Urbanization,land use,and water quality in Shanghai. 1947-1996

The paper undertakes a preliminary investigation into the relationship between water quality and urbanization as well as the changing patterns of land use within Shanghai. Longitudinal changes to water quality at various points along the course of the Huangpu River are analysed and compared to changes in the rates of urbanization and changes in land uses. The results reveal that rapid urbanization corresponds with rapid degradation of water quality. It also shows that urban land uses are positively correlated with the decline in water quality. A regression model shows that close to 94% of the variability in water quality classifications is explained by industrial land area. The paper concludes with the need for comprehensive land use planning as a way of protecting valuable water resources.     

Incomplete oxidation of ethylenediaminetetraacetic acid in chemical oxygen demand analysis.

Ethylenediaminetetraacetic acid (EDTA) was found to incompletely oxidize in chemical oxygen demand (COD) analysis, leading to incorrect COD values for water samples containing relatively large amounts of EDTA. The degree of oxidation depended on the oxidant used, its concentration, and the length of digestion. The COD concentrations measured using COD vials with a potassium dichromate concentration of 0.10 N (after dilution by sample and sulfuric acid) were near theoretical oxygen demand values. However, COD measured with dichromate concentrations of 0.010 N and 0.0022 N were 30 to 40% lower than theoretical oxygen demand values. Similarly, lower COD values were observed with manganic sulfate as oxidant at 0.011 N. Extended digestion yielded somewhat higher COD values, suggesting incomplete and slower oxidation of EDTA, as a result of lower oxidant concentrations. For wastewater in which EDTA is a large fraction of COD, accurate COD measurement may not be achieved with methods using dichromate concentrations less than 0.1 N.     

Effects of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites on cricket (Acheta domesticus) survival and reproductive success

The effect of two major hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) metabolites, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX), on cricket (Acheta domesticus) survival and reproduction was studied. RDX metabolites did not have adverse effects on cricket survival, growth, and egg production. However, MNX and TNX did affect egg hatching. MNX and TNX were more toxic in spiked-sand than in topical tests. TNX was more toxic to egg than MNX. Developmental stage and exposure time affected hatching. After 30 days exposure to MNX or TNX, the EC20, EC50, and EC95 were 47, 128, and 247 microg/g for TNX, and 65, 140, and 253 microg/g for MNX in topical tests. The ECs for 20, 50, and 95 were 21, 52, and 99 microg/g for MNX, and 12, 48, and 97 microg/g for TNX in sand. No gross abnormalities in cricket nypmhs were observed in all experiments indicating that neither TNX or MNX is teratogenic in this assay.     

Toxicity of the explosive metabolites hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) and hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) to the earthworm Eisenia fetida

Toxicity of hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) to earthworm was evaluated. Both MNX and TNX had lethal and sublethal effects on earthworms. Exposure to MNX- or TNX-contaminated soil caused a significant concentration-dependent decrease in earthworm survival and growth. The lowest observed lethal concentration (LOLC) for both MNX and TNX was 100 and 200 mgkg(-1) soil dry weight in the sandy loam soil and in the silt loam soil, respectively. No earthworms survived for 14 days in MNX- or TNX-spiked soil at 500 mgkg(-1) soil dry weight. After 7 days exposure, the lowest observed effect concentration (LOEC) for earthworm growth was 50 mgkg(-1) soil dry weight for TNX and 100 mgkg(-1) soil dry weight for MNX in both soil types. The LC20 and LC50 for MNX in sandy loam soil were 114 and 262 mgkg(-1) and for TNX, they were 114 and 254 mgkg(-1) soil dry weight, respectively. The corresponding values for MNX and TNX in silt loam soil were 234 and 390 mgkg(-1) soil dry weight, respectively, and 200 and 362 mgkg(-1) soil dry weight, respectively. After 35 days exposure, earthworm growth was reduced 8-39% by TNX in sandy loam soil, whereas TNX only inhibited earthworm growth 5-18% at the same concentration range in silt loam soil. LC20 and LC50 for TNX were slightly lower than for MNX; this indicates that TNX was more toxic than MNX. No significant morphological or developmental abnormalities were observed in earthworms surviving exposure.     

Uptake, accumulation and depuration of sodium perchlorate and sodium arsenate in zebrafish (Danio rerio)

In toxicokinetics studies, interactions between chemicals in mixtures has been largely neglected. This study examines a mixture of perchlorate and arsenate because (1) they have the potential to co-occur in contaminated aquatic habitats, and (2) a previous study by the authors found possible toxicological interactive effects. In the present study, zebrafish (Danio rerio) were exposed to two concentrations of sodium perchlorate (10 and 100 mg l(-1)), sodium arsenate (1 and 10 mg l(-1)), and the mixture-sodium perchlorate+sodium arsenate (10+1 mg l(-1) and 100+10 mg l(-1) Na(2)HAsO(4)-high mixture) for 90 d. Their uptake and accumulation by zebrafish was evaluated at 10, 30, 60, and 90 d. In addition, depuration was examined at 1, 3, and 5d after cessation of the exposure. The uptake of either chemical was concentration-dependent, with significantly higher uptake at high concentrations at either exposure interval. In contrast, there was no significant difference in whole body residue between single chemicals and the corresponding mixture except for 100 mg l(-1) sodium arsenate at 90 d. However, there was increasing accumulation over time at the high concentration of either chemical alone and their mixture, and this increasing trend was more pronounced in the single chemical exposures than in the mixture. At the concentrations tested in the current study, both chemicals reduced the uptake but enhanced the depuration of the other chemical from the zebrafish. This study represents the first examination of the interaction of two anions-perchlorate and arsenate with respect to toxicokinetics.     

Horizon scanning for South African biodiversity: A need for social engagement as well as science

Ambio - A horizon scan was conducted to identify emerging and intensifying issues for biodiversity conservation in South Africa over the next 5–10 years. South African biodiversity...     

Sources of dioxins in the United Kingdom: the steel industry and other sources

Several countries have compiled national inventories of dioxin (polychlorinated dibenzo-p-dioxin [PCDD] and polychlorinated dibenzofuran [PCDF]) releases that detail annual mass emission estimates for regulated sources. High temperature processes, such as commercial waste incineration and iron ore sintering used in the production of iron and steel, have been identified as point sources of dioxins. Other important releases of dioxins are from various diffuse sources such as bonfire burning and domestic heating. The PCDD/F inventory for emissions to air in the UK has decreased significantly from 1995 to 1998 because of reduced emissions from waste incinerators which now generally operate at waste gas stack emissions of 1 ng I-TEQ/Nm3 or below. The iron ore sintering process is the only noteworthy source of PCDD/Fs at integrated iron and steelworks operated by Corus (formerly British Steel plc) in the UK. The mean waste gas stack PCDD/F concentration for this process is 1,2 ng I-TEQ/Nm3 based on 94 measurements and it has been estimated that this results in an annual mass release of approximately 38 g I-TEQ per annum. Diffuse sources now form a major contribution to the UK inventory as PCDD/Fs from regulated sources have decreased, for example, the annual celebration of Bonfire Night on 5th November in the UK causes an estimated release of 30 g I-TEQ, similar to that emitted by five sinter plants in the UK.     

Gladius and its derivatives as potential biosorbents for marine diesel oil

The demand for low cost and effective materials to remove contaminants such as residues of oil spills has encouraged studies on new biosorbents produced from wastes. Considering the overgeneration of fishing residues and the necessity to provide an alternative purpose for such materials, this study aimed to evaluate squid gladius and its derivatives (β-chitin and chitosan) as sorbents to remove marine diesel oil (MDO) from fresh and artificial seawater. It was also executed an attempted to improve their performances through a high-intensity ultrasound treatment (UT-gladius and UT-β-chitin). All sorbents removed MDO at both salinities. Contact surface area, salinity, and water retention seemed to play a key role in the outcomes. UT-β-chitin’s performance was significantly superior to β-chitin’s and chitosan’s in MDO removal at salinity 0, as well as at salinity 30, where gladius and UT-gladius also excelled. Ultrasound treatment improved the oil removal performance of UT-β-chitin by increasing its contact surface area. This is the first report on the efficiency of gladius and UT-β-chitin for such purpose, and brought up huge possibilities and new questions that can lead to the achievement of biosorbents of great efficiency.     

Effects of suspended and sedimented clays on juvenile hard clams,<Emphasis Type="Italic"> Mercenaria mercenaria</Emphasis>, within the context of harmful algal bloom mitigation

Increased interest in using ecologically inert clays to flocculate, sediment, and thus mitigate harmful algal blooms at nearshore mariculture sites has prompted studies on the effectiveness of this method on prolific blooms, such as those caused by the neurotoxic dinoflagellate Karenia brevis in the Gulf of Mexico. Potential repercussions of this control strategy revolve around the increased flux of suspended particles to the benthos. Juvenile suspension-feeding bivalves are potentially vulnerable as they could suffer burial, a decrease in clearance rates, and/or an increase in pseudofeces production in response to suspended clay, leading to reduced growth and delay in attaining size refuge from predators. Here we assess lethal and sublethal effects on juvenile hard clams, Mercenaria mercenaria, in a 2-week flume application of phosphatic clay to simulated blooms of the nontoxic dinoflagellates Heterocapsa triquetra and Prorocentrum micans. Flow regimes simulated two contrasting, worst-case field conditions where (1) low flow allowed complete sedimentation and formation of a benthic sediment layer, and (2) high flow allowed complete particle suspension. No clam mortalities occurred in either treatment. The sedimentation treatment showed variable growth inhibition in shell and/or tissue, but effects were not apparent compared to controls (no sediment layer), and clams rapidly resumed siphon contact with the overlying water column. In contrast, a strong growth effect (~90% reduction in shell and tissue growth) occurred in particle-suspension trials compared to no-clay controls. These results suggest that repeated clay applications in the field are likely more detrimental to clams in a high-energy environment leading to prolonged in situ resuspension of clay than in an environment favoring sedimentation.Communicated by R.J. Thompson, St. Johns     

Effects of kinship on growth of a live-bearing reef fish

The influence of genetic relatedness on the individual performance (e.g. growth, development) of animals is often tied to agonistic or cooperative behaviors among conspecifics, and studies of the effects of kinship have produced mixed results. To explore genetic relatedness independent of these behaviors, we investigated the effects of kinship on the growth of the kelp perch Brachyistius frenatus, a live-bearing, planktivorous marine reef fish that is capable of only limited dispersal. Although juveniles occur in aggregations and compete for food resources, they do not exhibit overt aggressive or cooperative behavioral interactions. We hypothesized that under competition and in the absence of these behaviors, sibling and non-sibling groups of juvenile B. frenatus raised at the same densities in the field would not differ in average growth, but that siblings would exhibit lower variation in growth, simply due to genetic similarities in inherent growth rates. Pregnant, female kelp perch were collected and placed in cages until parturition was complete. Groups of young, recently born from the same mother or from different mothers, were then raised in the field for 9 wk. Our results revealed that average growth rates were similar between sibling and non-sibling treatments. While variation in growth increased initially in non-siblings, siblings showed little such variation. This divergence, however, was not consistent over the duration of the experiment, and variation in the growth of siblings ultimately converged with that of non-siblings. Effects of genetic relatedness would be most likely to manifest themselves early after birth, before environmental factors exert their influence, and this may explain the initial separation but eventual convergence in variation in growth between sibling and non-sibling treatments. For B. frenatus and other organisms that will encounter relatives and compete for resources without overt behavioral interactions, the degree of kinship may play a minor role in the demography of local populations. Received: 26 January 1998 / Accepted: 30 September 1998