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891.
do A Kehrig H Seixas TG Palermo EA Baêta AP Castelo-Branco CW Malm O Moreira I 《Environmental science and pollution research international》2009,16(1):10-24
Background, aim, and scope Selenium (Se) has been shown to reduce mercury (Hg) bioavailability and trophic transfer in aquatic ecosystems. The study
of methylmercury (MeHg) and Se bioaccumulation by plankton is therefore of great significance in order to obtain a better
understanding of the estuarine processes concerning Hg and Se accumulation and biomagnification throughout the food web. In
the western South Atlantic, few studies have documented trace element and MeHg in fish tissues. No previous study about trace
elements and MeHg in plankton has been conducted concerning tropical marine food webs. Se, Hg, and MeHg were determined in
two size classes of plankton, microplankton (70–290 μm) and mesoplankton (≥290 μm), and also in muscle tissues and livers
of four fish species of different trophic levels (Mugil liza, a planktivorous fish; Bagre spp., an omnivorous fish; Micropogonias furnieri, a benthic carnivorous fish; and Centropomus undecimalis, a pelagic carnivorous fish) from a polluted estuary in the Brazilian Southeast coast, Guanabara Bay. Biological and ecological
factors such as body length, feeding habits, and trophic transfer were considered in order to outline the relationships between
these two elements. The differences in trace element levels among the different trophic levels were investigated.
Materials and methods Fish were collected from July 2004 to August 2005 at Guanabara Bay. Plankton was collected from six locations within the bay
in August 2005. Total mercury (THg) was determined by cold vapor atomic absorption spectrometry (CV-AAS) with sodium borohydride
as a reducing agent. MeHg analysis was conducted by digesting samples with an alcoholic potassium hydroxide solution followed
by dithizone-toluene extraction. MeHg was then identified and quantified in the toluene layer by gas chromatography with an
electron capture detector (GC-ECD). Se was determined by AAS using graphite tube with Pin platform and Zeeman background correction.
Results and discussion Total mercury, MeHg, and Se increased with plankton size class. THg and Se values were below 2.0 and 4.8 μg g−1 dry wt in microplankton and mesoplankton, respectively. A large excess of molar concentrations of Se in relation to THg was
observed in both plankton size class and both fish tissues. Plankton presented the lowest concentrations of this element.
In fish, the liver showed the highest THg and Se concentrations. THg and Se in muscle were higher in Centropomus undecimalis (3.4 and 25.5 nmol g−1) than in Micropogonias furnieri (2.9 and 15.3 nmol g−1), Bagre spp (1.3 and 3.4 nmol g−1) and Mugil liza (0.3 and 5.1 nmol g−1), respectively. The trophic transfer of THg and Se was observed between trophic levels from prey (considering microplankton
and mesoplankton) to top predator (fish). The top predators in this ecosystem, Centropomus undecimalis and Micropogonias furnieri, presented similar MeHg concentrations in muscles and liver. Microplankton presented lower ratios of methylmercury to total
mercury concentration (MeHg/THg) (34%) than those found in mesoplankton (69%) and in the muscle of planktivorous fish, Mugil liza (56%). The other fish species presented similar MeHg/THg in muscle tissue (of around 100%). M. liza showed lower MeHg/THg in the liver than C. undecimalis (35%), M. furnieri (31%) and Bagre spp. (22%). Significant positive linear relationships were observed between the molar concentrations of THg and Se in the
muscle tissue of M. furnieri and M. liza. These fish species also showed significant inverse linear relationships between hepatic MeHg and Se, suggesting a strong
antagonistic effect of Se on MeHg assimilation and accumulation.
Conclusions Differences found among the concentrations THg, MeHg, and Se in microplankton, mesozooplankton, and fishes were probably related
to the preferred prey and bioavailability of these elements in the marine environment. The increasing concentration of MeHg
and Se at successively higher trophic levels of the food web of Guanabara Bay corresponds to a transfer between trophic levels
from the lower trophic level to the top-level predator, suggesting that MeHg and Se were biomagnified throughout the food
web. Hg and Se were positively correlated with the fish standard length, suggesting that larger and older fish bioaccumulated
more of these trace elements. THg, MeHg, and Se were a function of the plankton size.
Recommendations and perspectives There is a need to assess the role of selenium in mercury accumulation in tropical ecosystems. Without further studies of
the speciation of selenium in livers of fishes from this region, the precise role of this element, if any, cannot be verified
in positively affecting mercury accumulation. Further studies of this element in the study of marine species should include
liver samples containing relatively high concentrations of mercury. A basin-wide survey of selenium in fishes is also recommended. 相似文献
892.
893.
Occurrence, sources, and inventory of hexabromocyclododecanes (HBCDs) in soils from Chongming Island, the Yangtze River Delta (YRD) 总被引:6,自引:0,他引:6
Hexabromocyclododecanes (HBCDs) is a concern due to their large usage combining with physico-chemical properties and toxicity to wildlife and human. However, very limited data were reported on HBCDs in soils, especially from rural area. In this study, 22 soil samples were collected from Chongming Island at estuary of the Yangtze River Delta, to investigate the level, diasteroisomer profile, potential sources, and mass inventory of HBCDs. The total concentrations ranged from not detected to 93.8 pg g−1 dry weight (dw) with a mean of 23.3 pg g−1 dw, which was at the low end of the global levels. The wide distribution of HBCDs in soils suggested that the local emissions of HBCD-containing materials and/or the inputs via atmospheric transport from other regions were two possible sources. Variation of HBCDs levels was observed in different types of soils. Woodland, tideland and road soils contained slightly higher HBCDs than those of farmland and grassland. Overall, γ-HBCD was the dominant diasteroisomer in soils, followed by α-HBCD and β-HBCD. Significant but weak correlations were only found between α-HBCD and β-HBCD versus TOC content in soils. Currently, the mass inventory of HBCDs in soils of Chongming Island was 5.3 kg. Based on these data, we gave perspective on human intake of HBCDs via soil ingestion by age. Local resident’s intakes ranged from 15.5 to 97.8 fg kg body weight−1 d−1, in which children are exposed more than adults. 相似文献
894.
海河干流、大沽排污河沉积物中有机氯农药的残留状况 总被引:7,自引:0,他引:7
调查了海河干流和大沽排污河沉积物中持久性有机氯杀虫剂(OCPs)的残留状况.在所选取的16个断面沉积物样品中均有大量HCHs、DDTs检出,表明海河和大沽排污河的DDT和HCH污染相当严重.海河沉积物中HCHs和DDTs总质量浓度分别为3.30~75.96、1.57~221.57 ng/g.大沽排污河沉积物中HCHs和DDTs的残留量分别为2.30~124.61、11.28~237.30ng/g.与国内外部分河流表层沉积物中HCHs、DDTs的含量相比,海河和大沽排污河沉积物中有机氯农药含量较高.最后根据两条河流沉积物中的OCPs的残留量,分析了其可能的污染源. 相似文献
895.
目前分子生物技术发展日新月异,已渗透到各相关学科。本文综述了分子生物技术的基本原理与方法,及其在环境工程微生物领域的应用。讨论了分子生物技术在环境工程微生物的检测应用及在污泥、生物膜、底泥和土壤等微生物种群的多样性分析方面,以及环境工程菌的挑选和培养等方面的研究成果及其巨大研究前景,对该技术在环境工程领域的应用与发展提出了一些见解。 相似文献
896.
Li R. Gao Dan. Xia Hai Z. Tian Hai J. Zhang Li D. Liu Yi W. Wang 《Journal of environmental science and health. Part. B》2013,48(5):322-330
Organochlorine pesticides (OCPs) were analyzed in 26 surface sediment samples from the Liaohe River basin, and the distributions of and potential environmental risks posed by OCPs in the basin were evaluated. Eighteen OCPs listed in the Stockholm Convention were determined using isotope-dilution gas chromatography–high resolution mass spectrometry. This is the first study of hexachlorobenzene (HCB) in the Liaohe River basin sediments. The total OCP concentrations were 0.39–68.06 ng g?1 dry weight. The total α-, β-, γ-, and δ-hexachlorocyclohexane (HCH), the total dichlorodiphenyltrichloroethane (DDT – p,p′-dichlorodiphenyldichloroethane (DDD), p,p′-dichlorodiphenyldichloroethylene (DDE), o,p'-DDT, and p,p′-DDT), and the HCB concentrations in the sediment samples were 0.1–28.48 ng g?1 (mean 4.01 ng g?1), 0.08–6.52 ng g?1 (mean 3.07 ng g?1), and 0.18–24.8 ng g?1 (mean 4.38 ng g?1), respectively. The HCB concentrations were higher than the concentrations of the other OCPs, and the HCHs and HCB together were the dominant OCPs. β-HCH was the most abundant HCH isomer. The concentrations of DDTs and other OCPs were relatively low, and the (DDE+DDD)/DDT ratios (>0.5) and DDD/DDE ratios (<1) indicated that no recent DDT inputs had occurred in the Liaohe River system. The main sources of HCHs were probably the historical production and agricultural use of HCH in the study area. The DDT and HCH concentrations were generally below or similar to the concentrations that have been found in other parts of the world. An ecotoxicological evaluation indicated that HCHs in surface sediments pose slight risks to human and ecological health in the Liaohe River basin. 相似文献
897.
为了在酸性条件下实现剩余污泥中磷的高效回收,对pH=3时剩余污泥水解酸化过程中氨氮、正磷酸盐和钙镁离子的溶出现象以及磷回收进行了研究分析。结果表明:当pH=3时,所溶出的氨氮、镁离子和钙离子与磷酸盐的摩尔比均大于1,能满足采用鸟粪石沉淀法或者羟磷灰石沉淀法回收磷的要求;但所溶出的钙镁离子的摩尔比大于1,会对鸟粪石沉淀法回收磷的顺利进行有较大影响;有无外加镁剂对磷回收率影响不大。采用改型后的镁型强酸性阳离子交换树脂进行离子交换可以得到较高纯度的鸟粪石沉淀产品,通过XRD检测其纯度为95%以上。 相似文献
898.
The Influence of Mycorrhiza on Uranium and Phosphorus Uptake by Barley Plants from a Field-contaminated Soil (7 pp) 总被引:3,自引:0,他引:3
Chen B Zhu YG Zhang X Jakobsen I 《Environmental science and pollution research international》2005,12(6):325-331
Background Recent studies indicated that arbuscular mycorrhizal fungi (AMF) play important roles in plant accumulation of uranium (U)
from contaminated environments, but the impacts of fertilization practices on functioning of the symbiotic associations, which
are crucial factors influencing plant nutrition and growth responses to mycorrhiza, have rarely been considered.
Materials and Methods In a greenhouse experiment, a bald root barley mutant (brb) together with the wild type (wt) were used to test the role of
root hairs and AMF in uranium (U) uptake by host plants from a U contaminated soil. Nil, 20 and 60 mg KH2PO4-P kg–1 soil were
included to investigate the influences of phosphorus (P) fertilization on plant growth and accumulation of U.
Results Dry matter yield of barley plants increased with increasing P additions and wt produced significantly higher dry weight than
brb. Mycorrhiza markedly improved dry matter yield of both genotypes grown at nil P, whereas only brb responded positively
to mycorrhiza at 20 mg P kg-1. At the highest P level, mycorrhiza resulted in growth depressions in both genotypes, except
for the roots of wt. In general, plant P concentrations increased markedly with increasing P additions and in response to
mycorrhiza.
Mycorrhiza and P additions had no significant effects on shoot U concentrations. However, root U concentrations in both genotypes
were significantly increased by mycorrhiza. On the other hand, shoot U contents increased with increasing P levels, while
20 mg P kg-1 stimulated, but 60 mg P kg-1 marginally affected the U accumulation in roots. Root length specific U uptake was
moderately enhanced both by root hairs and strongly enhanced by mycorrhiza. Moreover, non-inoculated plants generally had
higher shoot-root ratios of U content than the corresponding inoculated controls.
Conclusion Our study shows that AMF and root hairs improves not only P acquisition but also the root uptake of U, and mycorrhiza generally
decreases U translocation from plant root to shoot. Hence, mycorrhiza is of potential use in the phytostabilization of U contaminated
environments.
Perspectives The complex impacts of P on U accumulation by barley plants suggested that U behavior in mycorrhizosphere and translocation
along the soil-fungi-plant continuum as affected by fertilization practices deserve extensive studies for optimizing the function
of mycorrhizal associations for phytoremediation purposes. 相似文献
899.
复合微生物菌剂强化堆肥技术研究 总被引:23,自引:0,他引:23
采用复合微生物菌剂对生活垃圾的接种堆肥技术进行了实验研究。通过测定堆肥过程中反应器出口O2、CO2与H2S气体浓度及对堆肥样品扫描电镜照片分析,比较了3个接种组与1个对照组中堆料中微生物总数变化、种群结构演替及堆肥腐熟速度。试验结果表明,在原料成分为:生活垃圾/成熟堆肥=80/20,有机物约为60%,初始含水率为55%,初始C/N-30时,对于不同接种量的复合微生物接种系统堆料中分别接种0.2%、0.3%、0.5%(质量百分含量),与加入0.3%灭活菌的对照组进行对比实验,接种复合微生物菌剂堆肥系统不仅微生物总数高于对照组,而且其种群结构合理,能明显提高堆肥效率,有效控制臭气的产生,提高堆肥腐熟度。 相似文献
900.
城市河流水质常规评价技术研究 总被引:11,自引:0,他引:11
运用综合水质标识指数法,对我国河流水质评价面临的关键技术问题,包括水质评价方法、水质评价项目,水质级别评价,水环境功能区达标评价、水质定性评价、河流及水系整体水质比较、水质随时间和空间变化等作了明确界定,并介绍了在上海河流水质评价中的应用。 相似文献