You Can Bend Me but Can’t Break Me: Vegetation Regeneration After Hurricane María Passed Over an Urban Coastal Wetland in Northeastern Puerto Rico

Tropical urban coastal wetland regeneration is complex. Wetland plant biodiversity varies due to past and present land use, nutrient inputs, hydrological conditions, and terrestrial/marine connectivity. The intensity of atmospheric disturbances, such as hurricanes, will determine these systems’ level of disturbance and regeneration capacity. On September 20, 2017, category 4 hurricane María passed over Puerto Rico, leaving behind a path of destruction across the entire island, especially in coastal ecosystems, from the combined effects of winds, severe storm surges, and urban runoff. Our question was: to what extent do human-influenced coastal urban wetlands regenerate after such a massive event. This study determines the spatio-temporal regeneration dynamics of plant cover and composition during the first 2 years after hurricane María in a coastal urban wetland, ciénaga Las Cucharillas, located in San Juan Bay. We assessed the distribution of plant functional types using small unmanned aerial vehicles (s-UAV) and monitored climate and environmental data (salinity, phreatic water levels, and precipitation). Wetland vegetation cover had a high recovery rate – 16 months after the hurricane, vegetation cover occupied 87% of the study area. We found a successional pattern of plant regeneration that seemed to be partly explained by the fast-slow continuum. Plants with high specific leaf area (SLA) colonized bare soil spaces first. Plant regeneration also varied according to changes in phreatic water conductivity and waterlogging. Isotopic analyses of plant species signaled high nutrient availability, increasing the system’s regeneration speed. After 2 years, the wetland’s plant cover and composition of functional plant types proved resilient to the initial hurricane effect and subsequent changes in conductivity and freshwater conditions. Further studies will expand how spatio-temporal conditions will affect long-term plant community dynamics.

Chemical characteristics of surface and phreatic water and their effects on the growth of Populus euphartica Oliv. in desert areas of Tarim National Nature Reserve, China

Chemical characteristics of surface water and phreatic water and their relationship with the growth of Populus euphratica Oliv. were explored. In the study area, hydrochemical types of the surface water were mainly SCaⅢ or ClNaⅢ (Based on the O. A. Arliekin's classification) and PH value of the surface water was below 8.0. The surface water from various sampling sites has a higher total hardness belonging to hard water and extremely hard water. The contents of sulfates and chlorides in the surface water in the protection zone ranged from 204.1 to 486.3 mg/l and from 70.9 to 239.9 mg/l, respectively. Phreatic water is mainly recharged by the surface water infiltration. In terms of water quality, TDS, total hardness and total alkalinity of phreatic water at W2 sampling point were 17.3, 9.3 and 4.7 times of surface water, respectively. Populus euphratica was able to grow normally in the environment of brackish water, where total hardness, total alkalinity, and TDS of overflowing river were in the range of 325.3~769.5, 142.6~290.3 and 782.2~1037.5 mg/l, respectively. The Populus euphratica in juvenile phase was a few, and its rejuvenation was confronted with difficulty. The present study can provide a reference for exploring the water quality characteristics of surface and phreatic water and their relationship with the growth of Populus euphratica. Bangladesh J. Bot. 50(3): 831-836, 2021 (September) Special

Influence of Gully Land Consolidation on Phreatic Water Transformation in the Loess Hilly and Gully Region

Gully Land Consolidation (GLC) is a proven method to create farmlands and increase crop yields in the Loess Hilly and Gully Region, China. However, GLC influences phreatic water transformation and might cause the farmlands water disasters, such as salinization and swamping. For exploring the influence of GLC on phreatic water transformation and mitigating disasters, a series of indoor experiments were conducted in the artificial rainfall hall. Then, we simulated the phreatic water transformation patterns under more conditions with HYDRUS-3D. Finally, an engineering demonstration in the field was performed to validate our research. The indoor experiments indicated that GLC could increase phreatic water outflow rate 4.39 times and phreatic water coefficient (PWC) 2.86 times with a considerable delay. After calibration and validation with experimental data, the HYDRUS-3D was used to simulate phreatic water transformation under more soil thickness and rainfall intensities. Accordingly, we summarized the relationship among PWC, rainfall intensities, and soil thickness, and therefore suggested a blind ditch system to alleviate farmlands disasters. Field application showed that a blind ditch system could avoid disasters with 3.2 times the phreatic water transformation rate compared to loess. Our research provides implications for sustainable land uses and management in the region with thick soil covers.

Height of Mining-Induced Fractured Zones in Overlying Strata and Permeability of Rock with Nonpenetrative Fractures

Exploitation of shallow thick coal seams that are overlain by phreatic aquifers may cause loss of the water resource and destruction of the surface ecological environment. In order to explain the phenomenon that the actual leakage of phreatic water is greater than the predicted value, field investigation and analogue simulation were carried out, and the nonpenetrative fractured zone (NFZ) was proposed based on the original three zone theory. Further, a “vertical four-zone model” was established and the overlying strata was divided into a caved zone (CZ), through-going fractured zone (TFZ), NFZ, and continuous zone (COZ) from the bottom to the top. The characteristics of fractured rock within NFZ and the determination method of its height were studied. The results showed that the height of NFZ ranged from 11.55 to 21.20 m, which was approximately 0.17 times the combined height of the TFZ and the CZ. To reveal the mechanism of phreatic water leakage, the permeability of rock within NFZ was studied for their premining and postmining using an in situ water injection test and laboratory test. The results showed that the permeability of the rock in NFZ was increased by 7.52 to 48.37 times due to mining, and the magnitude of the increase was nonlinear from top to bottom. The increase of permeability of tested specimens was also related to the lithology. The results of the study are helpful to the prediction of the potential loss of phreatic water and the determination of the mining thickness.

Distribution of fluoride in groundwater around Chagan Lake and its risk assessment under the influence of human activities

Chagan Lake is located in the area of Western Jilin for which waterways have high fluorine content. Because of the construction of water conservancy projects and agricultural irrigation areas, the groundwater replenishment and drainage conditions there have changed. Groundwater test data were used to analyze the status of groundwater fluoride with this changing hydrodynamic gradient. The paper established a health risk assessment model based on triangular fuzzy number. The results show that the samples of phreatic water and confined water with excessive fluoride content accounted for 68.74% and 29.4%, respectively. Samples that exceeded standards of fluoride content were mainly distributed in the northwest and southwest. The chemistry of phreatic water is more complicated than that of confined water. The water quality categories are mainly poor and very poor. The formation of major anions and cations was mainly controlled by evaporation and rock weathering. It was also found that non-carcinogenic risks of fluoride in phreatic water are greater than those in confined water. The risk indices for children and adults were [1.1, 1.6] and [0.6, 0.9], respectively (α = 0.8). The non-carcinogenic risk assessment model based on triangular fuzzy numbers has a higher reference value than that of traditional models.

Hydrochemical characteristics and processes for salinity sources of the shallow groundwater along the coast of northern Jiangsu, China

<p><strong>Abstract：</strong>In order to find out the hydrochemistry and salinization of shallow groundwater in coastal aquifers, 76 ground- and surface-water samples, contained phreatic upper water, phreatic water, confined water, river water and seawater were collected for major ion and isotope analysis(<sup>2</sup>H/<sup>18</sup>O, <sup>14</sup>C). The results show that: (1) The phreatic upper groundwater changes along the general flowpath towards the coast from fresh(TDS <1 g/L), brackish (1–3 g/L) to saline (3–50 g/L). The phreatic water and first confined water are basically unchanged, but mainly saline water. (2) Shallow groundwater is mainly derived from atmospheric precipitation and undergoes significant evaporation processes. The phreatic upper groundwater is mainly derived from modern atmospheric precipitation recharge. The phreatic water and first confined water are mainly derived from precipitation replenishment during the warm period of the Holocene and some relict seawater. (3) The processes for salinity sources of the shallow groundwater are that oceanic evaporative salt formed during the transgression and retreat period since the late Pleistocene was dissolved by atmospheric precipitation and river water for many periods. The salt in phreatic upper water of the estuary area is also derived from modern seawater intrusion.</p><p><strong>Key words:</strong> coastal zone; groundwater; hydrochemistry; hydrogen and oxygen stable isotope; salinization</p><p>_____________</p><p><strong> </strong></p><p><strong>Corresponding author. Qingdao Institute of Marine Geology, China Geologic Survey, Qingdao, 266071, PR China.</strong></p><p><strong>E-mail address: [email protected].</strong></p><p><strong>This study was financially supported by the National Natural</strong><strong> </strong><strong>Science Foundation of China (41977173)</strong><strong>, </strong><strong>China Geology</strong><strong> </strong><strong>Survey</strong><strong> </strong><strong>project</strong><strong>(</strong><strong>DD20189503</strong><strong>) and National key research and development projects(2016YFC0402801)</strong></p>

Phreatic Water Quality Assessment and Associated Hydrogeochemical Processes in an Irrigated Region Along the Upper Yellow River, Northwestern China

Groundwater resources are playing an increasingly vital role in water supply for domestic and irrigation purposes in the Yinchuan Plain, along with the reduction in water transfer from the Yellow River. This study aimed to identify the current status of phreatic water quality and associated hydrogeochemical processes in an irrigated region along the upper Yellow River. A total of 78 water samples were collected in September 2018 for chemical analysis. Results showed that the phreatic water was excellent or good in most areas west of the Yellow River, while it was poor or very poor quality in some places east of the Yellow River. The nitrate contamination is particularly severe in the pluvial-alluvial plain, relating to the localized fine-grained zone with low permeability. Most samples had no sodium hazard but had magnesium hazard. Additionally, the overall evolutionary trend of the phreatic water showed the transformation of Ca-Mg-HCO3 into Na-Cl-SO4 type. Rock weathering and evaporation jointly predominate the evolution of phreatic water chemistry. The main geochemical processes involve the dissolution/precipitation of gypsum, halite, dolomite. and calcite, along with the cation exchange. Insights from this work have important implications for groundwater sustainable management in such irrigated regions along the upper Yellow River.