Emergy Assessment of a Wheat-Maize Rotation System with Different Water Assignments in the North China Plain

Sustainable water use is seriously compromised in the North China Plain (NCP) due to the huge water requirements of agriculture, the largest use of water resources. An integrated approach which combines the ecosystem model with emergy analysis is presented to determine the optimum quantity of irrigation for sustainable development in irrigated cropping systems. Since the traditional emergy method pays little attention to the dynamic interaction among components of the ecological system and dynamic emergy accounting is in its infancy, it is hard to evaluate the cropping system in hypothetical situations or in response to specific changes. In order to solve this problem, an ecosystem model (Vegetation Interface Processes (VIP) model) is introduced for emergy analysis to describe the production processes. Some raw data, collected by investigating or observing in conventional emergy analysis, may be calculated by the VIP model in the new approach. To demonstrate the advantage of this new approach, we use it to assess the wheat-maize rotation cropping system at different irrigation levels and derive the optimum quantity of irrigation according to the index of ecosystem sustainable development in NCP. The results show, the optimum quantity of irrigation in this region should be 240–330 mm per year in the wheat system and no irrigation in the maize system, because with this quantity of irrigation the rotation crop system reveals: best efficiency in energy transformation (transformity = 6.05E + 4 sej/J); highest sustainability (renewability = 25%); lowest environmental impact (environmental loading ratio = 3.5) and the greatest sustainability index (Emergy Sustainability Index = 0.47) compared with the system in other irrigation amounts. This study demonstrates that application of the new approach is broader than the conventional emergy analysis and the new approach is helpful in optimizing resources allocation, resource-savings and maintaining agricultural sustainability.     

旋转填充床中Fenton+O_3氧化降解模拟阿莫西林废水

以旋转填充床(RPB)作为反应装置,研究了Fenton工艺与Fenton+O3工艺处理模拟阿莫西林废水的效果,考察了FeSO4·7H2O的投加量、温度、旋转床转速、液体流量及pH对COD去除率的影响。实验表明,Fenton+O3工艺的COD脱除率及BOD5/COD相对于Fenton工艺分别提升26.7%和140%。该工艺在pH为3、温度为25℃、液体流量30 L/h、气体流量2.5 L/h、转速800 r/min、H2O2的投加量为1 mmol/L及Fe2+投加量为0.4 mmol/L的条件下,100 mg/L的模拟阿莫西林废水中COD的去除率达到57.9%,BOD5/COD从0增加到0.36,满足后续生化处理要求。     

Distribution and habitat characteristics of fishes in the Pearl River Estuary北大核心CSCD

To explore the current situation and distribution of fish in the eight major estuaries of the Pearl River Estuary in China, acoustic detection and water quality monitoring were conducted in 2018. The results showed that almost living in eight major estuaries were juvenile, the proportion of strong echo was higher in winter, and Jiaomen and Modaomen Estuary were relatively rich in adult fish. In winter, the Humen, Jiaomen, and Yamen Estuary had a high density relatively, for 46.05 (± 50.30), 33.12 (± 93), and 32 (± 78) ind/103 m3, respectively. However, the fish densities of the Hengmen, Modaomen, and Hutiaomen estuaries were higher in summer at 55.72 (± 83.23), 37.52 (± 55) and 36 (± 99) ind/103 m3, respectively. Thus, fish are mainly concentrated in the flood tidal estuary in winter and in the ebb tidal estuary in summer. In addition, fish density was higher in flood tide than in ebb tide, and the strong echo proportion was lower. In winter, the key water quality factors affecting the biodiversity of estuary fish Shannon were chlorophyll a (P < 0.05), while what affected the fish density were turbidity and salinity (P < 0.05). This study showed that the Pearl River estuary was still the main habitat for juvenile fish. However, habitat variability is obvious; hence, it is important to flexibly carry out the delimitation of estuarine fish reserves and ecological restoration. © 2022 Authors. All rights reserved.     

Application of surrogate methods for assessing the bioavailability of PAHs in sediments to a sediment ingesting bivalve

The usefulness of two surrogate methods for rapidly determining the bioavailability of PAHs in hydrocarbon-contaminated marine sediments was assessed. Comparisons are made between the PAHs accumulated by the benthic bivalve, Tellina deltoidalis, and the extractable-PAHs determined using a 6-h XAD-2 resin desorption method and a 4-h gut fluid mimic (GFM) extraction method. There were significant positive relationships between PAH bioaccumulation by the bivalves and sediment PAH concentrations. These relationships were not improved by normalising the sediment PAH concentrations to the organic carbon concentration. The average percentage lipid content of the bivalves was 1.47 ± 0.22% and BSAFs for total-PAHs ranged from 0.06 to 0.80 (kg OC/kg lipid). The XAD-2 and GFM methods both extracted varying amounts of PAHs from the sediments. Low concentrations of PAHs were extracted by the GFM method (0.2–3.6% of total-PAHs in sediments) and the GFM results were inadequate for generalising about the bioavailability of the PAHs in the sediments. The XAD-2 method extracted greater amounts of PAHs (3–34% of total-PAHs in sediments), however, the total-PAH concentrations in the sediments provided a better, or equally good, prediction of PAH bioaccumulation by T. deltoidalis. The results indicated that these methods required further development before they can be applied routinely as surrogate methods for assessing the bioavailability of PAHs in sediments. Future research should be directed towards lowering detection limits and obtaining comparative data for a greater range of sediment types, contaminant classes and concentrations, and organisms of different feeding guilds and with different gut chemistry.     

复合磁性光催化剂Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6的制备及其光催化性能

以Co_(0.5)Zn_(0.5)Fe_2O_4为磁基体,制备了Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6复合磁性光催化剂。分别采用XRD、SEM、EDS和PL光谱技术对光催化剂进行了表征。利用氙灯为光源,以环丙沙星为目标污染物,考察了光催化剂对环丙沙星的降解性能。表征结果显示:复合磁性光催化剂中Bi_2WO_6晶相含量高,且结晶度大;Co_(0.5)Zn_(0.5)Fe_2O_4与Bi_2WO_6的质量比为1∶8时,Co_(0.5)Zn_(0.5)Fe_2O_4磁基体与Bi_2WO_6基本复合(该复合磁性光催化剂以Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6(Ⅱ)表示);Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6复合光催化剂光生空穴和电子复合几率低,具有较好的光催化性能。实验结果表明,Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6(Ⅱ)具有较高的光催化活性,光催化反应140 min后对环丙沙星的降解率达82.39%,且具有良好的磁性能,易实现固液分离,便于回收再利用。     

三种环境动力学模型建模方式的比较

在农药和化学品的风险评估工作中,环境动力学模型正得到越来越多的应用。采用Stella软件、Matlab M文件和Matlab Simulink 组件3种建模方式分别构建了微宇宙、湖泊和海湾系统的多介质环境动力学模型,并对3种方式的建模难度、计算耗时及模型直观性进行了比较。研究结果表明：Stella模型最直观,但提供的计算方法有限,更适用于微分方程数量不多且计算周期短的模型;M文件模型建模速度最快,但在直观性和计算速度上没有优势,不建议在环境动力学模型中使用;Simulink模型兼具直观性和计算速度快的优点,无论微分方程数量多少,在需要进行长周期计算的模型中都最具优势。     

Accelerated sunlight photocatalysis through improved electron mobility between g-C3N4 and BiPO4 nanomaterial

Herein, we report a detailed study on creating heterojunction between graphitic carbon nitride (g-C₃N₄) and bismuth phosphate (BiPO₄), enhancing the unpaired free electron mobility. This leads to an accelerated photocatalysis of 2,4-dichlorophenols (2,4-DCPs) under sunlight irradiation. The heterojunction formation was efficaciously conducted via a modest thermal deposition technique. The function of g-C₃N₄ plays a significant role in generating free electrons under sunlight irradiation. Together, the generated electrons at the g-C₃N₄ conduction band (CB) are transferred and trapped by the BiPO₄ to form active superoxide anion radicals (?O₂^?). These active radicals will be accountable for the photodegradation of 2,4-DCPs. The synthesized composite characteristics were methodically examined through several chemical and physical studies. Due to the inimitable features of both g-C₃N₄ and BiPO₄, its heterojunction formation, 2.5wt% BiPO₄/g-C₃N₄ achieved complete 2,4-DCP removal (100%) in 90 min under sunlight irradiation. This is due to the presence of g-C₃N₄ that enhanced electron mobility through the formation of heterojunctions that lengthens the electron-hole pairs’ lifetime and maximizes the entire solar spectrum absorption to generate active electrons at the g-C₃N₄ conduction band. Thus, this formation significantly draws the attention for future environmental remediation, especially in enhancing the entire solar spectrum’s harvesting.

Graphical abstract