A simulation model (PostPLANT-Soil) for predicting pesticide concentrations in succeeding leafy vegetables: II. Validation with experimental data on plant uptake in a growth chamber.

We validated a simulation model (PostPLANT-Soil) for predicting pesticide concentrations in succeeding leafy vegetables reported in our first paper in this series, which includes the pesticide sorption process into plant roots. As a result of the model validation with the measured data from a plant uptake study in a growth chamber, the model successfully simulated the concentration changes of pesticides in a plant shoot. However, the simulated shoot concentrations for several pesticides were overestimated compared to the measured values. The leafy vegetable (Brassica rapa) used in this study probably has a high metabolic ability for the fungicide flutolanil from the result of the uptake study under a hydroponic condition.

A simulation model (PostPLANT-Soil) for predicting pesticide concentrations in succeeding leafy vegetables: I. Validation with experimental data in a Japanese Andosol field.

We developed a simulation model for predicting pesticide concentrations in succeeding leafy vegetables (PostPLANT-Soil), which includes the process of pesticide uptake from plant roots. To validate the model, we compared pesticide concentrations simulated by the model with values measured from field experiments in an upland Andosol. The model validation showed that pesticide concentrations in the plant shoot were correlated with the concentrations in the soil solution rather than those of the water-extracted pesticides. The model successfully simulated the concentration changes in plant shoots when the simulated concentrations of the pesticides in the soil solution were fitted to the measured values by considering the key parameter - the corrective coefficient for the soil adsorption coefficient. However, the simulated shoot concentrations at the appropriate harvest period exceeded the measured values. This indicates that the leafy vegetable used in this study may have some metabolic capacity for the pesticides.

Change of clopyralid concentration in recycled beef cattle compost.

Composting of beef cattle manure using sawdust or recycled compost as a bulking agent was investigated for the management of clopyralid risk, such as changes in the clopyralid concentration and the mechanism of clopyralid accumulation caused by recycled compost. These raw materials were composted with laboratory equipment, which was controlled at 60℃ after the temperature peak by autothermal composting. Clopyralid concentration did not changed during composting in the thermophilic phase; on the contrary, it increased because clopyralid accumulated in compost when recycled compost was used repeatedly as a bulking agent. The clopyralid accumulation ratio (ratio of clopyralid concentration to that in the first compost) could be explained by a model using a recurrence formula, and a correlation existed between the calculated (model) accumulation ratios and measured accumulation ratios (R2  = 0.78). Using this model, the excessive accumulation of clopyralid could be controlled when using recycled compost as a bulking agent with lower moisture content or when part of the recycled compost was replaced by another bulking agent, even if recycled compost had high moisture content. In future work, the model and its considerations should be verified in a field test.

Liquid Chromatographic Determination of Trace Bioavailable Neonicotinoids in Soil with Dispersive Liquid-Liquid Microextraction and Its Application for Experimental Monitoring.

Dispersive liquid-liquid microextraction (DLLME) was applied to extract bioavailable neonicotinoids involved in the uptake from soil through roots to plants. To quantitatively extract bioavailable neonicotinoids with the proposed DLLME, 3.5 mL of dichloromethane (extractant)/acetonitrile (dispersive solvent) (6:1, v/v) was injected into 5 mL of aqueous soil extracts in which 1 g of sodium chloride was previously dissolved. The separated dichloromethane phase after sonication and centrifugation was evaporated, reconstituted with a mobile phase, and determined with high-performance liquid chromatography. The established method showed sufficient analytical performance to quantify the amount remaining in soil in trace amounts. In a pilot trial conducted in the field, the changes in the concentrations of bioavailable neonicotinoids were confirmed using the method. After showing rapid degradation in soil, degradation of clothianidin and imidacloprid slowed after about 100 days of treatment, but it continued to be detected at around 0.02-0.05 µg/g-dried weight until 1097 days. This result suggests that once these neonicotinoids are treated in soil, they might remain for long periods, which supports the possibilities of crop contamination and exposure to pollinators.

Detection of herbicide clopyralid at nanogram per gram level in agricultural products using easy-to-use micro liquid-liquid extraction followed by analysis with ultraperformance liquid chromatography-tandem mass spectrometry.

A new sample preparation method was developed for auxin-like herbicide clopyralid residue in agricultural products. The method uses extraction with sulfuric acid - acidified acetonitrile, with cleanup of sample extracts using solid-phase extraction (diatomaceous earth) and micro liquid-liquid extraction, followed by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). This sample preparation method greatly reduces the influence on ionization during determination with UPLC-MS/MS. Quantification was achieved using external calibrators prepared in matrix-free 0.1% formic acid. The proposed analytical method supported good recovery of 73.7-91.4% with less than 8% relative standard deviation. Method quantification limits (MQL) of samples were 0.6-1.0 ng g-1. The method was applied to determine clopyralid residue in several crop samples. The herbicide was detected as near the MQLs in all samples.

Effects of temperature on the dissipation of total- and water-extractable pesticides in Japanese soils.

We investigated the dissipation of 27 pesticides in five Japanese soils at three temperatures and the variability of activation energies (E a). The dissipation of total pesticides extracted sequentially using water and acetone was fitted to a single first-order (SFO) model. The E a values calculated from the dissipation rate constants of the SFO model showed a normal distribution with a median of 61.1 kJ mol-1. The dissipation of water-extractable pesticides (i.e., phytoavailable pesticides) was fitted to a double first-order in parallel model with two dissipation rate constants: k 1 and k 2. The E a values calculated from k 1 and k 2 showed normal or lognormal distribution, and the medians of the normal distribution calculated from k 1 and k 2 were 62.8 and 45.2 kJ mol-1, respectively. Furthermore, the method for estimating the biphasic dissipation of phytoavailable pesticides at different temperatures by using the median E a values of the laboratory experiment was demonstrated in a field experiment.

Highly sensitive analytical method for herbicide clopyralid residue in cattle manure compost with ultraperformance liquid chromatography tandem mass spectrometry.

A micro liquid-liquid extraction has been applied to sample preparation in the current authorized method for clopyralid in compost. The method rendered matrix effects practically negligible during determination with ultraperformance liquid chromatography-electrospray ionization tandem mass spectrometry with an improved limit of quantification of 0.7 µg/kg dry weight. Moreover, it had good accuracy and reproducibility. Therefore, the method is proposed as a highly effective routine analytical technique for investigating the actual status of clopyralid residue in compost.

Physiological disorder of plants depending on clopyralid concentration in the soil and plant.

The influence of clopyralid in soil on plant growth was investigated over time using three plants. The order of clopyralid sensitivity was as follows: Solanum lycopersicum>Solanum melongena>Momordica charantia, especially physiological disorder of S. lycopersicum were rapidly expressed as various serious symptoms with increasing concentration of clopyralid. In contrast, the clopyralid concentration of above-ground part was in the following order: M. charantia>S. lycopersicum, S. melongena, which differed from the order of sensitivity to clopyralid.

Relationship between growth stage of Brassica rapa var. perviridis and the abilities for uptake and translocation of pesticides in soil.

The relationships between plant growth stage and pesticide-uptake ability were investigated via cultivation of Brassica rapa L. var. perviridis in soil to which was added four pesticides of relatively high log K OW: fenobucarb, procymidone, flutolanil, and tolclofos-methyl. The root concentrations of pesticides were low in very young seedlings with undeveloped root systems, highest in seedlings with developed root systems, and tended to decrease until the usual harvesting stage. Additionally, the shoot concentrations of tested pesticides showed the same trends as the roots. The pesticide-uptake abilities of roots were lowest in very young seedlings and then constant for seedlings until the harvesting stage. In contrast, the pesticide-translocation abilities from root to shoot were constant regardless of growth stage. The results indicated that changes in shoot concentrations with growth stage were affected by the development of the root system and pesticide-uptake ability of roots.

The influence of Brassica rapa var. perviridis growth conditions on the uptake and translocation of pesticides.

We cultivated Brassica rapa var. perviridis in soil mixed with four pesticides (fenobucarb, procymidone, flutolanil, and tolclofos-methyl) at different temperatures, day lengths, and soil water contents. We compared plants' uptake and translocation abilities of the pesticides as affected by growth conditions. The root concentration factor (RCF) of pesticides tended to increase with rising temperature; however, but the influence of temperature on the transpiration stream concentration factor (TSCF) differed for each pesticide. The RCFs and TSCFs of pesticides were high for short days. The soil water content had little or no effect on the uptake and translocation of pesticides. These results showed that it is necessary to consider growth conditions, especially the temperature and day length in plant uptake models for these pesticides.

Comparison of soil sorption parameters of pesticides measured by batch and centrifugation methods using an andosol.

We compared the soil sorption coefficient (K d) measured by batch and centrifugation methods using a Japanese andosol and ten pesticides. Although the K d values measured by both methods increased with time, those obtained via the batch method tended to be higher during the test period. The difference in K d values between the two methods affected pesticide concentrations estimated in the soil solution, and the results estimated using K d values obtained via the batch method underestimated the observed trends.

Differential uptake and translocation of organic chemicals by several plant species from soil.

We performed uptake experiments with 12 different organic chemicals using 16 plant species and determined differences in the ability of plant species to take up and translocate these chemicals. There were differences among the plant species in the shoot and root concentrations of each organic chemical. The root concentration factor values increased with an increasing log of the n-octanol-water partition coefficient (log K OW) of organic chemicals. Thus, the concentrations in roots may be predicted to a certain extent because the root concentration factor values were related to the log K OW. The root-to-shoot translocation was related to the log K OW because the shoot-to-root concentration ratio decreased with an increasing log K OW; however, there was no clear relationship between the shoot concentration factor value and the log K OW, and this differed among plant species.

Source characterization and risk of exposure to atmospheric polychlorinated biphenyls (PCBs) in Ghana.

With recent evidence that persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) are emerging in environmental media in some developing countries that otherwise have sparing production and usage history, it has become important to identify such contemporary source factors of PCBs and the risks this may pose, in line with the global consensus on POP management and elimination. The present study investigated contaminations from atmospheric PCBs in Ghana, deciphered source factors, and accessed risk of exposure to dioxin-like PCBs (DL-PCBs). Atmospheric PCBs were monitored by deployment of PUF-disk passive air samplers (PAS) at several sites across Ghana for 56 days. Atmospheric ∑190PCB concentration in Ghana ranged from 0.28 ng/m3 in Kumasi to 4.64 ng/m3 at Agbogbloshie, a suburb in Accra noted for informal electronic waste (e-waste) recycling activities. As high as 11.10 ng/m3 of PCB concentration was measured in plumes from uncontrolled open burning of e-wastes at Agbogbloshie. Applying statistical source characterization tools, it emerged that e-wastes were a major contributor to the environmental burden of atmospheric PCBs in Ghana. The risk of DL-PCB toxicity via inhalation in the Agbogbloshie area was 4.2 pg TEQ/day, within similar order of magnitude of an estimated risk of 3.85 pg TEQ/day faced by e-waste workers working averagely for 8 h per day. It is suggested that elimination of e-waste sites would help to significantly reduce PCB-related toxicity issues in Ghana. Graphical abstract ᅟ.

Atmospheric monitoring of organochlorine pesticides across some West African countries.

Most African countries have ratified the Stockholm Convention on persistent organic pollutants (POPs) and are expected to reduce emissions of POPs such as organochlorine pesticides (OCPs) to the atmosphere. Emerging evidence, however, suggests that there are contemporary sources of OCPs in African countries despite the global ban on these products. This study investigated the atmospheric contamination from OCPs in four West African countries-Togo, Benin, Nigeria, and Cameroon-to ascertain the emission levels of OCPs and the characteristic signatures of contamination. Polyurethane foam (PUF) disk passive air samplers (PAS) were deployed in each country for ca. 55 days in 2012 and analyzed for 25 OCPs. Hexachlorocyclohexanes (HCHs) and DDTs constituted the highest burden of atmospheric OCPs in the target countries, at average concentrations of 441 pg m-3 (range 23-2718) and 403 pg m-3 (range 91-1880), respectively. Mirex had the lowest concentration, ranged between 0.1 and 3.3 pg m-3. The concentration of OCPs in rainy season was higher than in dry season in Cameroon, and presupposed inputs from agriculture during the rainy season. The concentrations of ∑25 OCPs in each country were in the following order: Cameroon > Nigeria > Benin > Togo. There was significant evidence, based on chemical signatures of the contamination that DDT, aldrin, chlordane, and endosulfan were recently applied at certain sites in the respective countries.

Potential application of immunoassays for simple, rapid and quantitative detections of phytoavailable neonicotinoid insecticides in cropland soils.

This study evaluated the applicability of commercially available kit-based enzyme-linked immunosorbent assay (ELISA) to simple, quick, and quantitative detection for three water-extractable (phytoavailable) neonicotinoid insecticides: dinotefuran, clothianidin, and imidacloprid in soils. ELISA showed excellent analytical sensitivity for determination, but with cross-reaction to structurally related neonicotinoid analogues, which might produce false positives. To analyze insecticides in soil samples of diverse physicochemical properties, they were extracted with water. The aqueous soil extracts were assayed directly with ELISA. No matrix interference was observed without additional dilution with water. Recovery experiments for the insecticides from aqueous soil extracts spiked at 2-10 ng/mL showed good accuracy (72-126%) and precision (<16%). Kit-based ELISAs were used to estimate soil-water distribution coefficients (Kd). Values estimated using this method showed positive correlation between organic carbon contents in soil and those for evaluated insecticides. Results indicate that the evaluated kit-based ELISA has applicability for simple, quick, and reliable detection of phytoavailable insecticides in soils and for estimating Kd values in soil.

Biodegradation of γ-hexachlorocyclohexane by transgenic hairy root cultures of Cucurbita moschata that accumulate recombinant bacterial LinA.

KEY MESSAGE: γ-HCH was successfully degraded using LinA-expressed transgenic hairy root cultures of Cucurbita moschata . Fusing an endoplasmic reticulum-targeting signal peptide to LinA was essential for stable accumulation in the hairy roots. The pesticide γ-hexachlorocyclohexane (γ-HCH) is a persistent organic pollutant (POP) that raises public health and environmental pollution concerns worldwide. Although several isolates of γ-HCH-degrading bacteria are available, inoculating them directly into γ-HCH-contaminated soil is ineffective because of the bacterial survival rate. Cucurbita species incorporate significant amounts of POPs from soils compared with other plant species. Here, we describe a novel bioremediation strategy that combines the bacterial degradation of γ-HCH and the efficient uptake of γ-HCH by Cucurbita species. We produced transgenic hairy root cultures of Cucurbita moschata that expressed recombinant bacterial linA, isolated from the bacterium Sphingobium japonicum UT26. The LinA protein was accumulated stably in the hairy root cultures by fusing an endoplasmic reticulum (ER)-targeting signal peptide to LinA. Then, we demonstrated that the cultures degraded more than 90 % of γ-HCH (1 ppm) overnight and produced the γ-HCH metabolite 1,2,4-trichlorobenzene, indicating that LinA degraded γ-HCH. These results indicate that the gene linA has high potential for phytoremediation of environmental γ-HCH.

Effect of Time-Dependent Sorption on the Dissipation of Water-Extractable Pesticides in Soils.

The dissipation behavior of water-extractable pesticides in soils is important when assessing the phytoavailability of pesticides in soils. This process is less understood than pesticide extraction with organic solvents. To elucidate the dissipation behavior of water-extractable pesticides in soils, we conducted an incubation study using 27 pesticides and five Japanese soils. The rate of decrease of the level of pesticides in water extracts was faster in soils than that of total extracts (water extracts and acetone extracts). This suggests that time-dependent sorption contributed to the difference in the dissipation between the pesticides in water and total extracts from soils. Increased apparent sorption coefficients (Kd,app) with time were positively and significantly correlated with Kd,app values of a 0 day incubation [Kd,app(t0)]. This empirical relationship suggests that Kd,app(t0) values can predict the time-dependent increase in Kd,app and the dissipation of water-extractable pesticides in soils.

Differential uptake and translocation of ß-HCH and dieldrin by several plant species from hydroponic medium.

To compare the uptake and translocation of hydrophobic organic chemicals by plant species, the authors performed uptake experiments with ß-1,2,3,4,5,6-hexachlorocyclohexane (ß-HCH) and 1,2,3,4,10,10-Hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-endo-1,4-exo-5,8-dimethanonaphthalene (dieldrin) using 5 species: Hordeum vulgare, Glycine max, Solanum lycopersicum, Brassica oleracea, and Cucurbita pepo. The present study evaluated uptake ability using root concentration factor (RCF) and translocation ability by transpiration stream concentration factor (TSCF). The RCFs of ß-HCH and dieldrin did not differ remarkably among species, except that the RCF of ß-HCH in B. oleracea was high. The TSCFs of ß-HCH and dieldrin were high in C. pepo, which was not superior in uptake as estimated by RCF. The TSCF of dieldrin in C. pepo was decreased in darkness and was markedly decreased by heating of roots. These results support the hypothesis that transport proteins produced in the root contribute to dieldrin translocation. In contrast, TSCF of ß-HCH was not decreased by these treatments. Therefore, translocation of ß-HCH might not need the contribution of transport proteins. It is possible that C. pepo has a certain function to transport hydrophobic organic chemicals smoothly in root tissues.

Contamination of indoor dust and air by polychlorinated biphenyls and brominated flame retardants and relevance of non-dietary exposure in Vietnamese informal e-waste recycling sites.

This study investigated the occurrence of polychlorinated biphenyls (PCBs), and several additive brominated flame retardants (BFRs) in indoor dust and air from two Vietnamese informal e-waste recycling sites (EWRSs) and an urban site in order to assess the relevance of these media for human exposure. The levels of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), 1,2-bis-(2,4,6-tribromophenoxy)ethane (BTBPE) and decabromodiphenyl ethane (DBDPE) in settled house dust from the EWRSs (130-12,000, 5.4-400, 5.2-620 and 31-1400 ng g(-1), respectively) were significantly higher than in urban house dust but the levels of PCBs (4.8-320 ng g(-1)) were not higher. The levels of PCBs and PBDEs in air at e-waste recycling houses (1000-1800 and 620-720 pg m(-3), respectively), determined using passive sampling, were also higher compared with non-e-waste houses. The composition of BFRs in EWRS samples suggests the influence from high-temperature processes and occurrence of waste materials containing older BFR formulations. Results of daily intake estimation for e-waste recycling workers are in good agreement with the accumulation patterns previously observed in human milk and indicate that dust ingestion contributes a large portion of the PBDE intake (60%-88%), and air inhalation to the low-chlorinated PCB intake (>80% for triCBs) due to their high levels in dust and air, respectively. Further investigation of both indoor dust and air as the exposure media for other e-waste recycling-related contaminants and assessment of health risk associated with exposure to these contaminant mixtures is necessary.

Atmospheric polychlorinated naphthalenes in Ghana.

A nationwide monitoring of atmospheric POPs (persistent organic pollutants) was conducted in Ghana between May and July 2010, applying polyurethane foam (PUF) disk passive air samplers (PAS). Reported here are preliminary findings on PCNs, an industrial organic contaminant currently under review for possible listing under the global chemical treaty. The present results constitute the first set of nationwide data on air PCNs from a West African country. Contrary to expectation, air PCNs levels were quite high in Ghana, at an average of 49 ± 5.4 pg/m(3). The coastal (southern) zone of Ghana appeared the most impacted, with crude open burning of waste, industrial emissions, and the harbor environment identified among possible emission factors. Tri- and tetra-CNs (the lowly chlorinated homologues) predominated in the atmosphere, altogether constituting approximately 90% of total PCN homologues composition. Increased volatilization under tropical conditions was presumed a key factor that contributed to this high atmospheric input of lowly chlorinated homologues. We further observed a significant level of fractionation of PCN homologues across the breadth of the country. The percentage composition of the lowly chlorinated homologues increased northwards, probably because of their transportation in the direction of prevailing winds. From congener profile analysis, PCN-45/36 is proposed as a possible source marker for emissions preempted by uncontrolled waste burning activities. Dioxin-like toxicity of air PCNs in Ghana was estimated to range 0.49-5.6 fg TEQ/m(3). This study brought to the fore the emerging problems of nonagricultural organohalogens that covertly might be confronting the environment in African nations like Ghana.