Spatial distribution and potential ecologic risk assessment of heavy metals in the sediments of the Nansi Lake in China

The contamination levels and ecological risks of heavy metals in the sediments of the Nansi Lake were investigated. The contents of Cd, Cr, Cu, Pb, Zn, Ni, and Co in the surface sediments collected at 20 sites ranged from 0.08 to 1.12, 58.92 to 135.62, 38.09 to 78.65, 24.51 to 53.95, 110.51 to 235.36, 11.30 to 65.40, and 4.12 to 20.14 mg/kg, respectively. The results of partitioning analysis revealed that the proportions of soluble and exchangeable fraction were less than 1 %, the proportions of carbonate, amorphous oxides, organic matter, and crystalline oxides fraction were less than 10 %, and 10.52 % of Cd was associated with carbonate. The average proportions in the residual fraction ranged from 48.62 % for Cu to 73.76 % for Ni, indicating low mobility and bioavailability. The geoaccumulation index (I _geo), relative enrichment factor (REF), sediment pollution index (SPI), and potential effect concentration quotient (PECQ) values of the heavy metals in the sediments were not in agreement with each another. The average REF values of Cd and Zn were higher than those of other metals. However, the average PECQ values were higher for Cr and Ni than those of other metals, indicating that these two metals would cause higher adverse biological effects. Therefore, it is suggested that future management and pollution control might focus on Cd, Zn, Cr, and Ni in the sediments of the Nansi Lake.     

Impact of land use and land cover changes on ecosystem services in Menglun, Xishuangbanna, Southwest China

Changing the landscape has serious environmental impacts affecting the ecosystem services, particularly in the tropics. In this paper, we report changes in ecosystem services in relation to land use and land cover over an 18-year period (1988--2006) in the Menglun Township, Xishuangbanna, Southwest China. We used Landsat TM/ETM and Quickbird data sets to estimate changes in ten land use and land cover categories, and generalized value coefficients to estimate changes in the ecosystem services provided by each land category. The results showed that over the 18-year period, the land use and land cover in the study area experienced significant changes. Rubber plantations increased from 12.10% of total land cover to 45.63%, while forested area and swidden field decreased from 48.73 and 13.14 to 27.57 and 0.46%, respectively. During this period, the estimated value of ecosystem services dropped by US $11.427 million (approximately 27.73%). Further analysis showed that there were significant changes in ecological functions such as nutrient cycling, erosion control, climate regulation and water treatment as well as recreation; the obvious increase in the ecological function is provision of raw material (natural rubber). Our findings conclude that an abrupt shift in land use from ecologically important tropical forests and traditionally managed swidden fields to large-scale rubber plantations result in a great loss of ecosystem services in this area. Further, the study suggests that provision of alternative economic opportunities would help in maintaining ecosystem services and for an appropriate compensation mechanisms need to be established based on rigorous valuation.     

Dissipation and residue of MCPA (4-chloro-2-ethylphenoxyacetate) in wheat and soil

A rapid and simple HPLC method has been developed for the quantitation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in both wheat and soil samples. Samples were extracted in acidic media and cleaned up by solid-phase extraction with C(18) cartridges before HPLC-DAD detection. The limits of detection and quantification of MCPA were 0.02 ng and 0.01 mg/kg for both wheat and soil. The mean recoveries ranged from 87.1% to 98.2%, and the RSDs ranged from 0.604% to 3.44% for the three spiked levels (0.01, 0.1, 0.5 mg/kg). The proposed method was successfully applied to the analysis of MCPA residues in wheat and soil samples from an experimental field. The dissipation half-lives in soil were calculated to be 3.22 days (Beijing) and 3.10 days (Tianjin), respectively. Direct confirmation of the analytes in real samples was achieved by gas chromatography-mass spectrometry. The results indicated that at harvest time, the residues of MCPA in wheat were well below the maximum residue levels and were safe to apply in wheat.     

The emergy analysis of loop circuit

Emergy analysis can analyze the resource utilization and environmental performance of a system. Loop circuit is a common structure in the process industry, but when emergy analysis is carried out to such structure, mistakes such as emergy double counting often occur. To avoid emergy double counting, two types of loop circuit-direct loop circuit and indirect loop circuit-are theoretically distinguished, and the methods to avoid such mistake are proposed. Finally, PVC production and vinyl acetate production are adopted to demonstrate the methods.     

神经节苷脂生产废水处理技术研究

针对神经节苷脂生产废水蛋白质含量高的特点,研究了等电点沉淀或混凝沉降预处理、厌氧好氧生物处理、化学沉淀和类Fenton氧化后处理组合工艺处理神经节苷脂生产废水的技术。结果表明,神经节苷脂生产废水的等电点在pH=2.2左右,通过等电点沉淀可去除30%以上的COD,但等电点时蛋白质的沉淀速度非常慢;用聚合硫酸铁对神经节苷脂生产废水进行混凝预处理的最适工艺条件是：pH=7～7.5,聚合硫酸铁用量＝500～750 mg/L。在优化条件下,混凝预处理可以使神经节苷脂生产废水的COD从27 000 mg/L左右降到13 000 mg/L左右。混凝预处理后的神经节苷脂生产废水经48 h厌氧和84 h好氧生物处理,COD值进一步下降到600 mg/L左右。然后向每升生化出水中加入2～3 mmol Fe³⁺,通过化学沉淀作用除去其中的磷酸盐,过量的Fe³⁺作为后续类Fenton氧化的催化剂。当H₂O₂(30％)用量为2～3 mL/L时,最终出水的COD值可以达到国家一级排放标准。     

T-S模糊神经网络在厌氧反应器预测中的应用

3个厌氧反应器运行稳定后,用三氯甲烷和2、4-二硝基酚作为毒物负荷对它们进行了冲击试验.利用负荷冲击试验所得的数据集建立了T-S模糊神经网络,并用其预测了反应器的容积产气率、挥发性脂肪酸和CH4体积含量.研究结果表明,基于某一反应器建立的T-S模糊神经网络可以很好地预测毒物负荷冲击下该反应器的容积产气率、挥发性脂肪酸和CH4变化规律,实测值与预测值的相关系数均＞0.850;但是基于某一反应器建立的模糊神经网络用来预测其他反应器时,其预测能力较差,预测值和实测值的相关系数基本上＜0.500.     

六氯苯对水体微型生物群落的影响及其吸附行为

研究了六氯苯(HCB)对微型水生生物群落的影响及其吸附、传递过程.测定了群落的耗氧量和不同粒经颗粒物的生物量及HCB变化.试验结果显示,在6μg/L HCB影响下,群落的呼吸作用受到抑制,生物量减少.试验第1天,30.0%(质量分数,下同)的HCB以溶解态存在,26.3%吸附在0.22～2 μm的颗粒物(以细菌为主)上,22.1%吸附在2～8 μm的颗粒物(以鞭毛虫和藻类为主)上,21.6%吸附在大于8 μm的颗粒物(以藻类和大型原生动物为主)上.48 h后,溶解态的HCB逐渐减少,并由食物链低营养级向高营养级传递.最后74.9%的HCB都吸附在微型生物群落等颗粒物上,只有25.1%的HCB以溶解态存在.     

水解-好氧工艺处理稠油污水

在此介绍了国内某油田采用生物膜水解酸化-生物膜接触氧化工艺处理稠油污水,并实现了3000 m3/d稠油(油密度ρ=0.86~0.97 g/L)污水达标外排的工程实例。装置运行一年来的结果表明,该工艺具有抗冲击能力强,污泥产生量少,处理效果稳定等优点,出水水质达到国家二级污水排放标准(GB8978-96),大部分水质指标达到国家一级污水排放标准。     

工业废油污染程度的熵权灰色关联模糊评价

在工业废油污染程度综合评价研究中,各类复杂油质和众多影响因素相互作用,各个理化指标间相互联系、相互干扰,因而在评价中存在一些模糊的概念和表象。采用熵权法客观赋权,灰色关联与模糊综合评价相结合的方法建立工业废油污染程度的评价排序模型。根据算例评价结果可知,该方法提供一种新的简便而快捷、适用的评价手段,为选择合适工业废油处理方式,以及工业废油的资源化和环境保护研究提供一定的理论依据。     

Chemical signature and fractionation of trace elements in fine particles from anthropogenic and natural sources

The health effects of trace metal elements in atmospheric fine particulate matter (PM_2.5) are widely recognized, however, the emission factor profiles and chemical fractionation of metal elements in different sources were poorly understand. In this study, sixteen metal elements, including Cd, Pb, V, Zn, Ba, Sb, As, Fe, Sr, Cr, Rb, Co, Mn, Cu, Ni and Sn from biomass burning, bituminite and anthracite combustion, as well as dust, were quantified. The results show different emission sources were associated with distinct emission profiles, holding important implications for source apportionment of ambient particulate metals. Specifically, Fe was the dominant metal species (28-1922 mg/kg) for all samples, and was followed by different metals for different samples. For dust, Mn (39.9 mg/kg_dust) had the second-highest emission factor, while for biomass burning, it was Cr and Ba (7.5 and 7.4 mg/kg_biomass, respectively). For bituminous coal combustion, the emission factor of Zn and Ba was 6.2 and 6.0 mg/kg_bituminous, respectively, while for anthracite combustion the corresponding emission factor was 5.6 and 4.3 mg/kg_anthracite, respectively. Moreover, chemical fractionation (i.e., the exchangeable, reducible fraction, oxidizable, and residual fraction) and the bioavailability index (BI) values of the metal elements from different sources were further investigated to reveal the link between different emission sources and the potential health risk. The findings from this study hold important implications for source apportionment and source-specific particulate metal-associated health effects.