Hydrogenative pyrolysis of waste tyres: kinetic analysis

A kinetic model for the hydrogenative liquid-solid pyrolysis of waste tyres is presented. The model is tested with available experimental data obtained by running the pyrolysis of tyre particles (size < 500 μm) in a stirred batch reactor, in the presence of tetralin (as hydrogen donor), under a nitrogen atmosphere, and in the temperature range 345–430°C. Because a huge number of products is formed during the pyrolysis process, the compounds have been classified into homogeneous groups. On the basis of the proposed model, a reaction network which describes the evolution of these groups has been set. The kinetic constants of the reactions entering the network have been evaluated at 345, 393, and 430°C. The analytical equations obtained from the model fit the data satisfactorily.

The results of the investigation indicate that the first step of the pyrolysis is the rupture of weak bonds which leads to the dissolution of the tyre particles as large aggregates of molecules, in a time which is of the order of 1 min. Then, much more slowly, lighter products are released from these aggregates. At T = 430°C the large aggregates are completely transformed into stable compounds, detectable by GC, in about 250 min. At lower temperatures, T = 345°C, after 250 min 40% of the loaded tyre is still present as macromolecules not detectable by GC.     

短路波导法的新应用

本文介绍一种测定不能进行机械加工的“固体材料”（农产品或矿物）微波介电特性的新方法。将这类材料研碎，成为“空气－粒子”混合物，应用短路波导方法，对几种不同的“松密度”混合物测量其介电特性（介电常数和损耗因子）。当已知待测材料的“固体密度”时，利用这些测得特性与混合物“松密度”的线性函数关系进行“外推”，从而获得“固体密度”下的农产品（或矿物）的微波介电特性。     

Plant detection and mapping for agricultural robots using a 3D LIDAR sensor

In this article, we discuss the advantages of MEMS based 3D LIDAR sensors over traditional approaches like vision or stereo vision in the domain of agricultural robotics and compare these kinds of sensors with typical 3D sensors used on mobile robots. Further, we present an application for such sensors. This application deals with the detection and segmentation of plants and ground, which is one important prerequisite to perform localization, mapping and navigation for autonomous agricultural robots. We show the discrimination of ground and plants as well as the mapping of the plants. Experiments conducted using the FX6 LIDAR by Nippon Signal were carried out in the simulation environment Gazebo, with artificial maize plants in the laboratory and on a small maize field. Our results show that the tested plants can be reliably detected and segmented from ground, despite the use of the low resolution FX6 sensor. Further, the plants can be localized with high accuracy.     

我国农业网站建设与评价研究

农业网站的建设有其自身的特殊性,本文首先简单介绍了农业网站的建设过程、分析了目前农业网站存在的问题,然后对农业网站的评价指标进行了建构。     

Abandoned farmlands as components of rural landscapes: An analysis of perceptions and representations

In spite of its importance in some agricultural landscape, abandoned farmland remains relatively little studied. Yet it is central to several land management issues: ecological (biodiversity), economic (agricultural or forest productivity) and landscape issues. In order to better address these issues, this study proposes to define how abandoned farmland is perceived in an intensive agricultural landscape. Using photographs, the perceptions of abandoned farmland (herbaceous and shrub dominated) and 5 other land uses (hay fields, corn fields, pastures, woodlots and plantations) were measured from a sample of 33 abandoned farmland owners in order to compare and rank the perceptions of abandoned farmland to that of other types of land use. Perceptions of landscape changes and the importance of abandoned farmland within properties were studied. The statistical analyses used allowed us to establish relationships between the different perceptions and the socio-economic characteristics and value indicators of the land owners. The analyses establish that abandoned farmland produces the most negative perceptions, followed by corn fields. Conversely, woodlots are the land use that is the most appreciated. The attitude towards the environment was one of the variables most often significant in explaining the perceptions encountered. Analysis of landscape evolution reveals an intensification of agricultural practices that may lead to the conversion of abandoned farmlands into cultivated land. Finally, abandoned farmland is perceived, at the scale of the individual property, as the land use having the least value (as opposed to corn fields) and being the least appreciated (as opposed to forests).     

Sulfate threshold target to control methylmercury levels in wetland ecosystems

Sulfate contamination has a significant environmental implication through the stimulation of toxic hydrogen sulfide and methylmercury (MeHg) production. High levels of MeHg are a serious problem in many wetland ecosystems worldwide. In the Florida Everglades, it has been demonstrated that increasing MeHg occurrence is due to a sulfate contamination problem. A promising strategy of lowering the MeHg occurrence is to reduce the amount of sulfate entering the ecosystem. High surface water sulfate concentrations in the Everglades are mainly due to discharges from the Everglades Agricultural Area (EAA) canals. Water and total sulfur mass balances indicated that total sulfur released by soil oxidation, Lake Okeechobee and agricultural application were the major sources contributing 49,169, 35,217 and 11,775 mtons year^− 1, respectively. Total sulfur loads from groundwater, levees, and atmospheric deposition contributed to a lesser extent: 4055; 5858 and 4229 mtons year^− 1, respectively. Total sulfur leaving the EAA into Water Conservation Areas (WCAs) through canal discharge was estimated at 116,360 mtons year⁻¹, and total sulfur removed by sugarcane harvest accounted for 23,182 mtons year^− 1. Furthermore, a rise in the mineral content and pH of the EAA soil over time, suggested that the current rates of sulfur application would increase as the buffer capacity of the soil increases. Therefore, a site specific numeric criterion for sulfate of 1 mg L^− 1 was recommended for the protection of the Everglades; above this level, mercury methylation is enhanced. In parallel, sulfide concentrations in the EAA exceeded the 2 μg L^− 1 criterion for surface water already established by the U.S. Environmental Protection Agency (EPA).     

On-farm treatment of dairy soiled water using aerobic woodchip filters

Dairy soiled water (DSW) is produced on dairy farms through the washing-down of milking parlours and holding areas, and is generally applied to land. However, there is a risk of nutrient loss to surface and ground waters from land application. The aim of this study was to use aerobic woodchip filters to remove organic matter, suspended solids (SS) and nutrients from DSW. This novel treatment method would allow the re-use of the final effluent from the woodchip filters to wash down yards, thereby reducing water usage and environmental risks associated with land spreading. Three replicate 100 m² farm-scale woodchip filters, each 1 m deep, were constructed and operated to treat DSW from 300 cows over an 11-month study duration. The filters were loaded at a hydraulic loading rate of 30 L m⁻² d⁻¹, applied in four doses through a network of pipes on the filter surface. Average influent concentrations of chemical oxygen demand (COD), SS and total nitrogen (TN) of 5750 ± 1441 mg L⁻¹, 602 ± 303 mg L⁻¹ and 357 ± 100 mg L⁻¹, respectively, were reduced by 66, 86 and 57% in the filters. Effluent nutrient concentrations remained relatively stable over the study period, indicating the effectiveness of the filter despite increasing and/or fluctuating influent concentrations. Woodchip filters are a low cost, minimal maintenance treatment system, using a renewable resource that can be easily integrated into existing farm infrastructure.     

ENVIRONMENTAL AND STRUCTURAL IMPLICATIONS FOR THE RE-USE OF TYRES IN FLUVIAL AND MARINE-CONSTRUCTION PROJECTS

There is increasing interest in reclaiming tyres for use in bank-side and coastal-protection structures. However, concern has been expressed about the potential for tyres to release pollutants into the environment and to retain their long-term structural stability. This paper describes laboratory leaching tests for heavy metals from new used tyres and tyres which have been exposed to an aquatic environment for thirteen years. The results show that the limiting factor to their use could be cadmium release. Tests found evidence of the loss of ultraviolet screening agents such as carbon black, suggesting that chemical breakdown of the tyre through leaching of vulcanising chemicals is more significant in the physical breakdown of the tyre, than the reverse. Three case studies of tyre flood-protection and river-control structures are presented, which examine the ability of tyres to retain structural integrity over long periods. Based on this evidence, guidance on design principles is offered. It is concluded that tyres can be used sustainably in a river or coastal environment, subject to careful consideration of local site conditions.     

Modelling Cryptosporidium oocysts transport in small ungauged agricultural catchments

Cryptosporidium is an environmentally robust pathogen that has caused severe waterborne disease outbreaks worldwide. The main source of zoonotic Cryptosporidium parvum oocysts in human drinking water is likely to be from farm animals via catchment pathways with water as the main transport vector. The vast majority of small agricultural catchments are ungauged therefore it is difficult to use a process model to predict and understand the mechanisms and activities that regulate the risk of surface water contamination from agricultural areas. For this study, two ungauged agricultural catchments in Ireland were used to model Cryptosporidium oocyst transport using SWAT2005 on a daily basis with reference data from adjacent catchment gauging stations. The results indicated that SWAT2005 could simulate stream flow with good agreement between prediction and observation on a monthly basis (R² from 0.94 to 0.83 and E (efficiency) from 0.92 to 0.66), but Cryptosporidium oocyst concentration results were less reliable (R² from 0.20 to 0.37, P < 0.05; with poor E −0.37 to −2.57). A sensitivity analysis using independent parameter perturbation indicated that temperature was the most important parameter regulating oocyst transport in the study catchments and that the timing of manure application relative to the occurrence of water runoff event was critical. The results also showed that grazing management had little influence on predicted oocyst transport while fields fertilized with manure were the key critical source areas for microbial contaminations in the study catchments. It was concluded that the approach presented could be used to assist with understanding the epidemiology of waterborne cryptosporidiosis outbreaks and to improve catchment management for the safety of the general public health.     

柿竹园矿区及周边农田土壤重金属形态分布与生物有效性研究

为了解柿竹园矿区及周边农田土壤重金属的生物有效性,采用连续提取法对该矿区及周边的农田土壤重金属Cu、Pb、Zn、Cd、As、Hg的形态分布和生物有效性进行了分析。结果表明:(1)柿竹园矿区及周边农田土壤未见Hg污染情况,但不同程度受到Cu、Pb、Zn、Cd、As的污染,尤以Cd、As污染为重;(2)柿竹园矿区及周边农田土壤中Cu、Pb、Zn以铁锰氧化物结合态为主,分别占其总量的48.3%、67.3%、47.1%,Cd铁锰氧化物结合态含量最高,残渣态、离子交换态和碳酸盐结合态次之;As和Hg以残渣态为主,含量比例在90%以上;(3)矿区及周边土壤中Cd的有效态含量最高,所占比例平均值为31.1%,远高于其他5种重金属元素,生物有效性最高,As的有效态含量最低,生物有效性最低。最后提出了采用稳定化修复技术清理污染源、采用磷酸二氢钙降低土壤中污染最严重元素Pb、Cd的生物有效性、采用香蒲等植物对工矿废弃地及部分未利用土地进行修复的建议。