Modelling tritrophic interactions mediated by induced defence volatiles

Many plant species defend themselves against herbivorous insects indirectly by producing and releasing induced volatiles to attract natural enemies of the herbivores. In this paper, we consider the recruitment of natural enemies attracted by plant-induced volatiles and introduce the An–Liu–Johnson–Lovett model into the Lotka–Volterra model in an attempt to add this missing vital link in tritrophic interaction. Increase in attraction strength of plant-induced volatiles to the natural enemy leads to high fluctuation amplitude of plant biomass and herbivore population. When the attack strength of natural enemies reaches a certain level, fluctuation amplitude of plant biomass and herbivore population will decrease and plant biomass will approach to its environmental carrying capacity. The simulation demonstrates that plant volatile compounds induced by insects have led to the introduction of a third tritrophic level, e.g., natural enemies, into the plant–herbivore system, resulting in the coexistence of plants, insects, and natural enemies during the evolution process.     

3种典型地区农村污水排放特征调查分析

目前,我国农村污水的处理率很低,农村污染问题日益受到关注。为了深入了解我国农村污水特征,在北京、浙江和云南等地分别选择水库水源地保护区、河网地区和风景旅游区内的村庄进行农村污水排放特征的调查研究,以期为农村污水治理提供准确的基础数据。调查方法包括资料调研、入户调查和现场采样监测。结果表明,生活污水和畜禽养殖污水与粪便是村落的主要点污染源,不同区域农村用水习惯不同,污水排放规律差异较大;河网地区的村落对河浜污染状况非常严重,成为隐性污染源;旅游风景区内村庄污水特征受季节影响显著。     

利用太阳能驱动的一体化氧化沟的运行方式

污水处理的高能耗和新能源利用已引起人们的关注,本文根据太阳光照强度的周期变化和农村污水昼夜排放量悬殊的特征,提出了一种新型的利用无蓄电池太阳能光伏系统驱动的污水生物处理系统,可有效降低太阳能光伏系统的成本。生物反应器是一个双沟式一体化氧化沟。按照启动的用电设备的数量,一体化氧化沟具有5种运行方式。在不同的运行方式下,一体化氧化沟的内沟和外沟具有不同的功能,其中运行方式3到运行方式5对污染物去除效率最高。采用阶梯型电量输出模式,可以充分利用太阳能,并保障一体化氧化沟的高效运行时间。在160 d的连续运行实验中,COD、氨氮、总氮和总磷的平均去除率分别为87.8%、98.4%、68.7%和80.3%。证明无蓄电池太阳能光伏系统驱动污水生物反应器处理农村分散污水是可行的。     

典型城市居民集中区初期降雨径流污染特征和生物炭对其氮磷去除效果研究

居民集中区初期降雨径流是城市面源污染的重要来源之一,其主要污染物包括总氮(TN)、总磷(TP)、硝态氮(NO3--N)等,可引发受纳水体富营养化,从而对城市居民集中区的水体环境安全和城市景观造成危害.以典型城市(无锡)居民集中区为研究对象,采用现场监测的方式重点开展了典型城市居民集中区不同下垫面初期降雨径流中主要污染物...     

An innovative integrated system utilizing solar energy as power for the treatment of decentralized wastewater

This article reports an innovative integrated system utilizing solar energy as power for decentralized wastewater treatment, which consists of an oxidation ditch with double channels and a photovoltaic (PV) system without a storage battery. Because the system operates without a storage battery, which can reduce the cost of the PV system, the solar radiation intensity affects the amount of power output from the PV system. To ensure that the power output is sufficient in all different weather conditions, the solar radiation intensity of 78 W/m 2 with 95% confidence interval was defined as a threshold of power output for the PV system according to the monitoring results in this study, and a step power output mode was used to utilize the solar energy as well as possible. The oxidation ditch driven by the PV system without storage battery ran during the day and stopped at night. Therefore, anaerobic, anoxic and aerobic conditions could periodically appear in the oxidation ditch, which was favorable to nitrogen and phosphate removal from the wastewater. The experimental results showed that the system was efficient, achieving average removal efficiencies of 88% COD, 98% NH 4 + -N, 70% TN and 83% TP, under the loading rates of 140 mg COD/(g MLSS·day), 32 mg NH 4 + -N/(g MLSS·day), 44 mg TN/(g MLSS·day) and 5 mg TP/(g MLSS·day).     

Simultaneous determination of ten taste and odor compounds in drinking water by solid-phase microextraction combined with gas chromatography-mass spectrometry

Taste and odor （T＆O） problems in drinking water frequently occur because of many compounds present in the water, of which trans-1,10-dimethyl-trans-9-decalol （geosrnin） and 2-methylisoborneol （MIB） are well-known. In this study, a fast and effective method was established for simultaneous determination of 10 T＆O compounds, including geosmin, MIB, 2,4,6-trichloroanisole （TCA）, 2-methylbenzofuran, 2-isopropyl-3-methoxypyrazine （IPMP）, 2-isobutyl-3-methoxypyrazine （IBMP）, cis-3-hexenyl acetate, trans,trans-2,4-heptadienal, trans, cis-2,6-nonadienal, and trans-2-decenal in water samples by headspace solid-phase microextraction （SPME） coupled with gas chromatography-mass spectrometry. An orthogonal array experimental design was used to optimize the effects of SPME fiber, extraction temperature, stirring rate, NaC1 content, extraction time, and desorption time. The limits of detection ranged from 0.1 to 73 ng/L were lower than or close to the odor threshold concentrations （OTCs）. All the 10 T＆O compounds were detected in the 14 water samples including surface water, treatment process water and tap water, taken from a waterworks in Lianyungang City, China. MIB and geosmin were detected in most samples at low concentration. Six T＆O compounds （IPMP, IBMP, trans,cis-2,6-nonadienal, 2-methylbenzofuran, trans-2-decenal, and TCA） were effectively decreased in water treatment process （sedimentation and filtration） that is different from cis-3-hexenyl acetate, MIB and geosmin. It is noted that the TCA concentrations at 15.9-122.3 ng/L and the trans,cis-2,6-nonadienal concentrations at 79.9-190.1 ng/L were over 10 times higher than their OTCs in tap water. The variation of the analytes in the all water samples, especially distribution system indicated that distribution system cannot be ignored as a T＆O compounds source.     

近40 a秦岭生境质量时空变化特征及驱动机制

运用InVEST模型,研究秦岭生境质量时空变化及驱动机制,以期为秦岭生态文明建设与秦岭区域可持续发展提供理论依据。结果表明：秦岭土地利用方式以林地和草地为主,主要分布于中、西部,耕地与建设用地主要分布在东、南部。人类对秦岭干扰程度在2000年后开始增加,土地利用变幅超过总面积的2%。1980年、1990年、2000年、2010年、2020年,秦岭的平均生境质量（范围0—?1）分别为0.7592、0.7594、0.7586、0.7585、0.7617,均处于“较高”等级。空间分布上,秦岭生境质量中、西部等级高,而东、南部等级低。在像元尺度上,秦岭生境质量较为稳定,显著变化的区域面积仅为2.74%。显著升高的区域主要集中在西南部略阳、勉县等区县,显著降低的区域主要集中在东部的洛南、商州等区县。秦岭的生境质量表现出显著的空间集聚特征,21世纪后,秦岭高质量生境集聚区域面积扩张,低质量的生境集聚区域面积降低。土地利用程度是影响秦岭生境质量最大的驱动因子,与之呈现显著的负相关关系,且影响范围分布于全域。秦岭生境质量的降低源于人类活动引起生境威胁源——建设用地与耕地的扩张,而生境质量的升高可能源于...     

重力式挡土墙抗震稳定性检算最不利状态选取探讨∗

重力式挡土墙整体稳定性检算最不利状态选取对抗震设计有重要影响。针对加速度峰值、墙身外倾峰值、墙顶位移峰值三种典型挡墙抗震危险时刻以及常用“土压力峰值时刻包络”取值方法,以振动台模型试验揭示地震土压力取值结果差异性,基于重力式挡土墙ABAQUS 有限元模型地震响应计算,分析各危险时刻墙背土压力取值及整体稳定性检算结果差异,提出抗震稳定性检算最不利状态建议。结果表明：（1）随地面峰值加速度和墙高增加,三种危险时刻地震土压力均呈现从非线性分布向近似正三角图式转化,合力及作用点高度整体上较现行抗震规范分别大49% 和18%;（2）峰值包络法因不能反映墙-土运动主/被动状态和地震动传导时延特征,致使墙顶附近土压力取值结果过大,地震土压力合力较危险时刻大一倍且作用点偏高约25%;（3）墙身外倾峰值危险时刻的抗滑移稳定系数较其余两种危险时刻偏小14%~33%,且随地面峰值加速度增大反映出更明显的衰减敏感性,以此作为抗震稳定性检算最不利状态有利于结构安全与经济性协调。     

高锰酸钾-过氧化氢-苯酚化学发光体系的研究

采用流动注射技术,研究了高锰酸钾-过氧化氢-苯酚的化学发光行为,对影响化学发光强度的诸因素进行了实验和探讨,建立了流动注射化学发光法测定苯酚的新方法.方法的检出限为3×10-8g/mL,线性范围为1.0×10-7-1.0×10-4g/mL,对4.0×10-6g/mL的苯酚进行11次平行测定,得方法的相对标准偏差为1.6%.方法用于废水中苯酚含量的测定,结果与分光光度法测得值一致.     

洪水淹没对矿区下游农用地土壤重金属污染特征的影响

为评估洪水淹没对西南某有色金属矿区下游农用地土壤重金属污染状况及土壤质量的影响,采用单因子指数法、内梅罗指数法、潜在生态风险指数法,对矿区下游淹没区及非淹没区农用地进行评价.结果表明,研究区域内主要重金属污染物为Cd、Sb、Pb、As、Zn,淹没区6种重金属As、Cr、Pb、Zn、Cd、Sb的平均含量分别为36.66、63.48、82.54、128.21、0.61、39.46 mg·kg~(-1),非淹没区6种重金属As、Cr、Pb、Zn、Cd、Sb的平均含量分别为7.38、71.44、13.27、35.27、0.16、5.62 mg·kg~(-1),除重金属Cr外,淹没区与非淹没区重金属平均含量存在显著性差异(p0.05).淹没区As、Pb、Zn、Cd、Sb的超标率分别为52.23%、44.54%、48.14%、72.03%、88.25%,非淹没区As、Pb、Zn、Cd、Sb的超标率分别为4.12%、3.23%、2.16%、15.03%、22.00%,淹没区土壤环境质量类别为安全利用,综合潜在环境风险为很强生态风险(RI=600.3),非淹没区土壤环境质量呈现优先保护状态,综合潜在环境风险为轻微生态风险(RI=69.1).有色金属矿区下游农用地被洪水长期淹没导致As、Pb、Zn、Cd、Sb的污染加重,由于研究区域特殊的地质背景,土壤中大量存在的铁锰氧化物胶膜对重金属具有强吸附作用,当洪水中存在大量重金属,随着水位上升洪水浸没土壤,铁锰氧化物胶膜把大量重金属截留在中下层土壤中,从而导致污染更为严重.