Rocky coast processes: with special reference to the recession of soft rock cliffs

Substantial progress in research on the recession of coastal cliffs composed of soft materials has been made in recent years and data with higher accuracy have been accumulated. This paper provides the state of the art review in the recession studies and highlights two new findings obtained from the reanalysis of existing data. The review topics are: episodic and localized nature of cliff recession; the development of cliffline; the relationship between cliff height and recession rate; mechanisms of cliff toe erosion by waves; a fundamental equation for wave-induced toe erosion; factors controlling toe erosion; and slope instabilities and mass movements. The findings are presented on (1) the temporal change in cliffline recession mode and (2) the effect of beach sediment at the cliff base on the cliff erosion.     

Development of novel backwash cleaning technique for reverse osmosis in reclamation of secondary effluent

The objective of the study was to further develop a novel cleaning technique for reverse osmosis in reclamation of municipal secondary effluent. This technique is a new backwash method via direct osmosis (DO) by intermittent injection of the high salinity (HS) solution without stopping of high pressure pump and it is environment and membrane friendly technique. In the study, DO-HS trials were carried out with a UF-RO pilot system which was operated on site with the secondary treated effluent as the raw feed. Different operating conditions for DO-HS treatment in the actual process were investigated. It was found that the operation for implementation of the DO-HS cleaning technique developed was easy. For the first time, the actual profiles of HS concentration, DO backwash flow rate, brine flow rate and permeate pressure during DO-HS treatment have been demonstrated. It was observed that turbidity of the brine stream during DO-HS treatment at 3 NTU was 5 times higher than that before DO-HS treatment. The results from this study have confirmed the previous hypothesis with DO-HS treatment that there would be a strong driving force for DO backwash to lift and sweep the foulants from the membrane surface which would be carried over to the brine. The optimal plant operating conditions in terms of RO feed flow rate, HS concentration and HS injection time are ready for the DO-HS method to be adopted and validated in a long-term continuous plant operation.     

BEWARE OF THE BEACH HIDDEN KILLER--RIP CURRENT

离岸流是垂直于海岸线、向外海方向快速移动的强劲海流。对于海边的人员来说非常危险,没有经验的游泳者一旦被离岸流带离浅滩,很难与之对抗游回岸边,往往因力竭而溺水。每年海滨区域都有大量的溺亡事件与此相关,但有关离岸流的知识在公众的视野里仍比较缺乏。本文从流体力学的角度对离岸流的危害、形成、特征以及分类进行了简要介绍,并在如何防范离岸流、保障自身安全等方面给出了一些建议。     

北仑地区的岸滩动态

本文依据水文、沉积和地貌资料,分析论证了北仑地区的岸滩动态,认为北仑地区岸滩已接近动态平衡,具备开辟深水良港的自然条件。     

煤炭矿区植被冠层光谱土地复垦敏感性分析

煤矿区土地复垦及复垦监测工作,对于我国土地利用和生态环境治理具有重要意义。微生物复垦技术能够促进植物吸收利用矿质养分和水分,增强土壤肥力,对矿区生态恢复具有显著作用。监测和评价土地复垦效应对植物生长影响的传统方法,通常采用野外采集植物和土壤样本并进行室内分析,但这些方法不仅破坏植物根系原状土壤,造成植株损伤,而且耗费人力、物力,时效性差。高光谱遥感技术具有数据获取速度快、信息量大、精度高且无须离体破坏植株等优点,对于土地复垦监测有非常大的潜力。目前,土地复垦效应遥感监测相关研究仍以观测盆栽大豆、玉米等作物的叶片光谱分析为主。实际上,卫星遥感数据观测到的是冠层光谱,并非叶片光谱,但目前还没有通过植被冠层光谱对矿区土地复垦进行监测的研究成果出现。植被冠层光谱不仅受到叶片光谱的影响,还受到植株长势、下垫面等其他因素的影响,光谱特征变化更为复杂。矿区植被冠层光谱特征对于土地复垦效应的敏感度分析,是对矿区植被理化参量进行定量反演的基础,也是限制高光谱技术应用于大面积土地复垦监测的主要瓶颈。于煤炭矿区土地复垦实验基地开展野外冠层光谱观测实验,获取了接菌组和对照组野外植株冠层光谱数据,并从光谱波形变化和光谱特征参量变化两方面综合分析了植被冠层光谱对土地复垦的敏感性。冠层光谱波形方面,分别采用标准差和光谱敏感度作为组内和组间光谱波形差异的有效指标;冠层光谱特征参量方面,选取了植被红边、黄边、蓝边、绿峰、红谷等典型光谱特征,计算获取其位置、斜率、面积等特征参量,并通过描述性统计和单因素方差分析研究了这些冠层光谱特征参量对土地复垦效应的敏感性,挑选出矿区土地复垦监测的有效特征参量。研究表明,接菌组和对照组冠层光谱的主要波形变化趋势一致,但接菌组植株的生长状况更稳定,不同植株之间差异较小,且绿峰和红谷两个特征更突出。这说明土地复垦能够减少植株间冠层光谱差异,增强植被典型光谱特征,而绿峰和红谷对土地复垦有较高的光谱敏感度。光谱特征参量方面,绿峰、红谷、红边波长在土地复垦作用下显著向长波方向移动,而此前叶片光谱研究中对土地复垦较敏感的红边、蓝边斜率变化并不显著。这说明,野外植被冠层光谱分析结果与实验室植被叶片光谱分析的结果并不完全一致,这可能和植被类型、生长周期、土壤背景光谱干扰等因素相关。在采用卫星或航拍遥感数据进行矿区植被环境监测时,所获取的都是植被冠层光谱,因此本研究所得到的结论具有更强的参考意义和实际应用价值。     

以催化裂化废催化剂为原料合成NaY分子筛的研究

针对催化裂化(FCC)废催化剂的回收利用问题,提出了一种废催化剂再利用的方法,即以FCC废催化剂为铝源,合成时只补充部分硅源,采用自制的高效NaY沸石导向剂,水热合成NaY分子筛。同时,以普通的化工原料合成了对比试样Y型分子筛。讨论了不同的FCC废催化剂预处理方式对合成产物性能的影响,发现以经过碱熔活化处理的废催化剂为原料合成的Y分子筛拥有更高的结晶度和纯度。采用X射线衍射、热分析、程序升温脱附法(NH3-TPD)和N₂静态容量吸附法对结晶产物和对比样品的晶体结构,热稳定性、酸性质、比表面积以及孔分布进行了表征。结果显示,以FCC废催化剂为原料完全可以合成出与普通原料性能接近的NaY分子筛。其BET比表面积可以达到615 m²·g^-1,孔体积可达0.38 cm³·g^-1,孔径集中在0.51 nm左右。     

煤矸石充填复垦重构土壤重金属含量高光谱反演

为研究煤矸石充填复垦土壤重金属含量快速有效的监测方法,以淮南创大生态园煤矸石充填复垦田间试验小区为研究区域,首先采用化学方法监测土壤(0～20 cm)重金属(Cu, Cr, As)含量,然后采用ASD(analytical spectral devices) FiSpec4型高光谱仪测量土壤样品的反射光谱,提取光谱特征,并对光谱进行一阶微分变换、二阶微分变换及倒数对数变换;将变换后的各光谱特征参数与监测的土壤重金属含量进行相关性分析,并依据相关性分析结果选择显著相关的波段作为相关因子供建模使用。采用多元逐步回归(stepwise multiple liner regression,SMLR)分析、偏最小二乘回归(partial least squares regression, PLSR)及人工神经网络(artificial neural network, ANN)三种方法分别建立基于光谱反射率估算土壤重金属含量的预测模型,并采用回归模型进行精度评定,然后确定各重金属含量的最佳预测模型。实验结果表明,经过微分变换的光谱波段与土壤重金属含量达到了显著相关;重金属Cu和Cr的一阶微分光谱的人工神经网络模型为最佳预测模型,重金属元素As的二阶微分光谱的偏最小二乘回归模型为最佳预测模型。     

Effect of large-scale reservoir and river regulation/reclama-tion on saltwater intrusion in Qiantang Estuary

By using field salinity data recorded in the Qiantang Estuary for the nearly forty years (which covers the periods before and after the erection of a large-scale reservoir in the watershed and river regulation/reclamation in the estuary) and one-dimensional salt water intrusion modeling, it is shown that the salt water intrusion decreases caused by increased low water discharge for the reservoir, while the intrusion increases for the increased tidal range because of the river regulation/reclamation. The integrate result is that the saltwater intrusion decreases.     

Fouling of reverse osmosis membranes by biopolymers in wastewater secondary effluent: Role of membrane surface properties and initial permeate flux

Reverse osmosis (RO) is being increasingly used in treatment of domestic wastewater secondary effluent for potable and non-potable reuse. Among other solutes, dissolved biopolymers, i.e., proteins and polysaccharides, can lead to severe fouling of RO membranes. In this study, the roles of RO membrane surface properties in membrane fouling by two model biopolymers, bovine serum albumin (BSA) and sodium alginate, were investigated. Three commercial RO membranes with different surface properties were tested in a laboratory-scale cross-flow RO system. Membrane surface properties considered include surface roughness, zeta potential, and hydrophobicity. Experimental results revealed that membrane surface roughness had the greatest effect on fouling by the biopolymers tested. Accordingly, modified membranes with smoother surfaces showed significantly lower fouling rates. When Ca²⁺ was present, alginate fouled RO membranes much faster than BSA. Considerable synergistic effect was observed when both BSA and alginate were present. The larger foulant particle sizes measured in the co-existence of BSA and alginate indicate formation of BSA-alginate aggregates, which resulted in greater fouling rates. Faster initial flux decline was observed at higher initial permeate flux even when the flux was measured against accumulative permeate volume, indicating a negative impact of higher operating pressure.     

应用ICP-MS分析猪污物中铅砷镉的形态分布

为有效控制资源化过程中畜禽污物所含重金属对环境和人类健康的危害,需要监测污物中重金属的赋存形态和浓度。采集北京昌平种猪场的猪污物样品(鲜样和干清样),用BCR提取法、硝酸-高氯酸消化法和ICP-MS仪器检测铅砷镉(Pb,As,Cd)总量及各形态含量。结果表明,猪污物中Pb,As,Cd的总量分别为29.0,28.2和0.288 mg·kg-1 DW(鲜样)以及19.7,28.2 和0.134 mg·kg-1 DW(干清样),均没有超过我国的城镇垃圾农用控制标准(As接近标准值)。两类样品中重金属的形态分布规律明显不同：鲜样中三种金属可交换态及碳酸盐结合态均超过50%,有机物及硫化物结合态则低于20%;而干清样中高生态毒性的可交换态及碳酸盐结合态和Fe/Mn氧化物结合态的比例较鲜样中都明显降低(降幅可达20%以上),表明干清样用于堆肥对农田更安全。该研究结果将为北京地区养猪场污物的资源开发和生态安全评价提供重要基础数据。