Repeated batch and continuous degradation of chlorpyrifos by Pseudomonas putida

The present study was undertaken with the objective of studying repeated batch and continuous degradation of chlorpyrifos (O,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate) using Ca-alginate immobilized cells of Pseudomonas putida isolated from an agricultural soil, and to study the genes and enzymes involved in degradation. The study was carried out to reduce the toxicity of chlorpyrifos by degrading it to less toxic metabolites. Long-term stability of pesticide degradation was studied during repeated batch degradation of chlorpyrifos, which was carried out over a period of 50 days. Immobilized cells were able to show 65% degradation of chlorpyrifos at the end of the 50th cycle with a cell leakage of 112 × 10³ cfu mL^?1. During continuous treatment, 100% degradation was observed at 100 mL h^?1 flow rate with 2% chlorpyrifos, and with 10% concentration of chlorpyrifos 98% and 80% degradation was recorded at 20 mL h^?1 and 100 mL h^?1 flow rate respectively. The products of degradation detected by liquid chromatography–mass spectrometry analysis were 3,5,6-trichloro-2-pyridinol and chlorpyrifos oxon. Plasmid curing experiments with ethidium bromide indicated that genes responsible for the degradation of chlorpyrifos are present on the chromosome and not on the plasmid. The results of Polymerase chain reaction indicate that a ~890-bp product expected for mpd gene was present in Ps. putida. Enzymatic degradation studies indicated that the enzymes involved in the degradation of chlorpyrifos are membrane-bound. The study indicates that immobilized cells of Ps. putida have the potential to be used in bioremediation of water contaminated with chlorpyrifos.     

The metabolic fate of 14C‐parathion by some fresh water phytoplankton and its possible effects on the algal metabolism

Abstract

The growth and total carbohydrate contents of Nostoc muscorum and Tolypothrix tenuis were greatly and significantly reduced by the application of parathion. “Chlorophyll a”, carotene biosynthesis and the rate of glucose absorption were enhanced after supplementation of parathion to the culture media of both cyanobacteria. Nitrogen released to the media, total nitrogen content and total nitrogen fixed were increased in both organisms‐ Increase in protein content was accompanied by remarkable drop in amino, peptide and ammonia fractions‐ Phosphorus uptake, RNA, DNA and total phosphorus content were accelerated to reach maximum accumulation at the highest insecticide level. In metabolism study using ¹⁴C‐labelled compound, parathion was readily degraded by Nostoc and Tolypothrix. Following ten days incubation, the aqueous fractions contained 21.1% and 18.1% of the initial activity in Nostoc and Tolypothrix respectively. TLC analysis of the hydrolytic products revealed the presence of three metabolites: p‐aminophenol, p‐nitrophenol and aminoparathion.     

g-C3N4制备及其协同PDS可见光催化降解布洛芬的研究

以尿素为主要原料,采用热聚合法在不同条件下制备了光催化剂g-C3N4(石墨相碳化氮),通过改变尿素在马弗炉中加热的温度(350℃、400℃、450℃、500℃)和时间(0.5 h、1 h、1.5 h),得到不同烧结温度和时间的光催化剂,并对其进行X射线衍射(XRD)、扫描电子显微镜(SEM)、傅立叶红外光谱分析仪(FT-IR)、紫外可见漫反射光(UV-Vis)表征,并通过可见光光催化降解布洛芬试验,探究了制备温度、时间对g-C3N4光催化性能的影响;并在溶液中加入PDS(过硫酸钾),联合g-C3N4在可见光下光催化降解布洛芬。结果表明,当烧结温度为500℃、烧结时间为1.5 h时,制备的g-C3N4在可见光区有较强吸收且具有较大的比表面积,以致其表现出最佳的光催化性能;PDS的存在对布洛芬的降解有促进作用,且加快了g-C3N4对布洛芬的光催化降解,相比于纯g-C3N4,4 h内布洛芬的降解率由63%提升为90.5%。以异丙醇、甲醇、对苯醌、草酸钠、重铬酸钾、甲醇分别为羟基自由基(·OH)、·OH和硫酸根自由基(SO4^-·)、超氧自由基(·O2-)、空穴(h+)、电子(e^-)的捕获剂。通过对反应过程的活性物种鉴定,·OH、SO4^-·、h+、e^-均参与了布洛芬的光催化降解,其中h+在反应中的贡献率达到了82.9%,在降解布洛芬过程中起主导作用;在反应体系中添加PDS后,催化剂g-C3N4的荧光强度变小,即加入PDS能够有效降低g-C3N4的光生空穴与电子的复合率,提高g-C3N4的光催化性能。     

Rubber cultivation and sustainable development in Xishuangbanna,China

SUMMARY

Xishuangbanna in southwest China is a tropical and subtropical region with extraordinary traditional cultures and attractive landscapes. Rubber cultivation is a key production source undergoing rapid growth. It contributes substantially to improvement of the local economic situation and partially replaces traditional slash-and-burn agriculture in the uplands, but it also results in biodiversity loss and environmental degradation and disturbs the peaceful life of the indigenous people. We discuss the traditional ecological knowledge (TEK) preserved in daily practices and the present types of rubber plantations and suggest the application of TEK, in particular, the indigenous land-use experience to rubber cultivation, in order to promote sustainability in local economic development and ecological well-being.     

Bivariate cointegration between poverty and environment: a case study of Pakistan (1980–2009)

The objective of this paper is to empirically investigate a two-way statistical relationship between the agriculture environment and rural poverty. To recognise the relationship between the two variables, a time series, co-integration and Granger causality tests have been employed. Secondary data pertaining to Pakistan from 1980–2009 on rural poverty and environmental factors (such as commercial energy consumption, water availability and total cropped area) have been used for the analysis. The empirical results only moderately support the conventional view that rural poverty has a significant long-term casual effect on environmental proxies in Pakistan. The present study finds evidence of uni-directional causality between poverty and the environment in the context of the agriculture sector in Pakistan.     

A Contemporary Assessment of Change in Humid Tropical Forests

Abstract: In recent decades the rate and geographic extent of land‐use and land‐cover change has increased throughout the world's humid tropical forests. The pan‐tropical geography of forest change is a challenge to assess, and improved estimates of the human footprint in the tropics are critical to understanding potential changes in biodiversity. We combined recently published and new satellite observations, along with images from Google Earth and a literature review, to estimate the contemporary global extent of deforestation, selective logging, and secondary regrowth in humid tropical forests. Roughly 1.4% of the biome was deforested between 2000 and 2005. As of 2005, about half of the humid tropical forest biome contained 50% or less tree cover. Although not directly comparable to deforestation, geographic estimates of selective logging indicate that at least 20% of the humid tropical forest biome was undergoing some level of timber harvesting between 2000 and 2005. Forest recovery estimates are even less certain, but a compilation of available reports suggests that at least 1.2% of the humid tropical forest biome was in some stage of long‐term secondary regrowth in 2000. Nearly 70% of the regrowth reports indicate forest regeneration in hilly, upland, and mountainous environments considered marginal for large‐scale agriculture and ranching. Our estimates of the human footprint are conservative because they do not resolve very small‐scale deforestation, low‐intensity logging, and unreported secondary regrowth, nor do they incorporate other impacts on tropical forest ecosystems, such as fire and hunting. Our results highlight the enormous geographic extent of forest change throughout the humid tropics and the considerable limitations of the science and technology available for such a synthesis.     

The nexus between eco-friendly technology and environmental degradation in India: Does the N or inverted N-shape load capacity curve(LCC) hypothesis hold?

This study aims to investigate the impact of eco-friendly technology on environmental degradation indicated using the load capacity factor (LCF) with the framework of the Load Capacity Curve (LCC) hypothesis. In this regard, an environmental degradation function is formed and analyzed using the Augmented Autoregressive Distributed Lag (AARDL) approach during the period spanning from 1975 to 2021 for India. The outcome indicates that eco-friendly technology reduces the LCF, thereby fostering environmental degradation in the long run, but the relationship is not significant in the short run. Further, an N-shaped LCC hypothesis has been observed in both long and short runs. Besides, energy consumption exhibits a LCF reducing or environmental degradation boosting role in the short run and long run. These findings are consistent with other models that are used to check the robustness of AARDL-based results. Thus, the study recommends policies for promoting eco-friendly technology, judicious economic growth, and cautious energy consumption to attain sustainable development by increasing the LCF in India.     

Efficient photocatalysis of tetracycline hydrochloride (TC-HCl) from pharmaceutical wastewater using AgCl/ZnO/g-C3N4 composite under visible light: Process and mechanisms

AgCl/ZnO/g-C₃N₄, a visible light activated ternary composite catalyst, was prepared by combining calcination, hydrothermal reaction and in-situ deposition processes to treat/photocatalyse tetracycline hydrochloride (TC-HCl) from pharmaceutical wastewater under visible light. The morphological, structural, electrical, and optical features of the novel photocatalyst were characterized using scanning electron microscopy (SEM), UV-visible light absorption spectrum (UV–Vis DRS), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and transient photocurrent techniques. All analyses confirmed that the formation of heterojunctions between AgCl/ZnO and g-C₃N₄ significantly increase electron-hole transfer and separation compared to pure ZnO and g-C₃N₄. Thus, AgCl/ZnO/g-C₃N₄ could exhibit superior photocatalytic activity during TC-HCl assays (over 90% removal) under visible light irradiation. The composite could maintain its photocatalytic stability even after four consecutive reaction cycles. Hydrogen peroxide (H₂O₂) and superoxide radical (^·O₂) contributed more than holes (h⁺) and hydroxyl radicals (^·OH) to the degradation process as showed by trapping experiments. Liquid chromatograph-mass spectrometer (LC-MS) was used for the representation of the TC-HCl potential degradation pathway. The applicability and the treatment potential of AgCl/ZnO/g-C₃N₄ against actual pharmaceutical wastewater showed that the composite can achieve removal efficiencies of 81.7%, 71.4% and 69.0% for TC-HCl, chemical oxygen demand (COD) and total organic carbon (TOC) respectively. AgCl/ZnO/g-C₃N₄ can be a prospective key photocatalyst in the field of degradation of persistent, hardly-degradable pollutants, from industrial wastewater and not only.     

Fate and degradation of triasulfuron in soil and water under laboratory conditions

The behavior and fate of triasulfuron (TRS) in water and soil systems were examined in laboratory studies. The degradation of TRS in both buffer solution and soil was highly pH-sensitive. The rate of degradation could be described with a pseudo first-order kinetic and was much faster at pH 4 than at pH 7 and 9. Aqueous hydrolysis occurred by cleavage of the sulfonylurea bridge to form 2-(2-chloroethoxy) benzenesulfonamide (CBSA) and [(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] (AMMT). AMMT was unstable in aqueous solutions in any pH condition but it degraded more quickly at pH 4 and 9. CBSA did not degrade in aqueous solutions or in enriched cultures but it underwent a quick degradation in the soil. The rates of TRS degradation in sterile and non-sterile soils were similar, suggesting that microorganisms played a minimal role in the breakdown process. This hypothesis is supported by the results of studies on the degradation of TRS by enriched cultures during which the molecule underwent a prevalently chemical degradation.     

Photochemical degradation of methylparathion in the presence of humic acid

Photochemical degradation of methylparathion (O,O,-dimethyl O-4 nitrophenylphosphorothioate) in the presence of humic acid between pH 2 and 7 was monitored by differential pulse polarography. Humic acid was not electro-active under the experimental conditions used in this study. Only the pesticide and its main degradation product at pH 2 exhibited polarographic signals. Photolysis of methylparathion in acid media was sensitized by humic acid since the pesticide did not degrade in the absence of this compound. Methylparathion degradation in the presence of humic acid was observed at each of the studied pHs. The reaction was first-order with rate constant values ranging from 2 × 10^?3 to 6.3 × 10^?3 min^?1.