Assessment of Noise Exposure of Sawmill Workers in Southwest,Nigeria

Economic wood processing employs the use of industrial machines for cutting, shaping, milling, and sawing timber, thereby leading to the generation of high levels of noise. Published data from empirical studies have categorized noise as an environmental hazard of global significance. Furthermore, noise exposure limits for different industries and all the industrial machines available has not been formally established as it presently exists in developed nations around the world. Therefore, this study assessed the daily exposure of sawmills workers to noise in Southwestern Nigeria. Reconnaissance surveys were first carried out in Osun, Oyo, Ondo, Ekiti, Lagos, and Ogun States to select sawmills that were fully operational and fit for the study. Two fully functional sawmills in two cities of each State were eventually selected for data collection, making a total of 24 sawmills, while the Circular Machines (CM), Planer Machines (PM), and Band-saw Machines (BM) were the machines in each sawmill considered. Two machines each of CM, PM, and BM were considered in each sawmill, making a total of forty-eight (48) machines each of CM, PM, and BM. Sound data were collected between 7 am and 7 pm each day for six days (between Monday and Saturday) using Extech 407732 sound level meter and all stabilized measurements were taken three times at different intervals. The data collected were in three different periods: Machine No-work Period (NP_m), Machine Idle Period (IP_m), and Machine Working Period (WP_m). A two–way Analysis of Variance (ANOVA) was carried out at P < 0.05 to determine whether there is a significant difference in the sound level average before and after the break, for both the idle and working periods of the three machines considered. This was also done to determine whether there is a significant difference between the sound level average of the results collected during idle and working periods of the three machines. Noise Pollution Levels (L_np) ranged from 83.20 dB (PM) to 107.65 (BM) and 93.42 (CM and PM) – 116.00 (BM) respectively, while IP_m also gave the least noise pollution level of 95.79 dB and WP_m gave the highest level of 102.88 dB. The results revealed that all the machines’ L_np values in the working period are more than the 90 dB acceptable limit the recommendation value of 90 dB while 89.6% of CMs, 75% of PMs, and 89.6% of BM had their L_np above 90 dB in the idle period respectively. The minimum and the maximum noise dose levels for IP_m, WP_m and overall are 0.09 (BM) and 2.37 (CM), 0.50 (CM), and 4.77 (PM) and 0.69 (BM) and 6.64 (PM) respectively. The study found out that the fundamental contributing factors to the high noise levels in sawmills are poor machine maintenance, use of old and obsolete machines, poor housekeeping strategy, limited space, workers’ negligence, lack of PPE, and lack of occupational safety training. The study recommends that proper workplace practices such as use of personal protective equipment, new and modern machines, training, and occupational safety programmes be implemented in the considered sawmills.     

利用反射太赫兹时域强度分布定量检测沙粒中的微量原油

原油污染是海洋生物和环境安全的主要威胁之一,检测近海沙粒中的微量原油对于环境保护和原油勘探有着重要意义.本文采用反射式太赫兹时域波形对近海沙粒中的原油进行定量检测,详细地分析了延迟时间与沙粒中的原油浓度的关系.结果表明,原油浓度与延迟时间呈线性递减关系,反射式太赫兹时域波形是一种具有潜力的污染定量检测方法.     

A Water-Stable Lanthanide Coordination Polymer as Multicenter Platform for Ratiometric Luminescent Sensing Antibiotics

As a hot topic of global concern, the distinguishing and detecting of antibiotic pollution is crucial owing to its adverse effect on ecosystems and human health stemming from excessive use and poor management. Herein, a water-stable lanthanide coordination polymer sensor (Dy-TCPB) with multiple emitting centers is prepared. The versatile Dy-TCPB can conveniently differentiate various antibiotics, and displays a self-calibration luminescent response to nitrofurazone (NFZ) and furazolidone (FZD). Each antibiotic exhibits notable correlation to a unique combination of the two ligand-to-Dy ion emission intensity ratios, enabling two-dimensional fingerprint recognition. Furthermore, the novel self-calibration sensor demonstrates effective recognition of NFZ and FZD with excellent sensitivity and selectivity, and detection limits as low as 0.0476 and 0.0482 μm for NFZ and FZD, respectively. The synthetic approach for the fabrication of a singular coordination polymer exhibiting multiple emissions provides a promising strategy for the development of facile and effective ratiometric sensors.     

A safe minimum standard,the elasticity of substitution,and the cleanup of the Ganges in Varanasi

Despite repeated calls for a thorough cleanup of water pollution in the Ganges river, there are only two papers in the social sciences by Batabyal and Beladi (2017, 2019) that have shed theoretical light on this cleanup problem and its connection to the sustainability of tourism in Varanasi. Hence, we extend the above‐mentioned analyses and focus on two specific questions. First, we introduce the notion of a safe minimum standard (SMS) into the study and show how to analyze a probabilistic model of the Ganges cleanup problem when the SMS is accounted for. Second, for a representative citizen of Varanasi, we study how the magnitude of the elasticity of substitution between a composite consumption good and water quality in the Ganges—modeled by the SMS—affects the tradeoff between consumption and water quality maintenance.     

Approximations of spectra of Schrödinger operators with complex potentials on ℝd

We study spectral approximations of Schrödinger operators T = ?Δ+Q with complex potentials on Ω = ?^d, or exterior domains Ω??^d, by domain truncation. Our weak assumptions cover wide classes of potentials Q for which T has discrete spectrum, of approximating domains Ω_n, and of boundary conditions on ?Ω_n such as mixed Dirichlet/Robin type. In particular, Re Q need not be bounded from below and Q may be singular. We prove generalized norm resolvent convergence and spectral exactness, i.e. approximation of all eigenvalues of T by those of the truncated operators T_n without spectral pollution. Moreover, we estimate the eigenvalue convergence rate and prove convergence of pseudospectra. Numerical computations for several examples, such as complex harmonic and cubic oscillators for d = 1,2,3, illustrate our results.     

我国环境污染与居民恶性肿瘤发病及死亡的灰色关联度分析

收集2003-2012年三个区域:全国区域、城市区域、农村区域的恶性肿瘤发病及死亡率和污染物数据,采用灰色关联分析方法计算了不同区域与不同污染物的综合关联度,并对污染物致恶性肿瘤死亡的潜伏期作了定量分析.研究结果表明:1)氨氮排放量和二氧化硫对我国三个不同区域居民恶性肿瘤发病和死亡率的影响最大;2)污染物与恶性肿瘤发病率的关联度跟区域无关,但是污染物与恶性肿瘤死亡率的关联度城市明显大于农村,污染物与恶性肿瘤死亡率的关联度男性明显大于女性;3)氨氮和二氧化硫导致居民恶性肿瘤死亡的潜伏期分别为:2和1年.     

Recycling of polyethylene terephthalate (PET Or PETE) plastics – An alternative to obtain value added products: A review

Waste management is become one of the world's most pressing issues. Plastic is one of the most widely utilised materials in the modern world. Plastic manufacturing and usage have risen globally in recent decades due to its low weight and outstanding mechanical properties. Plastic has a wide range of applications due to such good properties include lightweight, high strength, and extended durability. Because of plastics are non- or low-biodegradable, a vast quantity of plastic waste is generated every day, making waste disposal the most pressing matter globally. Furthermore, improper waste disposal pollutes the environment. An ecologically friendly approach is necessary to locket these issues. One of the solutions is to recycle this sort of garbage. There are many plastic recycling technologies available, however practically all of them have certain restrictions. Chemical recycling of plastic, on the other hand, has been shown to be more efficient than other recycling methods. This article provides a quick overview of chemical recycling of PET post-consumer waste and the synthesis of potentially value-added products such as dye or dyestuffs, bolaform surfactant, bio-degradable polyesters, drug carrier, Metal-organic framework (MOF), bio-degradable polymeric scaffolds, polyurethane foam and coating materials etc.     

改性生物炭对废水中锑的去除研究进展

废水锑排放限值日趋严格,迫切需要高效低成本的废水锑去除技术。本文介绍了含锑废水较为成熟的处理技术和工艺,然后结合生物炭的制备和特点综述了改性生物炭技术应用于废水中锑的去除治理所具有的明显优势和现阶段所取得的研究成果,为改性生物炭技术用于废水中锑的去除应用和推广提供一定的参考。     

西南山地煤矿区耕地土壤-农作物重金属富集及健康风险评价

为了解西南某典型山地煤矿区周边农田土壤、农作物重金属的富集情况及对当地人群健康的影响程度,采集矿区周边农田土壤样品和对应的农作物样品,测定重金属Cr、Mn、Zn、As、Pb的含量。运用Nemero指数法、潜在风险指数法对土壤重金属的污染程度进行评价;采用靶标危害系数法(THQ)评价农作物重金属对人体的健康风险。结果显示,Cr、Mn、Zn、As、Pb分别是背景值的1.81、1.90、2.89、1.30、0.86倍,处于轻度污染级别,轻微危害程度。农作物重金属Cr、Pb和As含量的超标情况较严重,Zn的含量超标相对较小。各农作物富集的重金属对人体的健康风险大小为：高粱>玉米>白菜>葱>辣椒。农作物重金属对儿童健康的危害均达到了慢性中毒;对成人健康的影响,高粱处于慢性中毒,其它农作物重金属处于产生较大影响的危害程度。农作物重金属与土壤重金属的相关性分析表明,农作物重金属的含量与土壤重金属全量并无线性关系;各重金属在农作物中的转移能力不同;Pb,As在农作物中的转移能力较大,而Cr相对较小。鉴于矿区重金属的富集情况,应尽快采取修复治理措施,为保证当地人群健康,建议当地居民不再食用和种植富集重金属严重的高粱、玉米农作物。     

Supercritical Carbon Dioxide-Based Processes in Photocatalytic Applications

Conventional methods generally used to synthesize heterogeneous photocatalysts have some drawbacks, mainly the difficult control/preservation of catalysts’ morphology, size or structure, which strongly affect the photocatalytic activity. Supercritical carbon dioxide (scCO₂)-assisted techniques have recently been shown to be a promising approach to overcome these limitations, which are still a challenge. In addition, compared to traditional methods, these innovative techniques permit the synthesis of high-performance photocatalysts by reducing the use of toxic and polluting solvents and, consequently, the environmental impact of long-term catalyst preparation. Specifically, the versatility of scCO₂ allows to prepare catalysts with different structures (e.g., nanoparticles or metal-loaded supports) by several supercritical processes for the photocatalytic degradation of various compounds. This is the first updated review on the use of scCO₂-assisted techniques for photocatalytic applications. We hope this review provides useful information on different approaches and future perspectives.