Nitrogen Saturation of Terrestrial Ecosystems: Some Recent Findings and Their Implications for Our Conceptual Framework

The consequences of nitrogen (N) enrichment for terrestrial and freshwater ecosystems are of increasing concern in many areas due to continued or increasing high emission rates of reactive N. Within terrestrial ecosystems various conceptual frameworks and modelling approaches have been developed which have enhanced our understanding of the sequence of changes associated with increased N availability and help us predict their future impacts. Here, some recent findings are described and their implications for these conceptual frameworks and modelling approaches discussed. They are: (a) an early loss of plant species that are characteristic of low N conditions as N availability increases and a loss of species with high N retention efficiencies (so called N ‘filters’), (b) suppression of microbial immobilisation of deposited due to increased availability in the early stages of N saturation, (c) the early onset of leaching due to these changes (a and b above) in both plant and microbial functioning, (d) reduced sensitivity of vegetation to N additions in areas with high historical N deposition, (e) delayed changes in soil C:N changes due to increased net primary productivity and reduced decomposition of soil organic matter. Some suggestions of early indicators of N saturation are suggested (occurrence of mosses; ratio in surface soils) which indicate either a shift in ecosystem function and/or structure.     

采用烧结法降低垃圾焚烧飞灰浸出毒性的研究

采用电感耦合等离子体发射光谱仪（ICP-AES）对垃圾焚烧飞灰和造粒烧结后试样中重金属的浸出量进行分析.研究表明,随着烧结时间的增加和烧结温度的提高,大多数重金属浸出毒性都有所降低.对造粒后的飞灰物料进行低温烧结处理,烧结工艺参数可初步定为造粒直径为15mm,烧结温度为950℃-1100℃,烧结时间约为20min.     

机械活化对CRT锥玻璃浸出动力学的影响

通过研究CRT锥玻璃经机械活化后在硝酸溶液体系中浸出反应动力学规律,考察了机械球磨转速、浸出温度以及硝酸初始浓度对锥玻璃中铅的浸出效果影响。研究结果表明,锥玻璃经机械活化预处理后,反应活性显著增强,锥玻璃中铅浸出率大幅度提高。浸出反应的表观活化能和反应级数由109.4 kJ/mol和0.79降至54.3 kJ/mol和0.51。     

铁镁质尾矿中的钙镁浸取效果优化

铁镁质尾矿含有丰富的钙镁,利用浸取剂可以促进铁镁质尾矿中钙镁的释放,使这些尾矿成为固定CO2的材料。尾矿中钙镁的浸出率大小跟多个因素相关,如何寻求浸取钙镁的最优化条件,是有效利用铁镁质尾矿的重要内容。考虑环境友好的方案,采用EDTA、柠檬酸和柠檬酸钠浸取尾矿中的钙镁,并对比了不同条件下的浸取效果。通过比较,显示柠檬酸钠的浸取效果较好,在此基础上利用响应面法对粒度、pH值、固液比等主要影响因子进行优化处理。当反应液的pH=1,尾矿粒度<75μm,固液比为2.6∶100时,模型预测实验尾矿淋滤的Mg2+浓度为143.4 mg/L,Mg达到最佳溶出率2.03%。实验模型的预测精度良好,表明响应面法适用于尾矿的浸取实验优化。     

电镀污泥回收重金属的新工艺

合理、经济地处理混合电镀污泥,回收其中有价值的金属具有重要意义。以不同的酸作为浸出剂对电镀污泥中的金属进行了浸出效果实验。结果表明,在相同条件下,各酸的浸出效果顺序为:硫酸>盐酸>王水>硝酸;液体水与固体电镀污泥比为3,干污泥为5 g,硫酸加入量为15 mL,时间1 h条件下,混合电镀污泥中金属铜锌的浸出率最大,达到97.38%。分别采用铁和铁锰合金还原剂常温还原低熔点重金属离子铜、锌,浸出液中99%以上含量的铜、锌沉淀,使低熔点重金属与黑色金属铁、锰、铬有效分离。低熔点混合重金属可以用来做铜合金添加剂使用,最后沉淀的混合黑色金属氢氧化物处理后可以用来做炼钢合金添加剂使用。     

固体废物中重金属浸出毒性评价方法的研究进展

浸出毒性是固体废物的重要特性之一,亦是判别固体废物是否属于危险废物的重要评价指标.根据与溶液接触方式的不同,固体废物浸出毒性评价方法可以划分为批处理实验、柱淋滤实验和恒pH滴定(pH-stat)实验等.对这3种方法的应用方向、特点和缺陷等进行了系统总结.最后还指出,在评价固体废物中重金属的浸出毒性时,可采用几种方法进行对比,还可以根据实验目的和需求对各个实验参数进行改进,从而得出更全面、客观的评价结果.     

Equilibrium studies on the adsorption of acid dye into chitin

We report the adsorption isotherm of acid dye on the surface of chitin, a unique solid adsorbent. Adsorption process offers an attractive benefit for a dyeing house treatment. Influences of essential kinetic parameters such as adsorbent particle size, reaction temperature governing the dye adsorption have been investigated. Adsorptions isotherms of dye on chitin were developed and the equilibrium data fitted well to the Langmuir, Freundlich and Redlich Peterson isotherm model. At optimum conditions maximum dye adsorption capacity of chitin estimated with the Langmuir 44.0, 85.0, 104.3 mg/g and 85.0, 114.10, 113.62 mg/g adsorbent. The results showed that chelating polymer of chitin could be considered as potential adsorbents for acid dye removal from dilute solution.     

微咸水淋洗对苏打盐渍土土壤理化性状的影响

在轻度盐碱化和中度盐碱化2种苏打盐渍土上,分别设置对照、补充灌溉、低额淋洗和高额淋洗4个处理,对经微咸水淋洗的苏打盐渍土的土壤渗透性、土壤容重以及土壤盐碱含量的分析结果表明,在高额淋洗区,微咸水在中度苏打盐渍土中渗透速率约为对照区的3倍,在轻度苏打盐渍土中约为对照区的2倍。与对照区相比,中度和轻度苏打盐渍土高额淋洗区土壤容重分别降低10.1%和9.5%。在高额淋洗区,中度苏打盐渍土60 cm深度内的含盐量降至1.0 g.kg-1,碱化度降低17.4百分点;轻度苏打盐渍土120 cm深度内含盐量均降至0.6 g.kg-1以下,碱化度也降低7.9百分点。苏打盐渍土土壤理化性状得到明显改善。认为适合中、轻度苏打盐渍土的淋洗定额分别为400和150 mm。     

The mobility of thiobencarb and fipronil in two flooded rice-growing soils

The mobility of the rice pesticides thiobencarb (S-[(4-chlorophenyl) methyl] diethylcarbamothioate) and fipronil ([5-amino-3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]pyrazole) were investigated in the glasshouse under flooded conditions using two Australian rice-growing soils. When using leakage rates of 10 mm day^?1, less than 20% of applied thiobencarb and fipronil remained in the water column after 10 days due to rapid transfer to the soil phase. Up to 70% and 65% of the applied thiobencarb and fipronil, respectively, were recovered from the 0–1 cm layer of soils. Only 5–7% of each pesticide was recovered from the 1–2 cm layer, and less than 2% was recovered from each 1 cm layer in the 2–10 cm region of the soils. Analysis of the water leaking from the base of the soil cores showed between 5–10% of the applied thiobencarb and between 10–20% of the applied fipronil leaching from the soil cores. The high levels of pesticide in the effluent was attributed to preferential flow of pesticide-laden water via soil macropores resulting from the wetting and drying process, worm holes and root channels.     

Impact of soil amendments on metribuzin and DCPA half-lives and mobility into agricultural runoff water

The retention and behavior of two herbicides, metribuzin [4-amino-6-tert-butyl-4, 5-dihydro-3-methylthio-1, 2, 4-triazin-5-one] and DCPA [1, 4-Benzenedicarboxylic acid, 2, 3, 5, 6-tetrachloro-, dimethyl] ester, in runoff and seepage water from agricultural fields were investigated. The objectives of this investigation were to: (i) determine the dissipation and half-life (T _1/2) of metribuzin and DCPA herbicides in soil under three management practices: chicken manure (CM), sewage sludge (SS), and no-mulch native soil (NM); (ii) monitor herbicides residues in runoff and infiltration water following addition of soil amendments; and (iii) determine the impact of soil amendments on the transport of NO₃, NH₄, and PO₄ from soil into surface and subsurface water. Half-life (T _1/2) values of metribuzin were 24, 18, and 12 d in CM, SS, and NM treatments, respectively. Similarly, T _1/2 values of DCPA were greater in CM and SS incorporated soil (45.8 and 52.2 d, respectively) compared to NM native soil (26.2 d). Addition of CM and SS to native agricultural soil increased water infiltration, lowering runoff water volume and herbicide residues in runoff following natural rainfall events. We concluded that soil amendments could be used to intercept pesticide-contaminated runoff from agricultural fields. This practice might provide a potential solution to pesticide contamination of surface and seepage water from farmlands.