In this study, we investigated cadmium toxicity created by adsorption kinetics in several mixtures containing two types of multi-walled carbon nanotubes (COOH-MWCNT and NH2-MWCNT) and natural kaolinite. Characteristics of two types of MWCNTs were measured by zeta potential and ATR FT-IR graphs and TEM images. The solution of CNTs and kaolinite was tested to study Cd adsorption kinetics and mechanisms of differentiation-associated toxicity using Daphnia magna in a binary system (Cd–MWCNTs and Cd–kaolinite) and a ternary system (Cd–MWCNTs–kaolinite). In the binary system, Cd removal efficiency was nearly 100% and 40% for MWCNTs and kaolinite because of surface charge, respectively, with increasing sorbent concentration. In the ternary system, the trend of adsorption rate was similar to that of binary system. In comparison with percent mortality in the binary system, the solution in the ternary system showed higher toxicity due to the interaction of MWCNTs–kaolinite coagulated particles, thereby decreasing Cd adsorption onto CNTs and kaolinites. Overall, kaolinite can affect the adsorption process of Cd on MWCNTs in negative ways, depending on adsorption state. In conclusion, our studies suggest that kaolinite differs with adsorption ability of Cd by MWCNTs, and toxicity is likely to be produced by multivariable regression in the adsorption state.
Environmental Fluid Mechanics - This study implemented three analytical models to investigate the lateral distribution of depth-averaged streamwise velocity in a rectangular channel with lateral,... 相似文献
This paper reports findings of a qualitative study conducted in collaboration with Aboriginal people with disabilities and their carers residing in the rural and remote Kimberley region of Western Australia, specifically the impact of chronic food insecurity on their daily lives. Nutritious food is important to maintaining health, particularly for Aboriginal people with disabilities who are at the greatest risk of a range of chronic health conditions, illnesses and secondary disability. In the remote areas of the West Kimberley, the high cost of living, including food expenses and the generally low incomes of residents mean that food insecurity is common. A large portion of the population living in remote and rural areas of the Kimberley is Aboriginal, and chronic illness and disability are twice as likely among this group. Lack of access to nutritious food has a cyclical interaction with disability, resulting in secondary impairments and ill health, which leads to greater economic exclusion and further food insecurity. Participants in this research consistently reported that they coped with food insecurity by fishing and crabbing on their traditional lands, “in country”. This link between land sovereignty, food sovereignty and food security for Aboriginal Australians has echoes with global food sovereignty movements. 相似文献
Social insect colonies need to explore and exploit multiple food sources simultaneously and efficiently. At the individual
level, this colony-level behaviour has been thought to be taken care of by two types of individual: scouts that independently
search for food, and recruits that are directed by nest mates to a food source. However, recent analyses show that this strict
division of labour between scouts and recruits is untenable. Therefore, a modified concept is presented here that comprises
the possible behavioural states of an individual forager (novice forager, scout, recruit, employed forager, unemployed experienced
forager, inspector and reactivated forager) and the transitions between them. The available empirical data are reviewed in
the light of both the old and the new concept, and probabilities for the different transitions are derived for the case of
the honey-bee. The modified concept distinguishes three types of foragers that may be involved in the exploration behaviour
of the colony: novice bees that become scouts, unemployed experienced bees that scout, and lost recruits, i.e. bees that discover
a food source other than the one to which they were directed to by their nest mates. An advantage of the modified concept
is that it allows for a better comparison of studies investigating the different roles performed by social insect foragers
during their individual foraging histories.
Received: 29 December 1999 / Revised: 25 February 2000 / Accepted: 16 October 2000 相似文献
The coupling relation exists in water and soil conservation and economic-social development. The article analyses the relation of soil and water conservation and economic-social development stages as well as the coupling analytical method. Then calculates the expecting income by dispersing Markov decision and calculates the correlation coefficient and the relationship degree. The article obtains the relationship of soil and water conservation investments and all kinds of incomes. Finally, it analyzes the important meaning in socio-economic development of water and soil conservation. 相似文献
The level and extent of organic contaminants along the Korean coast were estimated through the mussel watch program, established in 2001. Mussels and oysters were collected at 20 sites along the Korean coast in 2001 and at 25 sites from 2002 to 2007. The mussel tissues were analyzed for PCBs, organochlorine presticides, PAHs, BTs, and PCDD/Fs. PCBs, PAHs, BTs, and PCDD/Fs were ubiquitous contaminants along the Korean coast, showing mean detection frequencies of more than 95% over 7 years. The concentrations of organic contaminants in mussels along the Korean coast were relatively low or moderate compared with foreign studies. Concentrations of DDTs, PCBs, and PCDD/Fs were below the action or maximum levels for humans established by USFDA and EU. Elevated concentrations above the 85th percentile were found for PCBs, PAHs, BTs, and PCDD/Fs at sites near industrial complexes or big harbors, for HCHs at sites near non-industrial complexes, and for DDTs at sites near both non-industrial and industrial complexes. Using two nonparametric tests to assess temporal trends, the Spearman test revealed that BTs and PCDD/Fs had significant decreasing trends at four sites (Gwangyang Bay, Cheonsu Bay, Garorym Bay, and the Incheon coast) and at six sites (Hupo coast, Guryongpo coast, eastern part of Geojedo, Gunsan coast, Garorym Bay, and Asan Bay), respectively. 相似文献
Over-stabilisation and eutrophication affect many dune systems in north-west Europe. This leads to lower diversity of typical
dune species and an accumulation of soil nutrients. Existing management techniques to remove excess nutrients include mowing,
with removal of cuttings, and turf stripping. A new restoration technique called topsoil inversion or deep ploughing may also
be able to counter some of the negative effects of eutrophication. It simulates the burial of established soils with fresh
mineral sand, by inverting the soil profile. A trial was carried out on two small blocks of eutrophic dune grassland in North
Wales, UK. Nutrient-rich surface soils were buried beneath mineral sub-sand using a double-bladed plough, designed to plough
to depths of up to 100 cm. Results show that the organic soil horizons were buried to a depth of 80 cm, and covered with 40–50 cm
of mineral sand. The pH and organic matter of the surface layers became comparable to those of mobile dunes. Fifteen months
after ploughing, bare sand cover was still 70–90%, but significant sand loss through wind erosion resulted in a thinning of
the mineral sand over-burden, leaving the buried organic layer closer to the surface. Natural vegetation colonisation was
slow, with the first surviving plants observed after 8 months. The majority of species present at 15 months were present before
ploughing and had regenerated from rhizomes or root fragments. The effect of excluding disturbance caused by rabbits, people
and dogs was assessed within fenced areas. After 11 months, vegetation cover was greater in the fenced areas than in plots
exposed to disturbance, therefore disturbance replaced physical conditions as the dominant influence on plant growth and establishment.
These early results suggest the trial has been partially successful, but that topsoil inversion could be combined with other
methods such as turf stripping or by stabilisation of the ploughed surface by planting with pioneer species, depending on
the ultimate restoration goal. 相似文献
The purpose of this study is to investigate the enhancement of polycaprolactone (PCL) on total nitrogen (TN) removal of coal pyrolysis wastewater (CPW) with low COD to nitrogen ratio by partial nitrification-denitrification bioprocess (PNDB) in one single reactor. With the innovative combination of PCL and PNDB, the TN removal efficiency in the experimental reactor (signed as R1) was 10.21% higher than control reactor (R2). Nitrite accumulation percentage (NAP) in R1 was 82.02%, which was 17.49% higher than R2 at the dissolved oxygen (DO) concentration of 0.9–1.5 mg/L, for the reason that the extra DO was consumed by PCL biodegradation at the aerobic period. Gel permeation chromatography (GPC) results demonstrated that organics with the molecular weight of 185 Da, which could serve as additional carbon sources for denitrifiers, were generated during the PCL hydrolysis process at the anoxic period. PCL was hydrolyzed by extracellular enzymes with the break of the ester bond which was confirmed by FT-IR spectrometer. Microbial community analysis revealed that Ferruginibacter was the dominant hydrolysis bacteria in R1. Nitrosomonas were the main ammonium-oxidizing bacteria (AOB) and Hyphomicrobium were the denitrifiers in this study.
ABSTRACT The South Coast Air Quality Management District (SCAQMD) conducted a 1-year special particulate monitoring study from January 1995 to February 1996. This monitoring data indicates that high PM10 and PM2 5 concentrations were observed in the fall (October, November, and December), with November concentrations being the highest. During the rest of the year, PM2.5 and PM10 masses gradually increased from January to September. Monthly PM10 mass varied from 20 to 120 |ig/m3, and monthly PM25 mass varied from 13 to 63 |j.g/m3. The PM2.5-to-PM10 ratio varied daily and ranged between 22 and 96%. Two types of high-PM days were observed. The first type was observed under fall stagnation conditions, which lead to high secondary species concentrations. The second type was observed under high wind conditions, which lead to high primary coarse particles of crustal components. The highest 24-hr average PM10 concentration (226.3 |ig/m3) was observed at the Fontana station, while the highest PM25 concentration (129.3 |ig/m3) was observed at the Diamond Bar station. 相似文献