Heavy Metal Contaminated Food Crops Irrigated with Wastewater in Peri Urban Areas, Zambia

Studies on peri urban farming in Zambia have not adequately tackled the issues pertaining to heavy metal contaminated wastewater irrigation farming. The study investigated heavy metal contamination of water, soils and crops at two peri urban areas in Zambia. Two study sites were New Farm Extension in Mufulira Town in the Copperbelt Province and Chilumba Gardens in Kafue Town in Lusaka Province. The heavy metals investigated were lead, copper, cobalt, nickel and chromium. These heavy metals were found to be higher than acceptable limits in wastewater used to irrigate crops and there are potential human health risks associated with consumption of heavy metal contaminated food crops which have implications on the livelihoods of people. Samples of water, soil and crops were collected and analysed for lead (Pb), copper (Cu), chromium (Cr), cobalt (Co) and nickel (Ni) using the Atomic Absorption Spectrometer (AAS). The data on heavy metals was analysed using mean, standard error and T-test. The results indicated that the levels of heavy metals in wastewater, soil and food crops were above acceptable limits at two study sites. It can be concluded that there was heavy metal contamination of wastewater, soil and food crops at the two peri-urban areas in Zambia. The study highlighted the actual levels of heavy metal contaminant uptake in food crops consumed by the peri urban population. The information from this study can be used by the relevant authorities to develop appropriate measures for monitoring and control of heavy metal contamination in wastewater irrigation farming systems in peri urban areas inZambia.

Function of Agricultural Land Use and Its Evolvement in Peri-urban Area: A Case Study of Beijing

Rapid urbanization in Beijing stimulates the urban land expansion and diminishes available agricultural land. Monofunctional agricultural land use can not meet the demand of the devel- opment of the multifunctional agriculture and urbanization any more, so multifunctional agricultural land use is going to be promoted in the city. This article proposes the evolvement of the land use change from 1992 to 2004 and discusses some evolvement views.

Study on Environmental-Geological Problem and Ecosystem Re-establishment Countermeasures About Quarry and Damaged Mountain in Peri-urban

The quarry and damaged mountain in peri-urban have an important influence to ecological environment. They have had a series of serious environmental -geological problems to the socio-economic development and urban modernization process, such as increased environmental pollution and soil erosion,destruction of landscape aesthetic。

The Role of Private Water Vending in Nigeian Peri-Urban Informal Settlements: Implication for Policy Makers

This paper presents a study of water vending in 3 informal settlements of Yola North in Adamawa State of Nigeria. These settlements represent the fast growing urban areas often dwelling in unplanned and unsecured tenure. Access to safe water supply has great influence on the health, economic productivity and quality of life of the people. But meeting this need is one of the major challenges facing the urban communities of Nigeria today. A field survey was conducted in the area with 100 observations of households in each of the three informal settlements. These settlements are Sabongari -University village, Vinikilang and Wuro Jabbe. The survey solicited for response concerning household water source, water per capita use and household size. Findings revealed that about 92% of respondent in Sabongari-University village, 66% in Vinikilang and 87% in Wuro Jabbe depend on vended water from borehole, hand dug well as well as surface water sources which are delivered by hand pushed trucks. Owing to the absence of piped water networks in the study area, households are forced to rely on available water sources which are precursor to water borne diseases. It is advocated that the public agencies should evolve special programs for regularizing informal settlements, meaning the legalization of land tenure, layout corrections and service upgrading if service is to meet the poor informal dwellers.

Policy Needs for Social Security in the Process of Citizenization of the Peri-urban Farmers:A Case Study of Hefei City

We conduct a survey of transformational towns and villages in High-tech Development District, Yaohai District and Shushan District, Hefei City. Using data, we analyze the "sideline effect" and inherent contradiction of transformational cities, research the policy needs for social security and its trend in the citizenization process of the peri-urban farmers. On this basis, we construct the social security policy system that can adapt to the accelerated process of urbanization. Finally, we put forth the following recommendations for the social security policy in the citizenization process of the peri-urban farmers: distinguishing different groups' policy needs for social security; attaching importance to people's dynamic policy needs for social security in urbanization; focusing on the adaptability of social security policy transformation in urbanization; attaching importance to the social psychosocial environment of social security policy transformation in urbanization; achieving the trinity of non-farm conversion, urbanization and citizenization in the process of urbanization; strengthening the government's dominant position in the building of social security policy system.

Natural Regeneration of Marker Species of the Tropical Dense Humid Ecosystems in the Loukaya Peri-Urban Forest, Brazzaville-Congo

The study aimed at evaluating the natural regeneration of some characteristic species in the Loukaya peri-urban forest was carried out in Brazzaville, over three surveys of one hectare each. The botanical inventory of the 23 species monitored covers the subjects of 2 ≤ d0.20 < 10 cm and d1.30 ≥ 10 cm. The study shows 1255 individuals of which 68.27% are 2 ≤ d0.20 < 10 cm. While being tropophilic and mesophilic, this ecosystem is pauciflorous and paucispecific. The phytoecological data show that this formation, which is a link in the African dense humid forest, presents values far below those known elsewhere;while being faithful to the forests of the Cataractes Plateau. As for the rate of natural regeneration, this index is greater than or equal to 100 for 69.56% of the taxa. Sarcochores and heliophytes are the taxa that best support this natural regeneration. This high rate of regeneration would be correlated with the high level of anthropization, whose large canopy gaps are accompanied by a flow of light conducive to the installation of seedlings.

Analysis of the Trend of Peri-Urban Development in Minna, Niger State

Current situation of development in Minna has raised many spatial challenges especially in the peri-urban areas. This study analyzed the spatial development of Minna between 1972 and 2015, with a view to determining the trend at which the peri-urban area changes over time. Minna topographical map of 1972, township map of 1979 and the satellite imageries covering 1986, 1996, 2006 and 2015 were employed in this study. Map processing and image classification techniques were used in extracting the information needed. The study revealed that there was over 2000% increase in the built-up area of Minna within the period understudied. This implies that the peri-urban areas of Minna by 2015 had grown about thirty-two times its size in 1972;thirteen its size in 1979;thrice its size in 1986 and 1996, respectively;and twice of its size in 2006, but, with an increased rate of uncoordinated and unplanned development. It concluded that the planning and development of Minna peri-urban areas should not be left to chance or the interplay of economic variables, but should be guided by strategies that will ensure orderly growth and development. It therefore recommended that the government through the statutory agencies should initiate a strategic development plan proposal known as Peri-urban Area Strategic Development Plans (PuASDP), which is to guide and control every spatial development activities in the peri-urban areas.

Assessing Localized Contamination Hazard and Groundwater Quality Challenges in Water-Stressed Peri-Urban Accra, Ghana

The study assesses the quality of hand dug wells in relation to distance from soakaway septic tanks in three selected peri-urban communities in the Ga West Municipality near Accra, Ghana. Water quality analyses of bio-physico-chemical variables (pH, Temperature, EC, turbidity, DO, BOD, TSS, TDS, sodium, potassium, nitrate, nitrite, ammonia, sulphate, chloride, salinity, total alkalinity, total coliform, fecal coliforms and isolation of E. coli) were determined. Concentrations of the major nutrient anion sulphate, nitrate, phosphate, and chlorides in water samples at distances between 0 - 30 m radial distances from the septic tank were above the WHO permissible limit of drinking water compared to the control. All the water samples had high fecal and total coliform counts that exceeded the international standard of 0 per 100 mL of potable water with counts ranging from 0 - 143 cfu/100 ml and 53 - 463/100 ml for FC and TC respectively. High fecal coliform and detection of E. coli in most samples is an indication of fecal pollution possibly from their close proximity to soak away septic sewage. The high nutrient levels detected in samples at distances between 0 - 30 m as compared to the controls may also be attributed to its close proximity to septic tanks. This study, therefore, accentuates the need for the owners of the water points to site their water source at least 30m away from localized sources of pollution as well as treatment of groundwater before use.

Drivers of Innovative Urban and Peri-Urban Agriculture in Bamenda City, Cameroon

Urban and peri-urban agriculture (UPA) is gaining increasing importance in developing countries, due to rapid urbanization and rising rural-to-urban migration which has led to an increase in the population of the urban poor in Cameroon. It has been estimated that at least 70% of the total population of Cameroon will be living in urban areas by 2060. Urban and peri-urban agriculture (UPA) has become an important source of livelihood and survival, especially amongst the urban poor but is not adequately recognized and supported by the government of Cameroon and organizations. Recent innovations in UPA have created new opportunities for social, economic, and environmental sustainability of urban areas, hence possible policy formulation in UPA. Therefore, this study was conducted with the main objective of determining the drivers of innovative urban and peri-urban agriculture in Bamenda City, Cameroon. Methodologically, the study employed probit model, using primary data collected from a sample of 402 UPA farmers through the cluster, simple random, and snowball sampling techniques. The results revealed that access to extension services is a major driver of innovative UPA in Bamenda City and is statistically significant at 1%. Other factors such as employment status (full time), age group (26 to 50 years), and gender, were also seen to have a significant positive influence on innovative UPA while the level of education (secondary) had a negative influence on innovative UPA and was statistically significant at 5%. Limited capital, limited knowledge, and financial constraints were identified as the major challenges hindering the practice of innovative urban and peri-urban agriculture in Bamenda City. The study recommends that the government and non-governmental organizations should increase the quality and quantity of extension service delivery to urban and peri-urban farmers, and more recognition and support should be offered to them to help overcome the challenges faced.

The Experience of Industrial Districts Construction in Yokohama City-A Useful Reference for Shanghai Urban Planning

Shanghai and Yokohama are very similar in the positions in their respective state economy and in the orbit of eco-nomic structure development. Since industrial districts in Yokohama city were established dozens years earlier than Shanghai, the experience of Yokohama must be very useful for Shanghai urban planning.

成都市半城市化地区的特征、驱动机制及规划启示

半城市化地区作为一种在景观格局、社会构成和空间形态等方面发生深刻转变的过渡性地域类型,在不同发展战略引导下,其未来发展可能会出现保持现状、持续发展或依赖陷阱等截然不同的结果。特大城市郊区半城市化地域的发展关系到国家经济发展、社会稳定和人居环境改善,对其进行主动干预和精明管治势在必行。文章以成都市为例,研究半城市化发展的时空格局及其特征演变的规律性,在此基础上从交通基础设施和产业园区建设以及城乡接合部的自发发展3个方面解析成都市半城市化发展的驱动机制,基于成都市环城生态区规划实施与城乡统筹规划的创新做法,进一步探讨半城市化地区如何通过规划介入成为一个可持续的发展区域。

场景营造与城市近郊特色小镇建设

场景营造对创造人地共生所需的文化空间具有形塑作用,是统合文化生产与消费、激活多方主体参与、实现乡村振兴的内在动力机制。特色小镇是当代中国城镇化的一种发展模式,既是打通新型城镇化和乡村振兴两大战略的空间支撑节点,也是城乡融合发展的重要载体,同时还是文旅融合赋能乡村振兴战略的承接地。场景理论的应用,推动着特色小镇的建设从以空间扩张为特征的第一阶段向以文化内涵建设为特征的第二阶段演进。城市近郊特色小镇作为一种特色鲜明、要素集聚、宜居宜业、富有活力的文化空间,与城市的经济文化社会发展存在诸多协同。在推动“城市群——都市圈——中心城市——大中小城市协同发展——特色小镇——乡村振兴”统筹发展的新型城镇化总体战略高质量落地的过程中,以场景营造推动城市近郊特色小镇建设中主体价值的重点突出,避免特色小镇的价值分散与符号游离,重视与城市主体文化生态的协同,强化空间规划和错位发展,围绕特色符号构建产业价值链,是调整城乡产业空间布局、探索建设美丽中国、实现乡村振兴的新的理论解释和实践路径。

长三角典型城郊流域溶解性有机质的分子特征:以浙江樟溪为例

溶解性有机质(DOM)在流域水环境中广泛存在,参与各种生物地球化学循环过程。快速的城镇化过程和人类活动显著改变了流域水体DOM含量和特性,从分子层面上解析DOM在流域尺度上的时空分异特征对流域水质管控具有重要的理论和应用价值。以长三角地区樟溪流域为研究对象,依据土地利用和人类活动强度布设采样点,于2022年7月采集水样。结果表明,樟溪流域水体溶解性有机物主要的分子式元素组成为CHO、CHON、CHOS,其中木质素/富羧酸脂环分子类有机物相对占比最高。在子流域空间分布上,人类活动强的子流域CHON、CHONS类型化合物含量更高。选取采样点距城镇距离、距源头距离以及土地利用类型所占采样点缓冲区的比例来表征人类活动的影响。结果表明,流域内DOM杂原子受人类活动强度影响,距源头的距离与水体DOM分子中氮原子的强度加权平均值(N wa)和CHON化合物百分呈显著正相关,与碳、氢原子和荷质比的强度加权平均值(C wa、H wa、m/z wa)呈显著负相关。CHON分子的相对丰度与林地面积比例呈显著负相关,与农业用地比例呈显著正相关。比较具有典型土地利用类型的水体DOM:典型农田、城镇土地利用类型DOM含有更多独特的CHON分子式,农田DOM在木质素/富羧酸脂环分子区域出现CHON分子式的富集,城镇DOM在脂肪类和木质素/富羧酸脂环分子区域均出现了CHON分子式富集。研究表明在城郊流域中,人类活动显著改变了水体DOM的分子特征,增加了分子多样性,促进了特定分子式的富集。

关中近郊乡村宅院民居空间功能置换设计策略

随着我国城乡一体化发展理念的提出,以农耕产业为主导的乡村经济模式正在发生变革,其中近郊乡村农户的生计转型最为明显。目前大量的宅院民居需要在自主更新建设中对既有空间进行功能置换,以适应新的需求。综上,以关中地区为例,探究基于农户生计类型划分的宅院空间功能使用现状,并以院落、主体用房、附属用房作为宅院空间的构成要素构建“多类型、多层级”的功能置换设计策略,以期为关中近郊乡村的高质量更新提供依据。

海湾型城市半城市化地区空间扩展演化——以厦门市为例

选择海湾型城市——厦门市半城市化地区为研究对象,基于研究区1987、1992、1997、2002和2007年5个时相的TM/ETM+遥感影像数据,在遥感与GIS技术支持下获取了近20a来各期土地利用信息数据,采用景观格局转移矩阵、景观格局指数和分形理论等方法研究了厦门市半城市化地区城市化过程中的景观格局空间演变特征,详细分析了城市形态演变、城市围填海特征及政策影响。结果表明:20a年来厦门近郊建设用地从18.4km2增加到108.4km2,远郊则从35.7km2增加到114.9km2,分别增长为原来5.9倍和3.2倍;城市空间扩展过程通过不断侵蚀耕地、林地和大规模填海造地完成,其中耕地景观变化最大,城市扩展最高峰(2002～2007年)近郊与远郊被建设用地"蚕食"的耕地多达19.74km2和33.11km2;在城市空间不断扩展的过程中,近郊城市城市由不稳定形态逐步向稳定形态(填充增长)演化,但远郊形态格局尚处于以中心城市扩展为主体的时期;填海造地面积及其时空分布与政策因素密切相关,20a来厦门半城市化地区海岸线缩短了14.3%,近郊与远郊海岸分维数分别从1.236和1.267降到1.191和1.262,岸线复杂性明显降低,逐步趋于平直;海湾型城市战略的提出对填海造地影响最为明显,2002～2007年期间填海进程明显加快,近郊与远郊分别填海13.32和9.15km2,超越了前15a填海总面积。

中国半城市化现象及其研究重点

1978年改革开放以来,受外国资本涌入、大都市辐射与扩散、乡村工业化等的推动及城乡二元管理体制的阻碍等多因素的复合作用,在我国部分区位、禀赋条件较好的农村地区,普遍发育和形成了一种城乡土地利用混杂交错、社会经济结构急剧变化、“似城非城”的过渡性地域类型,即半城市化地区。在广泛地评析国内外相关进展的基础上,重点辨析了城市边缘区、边缘城市、都市扩展区、Desakota、城乡一体化等5种具有理论借鉴意义的概念及其与我国半城市化现象的异同,进一步阐述了开展我国半城市化研究的重要意义及其研究重点。

长江三角洲城乡交错区农业土壤pH特征及影响因素探讨——以江苏省无锡市为例

城乡交错区经济的迅速发展对土壤pH产生了明显的影响。以无锡市某城乡交错区为例,研究了土壤pH的时空变异及与土壤性质的关系,探讨了影响土壤pH变化的主要因素。结果显示,该区土壤pH变化较大(3.74～8.50),土壤酸度由交换性H+、Al3+共同决定,蔬菜地土壤由于交换性H+和Al3+的出现降低了盐基总量和盐基饱和度,导致pH降低。稻田改种蔬菜后,土壤明显酸化,pH均值从6.43降至5.40;工企业周围土壤pH也明显降低;相反,在城镇周围及公路两侧土壤pH则明显较高。综合分析表明,该地区土壤pH的变化受农业活动影响较大,包括土地利用的变化,持续的强烈利用和大量施用无机化肥等;另外,工业活动也使得企业周围土壤pH明显降低;其次,公路和城镇建设带入的碱性物质使土壤pH增加,建议增加有机肥施用及水旱轮作进行改良。

工业型城乡交错区农业土壤Cu、Zn、Pb和Cd的空间分布及影响因素研究

在江苏省无锡市工业型城乡交错区,选择8 km2区域,采集119个土壤样品,对土壤Cu、Zn、Pb、Cd及其有效态含量的空间分布和影响因素进行探讨。结果表明:该区土壤Cu、Zn、Pb、Cd含量和变异系数都明显增加,土壤有效态重金属含量与相应的全量重金属含量具有显著相关性。土壤Cu、Zn、Cd空间变异主要受到工业影响,但由于该区工业类型的多样性和工厂分布的分散性,Cu、Zn、Cd空间分布模式并不相同。本区土壤Pb的分布与工厂分布的相关性不大,但随与城市距离增加而降低。公路和土地利用与土壤重金属含量的关系表现不明显。该区工业污染对土壤重金属空间变异的影响可能掩盖了公路和土地利用等的影响,建议在城乡交错区合理安排工业布局以控制土壤受重金属污染的范围。

工业型城乡交错区农业土壤Zn的空间分异及其影响因子探讨──以无锡市为例

城乡交错区的工业发展可能导致土壤重金属积累,并威胁食品安全。本文以无锡典型工业型城乡交错区为例,利用地统计学变异函数研究了农业土壤全量Zn和DTPA-Zn的空间变异特征,并分析了其影响因素。结果表明:人类活动明显增加了土壤的含Zn量,研究区土壤全量Zn具有强烈的空间自相关性,其空间变异主要与工业活动有关,土地利用对它没有影响;土壤全量Zn在工厂分布区附近较高,其他地区较低。土壤DTPA-Zn变异性大于全量Zn,具有中等的空间自相关性,其空间变异与工厂无明显关系,但土地利用对它影响较大,菜地DTPA-Zn含量明显高于水稻田。

南通市城市边缘带土壤重金属污染现状及评价

通过对不同土地利用方式下的7个样区进行系统的采样测定,对南通城市边缘带土壤重金属富集与污染状况进行了分析与评价。结果显示,研究区土壤未发生明显的重金属污染。但3个样区的土壤有轻度的重金属污染现象,Zn是发生富集最普遍的元素,约76%的样点土壤Zn富集指数>1,18%的样点土壤出现Zn的轻度污染。Cu、Pb等重金属元素导致的污染也在零星样点被发现。方差分析表明,土地利用方式不是导致研究区土壤重金属含量空间差异的主要因素,而土壤类型、样区空间环境与土壤重金属含量及富集、污染有相对密切的关系。