Water incubation-induced fluctuating release of heavy metals in two smelter-contaminated soils

The soil moisture regime can affect the release of heavy metals in soil. In the previous studies, slightly polluted soils or artificially contaminated soil samples were considered to investigate the effect of soil moisture. We used highly smelter-contaminated and aged soils to study the release of typical heavy metals(Cu, Zn, Cd and Pb) induced by water incubation in batch experiments with characterization via speciation and X-ray diffraction analyses(XRD). The results show that the leachable concentrations of the heavy metals increased slightly in the first 30 days, decreased drastically between 30 and 90 days, and immobilized relatively constant thereafter. The fluctuation was ascribed to the changes of soil Eh and pH, the reductive dissolution of crystalline iron oxides, the formation of new amorphous iron oxides, the absorption of dissolved organic matter and the precipitation of metal sulfide. Speciation analysis indicated that a proportion of the soil heavy metals was transformed from an exchangeable fraction to a less labile fraction after water incubation. And the presence of a lead iron oxide phase and the peak increasing of zinc sulfide were observed via XRD analyses. Finally, water incubation restrained the release of heavy metals after 180 days of incubation, and reduced the leachability of Cu, Zn, Cd and Pb by as much as 1.61%–7.21% for soil A and 0.43%–3.36% for soil B, respectively. The study findings have implications for the formulation of risk control and management strategies for heavy metals in smelter-contaminated soils.     

武汉市无公害蔬菜生产的问题与对策

介绍了我国部分城镇在粮食作物和蔬菜产品受化学农药等有害化学物污染简况和无公害蔬菜的研究进展。调查分析了武汉市目前蔬菜生产中农药污染的现状与问题，提出了在武汉市实施无公害蔬菜生产示范工程项目的建议和对策，并进行了讨论。     

我国东部沿海地区差距状况以及经济低谷地区的崛起

我国是区域发展差异巨大的大国之一，存在着多种尺度的区域发展差异。从中小尺工区域差异的角度，分析了我国东部沿海地区内部发展差距扩大趋势有其影响，可以看出，东部沿海地区在经济快速发展的同时，也存在着经济相对落后的低谷地区。沿海经济低谷地区分布相对集中于香港－－珠江三角洲、上海－长江三角洲、京津唐－环渤海三个经济隆起带之间，处于省际交界处。按照类型可以分为黄泛平原区、丘陵山区和沿海库区。东部经济低谷地区区位条件相对比较落后，交通可达性较差，产业结构单一，城市化水平发展严重滞后，社会经济发展比较缓慢，这些不利因素制约着该地区经济和社会的发展。根据崛起机制和途径，低谷地区发展呵以分为资源转换型、非国有经济推动型和外资推动型。建议国家修筑贯穿沿海经济低谷地区的东部沿海铁路大通道，降低沿海经济低谷地区设定标准，加快农业产业化发展，对特殊贫困地区实行特殊优惠政策，从而促进东部沿海地区经济协调发展。     

长江上游攀西—六盘水地区资源开发与环境保护

长江上游攀西——六盘水地区是个资源富集的“金三角”。通过交通先行,加快资源开发,对增强21世纪经济发展后劲意义重大。但生态环境恶化,急需加强保护。     

雷州半岛与海南岛砖红壤养分比较研究

雷州半岛与海南岛砖红壤养分比较研究罗凯（广东省徐闻县农村工作委员会，徐闻５２４１００）ＣｏｍｐａｒｉｓｏｎｏｆＮｕｔｒｉｅｎｔｓＣｏｎｔｅｎｔｏｆＬａｔｏｓｏｌｓｉｎＬｅｉｚｈｏｕＰｅｎｉｎｓｕｌａａｎｄＨａｉｎａｎＩｓｌａｎｄ￥ＬｕｏＫａｉ（Ｒｕｒ...     

耕地不同产量水平的面积与分布监测法

查清中低产田的面积、分布与开发条件是制定农业综台开发规划的重要依据。采用按公里网布设的农业资源动态监测系统,开展对耕地不同产量水平的面积与分布的动态监测,其方法具有准确、简便和实用的特点。     

润滑油基础油在储运过程中可能产生的危害和对策

分析了润滑油基础油在储运过程中,油品质量可能产生的不良变化和对周围环境造成的危害.针对这些危害提出了解决的对策.     

Elevated CO2 stimulates net accumulations of carbon and nitrogen in land ecosystems: a meta-analysis

The capability of terrestrial ecosystems to sequester carbon (C) plays a critical role in regulating future climatic change yet depends on nitrogen (N) availability. To predict long-term ecosystem C storage, it is essential to examine whether soil N becomes progressively limiting as C and N are sequestered in long-lived plant biomass and soil organic matter. A critical parameter to indicate the long-term progressive N limitation (PNL) is net change in ecosystem N content in association with C accumulation in plant and soil pools under elevated CO2. We compiled data from 104 published papers that study C and N dynamics at ambient and elevated CO2. The compiled database contains C contents, N contents, and C:N ratio in various plant and soil pools, and root:shoot ratio. Averaged C and N pool sizes in plant and soil all significantly increase at elevated CO2 in comparison to those at ambient CO2, ranging from a 5% increase in shoot N content to a 32% increase in root C content. The C and N contents in litter pools are consistently higher in elevated than ambient CO2 among all the surveyed studies whereas C and N contents in the other pools increase in some studies and decrease in other studies. The high variability in CO2-induced changes in C and N pool sizes results from diverse responses of various C and N processes to elevated CO2. Averaged C:N ratios are higher by 3% in litter and soil pools and 11% in root and shoot pools at elevated relative to ambient CO2. Elevated CO2 slightly increases root:shoot ratio. The net N accumulation in plant and soil pools at least helps prevent complete down-regulation of, and likely supports, long-term CO2 stimulation of C sequestration. The concomitant C and N accumulations in response to rising atmospheric CO2 may reflect intrinsic nature of ecosystem development as revealed before by studies of succession over hundreds to millions of years.     

Accumulation and phytoavailability of benzo[a]pyrene in an acid sandy soil

Effects of benzo[a]pyrene (B[a]P) on ryegrass (Lolium perenne L.) growth, plant accumulation and dissipiation of B[a]P in a red sandy soil (Hapli-Udic Argosol) were studied in a pot experiment. The plants were grown for 61 days in soil spiked with B[a]P at 0, 12.5, 25 and 50 mg kg⁻¹. Control pots without plants were also set up. Soil extractable B[a]P, plant shoot and root biomass, and concentrations of B[a]P in plant shoots and roots were determined. Ryegrass biomass was increased by addition of B[a]P and root B[a]P concentrations were significantly correlated with B[a]P application rate, but no such correlation was found for shoot B[a]P concentrations. This indicates that B[a]P enhanced the growth of the ryegrass. The extractable B[a]P concentration in the planted soil was significantly lower than that in the unplanted control soil at the rate of 50 mg B[a]P kg⁻¹. This indicates that ryegrass may help to dissipate B[a]P in soil at concentrations over 50 mg kg⁻¹ soil although the mechanism for this is not understood.     

TiO2/SiO2催化剂光催化降解罗丹明B的表观动力学

采用多孔硅胶为载体的TiO₂/SiO₂光催化剂,建立了三相内循环流化床光催化氧化体系,并以罗丹明B染料为典型污染物,研究其降解规律.通过对罗丹明B降解过程的表观动力学研究,发现在该体系中罗丹明B的降解并不符合Langmuir-Hinshelwood反应动力学模型.实验表明,其降解反应动力学符合双曲型模式,即降解率的倒数1/X和时间的倒数1/t成线性关系.反应速率常数与反应物初始浓度无关,与光源强度和相对体积能量吸收速率成正比.将不同实验条件下的罗丹明B的降解率实测值与模型计算值相比较,二者能很好吻合,平均相对偏差仅为3.25%.