禾草灵对水稻生长和典型土壤酶活性的影响

禾草灵是一种广泛使用的除草剂,在土壤中大量残留,对非靶标生物产生危害。为探究除草剂对环境生物的毒性作用,本研究模拟水稻自然生长的环境,评估禾草灵对水稻及土壤微生物的影响。研究结果表明,低浓度禾草灵(200 μg L^-1)处理4 d对土壤微生物量没有显著影响(P>0.05);8 d时,水稻生长没有明显变化,但土壤微生物量较对照组显著升高(P<0.05)。高浓度禾草灵(1 000 μg L^-1)处理4天后,土壤脲酶、酸性磷酸酶和过氧化氢酶的活性显著下降(P<0.05),下降幅度分别为8.9%,16.6%和10.2%;处理8 d后,水稻幼苗鲜重显著降低(P>0.05),叶绿素a和叶绿素b含量分别下降了13.5%和13.3%。本研究证实高浓度的禾草灵残留会对植物和土壤微生物产生不良的影响。     

7种农药对管氏肿腿蜂的毒性及初级风险评价

为评估农药对寄生类自然天敌昆虫的安全性,选择管氏肿腿蜂(Scleroderma guani Xiao et Wu)作为受试生物,采用管测药膜法测定了3种杀虫剂、2种除草剂、2种杀菌剂对其致死效应,并根据田间推荐剂量计算暴露量,采用风险商值HQ对杀虫剂进行风险评估。结果显示,与空白对照比较,3种杀虫剂均具明显毒性作用,其中丁硫克百威、吡虫啉和呋虫胺对管氏肿腿蜂的24 h半致死量(24 h-LR50)分别为5.11、2.92和0.06 g a.i.·ha-1,农田内风险商值分别为60.23、16.64和3 105。除草剂和杀菌剂在3倍最大田间推荐剂量作用下,24 h管氏肿腿蜂死亡率均小于50%。上述结果表明,在田间推荐用量下,3种杀虫剂对管氏肿腿蜂的初级风险评价为存在高风险,建议进一步开展高级阶段风险评估或者采取合理的风险管理措施来降低风险;除草剂和杀菌剂对管氏肿腿蜂的风险可接受。     

Removal of sulfamethoxazole and sulfapyridine by carbon nanotubes in fixed-bed columns

Sulfamethoxazole (SMX) and sulfapyridine (SPY), two representative sulfonamide antibiotics, have gained increasing attention because of the ecological risks these substances pose to plants, animals, and humans. This work systematically investigated the removal of SMX and SPY by carbon nanotubes (CNTs) in fixed-bed columns under a broad range of conditions including: CNT incorporation method, solution pH, bed depth, adsorbent dosage, adsorbate initial concentration, and flow rate. Fixed-bed experiments showed that pH is a key factor that affects the adsorption capacity of antibiotics to CNTs. The Bed Depth Service Time model describes well the relationship between service time and bed depth and can be used to design appropriate column parameters. During fixed-bed regeneration, small amounts of SMX (3%) and SPY (9%) were irreversibly bonded to the CNT/sand porous media, thus reducing the column capacity for subsequent reuse from 67.9 to 50.4 mg g^?1 for SMX and from 91.9 to 72.9 mg g^?1 for SPY. The reduced column capacity resulted from the decrease in available adsorption sites and resulting repulsion (i.e., blocking) of incoming antibiotics from those previously adsorbed. Findings from this study demonstrate that fixed-bed columns packed with CNTs can be efficiently used and regenerated to remove antibiotics from water.     

Modeling cold soak evaporative vapor emissions from gasoline-powered automobiles using a newly developed method

ABSTRACT

Volatile organic compounds (VOCs) evaporate and vent from a vehicle’s fuel tank to its evaporative control system when the vehicle is both driven and parked. VOCs making it past the control system are emissions. Driving and parking activity, fuel volatility, and temperature strongly affect vapor generation and the effectiveness of control technologies, and the wide variability in these factors and the sensitivity of emissions to these factors make it difficult to estimate evaporative emissions at the macro level. Established modeling methods, such as COPERT and MOVES, estimate evaporative emissions by assuming a constant in-use canister condition and consequently contain critical uncertainty when real conditions deviate from that standard condition. In this study, we have developed a new method to model canister capacity as a representative variable, and estimated emissions for all parking events based on semi-empirical functions derived from real-world activity data and laboratory measurements. As compared to chamber measurements collected during this study, the bias of the MOVES diurnal tank venting simulation ranges from ?100% to 129%, while the bias for our method’s simulation is 1.4% to 8.5%. Our modeling method is compared to the COPERT and MOVES models by estimating evaporative emissions from a Euro-3/4/5 and a Tier 2 vehicle in conditions representative for Chicago, IL, and Guangzhou, China. Estimates using the COPERT and MOVES methods differ from our method by ?56% to 120% and ?100% to 25%, respectively. The study highlights the importance for continued modeling improvement of the anthropogenic evaporative emission inventory and for tightened regulatory standards.

Implications: The COPERT and MOVES methodologies contain large uncertainties for estimating evaporative emissions, while our modeling method is developed based on chamber measurements to estimate evaporative emissions and can properly address those uncertainties. Modeling results suggested an urgent need to complete evaporative emissions inventories and also indicated that tightening evaporative emission standards is urgently needed, especially for warm areas.     

质子化壳聚糖的除磷性能

壳聚糖是一类无毒无害的天然高分子絮凝剂,为了提高壳聚糖在污水处理中的除磷性能,采用硫酸溶液对壳聚糖进行质子化改性;考察了质子化度(硫酸溶液pH值)、吸附时间以及原水pH值对除磷效率的影响。研究结果表明,质子化度越大,总磷去除效率越高;在吸附时间为40～50 min的范围内,总磷去除率最大;原水pH值对质子化壳聚糖的总磷去除效率有明显影响,在质子化度较低时(硫酸溶液pH值≥3),随着原水pH值的增加,总磷去除率降低,在质子化度较高时(硫酸溶液pH值=2),在原水pH=6时,总磷去除率最大;质子化壳聚糖的吸附过程较好地遵循Lagergren准二级动力学模型和Langmuir吸附等温方程,吸附热力学参数ΔH<0,ΔG<0,ΔS<0,吸附过程表现为放热、自发的单分子层化学吸附过程。     

不同粒径泥沙理化特性对磷吸附过程的影响

以北京大兴南海子湖表层沉积物为研究对象,测试分析了0.147～0.246 mm(细砂)、0.074～0.147 mm(极细砂)、0.0385～0.0740 mm(粉粒)和<0.0385 mm(粉粒粘粒混合物)4种粒径泥沙对磷的吸附行为,并采用相关分析及逐步回归分析探讨不同粒径沉积物中有机质(OM)、Fe、Al、Ca、Mn和TP含量对磷吸附过程的影响。结果表明,二级动力学方程和Langmuir模型能较好地描述南海子不同粒径泥沙的吸附动力学及等温吸附过程(R2>0.90)。粒径对单位质量泥沙吸附磷量具有明显影响,粉粒粘粒混合物>粉粒>细砂>极细砂。总体上,泥沙有机质(OM)、TP、Fe、Al、Ca和Mn含量随粒径的减小而增大,且粘粒对其影响较大。不同粒径泥沙(OM)、Fe、Al、Ca和Mn含量之间存在极显著正相关关系(P<0.01),且均对单位质量泥沙最大吸附量(Xm)和饱和吸附量(Cse)具有正效应,其中Al含量对该参数的影响更为显著。这说明泥沙对磷的吸附行为可能受到粒径和化学成分的共同影响。     

利用CRT屏玻璃制备板状泡沫玻璃

以废旧阴极射线管(CRT屏)为主要原料,混合碳粉作为发泡剂,硼砂为助熔剂、稳泡剂,利用烧结法制备出的板状泡沫玻璃是一种高性能无机建筑保温材料。利用TG-DSC-MS研究分析了CRT屏玻璃的热性能与发泡剂协同作用的关系。配合料被预先压制成板块状,然后在发泡温度下进行烧成。研究了发泡剂碳粉的含量、发泡温度和发泡时间与其结构、性能的关系。研究分析表明,以废CRT屏玻璃为主要原料、碳粉为发泡剂,将混合料压制成块,烧制出板状泡沫玻璃。其较佳的发泡温度为850℃、碳粉的最佳用量范围为0.3%～0.5%,较好的发泡时间为30 min。烧制的板状泡沫玻璃的密度为0.292 g/cm3。在相同的制备条件下,随着发泡温度的升高,气泡孔径也呈现增大趋势,孔壁也逐渐变薄。随着发泡时间逐渐增加,气孔的直径迅速增大,并有形成连通孔。     

超滤膜深度处理染整废水的膜污染机理

实验采用不同规格和材料的超滤膜进行染整二级尾水分离实验,对超滤膜污染机理及影响因素进行了分析。实验采用红外光谱分析了聚醚(PES)膜、聚砜(PSF)膜和聚醚酰亚胺(PEI)膜3种超滤膜材料,对比了污染前后膜面的接触角以及不同切割分子量对膜通量及出水水质的影响,并利用线性化的Herman堵塞模型拟合了不同分子量超滤膜的堵塞模型,初步探讨了超滤膜的污染机理。实验结果表明,膜材料表面亲水性基团的多少与初始膜通量大小成正比,出水COD值随超滤膜切割分子量减小而减小。切割分子量同为2 000 Da的3种超滤膜中,PES膜的处理效果最佳,出水COD平均值为47.81 mg/L;PEI膜通量最高,平衡通量可达50 L/(m2.h);切割分子量为1 000、10 000的超滤膜堵塞机理符合滤饼过滤模型,100 000的超滤膜堵塞机理更接近于完全堵塞模型;1 000的聚醚砜材质膜(PES)更适合此类废水的深度处理。     

利用沉水植物生长期收割进行富营养化水体生态管理的实地研究

在以再生水为补水水源的圆明园玉玲珑水域进行沉水植物收割实验,自2011年4—12月间每隔半个月监测一次水质。结果表明,通过在生长期收割沉水植物,玉玲珑水体TP、SRP、TN、NH4+-N、NO3--N和COD的平均浓度可维持在0.1、0.04、0.86、0.1、0.32和18 mg/L左右,水质保持在Ⅲ类至Ⅳ类地表水之间;与之对照的不收割沉水植物的玉玲珑进水口水域,9月沉水植物开始死亡腐烂,TP、SRP、TN、NH4+-N最高分别可达0.5、0.1、2.4和0.60 mg/L;作为对照的另一以挺水植物为主的水域,水质普遍劣于有大量沉水植物生长的水域,TP、SRP、TN、NH4+-N最高分别可达1.2、0.60、6.1和0.61mg/L。圆明园的实地实验表明,沉水植物有很强的净化水质作用,通过生长期收割,能够进一步强化其水质净化作用,可以作为一项对富营养化水体进行生态管理的有效措施进行推广。     

氧化物催化剂对非热等离子体催化降解甲苯的影响

考察了在干燥气氛下不同氧化物催化剂对非热等离子体催化降解甲苯的影响。从甲苯降解率、碳平衡、CO2选择性和O3去除4个方面,对比了氧化物催化剂的介电性能、表面供氧能力和比表面积与多孔结构对反应产生影响的强弱。结果表明,催化剂的介电性能有利于甲苯降解率、碳平衡和O3产量的提高,但对CO2选择性和O3去除的影响极小;一定能量密度下,催化剂比表面积与多孔结构对CO2选择性和O3去除所产生的影响要强于介电性能;催化剂表面供氧能力可明显促进反应的进行,其对反应所产生的影响要强于比表面积与多孔结构。