Characterization of Fe5(AsO3)3Cl2(OH)4·5H2O, a new ferric arsenite hydroxychloride precipitated from FeCl3–As2O3–HCl solutions relevant to arsenic immobilization

Tooeleite(Fe6(As03)4 SO4(OH)4·4 H_2 O) is widely precipitated for direct As(III) removal from sulfate-rich industrial effluents.However,whether or not Fe(III)-As(III)-Cl(-I) precipitate is produced in chloridizing leaching media for As immobilization is almost unknown.This work founded the existence of ferric arsenite(hydroxy)chloride as a new mineral for As(III)removal.Its chemical composition and solid characterization were subsequently studied by using scanning electron microscope with an energy dispersive spectrometer(SEM-EDS),X-ray diffraction(XRD),infrared(FT-IR),Raman spectroscopy and thermogravimetric(TG)curve.The results showed the formation of a yellow precipitate after 3-days reaction of Fe(III)/As(III) with molar ratio≈1.7 in chloride solution at pH 2.3 neutralized with NaOH.Compared with tooeleite,chemical analysis and solid characterization indicated that Cl(-I)replaces S04(-II) producing ferric arsenite hydroxychloride with formula Fe5(As03)_3-Cl_2(OH)4·5 H_2 O.This new plate shaped solid showed better crytallinity than tooeleite,although it has similar morphology and characteristic bands to tooeleite.The FT-IR bands at 628,964 cm-1 and the Raman bands at 448,610,961 cm-1 were assigned to Fe-O or As(Ⅲ)-O-Fe or As(Ⅲ)-O bending/stretching vibration,indicating that both arsenite and chloride substituted for the position of sulfate for ferric arsenite hydro xychloride produced due to the lack of the SO_4~(2-) vibrations.Cl-(I) also contributed to increase As removal efficiency in aqueous sulfate media under acidic pH conditions via the probable formation of sulfatechloride ferric arsenite.     

淮南新集矿区主要充水含水层水化学特征及成因

为探明新集矿区深层地下水离子组成及其演化特征,采集了研究区砂岩水和太灰水等共20个水样,测试分析常规离子和氢氧同位素数据,采用Piper三线图、相关性分析、离子比例系数与饱和指数等方法,探讨了研究区深层地下水水化学特征及其成因。结果表明:(1)研究区砂岩水为高矿化度水,平均矿化度为2 743. 73mg/L,水化学类型主要为Cl-Na型,太灰水多为中矿化度水,平均矿化度为1 468. 33mg/L,水化学类型主要为HCO3·Cl-Na型和Cl-Na型;(2)研究区地下水的补给不仅有大气降水和地表水,还有古气候条件下形成的古溶滤-渗入水,且由于矿物质与深层地下水的水岩作用使得氧同位素发生漂移;(3)含水层中主要发生的水岩相互作用有硅酸盐和蒸发盐岩的溶解及阳离子交替吸附作用,盐岩和石膏在研究区地下水中是反应性矿物,白云石和方解石的溶解在矿区地下水中呈过饱和状态。     

金属离子屏蔽腐殖酸对污泥厌氧消化抑制作用实验研究

以实验室培养、几乎不含腐殖质和金属离子的剩余污泥为研究对象,选择与市政污泥中腐殖酸特征相近的市售腐殖酸作为外加填充腐殖质,通过投加外源金属离子实验研究屏蔽腐殖质对污泥厌氧消化过程的抑制作用.结果表明,单独投加Ca2+与Al3+可分别获得65.4%和65.7%的屏蔽抑制率;Ca2++Al3+组合投加效果更佳,可获得高达80.1%的屏蔽抑制率,具有"1+12"的屏蔽抑制效果.然而,过高的金属离子含量(或组合含量)不仅无助于进一步提高屏蔽抑制效果,反而会因抑制微生物活性而导致屏蔽抑制率下降.Ca2+通过阳离子交换产生屏蔽抑制作用,而Al3+主要靠静电作用和网捕卷扫作用产生屏蔽效果.在屏蔽腐殖酸抑制方面,三价金属离子好于二价金属离子的原因是两者的静电作用力大小、作用方式、环境效果不尽相同.     

基于天地协同的巢湖水华分布特征分析

基于MODIS影像监测2016年巢湖蓝藻水华分布,结果表明：水华的频次,持续时间从西北部水域向东南部水域逐渐减弱;西半湖湖心水华开始日期最早（5月19日）,持续时间最长为131d,塘西水华发生频次较多（10次）.进一步将水华遥感监测结果与同步水面实测水质参数数据（藻密度,叶绿素a,总氮,总磷）进行相关性分析,利用Q型聚类分析将水面实测采样点分为东区和西区两部分.西区藻密度,叶绿素a,总氮,总磷和水华面积相关性较强（R²均大于0.6）.     

Comparison of the effects of aluminum and iron(III) salts on ultrafiltration membrane biofouling in drinking water treatment

Coagulation plays an important role in alleviating membrane fouling, and a noticeable problem is the development of microorganisms after long-time operation, which gradually secrete extracellular polymeric substances (EPS). To date, few studies have paid attention to the behavior of microorganisms in drinking water treatment with ultrafiltration (UF) membranes. Herein, the membrane biofouling was investigated with different aluminum and iron salts. We found that Al₂(SO₄)₃·18H₂O performed better in reducing membrane fouling due to the slower growth rate of microorganisms. In comparison to Al₂(SO₄)₃·18H₂O, more EPS were induced with Fe₂(SO₄)₃·xH₂O, both in the membrane tank and the sludge on the cake layer. We also found that bacteria were the major microorganisms, of which the concentration was much higher than those of fungi and archaea. Further analyses showed that Proteobacteria was dominant in bacterial communities, which caused severe membrane fouling by forming a biofilm, especially for Fe₂(SO₄)₃·xH₂O. Additionally, the abundances of Bacteroidetes and Verrucomicrobia were relatively higher in the presence of Al₂(SO₄)₃·18H₂O, resulting in less severe biofouling by effectively degrading the protein and polysaccharide in EPS. As a result, in terms of microorganism behaviors, Al-based salts should be given preference as coagulants during actual operations.     

The production of formaldehyde and hydroxyacetone in methacrolein photooxidation: New insights into mechanism and effects of water vapor

Methacrolein(MACR) is an abundant multifunctional carbonyl compound with high reactivity in the atmosphere. In this study, we investigated the hydroxyl radical initiated oxidation of MACR at various NO/MACR ratios(0 to 4.04) and relative humidities( 3% to80%) using a flow tube. Meanwhile, a box model based on the Master Chemical Mechanism was performed to test our current understanding of the mechanism. In contrast to the reasonable predictions for hydroxyacetone production, the modeled yields of formaldehyde(HCHO) were twice higher than the experimental results. The discrepancy was ascribed to the existence of unconsidered non-HCHO forming channels in the chemistry of CH_3-UC(=CH_2)OO, which account for approx. 50%. In addition, the production of hydroxyacetone and HCHO were affected by water vapor as well as the initial NO/MACR ratio. The yields of HCHO were higher under humid conditions than that under dry condition. The yields of hydroxyacetone were higher under humid conditions at low-NO_x level, while lower at high-NOxlevel. The reasonable explanation for the lower hydroxyacetone yield under humid conditions at high-NO_x level is that water vapor promotes the production of Umethacrolein nitrate in the reaction of HOCH_2 C(CH_3)(OO)CHO with NO due to the peroxy radical-water complex formation, which was evidenced by calculational results. And the minimum equilibrium constant of this water complex formation was estimated to be 1.89 × 10~(-18) cm~3/molecule. These results provide new insights into the MACR oxidation mechanism and the effects of water vapor.     

Effects of O3/Cl2 disinfection on corrosion and opportunistic pathogens growth in drinking water distribution systems

The effects of O_3/Cl_2 disinfection on corrosion and the growth of opportunistic pathogens in drinking water distribution systems were studied using annular reactors(ARs).The corrosion process and most probable number(MPN) analysis indicated that the higher content of iron-oxidizing bacteria and iron-reducing bacteria in biofilms of the AR treated with O_3/Cl_2 induced higher Fe_3O_4 formation in corrosion scales.These corrosion scales became more stable than the ones that formed in the AR treated with Cl_2 alone.O_3/Cl_2 disinfection inhibited corrosion and iron release efficiently by changing the content of corrosion-related bacteria.Moreover,ozone disinfection inactivated or damaged the opportunistic pathogens due to its strong oxidizing properties.The damaged bacteria resulting from initial ozone treatment were inactivated by the subsequent chlorine disinfection.Compared with the AR treated with Cl_2 alone,the opportunistic pathogens M.avium and L.pneumophila were not detectable in effluents of the AR treated with O_3/Cl_2,and decreased to(4.60 ± 0.14) and(3.09 ± 0.12) log10(gene copies/g corrosion scales) in biofilms,respectively.The amoeba counts were also lower in the AR treated with O_3/Cl_2.Therefore,O_3/C_l2 disinfection can effectively control opportunistic pathogens in effluents and biofilms of an AR used as a model for a drinking water distribution system.     

Assessment of column aerosol optical properties using ground-based sun-photometer at urban Harbin, Northeast China

Aerosol plays a key role in determining radiative balance, regional climate and human health. Severe air pollution over Northeast China in recent years urges more comprehensive studies to figure out the adverse effects caused by excessive aerosols. In this study, column aerosol measurements over urban Harbin, a metropolis located at the highest latitude in Northeast China, during May 2016 to March 2017 were conducted using a CIMEL sun-photometer to analyze local aerosol properties and its variation from different aspects. According to the observations, aerosol optical depth at 440 nm (AOD₄₄₀) ranges from 0.07 up to 1.54, and the large variability in both AOD₄₄₀ and Angstrom Exponent (AE_440–870) indicates the frequent change of aerosol types due of different emission sources. Coarse mode particles dominated Harbin during the studying period because of the long-range transported dust and probably the suspended snow crystals in winter. As the wavelength increases, relatively consistent decrease trends of single scattering albedo (SSA) and asymmetry factor (ASY) were observed in spring, autumn, and winter, indicating the presence of absorbing polluted aerosols. Mixed type (MIX) aerosol dominated the study region with a total percentage of 34%, and biomass burning and urban industry (BB/UI), clean continental (CC), and desert dust (DD) aerosols were found to be 31%, 27%, and 8%, respectively. The current work fills up the optical characteristics of aerosols in Harbin, and will contribute to the in-depth understanding of local aerosol variation and regional climate change over Northeast China.     

西洞庭湖入湖河流磷的污染特征

为识别西洞庭湖长江三口分流来水与洞庭湖水系河流来水磷元素的污染特征,于2016年1-12月在西洞庭湖的主要入湖河流松滋河（三口分流河道）、沅江和澧水（洞庭湖水系河流）开展了水文水质同步调查,研究了入湖河流中磷浓度和组成的时空分布特征,剖析了水文因素对磷污染特征的影响,探究了磷的来源结构.结果表明,3条主要入湖河流流量平均值表现为沅江（1 718 m3/s）>松滋河（935 m3/s）>澧水（884 m3/s）,ρ（TP）平均值表现为沅江（0.070 mg/L） < 澧水（0.077 mg/L） < 松滋河（0.138 mg/L）;沅江的年均入湖磷通量（4 177.26 t/a）对于西洞庭湖磷污染而言仍起主导作用;沅江、澧水与松滋河的磷的形态以DTP（溶解态磷,占比为78.56%~90.19%）为主,并且松滋河DTP占比（90.19%）显著高于沅江和澧水（78.56%~83.34%）.进一步的分析显示,3条河流的磷污染状况受水文因素影响显著,沅江和澧水磷浓度表现为汛期高于非汛期,磷的主要来源为非点源;松滋河的磷浓度表现为非汛期高于汛期,汛期主要取决于长江来水状况,非汛期主要取决于松滋口以下区间的点源污染状况.研究显示,3条河流磷浓度和形态均具有时空差异性,并且年内变化规律差异较大.