Field test of best management practice pollutant removal efficiencies in Shenzhen, China

This paper presents a study on the use of best management practices (BMPs) for controlling nonpoint pollution in the Xikeng Reservoir watershed located in Shenzhen, China. A BMP treatment train design, including a pond, a wetland, and a buffer strip placed in series was implemented at the reservoir location. A separate grass swale was also constructed at the site. Low impact development (LID) BMPs, namely a planter box and bioboxes, were used at the parking lot of the reservoir’s Administration Building. Samples were collected during storm events and were analyzed for total suspended solids (TSS), biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃—N), and total phosphorus (TP). The removal efficiencies of both BMP systems were evaluated using the Efficiency Ratio (ER) method based on the event mean concentration (EMC) data. In summary, the pond/wetland treatment train removed 70%―90% of TSS, 20%―50% of BOD₅, and 30%―70% of TP and NH₃—N. The swale removed 50%―90% of TSS, 30%―55% of BOD₅, −10%―35% of NH₃—N, and 25%―70% of TP. For the planter box and biobox, the ranges of removal rates were 70%―90%, 20%―50%, and 30%―70% for TSS, BOD₅, and ammonia and phosphorus, respectively.     

Hydrologic and water quality performance of a laboratory scale bioretention unit

A bioretention unit (BRU) or cell is a green infrastructure practice that is widely used as a low impact development (LID) technique for urban stormwater management. Bioretention is considered a good fit for use in China’s sponge city construction projects. However, studies on bioretention design, which incorporates site-specific environmental and social-economic conditions in China are still very much needed. In this study, an experimental BRU, consisted of two cells planted with Turf grass and Buxus sinica,was tested with eighteen synthesized storm events. Three levels (high, median, low) of flows and concentrations of pollutants (TN, TP and COD) were fed to the BRU and the performance of which was examined. The results showed that the BRU not only delayed and lowered the peak flows but also removed TN, TP and COD in various ways and to different extents. Under the high, medium and low inflow rate conditions, the outflow peaks were delayed for at least 13 minutes and lowered at least 52%. The two cells stored a maximum of 231 mm and 265 mm for turf grass and Buxus sinica, respectively. For both cells the total depth available for storage was 1,220 mm, including a maximum 110 mm deep ponding area. The largest infiltrate rate was 206 mm/h for both cells with different plants. For the eighteen events, TP and COD were removed at least 60% and 42% by mean concentration, and 65% and 49% by total load, respectively. In the reservoir layer, the efficiency ratio of removal of TN, TP and COD were 52%, 8% and 38%, respectively, within 5 days after runoff events stopped. Furthermore, the engineering implication of the hydrological and water quality performances in sponge city construction projects is discussed.

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Linking human security to natural resources: perspective from a fishery resource allocation system in Chilika lagoon, India

Human security is linked to people’s access to natural resources and vulnerabilities to environmental change. In the case study of Chilika lagoon, the findings reveal that insecurity linked to natural resources is largely embedded in the historical process of resource allocation among stakeholders, rather than on the presence of resource stocks. The insecurities are strongly tied not only to allocation changes, but also to multiple factors (environmental, technological, and demographic factors). Based on the Chilika lagoon experience, this article develops a pathway toward a clear understanding of the linkage between human security and natural resources in a local context.     

Relationships between steric factors and bioconcentration of polychlorinated biphenyls (PCB's) by the sea mullet (Mugil cephalus Linnaeus)

Isolation of the polychlorinated biphenyls (PCB's) from sea mullet (Mugil cephalus) collected in the Brisbane River estuary indicated that these corresponded approximately to the Arochlor Grade 1260, although minor amounts of Grade 1254 were present. However the composition of the isolates similar to the 1260 Grade in all cases exhibited marked differences between the proportions of individual components present in the original mixture as compared to the mixture found in the fish. The number of chlorines in a PCB compound has an influence on bioconcentration, but with isomers it is suggested that variable uptake of the different PCB's occurs principally as a result of steric effects relating to the orientation of the two phenyl rings and the patterns of substitution of chlorine. A Steric Effect Coefficient has been empirically developed which correlates closely with relative uptake of PCB isomers.     

Photochemical production of ozone and control strategy for Southern Taiwan

An observation-based method (OBM) is developed to evaluate the ozone (O₃) production efficiency (O₃ molecules produced per NO_x molecule consumed) and O₃ production rate (P(O₃)) during a field campaign in southern Taiwan. The method can also provide an estimate of the concentration of OH. A key step in the method is to use observed concentrations of two aromatic hydrocarbons, namely ethylbenzene and m,p-xylene, to estimate the degree of photochemical processing and amounts of photochemically consumed NO_x and NMHCs by OH. In addition, total oxidant (O₃+NO₂) instead of O₃ itself turns out to be very useful for representing ozone production in the OBM approach. The average O₃ production efficiency during the field campaign in Fall (2003) is found to be about 10.2±3.9. The relationship of P(O₃) with NO_x is examined and compared with a one-dimensional (1D) photochemical model. Values of P(O₃) derived from the OBM are slightly lower than those calculated in the 1D model. However, OH concentrations estimated by the OBM are about a factor of 2 lower than the 1D model. Fresh emissions, which affect the degree of photochemical processing appear to be a major cause of the underestimate. We have developed a three-dimensional (3D) OBM O₃ production diagram that resembles the EKMA ozone isopleth diagram to study the relationship of the total oxidant versus O₃ precursors. The 3D OBM O₃ production diagram suggests that reducing emissions of NMHCs are more effective in controlling O₃ than reducing NO_x. However, significant uncertainties remain in the OBM, and considerable more work is required to minimize these uncertainties before a definitive control strategy can be reached. The observation-based approach provides a good alternative to measuring peroxy radicals for evaluating the production of O₃ and formulating O₃ control strategy in urban and suburban environments.     

A method to determine residue levels of persistent organochlorine pesticides in human milk from Indonesian women

A method has been developed for the analysis of organochlorine pesticides in human milk using solvent extraction, Florisil solid phase extraction clean-up and analysis by gas chromatography with an electron capture detector. The recovery of analytes from spiked milk samples was in the range 53 +/- 1% to 109 +/- 7% (n = 9). A small number of samples were obtained from women in a rural and an urban area of Indonesia and analysed using the developed method. The results are reported on a milk fat basis. All samples contained detectable residues of p,p'-DDT (urban mean 0.11 +/- 0.18 mgkg(-1) (n = 5), rural mean 0.07 +/- 0.03 mg kg(-1) (n = 5)) and p,p'-DDE (urban mean 0.05 +/- 0.04 m kg(-1) (n = 5), rural mean 0.76 +/- 1.46 mg kg(-1) (n = 5)). Residues of HCB, betaHCH, alpha-endosulfan and dieldrin were also detected in some samples. There was no significant difference (at the 95% confidence level) in levels of pesticides between urban and rural areas. The levels of organochlorine pesticides in milk from Indonesian women were lower than those reported from Indonesian women exposed to DDT through malaria eradication schemes and were similar to levels reported from UK and Japan.     

Nuptial feeding of spermless spermatophores in the Hawaiian swordtail cricket, Laupala pacifica (Gryllidae: Triginodiinae)

Crickets in the genus Laupala (subfamily Trigonidiinae) have an elaborate courtship system, defined by a highly ritualized serial transfer of multiple spermatophores. Males produce multiple “micro” spermatophores followed by a final “macro” spermatophore during a single mating bout. Remarkably, the microspermatophores of L. cerasina, the first species whose mating system was studied in detail, were discovered to be spermless. However, in a study of another species, L. pacifica, sperm transfer was reported after every copulation suggesting that L. pacifica microspermatophores contain sperm. The presence or absence of sperm in the microspermatophore has important implications for the evolution of this exaggerated courtship system and the origin of nuptial gifts. In this study, we systematically examined L. pacifica spermatophore contents for sperm using a fluorescent nuclear stain. We detected sperm only in macrospermatophores. This finding suggests that spermless microspermatophores are typical for Laupala; thus, to determine the origin of this highly modified phenotype will require comparative analyses with closely related outgroups that exhibit less exaggerated courtship systems.