2017年1月—12月期间在四川省宜宾市布置4个点位,共采集360个PM_(2.5)样品膜,采用美国沙漠研究所DRI Model 2001型热光分析仪测定PM_(2.5)样品中OC、EC的浓度值,应用OC/EC比值法对SOC进行了估算.结果表明,宜宾市PM_(2.5)年均浓度为75.2μg·m~(-3).OC、EC年均浓度分别为14.3μg·m~(-3)和4.30μg·m~(-3),季节变化趋势为冬季秋季春季夏季,OC占PM_(2.5)比例为19.0%,为PM_(2.5)重要组成部分.SOC年均浓度为4.70μg·m~(-3),对OC贡献较大,在OC中占比为29.3%;SOC在OC中的占比春季冬季≈秋季夏季.进一步对OC1、OC2、OC3、OC4、EC1、EC2、EC3、和OPC进行主成分分析,结果表明机动车尾气、燃煤排放和生物质燃烧是宜宾市PM_(2.5)中OC和EC的主要贡献源,可贡献PM_(2.5)中碳组分的54.0%—69.0%. 相似文献
In order to assess the intake of lead and cadmium by consumers of home grown vegetables in urban areas, replicated experimental plots of uniform size, comprising summer and winter crops, were established in 94 gardens and allotments in nine towns and cities in England.The geometric mean lead and cadmium concentrations for the soils (n = 94) were 217 g g–1 (ranging from 27 to 1,676 g g–1) and 0.53 g g–1 (<0.2–5.9 g g–1), respectively. Compared with agricultural soils, the garden and allotment soils contained elevated levels of lead but not cadmium.Lead concentrations in the vegetables ranged from <0.25 g g–1 to 16.7 g g–1 dry weight and cadmium concentrations ranged from <0.025 g g–1 to 10.4 g g–1 dry weight. Lead concentrations were higher than reported background levels, although <1% exceeded the statutory limit for saleable food in the UK (1 g g–1 fresh weight). Cadmium concentrations were generally similar to background levels. 相似文献
The food and agriculture sector controls the economic growth of a developing country. The food industries have practices of growing crops, raising livestock and sea foods, food processing and packaging, regulating production and distribution with quality and safety. The process control and monitoring quality are crucial steps. Here we review nanosensors and nanobiosensors as alternative of classical quantification methods. Nanoscale dimensions of metal nanoparticles, metal nanoclusters, metal oxide nanoparticles, metal and carbon quantum dots, graphene, carbon nanotubes, and nanocomposites expand the sensitivity by signal amplification and integrate several novel transduction principles such as enhanced electrochemical, optical, Raman, enhanced catalytic activity, and superparamagnetic properties into the nanosensors. The electrochemical nanosensors, optical nanosensors, electronic nose and electronic tongue, nanobarcode technology, and wireless nanosensors have revolutionized the sensing in food and agriculture sectors with multiplex and real-time sensing capabilities. Despite previous success stories of the remunerative health sector, the approaches are transferred subsequently to food and agriculture sector; with potential application in detection of food contaminants such as preservatives, antibiotics, heavy metal ions, toxins, microbial load, and pathogens along with the rapid monitoring of temperature, traceability, humidity, gas, and aroma of the food stuff. 相似文献
Six wastewater treatment plants （WWTPs） were investigated to evaluate the occurrence and removal of N-nitrosodimethylamine （NDMA）, NDMA formation potential （FP） and four specific NDMA precursors, dimethylamine （DMA）, trimethylamine （TMA）, dimethyl- formamide （DMFA） and dimethylaminobenzene （DMAB）. DMA and tertiary amines with DMA functional group commonly existed in municipal wastewater. Chemically enhanced primary process （CEPP） had no effect on removal of either NDMA or NDMA FP. In WWTPs with secondary treatment processes, considerable variability was observed in the removal of NDMA （19%-85%） and NDMA FP （16%-76%）, moreover, there was no definite relationship between the removal of NDMA and NDMA FP. DMA was well removed in all the six surveyed WWTPs; its removal efficiency was greater than 97%. For the removal of tertiary amines, biologic treatment processes with nitrification and denitrification had better removal efficiency than conventional activated sludge process. The best removal efficiencies for TMA, DMFA and DMAB were 95%, 68% and 72%, respectively. CEPP could remove 73% of TMA, 23% of DMFA and 36% of DMAB. After UV disinfection, only 17% of NDMA was removed due to low dosage of UV was applied in WWTP. Although chlorination could reduce NDMA precursors, NDMA concentration was actually increased after chlorination. 相似文献
Pharmaceuticals and personal care products (PPCPs) have been regarded as an emerging problem in the surface water environment in the past few decades. In China, although related studies were initiated several years ago, an increasing number of studies on this topic have been conducted in recent years. These studies have expanded knowledge of their occurrence, behavior and associated risk in the surface water environment in China. This review compiles the most recent literature related to the studies of PPCPs in the surface water environment in China. It includes PPCP occurrence in surface water and sediments, their geographical distribution, and outcomes of the associated risk assessment. It shows that antibiotics have received much more attention in both surface water and sediments than other PPCPs. Compared to other countries; most antibiotics in the collected sediments in China showed higher contamination levels. Many more study areas have been covered in recent years; however, attention has been given to only specific areas. Environmental risk assessment based on risk quotients indicated that sulfamethoxazole presents the most significant environmental risk to relevant aquatic organisms; followed by ofloxacin, ciprofloxacin, enrofloxacin, 17α-ethynylestradiol, ibuprofen and diclofenac. Despite limited research on the environmental risk assessment of PPCPs in sediments, higher risks posed by PPCPs in the sediments rather than surface water were identified highlighting the need for further risk assessment of PPCPs in sediment samples.
Sequential extraction has been used as a suitable method for fractionation of chemical forms of trace elements and study of
their plant availability. Surface soils were sampled from Guilan and Hamadan provinces in north and northwest of Iran with
temperate and semiarid climates. The chemical forms of Pb in the Pb(NO3)2-treated (400 μg Pb g−1) soils have been studied in solid state incubation (FC) at 27°C in sterile and unsterile conditions. After 20 min and 3600 h
a sequential extraction scheme was also used to fractionate Pb of incubated samples into soluble-exchangeable (Sol-Exch),
carbonates associated (ACar), organic matter associated (AOM), Mn oxide associated (AMnOx), Fe oxide associated (AFeOx), and
residual (Res) forms. Temperate soil samples had higher clay content, cation exchange capacity (CEC), dichromate oxidable
organic carbon (OC), total Kjeldahl-nitrogen (TN), biological activity, amorphous and crystalline Fe and Al, but semiarid
soil samples had higher sand content, pH, equivalent calcium carbonate (ECC), available P and K. Soil lead fractionation revealed
that in both groups of soils Pb largely changed to exchangeable, carbonates associated and organic associated forms after
20 min. The chemical forms of Pb differed widely among soils after 3600-h incubation. The conversion rate of Pb from more
available forms to less available forms was higher in temperate soils with higher Fe–Mn oxides and OM contents compared to
semiarid soils. In temperate soils after 3600-h incubation, greater content of Pb was observed in Res (68%), AOM (14%), ACar
(7%), and AMnOx (5%) fractions. However, in semiarid soils greater content of Pb was observed in Res (61%), ACar (16%), Sol-Exch
(8%), and AOM (8%) fractions. The sum of AMnOx and AFeOx chemical forms for Pb in semiarid soils compared to temperate soils
was lower. It was only 7% against 9% in temperate soils. Soil microorganisms in unsterile soils had significant effect on
AOM, AFeOx and Res fractions of Pb. They not only increased AOM and AFeOx fractions of Pb in soils but also decreased Res
fraction of Pb significantly. 相似文献
The results presented here were obtained at six locations during three cruises in 1985 (off the coast of Labrador), 1986 (at the eastern end of Viscount Melbourne Sound) and 1988 (off the coast of Labrador). In situ chlorophyll maximum concentrations were >7 gl-1 at depths of between 0 and 30 m in all sampling areas. In feeding experiments copepods attained higher gut pigment concentrations the longer they had been previously starved and higher concentrations when fed in the dark than when fed in the light. Community ingestion rates calculated from changes in particulate chlorophyll were higher than estimates derived from gut pigment data except when copepods had been starved for 24 h. Differences between estimates by the two methods suggested pigment destruction. In feeding experiments pigment: biogenic silica ratios in food and faecal pellets suggested that the length of starvation period affected the degree of pigment destruction differently at different stations and that feeding in the light greatly increased pigment destruction. A comparison of pigment: silica ratios in the water column, and in faecal pellets collected from copepods which had fed there, suggested that pigment destruction may occur in situ sometimes and that the degree to which it occurs may be affected by feeding history, light, diel feeding behaviour and species composition. 相似文献
