Degradation of fipronil under laboratory conditions in a tropical soil from sirinhaém pernambuco,Brazil

The objective of this research was to assess the degradation of fipronil [5-amino-1-(2,6-dichloro-α,α,α -trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile] in soils from sugar cane fields in Northeastern Brazil. Degradation experiments were carried out under laboratory conditions (controlled temperature and in the dark), where sterile and non-sterile soils (Ustoxs) were incubated [under moisture content of 55% of the water holding capacity (WHC)] and analyzed for fipronil disappearance and metabolite formation. Microbial communities present in the soil degrade fipronil. However, biodegradation seems to be dependent on the bioavailability of the fipronil and the half-life according to the zero-order model. Fipronil degradation rate appeared to be biphasic. Degradation fipronil ranged from 83 days (initial concentration = 978 ng g^{? 1}; short-term experiment) to 200 days (initial concentration = 689 ng g^{? 1}; long-term experiment). This an initial slower rate followed by a faster rate after 90 days of incubation may lead to shorter half-life than that calculated with the zero-order model. The sulfone derivative (an oxidation product) was the predominant metabolite, but the sulfide (a reduction product) and amide (a hydrolysis product) derivatives were also formed under non-sterile conditions after 120 days of incubation. The metabolites underwent further biodegradation, particularly the sulfone derivative. Bioavailability appears to affect fipronil degradation in soils with an effective capacity to adsorb fipronil (such as Ustoxs), while redox potential was important for the formation of metabolites. Despite the fine texture, more aerobic sites were present, thus favoring the formation of the sulfone metabolite over that of the sulfide metabolite. Therefore, microaggregation of Ustoxs, with high clay content, played a very important role in determining the types of metabolites formed.     

Paraquat Adsorption,Degradation, and Remobilization in Tropical Soils of Thailand

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with K _f values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0–5 cm layer under field conditions and in the 0–1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT₅₀ at 36–46 days and DT₉₀ around 119–152 days.     

Nutrient concentrations within and below root zones from applied chicken manure in selected Hawaiian soils

The objective of this study was to evaluate the effects of chicken manure (CM) application rates on nutrient concentrations within and below the root zone of sweet corn (Zea mays L. subsp. mays) under Hawaiian conditions. The research was conducted in leeward (Poamoho) and windward (Waimanalo) areas of Oahu, Hawaii, where contrasts exist in both climatic and soil conditions. Suction cup were used to collect soil solutions from 30 and 60 cm depths. Soil solutions were collected six times during the growing season at each location and analyzed for different nutrients (N, P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu), nitrate-nitrogen (NO₃–N), ammonium-nitrogen (NH₄–N), electrical conductivity (EC), and pH. Analysis showed that CM rates significantly affected the concentration of macro-nutrients below the root zone at Poamoho and within the root zone at Waimanalo. In general, nutrient concentration increased with the increasing rates of CM application. There was a significant effect of CM on micro-nutrients except below the root zone at Poamoho. CM significantly affected NO₃–N concentration within the root zone for 15, 60 days after planting (DAP) at Poamoho, and 16, 28 DAP at Waimanalo. The effect was also significant on total nitrogen (N) concentration in the root zone across the two growing seasons at Waimanalo. There was a highly significant correlation between total N and NO₃–N, and EC within and below the root zone.     

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of α and β endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 μg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan–degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.     

新型旋流除尘器在100万吨/年乙烯装置尾气除尘中的应用

为了去除石化行业乙烯装置裂解炉烧焦尾气中的颗粒污染物,对传统用于气体除尘的旋风分离器进行改进,设计了一种新型旋流除尘器,并将其应用于乙烯装置裂解炉清焦过程中.经新型旋流除尘器处理后,出口气中焦粉颗粒质量浓度基本控制在15 mg/m3以下,符合GB 31570—2016《石油炼制工业污染物排放标准》的排放要求(≤20 m...     

N-methylcarbamate pesticides and their phenolic degradation products: hydrolytic decay,sequestration and metal complexation studies

We report on the rates of decomposition of a group of N-methylcarbamate (NMC) pesticides (carbaryl, carbofuran and propoxur) under pre-determined tropical field conditions. Rates of decomposition for three NMCs were determined at pH 7.08 and T?=?20?°C and pH 7.70 and T = 33?°C respectively, as follows: carbaryl (78?days and 69?days); carbofuran (143?days and 83?days) and propoxur (116?days and 79?days). Investigation on methods for removal of NMCs and their phenolic decomposition products shows that activated charcoal outperforms zeolite, alumina, diatomaceous earth, cellulose and montmorillonite clay in the removal of both NMCs and phenols from aqueous solution. Furthermore, metal complexation studies on the NMCs and phenols showed that Fe (III) forms a complex with isopropoxyphenol (IPP) within which the Fe:IPP ratio is 1:3, indicative of the formation of a metal chelate complex with the formula Fe(IPP)₃.     

静电旋风除尘技术的现场试验

对静电旋风除尘技术的机理进行了探讨,现场试验表明,此技术用于电厂旋风水膜除尘器的改造,可将平均除尘效率由９２．５５％到９８．４％,且对不同浓度的烟尘除尘效率比较稳定,在处理烟气量为１０６００Ｎｍ＾３／ｈ时,阻力为８００－９２０Ｐａ,高压电源的单位能耗为０．２Ｗ·ｈ／（ｍ＾３·ｈ）。     

海南岛甘什岭低地次生雨林土壤有机碳及影响因素

热带雨林是世界上最复杂的森林生态系统,在全球碳循环中发挥着重要作用.热带低地次生雨林是受人类干扰较为严重的雨林类型,而关于其土壤有机碳库的研究甚少.以海南岛甘什岭热带低地次生雨林为研究对象,通过野外调查采样与室内分析相结合等方法,研究了经人为采伐干扰后自然更新恢复形成的3种林分类型(Ⅰ为较大采伐强度下恢复的灌丛与低矮乔...     

Connecting science,policy, and implementation for landscape‐scale habitat connectivity

We examined the links between the science and policy of habitat corridors to better understand how corridors can be implemented effectively. As a case study, we focused on a suite of landscape‐scale connectivity plans in tropical and subtropical Asia (Malaysia, Singapore, and Bhutan). The process of corridor designation may be more efficient if the scientific determination of optimal corridor locations and arrangement is synchronized in time with political buy‐in and establishment of policies to create corridors. Land tenure and the intactness of existing habitat in the region are also important to consider because optimal connectivity strategies may be very different if there are few, versus many, political jurisdictions (including commercial and traditional land tenures) and intact versus degraded habitat between patches. Novel financing mechanisms for corridors include bed taxes, payments for ecosystem services, and strategic forest certifications. Gaps in knowledge of effective corridor design include an understanding of how corridors, particularly those managed by local communities, can be protected from degradation and unsustainable hunting. There is a critical need for quantitative, data‐driven models that can be used to prioritize potential corridors or multicorridor networks based on their relative contributions to long‐term metacommunity persistence.