Shrimp and fish pond soils: processes and management

The pond bottom soil and the accumulated sediments are integral parts of ponds. Concentrations of nutrients, organic matter and microorganism density in the pond bottom are several orders of magnitude greater than in the water. The accumulation of organic sediments may limit pond intensification. The intensive organic matter degradation at the pond bottom and high sediment oxygen demand exceeds the oxygen renewal rate. This leads to the development of anoxic conditions in the sediments and at the sediment–water interface. A series of anaerobic processes, affected by the redox potential of the system, are taking place. A large number of potentially toxic materials are generated. Among those are organic acids, reduced organic sulfur compounds, reduced manganese and sulfides.

Shrimp, as animals that normally live on or near the bottom, are exposed to conditions on the pond bottom. Exposure to toxic materials endanger the well being of the cultured shrimp. Reduced feeding, slower growth, mortality and possibly higher sensitivity to disease are reported.

The rational use of aerators to minimize the area of sludge accumulation, construction of ponds to trap sludge, stirring sediments, chemical poising of the redox system and environmentally accepted treatment and reuse of drained sediments are means to control the conditions at the pond bottom.     

黄河未来输沙量态势及其适用性对策

[目的] 探索黄河输沙预测的新思路,预估黄河未来输沙态势与输沙量水平,为黄河流域生态治理规划提供参考。[方法] 结合黄河流域水土保持生态修复现状,采用单累积曲线法、滑动平均及频率分析方法,分析1950—2019年黄河主要来沙区间的实测输沙量变化特征及其未来态势。[结果] 1950—2019年黄河输沙量呈现阶梯式减少。1950—2019年黄河中游各站累积实测输沙量随时间的变化可用“左半抛物线”表征。黄河输沙量自1997年以来已进入相对稳定态势,目前已达企稳状态;黄河潼关站未来年输沙量在90%频率下为1.00×10⁸ t左右,在10%频率下为5.00×10⁸ t左右,未来多年平均输沙量为1.40×10⁸ t。[结论] 为了维持黄河输沙量低稳状态,提升水土保持措施质量与标准,补齐“后水土保持”短板,构建完善的水沙关系调控体系,维持黄河下游河道冲淤平衡,是黄河流域生态保护与高质量发展的保障。     

光裸方格星虫(Sipunculus nudus)生物扰动对混养系统沉积物及间隙水中营养物质的影响

采用养殖水化学测定方法分析沉积物中有机质和营养盐含量变化,研究方格星虫生物扰动对混养系统中沉积物的生态效应。混养试验在20个养殖桶内(水体积550 L)进行,方格星虫(1.2±0.1 g)养殖在桶底沙层中,其放养密度为0、50、100和150条/桶;鲻(24.5±0.5 g)的放养密度为3尾/桶,养殖在水体中的网箱中(直径0.8 m、高度0.6 m)。试验共分4个处理组(T0、T50、T100和 T150),每个处理组各设5个重复。结果显示,与对照组(T0)相比,方格星虫组底层(6–8 cm)沙中有机质含量有所增加,但未达到统计学显著差异(P>0.05)。随着试验的进行,4个试验组的间隙水中硝态氮(NO3-N)、氨氮(NH4-N)以及活性磷(SRP)浓度均呈现出升高的趋势。试验结束时,T100和 T150组各层间隙水的 NO3-N 浓度均低于T0组(P<0.05),且底层间隙水的 NO3-N 浓度随方格星虫密度的增加而降低;T0组表层 NH4-N 浓度高于方格星虫组,而底层氨氮却显著低于高密度方格星虫组(T100和 T150)(P<0.05)。结果表明,方格星虫的生物扰动在一定程度上可以促进沉积物表层的有机质向底层转移,从而影响间隙水中氮、磷营养盐的转化和释放。方格星虫的生物扰动在精养池塘中的底质修复作用仍需进一步研究。     

Soy protein concentrate as a substitute for fish meal in diets for juvenile Acanthopagrus schlegelii: effects on growth,phosphorus discharge and digestive enzyme activity

The current high demand and cost of fish meal (FM) necessities the evaluation of alternative plant protein ingredients in diets of farmed marine fish. A 56‐day feeding trial was performed to study the effects of replacement of FM with soy protein concentrate (SPC) in diets of Acanthopagrus schlegelii. Diets were prepared at levels of 0%, 30%, 47.5%, 65%, 82.5% and 100% SPC, respectively, replacing FM. The results indicated no significant differences (p > .05) in % weight gain (WG) and specific growth rate of fish fed S30% to S82.5% diets compared with the control diet while, further inclusion at 100% significantly depressed growth performance. SPC inclusion and phytase supplementation significantly affected the phosphorous discharge (P‐load) showing lowest value (3.83 ± 0.53 g/kg WG) in S100% compared to control (14.79 ± 0.37 g/kg WG) and in fish fed S30% diet (13.24 ± 0.89 g/kg WG) (p < .05). The results of this study showed that FM could be substituted up to 82.5% by SPC in the diet of Acanthopagrus schlegelii fingerlings (5.53 ± 0.12 g) without any adverse effects. Phytase supplementation SPC based diets could be effective in reducing the phosphorus load in the aquatic culture environment.     

基于多层C／S结构的医疗管理系统的开发与应用

随着经济的快速发展，环境污染越来越严重。排污权作为一项权利提出以后，其法律性质及法域归属问题争议颇多，有学者认为排污权是以环境容量为客体的用益物权，归属物权法域。从排污权的特殊性和现有立法规定看，排污权是以环境资源为客体的一种环境权，归属于环境法域。     

浅谈提高房地产项目环评审批效率的措施

为提高苏州高新区房地产建设项目的环评审批效率,在此分析了房地产项目的建设特点及环评审批现状,并结合相关的法律法规依据,提出合理调整环评评价内容、降低环评评价等级、提高环评审批效率的意见和建议。     

Evaluating Sediment Accretion on a Relic Oyster Reef in Mobile Bay,Alabama

Abstract

Sediment traps were deployed at Fish River Reef (FRR), a relic oyster reef on the eastern side of Mobile Bay, and at Cedar Point Reef (CPR), a productive oyster reef on the western side of Mobile Bay, Alabama, from July through October 1999. Sediment accretion at FRR was two to three times greater than sediment accretion at CPR. The proportions of particulate organic matter and ash in the sediment at the two sites were similar. The proportion of coarse to fine sediment at CPR was greater than at FRR. Also, the sediment at FRR was black and had a sulfide odor suggesting anoxia, while the sediment at CPR was brown and odorless. Various fishes and invertebrates colonized the sediment traps at CPR, while those at FRR were devoid of live organisms. Oyster spat had settled on the shells in the traps at CPR but not on those at FRR. Results suggest that in order to restore oysters at FRR, cultch material should be dispersed during periods of peak larval settlement to prevent inhibitory levels of siltation on cultch before spat settle.     

气相色谱-电子捕获检测器测定电子废弃物处理场地底泥中的四溴双酚-A

通过优化分析仪器的条件设置，建立了使用气相色谱-电子捕获检测器技术分析四溴双酚-A（TBBP—A）的仪器分析方法。样品采用正己烷索氏提取、硅胶柱分离纯化、外标法定量，结果表明，测定方法在测量范围内具有良好的线性关系，测定的平均回收率为86．8％，检出限为5．0ng／ml，相对标准偏差为3．26％～8．77％：     

油量计量的微计算机控制

讨论了运用ＣＭＣ－８０双板机控制成品油库发油计量的原理和实现方法，该控制装置已在实际系统中使用。