Utilization of recycled solid waste as ecological reclamation materials based on plant growth experiments and soil quality analysis

During the highway construction,a large number of spoil areas will be generated while a large amount of waste slag and soil could not be rationally utilized.Besides,the vegetation recovery is slow in the spoil areas due to the soil depletion.Aiming at recycling the solid waste,the sieved engineering waste slag with local red clay and corn straw biochar was supplied to solve the problem of insufficient nutrients in engineering waste slag and soil.In addition,planting experiments of alfalfa(Medicago sativa L.)and Amorpha fruticosa L.combined with physical and chemical experiments were carried out to prove the feasibility of the novel improved substrate for the reclamation of spoil areas.The results show that the substrate's improvement effect is mainly affected by the soil to slag ratio and the biochar content.The improvement effect of soil matrix in highway spoil area decreases with the increase of the waste slag content,especially when the soil-slag ratio is less than 3,and the promotion of plants is limited.On the contrary,the improvement effect is proportional to the biochar content(3%-8%).But it is noted that the Cu and Pb in the soil will exceed the clean limit corresponding to the Nemero soil pollution index level when the biochar content is 8%.Therefore,it is recommended that the soil-slag ratio should be≥3,and the biochar content should reach 3%-5%.This research provides experimental basis and technical support for utilizing solid waste resources in the reclamation of highway spoil areas.

Reclamation of CO_(2) sodium silicate used sands by steam leaching

The bond film on the surface of the CO_(2) sodium silicate used sands is not easy to decompose,therefore,it is difficult to reclaim used sands.A new reclamation method of CO_(2) sodium silicate used sands was developed by steam leaching,which can reduce the water consumption of reclamation and improve the removal effect of sodium silicate bond film.Firstly,the leaching effect of the sodium silicate sands after 20/200/400/600/800/1,000°C heat preservation treatment was simulated.Furthermore,the influence of the leaching time on the removal effect of the sodium silicate bond film was studied.Finally,the casting properties of the reclaimed sands after the leaching reclamation treatment were tested.The results show for simulated used sands after 30 min of steam leaching,the removal ratio of the alkali exceeds 84.1%,the removal ratio of silicate is 86.2%,and the removal ratio of carbonate is 93.6%.The removal rate of alkali,silicate and carbonate is relatively low in the leaching time of 30-50 min.Considering the reclamation effect and cost,the leaching time is controlled in 30 min.Water consumption is only 60%of the mass of used sands for 30 min steam leaching,while it is 200%for wet reclamation.Morphological analysis shows that most of the hazardous substances in the used sands are removed in 30 min steam leaching,and the reclaimed sands surface after steam leaching in 50 min is as smooth as new sands.After 30 min of steam leaching,the alkali removal effect of the factory used sands can reach 81.5%,the water consumption by the steam leaching reclamation is 58%of the mass of the used sand,which is similar to the result of simulated used sands.The performance of reclaimed sands obtained after 30 min steam leaching is better than that of new sands when the amount of sodium silicate added is 6%of the mass of the reclaimed sands and the CO_(2) blowing time is 15 s:the 24 h ultimate compressive strength of reclaimed sands is 5.6 MPa(equated with new sands),and the collapsibility compressive strength is 5.2 MPa,which is lower than the collapsibility compressive strength of new sands(7.7 MPa).This indicates that the reclamation of CO_(2) sodium silicate used sands by steam leaching is a feasible method.

Impact of estuarine reclamation projects on saltwater intrusion and freshwater resource

Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been implemented in the Changjiang River estuary in recent years:the Xincun Shoal reclamation project(RP-XCS),the Qingcao Shoal reclamation project(RP-QCS),the Eastern Hengsha Shoal reclamation project(RP-EHS),and the Nanhui Shoal reclamation project(RP-NHS).The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model.Results show that for a multichannel estuary,local reclamation projects change the local topography and water diversion ratio(WDR)between channels and influence water and salt transport and freshwater utilization in the estuary.During spring tide,under the cumulative effect of the four reclamation projects,the salinity decreases by approximately 0.5in the upper reaches of the North Branch and increases by 0.5-1.0 in the middle and lower reaches of the North Branch.In the North Channel,the salinity decreases by approximately 0.5.In the North Passage,the salinity increases by 0.5-1.0.In the South Passage,the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2-0.5 on the north side of the middle and lower reaches.During neap tide,the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide,but there are some differences.The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail.The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.

Coastline changes and tidal current responses due to the large-scale reclamations in the Bohai Bay

China’s Bohai Bay has experienced large-scale land reclamation since 2000.These reclamation projects create a nearshore ecological imbalance and shift sediment transport by changing the tidal current.However,these tidal current changes are not comprehensively understood.In this paper,the coastline changes in Bohai Bay due to reclamation are investigated and the responses of the tidal current are calculated through numerical methods.The results show that the coastline length of the bay increases by more than 500 km from 2000 to 2015 with the largest reclamation rate of 150.9 km^(2)/a.Consequently,the current velocity changes with an uneven distribution near the reclamation due to construction masking and dike protrusion.The tidal symmetry also changes in most nearshore areas,with opposite variations in the current velocity at peak flood and ebb tide.In addition,the tide direction deflects to bypass the reclamation and is usually consistent with the coastline.Harmonic analysis of the dominant M2 tidal constituent shows that the range of the reciprocating current is widely extended.The total influence of the reclamation can reach the-8-m isobaths in Bohai Bay.Changes in the tidal current are the main causes of water environment deterioration.Therefore,the arrangement and structural optimization of reclamation projects should be considered in the future.

GIS-Based Assessment of Soil Chemical and Physical Properties as a Basis for Land Reclamation in Toshka Area, Aswan, EGYPT

The accurate assessment of soil properties is a crucial factor for composing and implementing reclamation plans. The main objective of this study was to evaluate soil chemical and physical properties and calculate the chemical and fertility index for assisting land reclamation in Toshka area. The Toshka area is located between latitudes 31°32'N and 31°36'N and longitudes 32°40'E and 32°60'E. GIS was used to select 16 sites. The results revealed the soil has undesirable characteristics. The soil pH ranged from slightly alkaline to moderately alkaline. Furthermore, it was characterized as saline (with a ECe of 4.65 - 11.45 dS⋅m−1) and moderately calcareous soil (with CaCO3 at 11.85% - 17.20%). The soil had a low soil organic matter content which did not exceed 0.18%. The soil was dominated by a sandy loam texture (62.50%) followed by a sandy clay loam texture (18.75%). The bulk density, total soil porosity and saturated hydraulic conductivity values varied with 1.38 - 1.55 Mg⋅cm−3, 41.85% - 48.45% and 1.20 - 3.34 cm⋅h−1, respectively. The chemical index ranged from low to moderate quality. The correlations between the parameters osculated between negative and positive. Therefore, the soil may be reclaimed if the soil properties are improved and crop selection is optimized for this soil.

Feasible Rate of Tidal Flat Reclamation——Jiangsu Mud Coast as a Case Study

Reclamation of tidal flat is one of the main ways to get a dynamic balance of the total amount of plowland. With the development of social economy and the increasing demand for plowland, the contradiction between tidal flat reclamation and environment protection becomes more and more outstanding. However, tidal flat reclamation should also follow the dynamic balance of total amount of tidal flat amount. The paper analyzed the history of reclamation and development of Jiangsu mud coast, and calculated the feasible rates of tidal flat reclamation on different stretches respectively, and pointed out that both the economic social benefits of reclamation and the natural erosion-accretion conditions of the coasts should be taken into consideration in deciding the intensity of tidal flat reclamation, so as to satisfy demands on both reclamation and protection of tidal flat resource.

A study of impact of the reclamation and artificial island projects on tidal currents and sediment concentration in radial sand ridge field of the South Yellow Sea

The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observations. Then the variations of tidal currents and suspended sediment concentration caused by reclamation and artificial islands projects are simulated. The results show that the impacts are limited around the project areas. After the projects, the fan-shaped, Jianggang centered tidal current pattern would be replaced by a pattern which is formed by two tidal paths. One locates at the Xiyang channel in north-south direction, and the other locates at the Huangshayang channel in east-west direction. The reclamation of Tiaozini separates the waters into south portion and north portion. The changes of sediment concentrations coincide with those of currents. Both the sediment concentrations and tidal currents increase at the northwest of Dongsha and the south of Gaoni, while both decrease at the north and south of Tiaozini, and the east and southwest of Dongsha.

Determination of the Thickness and Medium of Covering Soil for Land Reclamation

Land reclamation is a process of ecosystem reconstruction, for which it is very important to keep co-adaptation between plants and the below ground habitat. In order to keep the co-adaptation among plant species, thickness of covering soil and medium of covering soil to establish a self-regulating ecosystem, the thickness of covering soil of land reclamation for plants in different living forms by synusia structure of plant below-ground habitat and medium of covering soil by ecological factors of plant below-ground habitat were studied. Synusia structure of plant below-ground habitat was recognized through investigation on structure and root of plant community, and ecological factors were determined through soil profile investigation. The thickness and medium of covering soil of land reclamation for the tree, the shrub and the herb were proposed.

Evaluation Study on the Reclamation Suitability of Occupied Land in the Coal Mine Area——Taking Gouchang Coal Mine in Nayong County of Guizhou as An Example

The suitability evaluation of reclamation land was the premise and foundation for drawing up the land reclamation program.Taking Gouchang coal mine in Nayong County of Guizhou as an example,combining with the actual situation which included the topography,the soil in the mine area and so on,the reclamation land in the mine area was divided into the living area,the production area,the coal yard,the temporary coal gangue yard and other subsidiary facilities district.It determined that the main destruction type in every unit was the occupation,and the destruction degree was severe.Meanwhile referring the suitability evaluation standards of cultivated field and woodland,it finally determined that the reclamation direction of evaluation land which was damaged seriously by the occupation in the mine area was all suitable to the cultivated field and woodland.

ExperimentonPerformanceofLow-TemperatureExhaustSteamReclamation

针对不同的喉嘴距、面积比，实验研究了不同的进水压力、进水温度和出水压力对低温乏汽回收利用装置性能的影响规律．发现在进水压力为0．14～O．50MPa、进水温度为23～60℃、出水压力为0．096-0．110MPa，以及4种喉嘴距、3种面积比的实验条件范围内，随着喉嘴距和面积比的增加，加热温升和流量比先增大后减小，得到最佳归一化喉嘴距L=4．50，以及最佳面积比m=6．25，使得加热温升和流量比最大．同时，加热温升和流量比均随着进水压力和进水温度的增加而减小，当出水压力升高时，装置性能变差，加热温升和流量比均减小．

Quantitative Simulation of Dynamic Changes in Cultivated Land in Areas of Reclamation and Returning Cultivated Land to Forest or Pastures under RCPs Climate Scenarios

Northeast China as one of important agricultural production bases is an area under reclamation and returning cultivated land to forests or pastures. Therefore, it is of great practical significance in guaranteeing the sustainable development and national food security to study the spatial and temporal variation of cultivated land in Northeast China under future climate scenarios. In this study, based on data of land use, natural environment and social-economy, dynamics of land system（DLS） model was used to to simulate the spatial distribution and changing trends of cultivated land in the typical areas of reclamation and returning cultivated land to forest or pastures in Northeast China during 2010-2030 under land use planning scenario and representative concentration pathways（RCPs） scenarios quantitatively.The results showed that the area of cultivated land had an overall decreasing trend under the land use planning scenario, but the area of upland field increased slightly from 2000 to 2010 and then declined greatly, while the area of paddy field continuously declined from 2000 to 2030. Under the Asia-Pacific Integrated model（AIM）scenario, the total area of cultivated land had a tendency to increase considerably,with the upland field expanding more obviously and the paddy field declining slightly.In addition, the cultivated land showed a greater decreasing trend under the model for energy supply strategy alternatives and their general environmental impact（MESSAGE） scenario compared to the land use planning scenario. Moreover, analysis on the conversion between different land use types indicated that the reclamation and returning cultivated land to forests or pastures was likely to continue under future scenarios, but the frequency of occurrence could decrease as the time goes by. The conclusions can provide significant decision-making information for the rational agricultural planning and cultivated land protection in Northeast China to adapt to the climate change.

Zoning of land reclamation in coal mining area and new progresses for the past 10 years

Coal mining disturbed land is the main sources of land reclamation in China.With the rapid increase of economy and coal production,more and more land has been disturbed by construction and coal mining;thus,land reclamation has become highlights in the past 10 years,and China is boosting land reclamation in mining areas.Disturbance characteristics vary from region to region,according to natural and geological conditions,coal mining area land reclamation was divided into 3 zones,which are eastern,western and southern.Reclamation strategies are focused on prime farmland protection in eastern and ecological restoration in western and southern zones,respectively.Several innovative reclamation technologies and theories for the past 10 years were introduced in this paper,including concurrent mining and reclamation,Yellow river sediments backfilling,self-reclamation,and topsoil alternatives in opencast mines.Besides,in the government regulation and legal system building respect,several important laws and regulations were issued and implemented in the past 5 years,promoting land reclamation management and supervision greatly.Land reclamation is and will still be one of the most important parts of coal industry in the future,and more efforts and funds are expected to get involved.

Suitability evaluation for land reclamation in mining area:A case study of Gaoqiao bauxite mine

Suitability evaluation plays an important role in land reclamation because the choice of evaluation methods affects the accuracy and objectivity of the suitability evaluation results. Furthermore, it influences the decision-making related to land reclamation. An improved method, which is called limit comprehensive conditions method, was developed after different suitability evaluation methods were studied. Based on this method, the reclaimed land of the Gaoqiao bauxite mining area was evaluated. The Gaoqiao mining area was divided into seven evaluation units that were evaluated respectively by selecting evaluation factors and establishing grade standards. The results show that the proposed method is more applicable and easier to handle. Moreover, its evaluation results are more scientific compared with the traditional evaluation methods. The improved method can be beneficial to the rapid monitoring and the effective management of reclaimed land in the opencast mine area.

Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe Salt-Affected Soils

Reclamation of salt-affected land plays an important role in mitigating the pressure of agricultural land due to competition with industry and construction in China. Drip irrigation was found to be an effective method to reclaim salt-affected land. In order to improve the effect of reclamation and sustainability of salt-affected land production, a field experiment （with reclaimed 1-3 yr fields） was carried out to investigate changes in soil physical, chemical, and biological properties during the process of reclamation with cropping maize and drip irrigation. Results showed that soil bulk density in 0-20 cm soil layer decreased from 1.71 g·cm-3 in unreclaimed land to 1.44 g ·cm^-3 in reclaimed 3 yr fields, and saturated soil water content of 0-10 cm layer increased correspondingly from 20.3 to 30.2%. Both soil salinity and pH value in 0-40 cm soil layer dropped markedly after reclaiming 3 yr. Soil organic matter content reduced, while total nitrogen, total phosphorus, and total potassium all tended to increase after cropping and drip irrigation. The quantities of bacteria, actinomycete, and fungi in 0-40 cm soil layer all greatly increased with increase of reclaimed years, and they tended to distribute homogeneously in 0-40 cm soil profile. The urease activity and alkaline phosphatase activity in 0-40 cm soil layers were also enhanced, but the sucrase activity was not greatly changed. These results indicated that after crop cultivation and drip irrigation, soil physical environment and nutrients status were both improved. This was benefit for microorganism＇s activity and plant＇s growth.

The impact of coastal reclamation on tidal and storm surge level in Sanmen Bay, China

In recent years,fast economic development demands for more land use and thus many reclamation projects are initiated around the Sanmen Bay,Zhejiang,SE China in the East China Sea,for which tidal and storm surge levels are reassessed.A two-dimensional numerical model based on an advanced circulation model(ADCIRC)was applied to evaluate the impact of reclamation projects on tidal and storm surge levels in the bay.The results show that the shoreline relocation and topographic change had opposite effects on tidal heights.Shoreline relocation decreased the tidal amplitude,while siltation caused topographic change and increased the amplitude.Such variations of the amplitude were significant in the top areas of Sanmen Bay.Three types of typhoon paths were selected for a case study to investigate the impacts of shoreline relocation and topographic change on storm surge level.Results show that the maximum increase in storm surge level due to shoreline relocation was less than 0.06 m.The rise of peak surge level due to the change of topography was significant and the peak surge level rose when siltation increased.The maximum surge level rise occurred in the path of northwest landing typhoons,which exceeded 0.24 m at the top of the bay.The rise in peak surge level can potentially lead to severe damages and losses in Sanmen Bay and more attention needs to be paid to this problem of shoreline change in the future.

A Model for Environmental Impact Assessment of Land Reclamation

Land reclamation is a complex marine environmental engineering and has a huge impact on social, economic, and physical environment. Reclamation environmental impact assessment （REIA） is also a complicated project, including the assessment of social economic background, ocean engineering, coastal geomorphology, sediment transportation, marine hydrodynamics and marine ecosystem and so on. Nowadays, a large number of land reclaimed projects have been carried out or in the process of construction along the coastal zone, thus, it is necessary to build up a fnmlework on REIA to evaluate and quantify the environmental changes, to contribute to reclamation program, to reduce marine environmental disasters, and to sustain development of coastal zone. This article focuses on the research of REIA framework theory and puts forward a REIA model on land reclaimed evaluation, at the same time, applies this assessment system in Shenzhen City, which is a highly developed coastal city with an expectation of land reclamation. By use of the Remote Sensing （RS） and Geographic Information System （GIS） techniques, along with the topographic map and in situ survey in recla- mation area, it concludes that the area of 2680 hectares in total has been reclaimed in Shenzhen city by the end of the year 2000. Thus, reclamation is usually applied to meet the needs for infrastructure, such as harbors, industries and highways in Shenzhen City. However, some serious negative impacts have been created to the coastal environment shown clearly in the following aspects. Firstly, it caused the dramatic changes of tidal flat and channels along the western coast, made this area more unstable, which is threatening the function of the harbor in this area. Secondly, Tidal prism has decreased rapidly. During the 20 years of reclamation, the tidal prism has been reduced by 20% - 30% along the western coast in the Lingdingyang Estuary, and 15.6% in the Shenzhen Bay. As a result, the velocity of the tidal current has also declined, and the direction of the tidal current has changed, which is harmfid to the dilution and diffusion process of the contaminants. Thirdly, it has threatened the eco-environment finally. More than 147 hectares of mangrove area along the coast of Shenzhen Bay, accounting for 48.8% of the total mangrove reserve area in this region, has been reclaimed only during the short period from 1988 to 2000. Thus, the biodiversity is decreasing, and more and more plants and animals are disappearing. Based on the above analyses of the environmental impacts, strategies and suggestions for the future reclamation in this area have been put forward in order to support the sustainable development of the coastal zone.

Ecological rebuilding and land reclamation in surface mines in Shanxi Province, China

It is well known that the mining industry produces a large amount of derelict land, and causes pollution of water loss and soil erosion as well as other environmental damage in China. As land is under pressure in China, it is now policy to restore or reclaim land despoiled by mining, the aim being to develop sustainable and healthy arable land ecosystems. This paper outlines the principles and approaches of ecological restoration, which have been adopted in Shanxi Province with reference to three typical surface mines. In the research, the principles of ecological engineering and ecological succession are considered as the critical theories of ecological restoration in mine degraded land. Meanwhile, the paper made a comparative research on main links of ecological rebuilding in three surface mines in Shanxi Province, which include new land construction, treatment of toxic substances, control of soil erosion, fertility management, irrigation, ecological planning and the establishment of legislation systems. As the research demonstrated, for successful restoration, new land construction is the fundamental framework, but it must be integrated with ecological engineering including ecological planning, the control of soil erosion and vegetation establishment and ecosystem creation in order to optimise land productivity and soil fertility. In addition, the establishment of the legislation systems and organization of administration are also indispensable aspects of ecological rebuilding in mined land.

Analysis of Jiangsu Tidal Flats Reclamation from 1974 to 2012 Using Remote Sensing

Jiangsu has the most abundant tidal flat resources among China＇s coastal provinces. To ease the conflict between the growing population and shrinking usable land and to promote regional sustainable development, large-scale coastal reclamation development activities have been performed in Jiangsu Province since 1949. The present study has integrated multi-source remote sensing images during 1974 to 2012 by using a Multi-point Fast Marching Method （MFMM） to extract the Jiangsu coastal reclamation areas for different time periods. The temporal and spatial patterns of the extent and elevation of the reclamation areas were analysed in order to determine the unused potential for future reclamation. It will provide information necessary to support the development and construction of tidal flats in Jiangsu. Results show that： （1） the reclaimed tidal fiats along the Jiangsu coast cover more than 19.86×10^4 hm^2, of which 13.97×10^4 hm^2 is located in Yancheng, 4.84×10^4 hm^2 in Nantong, and 1.05×10^4 hm^2 in Lianyungang; （2） the average elevation of the reclaimed Jiangsu tidal flats has gradually decreased over the last 40 years, while those in Dongtai and Rudong have showed particularly accelerated decrease since the 1990s; and （3） in 2012, very few unused tidal flats two meters above the sea level are left along the Jiangsu coast, and mainly concentrated in Yancheng. As there are still reserving some coastal land resources between 0-2 m, providing us with a potential for future development. All of these findings may be useful for researchers and local authorities for the development and utilization of tidal flat resources in Jiangsu.

Wet reclamation of sodium silicate used sand and biological treatment of its wastewater by Nitzschia palea

The massive amount of sodium silicate in the used sand was a pollution source, especially in the waste water from the wet reclamation of used sand. A new process of wet reclamation by biologically treating the waste water produced during the wet reclamation process of used sand was studied in the paper. In the work, the precultivation of N. palea was performed firstly, and three different scrubbing solutions： （1） tap water, （2） modified medium for N. palea, and （3） filtrate of the broth treated by N. palea for 15 days, were used. The results of the primary investigation show that a de-skinning ratio of 90% is obtained when using the scrubbing solution containing modified medium for N. palea at the ratio 1：2 of sand and scrubbing solution, and the maximal concentrations of Na^＋ and SiO3^2- are 1.49 g.L-1 and 0.51 g.L-1, respectively. The results of the optimal biomass, pH value decrease and Na^＋ and SiO32 consumption indicate the optimal incubation conditions are at the irradiance of 5,000 lux and 25 ℃. Using the filtrate of the broth treated by N. palea for 15 days as the scrubbing solution directly, a de-skinning ratio of 93% is the highest compared to the results of the tap water and the modified medium for N. palea. In the biological process using N. palea, less water is used and little wastewater is produced, which is advantageous to the purpose of green manufacturing and environmental protection.

Assessing Reclamation Levels of Coastal Saline Lands with Integrated Stepwise Discriminant Analysis and Laboratory Hyperspectral Data

At different times over the past 30 years in Zhejiang Province, China, the coastal tidelands have been successively enclosed and reclaimed for agricultural land use. The purpose of this work was to evaluate whether laboratory hyperspectral data might be used to estimate the physicochemical characteristics of these reclaimed saline soils. A coastal region of Shangyu City (Zhejiang Province), which was grouped into four subzones according to reclamation history, was used as the study area, and soil samples were collected in each subzone. Physicochemical analyses showed that the soils were characterized by high electrical conductivity and sand content with low organic matter; the longer the saline lands had been reclaimed, the lower were the electrical conductivity and sand content and the higher the organic matter content. These changing trends of soil chemical and physical properties were found in laboratory reflectance spectra of soil samples and their first-order derivative curves. Stepwise discriminant analysis (SDA) identified six salient spectral bands at 488, 530, 670, 880, 1400, and 1900 nm. Using derived discriminant functions for saline lands with different historical years of reclamation, classification revealed an overall accuracy from a self-test of 86.6% and from cross-validation of 89.3%. Therefore, as opposed to time-consuming field investigations, this study suggested that remotely sensed hyperspectral data could serve as a promising measure to assess the reclamation levels of coastal saline lands.