北京市近郊区土壤砷累积特征

城市近郊区土地利用类型多元化,同时也承载着巨大环境压力,研究近郊区土壤污染特征对城市规划及发展有着重要意义.通过3 km×3 km网格布点,系统采样调查了北京市近郊区5～6环路之间167个样点的0～20 cm表层土壤样品中砷的含量,分析了城市近郊区土壤砷的累积特征.结果表明,北京市近郊区土壤砷含量为2.89～11.38 mg.kg-1,平均值为7.11mg.kg-1.平均值在90年代末的背景值调查数据的范围之内,但是各个分位数级别的值均小于80年代初的北京市土壤背景值调查数据.因子分析结果发现北京市近郊区土壤砷与来源于成土母质的Co、Mn和Ni元素一组.克里格插值得到的北京市近郊区土壤砷含量空间分布图表明,西北与东部及东南部分土壤砷含量较东北和西南部高,砷含量最高25%的土壤样点与点源污染有关,而砷含量最低25%的样点大多远离污染源.不同土地利用类型土壤砷的比较结果表明人类活动在一定程度上影响土壤中砷的累积,生活区与农田土壤砷含量相似且显著大于绿地和荒地.污染源对生活区和绿地与荒地土壤中砷的累积有显著影响,工厂区附近的土壤砷含量显著比远离工厂区和交通区的土壤高.因此,北京市近郊区土壤砷在整体空间分布上主要与成土母质有关,然而人类活动在一定程度上也显著增加了土壤砷的累积.     

Vulcan_(42)消解—原子荧光测定土壤和沉积物中的砷汞

建立了全自动样品处理系统Vulcan 42-原子荧光光度法测定土壤和沉积物中砷和汞的方法。准确称取0.2500 g样品,经Vulcan42全自动消解系统消解后,采用原子荧光光度计测定砷和汞的含量。运用该方法砷的检出限为0.11 mg/kg,回收率在96%¹01%之间,相对标准偏差(n=6)在1.3%101%之间,相对标准偏差(n=6)在1.3%⁴.5%之间;汞的检出限为0.003 mg/kg,回收率在90%4.5%之间;汞的检出限为0.003 mg/kg,回收率在90%¹08%之间,相对标准偏差(n=6)在0.5%108%之间,相对标准偏差(n=6)在0.5%⁴.7%之间。     

电动力学修复铜污染土壤的研究

采用电动力学方法修复重金属污染土壤。研究中采用高岭土模拟铜污染土壤,电化学装置的电压强度为0.5 V/cm,通过在阴阳极室加入不同的缓冲液来确定铜的迁移效果。结果表明在阴极室加入乙酸作为缓冲液可以有效提高铜的迁移效果,在阳极加入柠檬酸能够有效的与铜形成络合物达到更好的迁移效果。     

原子荧光光谱仪测定底泥中砷含量的不确定度评定

介绍了原子荧光光谱仪测定底泥中砷含量的不确定度评定方法,分析和识别测量过程中不确定度的来源,较为全面地评定了测量不确定度。根据最小二乘法拟合计算工作曲线的标准不确定度,采用极差法评定测量次数较少时引起的标准不确定度。     

Soil fertility dynamics in runoff-capture agriculture, Canary Islands, Spain

In the extremely arid (∼150 mm yr⁻¹) eastern Canary Islands of Lanzarote, Fuerteventura and La Graciosa, agriculture has been sustained for decades by a traditional runoff-capture (RC) farming system known as “gavias”. Although the main goal of these systems is to increase water supply for crops, making unnecessary conventional irrigation, a secondary and equally important factor is that this system allows for sustainable agricultural production without addition of chemical or organic fertilizers. A field study was conducted to assess the impact of long-term agriculture (>50 yr) on soil fertility and to evaluate key factors affecting the nutrient sustainability of RC agricultural production. Soil fertility and nutrient dynamics were studied through chemical characterization of the arable layer (0-25 cm) of RC agricultural plots, adjacent natural soils (control) not affected by runoff and cultivation, and sediments contributed by a series of RC events. Results showed that RC soils have enhanced fertility status, particularly because they are less affected by salinity and sodicity (mean electrical conductivity = 1.8 dS m⁻¹ vs. 51.0 dS m⁻¹ in control soils; mean exchangeable sodium percentage = 11.1% vs. 30.6% in control soils), and have higher water and nutrient holding capacities (mean clay plus silt contents ≈87% vs. 69% in control soils). In general, sediments transported with the runoff and deposited in RC plots (average sediment yield ≈ 46 ton ha⁻¹ yr⁻¹), contain sufficient nutrients to prevent a progressive reduction of essential plant nutrients below natural levels in spite of nutrient uptake and removal by the harvested crop. Average additions of nitrogen, phosphorus and potassium with the runoff sediments were 33.6, 35.3 and 48.8 kg ha⁻¹ yr⁻¹, respectively. Results of this study show how a crop production system can be sustained in the long term by natural hydrological and biogeochemical catchment processes. This system maintains a nutrient balance that is not based on energy-intensive inputs of fertilizers, but is integrated in natural nutrient cycling processes, unlike other tropical farming agroecosystems.     

Impact analysis of drought, water excess and salinity on grass production in The Netherlands using historical and future climate data

The coupled SWAP-WOFOST model was used to study the effects of increasing salinity of groundwater, drought and water excess on grass production in The Netherlands. WOFOST simulates crop growth and SWAP simulates transport of water, solutes and heat in the vadose zone. The model was tested using several datasets from field experiments. We applied the models at regional scale where we quantified the impact of various groundwater salinity levels on grass growth and production using historical weather data (1971-2000). The salt concentrations in the subsoil were derived from the National Hydrological Instrument. The results show that salinity effects on grass production are limited. In wet years the excess rainfall will infiltrate the soil and reduce salt water seepage. In a next step we used future weather data for the year 2050, derived from 3 Global Circulation Models. From each model we used data from two CO₂ emission scenarios. As expected higher temperatures increased drought stress, however, the production reduction as a result of salt water in the root zone is limited. Salt stress mainly occurred when irrigation was applied with saline water. The increased CO₂ concentration in combination with the limited drought stress resulted in increasing simulated actual and potential yields. Overall conclusion for grassland in The Netherlands: drought stress is stronger than stress caused by water excess which on its turn is stronger than salinity stress. Future water demand for irrigation may increase by 11-19% and result in water scarcity if water supply is insufficient.     

南方红壤丘陵区粮食生产的完全成本 ——以湖南省祁阳县为例

针对目前我国农业生产中的资源环境问题,指出粮食生产成本核算的不完整性,粮食生产造成的资源耗减和环境降级得不到补偿。运用环境经济学原理和可持续发展理论对粮食生产的完全成本进行分析,提出粮食生产的完全成本除包括直接生产成本外,还应包括粮食生产的资源环境成本。论文以南方红壤丘陵区的湖南省祁阳县为研究对象进行案例分析,研究表明,2008年该区域粮食生产的资源环境成本相当于当年农业总产值的36.55%;早、中、晚稻的完全成本分别达到4.27、3.84和4.40元·kg^-1,其中资源环境成本分别为1.38、 1.65和1.64元·kg^-1,直接生产成本分别为2.89、 2.19和2.76元·kg^-1,而实际市场价格分别仅有1.76、 1.90和1.84元·kg^-1。研究结果对有关部门制定相关农业政策、调整粮食生产布局、促进区域粮食生产和可持续发展具有一定的参考价值。     

吸附剂烟气脱砷的研究现状

大气砷污染问题日益引起人们的重视,吸附剂能够在去除烟气中砷的同时去除其他有害气体,是控制烟气砷含量、防止砷污染的有效途径.文章分析了砷在废气中的形态及分布,总结了近年来氧化钙、活性炭、飞灰和金属氧化物作为吸附剂用于烟气脱砷的最新研究进展,重点分析了各自的吸附机理及不同因素对脱砷过程的影响.指出吸附过程通常以化学吸附为主...     

Arsenic removal from groundwater by acclimated sludge under autohydrogenotrophic conditions

Arsenic in the environment is attracting increasing attention due to its chronic health effects. Although arsenite(As(III)) is generally more mobile and more toxic than arsenate(As(V)), reducing As(V) to As(III) may still be a means for decontamination, because As(III) can be removed from solution by precipitation with sulfide or by adsorption or complexation with other metal sulfides. The performance of As(V) bio-reduction under autohydrogenotrophic conditions was investigated with batch experiments. The results showed that As(V) reduction was a biochemical process while both acclimated sludge and hydrogen were essential. Most of the reduced arsenic remained in a soluble form, although 20% was removed with no addition of sulfate, while 82% was removed when sulfate was reduced to sulfide. The results demonstrated that the reduced arsenic was re-sequestered in the precipitates, probably as arsenic sulfides. Kinetic analysis showed that pseudo first-order kinetics described the bio-reduction process better than pseudo second-order. In particular, the influences of pH and temperature on As(V) reduction by acclimated sludge under autohydrogenotrophic conditions and total soluble As removal were examined. The reduction process was highly sensitive to both pH and temperature, with the optimum ranges of pH 6.5–7.0 and 30–40°C respectively. Furthermore, Arrhenius modeling results for the temperature effect indicated that the As(V) reduction trend was systematic. Total soluble As removal was consistent with the trend of As(V) reduction.     

Community structure and elevational diversity patterns of soil Acidobacteria

Acidobacteria is one of the most dominant and abundant phyla in soil,and was believed to have a wide range of metabolic and genetic functions. Relatively little is known about its community structure and elevational diversity patterns. We selected four elevation gradients from 1000 to 2800 m with typical vegetation types of the northern slope of Shennongjia Mountain in central China. The vegetation types were evergreen broadleaved forest,deciduous broadleaved forest,coniferous forest and sub-alpine shrubs. We analyzed the soil acidobacterial community composition,elevational patterns and the relationship between Acidobacteria subdivisions and soil enzyme activities by using the 16 S rRNA meta-sequencing technique and multivariate statistical analysis. The result found that 19 known subdivisions as well as an unclassified phylotype were presented in these forest sites,and Subdivision 6 has the highest number of detectable operational taxonomic units(OTUs). A significant single peak distribution pattern(P 0.05) between the OTU number and the elevation was observed. The Jaccard and Bray–Curtis index analysis showed that the soil Acidobacteria compositional similarity significantly decreased(P 0.01) with the increase in elevation distance. Mantel test analysis showed the most of the soil Acidobacteria subdivisions had the significant relationship(P 0.01) with different soil enzymes. Therefore,soil Acidobacteria may be involved in different ecosystem functions in global elemental cycles. Partial Mantel tests and CCA analysis showed that soil pH,soil temperature and plant diversity may be the key factors in shaping the soil Acidobacterial community structure.