好氧土壤中[C环-U-14C] 丙酯草醚的结合残留及其在腐殖质中的分布动态

农药的环境行为与归趋,尤其是结合残留研究,是新农药安全性评价的重要内容之一,这关系到新农药的科学使用。本文利用14C同位素示踪技术,研究了[C环-U-14C]丙酯草醚(ZJ0273)在3种不同类型好氧土壤中的结合残留及其在富啡酸、胡敏酸和胡敏素中的动态分布。结果表明：（1）在整个培养过程中,土壤中的丙酯草醚结合残留量均随时间而递增。培养至75d,红砂土（S1）、黄松土（S2）与淡涂泥田（S3）中的14C-BR最大值分别为引入量的12.55%,20.35%和20.49%,且富含有机质和pH较高的土壤更易与丙酯草醚形成结合残留;（2）丙酯草醚与富啡酸、胡敏酸和胡敏素形成的结合残留,含量大小依次为富啡酸＞胡敏素＞胡敏酸。因此,丙酯草醚与土壤基质形成结合残留的过程中,富啡酸起主要作用,而胡敏酸的作用最小。     

Degradation of [carboxyl-14C] 2,4-D and [ring-U-14C] 2,4-D in 114 agricultural soils as affected by soil organic carbon content

This study compared the degradation of [carboxyl-¹⁴C] 2,4-dichlorophenoxyacetic acid (2,4-D) (C2,4-D) and [ring-U-¹⁴C] 2,4-D (R2,4-D) in 114 agricultural soils (0–15 cm) as affected by 2,4-D sorption and soil properties (organic carbon content, pH, clay content, carbonate content, cation exchange capacity, total microbial activity). The sample area was confined to Alberta, Canada, located 49–60° north longitude and 110–120° west latitude and soils were grouped by soil organic carbon content (SOC) (0–0.99%, 1–1.99%, 2–2.99%, 3–3.99% and >4% SOC). Degradation rates of C2,4-D and R2,4-D followed first-order kinetics in all soils. Although total microbial activity increased with increasing SOC, degradation rates and total degradation of C2,4-D and R2,4-D decreased with increasing SOC because of increased sorption of 2,4-D by soil and reduced bioavailability of 2,4-D and its metabolites. Rates of R2,4-D degradation were more limited by sorption than rates of C2,4-D degradation, possibly because of greater sorption and formation of bound residues of 2,4-D metabolites relative to the 2,4-D parent molecule. Based on the sorption and degradation parameters quantified, there were two distinct groups of soils, those with less than 1% SOC and those with greater than 1% SOC. Specifically, soils with less than 1% SOC had, on average, 2.4 times smaller soil organic carbon sorption coefficients and 1.4 times smaller 2,4-D half-lives than soils with more than 1% SOC. In regional scale model simulations of pesticide leaching to groundwater, covering many soils, input parameters for each pesticide include a single soil organic carbon sorption coefficient and single half-life value. Our results imply, however, that the approach to these regional scale assessments could be improved by adjusting the values of these two input parameters according to SOC. Specifically, this study indicates that for 2,4-D and Alberta soils containing less than 1% SOC, the 2,4-D pesticide parameters obtained from generic databases should be divided by 2.5 (soil organic carbon sorption coefficient) and 1.5 (half-life value).     

Formation of [14C]cellulase-humic complexes and their stability in soil

[¹⁴C]cellulase was extracted from the culture medium of Trichoderma viride and an attempt made to complex it with humic acid by adsorption. The results showed that the humic acid extracted from soil does not form a stable complex with [¹⁴C]cellulase. In contrast, the flocculation of humic acid by 24 mM Ca²⁺ in the presence of the cellulase resulted in the formation of stable humic-cellulase complexes. These complexes showed great resistance to proteolysis and storage at high temperatures. DEAE cellulose chromatography of cellulase-humic complexes revealed that cellulase could not be separated from the humic acid. Enzyme activity was only eluted along with humic acid upon increasing gradient concentration from 1.0 to 1.5 m NaCl. Furthermore, in order to test their stability, the enzyme-humic complexes were incorporated into fresh soil for 90 days. The cellulase-humic complexes were then extracted from soil. Fractionation of the extract on DEAE cellulose and G 100 Sephadex revealed that cellulase activiiy could not be separated from humic acid and was again eluted in the form of enzyme-humic complexes. This confirmed the stability of cellulase-humic complexes in soil.     

Pyrolysis of [14C]-chlorantraniliprole in tobacco

The pyrolysis of [(14)C]-chlorantraniliprole {3-bromo-1-(3-chloro-2-pyridinal)-N-[4-chloro-2-methyl-6-[(methylamino)carbonyl]phenyl]-1H-pyrazole-5-carboxamide} in tobacco was examined. Typically five commercially available cigarettes were treated separately with either [pyrazole carbonyl-(14)C] or [benzamide carbonyl-(14)C]-chlorantraniliprole at a concentration of 20 ppm (μg chlorantraniliprole equivalent/g cigarette weight; main study) to 40 ppm (for degradate identification only). All treated cigarettes were smoked using an apparatus designed to collect mainstream (MS) and sidestream (SS) smoke through a glass fiber filter and a series of liquid traps. The material balance for recovery of applied radiolabel ranged from 92.4 to 94.9%. Unchanged chlorantraniliprole was the major component found in butt and filter extracts, averaging a total of 17.4-17.9% of the applied radioactivity. A nonpolar degradation product, 2-[3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazol-5-yl]-6-chloro-3,8-dimethyl-4(3H)-quinazolinone, designated 1, represented an average of 10.1-15.9% of the applied radioactivity in the [pyrazole carbonyl-(14)C] or [benzamide carbonyl-(14)C]-chlorantraniliprole cigarettes, respectively. (14)CO(2) was the major degradate, representing an average of 32.9 and 25.1% of the applied radioactivity in pyrazole and benzamide experiments, respectively. In the pyrazole carbonyl label a polar degradate, 5-bromo-N-methyl-1H-pyrazole-3-carboxamide (2) was present in the filter extracts at an average of 9.5% of the applied radioactivity. The most nonpolar degradate, 2,6-dichloro-4-methyl-11H-pyrido[2,1b]quinazolin-11-one (3), was present in [benzamide carbonyl-(14)C]-treated cigarettes only and represented an average of 14.7% of the applied radioactivity.     

Biogeochemical factors related with organic matter degradation and C storage in agricultural volcanic ash soils

Laboratory incubation experiments in addition to physicochemical analyses of volcanic ash soils were carried out in order to identify biogeochemical factors related with soil organic C (SOC) stabilization in the long term and with the potential for C sequestration of agroecosystems. Up to 24 vineyard plots under similar subtropical conditions in Tenerife Island (Spain) were sampled. Soil samples were incubated for 30 days in laboratory conditions (27 °C and 66% water holding capacity) and the CO₂ released was periodically measured to plot C mineralization curves. Soil organic matter (SOM) with special emphasis paid on the humic acid (HA) was characterized by elemental composition, spectroscopic techniques: visible, infrared (IR) and ¹³C nuclear magnetic resonance (¹³C NMR) and analytical pyrolysis–gas chromatography/mass spectrometry (GC/MS). The dependent variables examined were either the total mineralization coefficient (TMC, g C · kg C soil^?1 day^?1) in laboratory incubations, or the SOC. A very significant negative correlation was found between SOC and TMC, i.e., in our soils, the higher the biodegradation rates under laboratory conditions, the lower the soil C sequestered in the corresponding plots. In it was also observed that the concentration of amorphous minerals (Al_o + ½ Fe_o index) and the water holding capacity at 0.033 MPa were associated with lower CO₂ release; the latter could suggest microanaerobic conditions hampering biodegradation in these thixotropic soils. Conversely, no correlation was found between SOC or TMC and typical soil physical and chemical factors, such as granulometric fractions or exchangeable calcium. The molecular characteristics of the HAs showed also predictive potential as regards SOC resilience, reflecting the comparatively fast biodegradation of SOM composed mainly of biomass constituents (prominent lignin signature and O-alkyl ¹³C NMR region). The poor correlation between total aromaticity of the HAs and SOM resistance against biodegradation could be explained by a dual origin of aromatic structures in HAs, either consisting of methoxyl-containing non-decomposed lignin structures or condensed black carbon-like polyaromatic structures. The results suggested the possibility of predicting the vulnerability of SOC to biodegradation from laboratory incubation experiments, which results of interest for modeling global change scenarios.     

Formation and degradation of ethylene in submerged rice soils

Ethylene formation in submerged soils and ethylene degradation by rice roots and soils were investigated. Ethylene was formed in rice soils in amounts which may deleteriously affect the growth of rice seedlings. Ethylene formation was markedly enhanced when organic materials such as glucose or rice straw were added to the soil. The rice roots, especially those taken from lowland and rice fields, showed notable ethylene-degradation activity; the rhizosphere microorganisms of the lowland rice appeared to be responsible for the ethylene-degradation activity. Lowland soils which have been continually submerged for a long time also showed ethylene-degradation activity. Upland soil and soil recently submerged, however, showed little degradation activity.     

Permethrin and its two metabolite residues in seven agricultural crops

Metabolite residues of permethrin are not reported in the literature for most agricultural crops. This paper reports residues of permethrin and its 2 metabolites (dichlorovinyl acid and metaphenoxybenzyl alcohol) in 7 different agricultural crops (Chinese cabbage, spinach, asparagus, raspberries, green peas, turnip roots, and turnip greens). Permethrin residues declined approximately 85% within 7 days after treatment in all crops. In most cases, the acid metabolite residues peaked at 3 days, and declined after that. Translocation of residues into turnip roots was very slight; the average was less than 0.05 ppm for permethrin and alcohol metabolite residues and none was detected for the acid metabolite residue. Permethrin residues in the turnip greens averaged approximately 2 ppm for the 0.112 kg ai/ha treatment, and 6 ppm for the 0.224 kg ai/ha treatment.     

Decomposition of 14C glucose in two soils with different amounts of heavy metal contamination

A high metal-containing soil and a low metal-containing soil were supplied with ¹⁴C-labelled glucose at two rates, one to provide a constant glucose-to-soil ratio and the other a constant glucose-to-biomass ratio. The aim was to assess the effects of these different ratios on the microbial substrate utilisation efficiency. Glucose was added with or without N to investigate the extraction efficiency of the fumigation-extraction method shortly after substrate addition. The addition of glucose without N resulted in a proportionally larger increase in microbial biomass C than in microbial ninhydrin-reactive N (E_NIN) within the first few days after substrate addition, due to N deficiency. The biomass C-to-E_NIN ratio remained constant in all soil treatments after glucose addition in combination with N, indicating that the extraction efficiency of the fumigation-extraction method is not affected by the addition of glucose. Lower percentages of glucose added were incorporated into the microbial biomass with an increasing ratio of glucose-to-biomass. The ratio of respired to biomass incorporated ¹⁴C increased in all high metal-containing soil treatments markedly above that of the low metal-containing soil from day two of the incubation, markedly overriding the effects on the glucose C-to-biomass C ratio. Our results clearly demonstrated that more substrate was diverted by microorganisms into catabolic at the expense of anabolic processes in a high metal-containing soil.     

pH regulation of carbon and nitrogen dynamics in two agricultural soils

Soil pH is often hypothesized to be a major factor regulating organic matter turnover and inorganic nitrogen production in agricultural soils. The aim of this study was to critically test the relationship between soil pH and rates of C and N cycling, and dissolved organic nitrogen (DON), in two long-term field experiments in which pH had been manipulated (Rothamsted silty clay loam, pH 3.5-6.8; Woburn sandy loam, pH 3.4-6.3). While alteration of pH for 37 years significantly affected crop production, it had no significant effect on total soil C and N or indigenous mineral N levels. This implies that at steady state, increased organic matter inputs to the soil are balanced by increased outputs of CO₂. This is supported by the positive correlation between both plant productivity and intrinsic microbial respiration with soil pH. In addition, soil microbial biomass C and N, and nitrification were also significantly positively correlated with soil pH. Measurements of respiration following addition of urea and amino acids showed a significant decline in CO₂ evolution with increasing soil acidity, whilst glucose mineralization showed no response to pH. In conclusion, it appears that changes in soil pH significantly affect soil microbial activity and the rate of soil C and N cycling. The evidence suggests that this response is partially indirect, being primarily linked to pH induced changes in net primary production and the availability of substrates. In addition, enhanced soil acidity may also act directly on the functioning of the microbial community itself.     

[噻唑基-2-14C]-毒氟磷在产蛋鸡体内的分布

为阐明毒氟磷在动物体内的分布代谢特征,并深入认识毒氟磷的安全性和膳食风险,本研究选择白羽产蛋鸡为试验对象,[噻唑基-2-¹⁴C]-毒氟磷为同位素示踪剂,研究了毒氟磷在产蛋鸡体内的排泄分布特征。结果表明,毒氟磷在产蛋鸡体内排泄水平高,首次给药24 h后即排泄出当日给药量的82.04%,连续给药7 d后的累计排泄率为82.24%。毒氟磷在组织中的总残留仅占引入量的3.81%,其中胃中残留量占比相对最高,占引入量的2.14%,而肺、肾、脂肪、胰腺中的放射性残留量均不超过引入量的0.01%,膳食评估结果表明在上述内脏组织中的毒氟磷残留无膳食风险。蛋、肌肉、心、脑、脾、卵巢等组织中未检测到放射性残留。本研究为科学评价毒氟磷在家禽中的安全性提供了试验依据。     

Uptake and metabolic fate of [14C]-2,4-dichlorophenol and [14C]-2,4-dichloroaniline in wheat (Triticum aestivum) and soybean (Glycine max)

The uptake and metabolism of [14C]-2,4-dichlorophenol (DCP) and [14C]-2,4-dichloroaniline (DCA) were investigated in wheat and soybean. Seeds were exposed to a nutrient solution containing 50 microM of one of two radiolabeled compounds, and plant organs were harvested separately after 18 days of growth. In wheat, uptake of [14C]-2,4-DCP was 16.67 +/- 2.65 and 15.50 +/- 2.60% of [14C]-2,4-DCA. In soybean, uptake of [14C]-2,4-DCP was significantly higher than [14C]-2,4-DCA uptake, 38.39 +/- 2.56 and 18.98 +/- 1.64%, respectively. In the case of [14C]-2,4-DCP, the radioactivity absorbed by both species was found mainly associated with roots, whereas [14C]-2,4-DCA and related metabolites were associated with aerial parts, especially in soybean. In wheat, nonextractable residues represented 7.8 and 8.7% of the applied radioactivity in the case of [14C]-2,4-DCP and [14C]-2,4-DCA, respectively. In soybean, nonextractable residues amounted to 11.8 and 5.8% of the total radioactivity for [14C]-2,4-DCP and [14C]-2,4-DCA, respectively. In wheat, nonextractable residues were nearly equivalent to extractable residues for [14C]-2,4-DCP, whereas they were greater for [14C]-2,4-DCA. In soybean, the amount of extractable residues was significantly greater for both chemicals. However, in both species, nonextractable residues were mainly associated with roots. Isolation of soluble residues was next undertaken using excised shoots (wheat) or excised fully expanded leaves including petioles (soybean). Identification of metabolite structures was made by comparison with authentic standards, by enzymatic hydrolyses, and by electrospray ionization-mass spectrometric analyses. Both plant species shared a common metabolism for [14C]-2,4-DCP and [14C]-2,4-DCA since the malonylated glucoside conjugates were found as the final major metabolites.     

[苄基-14C]-毒氟磷在大豆中的残留分布和代谢产物动态变化

为深入了解毒氟磷在植物体内的残留代谢规律,以大豆为研究对象,利用¹⁴C示踪法研究了[苄基-¹⁴C]-毒氟磷在大豆中的残留分布特征及代谢产物动态变化规律。结果表明,施药后毒氟磷主要残留在大豆受施叶上,在豆叶中毒氟磷母体的半衰期为15.32 d,施药后代谢产物的残留浓度均随时间推移而不断增加;至施药20 d时,叶片上毒氟磷母体的残留浓度为6.960 mg·kg^-1, 占总放射性活度的53.443%;代谢产物M4、M3、M1+M2的残留浓度分别为3.838、2.431、1.464 mg·kg^-1; 收获时,可食豆子中残留物含量小于总放射性残留的0.3%,其代谢产物组成与叶中相同;母体及M4的相对含量分别为51.932%和20.301%,且两者残留浓度均大于0.050 mg·kg^-1。本试验为客观评价毒氟磷的安全性提供了重要的代谢数据。     

Persistence, fate, and metabolism of [(14)C]metalaxyl in typical Indian soils

The biodegradation of ring-labeled [(14)C]metalaxyl in six Indian soils was examined. The total recovery of radioactivity from soil was 100 +/- 6% of the applied radioactivity. Volatile organics and (14)CO(2) were detected at lower levels. This suggests that neither mineralization nor volatilization is a major route of metalaxyl dissipation. The most rapid degradation of metalaxyl was observed in Bannimantap soil, in which the half-life of metalaxyl was 36 days. An inverse relationship was found when half-lives were plotted against microbial biomass and soil clay content. However, soil total organic carbon did not correlate with metalaxyl persistence. Five metabolites detected by thin-layer chromatography were more polar than metalaxyl.