Lead Concentration in Hong Kong Roadside Dust after Reduction of Lead Level in Petrol

Samples of roadside dust were collected from 30 sites in Hong Kong.The total concentrations of 10 metals in the samples were analyzed,and the correlation coefficients among the metal contents and the annual average daily traffic(AADT)in 1986 were determined.Pb was found to have a significant correlation(P<0.01)with AADT.No correlation was found between Al, Ba,Cd,Cr,Cu,Fe,Mn,Ni,and Zn with respect to AADT.A general decrease in the level of Pb in roadside dust in the past few years has been observed since the reduction in the level of lead in petrol.1989 Academic Press,Inc.

Microalgae as Bioabsorbents for Treating Mixture of Electroplating and Sewage Effluent

The effectiveness of copper and nickel uptake by microalgae grown in the mixture of electroplating effluent and sewage was studied. The results showed that a high percentage of copper removal (68.1%-88.2%) was achieved by Chlorellapyrenoidosa (strain No. 26) reared in the mixture of 90% electroplating effluent and 10% raw sewage during the first 3 days despite the fact that cell growth was inhibited. Similar results were also obtained by using Chlorella HKBC-C3, another species collected from one of the heavy metal polluted sites in Hong Kong, isolated and cultured in the Biology Department. There was no significant difference (P>0.05) in the removal of copper and nickel from the effluent between these 2 algal species. However, it was noted that removal of nickel from the mixture by the two species were comparatively lower (<20%) than the removal of copper (>68%).

Toxicity Tests of Soil Contaminated by Recycling of Scrap Plastics

The present investigation studied the toxicity of soil contaminated by untreated discharge from a factory that recycles used plastics. The nearby agricultural areas and freshwater fish ponds were polluted with high concentrations of Cu, Ni, and Mn. Water extracts from the contaminated soil retarded root growth of Brassica chinensis (Chinese white cabbage) and Cynodon dactylon (Bermuda grass) where their seeds were obtained commercially. The contaminated populations of C. dactylon, Panicum repen (panic grass), and Imperata cylindrica (wooly grass) were able to withstand higher concentrations of Cu. Ni, and Mn, especially C. dactylon, when compared with their uncontaminated counterparts. 1990 Academic Press, Inc.

Residues of Polychlorinated Biphenyls (PCBs) in Fish, Water and Sediment from Shing Mun River

The level and pattern of contamination by polychlorinated biphenyls (PCBs) were investigated in tilapia, Oreochromis mossambicus (Peters), sediment, and water from the Shing Mun River. The range of total PCBs was 12.9 ng/g to 181.6 ng/g wet weight in tilapia, 12.7 ng/g to 46.0 ng/g freeze-dried weight in sediment, and 3.8 ng/L to 13.6 ng/L in water. The effect of biomagnification was also observed, PCB concentrations increased from water to sediment to tilapia. PCB congeners occurred in such a way that lower chlorinated PCBs comprised a higher fraction of the total PCBs in water, sediment, and tilapia muscle, whereas higher chlorinated PCBs were more commonly found only in tilapia.

Removal of Cu and Ni by Free and Immobilized Microalgae

The present investigation evaluated the effectiveness of Chlorella cells in concentrating Cu and Ni in their cells and thereby removing the two metals from solution. The removal efficiency of the two metals by free and immobilized algal cells were further studied. (1) Four types of Chlorella cells, namely Chlorella pyrenoidosa (26) (from Carolina Biological Supplies Company), Chlorella HKBC-1 and-2 (isolated from a polluted stream receiving wastewater from several electroplating factories) and Chlorella HKBC-3 (from a clean water pond) were subjected to different concentrations of Cu and Ni accordingly. It was revealed that Chlorella HKBC-1 was the most tolerant species toCu and Ni as reflected by their highest values of 48 h and 96 h 'Highest no effect concentrations' (The highest concentration of the tested substance that does not inhibit the growth rate of the alga: Cu 2 and Ni 10 mg/1 at 48 h, Cu 2 and Ni 5 at 96 h). This was followed by C. pyrenoidosa (26) and then C. HKBC-2 while C. HKBC-3 had the lowest tolerance to the two metals (Cu 0.5 and Ni 2 at 48 h; Cu 0.5 and Ni 1 mg/1 at 96 h). (2) It was further revealed that C. HKBC-1 had higher concentration factors and removal efficiencies of Ni (734-963 mg/1, 16.3-18.7%) and C. HKBC-2 had higher concentration factors and removal efficiencies of Cu (2316-2839 mg/1, 53.7-66%) when exposed to lower concentrations of Cu (0.5,1 and 2 mg/1) and Ni (5, 10 and 13 mg/1). (3) By treating the free and immobilized algal cells (algal cells entrapped in alginate beads) with different concentrations of Cu and Ni, it was observed that free cells had higher concentration factors and removal efficiencies when compared with immobilized cells (free cells: Cu 1577-3056 mg/1, 24.2-71.4%; Ni 355-849 mg/1, 4.8-18.7%; immobilized cells: Cu 453-935 mg/1, 13.9-53.2%; Ni 244-486 mg/1, 3.2-11.9%).

Morphological Changes in the Gills of Tilapia Fed Sterilized and Nonsterilized Sludge

The effects of digested sludge on the ultrastructure of gills of Sarotherodon mossambicus were investigated.Samples of digested sludge were collected from the Shatin Sewage Treatment Plant in Hong Kong and.they were (1)sun-dried(NS)or(2)sterilized in an autoclave(SS).They were then used as supplementary fish feed to cultivate the freshwater tilapia,S.mossambicus,for 50 days under laboratory conditions.The SS at low dosage(25%)had the lowest toxicity among different treatments.A swelling of lamellar epithelium,the enlargement of the subepitlaelial space,the collapse of capillaries,and the infiltration of polymorphonuclear cells in the lamellae offish gills were common to fish fed 50 to 100% NS and SS.The thickening of the basal lamina in the gill lamellae is a common feature found in the sludge-treated fish.1989 Academic Press.Inc.

Removal of Lead from Aqueous Solution by Acinetobacter calcoaceticus

A bacterial strain tolerant to the presence of 400 ppm lead was isolated from digested sewage sludge. The organism was identified as Acinetobacter calcoaceticus var: anitraus (98% confidence). Both viable and formalin-inactivated bacterial cells could remove Pb from an aqueous solution. The Pb-binding ability of inactivated cells was compared with that of a commercial ion-exchange resin, Amberlite IR-I20. The metal-binding ability of A. calcoaceticus followed the sequence Pb≥Cu≥Cr≥ (Cd, Ni, and Zn)≥Co. The ability of the inactivated cells to remove Pb was pH sensitive, and the adsorption process was slightly affected at high temperature (70℃). The adsorption and desorption process worked equally well with A. calcoaceticus embedded in a polyacrylamide gel matrix. (c)1990 Academic Press, Inc.

The Effects of Organic Ligands on the Survival of Daphnia in Zn Solution

Bioassays involving zinc alone and in combinations with two organic ligands, namely histidine and EDTA were conducted on Daphnia longispina over a period of 96 h. The percentage of mortality was recorded and the Median Lethal Concentration (LC50) at 96 h estmated. The 96 h LC50 of D. longispina in zinc solution was 91 μg/1 whereas no values of LC50 were revealed when D. longispina were exposed to histidine or EDTA alone although the organic ligands seemed to exert harmful effects (e.g. The mortality at 96 h was 18% at a concentration of 10×10^(-5) M histidine and 16% at a concentration of 6×10~6 M EDTA). However, addition of histidine and EDTA effectively reduced the toxicity of zinc to the test animals. The detoxification effect was the most obvious at the concentration of 100×g/1 Zn added with 5×10^(-5) M histidine and 3×10^(-6) M EDTA where 7-fold and 5-fold reduction in terms of mortality were noted.

Decontamination of Landfill Leachate by Soil Infiltration

A soil column study was conducted to evaluate the efficiency of soil to attenuate pollutants in landfill leachate.It was found that more than 60% of the initial alkalinity,COD,and total nitrogen was removed after the leachate had percolated through the soil column.Lower effi- ciencies were observed for the removal of dissolved cations,ammonia nitrogen,and nitrate nitrogen.When previously percolated leachate was recirculated through the soil column,sig- nificant removal(93.6%)of ammonia nitrogen was achieved.Moreover,a further reduction in COD,total nitrogen,nitrate nitrogen,and potassium was evident.Bioassay tests of seed germi- nation and root growth of Brassica chinensis were performed to compare the phytotoxicities of untreated,percolated,and recirculated leachates.The phytotoxicity was reduced by both treatments,with the greatest detoxification observed in the leachate recirculation treatment.The values ofpH and Olsen phosphorus were significantly reduced(P<0.01)in the treated column soil.whereas significant increases(P<0.05)in electrical conductivity(EC),various forms of nitrogen,exchangeable sodium percentage(ESP),potassium,magnesium,zinc,and iron were observed.EC,ESP,potassium,magnesium,sodium,iron,and various forms of nitrogen accu- mulated at the soil surface(10 cm).On the other hand,manganese was deposited at 20 to 50 cm below the soil surface of the treated column.1989 Academic Press.Inc.