Wastewater-nitrogen removal using polylactic acid/starch as carbon source: Optimization of operating parameters using response surface methodology

The use of PLA/starch blends for nitrogen removal was achieved. The influence of different operating parameters on responses was verified using RSM. The conditions for desired responses were successfully optimized simultaneously. Blends material may have a promising application prospect in the future. Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid (PLA)/starch blends as carbon source and carrier for functional bacteria. The exclusive and interactive influences of operating parameters (i.e., temperature, pH, stirring rate, and PLA-to-starch ratio (PLA proportion)) on nitrification (Y₁), denitrification (Y₂), and COD release rates (Y₃) were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous nitrification and denitrification. The carbon release rate of the blends was controllable. The sensitivity of Y₁, Y₂, and Y₃ to different operating parameters also differed. The sequence for each response was as follows: for Y₁, pH>stirring rate>PLA proportion>temperature; for Y₂, pH>PLA proportion>temperature>stirring rate; and for Y₃, stirring rate>pH>PLA proportion>temperature. In this study, the following optimum conditions were observed: temperature, 32.0°C; pH 7.7; stirring rate, 200.0 r·min^-1; and PLA proportion, 0.4. Under these conditions, Y₁, Y₂, and Y₃ were 134.0 μg-N·g-blend^-1·h^-1, 160.9 μg-N·g-blend^-1·h^-1, and 7.6 × 10³ μg-O·g-blend^-1·h^-1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.     

Genotoxicity biomarkers in the amphipod Gammarus elvirae exposed in vivo to mercury and lead,and basal levels of DNA damage in two cell types

The present work deals with the application of genotoxicity biomarkers by means of the Comet assay in haemocytes and spermatozoa of the crustacean Gammarus elvirae exposed in vivo to heavy metals. Furthermore, a basal levels (BLs) study of DNA damage in the two cell types considered for two different gammarids species, G. elvirae and Echinogammarus veneris, was carried out. It is important to identify factors that influence the outcome of the assay in order to obtain reliable and reproducible results usable for risk assessment purposes. Our results highlight that the Italian legal limits for Hg and Pb, respectively, 0.5 and 50?µg/L, are inadequate for establishing safety thresholds in the aquatic environment. Furthermore, the freshwater invertebrate G. elvirae, used for the first time to measure the effect of genotoxicants, is a good candidate for evaluating the genotoxicity damage induced by heavy metals. Our results concerning spermatozoa show excessively variable responses and high BLs.     

Bibliometric analysis of ecosystem monitoring-related research in Africa: implications for ecological stewardship and scientific collaboration

Regional ecosystem monitoring is a central form of knowledge sharing and collaboration amongst scientists and decision makers on environmental health, land use change, and science-policy development. Despite the proliferation of such research networks on long-term monitoring on many continents, little has been achieved in Africa. This study aims to assess and examine the spatiotemporal trend and categorical patterns in ecosystem monitoring-related research in Africa for the benefits of conserving biodiversity and sustaining natural resource sectors for well-being and livelihood security, environmental planning, and ecological stewardship. A systematic review was conducted using bibliometric tools. Based on a set of search terms and peer-reviewed publications retrieved from various ecosystem monitoring networks and journal databases, further analysis was conducted using social network approaches, mapping tools, and content analysis. About 1442 scientific publications on ecosystem monitoring and related research were documented from 1987 to 2014 mostly published in English. The number of publication increased progressively since 1992 after the Convention on Biodiversity was signed and this trend peaked till 2008. South African Journal of Science was the most leading journal and Nature the most cited. Internationally coauthored and collaborative articles represented majority of the findings with the United Kingdom at the central position in the research network due to colonial relationships. Regional collaboration amongst countries is limited owing to language barriers and other institutional constraints such as funding and short-term projects. These findings have implication for prioritizing national and regional policies toward biodiversity science and its contribution to human well-being, food security, and global change responses.     

冶炼企业周边农田土壤的多环芳烃污染及其细菌群落效应

多环芳烃是一类持久性有机污染物,进入土壤后可能产生多方面生态效应。为研究多环芳烃对土壤微生物的影响,选取南京某冶炼企业周边农田样品,在分析污染物含量基础上,采用高通量测序、定量PCR等方法综合评价了土壤细菌多样性和组成以及多环芳烃降解细菌丰度等特征。17个土壤样品中,多环芳烃总量为0.25~31.08 mg·kg-1,并具有随污染源距离增加而降低的空间分布特征。与土壤理化性质如p H相比较,多环芳烃污染对土壤细菌的总体多样性和群落组成影响不显著。进一步分析发现多环芳烃与潜在降解微生物的相对丰度和降解功能基因(芳香环羟基化双加氧酶,PAH-RHDα)拷贝数显著正相关。污染较重样品的克隆、测序分析表明,土壤中PAH-RHDα基因主要属于革兰氏阳性细菌nid A3/fad A1类群,且与分支杆菌相关序列较为接近。这些结果综合评价了冶炼企业周边农田土壤多环芳烃污染对微生物群落的影响,提示土壤污染在多环芳烃潜在降解细菌中的富集作用,将为后续污染土壤生物修复提供重要科学依据。     

DEHP暴露对鲤鱼肾脑生物标志物的影响

为探讨邻苯二甲酸二乙基己酯(DEHP)对鱼类肾、脑组织生物标志物的影响,将鲤鱼分别在浓度为5、20、80、160 mg·L~(-1)的DEHP水体,暴露20 d,以水和吐温-80为对照,测定肾脑组织中多种酶活性和丙二醛(MDA)含量的变化。结果表明:与水对照组相比,吐温-80组所测各项指标,差异均不显著。与水和吐温-80对照组相比,各染毒组,肾脏中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性和抗羟自由基、抗超氧阴离子的活力均显著降低(P0.05或P0.01)。谷胱甘肽过氧化物酶(GSH-Px)酶活性呈现先升高后降低,在5、20、80 mg·L~(-1)浓度组显著升高(P0.05)。丙二醛(MDA)含量在80、160 mg·L~(-1)浓度下,显著升高(P0.05),但脑组织中变化不显著。脑中一氧化氮合酶(NOS)在各浓度组显著升高(P0.05或P0.01);乙酰胆碱酯酶(ACh E)在80、160 mg·L~(-1)时降低显著(P0.05);钙调神经磷酸酶(CaN)呈先升高后降低的趋势,在20 mg·L~(-1)下,升高显著(P0.01),在80、160 mg·L~(-1)浓度组,降低极显著(P0.01);抗羟自由基、抗超氧阴离子活性均显著下降(P0.05或P0.01)。可见,在实验浓度范围内,DEHP对鲤鱼具有一定免疫毒性和神经毒性,进一步的机理有待研究。     

浓度效应对卡马西平在生物炭上的吸附动力学影响

为了解人工合成药物在生物炭上的吸附动力学特征及其浓度效应的影响,选择卡马西平(CBZ)为目标污染物。探讨不同初始质量浓度(2、4、25、50 mg·L~(-1))在不同裂解温度(200、300、500℃)下制备的生物炭上的吸附动力学特征。结果表明,双室一级动力学模型可以精确地描述CBZ在生物炭上的吸附动力学特征。CBZ的快室吸附对总体吸附的贡献随初始浓度的增大而减小,而慢室吸附贡献则增大。π-π作用可能对CBZ的吸附贡献较大。孔隙填充可以描述慢室吸附过程,可能是吸附速率的控制环节。     

Photochemical indicators of ozone sensitivity: application in the Pearl River Delta,China

Surface O₃ production has a highly nonlinear relationship with its precursors. The spatial and temporal heterogeneity of O₃-NO _x -VOC-sensitivity regimes complicates the control-decision making. In this paper, the indicator method was used to establish the relationship between O₃ sensitivity and assessment indicators. Six popular ratios indicating ozone-precursor sensitivity, HCHO/NO _y , H₂O₂/ HNO₃, O₃/NO _y , O₃/NO _z , O₃/HNO₃, and H₂O₂/NO _z , were evaluated based on the distribution of NO_x- and VOC-sensitive regimes. WRF-Chem was used to study a serious ozone episode in fall over the Pearl River Delta (PRD). It was found that the south-west of the PRD is characterized by a VOCsensitive regime, while its north-east is NO _x -sensitive, with a sharp transition area between the two regimes. All indicators produced good representations of the elevated ozone hours in the episode on 6 November 2009, with H₂O₂/HNO₃ being the best indicator. The threshold sensitivity levels for HCHO/NO_y, H₂O₂/HNO₃, O₃/NO _y , O₃/NO _z , O₃/HNO₃, and H₂O₂/NO _z were estimated to be 0.41, 0.55, 10.2, 14.0, 19.1, and 0.38, respectively. Threshold intervals for the indicators H₂O₂/HNO₃, O₃/NO _y , O₃/NO _z , O₃/HNO₃, and H₂O₂/NO _z were able to identify more than 95% of VOC- and NO _x -sensitive grids. The ozone episode on 16 November 16 2008 was used to independently verify the results, and it was found that only H₂O₂/HNO₃ and H₂O₂/NO _z were able to differentiate the ozone sensitivity regime well. Hence, these two ratios are suggested as the most appropriate indicators for identifying fall ozone sensitivity in the PRD. Since the species used for indicators have seasonal variation, the utility of those indicators for other seasons should be investigated in the future work.

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Diversity of crude oil-degrading bacteria and alkane hydroxylase (<Emphasis Type="Italic">alkB</Emphasis>) genes from the Qinghai-Tibet Plateau

The aim of this study was to survey the response of the microbial community to crude oil and the diversity of alkane hydroxylase (alkB) genes in soil samples from the Qinghai-Tibet Plateau (QTP). The enrichment cultures and clone libraries were used. Finally, 53 isolates and 94 alkB sequences were obtained from 10 pristine soil samples after enrichment at 10 °C with crude oil as sole carbon source. The isolates fell into the phyla Proteobacteria, Actinobacteria, and Bacteroidetes, with the dominance of Pseudomonas and Acinetobacter. The composition of degraders was different from polar habitats where Acinetobacter sp. is not a predominant responder of alkane degradative microbial communities. Phylogenetic analysis showed that the alkB genes from isolates and enrichment communities formed eight clusters and mainly related with alkB genes of Pseudomonas, Rhodococcus, and Acinetobacter. The alkB gene diversity in the QTP was lower than marine environments and polar soil samples. In particular, a total of 10 isolates exhibiting vigorous growth with crude oil could detect no crude oil degradation-related gene sequences, such as alkB, P450, almA, ndoB, and xylE genes. The Shannon-Wiener index of the alkB clone libraries from the QTP ranged from 1.00 to 2.24 which is similar with polar pristine soil samples but lower than that of contaminated soils. These results indicated that the Pseudomonas, Acinetobacter, and Rhodococcus genera are the candidate for in situ bioremediation, and the environment of QTP may be still relatively uncontaminated by crude oil.     

Assessment of urban sustainability efficiency based on general data envelopment analysis: a case study of two cities in western and eastern China

Sustainable urban development focuses on enhancing urban well-being, while also balancing the demands of urban social and economic development, natural resource consumption, and environmental pollution. This work used general data envelopment analysis to assess the urban sustainability efficiency (USE) and sustainability potential (SP) in Lanzhou and Xiamen, two cities that are characteristic of urban areas in western and eastern China. The assessment indicator system included important natural and urban welfare factors as input and output indices, respectively. The results showed that overall urban sustainability efficiency increased in Lanzhou and Xiamen from 1985 to 2010, but that the sustainability of natural resources clearly decreased. The urban sustainability efficiency of Xiamen was higher than that of Lanzhou, and the sustainability potential of Xiamen was lower than that of Lanzhou; this indicates that Xiamen performed better in terms of urban sustainable development. The urban sustainability efficiency in Xiamen has increased with increasing urban population, and the rate and scale of economic development have been higher than in Lanzhou. The assessment and analysis performed in this study show that cities with different natural resources and development characteristics have different forms, patterns, and trajectories of sustainable development.