徒骇河沉积物和沿岸土壤对磷酸盐的吸附动力研究

通过实验模拟的方法,研究了徒骇河沉积物和沿岸土壤对磷酸盐的吸附作用,发现二者均具有较强的对磷酸盐的吸附作用,沉积物的吸附作用强于土壤,沉积物在2h内即可达到吸附平衡,土壤在12h内达到平衡;在中等扰动条件下,随着磷酸盐浓度的上升,沉积物和土壤的磷酸盐吸附容量均明显增加,沉积物的吸附容量大于土壤,这种吸附能力对徒骇河水体的磷酸盐缓冲作用起着积极的作用;徒骇河沉积物和沿岸土壤对磷酸盐的吸附等温曲线符合Langmuir等温吸附方程。     

Biofuel development, food security and the use of marginal land in China

With concerns of energy shortages, China, like the United States, European Union, and other countries, is promoting the development of biofuels. However, China also faces high future demand for food and feed, and so its bioenergy program must try to strike a balance between food and fuel. The goals of this paper are to provide an overview of China's current bioethanol program, identify the potential for using marginal lands for feedstock production, and measure the likely impacts of China's bioethanol development on the nation's future food self-sufficiency. Our results indicate that the potential to use marginal land for bioethanol feedstock production is limited. Applying a modeling approach based on highly disaggregated data by region, our analysis shows that the target of 10 million t of bioethanol by 2020 seems to be a prudent target, causing no major disturbances in China's food security. But the expansion of bioethanol may increase environmental pressures due to the higher levels of fertilizer use. This study shows also that if China were able to cultivate 45% of its required bioethanol feedstock on new marginal land, it would further limit negative effects of the bioethanol program on the domestic and international economy, but at the expense of having to apply another 750 thousand t of fertilizer.     

崇明东滩沉积物再悬浮对沉积物-水界面氮、磷交换行为的影响

2002年7月采集崇明东滩低潮滩沉积物样和水样,运用模拟实验研究沉积物再悬浮作用对沉积物-水界面三态氮和可溶磷交换行为的影响实验发现,在沉积物不断发生再悬浮的过程中,水体中三态氮的含量明显增加,其中NO₃^--N变化最为显著,升高浓度值达11.869μmol·L^-1,NH₄⁺-N增长2.1713μmol·L^-1,NO₂^--N的释放约为0.2μmol·L^-1,可溶磷的含量也有少量的增加.同时,再悬浮作用对沉积物-水界面三态氮和可溶磷的环境地球化学行为也有一定的影响,与静置状态相比,NH₄⁺-N和NO₃^--N表现出与静置状态截然相反的变化规律,NO₂^--N受多种因素的影响,变化比较复杂,初期与静置状态相反而后表现一致.再悬浮颗粒物浓度也是制约沉积物-水界面三态氮和可溶磷变化的主要因子之一.实验结果显示,NH₄⁺-N在前7h以内的变化和悬浮颗粒物浓度表现出较好的相关关系,后5h呈负相关关系;NO₂^--N和可溶磷在整个过程中与悬浮颗粒物浓度的变化都有着很好的相关性,只有NO₃^--N的变化与其关系比较薄弱.     

改造滤岸对城市降雨径流中氮磷去除的中试研究

选择煤渣、锯末、沸石、麦饭石、土壤和马尼拉草构建了城市河岸带改造滤岸中试模型,并对其去除城市降雨径流中氮磷污染物能力进行了研究.结果表明,改造滤岸对表面径流和下渗径流中NH4+-N和TP具有良好的净化效果和较强的去除能力;NH4+-N平均去除率分别为66.5％和83.7％,TP平均去除率分别为42.6％和96.2％,出水水质分别可达国家地表水Ⅳ类和Ⅲ类水标准,模型稳定后对表层径流和下渗径流中TN的去除率可达20％左右;模型对NH4+-N、TN和TP的处理负荷分别为634.1～1114.5 mg-m-2·h-1、102.2 ～594.2mg· m-2·h-1和20.6～ 209.0 mg·m-2· h-1,表面径流大于下渗径流.模型内碳源(锯末)以及其他介质的添加虽然能够提高氮的转化能力,但也会影响模型对TN的去除率;下凹断面和末端断面对氮磷的去除率和去除负荷间存在一定的差异,但随着模型的稳定其差异逐渐降低.模型对氮磷的处理负荷与入水氮磷浓度呈显著正相关,说明模型具有一定的抗冲击能力.     

长江口北支潮滩沉积物-水界面无机氮的交换通量及季节变化

对长江口北支地区沉积物--水界面无机氮的交换通量及季节变化进行了研究。由于沉积物--水界面无机氮的交换行为受到不同环境因子的影响，随着季节更替，氮的界面交换行为有较大的差异。一方面，滨岸地区的沉积物对水体中的氮有着良好的去除能力，是水体中硝氮、氨氮的汇；另一方面，由于河口滨岸生态系统是一个脆弱的并且处于动态变化的系统，随着外界条件的变化，河口沉积物--水界面的物质交换会受到很大的影响，有可能从营养盐的汇转化为营养盐的源，对水体造成二次污染。研究揭示：生物活动、温度、溶解氧等环境因子在沉积物--水界面氮的季节交换行为中作用明显，而盐度、Eh等因子的作用是次要的。     

Toxic heavy metal contamination and risk assessment of street dust in small towns of Shanghai suburban area, China

The aims of this paper were to quantify the heavy metal concentrations in street dust of small towns in Shanghai suburban area compared with those in urban area, and examine their seasonal and spatial variations, and to assess their risks to water environment and local populations. Street dust samples were collected from three small towns and urban area in Shanghai in different seasons. Levels of heavy metals were determined by atomic adsorption spectrophotometer analyzer. The method of potential ecological risk index and the health risk assessment model were used to evaluate the potential risks to water bodies and local residents, respectively. The mean metal concentrations in street dust of small towns were far above soil background values but still lower than those in the urban area. No significant seasonal change was observed except for Cr, Ni, and Zn concentrations. Higher metal concentrations tended to be located in central area of towns and township roads. The integrated metal contamination was high and posed a strong potential ecological risk. Children had greater health risk than adults. The carcinogenic risk probabilities were under the acceptable level. The hazard index values to children were close to the safe level. Street dust from the studied area has been contaminated by heavy metals. The contamination of these elements is related more to the pollution source than seasonal change. The combination of the six metals may threaten the water environment and has non-cancer health risk to children, but not to adults.     

Metal release/accumulation during the decomposition of Potamogeton crispus in a shallow macrophytic lake

Changes in metal concentrations in the litter of Potamogeton crispus were monitored during a consecutive 40-day in situ decomposition experiment using the litterbag method.The accumulation index was calculated and used to indicate the changes in the metals in litter.The results showed that the concentrations of Al,Cd,Cr,Fe,Mn,and Pb in litter increased significantly during the decomposition,while Cu and Zn concentrations decreased dramatically.Significant positive correlations were found between the concentrations of Al,Cr,Fe,and Mn and between Cu and Zn.Moreover,Cu and Zn both negatively correlated with Al and Fe.The remaining dry mass was negatively correlated with Al and Fe concentrations but positively correlated with Cu and Zn concentrations.Generally the accumulation index values of metals other than Al were less than one,indicating that the litter of P.crispus acted as a source of metals to the surrounding water body.Al was the only metal that showed continuous net accumulation in litter.The net accumulation of Fe and Mn in litter during the last 10 days of the experiment may indicate the precipitation of Feand Mn-oxides.It was estimated that 160 g/m~2(dry weight)P.crispus was decomposed in40 days.This was equivalent to releasing the following amounts of metals:0.01 mg Cd,0.03 mg Cr,0.71 mg Cu,0.55 mg Mn,0.02 mg Pb and 13.8 mg Zn into surrounding water,and accumulating 149 mg Al and 11 mg Fe,in a 1 m~2 area.     

东平湖菹草腐烂分解及其对水环境的影响

于2011年6月-7月在现场采用网袋法研究了东平湖沉水植物菹草的分解失重和营养元素的变化动态.结果表明,菹草在0～14d腐烂分解较快,40 d可分解约80％的生物量,年残留率为5.0％,与一次指数模型相比,二次指数模型Wt/W0 =0.785e-0.386t +0.215e-0.004t(R2=0.876)能更好的描述菹草分解失重动态.菹草残留物中各营养元素的损失与干重衰减不同步,C、N、S含量在1～20 d内表现为上升,20～30 d显著下降,30～40 d略有增加但变化较小;P含量在1～6 d显著下降,随后呈缓慢上升趋势.菹草各营养元素的累积释放率变化规律基本一致,均在14 d和25 d达到峰值,在腐烂初期(0～8d)表现为P＞S＞C＞N,8d后(10～40 d)表现为P＞C＞S＞N.各营养元素的释放主要集中在菹草腐烂分解的前期(0～ 14 d),初步估算东平湖内该期间C、N、S、P的释放量约为12510 t、1187 t、147 t和235 t,相当于水中C、N、S、P分别增加约29.9、2.84、0.35、0.56 mg·L-1,易造成水体的“二次污染”.东平湖菹草年残留量约为2090t(干重),约占东平湖沉积通量的0.6％,对湖泊的填平作用较小.     

聊城市城区河湖水中Hg、As浓度分布特征及健康风险评价

为了解聊城市城区河湖水中Hg、As浓度分布,于2010年12月19日采集、分析了20个表层水样中Hg、As浓度,并采用美国环境保护署推荐的健康风险评价模型对其进行了初步评价.结果表明:城区河湖水中Hg、As的质量浓度分别为0.016～0.366、0.494～23.438 μg/L,各主要河湖水中Hg的平均浓度大小为周公河＞东昌湖＞小运河＞徒骇河;As的平均浓度大小为周公河＞徒骇河＞小运河＞东昌湖;东昌湖Hg浓度超过《地表水环境质量标准》(GB 3838-2002)的Ⅲ类水标准值,超标率为71.4％.各主要河湖水中Hg、As浓度的空间分布差异显著,Hg主要来源于大气沉降和沿岸生活污水的排放,As主要来源于工业废水,两者均受到上游来水的影响.As通过饮水途径产生的健康风险值在10-6～10-4 a-1,是Hg的103～106倍,高于部分机构推荐的最大可接受风险水平(1.0×10-6 a-1).建议有关部门应加强对聊城市城区河湖水中Hg、As的监测和环境风险管理.     

A comprehensive investigation and assessment of mercury in intertidal sediment in continental coast of Shanghai

The aims of this paper were to survey the total Hg levels and distribution character in intertidal sediment in continental coast of Shanghai, and identify the environment factors that might influence the sediment Hg concentrations, and to assess the pollution degree and potential ecological risk of Hg in sediment. Eighty-eight surface sediment samples and 18 sediment cores were collected for Hg contamination analysis. Physicochemical properties including Eh, particle size, content of total organic carbon (TOC), and acid volatile sulfide (AVS) were also measured. Index of geo-accumulation (I _geo) and potential ecological risk index were used respectively to assess the pollution levels and the ecological risk of sediment Hg. The average of total Hg concentrations in surface sediments was 107.4?±?90.9 ng/g with the range from 0 to 465.9 ng/g. Higher Hg concentrations were generally found in surface sediments near sewage outfalls and the mouth of rivers. Total Hg concentrations were significantly correlated with TOC (p?<?0.05) both in surface (r?=?0.24) and core (r?=?0.29) sediments, but not with the other environment factors (Eh, AVS, and particle size). Geo-accumulation index indicated that Hg contamination in intertidal sediments was generally at none to moderate degree, while potential ecological risk index demonstrated that the risk caused by Hg were at moderate to considerable level. Intertidal sediment in continental coast of Shanghai has generally been contaminated by Hg, and it might pose moderate to considerable risk to the local ecosystem. The Hg contamination is related more to the coastal pollution sources and complicated hydrodynamic and sedimentary conditions than the other environment factors studied.