Search

Contamination of leafy vegetables grown in heavy metal(loid)-polluted mining areas pose serious health risks. This study aimed to explore the heavy metal(loid) contamination of leafy vegetables near two mining areas, by collecting samples from 14 different leafy vegetable species in Yunnan Province, China. The lead (Pb), cadmium (Cd), arsenic (As), and copper (Cu) contents of the samples were determined, and risks to human health were calculated using the hazard quotient and hazard index (HI). Moreover, Malabar spinach was identified as a leafy vegetable that exhibits low accumulation of heavy metal(loid)s. The accumulation capacity of different Malabar spinach varieties was verified, and a Cd soil safety threshold was determined using a pot experiment. Overall, Pb and Cd were the main soil and vegetable contaminants found in both study sites. The HI values for all leafy vegetables, apart from Malabar spinach, were greater than 1, indicating the presence of risks to human health; moreover, the health risks were greater for children than adults. The Malabar spinach pot experiment results showed that only some Cd forms exceeded China's maximum permissible standards. Furthermore, Malabar spinach varieties A (instant Malabar spinach), C (extra-large leaf green vine Malabar spinach), and F (large leaf Malabar spinach) displayed the lowest Cd accumulation. We calculated Cd total and bioavailable soil safety thresholds of 4.75 and 0.77 mg kg-1, respectively. However, further research is required to validate soil heavy metal safety thresholds for different vegetables. Ultimately, the heavy metal(loid) contamination of leafy vegetables described here was more serious than anticipated. Finally, the results of this study can inform residents living near these mining areas of a low-risk leafy vegetable, which will reduce the harm caused by heavy metal(loid) contamination in the area. [ABSTRACT FROM AUTHOR]

Purpose: The purposes of this study were to quantify the resource consumption intensity of cement clinker production using natural mineral in China and to determine the influence of the utilization of calcium carbide sludge (CCS) for cement clinker production on the resource-accounting result. Methods: Exergy-based resource accounting method was adopted by this study. Cumulative exergy demand (CExD) was used to characterize the resource consumption intensity of cement clinker production using natural mineral in China. Exergy-based characterization factors of land resource and CO2 emission were employed to determine the resource benefit brought by the substitution of CCS for natural limestone (land saving and CO2 reduction). Results and discussion: The CExD value of cement clinker production using natural mineral as raw material in China is 5005 MJ/t, and the consumption of raw coal is the largest contributor to this result, accounting for approximately 81% of the CExD value. The phenomenon that coal consumption dominates the CExD result may be because, through combustion reactions, the chemical state of carbon contained in coal almost reaches equilibrium with its chemical dead state in terms of exergy and is deeply dissipated; in comparison, the major chemical compound contained in limestone, i.e., calcium oxide, is mostly transformed into cement clinker by the reactions occurred in the production system, instead of being consumed in a deeply dissipated way and emitted to the environment. The major disadvantage of using CCS for cement clinker production is the increase of coal consumption, i.e., 515 MJ/t cement clinker, and the major advantage of using CCS for cement clinker production is the resource benefit brought by CO2 reduction (the avoided biotic resource damage in ecosystem), i.e., 1160 MJ/t cement clinker. Conclusions: From the analysis on the influence of the substitution of CCS for limestone on the resource consumption intensity, we found that the resource consumption intensity of the production system using CCS is approximately 15.5% lower than that of the production system using natural mineral; however, if this resource benefit is neglected, the resource consumption intensity of the production system using CCS is approximately 7.6% higher than that of the production system using natural mineral. We suggest that establishing a theoretical bridge between the characterization models of biotic resource and abiotic resource will still be a significant research direction in the future, which is fundamental in objectively understanding and unifying the issues of emission reduction and resource saving. [ABSTRACT FROM AUTHOR]

Purpose: Cement production is associated with a considerable environmental load, which needs to be fully understood before effective measures can be taken. The existing literature did not give detailed life cycle assessment (LCA) study of China and had limited potential for investigating how best available techniques (BATs) would provide a maximum benefit when they are applied in China. Japan was selected as a good example to achieve better environmental performance of cement production. We identified potentials for reducing emissions and saving energy and natural resources in Chinese cement industry through the comparative analysis. Methods: This paper follows the principal of Life Cycle Assessment and International Reference Life Cycle Data System ( ILCD). The functional units are '1 t of portland cement' and with 42.5 MPa of strength grade. The input (limestone, sandstone, ferrous tailings, coal, and electricity) and output (CO from limestone decomposition and coal combustion, NOx, PM, and SO) of cement manufacturing were calculated by use of on-site measurements, calculation by estimated coefficients, and derivation by mass and heat balance principle. The direct (cement manufacturing) and indirect (electricity production) LCI are added to be total LCI results (cement production). The impact categories of global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), photochemical oxidant formation potential (POCP), and human toxicity potential (HTP) are used to calculate environmental impact. Results and discussion: Only in GWP of cement manufacturing China has advantage. Japanese cement industry shows remarkable superiorities in the environmental impacts of AP, POCP, HTP, and EP due to advanced technologies. SO emissions make the corresponding AP and HTP. PM emissions result in part of HTP. The NOx emissions are the major contributors of POCP, AP, EP, and HTP in China. China emits fewer CO emissions (2.09 %) in cement manufacturing than Japan but finally makes higher total GWP than Japan due to more GWP of electricity generation in power stations. The waste heat recovery technology can save electricity but bring more coal use and CO emissions. The alternative fuel and raw materials usage and denitration and de-dust technologies can relieve the environmental load. Using the functional unit with the strength grade, the life cycle impact assessment (LCIA) results are affected. Conclusions: LCA study allows a clear understanding from the view of total environmental impact rather than by the gross domestic product (GDP) unit from an economic development perspective. In an LCA study, the power generation should be considered in the life cycle of cement production. [ABSTRACT FROM AUTHOR]

Abstract: To make clear the environmental damages and potential improvements of Chinese cement industry, the detailed life cycle inventory (LCI) of cement manufacture with direct input and output in the boundary of cement plant as well as corresponded transport is conducted. The functional units are 1 t of Portland Ordinary cement and 1 t of clinker. The input data contain not only the traditional items such as raw materials (limestone, sandstone, ferrous tailings and gypsums), energy (coal and electricity), and admixtures (fly ash and furnace slag), but also fresh water which is not paid attention in other literature. The output data contain not only greenhouse gas (CO2) and primary pollution (NO x , PM, SO2), but also the hazardous air pollutants (HCl, NMVOC, PCDD/Fs, PAHs and fluoride) as well as noise and heavy metal emissions (As, Cd, Cr, Hg, Ni, Pb, Zn, Cu) which are usually neglected by others. The data were measured on-site. The applications of reducing pollutants and waste heat recovery technologies, and AFRs usage in cement industry are evaluated. The three steps of developments of LCI study for China cement industry are discussed. [Copyright &y& Elsevier]

China was positioned as the world's largest producer and consumer of ceramic tiles, accounting for 50% of tile production and 40% of tile consumption in the world approximately. Recently, Chinese ceramic industry has increased its focus on environmental issues with the aim of protecting natural resources and reducing pollutant emission. This study evaluated and compared the environmental impacts of ceramic tiles produced by traditional technology and cleaner production technology using life cycle assessment methodology with "cradle to gate" perspective. The results showed that the energy consumptions and emissions from fuel combustion were the hotspots of the environmental impact caused by tile production. The drying and firing processes were the main contributors to the energy consumption at the ceramic production stage. Moreover, the environmental impact reduction potential of different cleaner production technologies was elaborated in this paper. The results proved that applying natural gas as fuel instead of coal (producer gas) caused less damage on human health and ecosystem but more damage on the resource. The dry-milling process has potential to reduce environmental impacts compared with wet-milling process in all midpoint and endpoint indicators. In addition, the sensitivity analysis of input parameters, transportation distance and qualified products rate was conducted to identify the key parameters that have great influence on the results. • Ceramic products from four typical plants in China was analyzed using LCA. • Environmental impact of different fuel scenarios and milling technologies was compared. • Applying the natural gas as fuel instead of coal (producer gas) caused less damage on human health and ecosystem. • Dry-milling process have potential to reduce the environmental impact compared with wet-milling process. • Sensitivity analysis related to input parameter, transport distance and qualified products rate were conducted. [ABSTRACT FROM AUTHOR]