Degradation of diazinon in soil

The disappearance rate of diazinon in two different soils, at two levels of water content, with two different diazinon concentrations, and in steam-treated and untreated soils has been studied. The rates of disappearance were measured by the slopes of the disappearance curves in a semi-logarithmic coordinate system and by the corresponding half-lives (RL₅₀ in days) for each combination of the factors. The results were examined statistically, and it was found that all of the four factors influenced the degradation rate of diazinon in soil, the greatest effect occurring with steam-treatment, i.e. caused by the micro-organisms in the soils, and the least from the diazinon concentration. Interactions between some of the factors are demonstrated.     

Measuring herbicide volatilization from bare soil

A field experiment was conducted to measure surface dissipation and volatilization of the herbicide triallate after application to bare soil using micrometeorological, chamber, and soil-loss methods. The volatilization rate was measured continuously for 6.5 days and the range in the daily peak values for the integrated horizontal flux method was from 32.4 (day 5) to 235.2 g ha(-1) d(-1) (day 1), for the theoretical profile shape method was from 31.5 to 213.0 g ha(-1) d(-1), and for the flux chamber was from 15.7 to 47.8 g ha(-1) d(-1). Soil samples were taken within 30 min after application and the measured mass of triallate was 8.75 kg ha(-1). The measured triallate mass in the soil at the end of the experiment was approximately 6 kg ha(-1). The triallate dissipation rate, obtained by soil sampling, was approximately 334 g ha(-1) d(-1) (98 g d(-1)) and the average rate of volatilization was 361 g ha(-1) d(-1). Soil sampling at the end of the experiment showed that approximately 31% (0.803 kg/2.56 kg) of the triallate mass was lost from the soil. Significant volatilization of triallate is possible when applied directly to the soil surface without incorporation.     

Solar radiation, relative humidity, and soil water effects on metolachlor volatilization

Pesticide volatilization is a significant loss pathway that may have unintended consequences in nontarget environments. Field-scale pesticide volatilization involves the interaction of a number of complex variables. There is a need to acquire pesticide volatilization fluxes from a location where several of these variables can be held constant. Accordingly, soil properties, tillage practices, surface residue management, and pesticide formulations were held constant while fundamental information regarding metolachlor volatilization (a pre-emergent pesticide) was monitored over a five-year period as influenced by meteorological variables and soil water content. Metolachlor vapor concentrations were measured continuously for 120 h after each application using polyurethane foam plugs in a logarithmic profile above the soil surface. A flux gradient technique was used to compute volatilization fluxes from metolachlor concentration profiles and turbulent fluxes of heat and water vapor (as determined from eddy covariance measurements). Differences in meteorological conditions and surface soil water contents resulted in variability of the volatilization losses over the years studied. The peak volatilization losses for each year occurred during the first 24 h after application with a maximum flux rate in 2001 (1500 ng m(-2) s(-1)) associated with wet surface soil conditions combined with warm temperatures. The cumulative volatilization losses for the 120-hour period following metolachlor application varied over the years from 5 to 25% of the applied active ingredient, with approximately 87% of the losses occurring during the first 72 h. In all of the years studied, volatilization occurred diurnally and accounted for between 43 and 86% during the day and 14 and 57% during the night of the total measured loss. The results suggest that metolachlor volatilization is influenced by multiple factors involving meteorological, surface soil, and chemical factors.     

土壤水分条件对白肋烟产、质量的影响及白肋烟灌溉的土壤水分指标研究

本项研究采用田间和盆栽试验相结合的方法研究了土壤水分条件对白肋烟产、质量和化学成分的影响.结果表明,白肋烟各生育期土壤相对含水量的适宜指标分别为移栽-团棵为70%、团棵-打顶为81%、打顶-采收为76%;干旱指标分别为移栽-团棵为58%、团棵-打顶为71%、打顶-采收为69%.白肋烟成熟阶段需水量相对较多,成熟期土壤相对含水量对白肋烟的成熟速度和化学成分的协调性及评吸质量的影响最为明显,在适宜的土壤相对含水量以下的范围内,表现出随土壤相对含水量升高,成熟速度加快,烟碱含量明显下降,内在化学成分更为协调和评吸质量提高.适宜的土壤相对含水量能明显提高白肋烟产量、产值和等级比重.     

Biological and environmental factors controlling root dynamics and function: effects of root ageing and soil moisture

Understanding factors controlling root dynamics and functioning can lead to more efficient and profitable vineyard management. However, our current understanding of root dynamics and their regulation by plant and environmental factors is limited, particularly under field conditions. This paper presents current understanding of grape root dynamics, highlighting studies using minirhizotron cameras, which directly assess root dynamics, and experiments on roots of known age, which link root phenology and function.
Data summarised here show timing of grape root production varies widely among different regions, as well as among rootstocks and canopy management systems in the same region. Timing of production can be responsive to differences in soil moisture. Lifespan of grape roots, however, appears less affected by soil moisture because of nocturnal hydraulic redistribution. Root function, such as capacity for P and N uptake, declines rapidly with root age. Differences in timing and spatial distribution of root production can effect above-ground growth and vineyard water-use efficiency.
Improving our understanding of when roots grow and are functionally active in agricultural systems can lead to improved water and fertiliser applications, and more precise vineyard management. Because both environmental and biological factors affect root dynamics, simple predictions of timing of root production or standing populations with shoot development are unlikely to be achieved. However, with multi-year data on root dynamics, and environmental and biological factors, regionally specific models of root populations and their functioning may be possible to develop.     

Turbulence effects on volatilization rates of liquids and solutes

Volatilization rates of neat liquids (benzene, toluene, fluorobenzene, bromobenzene, ethylbenzene, m-xylene, o-xylene, o-dichlorobenzene, and 1-methylnaphthalene) and of solutes (phenol, m-cresol, benzene, toluene, ethylbenzene, o-xylene, and ethylene dibromide) from dilute water solutions have been measured in the laboratory over a wide range of air speeds and water-stirring rates. The overall transfer coefficients (K(L)) for individual solutes are independent of whether they are in single- or multi-solute solutions. The gas-film transfer coefficients (kG) for solutes in the two-film model, which have hitherto been estimated by extrapolation from reference coefficients, can now be determined directly from the volatilization rates of neat liquids through a new algorithm. The associated liquid-film transfer coefficients (kL) can then be obtained from measured K(L) and kG values and solute Henry law constants (H). This approach provides a novel means for checking the precision of any kL and kG estimation methods for ultimate prediction of K(L). The improved kG estimation enables accurate K(L) predictions for low-volatility (i.e., low-H) solutes where K(L) and kGH are essentially equal. In addition, the prediction of K(L) values for high-volatility (i.e., high-H) solutes, where K(L) approximately equal to kL, is also improved by using appropriate reference kL values.     

Diurnal variation of carbohydrates in cocksfoot (Dactylis glomerata)

The diurnal variation of carbohydrate content in the leaf blades and leaf sheaths of cocksfoot grown in a controlled environment has been investigated. Most variation was found in the values for alcohol-soluble sugars in the leaf blades, while other fractions showed only small variations.     

Research Watch: Chemical volatilization

Indoor Air.     

Research Watch: PCB volatilization

Sediments.     

Full-field moisture induced deformation in Norway spruce: intra-ring variation of transverse swelling

The transverse hygro-expansion of Norway spruce wood is studied on the growth ring level using digital image correlation. This non-destructive technique offers the possibility for a contactless study of deformation fields of relatively large areas. The measured full-field strains are segmented into individual growth rings. Whereas radial strains closely follow the density progression with the maximum in the dense latewood (LW), tangential and shear strain remain constant except for positions around the edges of the sample. A simple FE three phase growth ring model is in good agreement with the experimental values. The selective activation of individual phases like earlywood (EW), transition wood and LW demonstrates that the radial hygro-expansion is dominated by the EW deformation, whereas tangential deformation is a complex interplay of expansion and compression that needs all tissues to fully develop.     

Chiral signatures show volatilization from soil contributes to polychlorinated biphenyls in grass

Enantiomer fractions (EFs) of PCB 95 and concentrations of PCBs 28/31, 52, 101, 118, 138, 153, and 180 were determined in air. Samples were taken at ~14 day intervals on a vertical gradient at an urban background site in Birmingham U.K. in summer 2009 (114 days) and spring 2010 (84 days). EFs in air at 3 cm height were nonracemic (average 0.453 (2009) and 0.468 (2010)) and differed significantly (p < 0.05) from the racemic EFs in air at 10, 40, 90, and 130 cm. EFs in soil (average 0.452 (2009) and 0.447 (2010)) closely matched those in air at 3 cm, while those in grass (average 0.468 (2009) and 0.484 (2010)) were intermediate between those in soil and the racemic EFs in air at ≥ 10 cm. This implies that at the study site, PCBs volatilize from soil to an extent discernible only at the soil:air interface, and that PCBs in grass arise due to foliar uptake of volatile emissions from soil. Atmospheric concentrations of ΣPCBs increased significantly (p < 0.05) with increasing height. Combined with the chiral signature data, this suggests the influence of PCB emissions from soil on airborne concentrations decreases with altitude, while that of emissions from the built environment increases.     

Aging of organochlorine pesticides and polychlorinated biphenyls in muck soil: volatilization, bioaccessibility, and degradation

An organic rich muck soil which is highly contaminated with native organochlorine pesticide (OCs) was spiked with known amounts of (13)C-labeled OCs and nonlabeled polychlorinated biphenyls (PCBs). Spiked soils were aged under indoor, outdoor, and sterile conditions and the change in volatility, surrogate bioaccessibility, and degradation of chemicals was monitored periodically over 730 d. Volatility was measured using a fugacity meter to characterize the soil-air partition coefficient (K(SA) = C(SOIL)/C(AIR)). The fraction of bioaccessible residues was estimated by comparing recoveries of chemical with a mild extractant, hydroxylpropyl-β-cyclodextrin (HPCD) vs a harsh extractant, DCM. K(SA) of the spiked OCs in the nonsterile (Indoor, Outdoor) soils were initially lower and approached the K(SA) of native OCs over time, showing reduction of volatility upon aging. HPCD extractability of spiked OCs and PCBs were negatively correlated with K(SA), which suggests that volatility can be used as a surrogate for bioaccessibility. Degradation of endosulfans, PCB 8 and 28 was observed in the nonsterile soils, and (13)C(6)-α-HCH showed selective degradation of the (+) enantiomer. Enantiomer fractions (EF) in air and HPCD extracts were lower than in nonsterile soils, suggesting greater sequestering of the (+) enantiomer in the soil during microbial degradation.     

Pathways and relative contributions to arsenic volatilization from rice plants and paddy soil

Recent studies have shown that higher plants are unable to methylate arsenic (As), but it is not known whether methylated As species taken up by plants can be volatilized. Rice (Oryza sativa L.) plants were grown axenically or in a nonsterile soil using a two-chamber system. Arsenic transformation and volatilization were investigated. In the axenic system, uptake of As species into rice roots was in the order of arsenate (As(V)) > monomethylarsonic acid (MMAs(V)) > dimethylarsinic acid (DMAs(V)) > trimethylarsine oxide (TMAs(V)O), but the order of the root-to-shoot transport index (Ti) was reverse. Also, volatilization of trimethylarsine (TMAs) from rice plants was detected when plants were treated with TMAs(V)O but not with As(V), DMAs(V), or MMAs(V). In the soil culture, As was volatilized mainly from the soil. Small amounts of TMAs were also volatilized from the rice plants, which took up DMAs(V), MMAs(V), and TMAs(V)O from the soil solution. The addition of dried distillers grain (DDG) to the soil enhanced As mobilization into the soil solution, As methylation and volatilization from the soil, as well as uptake of different As species and As volatilization from the rice plants. Results show that rice is able to volatilize TMAs after the uptake of TMAs(V)O but not able to convert inorganic As, MMAs(V) or DMAs(V) into TMAs and that the extent of As volatilization from rice plants was much smaller than that from the flooded soil.     

Diurnal variation on tear stability and correlation with tear cytokine concentration

PurposeTo investigate the effect of time of day on tear evaporation rate (TER) and tear break-up time, and its possible relationship with the concentration of inflammatory tear molecules (cytokines) in healthy subjects.MethodsParticipants with healthy ocular surfaces attended 3 visits, including the screening visit (V0), the 2nd visit (V1) and the 3rd visit (V2). There were 7-day intervals between visits. Participants with Dry Eye Disease (DED) were excluded by using appropriate clinical tests during V0. Clinical evaluation (TER and Non-Invasive Tear Break-Up Time (NITBUT)) and tear collection were performed during V1 and V2, between 9 and 10AM and 3-4PM. The relative humidity and temperature of the examination room were also measured. The tear fluid concentrations of 15 cytokines were measured by multiplex bead analysis.ResultsSeven men and 10 women (mean age ± S.D; 25.1 ± 6.63 years old) participated in the study. There were no differences in neither the TER and NITBUT outcomes, nor humidity and temperature among times or visits. Eleven out of the 15 cytokines measured were detectable in tear fluids in > 50% of the participants. In the tear levels, no significant (p > 0.05) inter- and/or intra-day differences were detected for EGF, fractalkine, IL-1RA, IL-1β and IP-10. However, significant inter-day differences were found in the tear levels of IL-10 (p = 0.027), IFN-γ (p = 0.035) and TNF-α(p = 0.04) and intra-day differences in the tear levels of IL-8/CXCL8 (p = 0.034) and MCP-1 (p = 0.002). A significant correlation between TER and IL1-β, IL-2, and Fractalkine (p = 0.03, p = 0.03 and p = 0.046, respectively) was found at V1.ConclusionsNITBUT and TER values had no significant variability over the course of a day (AM versus PM), or on different days in healthy participants when humidity and temperature were constant. However, some tear molecule levels did show inter- and intra-day variability, having an inconsistent and moderate correlation with TER diurnal variation.     

土壤水份监测创新技术:探地雷达(GPR)

从事葡萄酒酿造和葡萄栽培的人员都知道,土壤水份对于酿酒葡萄的栽培品质来说是至关重要的,但是准确监测土壤的水份含量却是一项困难而且耗费较大的工作。现在加州大学柏克莱分校的科学家们正在进行一项创新性研究,利用探地雷达     

Enzyme inactivation kinetics: Coupled effects of temperature and moisture content

Enzymes are often dried for stability reasons and to facilitate handling. However, they are often susceptible to inactivation during drying. It is generally known that temperature and moisture content influence the enzyme inactivation kinetics. However, the coupled effect of both variables on enzyme inactivation over a broad temperature–moisture content range is still not well understood. Therefore, the inactivation of β-galactosidase in maltodextrin matrix is investigated using a newly developed method. An improved kinetic modelling approach is introduced, to predict the inactivation over a large range of temperature–moisture values. The model assumes a two-step inactivation mechanism involving reversible unfolding and irreversible inactivation. The model is able to describe the inactivation kinetics of β-galactosidase accurately, showing the temperature-dependent kinetic transition from reversible unfolding to irreversible inactivation limited. Application of this approach can provide immediate understanding of the effect of processing on enzyme inactivation and indicates the processes’ critical points, which offers the possibility for optimisation.     

变色硅胶吸湿及变色特性研究

目的通过建立变色硅胶吸湿模型和色度值与吸湿量关系的模型,明确变色硅胶颜色变化与环境湿度的关系,进而为基于变色硅胶的湿度指示卡提供理论依据。方法建立变色硅胶在不同湿度和温度下的数学模型,并进行验证实验。结果变色硅胶饱和吸湿量与环境湿度的关系模型为:Q_h=-0.00434RH~2+0.7113RH+2.6664,R~2=0.9933;所用数学模型模型(Q_t=Q_h*[1-exp(--k*t)])和Arrhenius方程拟合所得方程的判定系数R~2都在0.99以上,验证实验的平均相对误差在90%RH和70%RH时分别为1.51%和2.85%;变色硅胶吸湿量与色度值(b值)的线性回归方程为:b=20.488-0.654 Q_t,R~2=0.9799,验证实验的平均相对误差为5.24%,远远低于10%的可接受水平。结论所建模型能够很好地预测变色硅胶的吸湿过程及吸湿后的颜色变化情况,可据此制作基于变色硅胶的湿度指示卡。     

基于Fortran程序的储粮通风温度和水分变化的模拟研究

小麦储藏过程中,温度和水分是安全储粮的关键因素。迄今为止,相关研究人员设计了多种数学模型来预测通风过程中小麦堆的温度和水分,然而这些模型一般需要占用大量的内存且计算周期很长。基于局部热质平衡原理采用Fortran程序设计了一套新的数学模型,有效地解决了以上问题,并且首次提出R值,使水分传递更加接近实际情况,通过与实验结果的比较,验证了该模型的准确性与可行性,对以后指导安全储粮具有非常重要的意义。