of atrazine than trifluralin. For example, the dose-response analysis showed that in the presence of 1% biochar in soil, the value of GR₅₀ (i.e. the dose required to reduce weed biomass by 50%) for atrazine increased by 3.5 times, whereas it increased only by a factor of 1.6 in the case of trifluralin. The combination of the chemical properties and the mode of action governed the extent of biochar-induced reduction in bioavailability of herbicides. The greater biomass of ryegrass in the soil containing the highest biochar (despite having the highest herbicide residues) demonstrates decreased bioavailability of the chemicals caused by the wheat straw biochar. This work clearly demonstrates decreased efficacy of herbicides in biochar amended soils. The role played by herbicide chemistry and mode of action will have major implications in choosing the appropriate application rates for biochar amended soils.     

Uptake and Modeling of Pesticides by Roots and Shoots of Parrotfeather (Myriophyllum aquaticum) (5 pp)

Intention, Goal, Scope, Background Aquatic plants have a great potential to function as in situ, on-site biosinks and biofilters of pollutants. They are used for phytoremediation and phytotoxicity studies. Pesticide uptake studies are very important to predict contaminant accumulation, translocation, and transformation. There are a lot of models which have been developed for emergent plants, but there are not any existing models for submerged aquatic plants for assessing pesticide uptake. Objective In this study, uptake of selected pesticides in parrotfeather (Myriophyllum aquaticum) were studied and the results were modeled with the aid of Log Kow and the concentration of pesticides. At the end, the developed model was compared to other existing models. Methods The test was conducted with parrotfeather as a model plant. The bioassay and cultivation of this plant were examined. Pesticide uptake by roots and shoots was determined using 14C-radiolabeled materials. Results and Discussion The results were fitted with an equation that showed a relationship between uptake and lipophilicity of pesticides. The model was compared with other pesticide uptake models developed for other plants. Atrazine and cycloxidim were taken up more by roots than by shoots in comparison to other pesticides used. The total uptake, both in shoots and roots, was lower than for terbutryn and trifluralin. The best appropriate model was developed from the results against the other models seen in the literature. The concentration factors (Root Concentration Factor (RCF) and Submerged Shoot Concentration Factor (SSCF)) increased with a higher Kow of the substances. The Submerged Shoot Concentration Factor (SSCF) revealed a better relationship of the chemicals than did the Root Concentration Factor (RCF). Conclusions In this study, an uptake model was developed for rooted, submerged aquatic plants. Further studies are necessary to develop and compare models with different plants and pesticides. Recommendation and Outlook Such studies as this one may be extended to other environmental pollutants in the aquatic ecosystem and may be employed to evaluate the possibility of using different plants in phytoremediation studies.     

Causes of phytotoxicity of metsulfuron-methyl bound residues in soil

The bioavailability and phytotoxicity of bound residues of metsulfuron-methyl were studied using 14C-labeling and bioassay with oil rape (Brassica napus L.). Soil bound residues at the concentration of 0.27 and 0.53 nmol g(-1) resulted in significant inhibition of oil rape seedling growth. The biologically active component of the bound residues was identified to be metsulfuron-methyl parent compound. Other metabolites, including the hydrolysis product 2-methylformate-benzenesulfonamide, showed no toxicity to the test species. This study suggests that residues of metsulfuron-methyl bound previously to the soil matrix could be again released upon planting. The phytotoxicity of metsulfuron-methyl bound residues was mainly caused by the metsulfuron-methyl parent compound that became available during plant growth.     

Fate of 14C‐lindane in a rice‐fish model ecosystem*

Abstract

A model ecosystem has been used to evaluate the impact of ¹⁴C‐lindane on rice‐fish agricultural system. The distribution of ¹⁴C‐residues among the constituents of the model ecosystem was studied over a period of 90 days. The insecticide was found to be readily absorbed by the roots and translocated to all parts of the rice plant. The peak level in the shoots (26 ppm) and roots (105 ppm) of plants was reached to within three weeks. Lindane was concentrated in fish and residues as high as 90 ppm could be detected after 30 days.

The major part of the residues present in the different constituents of the ecosystem could be extracted with hexane and proved to contain soley the parent compound. The data obtained show that lindane possesses a relatively low biodegradability in fish and in rice plant. The insecticide accumulates in fish and rice plant to considerable extent.     

Bioavailability and biological activity of wheat-bound chlorpyrifos-methyl residues in rats.

Wheat grain was treated with 14C-chlorpyrifos-methyl to generate bound residues for determining their bioavailability to rats. In a parallel experiment, bound residues were prepared with non-labelled chlorpyrifos-methyl to determine possible adverse effects in rats fed the grain-bound residue for 28 and 90 days. Two dose levels of 10 and 50 ppm were initially used on the grain. The 10 ppm led to the formation of 25.1% bound residues (2.51 ppm) after 6 months as determined by radiomeasurement. The higher dose was assumed to form 12.55 ppm bound residues. When 14C-bound residues were fed to male rats for 24 hours, the animals eliminated 75% of the radioactivity in urine, 7% in expired air and 8% in faeces after 3 days, indicating that the bound residues were highly bioavailable. A further "bioavailable" amount (4%) was found in selected organs.     

Speciation of Cd and Zn in contaminated soils assessed by DGT-DIFS, and WHAM/Model VI in relation to uptake by spinach and ryegrass

A pot experiment was carried out to investigate the impact of Cd and Zn extractability in soil and speciation in pore water of industrial contaminated soils, on metal concentration in a metal sensitive species like spinach (Spinacia oleracea) and a more metal tolerant species like Italian ryegrass (Lolium multiflorum). For chemical speciation of Cd and Zn in pore water, WHAM/Model VI version 6.0 was used. The DGT technique was used to determine the effective concentration, C(E), of Cd and Zn in soils. The free ion activity in pore water correlated well with the contents in plants, and there was a linear relationship between the C(E) values and the concentration of Cd and Zn in both spinach and ryegrass in the non-toxic range. However, the C(E) values usually overestimated the plant contents when plants, particularly the spinach plants, were subjected to toxic concentration in the pore water. Metal uptake decreased in plants affected by toxicity, whereas metal binding to the Chelex resin did not. Thus, we found no linear relationship between the C(E) and metal contents in spinach, whereas a linear relationship was found between C(E)-Zn and the Zn concentration in ryegrass (r2=0.96, p<0.001). For Cd in ryegrass this relationship was weak (r2=0.53, p=0.18). This study indicates that the transport of metals from labile metal pools to the DGT-resin is linearly related to plant uptake only when plants are growing well, and that the applicability of DGT as an indicator for plant uptake seems species dependent.     

Plant availability of bound anilazine residues in a degraded loess soil

Abstract

The relative biological availability of [benzene ring‐U‐¹⁴C] and Ctriazine‐U‐¹⁴C] anilazine for maize plants was studied in a degraded loess soil in a standardized microecosystem. The total uptake of radiocarbon in the course of the 4‐week experiment was 3.1 and 4 % respectively of the radioactivity applied if anilazine was uniformly mixed into the soil immediately before beginning the experiment. However, if anilazine was subjected to a degradation at 65 % of the maximum water holding capacity of the soil and temperatures varying daily between 16 and 27°C for 100 days before the plant experiment then the uptake was reduced to 0.4 or 0.7 % respectively. The uptake from soil with non‐extractable (bound) anilazine residues was similarly low. The mineralization rate of aged and bound anilazine residues was below 0.1 % of the radioactivity applied. Up to 2/3 of the radioactivity present in the soil after the plant experiment remained in the humic fraction.     

Predicting radium availability and uptake from soil properties

The results of a potted soil experiment to determine the soil and plant factors ruling radium availability and uptake by ryegrass and clover are described. Nine soils with distinct soil characteristics were spiked with 226 Ra. They were thoroughly characterized and the solid liquid partitioning coefficient, Kd, was determined. Kd ranged from 38 l kg(-1) to 446 l kg(-1) (average: 188+/-156 l kg(-1)) and was linearly related to cation exchange capacity (CEC) and organic matter (OM) content. The soil-to-plant transfer factor (TF) was significantly affected by the chemical properties of the soils and ranged from 0.054 kg kg(-1) to 0.719 kg kg(-1) for ryegrass and from 0.034 kg kg(-1) to 1.494 kg kg(-1) for clover. Overall, no significant difference in TF between ryegrass and clover was observed. TF was related to Kd, to CEC, OM (for ryegrass only when excluding one soil) and the calcium concentration in the soil solution (for both plants if excluding one soil). Radium flux were calculated from the radium concentration in the soil solution and the evapotranspiration, to predict total radium uptake derived from shoot radium concentration and biomass yield. It was found that radium uptake could be predicted from the radium flux (R2=0.61 and 0.83 for ryegrass and clover, respectively). Higher predictability (R2=0.70 and 0.91 for ryegrass and clover, respectively) was obtained when relating total radium uptake to a radium flow considering competition effects at the root surface by bivalent cations.     

Effects of a non-ionic surfactant (Tween-80) on the mineralization, metabolism and uptake of phenanthrene in wheat-solution-lava microcosm

Effects of a non-ionic surfactant (Tween-80) on the mineralization, metabolism and uptake of phenanthrene in wheat-solution-lava microcosm were studied using 14C-labeled phenanthrene. The mineralization and metabolism of phenanthrene were fast in such a system. At least 90% of the applied phenanthrene were transformed within 24 days. Only 0.3% of the applied 14C-activity were identified to be the parent phenanthrene. Most of the applied 14C-activity (70%) was recovered from wheat, in which ca. 70% were associated with wheat shoots (stems and leaves) and ca. 30% wheat roots. 33% and 20% of the applied 14C-activity had been constructed into wheat tissues of shoots and roots, respectively. The 14C-activity recovered in forms of CO2 and volatile organic chemicals (VOCs) was 12-16% and 4-5%, respectively. The major metabolites of phenanthrene were polar compounds (18% of the applied 14C) and only 2.1% were identified as non-polar metabolites. No phenanthrene was found in wheat shoots indicating that it could not be transported from roots to upper parts of the plant but in form of metabolites (mostly polar metabolites). Foliar uptake of 14C-activity via air in form of 14CO2 occurred. The presence of Tween-80 significantly enhanced the degradation of phenanthrene, which could be attributed to its increase of microbial activities in the system. Tween-80 also significantly (P < 0.05) reduced the phenanthrene level in wheat roots, which probably resulted from desorption of phenanthrene from root surface caused by the surfactant.     

Strategies for including vegetation compartments in multimedia models

The incentives for including vegetation compartments in multimedia Level I, II and III fugacity calculations are discussed and equations and parameters for undertaking the calculations suggested. Model outputs with and without vegetation compartments are compared for 12 non-ionic organic chemicals with a wide variety of physical-chemical properties. Inclusion of vegetation compartments is shown to have a significant effect on two classes of chemicals: (1) those that are taken up by atmospheric deposition and (2) those that are taken up by transpiration through the plant roots. It is suggested that uptake from the atmosphere is important for chemicals with logK(OA) greater than 6 and a logK(AW) of greater than -6. Plant uptake by transpiration is important for chemicals with logK(OW) less than 2.5 and a logK(AW) of less than -1. At logK(OA) > 9 atmospheric uptake is dominated by particle-bound deposition and the importance of partitioning to vegetation is largely dependent on the relative magnitude of the particle deposition velocities to soil and vegetation. These property ranges can be used to determine if a chemical will significantly partition to vegetation. If the chemical falls outside the property ranges of the two classes it will probably be unnecessary to include vegetation in models for assessing environmental fate. The amount of chemical predicted to partition to vegetation compartments in the model is shown to be highly sensitive to certain model assumptions. Further experimental research is recommended to obtain more reliable equations describing equilibrium partitioning and uptake/depuration kinetics.     

Investigation of uptake, translocation and fate of trichloroacetic acid in Norway spruce (Picea abies/L./Karst.) using 14C-labelling.

[1,2-14C]TCA of a high specific activity (3.7 GBq/mmol) and appropriate radioindicator techniques were used, to study the effect of trichloroacetic acid (TCA) on conifers. Easy uptake of TCA from soil through spruce roots and its further translocation by the transpiration stream up to the needles (where damage of the photosynthetic apparatus occurs) has been proved. During the growth period, after one-shot load of TCA, the uptake was most intensive in current-year needles at first; over an extended period a decrease in the level of [1,2-14C]TCA-derived radioactivity was found in the current-year needles while in older needles (C + 2), the level rose. Symptoms of TCA biodegradation and/or metabolism were found in the plant/soil system under study. During an eight-week exposure significant losses of radioactivity into the atmosphere were noticed, at least a part of them in the form of carbondioxide. The results of these more or less preliminary experiments demonstrated the suitability and advantages of the radioisotopic technique used.     

Effect of rhamnolipids on the uptake of PAHs by ryegrass

A hydroponic experiment was conducted to investigate the effect of rhamnolipids, a biosurfactant, on the uptake of polycyclic aromatic hydrocarbons (PAHs) by ryegrass. Results showed that rhamnolipids could enhance the uptake of PAHs by ryegrass roots. With increasing concentration of rhamnolipids, the PAH content in ryegrass roots initially increased and then decreased, while the PAH content in ryegrass shoots did not change. Batch studies also showed that the sorption of phenanthrene by fresh ryegrass roots was dependent on rhamnolipid concentration and showed the same trends as the uptake experiment. The increase of permeability of ryegrass root cells with the increase of rhamnolipid concentration may lead to the initial enhancement of PAH content in ryegrass roots, and the decrease of PAH adsorption onto the root surface with further increase of rhamnolipids led to the decrease of PAH content in ryegrass roots.     

Modeling uptake kinetics of cadmium by field-grown lettuce

Cadmium uptake by field grown Romaine lettuce treated with P-fertilizers of different Cd levels was investigated over an entire growing season. Results indicated that the rate of Cd uptake at a given time of the season can be satisfactorily described by the Michaelis-Menten kinetics, that is, plant uptake increases as the Cd concentration in soil solution increases, and it gradually approaches a saturation level. However, the rate constant of the Michaelis-Menten kinetics changes over the growing season. Under a given soil Cd level, the cadmium content in plant tissue decreases exponentially with time. To account for the dynamic nature of Cd uptake, a kinetic model integrating the time factor was developed to simulate Cd plant uptake over the growing season: C Plant=C Solution.PUF max.exp[-b.t], where C Plant and C Solution refer to the Cd content in plant tissue and soil solution, respectively, PUF max and b are kinetic constants.     

Bioavailability of dissolved organic nitrogen in treated effluents.

The research objective was to assess dissolved organic nitrogen (DON) bioavailability in wastewater effluents from a pilot-scale nitrification plant and a laboratory-scale total nitrogen (TN) removal plant. The DON bioavailability was assessed using a 14-day bioassay protocol containing bacterial and algal inocula. Nitrogen species, dissolved organic carbon, chlorophyll a, and biomass (as total suspended solids and culturable cell counts) concentrations were measured to assess DON bioavailability. The results showed an increase in algal chlorophyll a concentration, with a concurrent increase in algal biomass over time; increased bacterial counts and a decrease in DON concentration over time; and increased carbon-to-nitrogen ratio at the end of the 14-day bioassay, indicating effluent DON bioavailability to algae and bacteria. Approximately 18 to 61% of the initial DON in low-total-nitrogen wastewater effluent (TN = 4 to 5 mg/L) sample was bioavailable. The results show that bacteria and algae uptake and release DON during their growth.     

Fate of anilide and aniline herbicides in plant-materials-amended soils

The fate of herbicides trifluralin, pendimethalin, alachlor and metolachlor in paddy field soils amended with plant materials was investigated. The plant materials were purple sesbania, vegetable soybean and rice straw. The investigation was performed at two temperatures (25 and 40 degrees C) and two soil water moistures (60 and 90% water-holding capacity). The results showed linear and Freudlich equations described the adsorption of amide compound to soil. Adsorption coefficient (K(d)) fit to linear equation were in general greater in plant material-amended soils than in non-amended soil, especially in soil amending with rice straw. Increasing temperature and soil water moisture content shortened the half-lives of compounds in various treated soils. The movement of compounds in the soil columns showed the maximum distribution of aniline type compound, trifluralin and pendimethalin, appeared at the upper top of 0 to 5 and 0 to 10 cm of soil column, respectively, and of anilide type, alachlor and metolachlor, were distributed at 0 to 25 cm of the soil column. The mobility of chemicals in the different treated soils was simulated by the behavior assessment model (BAM). There was no significant difference among different plant material incubated soils on dissipation and mobility of compounds in soils.     

The formation of bound residues of diazinon in four UK soils: implications for risk assessment

The behaviour of diazinon in the soil determines the likelihood of further pollution incidents, particularly leaching to water. The most significant processes in the control of the fate of diazinon in the soil are microbial degradation and the formation of bound residues. Soils from four sites in the UK were amended with diazinon and its ¹⁴C labelled analogue and incubated for 100 days. After 0, 10, 21, 50 and 100 days, the formation of bound residues was assessed by solvent extraction, and the microbial degradation of diazinon by mineralisation assay. In microbially active soils, diazinon is degraded rapidly, reducing the risk of future pollution incidents. However, where there was limited mineralisation there was also significantly lower formation of bound residues, which may lead to water pollution via leaching. The formation of bound residues was dependent on extraction type. Acetonitrile extraction identified bound residues in all soils, with the bound residue fraction increasing with increasing incubation time.     

Metabolism of the environmental estrogen bisphenol A by plant cell suspension cultures

The metabolism of the environmental estrogen bisphenol A (BPA) was studied in heterotrophic plant cell suspension cultures of soybean (Glycine max), wheat (Triticum aestivum), foxglove (Digitalis purpurea), and thorn apple (Datura stramonium), which were regarded as metabolic model systems for intact plants. Three main metabolic routes of BPA were observed in the tissues. Most of the radioactivity found in the cell extracts consisted of carbohydrate conjugates of BPA amounting to about 85% (foxglove), 80% (wheat), 7% (soybean) and 15% (thorn apple) of applied 14C. The second main route was formation of non-extractable residues. Portions detected were low in foxglove (3.9% of applied 14C), moderate in wheat (13.5%), high in thorn apple (27.4%) and soybean (49.4%). With thorn apple, BPA derived bound residues were preponderantly resistant towards acid treatment; only traces of BPA were released. The third route was the formation of a highly polar, presumably polymeric material detected in media of soybean and thorn apple (29.3% and 36.0% of applied 14C, respectively). The mechanism of its formation remained unknown. In thorn apple, this highly polar material was formed extremely rapidly, and was considerably stable. Only traces of BPA were liberated by hydrolytic treatment with cellulase or acid. During hydrolysis experiments with glycoside fractions, non-extractable residues and highly polar materials, low amounts of presumably primary metabolites of BPA (up to 6% of applied 14C) were detected besides the parent compound; their chemical structures remained unclear.     

Influence of different acid and alkaline cleaning agents on the effects of irrigation of synthetic dairy factory effluent on soil quality, ryegrass growth and nutrient uptake

The aim of this study was to examine the effects of replacement of phosphoric acid with nitric or acetic acid, and replacement of NaOH with KOH, as cleaning agents in dairy factories, on the effects that irrigation of dairy factory effluent (DFE) has on the soil–plant system. A 16-week greenhouse study was carried out in which the effects of addition of synthetic dairy factory effluent containing (a) milk residues alone or milk residues plus (b) H₃PO₄/NaOH, (c) H₃PO₄/HNO₃/NaOH or (d) CH₃COOH/KOH, on soil’s chemical, physical and microbial properties and perennial ryegrass growth and nutrient uptake were investigated. The cumulative effect of DFE addition was to increase exchangeable Na, K, Ca, Mg, exchangeable sodium percentage, microbial biomass C and N and basal respiration in the soil. Dry matter yields of ryegrass were increased by additions of DFE other than that containing CH₃COOH. Plant uptake of P, Ca and Mg was in the same order as their inputs in DFE but for Na; inputs were an order of magnitude greater than plant uptake. Replacement of NaOH by KOH resulted in increased accumulation of exchangeable K. The effects of added NaOH and KOH on promoting breakdown of soil aggregates during wet sieving (and formation of a?<?0.25 mm size class) were similar. Replacement of H₂PO₄ by HNO₃ is a viable but CH₃COOH appears to have detrimental effects on plant growth. Replacement of NaOH by KOH lowers the likelihood of phytotoxic effects of Na, but K and Na have similar effects on disaggregation.     

Biodegradation of trifluralin in Harran soil

Degradation of trifluralin (alpha, alpha, alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was investigated in soils taken from three different locations at Harran region of Turkey under laboratory conditions. Surface (0-10 cm) soils, which were taken from a pesticide untreated field Gürgelen, Harran-1 and Ikizce regions in the Harran Plain. were incubated in biometer flasks for 350 days at 25 degrees C. Ring-UL-14C-trifluralin was applied at the rate of 2 microg g(-1) with 78.7 kBq radioactivity per 100 g soil flask. Evolved (14)CO2 was monitored in KOH traps throughout the experiment. Periodically, soil sub-samples were removed and extracted by supercritical fluid extraction (SFE). Unextractable soil-bound 14C residues were determined by combustion. During the 350 days incubation period 6.6, 5.4, and 3.3/' of the applied radiocarbon was evolved as (14)CO2 from the Harran-1, Gürgelen, and Ikizce soil, respectively. At the end of 350 days the SFE-extractable and bound 14C-trifluralin residues were 39.0 and 29.2% of the initially applied herbicide in Gürgelen soil. The corresponding values for Harran-1 and Ikizce soils were 36.2, 28.4% and 41.6, 18.5% respectively.