To explore the effect of elevated CO₂ concentrations ([CO₂]) on phosphine formation in paddy fields, the matrix-bound phosphine (MBP) content, different phosphorus fractions and various carbon forms in soil samples from rice cultivation under varying CO₂ concentrations of 400 ppm, 550 ppm and 700 ppm by indoor simulation experiment were determined. This study showed that MBP concentration did not increase significantly with elevated [CO₂] over four-week cultivation periods of rice seedlings, regardless of soil layers. MBP had a significant positive correlation with total phosphorus (TP) and inorganic phosphorus (IP), and multiple stepwise linear regression analysis further indicated that MBP preservation in neutral paddy soils with depths of 0–20 cm may have been due to conversion from FeP and CaP. Based on redundancy analysis and forward selection analysis, speculated that the formation of MBP in the neutral paddy soils as the response to atmospheric elevated [CO₂] was due to two processes: (i) FeP transformation affected by the changes of soil respiration (SCO₂) and TOC was the main precursor for the production of MBP; and (ii) CaP transformation resulting from variation in HCO₃⁻ was the secondary MBP source. The complex combination of these two processes is simultaneously controlled by SCO₂. In a word, the soil environment in the condition of elevated [CO₂] was in favor of MBP storage in neutral paddy soils. The results of our study imply that atmospheric CO₂ participates in and has a certain impact on the global biogeochemical cycle of phosphorus.

The negative effect of carbonate on the rate and extent of bioreduction of aqueous U(VI) has been commonly reported. The solution pH is a key chemical factor controlling U(VI)ₐq species and the Gibbs free energy of reaction. Therefore, it is interesting to study whether the negative effect can be diminished under specific pH conditions. Experiments were conducted using Shewanella putrefaciens under anaerobic conditions with varying pH values (4–9) and bicarbonate concentrations ([CO32−]T, 0–50 mmol/L). The results showed a clear correlation between the pH-bioreduction edges of U(VI)ₐq and the [CO32−]T. The specific pH at which the maximum bioreduction occurred (pHₘbᵣ) shifted from slightly basic to acidic pH (∼7.5–∼6.0) as the [CO32−]T increased (2–50 mmol/L). At [CO32−]T = 0, however, no pHₘbᵣ was observed in terms of increasing bioreduction with pH (∼100%, pH > 7). In the presence of [CO32−]T, significant bioreduction was observed at pHₘbᵣ (∼100% at 2–30 mmol/L [CO32−]T, 93.7% at 50 mmol/L [CO32−]T), which is in contrast to the previously reported infeasibility of bioreduction at high [CO32−]T. The pH-bioreduction edges were almost comparable to the pH-biosorption edges of U(VI)ₐq on heat-killed cells, revealing that biosorption is favorable for bioreduction. The end product of U(VI)ₐq bioreduction was characterized as insoluble nanobiogenic uraninite by HRTEM. The redox potentials of the master complex species of U(VI)ₐq, such as (UO2)4(OH)7+, (UO2)2CO3(OH)3−, and UO2(CO3)34−, were calculated to obtain insights into the thermodynamic reduction mechanism. The observed dynamic role of pH in bioreduction suggests the potential for bioremediation of uranium-contaminated groundwater containing high carbonate concentrations.

Recently, a novel method for carbon capture and storage has been proposed, which converts gaseous CO2 into aqueous bicarbonate ions (HCO3−), allowing it to be deposited into the ocean. This alkalinization method could be used to dispose large amounts of CO2 without acidifying seawater pH, but there is no information on the potential adverse effects of consequently elevated HCO3− concentrations on marine organisms. In this study, we evaluated the ecotoxicological effects of elevated concentrations of dissolved inorganic carbon (DIC) (max 193 mM) on 10 marine organisms. We found species-specific ecotoxicological effects of elevated DIC on marine organisms, with EC50-DIC (causing 50% inhibition) of 11–85 mM. The tentative criteria for protecting 80% of individuals of marine organisms are suggested to be pH 7.8 and 11 mM DIC, based on acidification data previously documented and alkalinization data newly obtained from this study. Overall, the results of this study are useful for providing baseline information on ecotoxicological effects of elevated DIC on marine organisms. More complementary studies are needed on the alkalinization method to determine DIC effects on seawater chemistry and marine organisms.

There is less research on the hydrological system and its destruction processes mechanism in the mining areas, especially combined application of isotope technology and chemical signals, which is a key scientific problem that need to be solved. This study takes Jinci spring area in Shanxi as a case study. It is based on the data of hydrology and mining condition from 1954 to 2015, combining monitoring experiments, O18, D, S34 and N15 tracing, chemical and model simulation. This study investigates the hydrological regularity and impacts of mining activities on water quantity and quality, and reveals the destruction process of hydrological system. The results show that: (1) Water chemical type shows an evolutionary trend of HCO3−-Ca2+-Mg2+→SO42--HCO3--Ca2+-Mg2+→SO42--Ca2+-Mg2+, due to the influence of exploitation and fault zones. Isotope tracer shows that mine pit water is formed by a mixture of pore water, karst water and surface water. (2) Although precipitation and seepage have a certain impact on the reducing of groundwater quantity, over-exploitation of water resource is still the main reason for reducing of groundwater quantity. Under the conditions of keeping the exploitation intensity at the current level or reducing it by 10%, groundwater level shows a declining trend. Under the condition of reducing it by 30%, groundwater level starts to rise up. When reducing by 50%, groundwater level reaches its highest point. Coalmining changes the runoff, recharge and discharge paths. (3) From 1985 to 2015, Water quality in the mining area is worsening. Ca2+ increases by 35.30%, SO42− increases by 52.80%, and TDS (Total Dissolved Solid) increases by 67.50%. Nitrates come from the industrial and domestic wastewater, which is generated by mining. The percentage of groundwater coming from gypsum dissolusion is 67.51%, and the percentage from coal measure strata water is 34.49%. The water qualities of river branches are generally deteriorated.

The extensive use of reclaimed wastewater (RW) as a source of urban landscape pond replenishment, stimulated by the lack of surface water (SW) resources, has raised public concern. Greater attention should be paid to pond sediments, which act as ‘sinks’ and ‘sources’ of contaminants to the overlying pond water. Three ponds replenished with RW (RW ponds) in three Chinese cities were chosen to investigate 22 indices of sediment quality in four categories: eutrophication, heavy metal, ecotoxicity and pathogens risk. RW ponds were compared with other ponds of similar characteristics in the same cities that were replenished with SW (SW ponds). Our results show a strong impact of RW to the eutrophication and pathogenic risks, which are represented by organic matter, water content, total nitrogen, total phosphorus and phosphorus fractions, and pathogens. In particular, total phosphorus concentrations in the RW pond sediments were, on average, 50% higher than those of SW ponds. Moreover, the content of phosphorus, extracted by bicarbonate/dithionite (normally represented by BD-P) and NaOH (NaOH-P), were 2.0- and 2.83-times higher in RW ponds, respectively. For pathogens, the concentrations of norovirus and rotavirus in RW pond sediments were, on average, 0.52 and 0.30- log times those of SW ponds. The duration of RW replenishment was proved to have a marked impact on the eutrophication and pathogens risks from sediments. The continued use of RW for replenishment increases the eutrophication risk, and the pathogens risk, especially by viral pathogens, becomes greater.

Temperate highland peat swamps on sandstone (THPSS) are unique state and federally protected ecological communities. THPSS is a higher level classification which is comprised of multiple swamp communities which include Blue Mountains Swamps and Newnes Plateau Shrub Swamps. The Blue Mountains has a string of urban settlements surrounded by large expanses of undisturbed natural vegetation which have varied degrees of protection ranging from state forests to World Heritage national parks. This study investigated aquatic invertebrates from seven THPSS within the Greater Blue Mountains area. Four swamps drain catchments with varying degrees of urban development and associated impervious surfaces, and three swamps have non-urban, naturally vegetated catchments. Water chemistry of non-urban swamps was acidic (mean pH 4.70) and dilute (mean EC 26.7 uS/cm) and dominated by sodium and chloride ions with most other major ions at low concentrations often below detection limits (Belmer et al. 2015). In contrast, urban swamps had higher pH (mean 6.60) and salinity (mean 153.9 uS/cm) and were dominated by calcium and bicarbonate ions (Belmer et al. 2015). Aquatic macroinvertebrate abundance, family richness and % EPT taxa were all found to be lower within urban swamps when compared to non-urban swamps. These results support the hypothesis of Belmer et al. (2015) that urban runoff within THPSS catchments is affecting the condition of their aquatic ecosystems.

The Subaé river watershed is considered one of the most critical Pb-impacted environments in Brazil and around the world, due to pollutant dispersion during 33 years of lead ore purification in Santo Amaro da Purification. Severe damages have been reported in biota and population, which depends on the Subaé river watershed quality for agriculture, fishing, and shellfish harvesting. This study aims to understand the geochemical characteristics and dynamics of the river close to the former Pb smelter. The river was sampled at eight sites upstream and eight sites downstream the smelter, near the estuary in the Todos os Santos Bay, six times during a year. Immediate analyses were performed by multiprobe. Major ions were measured by chromatography, dissolved metals by ICP-OES in the filtrated samples (0.45 μm), and particulate metals > 0.45 μm by EDX spectrometry. The ions Na⁺ and HCO₃⁻ are dominated in the river. Most of the samples (47.6%) were classified as sodic, due to oceanic saline intrusion during tide. Despite the high pollution caused by the smelter from 1960 to 1993, still observed in the surrounding soils, dissolved and particulate metals in the river remained low in all sites during the entire year. Only Cu presented some concentration above the threshold of the Brazilian regulations. The discharge of metals by the river into the Todos os Santos Bay appears to be low for Pb and Zn (2.2 and 14.3 kg km⁻¹ year⁻¹, respectively), but higher for Cu comparatively to other worldwide bays.

Several efforts have been carried out to present an efficient method for PMS activation. This work presented the use of UVC-LEDs (light emitting diodes) and US (ultrasound) to activate PMS for decolorization of Direct Orange 26 (DO26). The performance of UVC-LEDs/US/PMS process was effective in a broad range of pH (3.0–9.0). Complete decolorization was obtained in only 12 min in pH = 7.0 and 1.5 mM PMS. Bicarbonate and nitrite ions showed inhibitory effect on decolorization while sulfate, chloride, and nitrate had no significant effect on the performance of the process. Transition metals in homogenous (Fe²⁺ and Co²⁺) and heterogeneous forms (Fe₃O₄ and Co₃O₄) accelerated decolorization in UVC-LEDs/US/PMS system. The presence of turbidity declined the performance of UVC-LEDs/US/PMS through the prevention of PMS activation by UV and US. Compared to other oxidants (S₂O₈²⁻, H₂O₂ and 2Na₂CO₃.3H₂O₂), PMS proved the higher function in decolorization of DO26 in UVC-LEDs/US/oxidant system. Scavenging experiments showed that ¹O₂, HO•, and SO₄•⁻ contributed in the degradation of DO26. Moreover, the UVC-LEDs/US/PMS system could markedly increase the biodegradability of real textile wastewater. These results promised an effective process for degradation of organic pollutants from aquatic environment.

Coalbed natural gas (CBNG) is an important unconventional natural gas resource with large reserves in China and receives much attention these years. The CBNG production is accomplished by extracting large volumes of produced water from the aquifer. The CBNG-produced water is commonly managed by discharging into nearby disposal ponds in the Southern Qinshui Basin (SQB), which provides an opportunity for water source for nearby irrigation, livestock, wildlife, and human drinking water. However, utilization of this nontraditional water source in the SQB is hindered by limited knowledge of water quality, practically oxidation/reduction potential (OPR), electrical conductivity (EC), sodium adsorption ration (SAR), and trace element chemistry data. The objective of this study was to collect CBNG-produced water samples at discharge points in the SQB and investigate their water quality principally, including physicochemical parameters, major ions parameters, and trace element parameters. Discharge points were sampled from five main CBNG blocks in the SQB including SZ, ZZ, FZ, CZ, and PZ blocks from July 31, 2013 to August 11, 2014. A composite geochemical data was created with the test results from 145 produced water samples, resulting in information on 40 constituents/parameters. The resulting constituents/parameters were compared to common water use criteria of China to determine possible beneficial uses. Results suggest that the CBNG-produced waters from SQB are characterized by dominated Na-HCO₃ type waters, with approximately 12% Na-SO₄ and Na-Cl type waters. The observed TDS ranges from 615 to 4376 mg/L with 91% are less than 3000 mg/L, and Na⁺ and HCO₃⁻ are the dominating determinants of the TDS content. The EC values vary from 930 to 3844 μS/cm, ranging from class 3 to class 5 based on the suitability for irrigation. The CBNG-produced waters in SQB generally exhibit higher SAR values (avg. 41.98). Among the 25 detected trace elements in CBNG-produced waters from SQB, elements of environmental concerns include aluminum, iron, selenium, barium, manganese, nickel, and plumbum because their concentrations exceed the related Chinese regulatory standards for human drinking. The commonly constituents exceeding standards for human drinking water, livestock water, poultry water, and irrigation water include fluorinion, pH, and TDS. Besides, targeted reduction of SAR and EC also needs to be treated for most of the produced waters if used for irrigation. In contrast, the CBNG-produced waters in SQB are the most suitable for livestock water, because approximately 88% of the CBNG-produced waters are suitable for livestock drinking if the fluorinion is reduced.

To obtain an economical and effective adsorbent for fluoride removal, lanthanum-loaded pomelo peel biochar (PPBC-La) was synthesized using a facile approach. The batch adsorption experiments were investigated to determine adsorbent performance. The PPBC-La and its pristine biochar (PPBC) were characterized by scanning electronic microscopy (SEM), zeta potential, Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) methods. Experimental results showed that the adsorption data were described well by the pseudo-second-order kinetic and Freundlich isotherm models. The maximum fluoride adsorption capacity for PPBC-La was found to be 19.86 mg/g at 25 °C and pH 6.5. The PPBC-La worked well at pH 2.4–9.6 and carried positive charge at pH < 5.8. The presence of SO₄²⁻, Cl⁻, and NO₃⁻ had a slight effect on fluoride uptake except HCO₃⁻ and PO₄³⁻. The real groundwater study testified that 9.8 mg/L of fluoride was removed effectively at 1.0 g/L of dosage and pH 5.2. The regeneration results revealed that the PPBC-La had a good reusability. According to FTIR, XPS analysis and the anion exchange experiment, anions (NO₃⁻ and OH⁻) exchange with fluoride ions was mainly responsible for fluoride adsorption.