Partitioning of PAHs in pore water from mangrove wetlands in Shantou, China.

To investigate the trend of selected polycyclic aromatic hydrocarbons (PAHs) partitioning, fifteen pore water samples collected from the sediments of three mangrove wetlands were analyzed, and the partition coefficients and the partition model for the PAHs were determined by the correlation between K(oc) and octanol-water partition coefficient (K(ow)). The results revealed that the mean Kp values in inner mangrove wetlands were between 143 and 1031 L /Kg; the particulate organic carbon (POC) could strongly adsorb low-ring PAHs; the PAHs partitioning was on a obvious trend transported to particle phase. We suggest that the classic equilibrium model of organic carbon normalized (K(p)=K(oc)f(oc)) may be used to predict the trend of the selected PAHs partitioning.

The effect of mangrove reforestation on the accumulation of PCBs in sediment from different habitats in Guangdong, China.

To investigate the influence of mangrove reforestation on the accumulation of PCBs, the concentrations and homologue patterns of polychlorinated biphenyls in surface sediments from different mangrove forests and their adjacent mud flats in Guangdong Province were determined. The total PCB concentrations in the sediments ranged from 3.03 to 46.62 ng g⁻¹ (dry weight). Differences in the accumulation and distribution of PCBs were found between the mangrove sites and the mud flats. Furthermore, the natural forests and restored mangrove forests of native species showed slight PCB contamination, whereas the exotic species Sonneratia apetala exacerbated the PCB pollution at certain sites. It was suggested that the native mangrove species Kandelia candel and Aegiceras corniculatum could represent good choices for the phytoremediation of PCB contamination.

Interactions among Fe2+, S2-, and Zn2+ tolerance, root anatomy, and radial oxygen loss in mangrove plants.

Root anatomy, radial oxygen loss (ROL), and tolerances to ferrous (Fe(2+)), sulphide (S(2-)), and zinc (Zn(2+)) ions were investigated in seedlings of eight species of mangrove, including three pioneer species, three rhizophoraceous and two landward semi-mangrove species. The results showed an interesting co-tolerance to Fe(2+), S(2-), and Zn(2+). The three rhizophoraceous species (Bruguiera gymnorrhiza, Kandelia obovata and Rhizophora stylosa), which possessed the thickest lignified exodermis and the 'tightest barrier' in ROL spatial pattern, consistently exhibited the highest tolerance to Fe(2+), S(2-), and Zn(2+). B. gymnorrhiza could directly reduce ROL by increasing lignification within the exodermis. Such an induced barrier to ROL is a probable defence response to prevent further invasion and spread of toxins within plants. The data also indicated that, in B. gymnorrhiza, Fe(2+) or S(2-), or both, induced a lignified exodermis that delayed the entry of Zn(2+) into the roots and thereby contributed to a higher tolerance to Zn(2+). This study provides new evidence of exclusive strategies of mangrove seedling roots in dealing with contaminations. The information is also important in the selection and cultivation of tolerant species for the bioremediation of contaminated waters or soils.

[Health assessment of Qi'ao Island mangrove wetland ecosystem in Pearl River Estuary].

Based on the theories of wetland ecosystem health and by using "Pressure-State-Response" model, a health assessment indicator system for Qi' ao Island mangrove wetland ecosystem in Pearl River Estuary was built, and the assessment indices, assessment criteria, indices weighted values, assessment grades, and assessment methods were established to assess the health state of this ecosystem. In 2008, the overall health index of this ecosystem was 0.6580, health level was of grade II (healthy), and the pressure, state, and response indices were 0.3469, 0.8718, and 0.7754, respectively, suggesting that this ecosystem was good in state and response, but still had definite pressure. As a provincial nature reserve, this ecosystem was to be further improved in its health level. However, the research on the health assessment of mangrove wetland ecosystem was still young. Further studies should be made on the selection of assessment indices, long-term oriented monitoring of these indices, and quantification of the relations between ecosystem health level and ecosystem services.

Influence of mangrove reforestation on heavy metal accumulation and speciation in intertidal sediments.

To investigate the influence of mangrove reforestation on heavy metal accumulation and speciation in intertidal sediments, core sediments from a restored mangrove forest and adjacent mud flat in Yifeng Estuary (southeastern China) were analyzed. The chemical speciation of heavy metals (Pb, Zn, Cu, Cr and Ni) was determined according to a sequential extraction procedure. Special attention was paid to the upper 20cm of sediment, in which metal accumulation was enhanced and speciation was obviously modified. Mangrove reforestation decreased the concentrations of all metals in the acid-soluble fraction and increased metal concentrations in the oxidizable fraction. Increased Pb, Zn and Cu concentrations and decreased Ni and Cr concentrations were observed in the reducible fraction. These results suggest that mangrove reforestation facilitated the accumulation of heavy metals in the upper sediment layers but decreased their bioavailability and mobility.

Toxicity of bisphenol A and its bioaccumulation and removal by a marine microalga Stephanodiscus hantzschii.

The toxicity of bisphenol A (BPA) to Stephanodiscus hantzschii, a diatom isolated from tidal water of Futian Mangrove Nature Reserve, China, and the bioaccumulation and removal capability of the marine microalga to BPA were investigated in the present study. Toxicity experiments showed that the 96-h EC50 of BPA was 8.65+/-0.26 mg/L, and the cell number and chlorophyll a content of S. hantzschii decreased significantly with increases in BPA at concentrations higher than 3.00 mg/L. S. hantzschii had high removal capability at low BPA concentrations as BPA was bioaccumulated and biodegraded by cells. After 16-day treatment, 88%, 99%, 92%, 61%, 48%, 28% and 26% of BPA were removed by the diatom in the media supplemented with 0.01, 0.10, 1.00, 3.00, 5.00, 7.00 and 9.00 mg/L BPA, respectively. The present study demonstrated that S. hantzschii was a tolerant isolate that could be used to remove BPA from contaminated waters.

[Distribution and migration of zinc in Avicennia marina plant-soil system].

Zinc is a major anthropogenic contaminant in estuarine ecosystem, and has potential ecotoxicological consequences for aquatic animals and plants. An artificial mangrove wetland was set up in greenhouse to study the distribution and migration of zinc in synthetic wastewater in Avicennia marina plant-soil system. Different concentration synthetic wastewater and 1.5% salinity artificial seawater (control) were discharged into the system in fixed quantity twice a week for a year. The results showed that most part (> 67%) of zinc in the artificial wastewater discharged into the system was remained in the soil, and only a small portion (1.24%-10.4%) of it was entered into plant and litter, indicating that this artificial plant-soil system had a stronger purifying effect on the zinc in synthetic wastewater. The calculation with matter balance model indicated that soil subsystem had a higher environmental capacity of bearing zinc.

[Effects of PCBs on Aegiceras corniculatum seedlings growth and membrane protective enzyme system].

With pot experiment, this paper studied the effects of PCBs (0, 180, 900, 1800 and 2700 microg x kg(-1)) on the seedlings growth and the leaves chlorophyll content, MDA content, and membrane protective enzyme system of Aegiceras corniculatum. The results showed that PCBs had definite stimulative effects on the seedlings growth. The stem height, basal stem diameter, and stem volume were all increased with increasing PCBs concentration. Within the test range of PCBs, the chlorophyll content and chlorophyll a/b ratio maintained at a relatively stable and normal level. The decrement of chlorophyll content and the increment of chlorophyll a/b ratio were less than 25% and 10% of the control, respectively. With increasing PCBs concentration, SOD activity increased first and decreased then, while POD activity and MDA content were in adverse. It was suggested that A. corniculatum could endure and adapt definite concentrations of PCBs through physiological and biochemical mechanisms, being available to the phytoremediation of PCBs pollution.