Composition Of Rainwater Research Articles

Soil moisture and water redistribution patterns in white oak (Quercus alba) saplings and trees in fragmented urban woodlands

In the midwestern United States, models predict extended summer heatwaves and increasingly frequent and prolonged drought conditions. In the Chicago region, the potential for large-scale mortality of white oak trees (Quercus alba) coupled with the ongoing decline of white oak sapling recruitment are major concerns for researchers and practitioners. In this study, we determined the sources of water used by mature white oak trees and saplings in three qualitatively different sites within a remnant oak forest in Chicago during the 2021 drought. We investigated soil moisture dynamics (volumetric water content, VWC) and water isotope composition of leaf tissues (δD, δ18O), rainwater, and groundwater. These data were linked to sapling height (proxy for biomass) and ectomycorrhizal (ECM) functional types. We predicted that: (i) mature oak trees use deeper water sources and conducted hydraulic redistribution (HR), and (ii) mature trees shared water with saplings during dry periods via long-distance ECM functional types. Soil moisture decreased progressively from June to October (spring to fall), with August and September having the lowest moisture (<20 % VWC). Following rainfall recharge, temporal patterns of soil moisture showed gravity drainage and then ongoing stair-stepwise drawdown consistent with plant evapotranspiration. Leaf δD and δ18O values in mature trees and saplings were consistent with water uptake from rainfall and subsequent enrichment via evapotranspiration. In two sites, mature trees and saplings demonstrated distinct δD: δ18O slopes, with mature trees more enriched than saplings. In the third site, mature trees and saplings δD: δ18O slopes overlapped but here, the ECM community was dominated by contact-type ECM and sapling height increased with distance from the mature oak. Our findings indicate that HR was not a component of site ecohydrology, and future climate conditions may present increasing challenges for white oak recruitment as both mature trees and saplings compete for limited rainfall-derived soil moisture.

Chemical and isotopic composition of rainwater in the eastern Yucatan peninsula, Mexico

Given that rain is the component of precipitation that reaches the surface of the earth, and aiming to contribute to the global efforts of rainwater monitoring, we present information regarding the origin of ions and their relationship with isotopic patterns and the source of moisture for rainwater in the Mexican Caribbean, which not only may be useful for pollution and atmospheric studies, but also for estimating groundwater recharges, understanding dust nuisances, and offering information about water quality for rainwater harvesting. In this paper, we describe the chemical composition of rainwater in terms of major ions, isotopic composition, and the most probable sources of moisture in the Caribbean coastal zone of Mexico, considering the three main climatic seasons in this area. The chemistry of rainwater displayed a noticeable influence from sea-salt spray, land-blown dust, and anthropogenic impacts such as agriculture and biomass burning. We identified the predominant terrestrial origin of calcium, namely anthropogenic contributions of sulfates and nitrates, plus potassium from sea spray and anthropogenic emissions. The local meteoric water line is δ2H = 8.2 δ18O + 13.8 (R² = 0.9601) suggesting enrichment due to evaporative losses, various moisture sources and local climatic effects. Although isotope composition was not different by site, it was by season, as opposed to water chemistry. We conclude that the water chemistry responds to the local conditions of the air column below the clouds, while the isotope composition is influenced by the origin of moisture and the physical conditions in which water evaporates and condenses as well.

Alterations of throughfall and stemflow chemistry by vegetation in China: Insights from a machine learning based meta-analysis

In vegetated ecosystems, the chemical composition of rainwater is strongly altered after gross rainfall (GR) partitioning into throughfall (TF) and stemflow (SF) before entering the under-canopy soil. However, quantitative syntheses of the chemical alteration are lacking, rendering an insufficient comprehension of its overarching patterns and magnitudes. Here, we furnish a comprehensive dataset related to the chemistry of rainfall partitioning by vegetation in China compiled from 131 peer-reviewed papers published between 1988 and 2023. A meta-analysis was conducted to assess the chemical alterations as GR partitions into TF and SF. We discerned a marked acidification effect in SF but not in TF, with the pH being significantly lower in SF than in GR. Additionally, we observed a persistent concentration-based chemical enrichment of total nitrogen (TN) and total phosphorous (TP) as well as 12 commonly reported nutrient-ions (except for Cu2+) in both TF and SF, with SF generally exhibiting a greater degree of chemical enrichment than TF. Using a machine learning method (boosted regression trees), we identified the key drivers from twelve biotic and abiotic predictor variables on the effect sizes of pH, TN, TP, and each nutrient-ion, and further elucidated the prevalent non-linear partial effects of these key drivers on the magnitude of chemical alterations. For instance, three predictor variables were identified as key drivers for the effect sizes of TN for SF, with a descending relative influence of diameter at breast height (56.9 %; positive effect), Human Footprint (16.5 %; positive), and bark texture (14.0 %; stands with mixed bark textures exerting a greater impact). Our study has significant implications for an accurate estimation of nutrient budgets in vegetated ecosystems throughout China, contributes to a deeper understanding of the intricate ways in which biotic and abiotic predictors influence chemical alterations in rainfall partitioning, and aids in evaluating forest health and developing sensible forest management strategies.

Chemical composition of cloud and rainwater at a high-altitude mountain site in western India: source apportionment and potential factors.

This study focuses on the chemical composition of cloud water (CW) and rainwater (RW) collected at Sinhagad, a high-altitude station (1450m AMSL) located in the western region of India. The samples were collected during the monsoon over two years (2016-2017). The chemical analysis suggests that the concentration of total ionic constituents was three times higher in CW than in RW, except for NH4+ (1.0) and HCO3- (0.6). Compared to RW, high concentrations of SO42- and NO3- were observed in CW. The weighted average RW pH (6.5 ± 0.3) was slightly more alkaline than CW pH (6.1 ± 0.5). This can be attributed to the high concentrations of neutralizing ions such as nss-Ca2+, nss-Mg2+, K+, and NH4+, indicating the greater extent of wet scavenging during rainfall. These ions counteract the acidity generated by SO42- and NO3-. A high correlation between Ca2+, Na+, K+, NO3-, and SO42- makes it difficult to estimate the contribution of SO42- from different sources. Anthropogenic sulfur emissions and soil dust significantly influence the ionic composition of clouds and rain. Positive matrix factorization (PMF) was used to identify the contribution of different sources to the samples. In the CW, the extracted factors were cooking and vehicles, aging sea salt, agriculture, and dust. In RW, the factors were industries, cooking and vehicles, agriculture and dust, and aging sea salt. The findings of this study have significant implications for the monsoon build-up, ecosystems, agriculture, and climate change.

Investigating the convective transport possibilities of lower-atmospheric pollutants to the UTLS region using rainwater and aerosol chemical characterization

Various attempts using different platforms to understand the chemical composition of the Asian Tropopause Aerosol Layer (ATAL) have concluded that it primarily consists of nitrate (NO3−) aerosols. Recent in-situ measurements from aircraft flying through ATAL have suggested that ammonia (NH3) pollution from Asia could serve as the precursor for nitrate aerosols in ATAL through gas-to-particle formation after undergoing convective uplift to the Upper Troposphere and Lower Stratosphere (UTLS) regions. In this study, we aimed to investigate the potential pathways of convective transport of lower-atmospheric pollutants by analysing the chemical composition of rainwater and aerosols in a highly convective region, Kolkata (Head Bay of Bengal), India. We utilized the PILS-IC system established at Kolkata Camp Observatory of the National Atmospheric Research Laboratory (KCON). The analysis revealed a significant dominance of NH4+ and NO3− ions in both rainwater and aerosol samples during the monsoon and post-monsoon seasons, with the dominance increasing during the post-monsoon season. Air mass trajectories indicated a clear influence of the Indo-Gangetic Plain (IGP) region during the post-monsoon season, which is well-known for its dense agricultural activities and industries. High concentrations of NH3 even at higher altitudes, have been observed in Atmospheric Infrared Sounder (AIRS) measurements. Moreover, using Outgoing Longwave Radiation (OLR) and vertical wind as proxies for tropical deep convection and updrafts/downdrafts, respectively, we found evidence supporting the possibility of convective transport of these lower-atmospheric pollutants to the UTLS regions during the monsoon season. In conclusion, this study provides evidence for the potential convective transport of lower-atmospheric pollutants, including NH3 and other precursor gases, to higher levels. These pollutants could partially serve as the source of nitrate aerosols in the ATAL through gas-to-particle formation processes.

Chemical Composition and Health Risk Assessment of Rainwater Around a Cement Factory in Ibeshe, Ogun state

Chemical Composition and Health Risk Assessment of Rainwater Around a Cement Factory in Ibeshe, Ogun state

Assessing the determinants of scale effects on carbon efficiency in China's wastewater treatment plants using causal machine learning

The debate over the merits of centralized versus decentralized wastewater treatment plants (WWTPs) has gained prominence considering pressing sustainable development objectives and the need to reduce greenhouse gas (GHG) emissions. This highlights the importance of innovative analytical tools to shape forthcoming policies. Using causal machine learning, we evaluate the impact of WWTP scale on GHG emission intensities and investigate contributing factors. Results show GHG intensity typically decreases as WWTPs scale up. However, this trend varies based on regional environmental, economic, and infrastructure elements. Specifically, regions with fewer industrial wastewater contributions, increased rainwater composition, and elevated temperatures show smaller scale effects. This suggests limited GHG reductions from merely expanding WWTPs in such areas, as the benefits of handling fluctuating inflow volumes, tackling heavy pollution, and operating in cooler conditions offered by larger WWTPs are compromised. This research lays the foundation for comprehensive models promoting sustainable wastewater treatment strategies.

Economic and Industrial Development SignificantlyContribute to Acidity and Ionic Compositions of Rainwaterin China

To achieve a holistic understanding of the intricate interactions among human activities, atmospheric chemistry, and acid rain in China, a rigorous analysis of rainwater chemistry was made using a dataset comprising 2656 data points from 24 sites. The main cation and anion in the chemical composition of precipitation were Ca2+ and SO42− in China, with an average concentration of 169.9 μeq/L and 135.4 μeq/L, respectively. Acid rain generally occurs in southern cities such as Shenzhen, Guangzhou, Zhuhai, Xiamen, and Chongqing. There were evident regional disparities in acidity and ion concentrations in rainwater, with an increase in acidity and a decrease in ion concentrations from north to south across China. Utilizing positive matrix factorization, the study found that NH4+, SO42−, and NO3− mainly originated from anthropogenic sources such as fossil fuel combustion, vehicle exhaust emissions, agricultural fertilization, and industrial emissions (as reflected by F3 and F4). Ca2+ mainly stems from crustal factors, including industrial dust and natural crust (as represented by F1 and F4). Na+ and Cl− were traceable from marine sources (as reflected by F5), while Mg2+ originated from crust origin (as presented by F1). K+ was mainly derived from a mixed source of crust, marine, and biomass burning (as indicated by F2 and F3). The correlation analyses showed that SO42− and NO3− showed significant correlations with GDP and population. F− was associated with wastewater, which may be linked to the production of brick and tiles from clay with high fluoride contents. The pH was negatively related to industrial wastewater. Long-term analysis of precipitation chemistry in four cities suggested a clear decrease in the proportion of SO42− but a considerable increase in the proportion of NO3− in anions in metropolitans of Shanghai and Chongqing due to the environmental measures that targeted reducing sulfur dioxide (SO2) emissions and increase of vehicles. This showed that pollution control strategies had an impact on precipitation ion concentrations. These results can conclude that economic and industrial growth, which will increase energy consumption, utilization of coal combustion, and a subsequent rise in pollutant emissions, can contribute to the change in the chemical compositions of rainwater and the exacerbation of acid rain.

Caracterização química e rateio de fontes de águas pluviais na Reserva Biológica de Cuieiras, Amazônia central, Brasil

ABSTRACT The Amazon rainforest plays a crucial role in the global climate system, acting as a major carbon sink and influencing regional and global weather patterns. Understanding the chemical composition of rainwater is essential for assessing the impact of anthropogenic activities, such as deforestation and industrial emissions, on atmospheric chemistry and hydrology. This work aimed to characterize the chemical composition of rainwater in a biological reserve of primary forest in the central Brazilian Amazon at 60 km of a large urban center. Rainwater samples were collected from March 2008 to March 2010 and were analyzed by ion chromatography, ICP-MS, and TOC-V. This is the only and longest rainfall monitoring carried out in this reserve. The results showed that the rainwater is rich in organic carbon (TOC), representing 77% of total carbon. The most abundant ions were NH4 + and Cl-. Few elements were detected, with emphasis on Al and Fe. In the dry season, most species were enriched. The lower amount of precipitation, biomass burning and the lower capacity to remove pollutants from the atmosphere are the main reasons for this seasonal difference. Only 7% had characteristics of acid rain (pH &lt; 4.5), with acidity dominated by NO3 -. A positive matrix factorization indicated contribution of sources: crustal (48%), secondary aerosol (26%), biogenic (22%), and industrial emissions (4%). Although the forest has primary characteristics, the proximity to the urban center indicates some anthropogenic influence on the chemical composition of rainwater.

Isotopic study of rainfall and definition of local meteoric water lines: Case of the rainfall stations of the city of Bangui in Central African Republic

The study of the isotopic composition of rainwater discussed in this article allows isotopic characterization of rainfall recorded in the Bangui region over 11 years at two stations. It will highlight the relationships between isotopes, climatic parameters, and temporal variation before defining the local meteoric line, which constitutes the reference point for the region. The results obtained after a follow-up of eleven years without interruption showed two major physical effects, the effect of the rainfall influences more strongly the composition in isotopes, the contents in isotopes vary inversely with the precipitation. For example, heavy rainfall in August and September saw a strong depletion of δ¹⁸O and δ²H contents. These values reach up to -4.96‰ for δ¹⁸O and -28.3‰ for δ²H. Similar, although weaker, effects are observed for July and October precipitation. We also note that the isotope contents at the Bangui University station are lower than those measured at the Bangui Sodeca station located at 386 m altitude on the Lower Ubangi Hill, which is similar to a pseudo-altitude effect. The evolution of stable isotope content in water as a function of meteorological parameters (temperature, rainfall, altitude) has allowed us to determine a local meteorological line for the city of Bangui from two measuring stations defined as follows: δ2H = 7.6 × δ18O + 10.4 (R2 = 0.9909) Université de Bangui, δ2H = 8.4 × δ18O + 12.5 (R2 = 0.9909) Bangui-Sodeca and δ2H = 7.9 × δ18O + 11.3 (R2 = 0.9939) Bangui local meteoric water lines.

An investigation of heavy metals concentration in rainwater and their effects on human health in Kurdistan Region, Iraq

One possible source of fresh water is rainfall. Nonetheless, the natural composition of rainwater may change due to air pollution in any areas. The Kwashe and Gara in the Duhok Governorate, in the Kurdistan region of Iraq, was selected as the study areas. Heavy metals concentration of rainwater was investigated. Seven samples were taken during rainy January and February 2023 for this investigation, and a statistical analysis was carried out to identify the factors influencing the quality of the rainwater. The concentrations of heavy metals (Zn, Pb, Ni, Cr, Cd, Mn, Cu, Fe, and Co) were measured with an atomic absorption spectrophotometer (AAS) and compared to WHO standards. The purpose of the study was to compare the heavy metal content of study area rainwater to WHO standards in order to determine the effects of these metals on community members' individual health as well as the environment. The heavy metal concentrations dropped in the following order: (Zn, Pb, Ni, Cr, Cd, Mn, Cu, Fe, and Co in Kwashe and Zn &gt; Ni &gt; Cu &gt; Pb &gt; Cr &gt; Fe &gt; Mn &gt; Cd &gt; Co in Gara). The following heavy metals are within the WHO's permissible limit: Fe, Cu, Zn, Mn, and Co; the others exceeded it. The results indicate that the rainwater sources in the study areas are unsafe and unfit for human consumption. Because of this, rainwater from research areas needs to be treated before drinking in order to prevent Pb, Cd, Ni, and Cr-related health problems.

Bi-decadal trend of atmospheric emissions from thermal power plants in Mainland Southeast Asia: Implications on acid deposition and climate change Mitigation

Steady increase in electricity generation and heavy reliance on coal in Mainland Southeast Asia (M-SEA) create huge pressure on the environment. This study used information collected from individual thermal power plants (TPPs) in M-SEA to calculate emissions of air pollutants and greenhouse gases (GHG) for 2010, 2015 and 2019. The emissions were projected to 2030 following the latest national Power Development Plans. The emission results were analyzed in relation to the power development by country and fuel type, and environmental impacts. The region collective annual TPP emissions in 2019, in Gg/yr, were 27 PM2.5, 77 PM10, 0.7 BC, 4.9 OC, 255 SO2, 451 NOx, 91 CO, 12 NMVOC, 0.4 NH3, 260 CO2, 13 CH4, and 26 N2O. Coal-fired TPPs dominated the emissions of most species while NG-fired contributed the largest amounts of NH3 and CH4. Bi-decadal increase in energy production from TPPs of nearly 3 times is accompanied by 2.7 times increase in emissions. The 2010–2019 period saw average emissions increase by 1.9 times (TPPs' energy production increased 1.6 times), slightly higher than the rate of 1.4 times projected for 2019–2030 (double TPPs’ energy production). The current intrusion rate of renewable energy accompanied by phasing-out of old TPPs are still by far insufficient to reverse the emission trend. Aggressive power development in Vietnam with its heavy coal reliance made it the largest emitter in 2019 and the projected for 2030, followed by Thailand. Spatially, higher emissions are seen over locations of large coal-fired TPPs in Vietnam and Thailand. Available rainwater composition monitoring data showed higher deposition amounts of sulfate and nitrate in areas located near or downwind of large TPPs. Significant GHG emissions projected for TPPs in 2030 indicated that TPPs should be the priority for emission reduction to achieve Nationally Determined Contribution targets. Emission database produced by this study can be used in dispersion modeling studies to assess impacts of TPPs on air quality, health, and acid deposition.

Exploring the size-dependent dynamics of photosynthetic cells in rainwater: The influence of atmospheric variables and rain characteristics

The presence of microalgae in the atmosphere raises health and environmental concerns. Despite recent scientific advances, our knowledge of the origins and dynamics of photosynthetic cells in relation to atmospheric processes is limited due to a lack of empirical data. To address this gap, we conducted a one-year survey, collecting and analyzing rainwater samples. This study proposes to investigate the temporal dynamics of photosynthetic cells based on their size in combination with a unique dataset of variables of interest: type of rain and its characteristics, local meteorology, concentrations of inorganic chemical species, and long-range air mass transport. The analysis of the biochemical composition of rainwater, along with its correlation with the origin of air masses using ions as tracers, provides evidence of the long-range transport of photosynthetic cells. Additionally, our study reveals distinct removal mechanisms from the atmosphere for photosynthetic cells depending on their size. Our results suggest that convective events with high-intensity rainfall led to the efficient removal of medium-sized photosynthetic cells (4–15 μm) from the atmosphere. However, removal mechanisms for small (<4 μm) and large-sized cells (>15 μm) are not influenced by microphysical rainfall characteristics and seem to be governed by different atmospheric processes: dry deposition is proposed to be a significant mechanism for the removal of large-sized photosynthetic cells, while small-sized cells detected in rain are correlated with the horizontal wind speed and duration of rainfall, particularly during stratiform events. This implies that the removal of photosynthetic cells from the atmosphere is strongly influenced by environmental variables, which are expected to vary in response to global change. Therefore, it is crucial to enhance the monitoring of photosynthetic cells in relation to atmospheric processes and investigate the potential impact of the dissemination of genetic material from distant sources on recipient ecosystems.

Chemical composition of rainwater at three sites in Kandy/Peradeniya, Sri Lanka, and its effect on air pollution

The composition of atmospheric precipitation, an important criterion considered to account for air pollution, is usually determined with respect to wet precipitation and dry precipitation, or as bulk deposition in combined form. Although rainwater quality should be continuously monitored in order to understand the extent of air pollution, such investigation lacks attention in Sri Lanka. This study was thus aimed to determine the composition of bulk deposition collected weekly for a period of eleven months from February to December 2019, in three sampling locations; namely the University of Peradeniya (UOP), Kandy City Central (KCC) and Polgolla. Parameters quantitatively determined, rainfall, pH, conductivity, salinity, total dissolved solids (TDS), hardness, anions: Cl−, NO3−, SO42−, F−, PO43− and trace metals: Zn, Fe, Al, Mn, Cu, Pb, Cr, using standard analytical methods indicated that the KCC site showed the overall highest degree of air pollution followed by UOP and Polgolla sites. Nevertheless, no acid rain occurrences were observed during the sampling period in any of the three sites according to pH measurements. Anions of bulk deposition showed the sequence Cl−> SO42− > NO3−in all three sites with Cl−and SO42- being dominant anions. Furthermore, trace metals of bulk deposition showed the sequence, Zn > Fe > Al > Mn > Cu > Pb, in all three sites. Bulk precipitation data analyzed using Pearson correlation showed high positive significant correlations between conductivity and salinity, conductivity and TDS, and salinity and TDS, among all water quality parameters. Among trace metals, the highest positive significant correlation was found to be between Fe and Mn at the UOP Site. The highest positive significant correlation was between Al and Zn at the KCC site. No correlation between trace metals was found at the Polgolla Site.

Temporal and spatial shifts in the chemical composition of urban coastal rainwaters of Kuwait: The role of air mass trajectory and meteorological variables

The rainwater chemistry encompasses the signatures of geogenic and anthropogenic processes along the regional air mass movement apart from the local sources. The predominance of dust events and anthropogenic emissions in arid regions facilitate new particle formation. Further, rain events of different seasons depict moisture sources from diverse regions reflecting variation in the regional geochemistry with respect to seasons. Hence, to characterize the geochemical composition of rainwater, the study has focused on an integrated approach by considering regional transport, meteorological components and possible local sources. A total of 74 rainwater samples were collected from 27 rain events in 2018, 2019, and 2022, representing urban coastal areas of Kuwait predominantly of Ca-SO4-HCO3 type. The average pH and electrical conductivity of the rainwater were 7.18 and 140 μS/cm, respectively. The sea salt fractions calculated relative to Kuwait seawater ranged from 25.6 to >100 %, with higher values attributed to anthropogenic sources. Sea salt fraction, ion ratios, principal component analysis and factor scores revealed the terrestrial and anthropogenic sources apart from marine contributions. In addition, new particle formation and aerosols contributed to the rainwater chemistry involving SOx, NOx, and photochemical reactions during higher relative humidity and lesser wind speed. The HYSPLIT reflected that the moisture sources were largely from western regions of the study area, and those of December and January events had long-distance travel across the Azores high originating from northeast America. The trajectories of the November events are observed to originate from the Caspian/Black Sea region in the northeastern part of Kuwait with a relatively shorter distance of travel. The rainfall samples had higher ionic concentrations, and saturated with aragonite and calcite minerals in a few locations specifically after the dust events, while the subsequent rain events were less polluted.

Quantifying source effects based on rainwater δ18O from 10-year monitoring records in Southwest China

The stable isotopic composition of rainwater (δ18Op and δDp) has been considered an effective proxy in studying atmospheric circulation and hydrological cycle processes. However, the linkage between variabilities in moisture sources and δ18Op remains poorly understood in Southwest China. Here, we utilized three long-term (10-year) δ18Op records (Beibei, Furong, and Yangkou stations) in Chongqing, Southwest China, from 2010 to 2019 A.D., integrated with a cluster analysis based on the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) to quantitatively demonstrate the close remote coupling of moisture sources and δ18Op on seasonal and interannual timescales. The clustering calculation results indicated that the percentage initial moisture source proportions of the westerlies and Asian summer monsoon have changed significantly at seasonal and interannual timescales, leading to the significant variation in δ18Op in Southwest China. Domination of westerlies and inland moisture contribution resulted in the positive δ18Op excursion in the dry season (November, December, January–April) while prevailing oceanic moisture led to the negative δ18Op excursions in the rainy season (May–October). On the interannual scale, δ18Op and d-excess exhibited a persistent positive/high trend, which is consistent with a decrease/increase in water vapor contributions from the ocean/westerly sources. Furthermore, δ18Op showed a good correlation with the Indian Ocean Dipole index, El Niño-Southern Oscillation, and the South Asian monsoon index, indicating that large-scale circulation patterns may affect regional δ18Op through their influence on moisture transport and convective activity in the source region. The long-term observation confirmed changes in moisture sources largely depend on the Westerly and Indian monsoon dynamics controlled by ocean-atmosphere circulation, supporting the effects of moisture sources on the rainwater isotopic composition.

High‐resolution stable isotope profiles from shells of the land snailPlacostylusreveal contrasting patterns between snails originating from New Zealand and New Caledonia

ABSTRACTThe stable oxygen (δ18Oshell) and carbon (δ13Cshell) isotope ratios retrieved from the carbonate shell of terrestrial gastropods can be used as an environmental proxy and are thought to reflect dietary composition and ambient climatic conditions (e.g. precipitation amount, humidity, temperature). Here, we generate high‐resolution isotopic profiles of nine modern land snails of the genusPlacostylus, collected from two locations in New Caledonia and one location in New Zealand. We found that snails from New Zealand had, on average, higher δ18Oshellvalues than their counterparts in New Caledonia, which surprisingly runs counter to the expected relationship based on the isotopic composition of rainwater between these two regions. Specimens from New Caledonia exhibit ephemeral decreases in their δ18Oshellvalues, which could be linked to extreme precipitation events in this region, while snails from New Zealand have less variation in their δ18Oshellvalues. Snails from New Zealand had, on average, slightly higher δ13Cshellthan their counterparts in New Caledonia, but a large difference in carbon isotopes was sometimes observed between snails collected at the same location. Most snails exhibit a temporal trend in their δ13Cshellvalues, indicating potential shifts in diet through to maturity.

Multi-species plantation intensifies soil water competition and groundwater depletion in a water-limited desert region

Multi-species plantation has long been applied in forestry and landscape restoration to provide better ecosystem services and functions. However, the differences in water-use patterns between mixed and pure plantations are poorly understood, especially in the arid/semi-arid artificial desert ecosystems. The stable isotope compositions (δ2H and δ18O) of rainwater, xylem water, soil water, and groundwater were analyzed over three growing seasons (2019–2021) to identify the water-use patterns of Artemisia desterorum Spreng (A. desterorum), Amorpha fruticosea (A. fruticosa) and Pinus sylvestris var. mongolica (P. sylvestris) in pure and mixed plantations in the Mu Us Sandy Land. Seasonally, there was a transference of water-use pattern from deep (moist layer and groundwater) to shallow water sources (active and stable layers) during the transition period between the dry and rainy season for both pure and mixed A. fruticosa and P. sylvestris, which was attributed to dimorphic root systems of arbor and shrub in the water-limited region. However, A. desterorum with shallower roots predominately absorbed water from the active and stable layers across the whole growing season regardless of planting pattern. Annually, the three plant species in pure stands extracted water predominantly from the stable layer (36.97%–46.16%), followed by the active layer (23.55%–36.98%). In the mixed stand, however, all the plants absorbed water mainly from the active layer (33.04%–39.44%), followed by the stable layer (30.46%–33.68%), suggesting that multi-species plantation intensifies shallow soil water competition. Additionally, the proportional contribution of groundwater to plant water uptake under mixed plantation was higher than the pure plantations, causing faster groundwater decline in the mixed stand (0.29 m yr−1) compared to pure stands (0.11–0.20 m yr−1). Our study demonstrates that multi-species plantation in the water-limited desert region intensifies soil water competition and groundwater depletion and thus adversely affects sustainable development goals.

Water sources used by artificial Salix psammophila in stands of different ages based on stable isotope analysis in northeastern Mu Us Sandy Land

Understanding the water use pattern of artificially restored vegetation is important to provide reasonable water management strategies. However, the characteristics, controls and differences of water sources of planted Salix psammophila at different developmental stages remain poorly understood. In this study, the hydrogen and oxygen isotope compositions of xylem water, soil water, and rainwater were measured and coupled with the MixSIAR model to investigate the variations and controls of water use patterns of different aged S. psammophila in a semi-arid region in northeastern Mu Us Sandy Land. Results showed that >60% of water used by 6-yr S. psammophila derived from 0 to 120 cm soil layer throughout the growing season due to the relatively shallow roots (0–100 cm). In contrast, water sources used by 12- and 18-yr S. psammophila differed markedly between the dry and rainy seasons, which were attributed to the developed dimorphic root systems and seasonal changes in soil water profile. In the dry season, 12- and 18-yr S. psammophila extracted 71.93% and 68.91% of water from 120 to 300 cm and 40–200 cm soil layer, respectively; in the rainy season, however, they both shifted main water sources to 0–120 cm soil layer (65.09% and 56.14%). The severe soil desiccation and dead roots observed in the 18-yr stand decreased the ability of old S. psammophila to extract water from the deep soil layer (200–300 cm) in the dry season. Thus, changes in the vertical distribution of roots and soil water contents controlled the seasonal water use pattern of different aged S. psammophila. Our study demonstrates that the age-dependent water use pattern of S. psammophila should be considered to implement the corresponding management measures in future afforestation plans to avoid overuse of water and maintain sustainable vegetation restoration in the water-limited desert regions.

Atmospheric Deposition around the Industrial Areas of Milazzo and Priolo Gargallo (Sicily-Italy)-Part A: Major Ions.

The chemical composition of rainwater was studied in two highly-industrialised areas in Sicily (southern Italy), between June 2018 and July 2019. The study areas were characterised by large oil refining plants and other industrial hubs whose processes contribute to the release of large amounts of gaseous species that can affect the chemical composition of atmospheric deposition As in most of the Mediterranean area, rainwater acidity (ranging in the study area between 3.9 and 8.3) was buffered by the dissolution of abundant geogenic carbonate aerosol. In particular, calcium and magnesium cations showed the highest pH-neutralizing factor, with ~92% of the acidity brought by SO42- and NO3- neutralized by alkaline dust. The lowest pH values were observed in samples collected after abundant rain periods, characterised by a less significant dry deposition of alkaline materials. Electrical Conductivity (ranging between 7 µS cm-1 and 396 µS cm-1) was inversely correlated with the amount of rainfall measured in the two areas. Concentrations of major ionic species followed the sequence Cl- > Na+ > SO42- ≃ HCO3- > ≃ Ca2+ > NO3- > Mg2+ > K+ > F-. High loads of Na+ and Cl- (with a calculated R2 = 0.99) reflected proximity to the sea. Calcium, potassium, and non-sea-salt magnesium had a prevalent crustal origin. Non-sea salt sulphate, nitrate, and fluoride can be attributed mainly to anthropogenic sources. Mt. Etna, during eruptive periods, may be also considered, on a regional scale, a significant source for fluoride, non-sea salt sulphate, and even chloride.