Long-term temporal-spatial dynamics of marine coastal water quality in the Tolo Harbor,Hong Kong,China

The long-term temporal and spatial dynamics of marine coastal water quality in Tolo Harbor, Hong Kong were explored. The Harbor is divided into three zones represented as Harbor, Buffer, and Channel Subzones. The time range for the study covers the period from the 1970s to the 1990s. The selected indicators for the comprehensive assessment of water quality consist of physical, chemical and biological aspects, including suspended solids(SS), Secchi disk depth(SD), 5-day biochemical oxygen demand(BOD\-5), total nitrogen(TN), total phosphorus(TP), faecal coliform, chlorophyll-a(Chl-a), and the number of red tide occurrences. The results indicated the presence of obvious temporal and spatial trends with regard to changes in water quality. Spatially, water quality in the Channel Subzone is the best, while that in the Harbor Subzone is the worst. On a temporal basis, the average trend from bad to good was 1980s>1990s>1970s as indicated by most of the selected water quality indicators. Water quality during the late 1980s reached its worst level with the lowest SD, the highest BOD\-5, TN, TP, Chl-a concentrations, and the number of red tide occurrences. These long-term temporal-spatial water quality trends were also found in other studies of the Tolo Harbor. The large quantity of pollutants produced as a result of increasing population, industrial and commercial actives, and urbanization and industrialization trends in both Shatin and Tai Po seem to be primarily responsible for the changes in marine coastal water quality.

Thermodynamics of phenanthrene partition into solid organic matter from water

The thermodynamic behavior of organic contaminants in soils is essential to develop remediation technologies and assess risk from alternative technologies. Thermodynamics of phenanthrene partition into four solids(three soils and a bentonite) from water were investigated. The thermodynamics parameters(ΔH, ΔG o, ΔS o,) were calculated according to experimental data. The total sorption heats of phenanthrene to solids from water ranged from -7.93 to -17.1 kJ/mol, which were less exothermic than the condensation heat of phenanthrene-solid(i.e., -18.6 kJ/mol). The partition heats of phenanthrene dissolved into solid organic matter ranged from 23.1 to 32.2 kJ/mol, which were less endothermic than the aqueous dissolved heat of phenanthrene(i.e., 40.2 kJ/mol), and were more endothermic than the fusion heat of phenanthrene-solid(i.e., 18.6 kJ/mol). The standard free energy changes, ΔG o, are all negative which suggested that phenanthrene sorption into solid was a spontaneous process. The positive values of standard entropy changes, ΔS o, show a gain in entropy for the transfer of phenanthrene at the stated standard state. Due to solubility-enhancement of phenanthrene, the partition coefficients normalized by organic carbon contents decrease with increasing system temperature(i.e., lnK oc =-0.284lnS+9.82(n=4, r 2=0.992)). The solubility of phenanthrene in solid organic matter increased with increasing temperatures. Transports of phenanthrene in different latitude locations and seasons would be predicted according to its sorption thermodynamics behavior.

Characterization of Anabaena cylindrica Solution System Using Synchronous-Scan Fluorescence Spectroscopy

The characterization of the algae Anabaena cylindrical solution with Fe (III)was investigated using fluorescence emission and synchronous-scan spectroscopy. The ranges ofconcentrations of algae and Fe (III) in aqueous solutions were 5.0 X 10~7-2.5 X10^8 cell/L and 10-60mu mol/L, respectively. The effective characterization method used was synchronous-scanfluorescence spectroscopy (SFS). The wavelength difference (triangle open lambda) of 90 nm wasmaintained between excitation wavelength (lambda_(ex)) and emissionwavelength(lambda_(em)). The peakwas observed at about lambda_(ex) 236 nm / lambda_(em) 326 nm for synchronous-scan fluorescencespectroscopy. The fluorescence quenching in system of algae-Fe( III )-HA was studied usingsynchronous-scan spectroscopy forthe first time, Fe(III) was clearly the effective quencher. Therelationship between I_0/I (quenching efficiency) and c (concentration of Fe (III). added) was alinear correlation for the algae solution with Fe(III). Also, Aldrich humic acid (HA) was found tobe an effective quencher.

Determination of trophic relationships within a Bohai Bay food web using stable δ^(15)N and δ^(13)C analysis

This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from ?25.38‰ to ?11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ 13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ 15N ranged from 4.08‰ to 13.98‰, and showed a step-wise en- richment with trophic level of 3.8‰. The δ 15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46?2.10, 1.91?3.32, 2.55?4.23 and 2.98?4.28 for plankton, invertebrates, fishes, and seabirds.