Search

The impacts of coastal embankments on nitrogen (N) dynamics are of great importance in salt marshes. However, effects of embankments on seasonal N dynamics in the plant-soil systems of Suaeda salsa salt marshes are still not well understood. Therefore, the edaphic moisture and salinity, biomass, N concentrations and storage in different plant tissues; the extent of organic and inorganic N subpools in soil subsystems; as well as N immobilization and mineralization by microorganisms in embanked and neighboring natural S. salsa salt marshes through all four seasons were investigated in Yancheng, Eastern China. Our results revealed that embankments increased the biomass and N storage of dead tissues (e.g., litter), while they decreased the biomass and N storage of live tissues (e.g., living aboveground tissues and roots) of S. salsa through decreased edaphic moisture and salinity. Furthermore, under the influence of embankments edaphic water-dissolvable N, e.g.,edaphic dissolved organic N (EDON) and nitrate and nitrite N (TNN), significantly increased with higher N inputs from S. salsa litter. This water-dissolvable N was an important source of N for plants, which translated to higher N concentrations in live plant tissues. However, this excess absorbed N appeared not to facilitate the growth of plants, which would ultimately return to the soil from plant residues. Our results suggested that the decreased edaphic soil moisture and salinity due to embankments had negative impacts on the biomass and N storage of S. salsa plant tissues, which were likely due to shifts in the edaphic osmotic potential. Subsequently, a cascading butterfly effect may be initiated due to the impaired growth of S. salsa , to which more attention should be paid. This study represents a step forward by providing valuable insights and an improved elucidation of the seasonal plant-soil N dynamics of S. salsa salt marshes. • The embankment reduced the N storage of living plant tissues by decreasing the edaphic moisture and salinity. • Increased litter N storage due to the decreasing edaphic moisture and salinity by the embankments. • Enhancing N inputs from litter by the embankment lead to the edaphic water-dissolvable N remarkably increased. • The increased N concentrations of microbes and plants caused by lowering edaphic moisture and salinity due to the embankments. [ABSTRACT FROM AUTHOR]

The accumulation of heavy metals (HMs) in soil caused by mineral resource exploitation and its ancillary industrial processes poses a threat to ecology and public health. Effective risk control measures require a quantification of the impacts and contributions to health risks from individual sources of soil HMs. Based on high-density sampling, soil contamination risk indexes, positive matrix factorization (PMF) model, Monte Carlo simulation and human health risk analysis model were applied to investigate the risk of HMs in a typical mining town in North China. The results showed that As was the most dominant soil pollutant factor, Cd and Hg were the most dominant soil ecological risk factors, and Cr and Ni were the most dominant health risk factors in the study area. Overall, both pollution and ecological risks were at low levels, while there were still some higher hazard areas located in the central and south-central part of the region. According to the probabilistic health risk assessment (HRA), children suffered greater health risks than adults, with 21.63% of non-carcinogenic risks and 53.24% of carcinogenic risks exceeding the prescribed thresholds (HI > 1 and TCR >1E-4). The PMF model identified five potential sources: fuel combustion (FC), processing of building materials with limestone as raw materials (PBML), industry source (IS), iron ore mining combined with garbage (IOG), and agriculture source (AS). PBML is the primary source of soil HM contamination, as well as the major anthropogenic source of carcinogenic risk for all populations. Agricultural inputs associated with As are the major source of non-carcinogenic risk. This study offers a good example of probabilistic HRA using specific sources, which can provide a valuable reference for strategy establishment of pollution remediation and risk prevention and control. [Display omitted] • As, Cd and Hg are main HMs causing soil contamination and ecological risk. • Probabilistic health risks from different sources were quantitatively calculated. • PBML is the main source of heavy metals, follow by IOG. • 21.63% non-carcinogenic and 53.24% carcinogenic risks for child cannot be negligible. • PBML and AS contribute the most to the health risks of heavy metals. [ABSTRACT FROM AUTHOR]