厌氧氨氧化无纺滤布生物膜反应器的运行

氧气是厌氧氨氧化菌的抑制因素,通过无纺滤布生物膜系统内部形成适合厌氧氨氧化菌的厌氧环境,运行62 d,实现0.617 kg N/(m³·d)氮容积去除负荷,稳定运行阶段氨氮和亚硝氮的去除率分别为97.9％和98.7％；98 mg N/L NO^-₂-N经24 h接触产生完全抑制,通过将进水亚硝氮浓度降至20～40 mg N/L,运行31 d,成功恢复厌氧氨氧化活性,试验末期氮容积去除负荷为0.641 kg N/(m³·d)。     

不同泥源对厌氧氨氧化反应器启动的影响

采用2套上流式生物膜反应器,分别接种少量厌氧氨氧化污泥和大量硝化污泥,考察其对厌氧氨氧化反应器启动的影响。污泥接种入反应器后,测得接种厌氧氨氧化污泥的反应器(R1)内MLSS为0.22 g/L,另一个反应器(R2)MLSS为2.7 g/L。与直接接种厌氧氨氧化污泥相比,R1经过72 d的运行才显现出厌氧氨氧化特性。经过114 d的培养,前者氮去除速率由0.23 kg/(m3.d)提升到5.29 kg/(m3.d),总氮去除率大于89%;R2的氮去除速率由0.01 kg/(m3.d)提升到1.1 kg/(m3.d),总氮去除率大于84.6%。说明普通污泥启动需要一个较长的筛选过程,直接接种少量的厌氧氨氧化污泥比接种普通的污泥能够更快启动厌氧氨氧化反应器。     

ANAMMOX与反硝化协同作用及氮素负荷研究

向成功启动并稳定运行630 d后的UASB生物膜反应器系统连续添加有机物,分析其对厌氧氨氧化反应脱氮效果的影响,并进行氮素浓度负荷试验.在厌氧氨氧化反应器系统中连续投加有机COD(葡萄糖),系统运行稳定,有机COD(葡萄糖)存在对系统去除氮素能力影响不大,有机COD去除率达到92.0%,仅用23 d,在同一反应器系统中成功实现了厌氧氨氧化与反硝化协同作用脱氮.氮素浓度负荷试验阶段,进水氨氮(NH 4-N)、亚硝氮(NO-2-N)以及总氮(TN)浓度负荷分别从0.063 kg/(m3·d)和0.063 kg/(m3·d)和0.126 kg/(m3·d)提升到了0.239 kg/(m3·d)、0.315 kg/(m3·d)和0.554 kg/(m3·d),相应去除率分别为84.0%、93.0%和85.0%,厌氧氨氧化工艺的UASB生物膜反应器对氮素浓度负荷仍有很大提升空间.     

厌氧氨氧化菌接种污泥的选择培养过程研究

厌氧氨氧化菌的2种不同接种污泥培养实验表明,厌氧消化污泥和好氧硝化污泥均可成功启动厌氧氨氧化过程.接种厌氧消化污泥比好氧硝化污泥培养的厌氧氨氧化菌启动快,但后者去除效果较好.接种好氧硝化污泥的反应器的厌氧氨氧化速率随着氨氮基质进水浓度的增加呈线性增加.进水氨氮浓度为280 mg/L时的氨氮平均去除率达91%;而接种厌氧消化污泥的相应氨氮平均去除率仅为52%.厌氧氨氧化过程以接种好氧硝化污泥来启动为宜.     

C/N比对ANAMMOX与反硝化协同脱氮性能影响及其动力学

采用ASBR厌氧氨氧化(ANAMMOX)反应器,考察了不同C/N(NH+4-N)比时厌氧氨氧化与反硝化协同脱氮性能表现,并与无机环境下反应器的脱氮性能相比较。研究结果表明,C/N比决定了ANAMMOX/反硝化耦合反应的发展方向。当C/N0.33时,ANAMMOX为主导反应;当C/N=0.67时,耦合反应的效果最佳,NH_4~+-N和NO_2~--N的去除率分别为92%、95%、COD去除率大于96%,实现了氨氮及COD的同时去除;当C/N=1.33时,反硝化反应逐渐占据优势;当C/N2.96时,反硝化作用成为主导反应,厌氧氨氧化反应受到明显抑制,氨氮去除率下降。采取批次实验方法研究了厌氧氨氧化与反硝化协同反应的动力学特性。用基质抑制动力学Haldane模型拟合不同基质浓度下的厌氧氨氧化活性,得到氨氮最大比增长速率为0.09 kg/(kg·d)(以VSS计),半饱和常数为8.4 mg/L、半抑制常数为1 198.2 mg/L;亚硝态氮最大比增长速率为0.27 kg/(kg·d)(以VSS计),半饱和常数为10.2 mg/L、半抑制常数为300.1 mg/L。采用Monod模型和Haldane模型分别拟合不同COD浓度和亚硝酸盐浓度下的反硝化性能,得到反硝化亚硝态氮最大比增长速率为0.2 kg/(kg VSS·d),半饱和常数为17.4 mg/L、半抑制常数为128.4 mg/L,COD半饱和常数为83.3 mg/L。     

ASBR厌氧氨氧化反应器的快速启动及脱氮原理分析

以城市生活污水为基本水质进行配水,采用ASBR研究了厌氧氨氧化反应器的快速启动过程及脱氮性能。实验条件如下:T为(35±1)℃、HRT为24 h、pH为7.2～7.5,进水NH4+-N、NO2--N浓度为40～160 mg/L,TN负荷为0.08～0.34 kg TN/(m3.d),按2∶1比例混合接种好氧短程硝化污泥和厌氧氨氧化污泥,经49 d运行成功启动厌氧氨氧化反应器,并实现稳定运行。实验结果表明:稳定运行期NH4+-N、NO2--N去除率分别达96%和98%;NH4+-N、NO2--N去除量与NO3--N生成量比值为1∶1.05∶0.29,较为接近理论值;成功启动的反应器出水pH高于进水;系统TN去除率平均值为79.7%;反应器内存在反硝化与厌氧氨氧化的协同作用,实现了部分COD去除;污泥由深棕色絮状变成红褐色颗粒状,经SEM扫描电镜观察污泥菌群种类单一,多为球状菌,有漏斗状缺口,具有典型氨氧化菌形态特征。     

低温胁迫下Ca2+对厌氧氨氧化污泥脱氮效能影响研究

为了解决厌氧氨氧化(ANAMMOX)污泥在低温下脱氮效能较低的问题,采用上流式厌氧污泥床(UASB)反应器,通过投加不同浓度的Ca~(2+),考察低温胁迫下Ca~(2+)对ANAMMOX污泥脱氮效能及特性的影响。结果表明:低温胁迫下ANAMMOX污泥脱氮效能明显降低,当Ca~(2+)投加量为0mmol/L时,氨氮、亚硝态氮去除率分别降至50%、54%,UASB反应器的TN去除负荷最低为0.094kg/(m~3·d);投加一定Ca~(2+)对ANAMMOX反应有正面促进作用,在最佳Ca~(2+)投加量(0.04mmol/L)下,氨氮、亚硝态氮去除率可分别提高至65%、68%,TN去除负荷提高至接近0.200kg/(m~3·d),脱氮效能是未投加Ca~(2+)时的2倍左右,但Ca~(2+)投加量大于0.04mmol/L时,脱氮效能开始呈现下降趋势。投加Ca~(2+)可以增大污泥颗粒粒径,提高污泥的混合液悬浮固体(MLSS)、混合液挥发性悬浮固体(MLVSS)浓度,但对污泥活性的提升不明显。     

MBBR一体式耦合短程硝化-厌氧氨氧化处理污泥水

采用移动床生物膜反应器(MBBR)处理已回收磷后的实际污泥水,在进水平均氨氮浓度为167.51 mg·L~(-1)、HRT为22.24 h、DO为0.5 mg·L~(-1)和温度为24～26℃的条件下实现了一体式短程硝化-厌氧氨氧化过程的耦合,对氨氮和总无机氮的最大去除率可达96%和79.7%。但是,一体式反应器受DO浓度影响较大,维持稳定的DO浓度对于系统的氮去除非常重要。荧光原位杂交(FISH)及高通量测序结果表明,MBBR的生物膜及活性污泥中Nitrosomonas菌分别占总菌数的10.46%和21.46%,厌氧氨氧化菌的优势菌种Candidatus Kuenenia在生物膜和活性污泥中分别占总菌数的4.13%和0.71%。因此,MBBR中活性污泥主要完成亚硝化,生物膜主要完成厌氧氨氧化,常温条件下,两者在一个反应体系中共同完成了对污泥水中氮的高效自养脱除。以上结果表明了一体式反应器处理实际污泥水的可行性,可为该工艺在实际工程中的应用提供参考。     

上流式厌氧污泥床反应器中厌氧氨氧化脱氮性能的研究

研究了上流式厌氧污泥床(UASB)反应器中厌氧氨氧化工艺的脱氮性能。接种体积比为1∶1的已驯化半年的厌氧氨氧化污泥混培物和城市污水处理厂回流污泥,采用提高基质浓度和缩短水力停留时间(HRT)2种方式提高UASB反应器的脱氮性能。结果发现,2种方式结合可在UASB反应器中获得较高的脱氮速率,经过280d后,最高总氮去除速率达到5.16kg/(m3·d)。缩短HRT并未对UASB反应器的脱氮效果产生不良影响,反而强化了脱氮性能。HRT由0.4d缩短至0.2d时,总氮去除速率由1.89kg/(m3·d)增加到3.66kg/(m3·d)。形成的颗粒污泥中的细菌的细胞形态不规则,内部有厌氧氨氧化体,为典型厌氧氨氧化菌结构特征。污泥的比基质转化速率为3.15kg/(kg·d)。经16SrDNA检测,污泥中的厌氧氨氧化菌属于"Candidatus Kuenenia"属。     

高基质浓度下厌氧氨氧化反应器的启动过程

采用3套厌氧序批式生物膜反应器,研究了高基质浓度对厌氧氨氧化反应器启动过程的影响。经过50 d左右培养,3个反应器氮容积去除负荷均达到0.23 kg N/(m3.d)。但是随着氮容积负荷的提高,反应器内pH也随之升高,最终超过了厌氧氨氧化菌最适生长条件,3个反应器脱氮效果逐渐下降。然后分别通过降低浓度、延长水力停留时间的方式对其脱氮效能进行恢复性研究。结果表明高基质浓度不利于厌氧氨氧化反应器脱氮能力的增强。采用低基质浓度的方式提高反应器氮容积去除负荷时,脱氮效能不仅得到了恢复,而且能够提高到0.45 kg N/(m3.d)。说明低基质难度比高基质浓度更有利于厌氧氨氧化脱氮效能的提高。     

Dioxin- and POP-contaminated sites—contemporary and future relevance and challenges

BACKGROUND, AIM AND SCOPE: Once they have been generated, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and other persistent organic pollutants (POPs) can persist in soils and sediments and in waste repositories for periods extending from decades to centuries. In 1994, the US EPA concluded that contaminated sites and other reservoirs are likely to become the major source of contemporary pollution problems with these substances. With this in mind, this article is the first in a new series in ESPR under the title 'Case Studies on Dioxin and POP Contaminated Sites--Contemporary and Future Relevance and Challenges', which will address this important issue. The series will document various experiences from sites contaminated with PCDD/F and other POPs. This article provides an overview of the content of the articles comprising the series. In addition, it provides a review of the subject in its own right and identifies the key issues arising from dioxin/POP-contaminated sites. Additionally, it highlights the important conclusions that can be drawn from these examples. The key aim of this article and of the series as a whole is to provide a comprehensive overview of the types of PCDD/F contaminated sites that exist as a result of historical activities. It details the various processes whereby these sites became contaminated and attempts to evaluate their contemporary relevance as sources of PCDD/Fs and other POPs. It also details the various strategies used to assess these historical legacies of contamination and the concepts developed, or which are under development, to effect their remediation. MAIN FEATURES: Special sessions on 'Contaminated sites--Cases, remediation, risk and policy' were held at the DIOXIN conferences in 2006 and 2007, and this theme will be continued at DIOXIN 2008 to be held in Birmingham. Selected cases from the approximately 70 contributions made to these sessions, together with some additional invited case studies are outlined together with the key issues they raise. By evaluating these cases and adding details of experiences published in the current literature, an overview will be given of the different features and challenges of dioxin and POP-contaminated sites. RESULTS: This article provides a systematic categorisation of types of PCDD/F and POP-contaminated sites. These are categorised according to the chemical or manufacturing process, which generated the PCDD/Fs or POPs and also includes the use and disposal aspects of the product life cycle in question. The highest historical PCDD/F and dioxin-like polychlorinated biphenyl (PCB) contamination burdens have arisen as a result of the production of chlorine and of chlorinated organic chemicals. In particular, the production of chlorinated pesticides, PCBs and the related contaminated waste streams are identified being responsible for historical releases of toxic equivalents (TEQs) at a scale of many tonnes. Along with such releases, major PCDD/F contaminated sites have been created through the application or improper disposal of contaminated pesticides, PCBs and other organochlorine chemicals, as well through the recycling of wastes and their attempted destruction. In some extreme examples, PCDD/F contaminated sites have also resulted from thermal processes such as waste incinerators, secondary metal industries or from the recycling or deposition of specific waste (e.g. electronic waste or car shredder wastes), which often contain chlorinated or brominated organic chemicals. The examples of PCDD/F and dioxin-like PCB contamination of fish in European rivers or the impact of contaminated sites upon fishing grounds and upon other food resources demonstrate the relevance of these historical problems to current and future human generations. Many of the recent food contamination problems that have emerged in Europe and elsewhere demonstrate how PCDD/F and dioxin like PCBs from historical sources can directly contaminate human and animal feedstuffs and indeed highlight their considerable contemporary relevance in this respect. Accordingly, some key experiences and lessons learnt regarding the production, use, disposal and remediation of POPs from the contaminated sites are summarised. DISCUSSION: An important criterion for evaluating the significance and risks of PCDD/Fs and other POPs at contaminated sites is their present or future potential for mobility. This, in turn, determines to a large degree their propensity for off-site transport and environmental accessibility. The detailed evaluation of contaminated site cases reveals different site-specific factors, which influence the varied pathways through which poor water-soluble POPs can be mobilised. Co-contaminants with greater water solubility are also typically present at such sites. Hence, pumping of groundwater (pump and treat) is often required in addition to attempting to physically secure a site. At an increasing number of contaminated sites, securing measures are failing after relatively short time spans compared to the time horizon, which applies to persistent organic pollutant contamination. Due to the immense costs and challenges associated with remediation of contaminated sites 'monitored natural attenuation' is increasingly gaining purchase as a conceptual remediation approach. However, these concepts may well prove limited in their practical application to contaminated sites containing persistent organic pollutants and other key pollutants like heavy metals. CONCLUSIONS: It is inevitable, therefore, that dioxin/POP-contaminated sites will remain of contemporary and future relevance. They will continue to represent an environmental issue for future generations to address. The securing and/or remediation of dioxin/POP-contaminated sites is very costly, generally in the order of tens or hundreds of millions of dollars. Secured landfills and secured production sites need to be considered as constructions not made for 'eternity' but built for a finite time scale. Accordingly, they will need to be controlled, supervised and potentially repaired/renewed. Furthermore, the leachates and groundwater impacted by these sites will require ongoing monitoring and potential further remediation. These activities result in high maintenance costs, which are accrued for decades or centuries and should, therefore, be compared to the fully sustainable option of complete remediation. The contaminated site case studies highlight that, while extensive policies and established funds for remediation exist in most of the industrialised western countries, even these relatively well-regulated and wealthy countries face significant challenges in the implementation of a remediation strategy. This highlights the fact that ultimately only the prevention of contaminated sites represents a sustainable solution for the future and that the Polluter Pays Principle needs to be applied in a comprehensive way to current problems and those which may emerge in the future. RECOMMENDATIONS AND PERSPECTIVES: With the continuing shift of industrial activities in developing and transition economies, which often have poor regulation (and weak self-regulation of industries), additional global challenges regarding POPs and other contaminated sites may be expected. In this respect, a comprehensive application of the "polluter pays principle" in these countries will also be a key to facilitate the clean-up of contaminated areas and the prevention of future contaminated sites. The threats and challenges of contaminated sites and the high costs of securing/remediating the problems highlight the need for a comprehensive approach based upon integrated pollution prevention and control. If applied to all polluting (and potentially polluting) industrial sectors around the globe, such an approach will prove to be both the cheapest and most sustainable way to underpin the development of industries in developing and transition economies.     

Sorption and Desorption Behavior of Chloroanilines and Chlorophenols on Montmorillonite and Kaolinite

The bioavailability of pollutants, pesticides and/or their degradation products in soil depends on the strength of their sorption by the different soil components, particularly by the clay minerals. This study reports the sorption-desorption behavior of the environmentally hazardous industrial pollutants and certain pesticides degradation products, 3-chloroaniline, 3,4-dichloroaniline, 2,4,6-trichloroaniline, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol on the reference clays kaolinite KGa-1 and Na-montmorillonite SWy-l. In batch studies, 2.0 g of clay were equilibrated with 100.0 mL solutions of each chemical at concentrations ranging from 10.0 to 200.0 mg/L. The uptake of the compounds was deduced from the results of HPLC-UV-Vis analysis. The lipophilic species were best retained by both clay materials. The most lipophilic chemical used in the study, 2,4,6-trichloroaniline, was also the most strongly retained, with sorption of up to 8 mg/g. In desorption experiments, which also relied on HPLC-UV-Vis technique, 2,4,6-trichloroaniline was the least desorbed from montmorillonite. However, on kaolinite all of the compounds under study were irreversibly retained. The experimental data have been modelled according to the Langmuir and Freundlich isotherms. A hypothesis is proposed concerning the sorption mechanism and potential applications of the findings in remediation strategies have been suggested.     

Persistence and dissipation kinetics of trifloxystrobin and tebuconazole in onion and soil

The persistence and dissipation kinetics of trifloxystrobin and tebuconazole on onion were studied after application of their combination formulation at a standard and double dose of 75 + 150 and 150 + 300 g a.i. ha^?1. The fungicides were extracted with acetone, cleaned-up using activated charcoal (trifloxystrobin) and neutral alumina (tebuconazole). Analysis was carried out by gas chromatograph (GC) and confirmed by gas chromatograph mass spectrometry (GC-MS). The recovery was above 80% and limit of quantification (LOQ) 0.05 mg kg^?1 for both fungicides. Initial residue deposits of trifloxystrobin were 0.68 and 1.01 mg kg^?1 and tebuconazole 0.673 and 1.95 mg kg^?1 from standard and double dose treatments, respectively. Dissipation of the fungicides followed first-order kinetics and the half life of degradation was 6–6.6 days. Matured onion bulb (and field soil) harvested after 30 days was free from fungicide residues. These findings suggest recommended safe pre-harvest interval (PHI) of 14 and 25 days for spring onion consumption after treatment of Nativo 75 WG at the standard and double doses, respectively. Matured onion bulbs at harvest were free from fungicide residues.     

Synthesis and characterization of m- and p-methylbenzyl-mercapturic acids derived from m- and p-xylenes

Chemical synthesis and physical properties of two mercapturic acids suggested as urinary metabolites of m- and p-xylenes ace described. These compounds may be used for the identification and quantivative determination by high-performance liquid chromatography of the corresponding mercapturic acids in urine.     

Field and laboratory studies of the fate and enantiomeric enrichment of venlafaxine and O-desmethylvenlafaxine under aerobic and anaerobic conditions

The stereoselectivity of R,S-venlafaxine and its metabolites R,S-O-desmethylvenlafaxine, N-desmethylvenlafaxine, O,N-didesmethylvenlafaxine, N,N-didesmethylvenlafaxine and tridesmethylvenlafaxine was studied in three processes: (i) anaerobic and aerobic laboratory scale tests; (ii) six wastewater treatment plants (WWTPs) operating under different conditions; and (iii) a variety of wastewater treatments including conventional activated sludge, natural attenuation along a receiving river stream and storage in operational and seasonal reservoirs. In the laboratory and field studies, the degradation of the venlafaxine yielded O-desmethylvenalfaxine as the dominant metabolite under aerobic and anaerobic conditions. Venlafaxine was almost exclusively converted to O-desmethylvenlafaxine under anaerobic conditions, but only a fraction of the drug was transformed to O-desmethylvenlafaxine under aerobic conditions. Degradation of venlafaxine involved only small stereoisomeric selectivity. In contrast, the degradation of O-desmethylvenlafaxine yielded remarkable S to R enrichment under aerobic conditions but none under anaerobic conditions. Determination of venlafaxine and its metabolites in the WWTPs agreed well with the stereoselectivity observed in the laboratory studies. Our results suggest that the levels of the drug and its metabolites and the stereoisomeric enrichment of the metabolite and its parent drug can be used for source tracking and for discrimination between domestic and nondomestic wastewater pollution. This was indeed demonstrated in the investigations carried out at the Jerusalem WWTP.     

Levels of PCDDs and PCDFs in products and effluent from the Swedish pulp and paper industry and chloralkali process

Within the Swedish Dioxin Survey various samples from the pulp and paper industry and the chloralkali process have been analyzed by congener specific analytical methods. In addition to the generally discussed “bleaching pattern” of the tetrachlorinated congeners, these samples also contained higher chlorinated congeners like hexa-CDDs, hepta-CDFs, octa-CDD and octa-CDF. Consequently it is recommended that samples from the pulp industry should be analyzed for all PCDDs and PCDFs (tetra- through octa-). Counted as Nordic Toxic Equivalents (NTEQ), the recycled pulp samples had the highest contamination level followed by TMP, unbleached sulfite and bleached softwood and hardwood. In addition to the bleaching process, various chemicals used in the pulping, bleaching and wastewater treatment can contribute to the contamination.     

Uptake and translocation of metformin, ciprofloxacin and narasin in forage- and crop plants

Transfer of bioactive organic compounds from soil to plants might represent animal and human health risks. Sewage sludge and manure are potential sources for bioactive compounds such as human- and veterinary drugs. In the present study, uptake of the anti-diabetic compound, metformin, the antibiotic agent ciprofloxacin and the anti-coccidial narasin in carrot (Daucuscarota ssp. sativus cvs. Napoli) and barley (Hordeumvulgare) were investigated. The pharmaceuticals were selected in order to cover various chemical properties, in addition to their presence in relevant environmental matrixes. The root concentration factors (RCF) found in the present study were higher than the corresponding leaf concentration factors (LCF) for the three test pharmaceuticals. The uptake of metformin was higher compared with ciprofloxacin and narasin for all plant compartments analyzed. Metformin was studied more explicitly with regard to uptake and translocation in meadow fescue (Festucapratense), three other carrot cultivars (D.carota ssp. sativus cvs. Amager, Rothild and Nutri Red), wheat cereal (Triticumaestivum) and turnip rape seed (Brassicacampestris). Uptake of metformin in meadow fescue was comparable with uptake in the four carrot cultivars (RCF 2-10, LCF approximately 1.5), uptake in wheat cereals were comparable with barley cereals (seed concentration factors, SCF, 0.02-0.04) while the accumulation in turnip rape seeds was as high as 1.5. All three pharmaceuticals produced negative effects on growth and development of carrots when grown in soil concentration of 6-10 mg kg⁻¹ dry weight.     

Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene

The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C₂ through C₈ organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene.     

Aerobic and anaerobic degradation of profluralin and trifluralin

Abstract

The degradation of profluralin [N‐(cyclopropylmethyl)‐α,α,α‐trifluoro‐2,6‐dinitro‐N‐propyl‐]p‐toluidine] and trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) was studied under aerobic and anaerobic soil conditions. Three soils (Goldsboro loamy sand, Cecil loamy sand, Drummer clay loam) were each treated with 1 ppmw herbicide; anaerobic conditions were maintained by flooding. Soil samples were extracted monthly and subjected to TLC analysis. No degradation was detected in sterile controls. Aerobic degradation of both herbicides was greatest in the Cecil loamy sand soil over the entire incubation period. Degradation of profluralin in Cecil soil under aerobic conditions was 86 percent after 4 months with three products detected; 83 percent of the trifluralin was degraded with two products detected. Anaerobic degradation accounted for 72 percent of the profluralin and 78 percent of the trifluralin after 4 months. Degradation of both herbicides increased with incubation time for the first 3 months and decreased slightly thereafter. Generally there was more extensive degradation (percent and in number of products formed) of profluralin than trifluralin under the conditions tested. More degradation products were detected for both herbicides under aerobic conditions than under anaerobic conditions.     

Sources and distribution of polychlorinated-dibenzo-p-dioxins and -dibenzofurans in soil and sediment from the Yellow Sea region of China and Korea

Polychlorinated-dibenzo-p-dioxins and -dibenzofurans (PCDD/Fs) were measured in soils and sediments from the Yellow Sea region. Korean soils and sediments mostly contained detectable PCDD/Fs and showed a widespread distribution among locations. Soil and sedimentary PCDD/Fs from China were comparable to or less than those in Korea. The patterns of relative concentrations of individual congeners in soils were different between the two countries, but similar in sediments. Sources of PCDD/Fs in China and Korea were found to be independent of each other and their distributions reflected matrix-dependent accumulation. Spatial distribution indicated some point sources in Korea while Chinese sources were more widespread and diffuse. PCDD/Fs measured in the coastal areas of the Yellow Sea were comparable to or less than those previously reported in for eastern Asia. However, ∑TEQs in soils and sediments were near to or, in some cases exceeded environmental quality guidelines.