泸沽湖沉积物－水界面扩散作用对上覆水体基本化学组成的影响

通过云南泸沽湖──半封闭深水湖泊湖水和沉积物孔隙水中Ｃａ２＋、Ｋ＋、Ｎａ＋、ＨＣＯ等基本组分及ｐＨ等剖面分布的研究,结果表明,这些基本组分可以自底部沉积物向上覆水体扩散迁移。定量地估算了扩散通量及其对上覆水体的影响程度,说明湖泊沉积物－水界面作用在控制整个水体水化学基本组成中起着重要的作用。     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Gaseous elemental mercury concentration in atmosphere at urban and remote sites in China

An investigation of gaseous elemental mercury concentration in atmosphere was conducted at Beijing and Guangzhou urban, Yangtze Delta regional sites and China Global Atmosphere Watch Baseline Observatory (CGAWBO) in Mt. Waliguan of remote continental area of China. High temporal resolved data were obtained using automated mercury analyzer RA-915 . Results showed that the overall hourly mean Hg0 concentrations in Mt. Waliguan were 1.7± 1.1 ng/m3 in summer and 0.6±0.08 ng/m3 in winter. The concentration in Yangtze Delta regional site was 5.4±4.1 ng/m3, which was much higher than those in Waliguan continental background area and also higher than that found in North America and Europe rural areas. In Beijing urban area the overall hourly mean Hg0 concentrations were 8.3±3.6 ng/m3 in winter, 6.5±5.2 ng/m3 in spring, 4.9±3.3 ng/m3 in summer, and 6.7±3.5 ng/m3 in autumn, respectively, and the concentration was 13.5±7.1 ng/m3 in Guangzhou site. The mean concentration reached the lowest value at 14:00 and the highest at 02:00 or 20:00 in all monitoring campaigns in Beijing and Guangzhou urban areas, which contrasted with the results measured in Yangtze Delta regional site and Mt. Waliguan. The features of concentration and diurnal variation of Hg0 in Beijing and Guangzhou implied the importance of local anthropogenic sources in contributing to the high Hg0 concentration in urban areas of China. Contrary seasonal variation patterns of Hg0 concentration were found between urban and remote sites. In Beijing the highest Hg0concentration was in winter and the lowest in summer, while in Mt. Waliguan the Hg0 concentration in summer was higher than that in winter. These indicated that different processes and factors controlled Hg0 concentration in urban, regional and remote areas.     

Particle size distribution and removal in the chemical-biological flocculation process

The particle characterization from the influent and effluent of a chemical-biological flocculation (CBF) process was studied with a laser diffraction device. Water samples from a chemically enhanced primary treatment (CEPT) process and a primary sediment tank process were also analyzed for comparison. The results showed that CBF process was not only effective for both the big size particles and small size particles removal, but also the best particle removal process in the three processes. The results also indicated that CBF process was superior to CEPT process in the heavy metals removal. The high and non-selective removal for heavy metals might be closely related to its strong ability to eliminate small particles. Samples from different locations in CBF reactors showed that small particles were easier to aggregate into big ones and those disrupted flocs could properly flocculate again along CBF reactor because of the biological flocculation.     

水体环境中天然有机质腐殖酸研究进展

腐殖酸作为一种资源广泛存在于自然界中,它是影响环境生态平衡的重要因素,也是潜在的、可大力开发和综合利用的有机资源。腐殖酸类物质具有多种活性官能团,具有酸性、亲水性、界面活性、阳离子交换能力、络合作用及吸附分散能力。腐殖酸概念、理论出现了重大突破,已从传统腐殖酸重点或仅研究腐殖酸自身发生中的物质流动、能量转化规律,同时着眼研究腐殖酸与土壤、水体和生物多界面的环境过程和机理。文章主要以水环境为例,天然有机质研究历史、化学结构,对环境污染物效应和去除技术等几个方面的研究进展进行了简要的总结;对现代腐殖酸的研究趋势进行了展望。     

鼎湖山森林演替序列水文过程中总有机碳(TOC)变化规律及其对土壤碳平衡的贡献

森林水文过程中的总有机碳转运对土壤有机碳平衡起着重要的作用,但我们对于水文过程对碳平衡的贡献机理所知甚少.本研究针对鼎湖山季风常绿阔叶林演替序列不同森林生态系统(马尾松林、针阔混交林和季风常绿阔叶林(简称季风林))的大气降水、穿透水、树干流、凋落物淋洗水以及地表径流中的总有机碳(TOC)进行了三年(2002年4月-2005年5月)观测,以此来分析水文学过程中TOC的变化规律和水文学过程对不同成熟度森林生态系统土壤有机碳积累的贡献.每场雨后进行水样的采集,采集的水样装入棕色玻璃瓶中,加硫酸至pH值小于2,放置于实验室冰箱冷藏待测.TOC用日本岛津公司生产的5000A型TOC-V分析仪测定.研究结果及推论如下:鼎湖山森林水文学过程中TOC浓度和总量变化呈现规律性的变化.大气降水中的TOC浓度和总量分别为(3.65±0.59)mg·L~(-1)和51.8104 kg·hm~(-2)·a~(-1),大气降水是鼎湖山森林生态系统水文循环过程中TOC的主要来源.穿透水(DTF)中TOC浓度和总量均为:松林>混交林>季风林,其中季风林TOC浓度显著低于其他两种林型.松林树干流的TOC浓度显著高于混交林和季风林.凋落物淋洗水TOC浓度和总量大小依次均为:松林>混交林>季风林,且三林型间存在显著差异(p<0.05).径流中TOC浓度和总量均较小,且无明显差异.在湿季5月份,穿透水、树干流、凋落物淋洗水的TOC浓度呈现下降趋势.干季(10月)开始以后,穿透水、树干流、凋落物淋洗水中的TOC浓度又逐步回升.地表径流中TOC浓度干湿季变化趋势不明显.干季中各水文学分量TOC浓度大于湿季,但TOC总量呈现相反趋势.在森林水文学过程中,凋落物淋洗水所携带的有机碳量是土壤有机碳输入的最大项,季风林、混交林、松林中TOC总量分别为246.983 kg·hm~(-2)·a~(-1),255.187kg·hm~(-2)·a~(-1)和261.876kg·hm~(-2)·a~(-1);其次是直接到达土壤表面的穿透水,季风林、混交林、松林中TOC总量分别为28.152kg·hm~(-2)·a~(-1),37.410kg·hm~(-2)·a~(-1)和43.176kg·hm~(-2)·a~(-1);树干流中有机碳浓度虽高,但总量很微小,季风林、混交林、松林中TOC总量分别为4.663kg·hm~(-2)·a~(-1),5.910kg·hm~(-2)·a~(-1)和4.566kg·hm~(-2)·a~(-1),所以对土壤有机碳收入贡献不大.径流所携带的TOC总量很小,季风林、混交林、松林中分别为8.707kg·hm~(-2)·a~(-1),9.318kg·hm~(-2)·a~(-1),7.220kg·hm~(-2)·a~(-1).由此可知,水文过程输入土壤的TOC总量远大于径流所带走的TOC总量,导致了水文过程中的TOC存留在土壤中,对土壤有机碳(SOC)的积累起着重要作用.季风林、混交林和马尾松林土壤每年通过水文学过程净输入的有机碳量分别为(27.1+1.65)g·m~(-2),(28.9±2.79)g·m~(-2)和(30.2±2.65)g·m~(-2).水文学过程中的这部分有机碳由于占总有机碳比例较小往往被忽视,但是正是由于水分在土壤中的下渗使得有机碳的分布趋于均匀,这将更加利于SOC的积累和保存.     

杭州秋冬季PM2.5污染特征分析

为研究杭州PM_2.5污染来源特征,利用2013—2019年杭州市PM_2.5监测数据和气象观测数据,分析了杭州市2013—2019年PM_2.5浓度变化,选取本地积累型和输入型2种PM_2.5污染过程,结合单颗粒气溶胶飞行时间质谱仪（SPAMS）和在线离子色谱数据,探讨杭州市PM_2.5化学组分和污染来源。结果表明：每年秋冬季（11月至次年3月）杭州以东北风、西北风及偏南风为主,风速低于4 m/s时,大气扩散条件差,受本地污染物积累影响,PM_2.5浓度容易出现超标;风速较大且为东北风和西北风时,受上游污染输入影响,易出现PM_2.5重度污染。本地积累型和输入型案例中,PM_2.5化学组分中占比最大的为NO₃^-、SO₄^2-和NH₄⁺;PM_2.5浓度上升过程中,二次NO₃^-和SO₄^2-转换率明显上升,其中NO₃^-上升更为显著,二次气溶胶污染严重。2次案例中,PM_2.5来源贡献占比前3位均为机动车尾气源、燃煤源和工业工艺源,其中本地积累型PM_2.5浓度上升阶段,机动车尾气源占比会明显上升;输入型案例中,输入阶段机动车尾气源占比显著上升,燃煤源贡献也小幅上升。     

高级氧化技术降解水体中抗生素的研究进展

抗生素是一类用于阻止和治疗微生物传染性疾病的人用和兽用药物,在人类和动物疾病治疗领域以及水产养殖业有着广泛的用途。近年来,抗生素作为一种新型污染物不断排入水体并且在水体中持续存在,对水生态环境以及人类健康造成了威胁。化学和生物等降解技术引起广泛关注,其中高级氧化技术(AOPs)由于其具有适用范围广、反应速率快、氧化能力强等特点,被成功应用到自然水体和污水中抗生素等多种有机污染物的降解。基于近年来的研究成果,综述了几种常见AOPs对抗生素的降解过程和机理,对比分析了对抗生素的降解效果,最后展望了AOPs应用于抗生素降解的研究方向和挑战。     

Microwave and Fenton's reagent oxidation of wastewater

We compared two H₂O₂ oxidation methods for the treatment of industrial wastewater: oxidation using Fenton's reagent [H₂O₂/Fe(II)] and microwave irradiation. Both methods were applied to the treatment of synthetic phenol solutions (100 mg L⁻¹) and of an industrial effluent containing a mixture of ionic and non-ionic surfactants at high load (20 g L⁻¹ of COD). The effects of initial pH, initial H₂O₂ concentration, Fenton catalyst amount and irradiation time were assessed. According to the oxidation of phenol, it has been found that the oxidation by Fenton's reagent is dependent on the pH, contrary to the microwave system, which is not influenced by this parameter. For both systems, a limiting amount of oxidant has been found; above this point the oxidation of phenol is not improved by a further addition of peroxide. The oxidation of the industrial surfactant effluent has only been successful with the Fenton's reagent. In this case, large amounts of ferrous ions are necessary for the precipitation of the ionic surfactants of the effluent, followed by the oxidation of the non-ionic constituents of the solution. Electronic Publication