Distribution and Source of Pb in Urban Topsoil

In the process of industrialization and urbanization, human activities have caused more and more heavy metal lead to enter the surface soil, causing harm to the health of residents. Analysis of the status of lead pollution in urban surface soils in China found that lead pollution in most cities currently exceeds regional background values. The sources of heavy metals in cities mainly include transportation, industrial emissions, and human activities. At present, the methods for determining sources include three methods: multivariate statistical analysis, geographic information systems, and isotope tracing

Research progress and application of photobioreactor in wastewater treatment

The first photobioreactors were born in the 1950s, and photobioreactors based on microalgae have potential applications in the pharmaceutical industry, food and feed production, environmental engineering, wastewater treatment, and renewable energy. Photobioreactors were first used in pollutant treatment for carbon dioxide sequestration in 1953 at the Carnegie Institute in Washington. Photobioreactors use stable and efficient algae cultivation technology to create an artificial environment that provides all necessary conditions for algae growth such as (light, temperature, nutrients), and these conditions can be controlled and monitored, especially for microalgae cultivation, It is convenient for the rapid, stable and controllable growth of microalgae. Currently, there are many types of microalgae-based photobioreactors in terms of configuration, fabrication materials, and operating modes. It can optimize biomass production, improve the efficiency of pollutant removal, reduce cost and improve space advantage. The most common structures for photobioreactors are flat, columnar and tubular, followed by hoses and hybrid photobioreactors, taking their flexibility and efficacy to a higher level. Each photobioreactor type has its own advantages and disadvantages in terms of operation, biomass production, pollutant removal efficiency, and level of upgrade

Basalt fibre continuous reinforcement composite pavement reinforcement design based on finite element model

The thrust of basalt fibre (BFRP) tendons will result in narrower transverse crack spacing, decreased load transfer capacity of transverse cracks and voids at the bottom of the slab, which will lead to thrust failure. The thesis uses the finite element analysis method to analyse the material characteristics of BFRP tendons. At the same time, the article determines the critical load position corresponding to the tensile stress of concrete and BFRP tendons, and analyses the influence of voids, crack spacing and other factors on the load stress of concrete and BFRP tendons. The study results found that continuously reinforced concrete and asphalt overlay composite design can reduce cracks

Influence of Restrainer Piers on the Seismic Performance of Long Bridges with Equal-Height Piers

Pounding may occur between the main girders under the action of strong earthquakes, so as between main girders and abutments. This causes excessive longitudinal displacement of the main girder and unseating damage to bridges. Because long bridges in mountainous areas with high intensity are easy to unseat, the authors studied the influence of restrainer piers, expansion joint spacings (EJSs), and the span on the seismic performance of long bridges. The ABAQUS finite element software was used to simulate a bridge dynamic analysis model considering the elastoplasticity of the pounding effect of the pier and the beam. By inputting El-Centro, Northbridge, and Taft seismic waves, the time-history analysis of the seismic response of long bridges was carried out. The results indicated that a reasonable number of restrainer piers, an appropriate EJS, and a span could effectively reduce the maximum relative displacement of pier-beams. This behavior will improve the seismic performance of bridge structures. Moreover, for a 24-span equal-height beam bridge, the optimum seismic effect was obtained when 3 restrainer piers, an EJS of 70 mm, and a 50 m span were used

Distribution Characteristics of Soil Total Nitrogen in Low-efficiency Forest Land in the Northern Windy Desert Area of Jingbian County

[Objectives]The paper was to investigate the distribution characteristics of soil total nitrogen in low-efficiency forest land in the northern windy desert area of Jingbian County. [Methods]The distribution of soil total nitrogen in the 0-40 cm soil layer of 5 towns in the northern windy desert area of Jingbian County was studied through field sampling and laboratory detection. [Results]The average soil total nitrogen contents of Hongdunjie Town, Haizetan Town, Huanghaojie Town, Ningtiaoliang Town, Dongkeng Town and windy desert area in the 0-20cm soil layer were 0.259, 0.224, 0.242, 0.248, 0.431 and 0.275 g/kg, respectively. The soil total nitrogen content in Dongkeng Town was higher than those in other towns, while there was little difference among other regions. The average total nitrogen contents in the 20-40cm soil layer were 0.239, 0.285, 0.113, 0.262, 0.349 and 0.241 g/kg, respectively. The soil total nitrogen content in Huanghaojie Town was slightly lower than those in other towns, while that in Dongkeng town was higher. The variation coefficient of soil total nitrogen content in the survey area was greater than 30%, and there was great difference in spatial distribution. With the increase of soil depth, there was little change in soil total nitrogen content, namely the soil total nitrogen contents in 5 towns and windy desert area were not statistically different in the 0-40 cm soil layer. According to the nutrient grading standard of the second national soil survey, the soil total nitrogen content in the survey area was in the deficiency grade. [Conclusions]The research will provide a scientific guidance for the healthy and sustainable development of vegetation in arid regions

Distribution Characteristics of Soil Total Nitrogen in Low-efficiency Forest Land in the Northern Windy Desert Area of Jingbian County

[Objectives]The paper was to investigate the distribution characteristics of soil total nitrogen in low-efficiency forest land in the northern windy desert area of Jingbian County. [Methods]The distribution of soil total nitrogen in the 0-40 cm soil layer of 5 towns in the northern windy desert area of Jingbian County was studied through field sampling and laboratory detection. [Results]The average soil total nitrogen contents of Hongdunjie Town, Haizetan Town, Huanghaojie Town, Ningtiaoliang Town, Dongkeng Town and windy desert area in the 0-20cm soil layer were 0.259, 0.224, 0.242, 0.248, 0.431 and 0.275 g/kg, respectively. The soil total nitrogen content in Dongkeng Town was higher than those in other towns, while there was little difference among other regions. The average total nitrogen contents in the 20-40cm soil layer were 0.239, 0.285, 0.113, 0.262, 0.349 and 0.241 g/kg, respectively. The soil total nitrogen content in Huanghaojie Town was slightly lower than those in other towns, while that in Dongkeng town was higher. The variation coefficient of soil total nitrogen content in the survey area was greater than 30%, and there was great difference in spatial distribution. With the increase of soil depth, there was little change in soil total nitrogen content, namely the soil total nitrogen contents in 5 towns and windy desert area were not statistically different in the 0-40 cm soil layer. According to the nutrient grading standard of the second national soil survey, the soil total nitrogen content in the survey area was in the deficiency grade. [Conclusions]The research will provide a scientific guidance for the healthy and sustainable development of vegetation in arid regions

Analysis of soil fertility and toxic metal characteristics in open-pit mining areas in northern Shaanxi

Abstract The study specifically focused on the Hongliulin mining area, where a total of 40 soil samples were meticulously collected and analyzed from within a 1000 m radius extending from the tailings dam. The findings revealed that soil pH within the 0–1000 m range generally leaned towards the alkaline side. In terms of soil nutrient content, encompassing factors such as soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali nitrogen (AK), available phosphorus (AP), and quick-acting potassium (AK), the variations fell within the following ranges: 2.23–13.58 g/kg, 0.12–0.73 g/kg, 0.18–1.15 g/kg, 9.54–35.82 g/kg, 2.89–6.76 mg/kg, 3.45–11.25 mg/kg, and 5.86–130.9 mg/kg. Collectively, these values indicate relatively low levels of soil nutrients. Within the 0–500 m range of soil samples, the average concentrations of Cd, Hg, Pb, and As were 0.778, 0.198, 24.87, and 17.92 mg/kg, respectively. These concentrations exceeded the established soil background values of Shaanxi Province and emerged as the primary pollutants in the study area. Within this same range, the mean values of eight toxic metals (Pi) were ranked in the following descending order: 1.726 (Hg), 1.400 (As), 1.129 (Cr), 1.109 (Pb), 0.623 (Zn), 0.536 (Cd), 0.309 (Cu), and 0.289 (Ni). With the exception of Hg, As, Cr, and Pb, which exhibited slight pollution, the other toxic metals were found to be within acceptable pollution limits for this sampling range, in line with the results obtained using the geo-accumulation index method. The average potential ecological risk index for the eight toxic metals in the study area stood at 185.0, indicating a moderate overall pollution level. When assessing individual elements, the proportions of ecological risk attributed to Hg, As, Pb, and Cd were 34.57%, 27.44%, 25.11%, and 23.11%, respectively. This suggests that the primary potential ecological risk elements in the study area are Hg and As, followed by Cd and Pb. Notably, toxic metals Hg and Pb, as well as As and Pb, exhibited significant positive correlations within the sampling area, suggesting a common source. An analysis of the relationship between soil physicochemical properties and toxic metals indicated that soil pH, SOM, TN, and TP were closely linked to toxic metal concentrations. The toxic metal elements in the research area's soil exhibit moderate variability (0.16  0.36). Within the range of 0–200 m, the CV values for Cd and Hg exceed 1, indicating a high level of variability. The coefficient of variation for SOM, TP, AP, AK and TK is relatively high with the of 2.93, 2.36, 2.36, 21.01, 7.54. The soil in the sampling area has undergone significant disturbances due to human activities, resulting in toxic metal pollution and nutrient deficiencies

Application of NMR logging while drilling in fluid identification of low resistivity reservoirs in Wenchang Oilfield, South China Sea

In the development of low resistivity reservoirs in Wenchang Oilfield of South China Sea, NMR logging while drilling provides porosity, permeability and other parameters in a safe and efficient logging way, and plays a key role in qualitative identification of light oil. In order to further improve the application value of NMR logging while drilling in fluid identification of low resistivity reservoir in Wenchang Oilfield, starting from two influencing factors which is pore structure and fluid properties, T2 spectrum oil-bearing characteristic index was proposed, and pure water spectrum reconstruction was introduced to carry out fluid quantitative identification. The T2 spectrum oil-bearing characteristics index method was based on eliminating the influence of pore structure, and by using the transverse relaxation time difference between light oil and water to extract the real tail phenomenon of light oil, so as to achieve the purpose of quantitative identification of fluid.The water spectrum reconstruction method used the spherical tube model and the normal distribution model to construct the bound water spectrum and the movable water spectrum respectively, which the sum of the two spectrum is pure water spectrum. The information of fluid properties is extracted by comparing with the actual measured NMR T2 spectrum, so as to identify the fluid properties. The two methods have good applications to the fluid identification of low resistivity reservoirs in Wenchang Oilfield.These two methods can play important roles in the quantitative identification of reservoir fluids such as low resistivity reservoirs and water flooded reservoirs