Glufosinate and ammonium sulfate inhibit atrazine degradation in adapted soils

The co-application of glufosinate with nitrogen fertilizers may alter atrazine cometabolism, thereby extending the herbicide’s residual weed control in adapted soils. The objective of this study was to assess the effects of glufosinate, ammonium sulfate, and the combination of glufosinate and ammonium sulfate on atrazine mineralization in a Dundee silt loam exhibiting enhanced atrazine degradation. Application of glufosinate at rates of 10 to 40 mg kg⁻¹ soil extended the lag phase 1 to 2 days and reduced the maximum degradation rate by 15% to 30%. However, cumulative atrazine mineralization averaged 85% 21 days after treatment and was independent of treatment. Maximum daily rates of atrazine mineralization were reduced from 41% to 55% by application of 1 to 8 g kg⁻¹ of ammonium sulfate. Similarly, cumulative atrazine mineralization was inversely correlated with ammonium sulfate rates ranging from 1.0 to 8 g kg⁻¹ soil. Under the conditions of this laboratory study, atrazine degradation was relatively insensitive to exogenous mineral nitrogen, in that 8 g (NH₄)₂SO₄ per kilogram soil repressed but did not completely inhibit atrazine mineralization. Moreover, an additive effect on reducing atrazine mineralization was observed when glufosinate was co-applied with ammonium sulfate. In addition, ammonium fertilization alters the partitioning of ¹⁴C-atrazine metabolite accumulation and nonextractable residues, indicating that ammonium represses cleavage of the triazine ring. Consequently, results indicate that the co-application of glufosinate with N may increase atrazine persistence under field conditions thereby extending atrazine residual weed control in adapted soils.     

几种吸附剂对阿特拉津的吸附及其 Zeta 电位特性研究

通过振荡吸附平衡试验,研究了蒙脱石、凹凸棒石、竹炭、木炭对阿特拉津的吸附行为,讨论了pH值、离子强度对吸附的影响,并考察了吸附剂表面的Zeta电位变化。结果表明,几种吸附剂对阿特拉津的吸附均符合Freundlich方程;竹炭、木炭的吸附能力明显高于蒙脱石和凹凸棒石。吸附剂对阿特拉津的吸附量随着悬液离子强度的增加而增加,在悬液pH一定(pH=6),离子强度为10-3mol/L NaNO3时,蒙脱石、凹凸棒石对阿特拉津的吸附量分别为538.30、609.68 mg/kg,当离子强度增加为10-2mol/L时,吸附量分别增至611.26、731.63 mg/kg;当离子强度由10-3增至10-1mol/L NaNO3时,竹炭、木炭对阿特拉津的吸附量有较多增加。当悬液pH在3~8范围时,几种吸附剂表面均带负电荷,其Zeta电位值随着pH的增加而增加,随离子强度的增加而减小。悬液离子强度一定时,随着pH的增加,吸附阿特拉津后吸附剂表面Zeta电位变化不显著。研究结果有助于从机理上解析吸附剂对有机污染物的吸附行为。     

Microbial biomass and C mineralization in agricultural soils as affected by atrazine addition

This study examines the effects of atrazine on both microbial biomass C and C mineralization dynamics in two contrasting agricultural soils (organic C, texture, and atrazine application history) located at Galicia (NW Spain). Atrazine was added to soils, a Humic Cambisol (H) and a Gleyic Cambisol (G), at a recommended agronomic dose and C mineralization (CO₂ evolved), and microbial biomass measurements were made in non-treated and atrazine-treated samples at different time intervals during a 12-week aerobic incubation. The cumulative curves of CO₂–C evolved over time fit the simple first-order kinetic model [Ct = Co (1 − e ^−kt )], whose kinetic parameters were quantified. Differences in these parameters were observed between the two soils studied; the G soil, with a higher content in organic matter and microbial biomass C and lower atrazine application history, exhibited higher values of the total C mineralization and the potentially mineralizable labile C pool than those for the H soil. The addition of atrazine modified the kinetic parameters and increased notably the C mineralized; by the end of the incubation the cumulative CO₂–C values were 33–41% higher than those in the corresponding non-added soils. In contrast, a variable effect or even no effect was observed on the soil microbial biomass following atrazine addition. The data clearly showed that atrazine application at normal agricultural rates may have important implications in the C cycling of these two contrasting acid soils.     

竹炭固定化微生物对土壤中阿特拉津的降解研究

采用环境友好材料竹炭为主要载体,壳聚糖和海藻酸钠为辅助载体,固定从污泥中分离出的阿特拉津降解菌株,研究不同固定材料对降解菌生长的影响,以及固定化微生物对土壤中阿特拉津的降解效果.结果表明,竹炭对阿特拉津降解菌具有较强的吸附固定能力,且竹炭粒径越小,固定化效果越好.利用壳聚糖和海藻酸钠交联并加固阿特拉津降解菌,增大了固定化空间,显著增加了降解菌的生物量,并提高了阿特拉津的降解效率.1％壳聚糖+5％海藻酸钠+竹炭+降解菌颗粒对阿特拉津降解菌的固定化效果最佳,施用该微生物固定化颗粒28天后,砂姜黑土及红壤中阿特拉津残留率分别为48.07％和47.23％.     

How increasing availabilities of carbon and nitrogen affect atrazine behaviour in soils

 The effect of increasing amounts of glucose and mineral N on the behaviour of atrazine was studied in two soils. One had been exposed to atrazine under field conditions (adapted soil), the other had not (non-adapted soil), resulting, respectively, in an accelerated degradation of atrazine in the adapted soil and in a slow degradation of the herbicide in the non-adapted soil. The dissipation of ¹⁴C-atrazine via degradation and formation of non-extractable "bound" residues was followed during laboratory incubations in soils supplemented or not with increasing amounts of glucose and mineral N. In both soils, glucose added at rates of up to 16 g C kg^–1 soil did not modify atrazine mineralization but increased the formation of bound residues; this was probably due to the retention of atrazine by the growing microbial biomass. Atrazine dealkylation was enhanced when a large amount of glucose was added. In both soils, the addition of the largest dose of mineral N (2.5 g N kg^–1 soil) decreased atrazine mineralization. The simultaneous addition of glucose and mineral N enhanced their effects. When the largest doses of mineral N and glucose were added, atrazine mineralization stopped in both soils, and the proportion of bound residues increased. Glucose and mineral N additions influenced atrazine mineralization to a greater extent in the adapted soil than in the non-adapted one, as revealed by ANOVA, although glucose addition had a greater effect than N. The competition for space and nutrients between atrazine-degrading microorganisms and the total heterotrophic microflora probably contributed to the decrease in atrazine mineralization. Received: 9 June 1998     

Impact of grass filter strips length on exported dissolved masses of metolachlor,atrazine and deethylatrazine: a four‐season study under natural rain conditions

Herbicides atrazine and metolachlor have been detected in water bodies across the world. The objective of this study was to assess the efficiency of 0‐m, 3‐m, 6‐m and 9‐m grass filter strips to reduce masses of dissolved metolachlor, atrazine and deethylatrazine (a degradation product of atrazine) exported in runoff. For that purpose, 16 uncultivated plots (3‐m wide × 65‐m long) with 0‐m‐, 3‐m‐, 6‐m‐ and 9‐m‐long grass filter strips were setup in a completely randomized block design. During four seasons, masses of dissolved atrazine, metolachlor and deethylatrazine were determined for the first four to five rain events, under natural rain conditions, after atrazine and metolachlor application. Generally, grass filter strips reduced exported herbicide masses by more than 90% and influenced atrazine and metolachlor dissipation kinetics in the field. The 3‐m grass filter strip (area ratio source/strip of 22:1) usually provided a reduction in exported herbicide masses similar to the 6‐ or 9‐m grass filter strips. Therefore, under the present experimental soil and climate conditions, a grass filter strip of 3 m would be a good compromise between environmental protection of surface waters against atrazine and metolachlor contamination and conservation of agricultural land use. Such an approach contributes to the acceptability by producers to implement optimized best management practices such as vegetated filter strips for the preservation of the quality of water resources.     

Microbial mineralization of atrazine and 2,4-dichlorophenoxyacetic acid in riparian pasture and forest soils

Microbial biomass and mineralization of atrazine [2-chloro-4(ethylamino)-6(isopropylamino)s-triazine] and 2,4-D (2,4-dichlorphenoxyacetic acid) were examined in the top 10 cm of riparian pasture soils and in the litter layer and top 10 cm of mineral soils of riparian forest ecosystems. The riparian forest litter had higher levels of active and total fungal biomass than forest or pasture mineral soils in winter, spring, and fall. Active bacterial biomass was higher in forest litter than in forest and pasture mineral soils in spring and autumn, and higher in forest mineral soils than in pasture soils in summer. Total bacterial biomass was higher in forest mineral soils than in pasture soils during all seasons. In spring, it was also higher in forest litter than in pasture soils. Atrazie and 2,4-D mineralization in pasture soils was exceeded by that in forest litter in spring and autumn and by that in forest mineral soils in summer and autumn. There was no correlation between either active or total fungal and bacterial biomass with pesticide degradation.     

Influence of nitrogen on atrazine and 2, 4 dichlorophenoxyacetic acid mineralization in blackwater and redwater forested wetland soils

 Microcosms were used to determine the influence of N additions on active bacterial and fungal biomass, atrazine and dichlorophenoxyacetic acid (2,4-D) mineralization at 5, 10 and 15 weeks in soils from blackwater and redwater wetland forest ecosystems in the northern Florida Panhandle. Active bacterial and fungal biomass was determined by staining techniques combined with direct microscopy. Atrazine and 2,4-D mineralization were measured radiometrically. Treatments were: soil type, (blackwater or redwater forested wetland soils) and N additions (soils amended with the equivalent of 0, 200 or 400 kg N ha^–1 as NH₄NO₃). Redwater soils contained higher concentrations of C, total N, P, K, Ca, Mn, Fe, B and Zn than blackwater soils. After N addition and 15 weeks of incubation, active bacterial biomass in redwater soils was lower when N was added. Active bacterial biomass in blackwater soils was lower when 400 kg N ha^–1, but not when 200 kg N ha^–1, was added. Active fungal biomass in blackwater soils was higher when 400 kg N ha^–1, but not when 200 kg N ha^–1, was added. Active fungal biomass in redwater soils was lower when 200 kg N ha^–1, but not when 400 kg N ha^–1, was added. After 15 weeks of incubation 2,4-D degradation was higher in redwater wetland soils than in blackwater soils. After 10 and 15 weeks of incubation the addition of 200 or 400 kg N ha^–1 decreased both atrazine and 2,4-D degradation in redwater soils. The addition of 400 kg N ha^–1 decreased 2,4-D degradation but not atrazine degradation in blackwater soils after 10 and 15 weeks of incubation. High concentrations of N in surface runoff and groundwater resulting from agricultural operations may have resulted in the accumulation of N in many wetland soils. Large amounts of N accumulating in wetlands may decrease mineralization of toxic agricultural pesticides. Received: 26 June 1998     

The influence of nitrogen on atrazine and 2,4-dichlorophenoxyacetic acid mineralization in grassland soils

The influence of fertilizer N on the mineralization of atrazine [2-chloro-4(ethylamino)-6(isopropylamino)-s-triazine] and 2,4-D (2,4-dichlorophenoxyacetic acid) in soils was assessed in microcosms using radiometric techniques. N equivalent to 0, 250, and 500 kg N as NH₄NO₃ ha^-1 was added to three grassland soils. Compared to the control, the 250- and 500-kg treatments suppressed mineralization of atrazine by 75 and 54%, respectively, and inhibited mineralization of 2,4-D by 89 and 30%, respectively. Active fungal biomass responded to the N treatments in an opposite manner to herbicide mineralization. Compared to the control, the 250- and 500-kg treatments increased the active fungal biomass by more than 300 and 30%, respectively. These results agree with other observations that N can suppress the decomposition of resistant compounds but stimulate the primary growth of fungi. The degree of suppression was not related to the amount of N added nor to the inherent soil N levels before treatment. The interaction between the N additions and the active fungal biomass in affecting herbicide mineralization suggests that N may alter microbial processes and their use of C sources and thus influence rates of herbicide degradation in the field.     

草萘胺在五种土壤及其胶体上的吸附行为

土壤胶体是土壤中颗粒最细小的部分,由于具有巨大的比表面积和较高的吸附容量,是环境中污染物的重要吸附剂,直接影响到污染物的归趋和生物有效性.本文采用批次吸附试验的方法,研究了农药草萘胺在黄棕壤等5种土壤及土壤胶体上的吸附行为.结果表明,草萘胺在供试土壤及胶体上的吸附均能很好地符合Freundlich方程;与本体土壤相比,...     

Volatilization of trifluralin,atrazine, metolachlor,chlorpyrifos, alpha-endosulfan,and beta-endosulfan from freshly tilled soil

The volatile and soil loss profiles of six agricultural pesticides were measured for 20 days following treatment to freshly tilled soil at the Beltsville Agricultural Research Center. The volatile fluxes were determined using the Theoretical Profile Shape (TPS) method. Polyurethane foam plugs were used to collect the gas-phase levels of the pesticides at the TPS-defined critical height above a treated field. Surface-soil (0-8 cm) samples were collected on each day of air sampling. The order of the volatile flux losses was trifluralin > alpha-endosulfan > chlorpyrifos > metolachlor > atrazine > beta-endosulfan. The magnitude of the losses ranged from 14.1% of nominal applied amounts of trifluralin to 2.5% of beta-endosulfan. The daily loss profiles were typical of those observed by others for volatile flux of pesticides from moist soil. Even though heavy rains occurred from the first to third day after treatment, the majority of the losses took place within 4 days of treatment, that is, 59% of the total applied atrazine and metolachlor and >78% of the other pesticides. Soil losses generally followed pseudo-first-order kinetics; however, leaching due to heavy rainfall caused significant errors in these results. The portion of soil losses that were accounted for by the volatile fluxes was ordered as follows: alpha-endosulfan, 34.5%; trifluralin, 26.5%; chlorpyrifos, 23.3%; beta-endosulfan, 14.5%; metolachlor, 12.4%; and atrazine, 7.5%.     

Degradability of atrazine, cyanazine, and dicamba in methanogenic enrichment culture microcosms using sediment from the Pearl River of Southern China

Degradation of three herbicides, atrazine, cyanazine and dicamba, was assessed in laboratory microcosms incubated under simulated methanogenic conditions using sediment from Pearl River of Southern China as an inoculum. Atrazine was much more resistant to degradation than cyanazine and dicamba over 300 days of incubation. Biodegradation of cyanazine and dicamba was further substantiated by establishment of enrichment transfer cultures in which the degradation of the respective herbicide was accelerated by the active microorganisms. Degradation of cyanazine initially involved the removal of chlorine and the two side chains, while that of dicamba was O-demethylation reaction forming 3,6-dichlorosalicyclic acid. Results suggest that biodegradation of xenobiotics can be established through enrichment culture transfer technique, and further mechanism of degradation and microorganisms involved can be elucidated.     

胶体存在时不同质地土壤对锌镉的吸附试验研究

以重金属离子Zn和Cd及胶体为对象,通过等温静态批量平衡吸附试验,分析了3种不同质地土壤对Zn、Cd单一吸附和等量竞争吸附特征,胶体对土壤吸附Zn、Cd的影响,并用Langmuir和Freundlich方程对试验结果进行了拟合。结果表明,随着平衡液中Zn2+、Cd2+浓度的增加,土壤对Zn、Cd的吸附量逐渐增大;3种质地土壤对Zn、Cd吸附量顺序为砂壤>粉壤>壤砂土;Zn2+、Cd2+共存时,土壤对这两种离子的吸附量比单一离子存在的情况下明显下降;胶体存在时抑制了土壤对Zn的吸附,促进了土壤对Cd的吸附;就本试验来说,Freundlich方程拟合效果优于Langmuir方程。     

Effects of repeated metolachlor applications on its persistence in field soil and degradation kinetics in mixed microbial cultures

 The persistence of metolachlor, a soil-applied herbicide, was studied under field conditions involving repeated herbicide applications. The test field received four applications of metolachlor over an 8-month period, which included two cropping seasons. There was a trend for more rapid rates of degradation with increasing numbers of previous treatments, with fifty percent dissipation time (DT₅₀) of metolachlor declining from 18 days in the first spray to 2.5 days in the fourth spray. An effort was made to isolate the microbial population which had become acclimated to the herbicide from this field soil. A fungal community isolated from this soil showed the capacity to degrade up to 99.6% of the metolachlor within a span of 20 days. The bacterial community isolated could also degrade up to 81.5% of the metolachlor. Hence, this study clearly indicated that repeated applications of metolachlor to soil resulted in the generation of an adapted microbial population with an enhanced ability to degrade the applied herbicide. Received: 13 November 1998     

Influence of rainfall distribution on simulations of atrazine, metolachlor, and isoxaflutole/metabolite transport in subsurface drained fields

This research investigated the impact of modeling atrazine, metolachlor, and isoxaflutole/metabolite transport in artificially subsurface drained sites with temporally discrete rainfall data. Differences in considering rainfall distribution are unknown in regard to estimating agrochemical fluxes in the subsurface. The Root Zone Water Quality Model (RZWQM) simulated pesticide fate and transport at three subsurface drained sites: metolachlor/atrazine field experiment in Baton Rouge, LA (1987), and two isoxaflutole/metabolite field experiments in Allen County and Owen County, Indiana (2000). The modeling assumed linear, equilibrium sorption based on average reported physicochemical and environmental fate properties. Assumed rainfall intensity and duration influenced transport by runoff more than transport by subsurface drainage. As the importance of macropore flow increased, the necessity for using temporally discrete rainfall data became more critical. Long-term simulations indicated no significant difference between average or upper percentile (i.e., <2% difference in percent loss as a function of mass applied) atrazine, metolachlor, or isoxaflutole/metabolite loss through subsurface drainage among the three different rainfall assumptions. It was necessary (i.e., within 7% of predicted loss) to use hourly or average duration storm events as opposed to daily rainfall data for total (i.e., runoff and subsurface drainage) pesticide loss over the long term.     

Predicting plant sulfur deficiency in soils: results from Ohio

We developed a model for plant available sulfur (S) in Ohio soils to predict potential crop plant S deficiency. The model includes inputs of plant available S due to atmospheric deposition and mineralization of soil organic S and output due to leaching. A leaching index was computed using data on annual precipitation; soil pH and clay content that influence sulfate adsorption; and pore water velocity based upon percent sand, silt, and clay. There are five categories of S status ranging from highly deficient to highly sufficient, and the categories are defined based on whether the crop S requirement was 15 or 30kg S ha⁻¹ year⁻¹. The final database derived from the model includes 1,473 soil samples representing 443 of the 475 soil series in Ohio. For a crop requiring 15kg S ha⁻¹ year⁻¹, most soils (68.6%) were classified as variably deficient, which implies that the response to S fertilization will be variable but often positive depending on specific crop conditions. For a crop requiring 30kg S ha⁻¹ year⁻¹, 43.2% of soils were classified as variably deficient, but 49.7% were classified as moderately or highly deficient, implying that a response to S fertilization will usually or always occur. The model predicts crop S status for a single state in the USA, but with proper inputs, it should be applicable to other areas.     

木屑生物质炭对水中阿特拉津、多菌灵和啶虫脒复合农药的吸附性能研究

选取木屑为原材料,在500、700℃下制备生物质炭(标记为MX500和MX700),试验考察了溶液初始pH和生物质炭投加量对其吸附性能的影响,并利用吸附动力学、吸附等温线以及傅里叶变换红外光谱(FTIR)等手段,研究了木屑生物质炭对水溶液中3种不同类型的典型常用农药阿特拉津(ATR)、多菌灵(CAR)和啶虫脒(ACE)的吸附特性及吸附机理。结果表明：热解温度700℃,pH 3.0,生物质炭投加量为2.0 g/L时,木屑生物质炭对3种农药的联合吸附效果最好。MX700对ATR、CAR和ACE的最大吸附量分别为40.2、50.4和44.9μg/g,约为MX500的1.4倍～2.2倍。吸附动力学和吸附等温线结果显示,准二级动力学方程、颗粒内扩散方程和Langmuir方程能较好地拟合吸附过程。FTIR结果显示,木屑生物质炭主要通过酚羟基和羧基等含氧官能团以及芳香环结构去除水中ATR、CAR和ACE。木屑生物质炭对农药的吸附机理包括静电作用力、氢键作用力及π–π键相互作用力。在100μg/L浓度下,木屑生物质炭对ATR、CAR和ACE复合农药的吸附效果和机理与农药单体类似。综上,木屑生物质炭作为...     

汞在山东省三种森林土壤上的吸附解吸特征研究

As one of the most toxic heavy metals with persistence, bioaccumulation, and toxicity in environment, mercury and its envi- ronmental problems have caused a global concern. To fully understand the behavior and fate of mercury (Hg)(Ⅱ) in forest soils, a series of batch experiments were conducted to determine the adsorption and desorption characteristics of Hg(Ⅱ) by three dark brown forest soils from Mount Taishan, Laoshan Mountain, and Fanggan Village in Shandong Province, China. The adsorption solution was prepared using 0.1 mol L-1 NaNO3 as background electrolyte, with Hg(Ⅱ) at rising concentration gradients of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 mg L-1 . Fourier transform infrared (FTIR) spectroscopy was adopted to characterize the soil samples and soil-Hg complexes. It was found that Hg(Ⅱ) adsorption isotherms could be well fitted with both Langmuir and Freundlich equations. The soil from Mount Taishan had the largest potential Hg(Ⅱ) adsorption capacity, though with less adsorptive intensity. The percentages of Hg(Ⅱ) desorbed from all soil samples were less than 0.6%, which suggested that all the soils studied had a high binding strength for Hg(Ⅱ). The soil from Mount Taishan had a higher Hg(Ⅱ) desorption capacity than the other soils, which indicated that the Hg(Ⅱ) deposited on the topsoil of Mount Taishan from atmosphere may easily discharge to surface water through runoff. Results of the FTIR spectroscopy showed that the three soils contained the same functional groups. The relative absorbencies of soil-Hg complexes changed significantly compared with those of the soil samples and the adsorption of Hg(Ⅱ) mainly acted on the O-H, C-O, and C=O groups of the soils.     

Influence of microbial inoculation (Pseudomonas sp. strain ADP), the enzyme atrazine chlorohydrolase,and vegetation on the degradation of atrazine and metolachlor in soil

The concentrations of atrazine in the freshly added soils and the soils that had been incubated for 50 days significantly decreased 1 day after the addition of the enzyme atrazine chlorohydrolase or the soil bacterium Pseudomonas sp. strain ADP as compared with those in the uninoculated soils. Atrazine chlorohydrolase or ADP had no effect on the degradation of metolachlor. The half-lives of atrazine in the freshly added soils and in the aged soils after the treatment with atrazine chlorohydrolase or ADP markedly decreased as compared with those in the uninoculated soils. The half-lives of metolachlor in the aged soils were much longer than those of freshly added metolachlor. The percentage atrazine degraded in the freshly treated soils was much higher than that in the aged soils. This indicates that aging significantly decreased the bioavailability of atrazine. Vegetation significantly decreased the concentration of metolachlor. However, vegetation showed no effect on the degradation of atrazine.     

Simultaneous determination of alachlor, metolachlor, atrazine, and simazine in water and soil by isotope dilution gas chromatography/mass spectrometry

A multiresidue method was developed for the simultaneous determination of low parts per billion (ppb) concentrations of the herbicides alachlor, metolachlor, atrazine, and simazine in water and soil using isotope dilution gas chromatography/mass spectrometry (GC/MS). Known amounts of 15N,13C-alachlor and 2H5-atrazine were added to each sample as internal standards. The samples were then prepared by a solid phase extraction with no further cleanup. A high resolution GC/low resolution MS system with data acquisition in selected ion monitoring mode was used to quantitate herbicides in the extract. The limit of detection was 0.05 ppb for water and 0.5 ppb for soil. Accuracy greater than 80% and precision better than 4% was demonstrated with spiked samples.