Nutrients regeneration pathway, release potential, transformation pattern and algal utilization strategies jointly drove cyanobacterial growth and their succession

In order to better understand the contribution of nutrients regeneration pathway, release potential and transformation pattern to cyanobacterial growth and succession, 7 sampling sites in Lake Chaohu with different bloom degree were studied every two months from February to November 2018. The carbon, nitrogen (N) and phosphorus (P) forms or fractions in surface, interstitial water and sediments as well as extracellular enzymatic activities, P sorption, specific microbial abundance and community composition in sediments were analyzed. P regeneration pathway was dominated by iron-bound P desorption and phosphorus-solubilizing bacteria solubilization in severe-bloom and slight-bloom area respectively, which both resulted in high soluble reactive phosphorus (SRP) accumulation in interstitial water. However, in severe-bloom area, higher P release potential caused the strong P release and algal growth, compared to slight-bloom area. In spring, P limitation and N selective assimilation of Dolichospermum facilitated nitrate accumulation in surface water, which provided enough N source for the initiation of Microcystis bloom. In summer, the accumulated organic N in Dolichospermum cells during its bloom was re-mineralized as ammonium to replenish N source for the sustainable development of Microcystis bloom. Furthermore, SRP continuous release led to the replacement of Dolichospermum by Microcystis with the advantage of P quick utilization, transport and storage. Taken together, the succession from Dolichospermum to Microcystis was due to both the different forms of N and P in water column mediated by different regeneration and transformation pathways as well as release potential, and algal N and P utilization strategies.     

中国稻田土壤镉污染及务农性暴露概率风险

为了解中国稻田土壤镉污染时空变异特征及其务农性接触的健康风险,对1991~2017年发表的205篇有关稻田土壤镉调查文献进行系统回顾,并采用USEPA推荐的健康风险评估概率模型对健康风险进行评估.结果表明,全国稻田土壤镉平均浓度[（0.54±1.38）mg/kg]显著高于全国表层土壤镉背景值（0.097mg/kg）.虽未见显著的时间变异（β=-0.002,95%置信区间：-0.025~0.022）,但不同地区和不同人为扰动下的稻田土壤镉浓度存在较大异质性：华南[（0.88±1.59）mg/kg]>西南[（0.46±0.85）mg/kg]>华东[（0.44±1.45）mg/kg]>华北[（0.36±1.05）mg/kg]>东北[（0.35±0.83）mg/kg]>西北[（0.01±0.05）mg/kg]和矿冶[（1.77±2.18）mg/kg]>其他工业活动[（0.64±1.22）mg/kg]>电子垃圾拆解[（0.59±0.87）mg/kg]>污灌[（0.57±1.26）mg/kg]>交通[（0.56±0.86）mg/kg]>常规稻田[（0.25±0.34）mg/kg].除西北地区外,各地区稻田土壤镉浓度均出现不同程度的超标现象,尤其华南地区34%条土壤镉浓度数据超过农用地土壤镉污染风险管制值（1.5mg/kg）.土壤镉务农性接触的非致癌风险（HQ<<1）处于可接受水平,其中皮肤接触是主要途径,女性是务农性土壤镉暴露的高风险人群,华南和西南地区是务农性土壤镉暴露的高风险地区.     

重庆市主城区O3污染时期大气VOCs污染特征及来源解析

2020年8月底至9月初,重庆市主城区发生了持续时间近2周的O₃污染过程.期间,在主城区3个观测站点利用苏玛罐和DNPH采样柱采集的环境空气VOCs样品,研究了O₃污染期间VOCs组分特征、光化学反应活性及来源解析.结果表明,观测期间重庆市主城区TVOCs平均体积分数为45.08×10^-9,各组分体积分数排序依次为OVOCs、烷烃、卤代烃、烯烃、芳香烃和炔烃.体积分数较高的VOCs物种是甲醛、乙烯和丙酮,三者之和占比TVOCs超过30%.OVOCs和烯烃对· OH消耗速率（L_i^·OH）和臭氧生成潜势（OFP）均具有较大的贡献,是生成O₃的关键VOCs组分;其中,OVOCs组分中主要的活性物种为甲醛、乙醛和丙烯醛,烯烃组分中主要的活性物种为异戊二烯、乙烯和正丁烯.VOCs中二甲苯与乙苯的比值较低,并且两者呈现显著的相关性,表明主城区大气中VOCs气团老化程度高,同时还受到其他区域远距离传输的影响.PMF受体模型解析结果显示,主要有5种VOCs来源,依次为二次生成源（27.67%）、机动车尾气源（26.56%）、工业排放源（17.86%）、植物源（14.51%）和化石燃料燃烧源（13.4%）.     

室内木柴燃烧排放水溶性离子粒径分布特征

基于实验室模拟燃烧和稀释通道采样系统,采用荷电低压撞击采样器采集了6种典型木柴燃烧排放的14级粒径段颗粒物.采用离子色谱分析了8种水溶性离子,获得水溶性离子的分粒径排放因子和排放特征.结果表明,Ca²⁺的排放因子呈双峰分布,在0.25~0.38和2.5~3.6μm粒径段出现峰值,分别为0.14和0.16mg/kg.其余离子的排放因子为单峰分布.NH₄⁺、NO₃^-和SO₄^2-的排放因子在0.25~0.38μm粒径段出现峰值,分别为0.41、0.58和0.84mg/kg.K⁺和Cl^-的排放因子在0.15~0.25μm内出现峰值,分别为0.89和0.99mg/kg.木柴燃烧排放总水溶性离子的质量中值粒径为（0.30±0.07）μm,各离子的质量中值粒径范围为0.24~0.44μm.PM_0.094、PM_0.94、PM_2.5和PM₁₀中水溶性离子的排放因子变化范围分别为1.04~9.33、5.00~48.87、5.46~52.00和6.14~53.68mg/kg.木柴燃烧排放颗粒物中K⁺/Cl^-、K⁺/NO₃^-、K⁺/SO₄^2-和SO₄^2-/NO₃^-比值随粒径变化而变化,其排放初始值在应用于源解析和生物质燃烧排放气溶胶传输老化研究时需引起关注.木柴燃烧排放PM₁₀中的阴阳离子当量比值为0.80±0.11,颗粒物的酸度随颗粒物粒径而改变,亚微米颗粒物和细颗粒物的酸度高于超细颗粒物和粗颗粒物的酸度.本研究对构建生物质燃烧排放分粒径水溶性离子清单,更新和改进相关气候和空气质量模型的参数设置,识别烟气传输过程中的老化具有重要意义.     

基于摩擦纳米发电机的微塑料实时检测实验研究

采用基于自供电的摩擦纳米发电机(TENG)技术,设计开发了一种利用间断液柱检测水样内微塑料颗粒尺寸和丰度的实时快速检测方法和装置,并通过实验测试完成了对微塑料的尺寸形貌表征和化学元素组成的实时高效检测.研究发现,去离子水中加入微塑料颗粒时,溶液中zeta电位降低,改变了管壁表面的极化电场方向;随着水溶液中微塑料颗粒直径或丰度的增加,开路电压呈现减小趋势,50μm时减小了43.1%,0.250%浓度时减小了79.6%;微塑料颗粒对自来水的开路电压影响显著,以10μm微塑料颗粒为例,开路电压减小了20%,证明了TENG技术对海洋微塑料检测的可行性.     

Urinary analysis reveals high Alternaria mycotoxins exposure in the general population from Beijing, China

Alternaria mycotoxins are of concern due to its adverse health effect, they affect various cereal crops and grain-based food along with modified forms that contribute to overall exposure. This study aimed to determine the frequency and level of exposure to Alternaria mycotoxins (tenuazonic acid, TeA; alternariol, AOH; alternariol monomethyl ether, AME; tentoxin, TEN; and altenuene, ALT) in human urine from Beijing adults. A total of 2212 urine samples were collected and analyzed for five mycotoxins using LC–ESI–MS/MS. More than 98% of the samples had at least one Alternaria mycotoxin detected. Among the mycotoxins, AME had the highest detection rate (96.0%), followed by TeA (70.5%). The calculated average daily intake values of AME (12.5 ng/kg b.w.) was 5 times the TTC value (2.5 ng/kg b.w.) set by the EFSA, indicating the potential health risks associated with mycotoxins. Immediate attention and subsequent actions should be taken to identify the sources of mycotoxins and the corresponding exposure pathways to humans in the investigated regions.     

Chemical composition of different size ultrafine particulate matter measured by nanoparticle chemical ionization mass spectrometer

New particle formation (NPF) is the primary source of nanoparticles and contributes a large number of concentrations of cloud condensation nuclei. In recent years, field campaigns and laboratory experiments have been conducted to promote cognition of the mechanism for NPF and its following growth processes. The chemical composition measurement of nanoparticles could help deepen understanding of the initial step of particulate matter formation. In this work, we developed a nanoparticle chemical ionization mass spectrometer to measure nanoparticles' chemical compositions during their initial growth stage. Meanwhile, a non-radioactive ion source was designed for aerosol charging and chemical ionization. Time of flight mass spectrometer coupled with integrated aerosol size selection and collection module would guarantee the picogram level detection limit and high-resolution ability to measure the matrix of ambient samples. The performance of this equipment was overall evaluated, including the transmission efficiency and collection efficiency of custom-built nano differential mobility analyzer, chemical ionization efficiency, and mass resolution of the mass spectrometer. The high sensitivity measurement of ammonium sulfate and methylammonium sulfate aerosols with diameters ranging from 10 to 25 nm could guarantee the application of this instrument in the ambient measurement.     

Competing pathways of cresol formation in toluene photooxidation: OH-toluene adducts react with NO2 or with O2?

Methyl-hydroxy-cyclohexadienyl radicals (OTAs) are the key products of the photooxidation of toluene, with implications for the fate of toluene. Hence, we investigated the photooxidation mechanisms and kinetics of three main OTAs (o-OTA, m-OTA, and p-OTA) with NO₂ using quantum chemical calculations as well as the fate of OTAs under the different concentration ratios of NO₂ and O₂. The mechanism results show that the pathway of H-abstraction by NO₂ to anti-HONO (anti-H-abstraction) is more favorable than the syn-H-abstraction pathway, because the strong interaction between OTAs and NO₂ is formed in the transition states of the anti-H-abstraction pathways. The branching ratios of the anti-H-abstraction pathways are more than 99% in the temperature range of 216−298 K. The total rate constant of the OTA-NO₂ reaction is 9.9 × 10⁻¹² cm³/(molecule∙sec) at 298 K, which is contributed about 90% by o-OTA + NO₂, and the main products are o-cresol and anti-HONO. The half-lives of the OTA-NO₂ reaction in some polluted areas of China are 35 times longer than those of the OTA-O₂ reaction. In the atmosphere, the NO₂- and O₂- initiated reactions of OTAs have the same ability to form cresols as [NO₂] is up to 142.1 ppmV, which is impossible to achieve. It implies that under the experimental condition, the [NO₂]/[O₂] should be controlled to be less than 7.8 × 10⁻⁵ to simulate real atmospheric oxidation of toluene. Our results reveal that for the photooxidation of toluene, the yield of cresol is not affected by the concentration of NO₂ under the atmospheric environment.     

Response of PM2.5-bound elemental species to emission variations and associated health risk assessment during the COVID-19 pandemic in a coastal megacity

The coronavirus (COVID-19) pandemic is disrupting the world from many aspects. In this study, the impact of emission variations on PM_2.5-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic. Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown. After the lockdown, they rebounded rapidly, of which V and Ni even exceeded the levels before the lockdown, suggesting the recovery of both inland and shipping activities. Five sources were identified based on receptor modeling. Coal combustion accounted for more than 70% of the measured elemental concentrations before and during the lockdown. Shipping emissions, fugitive/mineral dust, and waste incineration all showed elevated contributions after the lockdown. The total non-carcinogenic risk (HQ) for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ. Whereas, the total carcinogenic risk (TR) for adults was above the acceptable level and much higher than that for children. Waste incineration was the largest contributor to HQ, while manufacture processing and coal combustion were the main sources of TR. Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk. From the perspective of health effects, priorities of control measures should be given to waste incineration, manufacture processing, and coal combustion. A balanced way should be reached between both lowering the levels of air pollutants and their health risks.     

Effects of co-exposure to lead and manganese on learning and memory deficits

Lead (Pb) and manganese (Mn) are common neurotoxins. However, individuals are subject to co-exposures in real life, and it is therefore important to study these metals in combination. Weaning Sprague-Dawley rats were given ad libitum access to drinking water solutions containing Pb (100 mg/L), Mn (2.5 mg/mL) or a mixture, and each treatment had its own minocycline (50 mg/(kg•day)) supplement group. The results showed a significant difference in spatial memory and induction levels of hippocampal long-term potentiation (LTP) in all exposure groups when compared with controls. The combined-exposure group exhibited the most pronounced effect when compared with each of the single-metal exposure groups. Microglia displayed activation at day 3 after exposure alone or in combination, while astrocytes showed activation at day 5, accompanied by decreased expression levels of GLAST, GLT-1, and GS. Furthermore, the levels of glutamate in the synaptic cleft increased significantly. When microglial activation was inhibited by minocycline, the activation of astrocytes and the expression of GLAST, GLT-1, and GS were both reversed. In addition, upon minocycline treatment, hippocampal LTP impairment and cognitive injury were significantly alleviated in each of the exposure groups. These results suggest that combined exposure to Pb and Mn can cause greater effects on cognition and synaptic plasticity when compared to single-metal exposure groups. The reason may involve abnormal activation of microglia leading to excessive regulation of astrocytes, resulting in glutamate reuptake dysfunction in astrocytes and leading to perturbed cognition and synaptic plasticity.