Contamination Assessment and Source Apportionment of Metals and Metalloids Pollution in Agricultural Soil: A Comparison of the APCA-MLR and APCA-GWR Models

Metals and metalloids accumulate in soil, which not only leads to soil degradation and crop yield reduction but also poses hazards to human health. Commonly, source apportionment methods generate an overall relationship between sources and elements and, thus, lack the ability to capture important geographical variations of pollution sources. The present work uses a dataset collected by intensive sampling (1848 topsoil samples containing the metals Cd, Hg, Cr, Pb, and a metalloid of As) in the Shanghai study area and proposes a synthetic approach to source apportionment in the condition of spatial heterogeneity (non-stationarity) through the integration of absolute principal component scores with geographically weighted regression (APCA-GWR). The results showed that three main sources were detected by the APCA, i.e., natural sources, such as alluvial soil materials; agricultural activities, especially the overuse of phosphate fertilizer; and atmospheric deposition pollution from industry coal combustion and transportation activities. APCA-GWR provided more accurate and site-specific pollution source information than the mainstream APCA-MLR, which was verified by higher R2, lower AIC values, and non-spatial autocorrelation of residuals. According to APCA-GWR, natural sources were responsible for As and Cr accumulation in the northern mainland and Pb accumulation in the southern and northern mainland. Atmospheric deposition was the main source of Hg in the entire study area and Pb in the eastern mainland and Chongming Island. Agricultural activities, especially the overuse of phosphate fertilizer, were the main source of Cd across the study area and of As and Cr in the southern regions of the mainland and the middle of Chongming Island. In summary, this study highlights the use of a synthetic APCA-GWR model to efficiently handle source apportionment issues with spatial heterogeneity, which can provide more accurate and specific pollution source information and better references for pollution prevention and human health protection.

Assessing Ecological Vulnerability under Climate Change and Anthropogenic Influence in the Yangtze River Estuarine Island-Chongming Island, China

Understanding and assessing ecological vulnerability for estuarine islands are important for maintaining estuarine island ecosystem services and its sustainable development. However, due to its complex fresh water–sea–land interaction mechanism and multiple stressors from both climate change and anthropogenic influence, a comprehensive evaluation of ecological vulnerability for estuarine islands has been limited. Therefore, taking the typical estuary island of Chongming Island as an example, we developed a comprehensive evaluation system of ecological vulnerability for an estuarine island ecosystem based on the pressure-state-response (PSR) conceptual model, and explored the spatial and temporal distribution of ecological vulnerability in 2005 and 2015. The results indicated that the main pressures of Chongming Island from saltwater intrusion intensity and land use intensity were mainly distributed in northern coastal areas and eastern areas of wetland; the ecological vulnerability index (EV) of Chongming Island showed a slight decrease from 2005 to 2015; and three categories of towns based on ecological vulnerability assessment for an eco-island planning and environmental management were identified. Our study provides an effective evaluation system of ecological vulnerability for estuarine islands, which could be helpful for planners and decision makers in improving eco-island planning and environmental management.

From Wetlands to Farmlands: A Campaign Against Nature on China's Chongming Island, 1960-1962

To confront food insufficiency caused by the Great Leap Forward, China's central government promoted a national policy of 'agriculture as the priority'. The Shanghai municipal government launched a campaign to expand cultivated land within its jurisdiction by transforming wetlands on Chongming Island through a military-style campaign. Tens of thousands of urban workers were drafted into a Land Reclamation Army to meet national and municipal food self-sufficiency goals. Their campaign featured both attacks on nature and interpersonal abuse. In accordance with the central directives, wetlands totalling 8,000 hectares were drained for conversion into farmland. This conversion proved to be costly, as land with low fertility was created through the permanent destruction of the wetland ecosystem and reclamation workers suffered physical and psychological mistreatment. Although the transformation of wetlands was completed quickly, food production fell far short of targets. Furthermore, the land reclamation campaign imposed irrevocable costs on the island's established communitiesotivations in authoritarian regimes operating diverse political and economic agendas.

First Report of Black Spot Caused by Penicillium citreosulfuratum on Saffron in Chongming Island, China

Saffron (Crocus sativus L.) is a world-famous source of dye and spices and an important medicinal plant, which is cultivated on a large scale on Chongming Island (31.62° N, 121.39° E) in Shanghai, China. In August 2020, a survey of saffron was conducted in this area, and black spots were observed on about 10% of plants. Characteristics of the disease were: The bottom of the corm was darkened in the groove and scattered black spots could be observed after peeling off the membranous scale leaves. The junction of lesions and healthy parts was light brown. As the lesions expanded, approximately 80% of the surface of the corm became dark brown to bluish gray. The inside of the corm was also necrotic. In order to isolate the pathogen, ten diseased corms with typical symptoms were selected. All corms were first treated with 75% ethanol for 30 s, 0.1% HgCl2 for 5 min, and then rinsed with sterile water 5 times. Next, tissue pieces (5 mm × 5 mm) at the margin of lesions were cut out and placed on the potato dextrose agar (PDA) medium. After incubating at 28°C for 5 days, fungi were separated and purified by using the hyphal-tip technique. A total of six pure cultures with different colony morphologies were obtained, of which only the isolate MF3 was present in ten diseased corms. The isolate MF3 was inoculated on the PDA and cultured at 28°C for 10 days and characteristics of the fungus colonies were: colonies sub-circular, reaching 28 to 30 mm diam, from above rough, dense, fluffy, blue-gray, with some white spots and central point raised, and outer margin form an irregular, narrow, white ring; from below, yellow with light-green. The hyphae were slender, with many septa. The conidiophores were typically smooth walled, short, and slender and either monoverticillate with very short stipes or as irregularly biverticillate. Phialides were ampulliform, 5 to 10 per metula, 5 to 8 × 2 to 3 µm. Conidia were smooth and globose, and ranged in diameter from 1.4 to 1.7 µm (n=50). Molecular identification of the fungus was made by PCR amplification of the internal transcribed spacer (ITS) region of rDNA and β-tubulin gene using primers ITS1/ITS4 (White et al. 1990), TUB2Fd/TUB4Rd (Aveskamp et al. 2009) respectively. The ITS (MW881446) and β-tubulin (MW911464) sequences of the fungus were similar to the ITS (MN592912) and β-tubulin (KY469126) sequences of the epitype of Penicillium citreosulfuratum with 99.81% and 99.56% identity, respectively. According to the morphological and molecular characterization, the isolate MF3 was identified as P. citreosulfuratum (Visagie et al. 2016). For pathogenicity testing, the fungus was grown on PDA and incubated at 28°C for 5 days. Then mycelial plugs (5 mm diam.) were inoculated on the scalpel incision square wounds of surface-disinfected corms and mock-inoculated corms received only PDA plugs. Corms were placed in sterile plastic bottles and observed after culturing at 28°C for 21 days. Each treatment had three replicates and the experiment was repeated twice. The results showed that corms inoculated with P. citreosulfuratum developed diseased with similar symptoms as in the field. No disease symptoms were observed on control corms. Re-isolations were performed from inoculated corms, and all re-isolated fungi were confirmed as P. citreosulfuratum, verifying the fungus as the pathogen based on Koch’s postulates. To our knowledge, this is the first report of the pathogen causing black spot disease of saffron. Although the disease is not fatal to saffron, to a certain extent it will cause a reduction in the production of the crop. In addition, this pathogen has not been reported to be pathogentic to other plant species.

Wetland Utilization and Adaptation Practice of a Coastal Megacity: A Case Study of Chongming Island, Shanghai, China

Coastal urban areas are faced with risks induced by global warming and sea level rise, which puts pressure on regional sustainable development. In particular, land use adjustment is closely related to climate change for a coastal megacity. Coastal wetlands on the edge of the megacity represent a vulnerable ecosystem and a key area in terms of the resilient adaptation strategy. However, the interrelationship between the development of these wetlands and the megacity’s adaptation practice has not been sufficiently analyzed. From a historical perspective, based on document synthesis and field investigation, we attempt in this study to reveal long-term land use stages and driving factors in association with urban marginal wetlands, with a special reference to eastern Chongming Island, Shanghai. On such a basis, the future adaptation strategy of the megacity is evaluated. The analytical results show that this island has witnessed three periods of time for wetland utilization: traditional land use for salt production, fishery and agriculture before 1950, industrialization with rapid reclamation during 1950–2001, and the land use pattern orientated toward wetland ecosystem protection after 2002. The driving forces include sediment budget on the coast, wetland morphodynamic processes, sea level rise, population growth, and resource management policy changes. Transformation occurred between the wetland utilization stages in response to the changes of these forces. Furthermore, facing future climate change, there are different options of adaptation, e.g., retreatment and adherence. It may not be suitable for coastal cities with a large population to take the first option. It will be suitable for coastal communities to adhere to the location, if solutions to the problems of flooding risk, coastal erosion, and the maintenance of coastal facilities can be found. For eastern Chongming wetlands, as a key experimental area for ecosystem-oriented development in Shanghai, the transformation from the reclamation-oriented utilization toward the protection of wetland ecosystems represents the first step toward the latter option. We suggest that the next steps would be to maintain the ecological niche of the wetlands, to create new approaches to coastal engineering with contributions from the ecosystem, and to provide better ecosystem services.

Spatiotemporal Characteristics of Vegetation Net Primary Productivity on an Intensively-Used Estuarine Alluvial Island

Net Primary Productivity (NPP) can effectively reflect the characteristics and strength of the response to external disturbances on estuarine alluvial island ecosystems, which can provide evidence for regulating human development and utilization activities and improving blue carbon capacity. However, there are a few studies on NPP of estuarine alluvial islands. We established a model based on a Carnegie–Ames–Stanford Approach (CASA) to estimate NPP on Chongming Island, a typical estuarine alluvial island, by considering the actual ecological characteristics of the island. The NPP of different land-cover types and protected areas in different years and seasons were estimated using Remote Sensing and Geographic Information System as the main tools. Correlations between NPP and Remote Sensing-based spatially heterogeneous factors were then conducted. In the last 30 years, the mean NPP of Chongming Island initially increased and then slowly decreased, while total NPP gradually increased. In 2016–2017, Chongming Island total NPP was 422.32 Gg C·a−1, and mean NPP was 287.84 g C·m−2·a−1, showing significant seasonal differences. NPP showed obvious spatial differentiation in both land-cover and protected area types, resulting from joint influences of natural and human activities. Chongming Island vegetation growth status and cover were the main factors that positively affected NPP. Soil surface humidity increased NPP, while soil salinity, surface temperature, and surface aridity were important NPP limiting factors.