Rapid urbanization has driven extensive coastal land reclamation worldwide. However, the soils used often contain geogenic contaminants, particularly arsenic, posing a largely unrecognized but substantial threat to the environment and human health. Here we present a comparative analysis of arsenic speciation in naturally contaminated coastal soils, revealing distinct risk profiles between reclaimed and natural environments. Analysis of 1029 soil samples from the Pearl River Delta, with detailed characterization of 29 high-arsenic samples using integrated chemical and microscale techniques, identifies two contrasting arsenic occurrence patterns: reclaimed soils dominated by unstable arsenic sulfide species versus natural hilly soils characterized by stable arsenic oxide species. The findings demonstrate that land development activities, hydrological dynamics and sea-level rise can trigger arsenic release in reclaimed soils. To mitigate these risks, an integrated risk management framework is proposed. This research provides valuable insights to inform sustainable land reclamation management across rapidly urbanizing coastal regions.

The objective of the study is to evaluate the degradability of volatile organic compounds (VOCs, in mixture) by sodium persulfate (SPS) with Fe(II) activation. Degradation of 51 VOCs by SPS alone and with 3 Fe(II)-based activators (i.e. ferrous ion, citric acid-chelated Fe(II), and EDTA-chelated Fe(II)) was investigated in batch experiments. In 48 h, 16 VOCs degraded over 90% with non-activated SPS, and 31 VOCs degraded over 90% with Fe(II) activation. The reaction rate constants of VOC degradation were also analyzed by quantitative structure-activity relationship (QSAR) model. Genetic algorithm and multiple linear regression analysis were applied to select the descriptors to build QSAR model. The main contribution to the degradation rate was given by energy level of highest occupied molecular orbital (E_HOMO), double bond equivalent, and the largest negative partial net charge on a carbon atom ( ). Based on cluster analysis of degradation rates and main descriptors, the degradability of target VOCs were classified into three classes—rapid, moderate, and slow. The obtained statistically robust QSAR model can be used to estimate the removal efficiency of VOCs by persulfate radicals.

Industrial soil is susceptible to acid or alkali pollution, but studies focused on the remediation of such soil are still limited. This manuscript investigated the neutralization effect of five agents (hydrochloric acid, citric acid, ferrous sulfate, calcium superphosphate and raw gypsum) to alkali polluted soil. The results showed that regarding the initial pH after the neutralizing agent addition, it was better to set it lower than the target, as the pH would rebound. None of the five agents caused an obvious increase in the heavy metal contents of the leachates, but they all caused an increase in electrical conductivity, which indicated an increase in soil salinity. The leachates showed a luminous gain to Vibrio fischeri. However, remediation with hydrochloric acid would cause significant inhibition of germination and root elongation of pakchoi. In addition, the addition of neutralizing agents reshaped the soil microbial community structure in different patterns. Soils treated with hydrochloric acid and ferrous sulfate seemed to improve the microbial richness. The neutralization might be favorable for the biodegradation of polycyclic aromatic hydrocarbons (PAHs), which usually coexist in industrial contaminated soil. In general, the neutralization of alkaline industrial soils using ferrous sulfate, superphosphate and gypsum brought minimal environmental risk, among which ferrous sulfate was the first recommendation in industrial soil after a comprehensive comparison.

Alkali-activated persulfate (PS) is widely used in situ in chemical oxidation processes; however, studies on the innovation of the alkali activation process are very limited. Two supported solid superbases, namely KNO₃/γ-Al₂O₃ (KAl) and KNO₃/SBA-15/MgO (KSM), respectively, were prepared and used to activate persulfate to degrade DCF in this work. The results showed that the superbases elevated the solution pH once added and thus could catalyze persulfate to degrade diclofenac efficiently above pH 10.5. The catalytic efficiency of KAl was close to that of sodium hydroxide, and that of KSM was the highest. The mechanism might be that, in addition to raising the solution pH, some potassium existed as K₂O₂, which had a strong oxidizing effect and was conducive to DCF removal. Hydroxyl, sulfate and superoxide radicals were all found in the reaction system, among which hydroxyl might play the most important role. The material composition ratio, common anion and humic acid all had some influences on the catalytic efficiency. A total of five intermediates were found in the KSM/PS oxidation system, and six oxidation pathways, which were hydroxylation, dehydrogen, dechlorination, dehydration, decarboxylation, and C-N bond breakage, might be involved in the reaction process. Several highly toxic oxidation products that should be paid attention to were also proposed.

The Erguna River, a Sino-Russian transboundary river, is vital for regional ecology, but land use impacts on its water quality remain unclear. This study aimed to reveal their response relationship. Using ArcGIS/ENVI, it classified land use in 2010 and 2016 into six types, and applied Pearson correlation to 10 monitoring sections’ water quality data. Results showed land use–water quality correlations were temporally and spatially variable: correlations weakened with increasing buffer distance, with the strongest associations within 1000 m. From 2010 to 2016, grassland shifted from a positive (water-purifying) to negative (pollutant-source) impact on water quality (BOD₅ and arsenic), which was driven by area reduction and overuse; forestland transitioned from no significant effect to a positive (pollutant-intercepting) role, attributed to area expansion. Arable and construction land showed no significant correlations with water quality, due to low proportions of construction land in cross-border areas, and arable land is mostly distributed in areas far from the riverbank. This study provides critical scientific support for transboundary water resource cooperation and targeted ecological management of the Erguna River Basin.