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1.
The geochemical characteristics of arsenic in the soil of the Western Hunan mining area of P.R. China were systematically
studied. The results show that the strata of Western Hunan are rich in arsenic and that Western Hunan is a geochemically abnormal
region for arsenic. The experimental study on speciation in the strata also indicates that the speciation of arsenic in the
Neoproterozoic-Cambrian strata are mainly easily transferred speciation (exchangeable, carbonate-bound, sulfides-bound), which
are approaching or exceed 60%. Arsenic content in the main soil of Western Hunan is in the range of 8.8–22.8 μg g−1, the mean value is 16.1 μg g−1, which is larger than the arsenic background value of Hunan soil. The distribution of rock with high arsenic content or high
easily transferred arsenic speciation is consistent with the distribution of high arsenic content soil. In the mining region,
part soils and river/brook waters were polluted by mine tailings and mining/smelting waste water. The arsenic content in polluted
paddy soils and river/brook water is 46.26–496.19 μg g−1, 0.3–16.5 mgL−1, respectively. The positive abnormality and pollution of arsenic in the soil and water affects the arsenic content of the
crop and the inhabitants’ health. 相似文献
2.
Maria do Socorro S. Pereira Eduardo Winter Jose Roberto Guimarães Susanne Rath Anne Hélène Fostier 《Environmental Chemistry Letters》2007,5(3):137-141
Here, we show a fast and sensitive method for the determination of inorganic arsenic in natural waters using differential
pulse cathodic stripping voltammetry. All the arsenite determinations were done in 2.0 mol L−1 HCl + 3.15 × 10−4 mol L−1 Cu(II) supporting electrolyte. 1 × 10−3 mol L−1 sodium thiosulphate was used as As(V) reducing agent. The detection limit was 0.5 μg L−1 for both species. The method has been applied to water samples collected in an arsenic-contaminated region of Brazil, in
particular, to verify the efficiency of the solar oxidation and removal of arsenic process applied to these waters. 相似文献
3.
Pistón M Silva J Pérez-Zambra R Dol I Knochen M 《Environmental geochemistry and health》2012,34(2):273-278
A multicommutated flow system was designed and evaluated for the determination of total arsenic and selenium by Hydride Generation
Atomic Absorption Spectrometry (HG-AAS). It was applied to the determination of arsenic and selenium in samples of natural
and drinking water. Detection limits were 0.46 and 0.08 μg l−1 for arsenic and selenium, respectively; sampling frequency was 120 samples h−1 for arsenic and 160 samples h−1 for selenium. Linear ranges found were 1.54–10 μg l−1 (R = 0.999) for arsenic and 0.27–27 μg l−1 (R = 0.999) for selenium. Accuracy was evaluated by spiking various water samples and using a reference material. Recoveries
were in the range 95–116%. Analytical precision (s
r
(%), n = 10) was 6% for both elements. Compared with the Standard Methods, APHA, 3114B manual method, the system consumes at least
10 times less sample per determination, and the quantities of acid and reducing agent used are significantly lower with a
reduction in the generation of pollutants and waste. As an additional advantage, the system is very fast, efficient and environmentally
friendly for monitoring total arsenic and selenium levels in waters. 相似文献
4.
This study was carried out to determine the occurrence, prevalence and contributing factors to the incidence of goitre in
Yewa north local government area of Ogun state, southwestern Nigeria. To achieve these objectives, soil, water, and cassava
tubers were collected from four villages – Igbogila, Egua, Sawonjo and Imoto and from Lagos (about 250 m to the ocean) as
a reference location, in order to determine their iodine concentrations. The results of the analyses indicated a soil mean
iodine range of 2.1–5.8 μg g−1; a cassava mean iodine value of 2.3–3.5 μg g−1 and a drinking water mean iodine value of generally <1.0 μg L−1 in all the four villages. These values of iodine in soil and water of the four villages are considered low when compared
with the soil iodine value of 7.4 μg g−1 and water iodine value of 6.1 μg L−1 obtained from Lagos. The limestone unit of the study area remains an inhibiting factor in the bioavailability of the iodine
because of its alkalinity. Statistical analysis has shown that there was significant difference between iodine concentration
in the soils and the drinking water, and a correlation between the soil iodine and organic matter content at p < 0.05. The correlation between soil iodine and granulometric fractions occurred at p < 0.01. Potential goitrogens in the commonly consumed cassava products might also have contributed to the prevalence of goitre
in the study area. Both the females and the adults (i.e., less mobile groups) were found to be vulnerable to goitre development
in these villages. 相似文献
5.
Jasmin Shah M. Rasul Jan Farhat-un-nisa Shehzad Behisht Ara 《Environmental Chemistry Letters》2010,8(3):253-259
A simple spectrophotometric method was developed for determination of trifluralin in commercial formulation and food samples.
The method was based on the hydrolysis of trifluralin with sodium hydroxide to form 2,6-dinitro-4-trifluoromethylaniline.
The resultant aniline group was diazotized with nitrate in acidic media and the diazotized product was coupled with β-naphthol
to form red colored product having λmax 550 nm. The reaction conditions were optimized for hydrolysis as well as for the diazotization reaction. The Beer’s law was obeyed over the range of 0.2–17 μg mL−1 with molar absorptivity of 1.5 × 104 L mol−1 cm−1. The relative standard deviation was found to be 3.6%. A two level factorial design of 23 was used for optimization of all parameters. The influence of different factors and their interactions on the final azo dye
formation were also studied from these factorial designs. The method has been applied successfully for the analysis of commercial
formulations and agricultural samples. The recovery for the determination of trifluralin was found to be in the range 95–97%. 相似文献
6.
An assessment of exposure to mercury in Changchun city has been undertaken. We estimated Hg exposure to members of the general population based on currently available information and our research. We also studied the Hg concentrations in scalp hair of adults. Adults have an estimated intake of all Hg species via all routes of 6.780 μg day−1 (excluding dental amalgam), which equates to an absorbed dose of 1.718 μg day−1. Fish consumption was the most important exposure route (12% of intake, 43% of absorbed dose). Furthermore, air, cereals and vegetables were important exposure routes, and these exposure were estimated for absorbed dosed at 0.296, 0.209 and 0.318 μg day−1, respectively. The mean Hg concentration in hair was 0.448 μg g−1 (range 0.092–10.463 μg g−1). Hg concentration in the hair of males was 0.422 μg g−1 (0.105–2.665 μg g−1), and was 0.474 μg g−1(0.092–10.463 μg g−1) in the hair of females. Neither place of residence nor age had any significant effect on hair Hg concentrations. 相似文献
7.
Patel KS Shrivas K Brandt R Jakubowski N Corns W Hoffmann P 《Environmental geochemistry and health》2005,27(2):131-145
Arsenic contamination in the environment (i.e. surface, well and tube-well water, soil, sediment and rice samples) of central
India (i.e. Ambagarh Chauki, Chhattisgarh) is reported. The concentration of the total arsenic in the samples i.e. water (n=64), soil (n=30), sediment (n=27) and rice grain (n=10) were ranged from 15 to 825 μg L−1, 9 to 390 mg kg−1, 19 to 489 mg kg−1 and 0.018 to 0.446 mg kg−1, respectively. In all type of waters, the arsenic levels exceeded the permissible limit, 10 μg L−1. The most toxic and mobile inorganic species i.e. As(III) and As(V) are predominantly present in water of this region. The
soils have relatively higher contents of arsenic and other elements i.e. Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, As, Ga, Zr, Sn, Sb, Pb and U. The mean arsenic contents in soil of this region are much higher than in arsenic soil of
West Bengal and Bangladesh. The lowest level of arsenic in the soil of this region is 3.7 mg kg−1 with median value of 9.5 mg kg−1. The arsenic contents in the sediments are at least 2-folds higher than in the soil. The sources of arsenic contamination
in the soil of this region are expected from the rock weathering as well as the atmospheric deposition. The environmental
samples i.e. water, soil dust, food, etc. are expected the major exposure for the arsenic contamination. The most of people
living in this region are suffering with arsenic borne diseases (i.e. melanosis, keratosis, skin cancer, etc.). 相似文献
8.
Arsenic in groundwaters of the Lower Mekong 总被引:1,自引:0,他引:1
Stanger G Truong TV Ngoc KS Luyen TV Thanh TT 《Environmental geochemistry and health》2005,27(4):341-357
Increasing incidence and awareness of arsenic in many alluvial aquifers of South-east Asia has raised concern over possible
arsenic in the Lower Mekong Basin. Here, we have undertaken new research and reviewed many previous small-scale studies to
provide a comprehensive overview of the status of arsenic in aquifers of Cambodia and the Cuu Long Delta of Vietnam. In general
natural arsenic originates from the Upper Mekong basin, rather than from the local geology, and is widespread in soils at
typical concentrations of between 8 and 16 ppm; (dry weight). Industrial and agricultural arsenic is localised and relatively
unimportant compared to the natural alluvial arsenic. Aquifers most typically contain groundwaters of no more than 10 μg L−1, although scattered anomalous areas of 10 to 30 μg L−1 are also quite common. The most serious, but possibly ephemeral arsenic anomalies, of up to 600 μg L−1, are associated with iron and organic-rich flood-plain sediments subject to very large flood-related fluctuations in water
level, resulting in transient arsenopyrite dissolution under oxidizing conditions. In general, however, high-arsenic groundwaters
result from the competing interaction between sorption and dissolution processes, in which arsenic is only released under
reducing and slightly alkaline conditions. High arsenic groundwaters are found both in shallow water-tables, and in deeper
aquifers of between 100 and 120 m depth. There is no evidence of widespread arsenicosis, but there are serious localised health-hazards,
and some risk of low-level arsenic ingestion through indirect pathways, such as through contaminated rice and aquaculture.
An almost ubiquitous presence of arsenic in soils, together with the likelihood of greatly increased groundwater extraction
in the future, will require continuing caution in water resources development throughout the region. 相似文献
9.
Cadmium accumulation in the female shore crab Carcinus maenas during the moult cycle and ovarian maturation 总被引:2,自引:0,他引:2
The influence of moulting and ovarian maturation on cadmium accumulation in the tissues of female shore crabs Carcinus maenas exposed to 1 mg Cd l−1 in the water was investigated. Cadmium accumulation in all tissues examined was markedly increased in crabs in the postmoult
stages (A and B) compared to crabs in all other moult stages. During the moult cycle, average cadmium accumulation in the
midgut gland ranged from 29 μg Cd g−1 dw at premoult stage (D2) to 589 μg Cd g−1 dw at postmoult stage (A). Average cadmium concentrations in the haemolymph ranged from 0.56 μg Cd ml−1 at intermoult stage (C4) to 4.6 μg Cd ml−1 at postmoult stage (A), while the gills accumulated from 103 μg Cd g−1 dw in intermoult stage (C3) to 352 μg Cd g−1 dw in postmoult stage (A). Cadmium concentration in gills and haemolymph was also significantly higher in crabs in late premoult
stage (D3) compared to C4-crabs, while midgut gland cadmium concentration remained elevated in C1- and C3- intermoult stages relative to C4. During ovarian maturation the cadmium accumulation in midgut gland, gills, ovaries and haemolymph decreased. Average cadmium
concentration in the midgut gland decreased from 63 μg g−1 dw in ovarian Stage I to 19 μg g−1 dw in ovarian Stage VI. The same pattern was observed for gills, haemolymph and ovaries. The present study demonstrates that
cadmium accumulation in the female shore crab strongly depends on the physiological status of the animal. A possible association
between physiological calcium requirements and cadmium accumulation during moulting is discussed.
Received: 20 January 2000 / Accepted: 20 July 2000 相似文献
10.
Eeva A. Mustonen Tuija Jokela Ilkka Saastamoinen Juhani Taponen Suvi Taponen Hannu Saloniemi Kristiina Wähälä 《Environmental Chemistry Letters》2006,3(4):154-159
An expedient high performance liquid chromatography (HPLC) method was developed for the quantitative analysis of environmental estrogenic isoflavonoids, particularly (S)-equol, in red clover fed ewes. We report here the phytoestrogen analysis of red clover silage and the serum of ewes fed with this feed. Ewes received daily 10.5 g of formononetin on average from red clover silage. In the serum samples a major part of formononetin had been metabolised to equol (average 7.7 μg ml−1). According to chiral HPLC analysis, the equol present in the serum of ewes was solely of the (S)-form. We also demonstrate the presence of the metabolite O-demethylangolensin (O-DMA) in ovine serum. 相似文献
11.
The Salí River Basin in north-west Argentina (7,000 km2) is composed of a sequence of Tertiary and Quaternary loess deposits, which have been substantially reworked by fluvial and
aeolian processes. As with other areas of the Chaco-Pampean Plain, groundwater in the basin suffers a range of chemical quality
problems, including arsenic (concentrations in the range of 12.2–1,660 μg L−1), fluoride (50–8,740 μg L−1), boron (34.0–9,550 μg L−1), vanadium (30.7–300 μg L−1) and uranium (0.03–125 μg L−1). Shallow groundwater (depths up to 15 m) has particularly high concentrations of these elements. Exceedances above WHO (2011) guideline values are 100% for As, 35% for B, 21% for U and 17% for F. Concentrations in deep (>200 m) and artesian groundwater
in the basin are also often high, though less extreme than at shallow depths. The waters are oxidizing, with often high bicarbonate
concentrations (50.0–1,260 mg L−1) and pH (6.28–9.24). The ultimate sources of these trace elements are the volcanic components of the loess deposits, although
sorption reactions involving secondary Al and Fe oxides also regulate the distribution and mobility of trace elements in the
aquifers. In addition, concentrations of chromium lie in range of 79.4–232 μg L−1 in shallow groundwater, 129–250 μg L−1 in deep groundwater and 110–218 μg L−1 in artesian groundwater. All exceed the WHO guideline value of 50 μg L−1. Their origin is likely to be predominantly geogenic, present as chromate in the ambient oxic and alkaline aquifer conditions. 相似文献
12.
Asaad Ahmed Nafees Ambreen Kazi Zafar Fatmi Muhammad Irfan Arif Ali Fujio Kayama 《Environmental geochemistry and health》2011,33(2):203-216
This study was designed to determine the association between chronic arsenic exposure through drinking groundwater and decrement
in lung function, particularly among individuals who do not have signs of arsenic lesions, among an adult population. This
was a comparative cross-sectional study conducted during the months of January to March 2009. One hundred participants ≥15 years
of age in each group, i.e. exposed (≥100 μg/l) and unexposed (≤10 μg/l) to arsenic, determined by testing drinking water samples
(using portable kits), were compared for effects on lung function using spirometry. A structured and validated questionnaire
was administered. Examination for arsenic skin lesions was also done. There was a decline in the mean adjusted FEV1 of 154.3 ml
(95% CI: −324.7, 16.0; p = 0.076), in mean adjusted FVC of 221.9 ml (95% CI: −419.5, −24.3; p = 0.028), and in FEV1/FVC ratio of 2.0 (95% CI: −25.3, 29.4; p = 0.884) among participants who were exposed to arsenic compared to those unexposed. A separate model comprising a total
of 160 participants, 60 exposed to arsenic concentrations ≥250 μg/l and 100 unexposed at arsenic concentrations of ≤10 μg/l,
showed a decrement in mean adjusted FEV1 of 226.4 ml (95% CI: −430.4, −22.4; p = 0.030), in mean adjusted FVC of 354.8 ml (95% CI: −583.6, −126.0; p = 0.003), and in FEV1/FVC ratio of 9.9 (95% CI: −21.8, 41.6; p = 0.539) among participants who were exposed to arsenic in drinking groundwater. This study demonstrated that decrement in
lung function is associated with chronic exposure to arsenic in drinking groundwater, occurring independently, and even before
any manifestation, of arsenic skin lesions or respiratory symptoms. The study also demonstrated a dose-response effect of
arsenic exposure and lung function decrement. 相似文献
13.
M. Tatzber M. Stemmer H. Spiegel C. Katzlberger G. Haberhauer M. H. Gerzabek 《Environmental Chemistry Letters》2007,5(1):9-12
Measurements of calcium carbonate contents in soils were performed with FT-IR (Fourier transform infrared) spectroscopy and
with the gas volumetric Scheibler method. To the authors’ knowledge it is the first time that carbonate was quantified in
soil samples by FT-IR spectroscopy. The carbonate contents of the test soils ranged from 11.3 to 13.1%. Both methods gave
similar results, however, results obtained from FT-IR spectra depend on the spectral band used for the carbonate determination.
In our investigation we used the bands at 875 and 2506 cm−1. In case of the band at 2506 cm−1 the difference between FT-IR and Scheibler method was a factor of 1.56, in case of 875 cm−1 the respective factor was 1.16. It can be concluded that FT-IR with both bands has a potential to be used in practice as
substitution of the Scheibler method. The advantages of the FT-IR method are better reproducibility and the simultaneous characterization
of soil organic matter in bulk samples. The disadvantage is its higher cost. 相似文献
14.
Growth and grazing responses of tintinnid ciliates feeding on the toxic dinoflagellate Heterocapsacircularisquama 总被引:1,自引:0,他引:1
T. Kamiyama 《Marine Biology》1997,128(3):509-515
Growth and feeding rates of two tintinnid species, Favellaazorica and Favellataraikaensis, were determined under various concentrations of the dinoflagellate Heterocapsacircularisquama which has been reported as highly toxic to shellfish. Mean growth rates of F. azorica and F. taraikaensis on a diet of H.circularisquama (ca. 102 cells ml−1) were 2.15 and 1.97 doublings d−1, respectively. These values are similar to those on a diet of Heterocapsatriquetra which is suitable food for various zooplankton. However, growth rates of both tintinnid species decrease with increasing
concentrations of >103 cells ml−1 of H. circularisquama. In particular, H. circularisquama under conditions of >103 cells ml−1 caused mortality in F.taraikaensis, probably due to toxins. Clearance and ingestion rates of F. azorica on H. circularisquama were 4.1 to 27.5 μl ind−1 h−1 and 1.5 to 28.7 cells ind−1 h−1, respectively, at concentrations of <104 cells ml−1 and those of F. taraikaensis were 0.9 to 22.1 μl ind−1 h−1 and 0.1 to 13.0 cells ind−1 h−1, respectively, at concentrations of <103 cells ml−1. Both clearance and ingestion rates on H.circularisquama were higher for replicates fed on H.triquetra. Daily grazing impact of the two species of Favella on the initial stage of a bloom of H.circularisquama were estimated to reach 6 to 50% of H. circularisquama at a concentration of 540 cells ml−1, indicating that grazing by tintinnids such as Favella spp. may significantly regulate the initial stages of blooms of H. circularisquama.
Received: 3 January 1997 / Accepted: 27 January 1997 相似文献
15.
Eun Jung Choy Qtae Jo Hyo-Bang Moon Chang-Keun Kang Ju-Chan Kang 《Marine Biology》2007,151(1):157-165
The time-course of uptake and elimination of benzo(a)pyrene (BaP) for the Pacific oyster, Crassostrea gigas and reproduction damage and reproductive outputs were studied. Sexually immature C. gigas broodstock were fed for 28 days with live algae grown in four BaP solutions of 0, 50, 500, and 5,000 μg L−1 (hereafter, control, 50, 500, and 5,000 oysters) and were subsequently conditioned to maturation by a feeding with BaP-free
live algae under temperature manipulation for another 28 days. The 5,000 μg L−1 oysters gained a steady state concentration, around 30,000 ng g−1 d.w. for digestive gland, a week earlier compared to the 500 μg L−1 oysters. The earlier gain or longer persistence of the steady state concentration influenced elimination of BaP, with an
eliminating trend for 500 μg L−1 oysters, while no elimination for 5,000 μg L−1 oysters. The maternal persistence of the steady state concentration resulted in significant damages in the reproductive success
and their reproductive outputs in terms of the hatching rate and larval growth, survival, and settlement. The 50 μg L−1 oysters remained far below the steady state concentration, and showed a manifest eliminating behavior during the subsequent
BaP-free 28 day maturation period. The reproductive success and initial larval events of 50 μg L−1 oysters were comparable to those of control. However, the damage potential of the 50 μg L−1 oysters might be more significant if their maternal exposure continued beyond 28 days, since the accumulation profile at this
dose was linear. 相似文献
16.
Pankaj Kumar Manish Kumar A. L. Ramanathan Maki Tsujimura 《Environmental geochemistry and health》2010,32(2):129-146
Arsenic contamination in groundwater is of increasing concern because of its high toxicity and widespread occurrence. This
study is an effort to trace the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain of
India through major ion chemistry, arsenic speciation, sediment grain-size analyses, and multivariate statistical techniques.
The study focuses on the distinction between the contributions of natural weathering and anthropogenic inputs of arsenic with
its spatial distribution and seasonal variations in the plain of the state Bihar of India. Thirty-six groundwater and one
sediment core samples were collected in the pre-monsoon and post-monsoon seasons. Various graphical plots and statistical
analysis were carried out using chemical data to enable hydrochemical evaluation of the aquifer system based on the ionic
constituents, water types, hydrochemical facies, and factors controlling groundwater quality. Results suggest that the groundwater
is characterized by slightly alkaline pH with moderate to strong reducing nature. The general trend of various ions was found
to be Ca2+ > Na+ > Mg2+ > K+ > NH4
+; and HCO3
− > Cl− > SO4
2− > NO3
− > PO4
3− > F− in both seasons. Spatial and temporal variations showed a slightly higher arsenic concentration in the pre-monsoon period
(118 μg/L) than in the post-monsoon period (114 μg/L). Results of correlation analyses indicate that arsenic contamination
is strongly associated with high concentrations of Fe, PO4
3−, and NH4
+ but relatively low Mn concentrations. Further, the enrichment of arsenic is more prevalent in the proximity of the Ganges
River, indicating that fluvial input is the main source of arsenic. Grain size analyses of sediment core samples revealed
clay (fine-grained) strata between 4.5 and 7.5 m deep that govern the vertical distribution of arsenic. The weathering of
carbonate and silicate minerals along with surface-groundwater interactions, ion exchange, and anthropogenic activities seem
to be the processes governing groundwater contamination, including with arsenic. Although the percentage of wells exceeding
the permissible limit (50 μg/L) was less (47%) than that reported in Bangladesh and West Bengal, the percentage contribution
of toxic As(III) to total arsenic concentration is quite high (66%). This study is vital considering that groundwater is the
exclusive source of drinking water in the region and not only makes situation alarming but also calls for immediate attention. 相似文献
17.
Total mercury and methylmercury concentrations in fish from the Mojana region of Colombia 总被引:1,自引:0,他引:1
Marrugo-Negrete J Verbel JO Ceballos EL Benitez LN 《Environmental geochemistry and health》2008,30(1):21-30
Total mercury (T-Hg) and methylmercury (MeHg) concentrations have been measured in the muscle tissue of 16 fish species consumed
in the Mojana region of Colombia. T-Hg analysis was performed by cold-vapor atomic-absorption spectroscopy (CV-ASS) and MeHg
analysis by gas chromatography with electron-capture detection. Higher T-Hg and MeHg concentrations were detected in carnivorous
species (T-Hg = 0.371 ± 0.172 (μg g−1 fresh wt, MeHg = 0.346 ± 0.171 μg g−1 fresh wt) than in non-carnivorous fish (T-Hg = 0.155 ± 0.108 μg g−1 fresh wt, MeHg = 0.146 ± 0.102 μg g−1 fresh wt). In the different species mercury was present almost completely as the methylated form, with percentages between
80.5 and 98.1% (mean 92.0 ± 3.4%). In 13.5% of fish-tissue samples T-Hg concentrations exceeded the maximum level recommended
by the World Health Organization for human consumption (Hg = 0.5 μg g−1 fresh wt). Although mean T-Hg concentrations in all fish samples (0.269 ± 0.181 μg g−1 fresh wt) did not exceed this limit, risk assessment suggested that the consumption of 0.12 kg fish day−1 could increase the risk of mercury poisoning of the inhabitants of this region. 相似文献
18.
Debapriya Mondal Mayukh Banerjee Manjari Kundu Nilanjana Banerjee Udayan Bhattacharya Ashok K. Giri Bhaswati Ganguli Sugata Sen Roy David A. Polya 《Environmental geochemistry and health》2010,32(6):463-477
Remediation aimed at reducing human exposure to groundwater arsenic in West Bengal, one of the regions most impacted by this
environmental hazard, are currently largely focussed on reducing arsenic in drinking water. Rice and cooking of rice, however,
have also been identified as important or potentially important exposure routes. Quantifying the relative importance of these
exposure routes is critically required to inform the prioritisation and selection of remediation strategies. The aim of our
study, therefore, was to determine the relative contributions of drinking water, rice and cooking of rice to human exposure
in three contrasting areas of West Bengal with different overall levels of exposure to arsenic, viz. high (Bhawangola-I Block,
Murshidibad District), moderate (Chakdha Block, Nadia District) and low (Khejuri-I Block, Midnapur District). Arsenic exposure
from water was highly variable, median exposures being 0.02 μg/kg/d (Midnapur), 0.77 μg/kg/d (Nadia) and 2.03 μg/kg/d (Murshidabad).
In contrast arsenic exposure from cooked rice was relatively uniform, with median exposures being 0.30 μg/kg/d (Midnapur),
0.50 μg/kg/d (Nadia) and 0.84 μg/kg/d (Murshidabad). Cooking rice typically resulted in arsenic exposures of lower magnitude,
indeed in Midnapur, median exposure from cooking was slightly negative. Water was the dominant route of exposure in Murshidabad,
both water and rice were major exposure routes in Nadia, whereas rice was the dominant exposure route in Midnapur. Notwithstanding
the differences in balance of exposure routes, median excess lifetime cancer risk for all the blocks were found to exceed
the USEPA regulatory threshold target cancer risk level of 10−4–10−6. The difference in balance of exposure routes indicate a difference in balance of remediation approaches in the three districts. 相似文献
19.
The effect of irradiance, prey concentration and pH on the growth and grazing responses of the mixotrophic prymnesiophyte
Chrysochromulina ericina under N-and P-replete conditions was studied using the pedinophyte Marsupiomonas pelliculata as prey. The two organisms were inoculated in monocultures and in mixed cultures at different predator: prey ratios at three
irradiances and allowed to grow for 4–7 days. All cultures were non-axenic. Algal densities and pH were monitored throughout
the experiments and growth and grazing rates were measured. An increase in growth of C. ericina cultures at irradiances of 25 and 70 μmol photons m−2 s−1 was observed after the addition of prey, while growth of C. ericina cultures at the high irradiance (150 μmol photons m−2 s−1) was unaffected by the addition of prey. However, although the growth of C. ericina increased at low irradiance (25 μmol photons m−2 s−1), it did not reach the same level as monocultures at the high irradiance (150 μmol photons m−2 s−1), suggesting that phagotrophy can only partly replace photosynthesis in C. ericina. Maximum growth rates of C. ericina at irradiances of 25 and 70 μmol photons m−2 s−1 were obtained at concentrations of > 0.15–0.3×105
M. pelliculata ml−1, corresponding to 50–100 μg C 1−1. Ingestion of M. pelliculata cells by C. ericina did not generally follow Michaelis—Menten kinetics. Deviation from the expected saturation kinetics was especially pronounced
at irradiances of 70 and 150 μmol photons m−2 s−1. At these irradiances ingestion of M. pelliculata cells by C. ericina decreased at high concentrations of M. pelliculata, indicating an increased uptake of bacterial prey in these cultures. The growth rate of C. ericina was affected in both monocultures and in mixed cultures when pH increased above 8.6, and growth stopped around pH 9. The
prey alga M. pelliculata tolerated high pH better and, consequently, took over in the mixed cultures when pH exceeded 9. The ecological significance
of mixotrophy in the genus Chrysochromulina is discussed.
Published online: 4 July 2002 相似文献
20.
To investigate copepod nauplii ingestion rates on phytoplankton, we have adapted the traditional gut fluorescence technique
as it can be used with lower gut pigment concentrations. With the improved technique, laboratory experiments were performed
to estimate functional responses for nauplii of Calanus helgolandicus and Centropages typicus. Nauplii were raised from eggs to copepodites and the experiments were performed with stages NIV-NV. Gut evacuation rates
and ingestion rates were measured on Isochrysis galbana at different concentrations. Specific ingestion rates ranged between 0.038–0.244 μg C μg−1 nauplii C d−1 for C. typicus and 0.041–1.412 μg C μg−1 nauplii C d−1 for C. helgolandicus. Both species showed a type III functional response, reaching a saturation concentration at around 600 μgC l−1 for C. typicus and 800 μgC l−1 for C. helgolandicus.
An erratum to this article can be found at 相似文献