Contamination of polycyclic aromatic hydrocarbons in surface sediments of mangrove swamps

The concentrations of total polycyclic aromatic hydrocarbons (sigmaPAHs) and 15 individual PAH compounds in 20 surface sediments collected from four mangrove swamps in Hong Kong were analysed. sigmaPAH concentrations ranged from 356 to 11,098 ng g(-1) dry weight with mean and median values of 1992 and 1,142 ng g(-1), respectively. These values were significantly higher than those of marine bottom sediments of Hong Kong harbours, suggesting that more PAHs were accumulated in mangrove surface sediments. The concentrations of sigmaPAHs as well as individual PAH compound varied significantly among mangrove swamps. The swamps heavily polluted by livestock and industrial sewage, such as Ho Chung and Mai Po, had much higher concentrations of total PAHs and individual PAH than the other swamps. The PAH profiles were similar among four mangrove swamps, and were dominated by naphthalene (two-ring PAH), fluorene and phenanthrene (three-ring PAH). The mangrove sediments had higher percentages of low-molecular-weight PAHs. These indicated that PAHs in mangrove sediments might originate from oil or sewage contamination (petrogenic input). Ratio values of specific PAH compounds such as phenanthrene/anthracene and fluoranthene/ pyrene, were calculated to evaluate the possible source of PAH contamination in mangrove sediments. These ratios varied among samples, suggesting that mangrove sediments might have a mixed pattern of pyrolytic and petrogenic inputs of PAHs. Sediments collected from Ho Chung mangrove swamp appeared to be more dominated by pyrolytic input while those from Tolo showed strong petrogenic contamination.     

Enhanced nutrient removal by oxidation-reduction potential (ORP) control in laboratory-scale extended aeration reactors

A study was conducted to examine N and P removal by a laboratory-scale extended aeration treatment system employing oxidation-reduction potential (ORP) controlled aeration. The system was provided with a 90-L aeration tank. When ORP controlled aeration was applied, the aeration tank was divided into three zones, namely the ORP zone (45 L), the anaerobic zone (27 L) and the aerobic zone (18 L). An external anoxic selector of 3.8 L in volume was also added. An ORP set point of 70 mV was used for the ORP zone. The extended aeration treatment system operating without the ORP controlled aeration was used as the control.COD removal (97%) was not affected, but both N and P removal were enhanced significantly in the ORP reactor. Total N removal efficiency was increased from 49.1% (control) to 83.5%. Almost all P was captured (99%), leaving an average of 0.09 mg L⁻¹ P in the effluent. The ORP reactor yielded a sludge P content of 3.1%, compared to only 1.8% for the control. This indicated luxury P uptake in ORP reactor. Very significant P release and denitrification were found in the anoxic selector. Fairly good simultaneous nitrification and denitrification had occurred in the ORP zone. However, P release was very limited in the anoxic zone. However, anoxic P uptake and nitrification were found in this zone.Low F/M bulking was observed in both the control and ORP operation before the installation of a selector. Bacterial Type 0041 was identified as the predominant bulking organism. For the Control, an aerobic selector cured the bulking problem in one sludge age while an anoxic selector fixed up the problem during the ORP operation.     

Oxidative stress in the blood of pregnant rats and reduction of organ weights caused by the polychlorinated biphenyl congener 77

3,3′,4,4′-Tetrachlorobiphenyl (PCB 77), one of the environmentally persistent polychlorinated biphenyls that have been used for industrial purposes, was repeatedly administered to pregnant rats by gavage at a dose of minimal, non-lethal toxicity in order to study its effects on routine blood variables, parameters of oxidative stress and hematopoietic organs in pregnant female rats. Of the routine blood parameters, PCB 77 reduced the mean corpuscular hemoglobin concentration and platelet counts; the levels of malondialdehyde and glutathione peroxidase in the blood were higher during the first days of gestation (1–7), as compared to the respective controls. In the subsequent period between days 8 and 18, these parameters did not show any significant change after PCB 77 treatment. Routine blood parameters and oxidative stress parameters indicated a moderate degree of oxidative stress which alone could not bring about the serious weight reduction of the thymus, pituitary, and kidneys. The extent of oxidative stress did not correlate with the weight reduction of some of the blood-forming organs.     

The role of radial oxygen loss and root anatomy on zinc uptake and tolerance in mangrove seedlings

Root anatomy, radial oxygen loss (ROL) and zinc (Zn) uptake and tolerance in mangrove plants were investigated using seedlings of Aegiceras corniculatum, Bruguiera gymnorrhiza and Rhizophora stylosa. The results revealed that B. gymnorrhiza, which possessed the ‘tightest barrier’ in ROL spatial patterns among the three species studied, took up the least Zn and showed the highest Zn tolerance. Furthermore, zinc significantly decreased the ROL of all three plants by inhibition of root permeability, which included an obvious thickening of outer cortex and significant increases of lignification in cell walls. The results of SEM X-ray microanalysis further confirmed that such an inducible, low permeability of roots was likely an adaptive strategy to metal stress by direct prevention of excessive Zn entering into the root. The present study proposes new evidence of structural adaptive strategy on metal tolerance by mangrove seedlings.     

Current efforts to monitor and conserve the Eastern Imperial Eagle Aquila heliaca in Hungary

The globally threatened Eastern Imperial Eagle Aquila heliaca has been one of the flagship species of Hungarian bird conservation efforts since the 1980s. Due to these conservation activities and positive land-use changes during the last 2 decades, the Hungarian Imperial Eagle population increased from as few as approximately 20 pairs in the early 1980s to 81 pairs by 2006. Between 2002 and 2005 as part of a LIFE-Nature project, MME/Birdlife Hungary carried out particularly intensive monitoring, conservation, research, and public awareness actions. The main goal of the project was to secure the long-term sustainable increase in the Imperial Eagle population after Hungary's European Union accession in 2004. New methods were developed and applied to census and monitor the breeding and wintering population sizes. Standardized baseline land-use mapping and surveys were introduced to detect long-term land-use and prey density changes in priority areas for Imperial Eagles and to monitor the effects of key mortality factors, such as electrocution. Historical information and data gathered before and during the project period were assimilated using a Geographic Information System and incorporated into a comprehensive set of Imperial Eagle Management Guidelines.     

Composting of spent pig litter at different seasonal temperatures in subtropical climate

To investigate the effects of seasonal temperatures on the composting of spent pig-manure sawdust litter (spent litter), two sets of experiments were carried out: one during winter, the other during summer. Physicochemical and microbial parameters including temperature, pH, inorganic N, humification indicators (HA and FA), heavy metals (Cu and Zn), total aerobic heterotrophs, ATP content and dehydrogenase activity were measured to understand changes in the spent litter during composting. Results demonstrated that the composting was faster during summer than winter. The spent litter during the summer trial reached maturity at day 56 whereas that of the winter trial was still immature at the end of composting (days 91). Microbial activities during the thermophilic stage of composting were much lower in the winter trial. Values began to increase during the latter part of composting, indicating that the spent litter in this winter trial was biologically unstable and must be further composted to reach full maturity. The changes in the microbial activities of the spent litter during summer or winter reflected the changes in their temperatures and chemical properties. The maturation of the spent litter during summer was accompanied by stabilization of the microbial and chemical properties and a drop in temperature to ambient level. Results of correlation analysis showed that temperature correlated not only with the microbial parameters but also with most of the chemical parameters. These parameters also correlated with each other. Among all the parameters measured, the trend of temperature changes is the simplest and most rapid parameter that can be used to evaluate the maturity of spent litter.     

Recovery of novel bacterial diversity from mangrove sediment

Bacteria in the surface sediments of a subtropical mangrove habitat were investigated using a cultivation-independent molecular approach. Phylogenetic analysis of nearly full-length 16S rRNA genes revealed a diversity of sequences that were mostly novel. Members from the five subdivisions of the Proteobacteria were detected, and they collectively represented the majority (67%) of the clone library. Sequence types affiliated with the Gammaproteobacteria constituted the largest portion (29%) of the library, and many of them were related to free-living and symbiotic sulfur-oxidizing bacteria. The Epsilonproteobacteria were the second most abundant group (16%), including only one sequence type clustering with PCR-generated bacterial clones previously recovered from deep-sea sediments. A substantial portion (8%) of the clones grouped within the Deltaproteobacteria, a subdivision with anaerobic sulfate or metal reduction as the predominant metabolic trait of its members. In addition, minor portions were affiliated with the Cytophaga–Flexibacter–Bacteroides group (9%), Actinobacteria (6%), Chloroflexi (5%), Firmicutes (4%), Fusobacteria (1%), and the Chlamydiae/Verrucomicrobia group, Fibrobacteres/Acidobacteria group and Planctomycetes (each < 1%). These results significantly expand our knowledge of the bacterial diversity of the unique mangrove environment.     

人工污水中的N在模拟秋茄湿地系统中的分配循环及其净化效果

在温室中建立模拟红树林植物秋茄湿地系统，系统包括１年生秋茄苗、底泥和潮汐海水，分别用正常、５倍和１０倍浓度的人工制备的城市污水每周定时、定时对模拟系统污灌２次，持续１年。用以研究营养污物Ｎ在系统中的分配循环及被净化的效果。结果表明，加入系统中的污水Ｎ主要留存在土壤中，留存在植物中只有一小部分，４个处理污水浓度组植株中Ｎ元素周转期衣次为４．１年、４．９年、５．３年和４．３年，比２０龄的秋茄群落Ｎ周期