Fate of metolachlor under subirrigation in a sandy soil: A lysimeter study

Abstract

A three‐year field lysimeter study was conducted to investigate the role of subirrigation systems in reducing the risk of water pollution from metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methlphenyl)‐N‐(2‐methoxy‐l‐methylethyl)acetamide). Nine large PVC lysimeters, 1 m long x 0.45 m diameter, were packed with a sandy soil. Three water table management treatments, i.e. two subirrigation treatments with constant water table depths of 0.4 and 0.8 m, respectively, and a free drainage treatment in a completely randomized design with three replicates were used. Corn (Zea mays L.) was grown in each lysimeter, and at the beginning of summer of each year metolachlor was applied, at the locally recommended rate of 2.75 kg a.i./ha. Soil and water samples were collected at different time intervals after each natural or simulated rainfall event. Metolachlor was extracted from these samples and analyzed using Gas Chromatography.

Results obtained in this three year study, (1993–1995), lead to the conclusion that metolachlor is quite mobile since it leached to a depth of 0.85 m below the soil surface quite early in the growing season. Metolachlor concentrations decreased with depth as well as with time. The shallower water table in the 0.4 m subirrigation treatment showed less residues in the soil solution than that of other treatments. However, a mass balance study, supported by an independent laboratory investigation, shows that water table management, statistically, has no significant effect on the reduction of metolachlor residues in sandy soils.     

Degrading a mixture of three textile dyes using photo-assisted electrochemical process with BDD anode and O2–diffusion cathode

In this paper, degradation of a mixture of three azo dyes was studied by the photo-assisted electrochemical process using an O₂-diffusion cathode containing carbon nanotubes and boron-doped diamond (BDD) anode. The concentration of three textile dyes (C.I. Acid Orange 8 (AO8), C.I. Acid Orange 10 (AO10), and C.I. Acid Orange 12 (AO12)) was determined simultaneously despite the severe overlap of their spectra. For this purpose, partial least square (PLS), as a multivariate calibration method, was utilized based on recording UV–Vis spectra during the decolorization process. Moreover, the central composite design was used for the modeling of photo-assisted electrochemical decolorization of the aqueous solutions containing three dyes. The investigated parameters were the initial concentration of three dyes, applied current and reaction time. Analysis of variance (ANOVA) revealed that the obtained regression models match the experimental results well with R (Khataee et al. 2010, Clean-Soil Air Water 38 (1):96–103, 2010) of 0.972, 0.971, and 0.957 for AO8, AO10, and AO12, respectively. Three-dimensional surface and contour plots were applied to describe the relation between experimental conditions and the observed response. The results of TOC analysis confirmed good ability of proposed photo-assisted electrochemical process for degradation and mineralization of textile industry wastewater.     

Uptake and distribution of phenanthrene and pyrene in roots and shoots of maize (Zea mays L.)

Polycyclic aromatic hydrocarbons as byproducts of carbon-based fuel combustion are an important group of pollutants with wide distribution in the environment. Polycyclic aromatic hydrocarbons are known as toxic compounds for almost all organisms. Different plant species can uptake polycyclic aromatic hydrocarbons by roots and translocate them to various aerial parts. The aim of this study is to investigate the uptake, translocation, and accumulation of pyrene and phenanthrene in maize under controlled conditions. Seeds were cultivated in perlite containing 25, 50, 75, and 100 ppm of phenanthrene and pyrene, and their concentrations in the roots and shoots of the plants were measured using high-performance liquid chromatography technique after 7, 14, and 21 days. The results revealed that phenanthrene naturally existed in maize and its concentration showed a time-dependent decrease in shoots and roots. In contrast, the concentration of pyrene was increased in the roots and reduced in the shoots. Although pyrene had higher uptake than phenanthrene in roots of maize, the translocation factor value for pyrene was lower than for phenanthrene. According to these findings, phenanthrene could be metabolized in maize in the shoot and root tissues, but pyrene had more tendency to be accumulated in roots.

     

A ternary CdS/AgBr/Ag3PO4 nanocomposite: characterization and the kinetics of its photocatalytic activity

Environmental Science and Pollution Research - A ternary CdS/AgBr/Ag3PO4 coupled system was prepared, characterized by different techniques, and used for the photodegradation of methylene blue...     

Subnational exposure to secondhand smoke in Iran from 1990 to 2013: a systematic review

Environmental Science and Pollution Research - Every year, almost eight million people die from tobacco-related diseases, among which around 1.2 million die from secondhand smoke (SHS) exposure....     

A detailed kinetic investigation on the effects of hydrogen enrichment on the performance of gas-fueled SI engine

This study investigates the effects of hydrogen enrichment on formation of pollutants and greenhouse gases in gas-fueled spark ignition engines. To this end, a previously validated detailed mechanism is embedded with a comprehensive one-dimensional engine model and the results are verified with experimental observations at different compression ratios and engine loads. The simulations are then performed for different mixtures of hydrogen and natural gas. The results indicate that adding hydrogen increases the cylinder peak pressure at different loads and compression ratios, despite the fact that reduces the amount of carbon monoxide, carbon dioxide, and methane in all the conditions.     

Lemon Balm (Melissa officinalis) Stalk: Chemical Composition and Fiber Morphology

This work investigates the potentials of lemon balm (Melissa officinalis L.) stalk (LBS), a massive waste part of medicinal plant, for pulp and papermaking by assessing its fiber characteristics and chemical composition. In addition, LBS properties were compared with some important agro-residues such as bagasse stalk (BS), cotton stalk (CS) and tobacco stalk (TS). There is no information about suitability of the LBS in the open literature. Chemically, LBS fibers contain a relatively high percentage of alpha-cellulose (32.7%), but a low percentage of lignin (25%), which benefits pulping and bleaching. The hemicelluloses in LBS are mainly glucose and xylose. Ash content was about 6%, superior to the average value corresponding to woods, which makes pulping difficult. It was verified that the chemical compositions of the studied agro-residues vary significantly. Morphologically, the LBS fibers are comparable to those of hardwoods. Rather a significant amount of parenchyma cells was found in LBS. The TS has the highest average fiber length, while the LBS has the least, and the lengths of BS and CS fibers fall in between. In general, based on the results of this study, some propositions can be made about the possible applications of LBS as a non-wood renewable source of natural products for use in the production of pulp and paper.     

Geochemical characterisation of pyrite oxidation and environmental problems related to release and transport of metals from a coal washing low-grade waste dump, Shahrood, northeast Iran

Pyrite oxidation and release of the oxidation products from a low-grade coal waste dump to stream, groundwater and soil was investigated by geochemical and hydrogeochemical techniques at Alborz Sharghi coal washing plant, Shahrood, northeast Iran. Hydrogeochemical analysis of water samples indicates that the metal concentrations in the stream waters were low. Moreover, the pH of the water showed no considerable change. The analysis of the stream water samples shows that except the physical changes, pyrite oxidation process within the coal washing waste dump has not affected the quality of the stream water. Water type was determined to be calcium sulphate. The results of the analysis of groundwater samples indicate that the pH varies from 7.41 to 7.51. The concentrations of the toxic metals were low. The concentration of SO4 is slightly above than its standard concentration in potable water. It seems that the groundwater less affected by the coal washing operation in the study area. Geochemical analysis of the sediment samples shows that Fe concentration decreases gradually downstream the waste dump with pH rising. SO(4) decreases rapidly downstream direction. Copper, Zn and Co concentrations decrease with distance from the waste dump due to a dilution effect by the mixing of uncontaminated sediments. These elements, in particular, Zn are considerably elevated in sediment sample collected at the nearest distance to the waste dump. There is no doubt that such investigations can help to develop an appropriate water remediation plan.