Characterization of demethylation of methylmercury in cultured astrocytes

Mercury (Hg) is a well-known neurotoxicant but its toxicity depends on the species present. A steady emergence of inorganic Hg in the brain following chronic and accidental exposure to methylmercury (MeHg) has suggested that MeHg can undergo demethylation. The objective of this study is to develop an in vitro model to study factors affecting Hg demethylation in the central nervous system. Astrocytes obtained from neonatal rat pups were cultured for 24h with 1 microM MeHg in the presence of two pro-oxidants, buthionine sulphoximine (BSO) and rotenone. The BSO treatment produced a 21% increase in reactive oxygen species (ROS) content compared to the control (control vs. BSO; 100+/-1.35 vs. 121+/-1.52 relative fluorescence units (RFU)mg(-1) protein, p<0.001) but did not affect total Hg accumulation (control vs. BSO=86.5+/-4.14 ng mg(-1) vs. 95.7+/-9.26 ng mg(-1)). Rotenone increased ROS levels 107% (control vs. rotenone; 100%+/-1.35 vs. 207%+/-6.78RFU mg(-1)protein, p<0.001) and significantly increased the accumulation of total Hg (control vs. rotenone=86.5+/-4.14 ng mg(-1) vs. 124+/-3.80 ng mg(-1), p<0.001). There was no detectable demethylation in the control or BSO treated group, however, the rotenone treatment significantly increased the demethylation (control vs. rotenone=-1.86+/-5.57% vs. 16.3+/-2.68%, p<0.05). For the first time, we have demonstrated in an in vitro primary astrocyte culture model that MeHg can be converted to inorganic Hg and demethylation increases with oxidative stress. Our results provide a useful model to study demethylation of Hg in astrocytes and to explore potential ways to protect against Hg toxicity.     

Sources and seasonal variation of PAHs in the sediments of drinking water reservoirs in Hong Kong and the Dongjiang River (China)

The main objective of this study was to investigate occurrence of polycyclic aromatic hydrocarbons (PAHs) in the sources of the drinking water supply of Hong Kong. The main emphasis was on the Dongjiang River in mainland China which is the major source, supplying 80% of the total consumption in Hong Kong (the remaining 20% is obtained from rain water). Sediments were collected from four sites along the Dongjiang River and four reservoirs in Hong Kong during both the dry and wet weather seasons. The concentrations of total PAHs in the sediments ranged between 36 and 539 microg/kg dry wt. The lower levels were detected at the upstream site on the Dongjiang River and at the reservoirs in Hong Kong (44-85 microg/kg dry wt), while the mid- and downstream sites on the Dongjiang River were more polluted (588-658 microg/kg dry wt). Examination of the PAH profiles revealed that the mid- and downstream sections of the Dongjiang River contained high percentages of 4,5,6-ring PAHs, similar to the amounts of atmospheric particulate matter and road dust collected during the dry weather season from the Pearl River Delta region as reported in the literature. Seasonal changes were revealed in the reservoirs of Hong Kong, with higher PAH levels in the wet weather season than in the dry weather season. For those reservoirs in Hong Kong that store water from the Dongjiang River, a distinct seasonal pattern was also observed, namely, that under dry weather season conditions the PAHs found in the sediments were primarily from petrogenic source, while under wet weather season conditions they were from pyrolytic sources. No such pattern was detected in the reservoirs which stored only rain water.     

基于余震序列分布信息的地震极灾区快速判断方法研究

利用震级加权标准差椭圆法研究了基于震后短期内(24 h)余震序列判定地震极灾区的方法,研究结果表明:1利用该方法判断宏观震中是一种比较可行的方法,不同震源破裂方式的震例利用该方法判断宏观震中的精度不同,倾滑-近倾滑型破裂方式的震例利用余震序列判定宏观震中的精度最高;2整体上看,利用该方法判断极灾区长轴方向的准确性低于利用距震中最近活动断裂判断的准确性,但对于倾滑-近倾滑型破裂方式的震例,利用该方法的准确性高于利用断层数据判定的准确性。     

长江重庆段表层水体中多环芳烃的分布及来源分析

采集了长江重庆段干流以及重要支流共7个断面的表层水样,采用液相色谱法分析15种优先控制的多环芳烃(PAHs).结果表明,水体中总PAHs浓度范围为6.44—109.39 ng·L-1,平均值为41.83 ng·L-1.在5个断面水体中检出苯并(a)芘,浓度为0.05—1.32 ng·L-1,低于我国地表水标准限值(2.8 ng·L-1).长江重庆段的PAHs浓度水平低于大部分国内其他河流,与国外一些河流的浓度水平相当.PAHs组成以中低环PAHs(3环和4环)为主,平均比例分别为55.7%和38.8%,高环PAHs(5环和6环)含量较低,分别占3.6%和1.9%.示踪PAHs比值法结果显示长江重庆段表层水体PAHs主要来源于石化产品的泄漏污染.     

不同碳氮比条件下鸡粪和椰糠高温堆肥腐熟过程研究

用鸡粪和椰糠作为基本堆肥原料进行高温堆肥试验,通过控制鸡粪和椰糠的添加量调节堆体初始C/N比,研究其对堆肥过程中堆体温度、p H值、C/N比及养分全量等理化指标的影响,探究鸡粪和椰糠高温堆肥的最适C/N比。结果表明,当C/N比为25时,堆体达到最高温度(57℃),且高温持续时间最长(14 d)。堆肥过程中各处理有机质、全碳、C/N比均呈下降趋势,p H值均呈先上升后下降趋势,全氮和种子发芽指数呈上升趋势。堆肥结束后,堆体F1(初始C/N比为20)、F2(初始C/N比为25)和F3(初始C/N比为30)的C/N比分别为11.13、11.19和10.24,总养分含量w分别为7.94%、8.63%和8.29%,种子发芽指数分别为77.90%、100.65%和93.30%。     

聚苯乙烯微塑料单独或与镉共同暴露诱导肝细胞铁死亡

微塑料作为一种新型污染物,易吸附并富集环境中的重金属等,广泛存在于大气、土壤和水体环境中,对人体的危害正受到广泛关注.微塑料与其吸附污染物引发的复合毒性效应及机制是目前微塑料环境毒理学评价中亟待解决的科学问题.本研究以聚苯乙烯微塑料和镉为研究对象,考察其对新型细胞死亡方式-铁死亡的诱导作用,发现微塑料和镉暴露诱导肝细胞线粒体形态异常和线粒体嵴减少、GSH水平下降、脂质过氧化损伤以及关键铁死亡调节蛋白GPX4表达量降低,证实微塑料和镉暴露可诱导肝细胞发生铁死亡;同时不同铁死亡抑制剂及毒性检测指标的测定还表明,Cd²⁺主要通过抑制膜脂修复膜GPX4活性,引起脂质过氧化,导致铁死亡发生;聚苯乙烯微塑料主要通过刺激活性氧产生促进铁死亡;二者复合体可同时通过活性氧和抑制酶活等方式促进铁死亡发生,但其发生程度弱于Cd²⁺,可能是由于复合体中Cd²⁺呈吸附态降低其部分毒性所致.本文预期将为深入评价微塑料与镉的复合毒性效应提供数据支撑,同时为微塑料与其它共存的有毒组分的复合毒性效应及机制研究提供一定参考.     

中国内陆流域地表水体光电化学特征研究

太阳辐射是自然界中最主要的能量来源.目前人们对自然界利用太阳能途径的认识主要集中于具有生物光采集系统（如叶绿体）的光合作用,而对于非生物光采集系统是否广泛存在于地表水体中仍不清楚.本研究通过测定全国范围内151个地表水样光生电子的能力,绘制了中国内陆流域地表水体光电化学特征图谱.通过利用XPS、XRD和EEM等手段表征水样悬浮态和溶解态物质组成,揭示了地表水体光电化学活性来源及其影响因素.结果显示,我国地表水体普遍存在光电化学活性.按生物质换算,我国地表水体光生电子每年可转化生物质当量约为1.4×10³~1.1×10⁴万t葡萄糖,相当于光合作用固碳总量的0.51%~4.02%.地表水体的光电流大小与光强和光敏物质浓度呈正相关,相关系数 分别达到0.99和0.99.水体的光电化学活性主要来源于悬浮态物质,其贡献度大于60%,与含Ti或含S的半导体矿物丰度呈正相关;而溶解态物质贡献较小（<40%）,其光电化学成分主要为溶解性有机质,并与腐殖酸类或富里酸类物质浓度呈正相关.本研究为自然界微生物光电能 营养作用的发生提供线索,同时也为量化自然地表水体太阳光引发的生物或非生物能量来源提供依据.     

长三角区域人为源活性挥发性有机物高分辨率排放清单

基于长三角区域41个城市本地实测,结合美国EPA的SPECIATE 4.4数据库,建立了长三角区域人为源活性挥发性有机物(VOCs)高分辨率排放清单,分析了区域内VOCs的排放特征和组分构成;计算了VOCs的臭氧生成潜势(OFP)和二次有机气溶胶生成潜势(SOAP).结果表明,2017年,长三角区域人为源VOCs排放总量为4.9×10⁶ t,其中工艺过程源、工业溶剂使用源、移动源、生活源、储运源、农业源和废弃物处理源排放贡献分别为：34.3%、27.1%、19.5%、9.7%、6.1%、2.5%和0.4%.芳香烃和烷烃是VOCs的主要种类,均各占长三角VOCs排放总量的25%.工艺过程源、工业溶剂使用源、移动源和生活源OFP贡献率分别为38.3%、21.5%、16.4%和13.2%,SOAP贡献率分别为26.2%、34.1%、18.1%和17.9%,与VOCs排放量的主要贡献源基本一致.各城市VOCs重点排放行业存在较大差异,重点城市群以石化化工和装备制造为主,区域北部则以木材家具等涂装行业为主.计算表明,丙烯、间/对-二甲苯和乙烯是臭氧主要贡献源;甲苯、1,2,...