Coastal Reclamation Research Articles

A Combination Method for Testing the Mechanical Properties of Ultra-Soft Fine-Grained Soils

Abstract With the consumption of land resources and a shortage of land space, the exploration and use of the ocean have increased. However, a new type of geotechnical engineering problem has been encountered in the development of marine engineering: the problem of ultra-soft soils, such as the dredger fills extracted from sediments in coastal reclamation projects and submarine landslides formed by the movement of sediments. Ultra-soft soils usually have very low strength with high water content, and flow easily. These features enable ultra-soft soils with high water content to exhibit physical properties of both solids and fluids. Reliably testing their mechanical properties presents new challenges for the traditional geotechnical test methods. To address these problems, a test method is proposed that combines a full-flow penetrometer test for soils and a rheological test for fluids. Kaolin samples with water content between 110 % and 157 % (approximately two to three times the liquid limit of kaolin) are tested as an example, and a detailed description and verification of the combination test method are presented. The results show that the combination test method can reliably measure the undrained shear strength of an ultra-soft soil at a wide range of shear strain rates in a short time, which is difficult for traditional methods. The combination test method proposed in this study provides a new reference for mechanical property testing of ultra-soft soils and hazard assessments related to ultra-soft soils.

Effects of soil structure improvement on chlorophyll fluorescence parameters and yield of rice in a coastal reclamation region

To examine the effects of soil structure improvement due to the amendment of biochar and polyacrylamide (PAM) on the chlorophyll fluorescence characteristics of rice leaves and the yield of rice, a pit cultivation experiment was carried out in a coastal reclamation region. Three levels of biochar (0%, 2% and 5% by the mass of 0-20 cm surface soil and noted as B1, B2 and B3, respectively) and PAM (0‰, 0.4‰ and 1‰ by the mass of 0-20 cm surface soil and noted as P1,P2 and P3, respectively) were applied to the adopted soil, respectively. The results of the three-year experiment showed that an appropriate application quantity of biochar and PAM could improve the fluorescence characteristics of rice leaves. However, high levels of biochar and PAM had no obvious or even a negative effect. Among all the treatments, the B2P2 treatment always had the highest the maximum photochemical efficiency (Fv/Fm), the actual photochemical efficiency of photosystem II (ΦPS2), the photochemical quenching coefficient (qP) and the non-photochemical quenching coefficient (NPQ) values during the whole growth period. The chlorophyll content (SPAD value) of rice leaves showed no significant difference among different biochar application levels. However, it showed significant differences among different PAM application levels, with the highest value under the soil amended with 0.4‰ PAM (the P2 treatment). The application of biochar and PAM had significant impacts on rice yield, with the highest yield, namely 7236 kg·hm-2, presenting under the B2P2 treatment, which was 28.5% higher than that of the control. The improved soil structure of the coastal saline soil due to the amendment of biochar and PAM affects rice yield mainly through its influences on the 1000-grain weight, the spike number per hole, the grain number per spike and the seed setting rate. It is concluded that improving soil structure by applying an appropriate quantity of biochar and PAM is conducive to increase the chlorophyll fluorescence characteristics and the yield of rice in the coastal reclamation region.

The Production of Space Through Land Reclamation

This dissertation argues that land reclamation has become geopolitical. Land reclamation has added a new dimension to international relations and this dimension cannot be ignored, for it touches upon our fundamental understanding of state territory and spatial practice. Drawing on Stuart Elden and Henri Lefebvre, territory is understood as a set of political technologies that produce different dimensions of our modern conception of territorial space. Land reclamation operates as such a territorial technology and alters our understanding of maritime space in contemporary geopolitics and international law. Two case studies will explicate this development. The first study will investigate coastal reclamation in Singapore and its effects for the city-state’s international relations. The second study will analyse Chinese reclamation works in the disputed region of the South China Sea. Both investigations will approach these activities with a focus on the United Nations Convention on the Law of the Sea as the international juridical space of territory. In conclusion, this dissertation claims that the material and conceptual production of space triggered by advancements in land reclamation technology are reshaping territorial state practice and the corresponding legal framework of maritime space.

Polycyclic aromatic hydrocarbons (PAHs) in surface soils from reclaimed and ditch wetlands along a 100-year chronosequence of reclamation in a Chinese estuary: Occurrence, sources, and risk assessment

The coastal reclamation for agricultural exploitation have caused serious pollution to the soil environment in coastal wetlands. However, few studies have been conducted on the persistent organic pollutants and ecological risks commonly existing in reclaimed coastal wetlands with different reclamation ages, which is of vital importance to alleviate agricultural soil organic pollution and warrantee food safety. Surface soils (0–10 cm) were collected in reclaimed wetlands (RW) and ditch wetlands (DW) along a 100-year chronosequence of intermittent reclamation (i.e., 100-yr, 40-yr, 30-yr, and 10-yr) in the Pearl River Estuary (PRE) of China. The concentrations of 16 Polycyclic aromatic hydrocarbons (PAHs) in soil samples were determined on a GC–MS 2010 QP-plus to investigate their occurrences, sources, and ecotoxic risk levels. The results showed that the total concentrations of PAHs at eight sampling sites ranged from 67.6 to 1172.8 ng·g−1, with a mean of 466.08 ng·g−1. The concentrations of ∑16PAHs in DW soils increased gradually, whereas the concentrations showed a “decreasing before increasing then decreasing” tendency in RW soils along the chronosequence of reclamation. The highest value occurred in the 30-yr soils of RW, which was heavily polluted, and the rest soils were slightly contaminated except for 40R and 100D soils (no pollution). The PAHs were predominantly composed of 2-, 3-, and 5-ring PAHs (the total accounting for >70% of the total 16 PAHs) at most of sampling sites. And the isomers of PAHs were predominantly composed of naphthalene (Nap), phenanthrene (Phe) and benzo(a)pyrene (Bap), and some PAHs isomers (i.e., Nap, Phe, Bap, fluorene (Fle), benz(a)an-thracene (Baa), and dibenz (a,h) anthracene (Daa) occurred predictable toxicity according to the sediment quality guidelines. A significant positive correlation was observed among the heavy Polycyclic aromatic hydrocarbons (HPAHs, including 4-, 5-, and 6-ring PAHs) and total nitrogen (TN), soil moisture and soil organic matter (SOM) in RW soils (p < 0.05), however, most of PAHs isomers were significantly negatively correlated with soil moisture content in DW soils (p < 0.05). According to the ratios of isomers, the combustion of fossil fuels and petroleum emissions were the major sources of PAHs. The highest value of toxic equivalent concentrations (TEQs)/∑PAHs ratios and TEQs appeared in 10-yr DW soils, followed by 100-yr and 30-yr RW soils, which showed higher potential ecological risks mainly because of certain PAH isomers (Bap and Daa) had higher TEQs and ecological risks.

Comparison between reactive MgO- and Na2SO4-activated low-calcium fly ash-solidified soils dredged from East Lake, China

A novel approach to mitigate the environmental concerns associated with cement industry is to replace Portland cement with low carbon alternative materials such as fly ash-based geopolymer cement. Hence, reactive MgO-activated low-calcium Class F fly ash was employed in comparison to Na2SO4-activated fly ash to stabilize a lacustrine soil reused potentially in soft coastal reclamation projects and as reinforced aggregates for anti-corrosion in marine engineering. The microstructural and strength properties were investigated with series of tests including X-ray diffraction (XRD), thermogravimetry/differential thermogravimetry (TG/DTG), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and unconfined compressive strength (UCS). The results demonstrate that the main hydration products in reactive MgO- and Na2SO4-fly ash-solidified soils are, respectively, magnesium silicate hydrate (M-S-H) gel and sodium aluminosilicate hydrate (N-A-S-H) gel. This finding is reconfirmed by the weight loss of solidified samples at 40–200 °C, which is correspondingly attributed to the dehydration of magnesium silicate hydrate (M-S-H) gel and sodium aluminosilicate hydrate (N-A-S-H) gel. The morphology and bonding ability of hydration products affects the microstructure and long-term strength of solidified soils. The microstructural change identified from SEM images coincides well with the quantitative evolution of pore structure. The pores with radius of 0.01–1 µm, i.e., micropore and mesopore, are supposed to be the dominant pores in reactive MgO- and Na2SO4-activated fly ash-solidified soils. The comparison of UCS indicates reactive MgO-activated low-Ca fly ash behaves much superior to Na2SO4-activated fly ash in enhancing the long-term compressive strength of soils. This study provides insight into the promising potential of low-Ca fly ash activated by immerging material – reactive MgO to replace cement in soil improvement.

STUDY OF THE STABILITY OF COASTAL RECLAMATION SLOPES BY USING GEOTEXTILES AS SOIL STRENGTH

This study presents a simulation of coastal reclamation deposits with geotextiles in areas with the weakest soil profile. Case studies related to deeds and improvement of slopes with woven geotextiles. Observations and investigations show that the land is sand soil which has a low carrying capacity. Weak soil parametric effects, geotextile webbing, external loads, and earthquake loads were analyzed by PLAXIS. The calculation results show reinforcement with woven geotextiles and against external loads and earthquake loads, having a large safety factor.

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.

Synergic effects of biochar and polyacrylamide amendments on the mechanical properties of silt loam soil under coastal reclamation in China

Recent surveys have reported severe erosion and slope collapse caused by a combination of the poor structure of silt loam and heavy rainfall in reclaimed areas of China. Biochar and polyacrylamide (PAM) have been widely used as amendments to protect soil from degradation and enhance plant growth. However, few studies have focused on their synergic effects on soil mechanical properties. In this study, biochar and PAM were incorporated into silt loam at rates of 0%, 2%, and 5% and 0‰, 0.4‰, and 1‰, respectively, to investigate the extent to which biochar and PAM additions affect soil consistency limits and shear strength and to evaluate the slope reliability under natural conditions. The results show that the plastic limit (PL) and liquid limit (LL) were significantly enhanced by amendments of 5% biochar and 1‰ PAM. Soil consistency limits were significantly correlated with the soil 3D fractal dimension (FD), μ-CT porosity and electrical conductivity (EC). Amendment of coastal silt loam soil with biochar resulted in decreased cohesion. The application of PAM reduced the negative effect of biochar on cohesion and considerably increased the cohesion value of the silt loam. The results of the slope stability analysis were closely related to the shear strength parameters. Biochar-amended silt loam soil in the coastal area exhibited a much lower factor of safety (FS) compared with the control soil, irrespective of the level of the water and the slope angle within the slope system. A PAM amendment in coastal silt loam soil increased the FS significantly (P < 0.05) and minimized the negative effects on the FS that was caused by the biochar amendment. Therefore, biochar and PAM could be applied to silt loam soil together to improve soil quality to enhance the slope stability under coastal reclamation in China.

Impacts of Coastal Reclamation on Natural Wetlands in Large River Deltas in China

Little information is available on the impacts of coastal reclamation on wetland loss in large-river deltas at a regional scale. Using remote sensing data of coastal wetland and reclamation in four deltas in China from 1978 to 2014, we tracked their continuous area changes in four periods: 1978–1990, 1990–2000, 2000–2008, and 2008–2014. The areal relation between wetland loss and reclamation was quantified and used to identify coastal reclamation mode intensity coupled with another three indicators: reclamation rate, accretion rate and land-use intensity of coastal reclamation. The results showed that coastal reclamation driven by economic development reduced, or even reverse the original growth of delta which was determined by the offset between wetland acceleration rate and wetland loss rate. Generally, the area of reclamation showed a positive linear correlation with the area of wetland loss. The findings imply that human activities should control reclamation rate and intensity to alleviate total wetland loss and maintain wetland ‘net gain’. Inappropriate coastal reclamation modes can magnify total wetland loss; therefore, coastal reclamation with a slow increment rate and low impervious surface percent is of great importance for sustainable development in future coastal management.

Effects of reclamation and natural changes on coastal wetlands bordering China's Yellow Sea from 1984 to 2015

AbstractCoastal wetlands are rapidly disappearing worldwide, which is posing a substantial threat to the integrity of coastal ecosystems. In addition to the direct area reduction caused by reclamation, coastal wetlands experience natural changes due to sediment transport in coastal regions. Arguably, the reclamation rates must be less than the net accretion rate to guarantee the restoration of coastal wetlands. By applying an automatic and replicable shoreline algorithm to all available Landsat imagery from 1984 to 2015 using the Google Earth Engine Cloud Platform, we developed distribution maps of coastal wetlands and reclamation in China's Yellow Sea (CYS) at 4‐ or 5‐year intervals. In addition, we divided coastal wetlands into saltmarshes and mudflats and analysed their trends separately. Over the past 30 years, the area of coastal wetlands decreased by 53% (from 6,463 to 3,036 km2), including a 67% decrease in saltmarshes (from 1,471 to 489 km2) and a 49% decrease in mudflats (from 4,992 to 2,547 km2). Meanwhile, the reclaimed area was 7,696 km2 (including 1,276 km2 of saltmarshes and 3,002 km2 of mudflats), which exceeded the area of newly formed coastal wetlands (852 km2). The natural state of mudflats gradually changed from accretion to erosion, but without considering the natural state of coastal wetlands, reclamation will continue at a high rate in CYS according to China's national marine functional zoning (MFZ) for 2010–2020. In view of their important ecological services, there is an urgent need to revise the national MFZ to achieve ‘no net loss’ of coastal wetlands.

Changes in surface soil organic/inorganic carbon concentrations and their driving forces in reclaimed coastal tidal flats

Intensive coastal wetland reclamation in China followed by agricultural use had significant impacts on soil carbon (C) dynamics due to the alterations in soil hydrology and physicochemical properties. The changes in C and its driving factors in reclaimed soils generally concentrated on soil organic C (SOC) and soil inorganic C (SIC) as major subpools of soil C, but this topic has received little attention. In this study, we have assessed the changes in SOC and SIC concentrations (0–20 cm) with reclamation duration and land use change based on 746 surface soil samples collected from three typical reclamation areas (with differences in sediment sources) in eastern China. Key factors driving SOC and SIC dynamics were identified using a random forest model (RF). The results revealed similar SOC concentration (7.24–7.69 g kg−1) and different SIC concentration (7.25–10.9 g kg−1) for the three study areas. Overall, SOC increased with reclamation duration, suggesting a positive impact of tidal flat reclamation on SOC accumulation. For SIC, slight increases in the younger land and dramatic decreases in the older land were observed, indicating a fast IC turnover time. The land impacted strongly by human activities had higher SOC than natural tidal flats. Compared with upland soil, paddy soil resulted in greater OC (except for 10 years reclaimed land in Cixi) and comparable levels of IC. Soil nutrient levels (the concentrations of nitrogen and phosphorus) were determined to be important factors for SOC in reclaimed lands. Soil CaO was determined to be the factor with the highest importance in controlling SIC dynamics in reclaimed lands. More attention should be given to the quality of the OC sequestrated by reclaimed soils.

Water flow and salt transport in bare saline‐sodic soils subjected to evaporation and intermittent irrigation with saline/distilled water

AbstractSustainable development of coastal reclamation areas is severely restricted by the high soil salt content and irrigation water salinity. We investigated the water flow and salt transport in open soil columns subjected to evaporation and intermittent irrigation with saline/distilled water by long‐term wetting–drying cycles. The study included two different soil materials (silt loam and silty clay) with four to five soil sodicity levels. Three groups of experiments with three replicates were imposed: silt loam × 5 sodicity level, silty clay × 5 sodicity level, and 2 soil textures × 5 irrigation water qualities. Three irrigations were conducted in Spring to early Autumn (March 2, June 30, and September 8), whereas the soil columns were subjected to the natural evaporation without rainfall throughout the period September 9 to March 1. The average daily soil evaporation rate significantly decreased with the soil clay content (pr = −0.55; P &lt; 0.001), soil exchangeable sodium percentage (pr = −0.54; P &lt; 0.001), and irrigation water salinity (pr = −0.32; P &lt; 0.001). The soil properties were the major factors responsible for controlling evaporation, whereas the irrigation water salinity was the less important factor. Soil salt distribution was significantly affected by the soil clay content (pr = 0.82; P &lt; 0.001), soil depth (pr = 0.68; P &lt; 0.05), soil exchangeable sodium percentage (pr = 0.85; P &lt; 0.001), and irrigation water salinity (pr = 0.37; P &lt; 0.001). The magnitudes of the steady‐state infiltration rate ic and soil saturated hydraulic conductivity Ks were largely reduced by wetting–drying cycles, especially for the silty clay. Understanding water flow and salt transport in saline‐sodic soils subjected to evaporation and intermittent irrigation with saline/distilled water is important for improving the soil desalination project and strategy.

Linkage between soil salinization indicators and physicochemical properties in a long-term intensive agricultural coastal reclamation area, Eastern China

Soil salinization is a major restricting factor for crop growth and agriculture productivity in coastal areas. Exploring the evolution of soil salinization indicators and physicochemical properties and their relationships in a long-term scale can provide a basis for the restoration, utilization, and prediction of coastal salinized soil. This study aimed to investigate the impact of reclamation years on soil salinization indicators and physicochemical properties in reclaimed coastal tidal land, and analysis the linkage between soil salinization indicators and physicochemical properties after long-term reclamation. Soil sample sites were respectively collected from reclamation regions reclaimed in 1951, 1974, 1982, and 2007 according to typical land use types. Besides, the natural tidal flat was collected as control. Soil samples were divided into two parts to determine soil bulk density (BD), soil water content (SWC), soil particle size distribution (PSD), soil salt content (SSC), pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), organic matter (SOM), alkaline hydrolyzed nitrogen (AN), and available phosphorus (AP). One-way analysis of variations (ANOVA) was conducted to investigate the differences in soil properties within different reclamation years. The linkage between soil salinization indicators and soil physicochemical properties was analyzed by redundancy analysis and Monte Carlo permutation. Compared with uncultivated tidal land, soil salinization indicators (SSC, pH, SAR, and ESP) significantly decreased after 30 years reclamation owing to the natural leaching and field management. Soil nutrients (SOM, TN, TP, AN, AP, CEC) apparently increased after reclamation of 30 years due to long-term fertilization. Moreover, SWC, BD, and SAND gradually decreased, whereas SILT and CLAY gradually increased after reclamation of 61 years. Soil salinization indicators were observed have a positive correlation with SAND and a negative correlation with SILT, CLAY, and soil nutrients. Long-term reclamation could radically decreased soil salinization (SSC, pH, SAR, ESP) and apparently promoted soil nutrients accumulation (SOM, TN, TP, AN, AP, CEC). Furthermore, soil salinization indicators are closely related to soil physicochemical properties, and soil PSD and soil nutrients were considered as the key factors for the differences of soil salinization.

The lives of women in a land reclamation project: Gender, class, culture and place in Egyptian land and water management

This article links feminist political ecology with the academic debate about commoning by focusing on the gendered distribution of common pool resources, in particular land and water. The research is set in the context of a coastal land reclamation project in Egypt’s Nile Delta, in a region where conflicts over resources such as arable land and fresh water are intensifying. Drawing on recent literature on commoning, we analyse the conditions under which different groups of resource users are constrained or enabled to act together. The article presents three case studies of women who represent different groups using land and water resources along the same irrigation canal. Through the concepts of intersectionality, performativity, and gendered subjectivity, this article explores how these women negotiate access to land and water resources to sustain viable livelihoods. The case studies unpack how the intersection of gender, class, culture, and place produces gendered subject positions in everyday resource access, and how this intersectionality either facilitates or constrains commoning. We argue that commoning practices are culturally and spatially specific and shaped by pre-existing resource access. Such access is often unequally structured along categories of class and gender in land reclamation and irrigation projects.

Applying Uncertain Science to Nature-Based Coastal Protection: Lessons From Shallow Wetland-Dominated Shores

Climate change and associated sea-level rise alongside the potential for alterations in the magnitude and frequency of extreme storm events, rapidly rising coastal populations, and a legacy of coastal land reclamation have led to the consideration of nature-based approaches towards coastal flood and erosion protection over recent years. The descriptions of such approaches highlight the flood protection value of natural coastal features but examples of their implementation remain few and far between and nature-based solutions to the rising coastal flood and erosion risk can certainly not (yet) be considered mainstream. One key problem around the implementation of these types of approaches has, arguably, been the relative lack of perceived scientific certainty, amongst stakeholders, surrounding the efficiency with which natural landforms reduce wave action on landward lying structures and the persistence of such landforms in an uncertain future. This makes nature-inclusive approaches less attractive to more traditional engineering-only approaches that rely solely on one ‘hard’ structure with a well-defined impact on waves and a specified design life. Using existing evidence for the coastal protection function of salt marshes, this paper offers a new perspective on this apparent lack of scientific certainty by offering a ‘no-regret’ application of existing science that allows decision makers and coastal planners to implement nature-inclusive approaches to coastal flood and erosion risk reduction measures with greater confidence.

Shift in soil organic carbon and nitrogen pools in different reclaimed lands following intensive coastal reclamation on the coasts of eastern China

The impacts of coastal reclamation on carbon (C) and nitrogen (N) sinks of coastal wetlands remain unclearly understood. This study was conducted to investigate the alterations of soil organic C and N (SOC and SON) pools following conversion of Phragmites australis salt marsh into fishpond, wheat and rapeseed fields and town construction land through reclamation along Jiangsu coast in eastern China. Coastal reclamation significantly increased stocks of soil total, labile and recalcitrant organic C and N (SLOC, SLON, SROC, and SRON), and concentrations of water-soluble organic C (WSOC), microbial biomass C and N (SMBC and SMBN), cumulative CO2-C mineralization (MINC) following conversion of P. australis salt marsh into fishpond, wheat and rapeseed fields. However, coastal reclamation reduced SOC, SLOC, SROC, SRON, WSOC, SMBC, SMBN, and MINC following conversion of P. australis salt marsh into town construction land. Our results suggest that coastal reclamation affects C and N sinks of coastal wetlands by changing SOC and SON pools size, stability and dynamics changes following conversion of P. australis salt marsh into other land use types. This finding were primarily attributed to alterations in quantity and quality of exogenous materials returning the soil, and soil physiochemical properties as affected by coastal reclamation.

Hydrodynamic changes due to coastal reclamation activities in Daya Bay

Based on the geometry and surface in Daya Bay, we artificially divided the reclamation projects into three periods to analyze the influences and changes on hydrodynamic conditions as a result of the reclamation projects. Three periods of tidal current fields, tidal prisms, and water exchange capacity are simulated by the Finite-Volume, primitive equation Community Ocean Model and the characteristics and trends of hydrodynamics in Daya Bay are discussed. The combination of observation and simulation in this paper gives a good description on the tidal dynamic system in Daya Bay. As indicated by model results, the tidal current velocity in the Bay totally decreases after numerous activities associated with reclamation construction. The decreasing current velocity region is mainly distributed near the Xiachong and Gangkou chain islands. The current velocity in 2015 decreases by approximately 5 cm s−1 compared with velocities before 2000. Future reclamation activities will exacerbate these decreasing current velocity trends in some regions. Compared with 2015, the tidal prism has significantly decreased by 1.3622 × 107 m3 due to planned reclamation. The half-water exchange times for Daya Bay in 2015 and after planned reclamation are 178.9 and 177.4 days, respectively. The water exchange capacity in Fanhe Harbor is weaker than other water fields throughout Daya Bay.

Cerium-modified biochar: A recycling biomaterial for regulating phosphorus availability in paddy ecosystem from coastal mudflat reclamation

Phosphorus (P) is a vital element for plant growth, especially in mudflat-reclaimed soil due to its extra alleviation of adverse effect by salt stress. P availability in mudflat-reclaimed soil is a critical factor for crop yield. In this study, cerium-modified straw biochar (Ce-MSB) derived from maize straw was prepared and characterized and its influence on P availability of the paddy soil was evaluated. The results indicated that the cerium elements were chemically bound to the functional groups of the biochar surface through SEM, EDX and FTIR techniques. The equilibrium process of P by Ce-MSB was described well by the Langmuir isotherm model (R2 > 0.99). The maximal P adsorption capacity of Ce-MSB was influenced remarkably by temperature. Accordingly, the addition of Ce-MSB significantly decreased the P content of surface water in paddy system after 3 months, while increasing the soil P availability. Furthermore, the incorporation of both common biochar and Ce-MSB into the soil increased the SOM content, while decreased soil pH and EC. Biolog EcoPlateTM trials indicated that Ce-MSB has no significantly negative effects on soil microbial diversity. This study provides valuable information for the source-reduction of P discharge from paddy system and improvement of P availability.Phosphorus (P) is a vital element for plant growth, especially in coastal reclaimed mudflat due to its extra alleviation of adverse effect by salt stress. P availability in mudflat-reclaimed soil is a critical factor for crop yield. In this study, cerium-modified straw biochar (Ce-MSB) derived from maize straw was prepared and characterized and its influence on P availability of the paddy soil was evaluated. The results indicated that the cerium elements were chemically bound to the functional groups of the biochar surface through scanning electron microscopy (SEM), energy dispersive X-ray spectrum scanning (EDX), and fourier transform infrared spectroscopy (FTIR) techniques. The equilibrium process of P (PO43−) by Ce-MSB was described well by the Langmuir isotherm model (R2 > 0.99). The maximal P adsorption capacity of Ce-MSB was influenced remarkably by temperature, which was 58, 69, and 78 mg g−1 under 5, 25, and 40 °C, respectively. Under laboratory simulation, the addition of Ce-MSB significantly decreased the P content of surface water in paddy system after 3 months, while increasing the P availability of soil. Furthermore, the incorporation of both common biochar and Ce-MSB into the soil increased the SOM content, while decreased soil pH and EC. Biolog EcoPlateTM trials indicated that Ce-MSB has no significantly negative effects on soil microbial diversity. This study provides valuable information for the source-reduction of P discharge from paddy system and improvement of P availability.

Effect of biochar on sweet corn and soil salinity under conjunctive irrigation with brackish water in coastal saline soil

Coastal areas of Eastern China possess substantial salt-affected lands and brackish water for agriculture usage. A novel method using biochar and conjunctive irrigation was conducted to explore the reliable utilization of these low-quality resources. Sweet corn (Z. mays L. saccharate) was grown in a coastal saline soil amended with biochar (0 and 5%). Conjunctive irrigation was carried out by alternately applying brackish water (non-saline, 2, 6, 10 dS m−1) and freshwater at the vegetative and reproductive phase. Biochar application improved sweet corn photosynthetic performance and mitigated oxidative damage as well as salt stress, further resulted in higher production and marketable value. Meanwhile, biochar amendment facilitated the availability of saline irrigation during salt sensitive stages, promoting the conjunctive irrigation with brackish water for the coastal reclamation. In addition, more salts were removed out due to biochar after leaching, and the addition of biochar reduced the salinity of the soil profile during conjunctive irrigation. In general, under conjunctive irrigation, biochar application led to enhanced growth of sweet corn and favorable salinity control in the soil profile. However, further long-term field studies should be conducted to evaluate the complex effects of biochar for agricultural production using low-quality soil and water resources in coastal regions.

The role of the hydrogeological and anthropogenic factors on the environmental equilibrium of the Ugento Wetland (Southern Italy)

The Ugento Wetland, recognized as a Site of Community Importance (SCI, European Directive 92/43/CEE) from 2005, is a “Regional natural littoral Park” from 2007. It includes some coastal reclamation works. It is a Groundwater Dependent Ecosystem (GDE); its environmental peculiarities are due to a complex hydrogeological pattern and to a peculiar dynamic equilibrium with sea, also due to the role of the wide coastal aquifer of Salento. The main objectives of the present research is the definition of the hydrogeological conceptualization to be integrated with the knowledge of the physical environment, to be used as a basis for thedesign of effective management of water resources to safeguard the ecological and environmental equilibria, considering the relevant impact of anthropogenic activities. The overlapping of geological and hydrogeological factors and anthropogenic modifications is discussed using selected indicators, with reference to two macro-indicators, water and soil. The critical issues related to the human activities potentially dangerous for the wetland environment, was considered with the definition of guidelines for their mitigation, based on the discussion of the indicators.