Residues of Reduced Herbicides Terbuthylazine, Ametryn, and Atrazine and Toxicology to Maize and the Environment through Salicylic Acid.

Terbuthylazine (TBA), ametryn (AME), and atrazine (ATZ) are triazine family herbicides. They are dominantly used in the field of cereal crops like wheat and maize for prevention of upland from annual gramineous and broad-leaved weeds, with attributes of weed efficiency broad spectrum and good market performance. Salicylic acid (SA) is a kind of natural plant growth regulator existing widely in the plant kingdom and participating in many physiological and defense processes. In this study, the effects of SA on the detoxification and degradation of herbicides TBA, AME, and ATZ in maize were investigated. When maize plants were exposed to 6 mg kg-1 of the triazine herbicides, the growth and chlorophyll concentration were reduced, while the membrane permeability increased. After maize was sprayed with 5 mg kg-1 SA, the herbicide-induced phytotoxicity was significantly assuaged, with the increased content of chlorophyll and decreased cellular damage in plants. Activities of several biomarker enzymes such as SOD, POD, and GST were repressed in the presence of SA. The concentration of the triazine herbicides in maize and the soil determined by high-performance liquid chromatography was drastically reduced by spraying SA. Using LC/Q-TOF-MS/MS, six metabolites and nine conjugates of AME in maize and soil were characterized. The relative contents of AME metabolites and conjugates in maize with SA were higher than those without SA. These results suggest that SA is able to promote the detoxification and decay of these triazine herbicides in maize and soil.

[Occurrence and Risk Assessment of Organophosphate Esters in Source Water of the Nanjing Section of the Yangtze River].

We explored the pollution characteristics, spatial and temporal distribution, ecological risk, and human health risk of organophosphate esters (OPEs) in the source water of the Nanjing section of the Yangtze River. Thirteen OPEs were determined by solid phase extraction-high performance liquid chromatography-tandem mass spectrometry. The results showed that twelve OPEs were detected to different extents with total concentrations ranging from 85.21 to 1557.96 ng·L-1[excluding tris (2,3-dibromopropyl) phosphate]. Chloroalkyl phosphate was the main compound and tris(2-chloroethyl) phosphate (TCEP) was the most abundant of the thirteen OPEs, which reached up to 447.08 ng·L-1. Seasonal variation of OPEs showed that the concentrations of OPEs in summer ranged from 220-1557.96 ng·L-1, with the average concentration of 493.78 ng·L-1 being 1.7-2.6 times higher than of that in spring and autumn. An ecological risk assessment showed that tricresyl phosphate and 2-ethylhexyl diphenyl phosphate were associated with moderate or high risks to organisms (algae, crustaceans, and fish). At a high exposure concentration, the total non-carcinogenic risk of OPEs in source water ranged from 4.41×10-3-2.91×10-2, with the highest risk being associated with children aged 0-3 months. The total cancer risk value was 5.88×10-7-3.89×10-6, among which TCEP and Tris(1,3-dichloro-2-propyl) phosphate was associated with a potential risk for children. We conclude that the long-term exposure risk for children of OPEs in the source water of the Nanjing section of the Yangtze River deserve more attention.

[Occurrence Characteristics and Risk Assessment of Antibiotics in Source Water of the Nanjing Reach of the Yangtze River].

Occurrence characteristics of antibiotics in the source water of the Nanjing section of the Yangtze River were analyzed preliminarily by solid-phase extraction and high-performance liquid chromatography-tandem mass spectrometry (SPE-HPLC-MS/MS). The results showed that the cumulative concentration of 16 sampling points ranged from 13.37 ng·L-1 to 780.5 ng·L-1, with an average concentration of 92.95 ng·L-1. Four sulfonamides, three fluoroquinolones, one tetracycline, five macrolides, and one chloramphenicol antibiotic were detected with average concentration ranging from 0.14 ng·L-1 to 49.91 ng·L-1,including enrofloxacin (ERX) and clarithromycin (CLR) with the highest detection rate of 100%, and clindamycin (CLI) with the highest concentration of 739.44 ng·L-1. Overall, the concentration levels of antibiotics in the Nanjing section of the Yangtze River were low compared with other rivers and lakes in China. The risk assessment results showed that the largest cumulative risk of S2 was 0.31, and the environmental risk of sulfamethoxazole (SMX), doxycycline (DOX), and roxithromycin (ROX) had lower risk levels;the health risk indexes of nine antibiotics for different age groups were between 2.22×10-6and 4.86×10-3, while CLI and DOX are the main potential health risk factors for humans.

[Residue dynamics of flubendiamide in paddy field].

Residue dynamics and terminal residue of flubendiamide 19.8% suspension concentrate (SC) in rice and field environment were measured by ultra performance liquid chromatography (UPLC). As flubendiamide and its metabolite were applied at a range of concentrations from 0.05 to 1.0 mg.kg-1, average recoveries of them in soil, water, rice straw, rice grain and rice hull samples ranged from 78.2% to 104.8%, with variation coefficients of 1.1% -4.4%. One-year and three-area results showed that the half-life of gradation for flubendiamide was 9. 8 to 17.3 d in water, 10. 8 to 22.4 d in soil, and 7.6 to 17.3 d in rice plants, respectively. Residues of metabolite NNI-des-iodo in water were detected, but not in soil or rice plants. When flubendiamide was applied at the recommended dose, its residue in rice grain on the 10th day after application was lower than 0.5 mg.kg-1, the maximum residue limit allowed by US for agricultural chemical residues in rice.

[Effects of multiple environmental factors on triflulsulfuron-methyl degradation in soils].

Triflulsulfuron-methyl, a widely used sulfonylurea herbicide, has done harm to the soil and crop. Its environment fate was affected by many factors such as physicochemical or biological factors. In order to understand the effects of different environmental factors on the degradation of triflulsulfuron-methyl in soil, simulated indoor incubation experiments were carried out to explore the effects of soil microbe, soil type, dissolved organic matter (DOM), temperature, and soil moisture on triflulsulfuron-methyl degradation in soils. The results showed that different environmental factors such as temperature, soil moisture, soil microorganisms and soil type influenced triflulsulfuron-methyl degradation in different degrees. The increased soil microbial biomass, soil organic matters and DOM were beneficial to the soil degradation of triflulsulfuron-methyl, meanwhile, the decrease in soil pH could accelerate its degradation in soils. The results showed that soil microorganisms were the main factor effecting the degradation of triflulsulfuron-methyl in soil. Our results provided initial data for the conclusion that a set of biological and physiochemical factors coordinately regulate the decay of triflulsulfuron-methyl in soils.

Impact of dissolved organic matter on bioavailability of chlorotoluron to wheat.

Chlorotoluron (Chl) is a phenylurea herbicide and is widely used for controlling weeds. While it has brought great benefits to crop production, it has also resulted in contamination to ecosystem. In this study, we investigated accumulation of chlorotoluron (Chl) and biological responses of wheat plants as affected by dissolved organic matter (DOM). Wheat seedlings grown under 10 mg kg(-1) Chl for 4 d showed a low level of chlorophyll accumulation and damage to plasma membrane. The growth was inhibited by exposure of chlorotoluron. Treatment with 50 mg DOC kg(-1) DOM derived either from sludge (DOM-SL) or straw (DOM-ST) attenuated the chlorotoluron toxicity to plants. Both DOMs decreased activities of catalase, peroxidase and superoxide dismutase in Chl-treated seedlings. However, an increased glutathione S-transferases activity was observed under the same condition. Wheat plants treated with Chl in the presence of DOM accumulated less Chl than those treated with Chl alone. Moreover, in the presence of DOM, bioconcentration factor (BCF) decreased whereas translocation factors increased. Analyses with FT-IR spectra confirmed the regulatory role of DOMs in reducing Chl accumulation in wheat.

Toxic reactivity of wheat (Triticum aestivum) plants to herbicide isoproturon.

The herbicide isoproturon is widely used for controlling weed/grass in agricultural practice. However, the side effect of isoproturon as contaminants on crops is unknown. In this study, we investigated isoproturon-induced oxidative stress in wheat ( Triticum aestivum). The plants were grown in soils with isoproturon at 0-20 mg/kg and showed negative biological responses. The growth of wheat seedlings with isoproturon was inhibited. Chlorophyll content significantly decreased at the low concentration of isoproturon (2 mg/kg), suggesting that chlorophyll was rather sensitive to isoproturon exposure. The level of thiobarbituric acid reactive substances (TBARS), an indicator of cellular peroxidation, showed an increase, indicating oxidative damage to plants. The isoproturon-induced oxidative stress resulted in a substantial change in activities of the majority of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Activities of the antioxidant enzymes showed a general increase at low isoproturon concentrations and a decrease at high isoproturon concentrations. Activities of CAT in leaves showed progressive suppression under the isoproturon exposure. Analysis of nondenaturing polyacrylamide gel electrophoresis (PAGE) confirmed these results. We also tested the activity of glutathione S-transferase (GST) and observed the activity stimulated by isoproturon at 2-10 mg/kg.

Biological responses of wheat (Triticum aestivum) plants to the herbicide chlorotoluron in soils.

Chlorotoluron is a phenylurea herbicide that is widely used for controlling grass weeds in the land of cereal, cotton and fruit production. However, extensive use of this herbicide may lead to its accumulation in ecosystems, thus inducing the toxicity to crops and vegetables. To assess chlorotoluron-induced toxicity in plants, we performed the experiment focusing on the metabolic adaptation of wheat plants (Triticum aestivum) to the chlorotoluron-induced oxidative stress. The wheat plants were cultured in the soils with chlorotoluron at concentrations of 0-25mg/kg. Chlorotoluron accumulation in plants was positively correlated with the external chlorotoluron concentrations, but negatively with the plant growth. Treatment with chlorotoluron induced the accumulation of O(2)(-) and H(2)O(2) in leaves and resulted in the peroxidation of plasma membrane lipids in the plant. We measured the endogenous proline level and found that it accumulated significantly in chlorotoluron-exposed roots and leaves. To understand the biochemical responses to the herbicide, activities of the antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were assayed. Analysis of SOD activity by non-denaturing polyacrylamide gel electrophoresis (PAGE) revealed that there were three isoforms in the roots and leaves, but the isoforms in the tissues showed different patterns. Also, using the native PAGE, 6 isoforms of root POD and 10 in leaves were detected. The total activity of POD in roots was significantly enhanced. Activities of APX in roots and leaves showed a similar pattern. The CAT activities were generally suppressed under the chlorotoluron exposure.

Effect of dissolved organic matter on the toxicity of chlorotoluron to Triticum aestivum.

Response of two wheat cultivars (Triticum aestivum cv. YM 158 and NM 9) to the herbicide chlorotoluron and the effect of two forms of dissolved organic matter on the chlorotoluron toxicity to the plants were characterized. Treatment with chlorotoluron at 10-50 microg/ml inhibited the seed germination and a dose-response was observed. The inhibition of seed germination was correlated to the depression of alpha-amylase activities. To identify whether chlorotoluron induced oxidative damage to wheat plants, the malondlaldehyde (MDA) content and electrolyte leakage were measured. Results showed that both MDA content and electrolyte leakage in the chlorotoluron-treated roots significantly increased. Activities of several key enzymes were measured that operate in citric acid cycle and carbohydrate metabolic pathway. Inhibited activities of citrate synthase and NADP-isocitrate dehydrogenase were observed in the chlorotoluron-treated roots as compared to control plants. We also examined malate dehydrogenase and phosphoenolpyruvate carboxylase in wheat roots exposed to 30 gg/ml chlorotoluron. However, none of the enzymes showed significant changes in activities. Application of 160 microg/ml dissolved organic matter (DOM) extracted from non-treated sludge (NTS) and heat-expanded sludge (HES) in the medium with 30 microg/ml chlorotoluron induced an additive inhibition of seed germination and plant growth. The inhibition of growth due to the DOM treatment was associated with the depression of activities of alpha-amylase, citrate synthase and NADP-isocitrate dehydrogenase, as well as the increase in malondlaldehyde content and electrolyte leakage. These results suggested that the presence of DOM might enhance the uptake and accumulation of chlorotoluron, and thus resulted in greater toxicity in wheat plants. The two forms of DOM exhibited differences in regulation of chlorotoluron toxicity to the wheat plants. Treatments with DOM-NTS induced greater toxicity to plants as compared to those with DOM-HES. In addition to DOM affecting chlorotoluron-induced toxicity to wheat plants, the cultivars could have also contributed to differences. Generally, NM-9 showed a higher sensitivity to chlorotoluron than YM 158 either in the absence or in the presence of DOM.