Immobilization of cadmium in simulated contaminated soils using thermal-activated serpentine

ABSTRACT

The thermal-activated serpentine prepared by heating natural serpentine at different temperatures was used to immobilize cadmium (Cd) in simulated contaminated soils. The results showed that the increasing soil pH induced by adding serpentine was primarily responsible for reducing the content of TCLP-Cd (toxicity characteristic leaching procedure-Cd) in soil. Furthermore, adding thermal-activated serpentine could promote the transformation from exchangeable form of Cd in soil to low bioavailable Cd (Fe-Mn oxides, carbonate, and residual form) by surface adsorption and surface precipitation, and then reduced the bioavailability of Cd in soil. Under the same treatment condition, adding S700 (serpentine activated at 700°C) exhibited better performance to immobilization of Cd, and it could reduce exchangeable Cd by 23.76~36.49%, and increase carbonate, Fe-Mn oxide, and residual form of Cd by 6.03~8.03%, 6.05~8.35%, and 11.17~19.58%, respectively. These results indicated that thermal-activated serpentine would be the great potential for immobilization of Cd in soil.     

小麦的水分利用效率及其最优化问题

根据田间实测资料分析了小麦水分利用效率的综合指数－Ｐ／Ｅ。水分利用效率的变化是光合和蒸腾综合作用的结果。影响这种变化的主要因子为光照，相对湿度，气孔传导率以及土壤的肥力状况等．。分析表明，作物的“午休”现象是农作物实现水分利用最优的一种适应性调节。     

菌根接种对柑桔磷素营养和生长效应的研究

许多研究证明菌根能显著地促进柑桔生长.Menge等(1975)报道接种Glomus fasciculatus于不同柑桔品种实生苗后,其植株生长量比无菌根的增加120—2600%.目前,美国、澳大利亚和南非等国以菌根真菌作为一种“生物肥料”,正研究菌根接种剂的商业生产,企图应用于柑桔果园,来提高肥效和减少施肥量.     

旱作农业综合配套技术及增产效益研究

宁夏南部半干旱水土流失地区,在作物合理布局的基础上,建立以粮——豆——草轮作为中心的综合配套技术体系,做到轮作制度化、栽培规范化,施肥模式化。系统内的能量转化效益提高14.7%,粮食单产和总产分别较实验前提高1.2倍和1倍。其中“轮作中心的平衡施肥”,既考虑到氮、磷等主要营养元素的协调平衡,也考虑到周期性的供求平衡,提高了系统内土壤养分的调控能力和稳定性。     

冀北高原草甸栗钙土春小麦中化肥氮去向的研究

在冀北高原张北县的草甸栗钙土上，采用＾１５Ｎ质量平衡法和微气象学技术，对春小麦中氮肥的去向，以及氨挥发进行了田间原位观测。试验中的氮肥用量为Ｎ４．８３ｋｇ／亩，１／３作基肥、２／３作追肥。基肥随播种施入，追肥于拔节期撤施，随即灌水。结果表明，小麦回收、土壤残留和损失的肥料氮各占施入氮量的３７．８％－４８．３％、３３．８％－４０．４％和１４．３％－２５．４％。其中，尿素作基肥与作追肥的处理之间，其氮     

Geochemistry of HCO3- at the Sediment-Water Interface of Lakes from the Southwestern Chinese Plateau

Sediments were cored, and the sediment-water interface and overlying waters were sampled in 5 lakes from the southwestern Chinese plateau during 1991-95. The geochemistry of HCO3- at the sediment-water interface was examined by studying detailed profiles of pH, HCO3- concentrations and δ13C of dissolved inorganic carbon (DIC) in overlying lake water and porewater near the sediment-water interface. Dissolution-precipitation equilibrium of carbonates, diffusion flux, and the extent of the influence of diffusion on the whole lake were calculated. The results show that the HCO3- near the interface carried isotopic characteristics of decomposition of organic matter during early diagenesis, and that the porewater in surface sediments was unsaturated relative to calcite, and gradually saturated with depth. Furthermore, the interface is a source of HCO3- to the overlying water. Alkalinity (Alk) diffusion flux from sediments to the overlying water due to concentration gradients ranged from 0.51 to 24.33 × 10-4 mol cm-2 a-1. The calculated contribution of the diffusion of Alk to the overlying water ranged from 0.46% to 49.42%. Diffusion is an important source of Alk in lakes with a long residence time and a relatively shallow depth.     

宁夏银南灌区排水现状分析及计算

作为灌溉农业的一项保障措施，农田排水在维持田间水盐平衡的同时，也向下游输送了大量可能成为地表水污染源的物质。位于黄河上游的宁夏银南灌区由于历史原因形成的“大引大排”积习，每年将过量的农田排水排入黄河，成为下游水质污染源，同时也浪费了宝贵的水资源。该文针对宁夏银南灌区过量排水问题，对灌区排水现状进行了详细的分析和计算。结果表明，在现有灌排制度下，生长期内水田的农沟排水量约56 cm，占地下排水总量的58%；旱田的农沟排水量较少，只有1.0 cm，占地下排水总量的4%。建议在水田农沟上加筑控制性建筑物，如堰等，对排水量进行控制，达到节约灌溉用水和减少农田排水对下游河道污染的目的。     

钾肥用量和品种对桑叶生产及蚕茧质量的影响

通过为期 4年的田间施肥试验和 1季养蚕试验 ,研究了钾肥用量和钾肥品种对桑叶产量、品质、养分吸收和蚕茧质量的影响。结果表明 ,施K2 O 1 5 0、30 0、375kghm-2 a-1 处理分别比不施K肥年均增产桑叶 2 3.9%、31 .7%、36 .0 %;等量钾肥时 ,KCl对桑叶增产效果基本等同于K2 SO4;施钾增产效果有逐年增加趋势 ,同时钾肥施用表现后效。施钾明显提高桑叶中N、K和S(K2 SO4为钾源时 )含量 ,而降低Ca、Mg和Zn含量 ,对P含量影响不大。结果显示 ,钾肥施用大幅度促进了桑树对各种养分的吸收 ,从而提高了肥料利用率。施钾明显促进桑叶品质的改善 ,随着钾肥用量增加 ,桑叶中必需氨基酸、氨基酸总量、蛋白质、糖分和油脂含量均呈增加趋势。KCl施用也能提高桑叶品质 ,但效果比K2 SO4差。蚕茧质量测试结果表明 ,桑树施钾后对喂养的蚕茧品质产生正面影响 ,蚕重、全茧量、上茧率、茧丝长、解舒率、茧丝净度等指标均因施钾而提高 ,高量钾比低量钾效果好 ,在等量钾用量时K2 SO4对蚕茧质量的促进作用明显好于KCl。     

我国储粮技术创新途径与发展思路

本文根据中国国情和基层实际，从三低储粮，机械通风、粮仓熏蒸，防护剂和消毒剂等四个方面，系统地提出了17项技术创新途径和设想，并对今后储粮实用技术发展方向提出了新的思路。