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121.
A meta-analysis of heavy metals pollution in farmland and urban soils in China over the past 20 years 总被引:3,自引:0,他引:3
A total of 713 research papers about field monitor experiments of heavy metals in farmland and urban soils in China, published from 2000 to 2019, were obtained. A meta-analysis was conducted to evaluate the level of China's heavy metal pollution in soils, mainly focusing on eight heavy metals. It was found that the average concentrations of cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), mercury (Hg), chromium (Cr), nickel (Ni), and arsenic (As) in China were 0.19, 30.74, 85.86, 25.81, 0.074, 67.37, 27.77 and 8.89 mg/kg, respectively. Compared with the background value (0.097 mg/kg), the Cd content showed a twofold (0.19 mg/kg) rise in farmland soils and a threefold (0.29 mg/kg) rise in urban soils. The decreasing order of the mean Igeo was Cd (1.77) > Pb (0.62) > Zn (0.60) > Cu (0.58) > Hg (0.57) > Cr (0.54) > Ni (0.47) > As (0.28). Nearly 33.54% and 44.65% of sites in farmland and urban soils were polluted with Cd. The average concentrations of eight heavy metals were not sensitive change in recent two decades in farmland and urban soils. The average Pn values for urban (2.52) and farmland (2.15) soils showed that heavy metal pollution in urban soils was more serious than that in farmland, and the middle Yangtze River regions, where industrial activity dominates, were the most polluted. The meta-analysis comprehensively evaluated the current pollution situation of soil heavy metal, and provided important basis for soil management and environment prevention in China. 相似文献
122.
123.
根据目前污水处理的迫切性和必要性,主要介绍了生态塘处理系统的原理,工程实践中常见的典型工艺流程,工艺特点及优点,并结合山东东营市的污水生态处理工程运行实践,分析了其运行效果、可靠性及经济性。 相似文献
124.
区域开发具有较大的不确定性,并且占地面积大、开发的内容广、性质复杂、建设周期长,通常的区域开发都有可能涉及到工业、城建、商业、人居、市政等多个领域的开发活动,所以区域开发必须结合区域开发的特征,准确识别其可能对区域内及其周边的空气环境、地下水质量、地表水水质及水文条件、声环境、土壤、植被、地形地貌等自然环境和人口、交通、经济结构等社会环境等产生的影响,并采取发展循环经济,减少污染生成的源头控制措施;科学规划产业结构,合理布局的预防性措施;源内达标、区域集中控制的污染治理措施;实施清洁生产、总量控制,推进区域环境与经济的持续发展。 相似文献
125.
126.
Severe drinking water shortage affects all resident of the Kabul river basin. Two and a half decades of civil war in Afghanistan
(it began in late 1978) have resulted in widespread environmental degradation and water resource development throughout the
country. The war has already finished and, therefore, water resource management for supplying water is one of the most important
tasks for Afghanistan’s government. The Kabul river basin which is the most populated area in the country is located in the
eastern part of Afghanistan. This article deals with the water resource properties of the Kabul river basin and also water
demand in the important cities of the basin, such as Kabul, the capital and the largest city in the country. Also a few suggestions
for providing water for domestic and agriculture purposes in short term, medium time and long term have been discussed. 相似文献
127.
Securing sustainable livelihood conditions and reducing the risk of outmigration in savanna ecosystems hosted in the tropical semiarid regions is of fundamental importance for the future of humanity in general. Although precipitation in tropical drylands, or savannas, is generally more significant than one might expect, these regions are subject to considerable rainfall variability which causes frequent periods of water deficiency. This paper addresses the twin problems of “drought and desertification” from a water perspective, focusing on the soil moisture (green water) and plant water uptake deficiencies. It makes a clear distinction between long‐term climate change, meteorological drought, and agricultural droughts and dry spells caused by rainfall variability and land degradation. It then formulates recommendations to better cope with and to build resilience to droughts and dry spells. Coping with desertification requires a new conceptual framework based on green‐blue water resources to identify hydrological opportunities in a sea of constraints. This paper proposes an integrated land/water approach to desertification where ecosystem management supports agricultural development to build social‐ecological resilience to droughts and dry spells. This approach is based on the premise that to combat desertification, focus should shift from reducing trends of land degradation in agricultural systems to water resource management in savannas and to landscape‐wide ecosystem management. 相似文献
128.
Stream restoration practices are becoming increasingly common, but biological assessments of these improvements are still
limited. Rock weirs, a type of constructed riffle, were implemented in the upper Cache River in southern Illinois, USA, in
2001 and 2003–2004 to control channel incision and protect high quality riparian wetlands as part of an extensive watershed-level
restoration. Construction of the rock weirs provided an opportunity to examine biological responses to a common in-stream
restoration technique. We compared macroinvertebrate assemblages on previously constructed rock weirs and newly constructed
weirs to those on snags and scoured clay streambed, the two dominant substrates in the unrestored reaches of the river. We
quantitatively sampled macroinvertebrates on these substrates on seven occasions during 2003 and 2004. Ephemeroptera, Plecoptera,
and Trichoptera (EPT) biomass and aquatic insect biomass were significantly higher on rock weirs than the streambed for most
sample periods. Snags supported intermediate EPT and aquatic insect biomass compared to rock weirs and the streambed. Nonmetric
multidimensional scaling (NMDS) ordinations for 2003 and 2004 revealed distinct assemblage groups for rock weirs, snags, and
the streambed. Analysis of similarity supported visual interpretation of NMDS plots. All pair-wise substrate comparisons differed
significantly, except recently constructed weirs versus older weirs. Results indicate positive responses by macroinvertebrate
assemblages to in-stream restoration in the Cache River. Moreover, these responses were not evident with more common measures
of total density, biomass, and diversity. 相似文献
129.
Membrane based treatment processes are very effective in removing salt from wastewater, but are hindered by calcium scale deposit formation. This study investigates the feasibility of removing calcium from treated sewage wastewater using accelerated seeded precipitation. The rate of calcium removal was measured during bench scale batch mode seeded precipitation experiments at pH 9.5 using various quantities of calcium carbonate as seed material. The results indicate that accelerated seeded precipitation may be a feasible option for the decrease of calcium in reverse osmosis concentrate streams during the desalination of treated sewage wastewater for irrigation purposes, promising decreased incidence of scaling and the option to control the sodium adsorption ratio and nutritional properties of the desalted water. It was found that accelerated seeded precipitation of calcium from treated sewage wastewater was largely ineffective if carried out without pre-treatment of the wastewater. Evidence was presented that suggests that phosphate may be a major interfering substance for the seeded precipitation of calcium from this type of wastewater. A pH adjustment to 9.5 followed by a 1-h equilibration period was found to be an effective pre-treatment for the removal of interferences. Calcium carbonate seed addition at 10 g l−1 to wastewater that had been pre-treated in this way was found to result in calcium precipitation from supersaturated level at 60 mg l−1 to saturated level at 5 mg l−1. Approximately 90% reduction of the calcium level occurred 5 min after seed addition. A further 10% reduction was achieved 30 min after seed addition. 相似文献
130.
Effects of three pesticides on the avoidance behavior of earthworms in laboratory tests performed under temperate and tropical conditions 总被引:2,自引:0,他引:2
Garcia M Römbke J de Brito MT Scheffczyk A 《Environmental pollution (Barking, Essex : 1987)》2008,153(2):450-456
Little research has been performed on the impact of pesticides on earthworms under tropical conditions. Taking into consideration the often-limited resources in tropical countries, simple screening tests are needed. Therefore, it was investigated whether three pesticides relevant for the Brazilian Amazon (benomyl, carbendazim, lambda-cyhalothrin) affect the avoidance behavior of the earthworm Eisenia fetida. The tests were performed for two days according to ISO guideline 17512 but were adapted to tropical conditions (i.e. test substrate, test organism and temperature). The results indicate that this test gives reproducible and reliable results. Toxicity values (NOEC, EC50) are lower than those determined in 14 day-acute mortality tests and are approximately in the same range such as those found in 56 day-chronic reproduction tests with the same earthworm species, which were performed in parallel. Therefore, the use of the earthworm avoidance tests is recommended as a screening tool for the risk assessment of pesticides. 相似文献