Machine-learning paradigms for selecting ecologically significant input variables

Harmful algal blooms, which are considered a serious environmental problem nowadays, occur in coastal waters in many parts of the world. They cause acute ecological damage and ensuing economic losses, due to fish kills and shellfish poisoning as well as public health threats posed by toxic blooms. Recently, data-driven models including machine-learning (ML) techniques have been employed to mimic dynamics of algal blooms. One of the most important steps in the application of a ML technique is the selection of significant model input variables. In the present paper, we use two extensively used ML techniques, artificial neural networks (ANN) and genetic programming (GP) for selecting the significant input variables. The efficacy of these techniques is first demonstrated on a test problem with known dependence and then they are applied to a real-world case study of water quality data from Tolo Harbour, Hong Kong. These ML techniques overcome some of the limitations of the currently used techniques for input variable selection, a review of which is also presented. The interpretation of the weights of the trained ANN and the GP evolved equations demonstrate their ability to identify the ecologically significant variables precisely. The significant variables suggested by the ML techniques also indicate chlorophyll-a (Chl-a) itself to be the most significant input in predicting the algal blooms, suggesting an auto-regressive nature or persistence in the algal bloom dynamics, which may be related to the long flushing time in the semi-enclosed coastal waters. The study also confirms the previous understanding that the algal blooms in coastal waters of Hong Kong often occur with a life cycle of the order of 1–2 weeks.     

Effect of sulfate on Cu(Ⅱ) sorption to polymer-supported nano-hydrated ferric oxides: Experimental and modeling studies

Incorporating of hydrous ferric oxide(HFO) inside porous supports with large sizes has become an effective way to decontaminate the water from heavy metals. Ubiquitous anions like sulfate are usually present in high concentrations in water, and might greatly affect adsorption behavior of hybrid HFO. Here, a polymer-based HFO-CPS was fabricated by encapsulating nano-HFO inside a chloromethylated polystyrene polymer(CPS) and the reactivity of HFO-CPS with Cu(Ⅱ) was evaluated in the presence of sulfate ions.Surface complexation theory was firstly employed to describe the effect of sulfate on Cu(Ⅱ) adsorption edges of hybrid HFO-CPS, where constant capacitance model(CCM) was adopted. The available weak adsorption site Fe_((2))OH of hybrid HFO-CPS was found to decrease from 20% Fe to 5% Fe, which might be caused by the pore plugging effect after HFO encapsulation. With the assumption that a ternary complex was formed, the effect of sulfate on Cu(Ⅱ) adsorption by HFO-CPS were successfully described by CCM using the optimized Fe_((2))OH site under different sulfate concentrations(1 or 10 mmol·L~(-1)) and Cu/Fe ratios(0.0042 or 0.0252). It is confirmed that the formation of Fe OHCu SO_4 ternary surface complexes played an important role in enhancing Cu(Ⅱ) adsorption on HFO-CPS in the presence of sulfate.     

纳米氧化锆/氧化锌光催化降解酸性红B的研究

以醋酸锌和氯氧化锆为原料，采用化学沉淀法制备了纳米氧化锆／氧化锌光催化剂。在中性条件下研究了催化剂煅烧温度，锆复合量，催化剂用量，染料初始质量浓度，过氧化氢质量浓度，各种阴、阳离子等条件对酸性红B脱色反应的影响。结果表明，该催化剂最佳制备条件为煅烧温度350℃，锆复合量2．5％（物质的量分数）。催化剂最佳用量0．9g／L。提高染料初始质量浓度会降低反应脱色率。适量过氧化氢可提高反应脱色率，当其质量浓度超过300mg／L会起负作用。NO3^-对反应影响不大；Fe^3＋和Ag^＋对反应起促进作用；SO4^2-，Cl^-，NO2^-等阴离子和Fe^2＋，Mn^2＋等阳离子对反应起抑制作用。     

Surface acidity study of Mn+-montmorillonite clay catalysts by FT-IR spectroscopy: Correlation with esterification activity

A simple method for evaluating the surface acidity of different cation-exchanged montmorillonite (mont) clay catalysts, Mⁿ⁺-mont (Mⁿ⁺=Al³⁺, Fe³⁺, Cr³⁺, Zn²⁺, Ni²⁺, Cu²⁺, and H⁺), involving treatment with pyridine is described. After treating with pyridine, the samples were heated at 120 °C and the FT-IR spectra were directly recorded in the region 1650 and 1350 cm⁻¹. The data obtained show the presence of both Lewis and Brønsted acid sites. The activities of the catalysts to bring about Brønsted acid catalysed esterification of succinic acid with iso-butanol to yield di-(iso-butyl) succinate have been studied. The Brønsted acidity data obtained for Mⁿ⁺-mont correlated well with activity in the esterification reaction. The activities of the catalysts were found to decrease in the order of exchange ions Al³⁺ > Fe³⁺ > Cr³⁺ > Zn²⁺ > Ni²⁺ > Cu²⁺ > Na⁺-mont. They also correlated well with the charge to radius ratio of the cations. The catalysts exchanged with trivalent cations showed stronger absorption bands attributed to Brønsted acidity (1540 cm⁻¹) whereas those exchanged with divalent cations showed an increased Lewis acidity (1450 cm⁻¹) and reduced Brønsted acidity along with charge to radius ratio. Zn²⁺-, Cu²⁺- and Ni²⁺-exchanged clays showed an additional peak around 1605 cm⁻¹ which is attributed to the pyridine adsorption on surface sites through its π electrons. The method suggested here to evaluate the acidity is suitable for active sites which are thermally unstable such as water molecules in the hydration shell of a cation in exchanged clay.     

生物滤料滤池处理姚江微污染水源水

通过中试试验,考察了不同滤料介质的生物滤池对于姚江微污染水源水的处理效果。结果表明,双层生物滤料滤池能够有效地去除有机物、氨氮等污染物质,可以延长滤池反冲洗周期,并能在短时间内恢复到正常处理能力,适合于传统滤池的改造。采用颗粒活性炭-石英砂滤料滤池的综合处理效果优于同类型的颗粒活性炭-沸石滤料滤池,通过加入少量臭氧(0.8～1.0mg/L)可以提高生物滤池的去除效果。     

Synthesis,structure, and adsorption properties of a three-dimensional porous yttrium–organic coordination network

Deprotonation of 4,4′-biphenyldicarboxylic acid (H₂BPDC) with triethylamine followed by the copolymerization with Y(III) in N,N-dimethylformamide (DMF) at room temperature yields a new three-dimensional (3-D) porous metal–organic coordination network, [Y₂(BPDC)₃(DMF)₂(H₂O)₂]_n · (DMF)_n · (H₂O)_n (1). Compound 1 (C_24.50H₁₉N_1.50O₉Y) crystallizes in the triclinic P-1 space group (a = 8.220 (2), b = 13.998 (4), c = 14.212 (4) Å, α = 111.058 (5)°, β = 90.187 (5)°, γ = 94.318 (5)°, V = 1520.9 (7) ų, and Z = 2). X-ray crystallography reveals that 1 consists of a 3-D framework contained open 1-D channels with the dimension of 5 × 10 Å along the crystallographic a axis. The adsorption measurements show that compound 1 can adsorb N₂, Ar and CO₂ into its pores. The adsorption isotherms for MeOH and H₂O were also measured.     

高铁酸钾去除饮用水源中盐酸四环素试验研究

利用提纯后的次氯酸钠溶液、硝酸铁、氢氧化钾制备高铁酸钾。并采用高铁酸钾氧化去除水中盐酸四环素（TC）,初步探讨了高铁酸钾去除TC的效果,研究了高铁酸钾投加量、pH值、氧化时间等对去除效率的影响。结果表明,高铁酸钾可以有效快速地去除水中的TC,在一定范围内,高铁酸钾投加越多,TC去除率越高,反应越快。pH值对反应影响较大,最优pH值范围为9～10。降解反应主要发生在前60S,在之后的10-20min内高铁酸钾与TC持续反应,TC得到进一步的降解。当高铁酸钾与TC摩尔比为1：1和1：5时,反应60S后的TC去除率约为100％。但反应液TOC下降幅度不大,说明大部分的TC仅转化为中间产物,未得到彻底矿化。     

溴酸根在紫外和氯消毒联用工艺中的形成

以H2O-Br--Cl2/NH2Cl/ClO2为研究对象,考查UV作用下BrO3-产生的情况。结果表明：原水和去离子水背景下,Cl2/UVC联用可以氧化部分的Br-生成BrO3-;NH3可以有效的抑制BrO3-生成,并且NH2Cl/UVC作用时不生成BrO3-;ClO2/UV体系产生溴酸根能力明显弱于Cl2/UV;ClO2/UVC产生BrO3-的量高于ClO2/UVA。酸性条件同时促进BrO3-的产生和ClO2的分解,碱性条件正好相反。     

我国南方农村生活污水处理技术的研发现状

针对农村生活污水直接排放已经成为影响我国农村水环境质量主要因素之一的现状,从适合我国农村的以村落或居民点为单位进行生活污水分散式处理的思维入手,介绍了我国现今主要的分散式生活污水处理技术的原理、特点、不足及其应用现状;继而综合比较了这些技术的技术经济指标,提出了适合我国农村的分散式生活污水处理技术的设计原则;最后提出发展有较高水力负荷,并具备小规模设备化特征和多种生物处理单元复合的创新技术是我国农村生活污水处理技术发展的主要方向。     

生物硅藻土-动态膜生物反应器处理微污染原水的研究

以硅藻土作为基材开发了一种新型给水处理技术——生物硅藻土-动态膜反应器,并对该工艺系统处理微污染原水的去除性能进行了小试研究.结果表明,在通量为40 L/(m2.h)的条件下,系统对浊度有较好的去除效果,且出水浊度均在1 NTU以下.本工艺对CODMn和UV254也有较好的去除效果,去除率分别达58.14%和45.8%,这主要是由于硅藻土吸附、微生物降解和动态膜的分离作用;同时,反应器对氨氮的去除率也较好,达到90%以上,这主要基于反应器内微生物的分解作用.