Kinetic and mechanism studies of the adsorption of lead onto waste cow bone powder (WCBP) surfaces

This study examines the adsorption isotherms, kinetics and mechanisms of Pb2(+) sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb2(+) in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb2(+) with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca2(+) and PO?3? concentrations during the metal sorption processes. The Pb2(+) sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb(+). The sorption isotherm results indicated that Pb2(+) sorption onto the Langmuir and Freundlich constant q(max) and K( F ) is 9.52 and 8.18 mg g?1, respectively. Sorption kinetics results indicated that Pb2(+) sorption onto WCBP was pseudo-second-order rate constants K? was 1.12 g mg?1 h?1. The main mechanism is adsorption or surface complexation (≡POPb(+): 61.6%), co-precipitation or ion exchange [Ca?(.)?? Pb?(.)?? (PO?)? (OH): 21.4%] and other precipitation [Pb 50 mg L?1 and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb2(+) removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb2(+) indicates its potential as another promising way to remediate Pb2(+)-contaminated media.     

Potential application of sludge produced from coal mine drainage treatment for removing Zn(II) in an aqueous phase

Various analyses of physico-chemical characteristics and batch tests were conducted with the sludge obtained from a full-scale electrolysis facility for treating coal mine drainage in order to find the applicability of sludge as a material for removing Zn(II) in an aqueous phase. The physico-chemical analysis results indicated that coal mine drainage sludge (CMDS) had a high specific surface area and also satisfied the standard of toxicity characteristic leaching procedure (TCLP) because the extracted concentrations of certain toxic elements such as Pb, Cu, As, Hg, Zn, and Ni were much less than their regulatory limits. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the CMDS mainly consists of goethite (70%) and calcite (30%) as a weight basis. However, the zeta potential analysis represented that the CMDS had a lower isoelectric point of pH (pH(IEP)) than that of goethite or calcite. This might have been caused by the complexation of negatively charged anions, especially sulfate, which usually exists with a high concentration in coal mine drainage. The results of Fourier transform infrared (FT-IR) spectrometry analysis revealed that Zn(II) was dominantly removed as a form of precipitation by calcite, such as smithsonite [ZnCO?] or hydrozincite [Zn?(CO?)?(OH)?]. Recycling sludge, originally a waste material, for the removal process of Zn(II), as well as other heavy metals, could be beneficial due to its high and speedy removal capability and low economic costs.     

超声气浮+SBR工艺在小城镇垃圾场渗滤液处理中的应用

根据小城镇垃圾渗滤液特点，采用超声气浮技术并加以SBR生化处理工艺进行脱氮处理，处理后氮氮，CODcr,BOD5,悬浮物均达标排放。具有操作简单，灵活，处理成本低，设施可整体搬移的特点，非常适合小城镇小型垃圾卫生填埋场使用。     

Response surface modeling-based source contribution analysis and VOC emission control policy assessment in a typical ozone-polluted urban Shunde, China

To develop a sound ozone (O₃) pollution control strategy, it is important to well understand and characterize the source contribution due to the complex chemical and physical formation processes of O₃. Using the “Shunde” city as a pilot summer case study, we apply an innovative response surface modeling (RSM) methodology based on the Community Multi-Scale Air Quality (CMAQ) modeling simulations to identify the O₃ regime and provide dynamic analysis of the precursor contributions to effectively assess the O₃ impacts of volatile organic compound (VOC) control strategy. Our results show that Shunde is a typical VOC-limited urban O₃ polluted city. The “Jiangmen” city, as the main upper wind area during July 2014, its VOCs and nitrogen oxides (NO_x) emissions make up the largest contribution (9.06%). On the contrary, the contribution from local (Shunde) emission is lowest (6.35%) among the seven neighbor regions. The local VOCs industrial source emission has the largest contribution comparing to other precursor emission sectors in Shunde. The results of dynamic source contribution analysis further show that the local NO_x control could slightly increase the ground O₃ under low (10.00%) and medium (40.00%) reduction ratios, while it could start to turn positive to decrease ground O₃ under the high NO_x abatement ratio (75.00%). The real-time assessment of O₃ impacts from VOCs control strategies in Pearl River Delta (PRD) shows that the joint regional VOCs emission control policy will effectively reduce the ground O₃ concentration in Shunde.     

Model for Prioritizing Best Management Practice Implementation: Sediment Load Reduction

Understanding the best way to allocate limited resources is a constant challenge for water quality improvement efforts. The synoptic approach is a tool for geographic prioritization of these efforts. It uses a benefit-cost framework to calculate indices for functional criteria in subunits (watersheds, counties) of a region and then rank the subunits. The synoptic approach was specifically designed to incorporate best professional judgment in cases where information and resources are limited. To date, the synoptic approach has been applied primarily to local or regional wetland restoration prioritization projects. The goal of this work was to develop a synoptic model for prioritizing watersheds within which suites of agricultural best management practices (BMPs) can be implemented to reduce sediment load at the watershed outlets. The model ranks candidate watersheds within an ecoregion or river basin so that BMP implementation within the highest ranked watersheds will result in the most sediment load reduction per conservation dollar invested. The model can be applied anywhere and at many scales provided that the selected suite of BMPs is appropriate for the evaluation area’s biophysical and climatic conditions. The model was specifically developed as a tool for prioritizing BMP implementation efforts in ecoregions containing watersheds associated with the USDA-NRCS conservation effects assessment project (CEAP). This paper presents the testing of the model in the little river experimental watershed (LREW) which is located near Tifton, Georgia, USA and is the CEAP watershed representing the southeastern coastal plain. The application of the model to the LREW demonstrated that the model represents the physical drivers of erosion and sediment loading well. The application also showed that the model is quite responsive to social and economic drivers and is, therefore, best applied at a scale large enough to ensure differences in social and economic drivers across the candidate watersheds. The prioritization model will be used for planning purposes. Its results are visualized as maps which enable resource managers to identify watersheds within which BMP implementation would result in the most water quality improvement per conservation dollar invested.     

A Statistical Sediment Yield Prediction Model Incorporating the Effect of Fires and Subsequent Storm Events1

Abstract: Alluvial fans are continuously being developed for residential, industrial, commercial, and agricultural uses in southern California. Development and alteration of alluvial fans need to consider the possibility of mud and debris flows from upstream mountain watersheds affected by fires. Accurate prediction of sediment yield (or hyper‐concentrated sediment yield) is essential for the design, operation, and maintenance of debris basins to safeguard properly the general populace. This paper presents a model for the prediction of sediment yields that result from a combination of fire and subsequent storm events. The watersheds used in this analysis are located in the foothills of the San Gabriel Mountains in southern California. A multiple regression analysis is first utilized to establish a fundamental statistical relationship for sediment yield as a function of relief ratio, drainage area, maximum 1‐h rainfall intensity and fire factor using 45 years of data (1938‐1983). In addition, a method for multi‐sequence sediment yield prediction under fire conditions was developed and calibrated using 17 years of sediment yield, fire, and precipitation data for the period 1984‐2000. After calibration, this model was verified by applying it to provide a prediction of the sediment yields for the 2001‐2002 fire events in southern California. The findings indicate a strong correlation between the estimated and measured sediment yields. The proposed method for sequence sediment yield prediction following fire events can be a useful tool to schedule cleanout operations for debris basins and to develop an emergency response strategy for the southern California region where plentiful sediment supplies exist and frequent fires occur.     

Characteristic behavior of peroxyacetyl nitrate (PAN) in Seoul megacity, Korea

We measured the concentrations of peroxyacetyl nitrate (PAN) and other photochemically reactive species, including O(3), NO(2), and non-methane hydrocarbons (NMHCs), in the Seoul Metropolitan area (SMA) during May through June in 2004 and 2005. PAN was determined using a fast chromatograph with luminol-based chemiluminescence detection. Mixing ratios of PAN ranged from below the detection limit (0.1ppbv) to 10.4ppbv with an average of 0.8ppbv. O(3) concentrations ranged from 0 to 141ppbv. The average PAN/O(3) ratio of 0.07 was higher than that observed in cities of Europe and North America (0.02) where control strategies have been enforced to reduce hydrocarbon emissions through extensively reformulated gasoline programs. Strong positive correlations between daily PAN and O(3) maxima during the day demonstrate that similar photochemical factors controlled the production of these two chemicals. However, relationships between PAN and its precursors, NO(2) and NMHCs, suggest that PAN production was more sensitive to NO(2) than NMHCs levels whereas O(3) production was limited by the overall availability of NMHCs. It is likely that the compositions of NMHCs in SMA were favorable for PAN production because of the low fractions of oxygenated compounds in automobile fuels. PAN maxima were observed around noon, which was 2-3h earlier than the much broader O(3) maxima that occurred in the midafternoon. After reaching the maximum, PAN concentrations rapidly dropped within a few hours, which could be largely due to thermal destruction and to limited production under the typically low NO(2) levels that occurred in the early afternoon. The heterogeneous destruction of particulate matter could be an additional sink for PAN in SMA.     

Probability-based nitrate contamination map of groundwater in Kinmen

Groundwater supplies over 50 % of drinking water in Kinmen. Approximately 16.8 % of groundwater samples in Kinmen exceed the drinking water quality standard (DWQS) of NO₃ ^?-N (10 mg/L). The residents drinking high nitrate-polluted groundwater pose a potential risk to health. To formulate effective water quality management plan and assure a safe drinking water in Kinmen, the detailed spatial distribution of nitrate–N in groundwater is a prerequisite. The aim of this study is to develop an efficient scheme for evaluating spatial distribution of nitrate–N in residential well water using logistic regression (LR) model. A probability-based nitrate–N contamination map in Kinmen is constructed. The LR model predicted the binary occurrence probability of groundwater nitrate–N concentrations exceeding DWQS by simple measurement variables as independent variables, including sampling season, soil type, water table depth, pH, EC, DO, and Eh. The analyzed results reveal that three statistically significant explanatory variables, soil type, pH, and EC, are selected for the forward stepwise LR analysis. The total ratio of correct classification reaches 92.7 %. The highest probability of nitrate–N contamination map presents in the central zone, indicating that groundwater in the central zone should not be used for drinking purposes. Furthermore, a handy EC–pH-probability curve of nitrate–N exceeding the threshold of DWQS was developed. This curve can be used for preliminary screening of nitrate–N contamination in Kinmen groundwater. This study recommended that the local agency should implement the best management practice strategies to control nonpoint nitrogen sources and carry out a systematic monitoring of groundwater quality in residential wells of the high nitrate–N contamination zones.     

Waterfowls habitat modeling: Simulation of nest site selection for the migratory Little Tern (Sterna albifrons) in the Nakdong estuary

This paper aims to find patterns in nest site selection by Little Terns Sterna albifrons, in the Nakdong estuary in South Korea. This estuary is important waterfowl stopover and breeding habitat, located in the middle of the East Asia-Australasian Flyway. The Little Tern is a common species easily observed near the seashore but their number is gradually declining around the world. We investigated their nests and eggs on a barrier islet in the Nakdong estuary during the breeding season (May to June, 2007), and a pattern for the nest site selection was identified using genetic programming (GP). The GP generated a predictive rule-set model for the number of Little Tern nests (training: R² = 0.48 and test: 0.46). The physical features of average elevation, variation of elevation, plant coverage, and average plant height were estimated to determine the influence on nest numbers for Little Tern. A series of sensitivity analyses stressed that mean elevation and vegetation played an important role in nest distribution for Little Tern. The influence of these two variables could be maximized when elevation changed moderately within the sampled quadrats. The study results are regarded as a good example of applying GP to vertebrate distribution patterning and prediction with several important advantages compared to conventional modeling techniques, and can help establish a management or restoration strategy for the species.