北京地区地表水中OCPs和PCBs的污染分析

在夏、冬两季对北京地区密云,潮白河,玉渊潭和通惠河等地表水中17种有机氯农药（OCPs）和84种多氯联苯（PCBs）的含量进行了分析及来源解析.实验结果表明,OCPs总量在7.86～53.1ng/L之间,平均值为（16.9±14.6）ng/L.PCBs总量在2.99～32.7ng/L之间,平均浓度为（10.9±10.4）ng/L.HCHs,硫丹,DDTs和HCB是主要的OCPs污染物,其含量分别为（13.9±11.5）ng/L,（2.20±2.01）ng/L,（0.63±1.51）ng/L和（0.12±0.14）ng/L.α-HCH/γ-HCH平均比值为1.53,小于工业HCH中比值4～7,表明北京地区地表水中存在林丹的使用.而DDT/（DDD+DDE）比值<1.22,表明北京地区并无新的DDTs污染源输入环境.PCBs以低氯代联苯为主,其中二氯,三氯,四氯和五氯联苯总和占∑₈₄PCBs总量的79.2%.北京地区地表水中不同氯取代数PCBs组成与我国历史PCB产品组成相符,均以低氯代联苯为主,表明北京地区地表水中PCBs污染来源为历史使用.相比于国内其他区域水质而言,北京地区地表水OCPs和PCBs污染水平较低.     

Investigation of correlativity between heavy metals concentration in indigenous plants and combined pollution soils

The accumulation of heavy metals (HMs) in soils is potentially hazardous to human, livestock and plant species. HMs in the combined pollution soils and indigenous plants were investigated in a non-ferrous metal-smelting area. The purpose of this study was to determine the HMs in the contaminated soil and different plant species found growing on it, as well as calculation of bioaccumulation coefficients (BACs). Representative sampling sites were identified according to the land-use types. A total of 12 surface soil samples and 32 plant samples were collected. HMs were analysed by inductively coupled plasma mass spectrometry. The levels of soil pollution were assessed using Nemerow’s synthetical contamination index method. The synthetical index was in the range of 16.81–198.11. This result indicated a heavy burden on local environment. HM concentrations in plants were directly related with soil concentrations. The average BACs of five metals were found in the order of Cd (0.309)?>?Zn (0.178)?≈?Pb (0.160)?>?Cu (0.105)?>?Sb (0.0672). Spontaneous weeds including Chenopodium album Linn, Kochia scoparia and trees of Leuce, Ulmus pumila were deemed HM accumulators. The results provided a practical basis for phytoremediation of HM-contaminated soils using accumulator species.     

New insights into FeS/persulfate system for tetracycline elimination: Iron valence, homogeneous-heterogeneous reactions and degradation pathways

In this study, complete tetracycline（TTC） and above 50% of total organic carbon（TOC） were removed by Fe S/PS after 30 min under optimized conditions. Although free radicals and high-valent iron ions were identified to generate in the process, the apparent similarity between intermediate products of Fe S/PS, Fe/PS, and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals(SO₄^·-) and hydroxyl radicals（ ·OH）. Based on the reaction between free radi...     

Evaluation on exposures to particulate matter at a junior secondary school: a comprehensive study on health risks and effective inflammatory responses in Northwestern China

Air pollutant measurement and respiratory inflammatory tests were conducted at a junior secondary school in Xi’an, Northwestern China. Hazardous substances including particulate matters (PMs), black carbon (BC) and particle-bounded polycyclic aromatic hydrocarbons (PAHs) were quantified both indoors and outdoors of the school. Source characterization with organic tracers and particle-size distribution demonstrated that the school’s air was mostly polluted by combustion emissions from the surrounding environment. The evaluation of health assessment related to air quality was conducted by two methods, including potential risk estimation of air pollutants and direct respiratory inflammatory test. The incremental lifetime cancer risks associated with PAHs were estimated and were 1.62 × 10⁻⁶ and 2.34 × 10⁻⁶, respectively, for indoor and outdoor fine PMs. Both the values exceeded the threshold value of 1 × 10⁻⁶, demonstrating that the carcinogenic PAHs are a health threat to the students. Respiratory inflammatory responses of 50 students who studied in the sample classroom were examined with a fractional exhaled nitric oxide (FeNO) test, with the aid of health questionnaires. The average FeNO concentration was 17.4 ± 8.5 ppb, which was slightly lower than the recommended level of 20 ppb established by the American Thoracic Society for children. However, a wide distribution and 6% of the values were > 35 ppb, suggesting that the potentials were still high for eosinophilic inflammation and responsiveness to corticosteroids. A preliminary interpretation of the relationship between air toxins and respiratory inflammatory response demonstrated the high exposure cancer risks and inflammatory responses of the students to PMs in the city.

     

Biomarkers as tools to assess the chronic toxicity of ammonia in the juvenile Mugil cephalus

With juvenile fish as the subject, the effects of low concentration ammonia on antioxidant system were studied using Mugil cephalus. Samples of gill and liver tissue were obtained from 0.35, 0.70, 1.5 and 3?mg/L ammonia groups at 0, 5, 10, 15 and 20 days of exposure, at which times the biomarkers were measured. Results showed that gill malondialdehyde (MDA) content exhibited an initial significant increase (p?≤?0.05) at unionised ammonia concentrations of 0.70, 1.5 and 3.0?mg/L on day 5, followed by subsequent declines, while liver MDA levels exhibited significant increases (p?≤?0.05) at unionised ammonia concentrations of 1.5?mg/L starting on day 10 and at 3.0?mg/L starting on day 5. With exposure to ammonia at different concentrations, Na⁺-K⁺-ATPase activity in liver and gill decreased over time. The Na⁺-K⁺-ATPase activity was negatively related to ammonia concentration from 0.70 to 3.0?mg/L. Overall, our results show that MDA and Na⁺-K⁺-ATPase, evaluated here as potential biomarkers of ammonia exposure, exhibited responses to sublethal concentrations of ammonia that were concentration dependent.     

Characteristics of N2O emission from Medicago sativa stands and its response to nitrogen fertilizers in the Longdong dryland Plateau北大核心CSCD

Nitrous oxide (N2O) is one of the potent greenhouse gases (GHG) that depletes the stratospheric ozone. Nitrogen fertilizers are considered to be a major source of nitrous oxide (N2O) emissions from arable soils. To investigate the characteristics of N2O emission, its influencing factors, and its response to nitrogen application in dry grassland in the Loess Plateau, one of the most intensively used agricultural regions in China, we conducted a field trial with two treatments including N0 (0 kg hm-2) and N150 (150 kg hm-2) at the Qingyang Loess Plateau grassland agricultural research station of Lanzhou University. An LGR-N2O/CO gas analyzer was used to monitor the emissions. The results showed that the N2O fluxes of the N0 and N150 treatments during the monitoring period were -0.0036 and 0.0118 mg m-2 h-1, respectively; the flux in case of the N150 treatment was significantly higher than that for the N0 treatment. The N2O emission flux has a distinct diurnal variation characteristic, which first showed the trend of decreasing and then increasing. Regression analysis indicated a significant positive correlation between the N2O flux and the surface soil water content at a depth of 10 cm. The N2O emission flux increased by 131.3%, compared with that during the non-precipitation days. At the same time, the N2O emission flux showed a trend of decreasing with the increase of the surface soil temperature at a depth of 10 cm. The daily emission characteristics indicated that there may be a significant underestimation of the N2O flux at the daily or longer time-scale, based on the N2O flux value measured at 9:00-11:00. In summary, the N2O emissions from the sown alfalfa grassland of the eastern Gansu are strongly affected by precipitation and nitrogen application and have obvious daily dynamic characteristics. It is recommended that the accuracy and representativeness of N2O emission flux data be enhanced by continuous dynamic measurement using the instrument. © 2018 Science Press. All rights reserved.     

氯霉素对大型溞的急性和慢性毒性效应研究

氯霉素是一种具有广谱杀菌作用的抗生素,曾在水产养殖中广泛使用,虽然目前已被列入我国渔药禁用清单,但在水环境中仍被大量检出。为探究氯霉素对水生生物的毒性作用,选择大型溞(Daphnia magna)作为受试生物,研究氯霉素对其急性毒性和慢性毒性效应,同时建立了氯霉素的高效液相色谱(HPLC)分析方法,通过实测浓度分析确保实验过程中氯霉素浓度保持在可接受范围内。结果表明:氯霉素对大型溞的48 h半数抑制浓度(EC50)为129.5 mg·L~(-1),95%置信区间为124.4!150.9mg·L~(-1),对溞类的急性毒性为低毒;长期暴露能抑制大型溞的产溞数量,以繁殖量为毒性指标,21 d无可观察效应浓度(NOEC)为1.25 mg·L~(-1),最低可观测效应浓度(LOEC)为2.50 mg·L~(-1);各暴露组实测浓度范围在配制浓度的80%～110%,保证了实验的有效性。同时,利用实验获得的急慢性毒性数据,计算氯霉素对大型溞的急慢性毒性比(ACR),发现利用慢性毒性求得的ACR值比利用急性毒性EC10求得的ACR值更接近推荐值。研究表明氯霉素对大型溞的急性毒性低,但具有慢性毒性效应,其环境风险不容忽视。     

土石坝溃决机理模型试验研究进展

大坝溃决将给人类社会带来巨大的灾难,因此国内外都很关注溃坝问题的研究。由于多数大坝均为土石坝,且土石坝是逐渐溃决的过程,而混凝土坝一般表现为瞬时溃决,因此土石坝溃决机理与溃决过程的研究对于溃坝过程数学模型的建立和致灾后果的评价具有重要的指导意义。自20世纪90年代以来,国内外学者围绕土石坝溃决机理开展了广泛深入的模型试验研究,取得了一系列重要的研究成果。分别从土石坝溃决原因、土石坝溃决机理研究进展、土石坝漫顶溃决模型试验、土石坝管涌溃决模型试验等方面介绍国内外的研究进展。重点针对土石坝坝型(均质坝、黏性心墙坝、面板堆石坝)和主要破坏模式(漫顶溃坝与管涌溃坝),介绍国内外开展的不同尺度的溃坝模型试验,分析研究了土石坝的溃决机理,并对今后的研究工作重点提出了相关建议。     

信息素调控质粒介导的粪肠球菌耐药基因接合转移机制研究进展

粪肠球菌是一种在自然环境中广泛存在的革兰氏阳性细菌.由于其特殊的耐药机制及高频率的耐药基因转移方式,导致了环境中耐药粪肠球菌的广泛传播,生态安全形势严峻.其中,信息素应答质粒介导的粪肠球菌耐药基因的接合转移是造成粪肠球菌耐药基因快速扩散的重要方式.本文回顾了近些年关于信息素应答质粒接合转移的研究成果,分析总结了接合转移的必要条件、正负调控信息素对接合转移的调节作用,并以携带四环素抗性的质粒pCF10为例简要探讨了接合转移相关基因、蛋白的调控机制,旨在更加全面地揭示粪肠球菌的耐药基因传播机制,为耐药细菌的基因转移机制研究提供参考.     

双台子河与大辽河表层水体微塑料特征与分布研究

微塑料是全球新兴环境热点问题之一.据估算,80％的海洋微塑料来于陆源输入,而河流被认为是陆源微塑料输入海洋的主要路径之一.为揭示辽河流域水体微塑料污染特征、空间分布及其对渤海微塑料污染的潜在贡献,本文基于密度分离原理并利用傅里叶变换红外光谱方法,研究了双台子河与大辽河下游至入海口(盘锦段)河道表层水体微塑料丰度、材质组成、形态特征与粒径分布特征.结果显示:从材质上分析,2条河流共检出了17种高分子聚合物,其中以聚乙烯占比最高,分别占双台子河和大辽河表层微塑料总量的38％和32％;从形态上分析,碎片微塑料(533.08～674.25μm)和纤维微塑料(1054.87～1450.76μm)分别占2条河流检出微塑料总量的80％以上,颗粒微塑料(100.26～241.3μm)占比则低于10％,并且没有检出形状规则的塑料微珠;从丰度上分析,双台子河((4.52±0.76)个·L-1)与大辽河((4.74±0.67)个·L-1)表层水体微塑料丰度之间无显著差异(P>0.05),并且各点之间也没有明显的变化趋势(P>0.05).以上研究结果表明,双台子河与大辽河表层水体微塑料污染特征相似,这为开展渤海微塑料溯源和风险管理提供了直接依据.