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Soil enzymes play a central role in carbon and nutrient cycling, and their activities can be affected by drought-induced oxygen exposure. However, a systematic global estimate of enzyme sensitivity to drought in wetlands is still lacking. Through a meta-analysis of 55 studies comprising 761 paired observations, this study found that phosphorus-related enzyme activity increased by 38% as result of drought in wetlands, while the majority of other soil enzyme activities remained stable. The expansion of vascular plants under long-term drought significantly promoted the accumulation of phenolic compounds. Using a 2-week incubation experiment with phenol supplementation, we found that phosphorus-related enzyme could tolerate higher biotoxicity of phenolic compounds than other enzymes. Moreover, a long-term (35 years) drainage experiment in a northern peatland in China confirmed that the increased phenolic concentration in surface layer resulting from a shift in vegetation composition inhibited the increase in enzyme activities caused by rising oxygen availability, except for phosphorus-related enzyme. Overall, these results demonstrate the complex and resilient nature of wetland ecosystems, with soil enzymes showing a high degree of adaptation to drought conditions. These new insights could help evaluate the impact of drought on future wetland ecosystem services and provide a theoretical foundation for the remediation of degraded wetlands. [ABSTRACT FROM AUTHOR]

This paper presents dating results of AMS 14C, 210Pb and 137Cs methods on two young peat profiles from Jinchuan Mire in southeast Jilin of China. JC1 (50-cm long) from a hummock of the mire covers 1962–2007 CE with an accumulation rate of 1.12 cm/y, whereas JCA (92-cm long) from a lawn site involves a 1000-year record with a mean sedimentation of 0.09 cm/y. Comparison of the dating results of the last 100-y part of the peat cores, chronologies based on the AMS 14C dating are most reliable, because the mobility of 210Pb and 137Cs in peat profiles causes overestimation of depositional rate with the larger errors in the deeper layers. The F14C of peat samples were significantly lower than that of the atmospheric CO 2 for the post nuclear bomb period because of three reasons: (1) uptake of old CO 2 dissolved in the water by aquatic plants during photosynthesis; (2) long-term mixing of the atmospheric CO 2 in multiple year growth of the plants; and (3) perhaps dilution effect caused by strong surface runoff. Among these factors, Factor (1) accounts for the major influence. Hence, a "bomb 14C curve" from a peat profile is necessary for determining post bomb ages. For the pre-nuclear bomb ages, acid-base-acid (ABA) treatment of a peat sample may cause an older-than-true age due to removal of organic acids produced during photosynthesis. This observation calls for detailed investigation of mechanism study and proper pretreatment of peat samples for 14C dating. The large difference of the depositional rates in the same peatland between JC1 and JCA indicates that estimation of carbon storage in a peatland should be based on the database of multiple sites rather than a couple of cores. For the same reason, one should not use a depositional rate either from a core with distance in the same peatland or from an adjacent peatland. [ABSTRACT FROM AUTHOR]

Background: Peatlands contain about 500 Pg of carbon worldwide and play a dual role as both a carbon sink and an important methane (CH4) source, thereby potentially influencing climate change. However, systematic studies on peat properties, microorganisms, methanogenesis, and their interrelations in peatlands remain limited, especially in China. Therefore, the present study aims to investigate the physicochemical properties, archaeal community, and predominant methanogenesis pathways in three typical peatlands in China, namely Hani (H), Taishanmiao (T), and Ruokeba (R) peatlands, and quantitively determine their CH4 production potentials. Results: These peatlands exhibited high water content (WC) and total carbon content (TC), as well as low pH values. In addition, R exhibited a lower dissolved organic carbon concentration (DOC), as well as higher total iron content (TFe) and pH values compared to those observed in T. There were also clear differences in the archaeal community between the three peatlands, especially in the deep peat layers. The average relative abundance of the total methanogens ranged from 10 to 12%, of which Methanosarcinales and Methanomicrobiales were the most abundant in peat samples (8%). In contrast, Methanobacteriales were mainly distributed in the upper peat layer (0–40 cm). Besides methanogens, Marine Benthic Group D/Deep-Sea Hydrothermal Vent Euryarchaeotic Group 1 (MBG–D/DHVEG–1), Nitrosotaleales, and several other orders of Bathyarchaeota also exhibited high relative abundances, especially in T. This finding might be due to the unique geological conditions, suggesting high archaeal diversity in peatlands. In addition, the highest and lowest CH4 production potentials were 2.38 and 0.22 μg g−1 d−1 in H and R, respectively. The distributions of the dominant methanogens were consistent with the respective methanogenesis pathways in the three peatlands. The pH, DOC, and WC were strongly correlated with CH4 production potentials. However, no relationship was found between CH4 production potential and methanogens, suggesting that CH4 production in peatlands may not be controlled by the relative abundance of methanogens. Conclusions: The results of the present study provide further insights into CH4 production in peatlands in China, highlighting the importance of the archaeal community and peat physicochemical properties for studies on methanogenesis in distinct types of peatlands. [ABSTRACT FROM AUTHOR]

A comprehensive and integrative view of East Asian monsoon evolution during the Holocene is still under debate, and additional high-resolution proxy records from climatically sensitive locations are requisite to solve this complex issue. In this paper, we present three well-dated mud/peat cores from a paleo-pingo depression in the Sanjiang Plain, a climatically sensitive region to monsoon variation, to reveal the paleoenvironmental history of the wetland and discuss the regional impacts from monsoon evolution. A paleolake developed in the study area before 5.5 ka BP, and a peatland initiated thereafter consequent upon the gradual shrinking of the paleolake. This transition lasted until 4.5 ka BP, when the paleolake changed entirely to a wetland. Considering the prevalent monsoon climate in the Sanjiang Plain, we suggest that the lake-to-wetland transition from 5.5 to 4.5 ka BP indicates a rapid decline of the East Asian summer monsoon in addition to autogenic basin infilling processes. Such a remarkable monsoon weakening event has been documented across northern China, and we associate this with ocean–atmosphere interactions throughout low-latitude regions. [ABSTRACT FROM AUTHOR]

The corresponding relationships between temperature, precipitation, and polycyclic aromatic hydrocarbon (PAH) concentration in a typical ombrotrophic peatland in Dajiuhu, Shennongjia, were quantitatively characterized by field sampling tests validated with simulation experiments. The PAH concentrations of peat cores in Dajiuhu peatland ranged from 262 to 977 ng·g−1, with a mean value of 536 ± 284 ng·g−1. PAHs were mainly composed of 2–3 ring PAHs, accounting for 31.7% ± 2.00% and 31.7% ± 5.00%, respectively. The concentration of PAHs in peat cores showed a significant decrease with increasing temperature, while the low molecular weight PAHs (LMW-PAHs) were more sensitive to temperature changes compared to the high molecular weight PAHs (HMW-PAHs). Besides, with the increase of quantity and velocity of leaching liquid, PAHs in peat were first transferred in the form of attached large-size particles and then gradually entered the aqueous phase. According to the IPCC projections of global warming, Dajiuhu peatland will release 956 ± 26.3 kg·°C−1 PAHs into gas phase during 2030–2052, and a conservative projection based on local temperature trends showed that 459 ± 12.6 kg·°C−1 PAHs will be released into gas phase by 2047 in Dajiuhu peatland. The projected release fluxes of PAHs in Dajiuhu peatland with precipitation volume and precipitation velocity are 381 ± 201 kg·100 mm−1 and 1052 ± 167 kg·min·mL−1, respectively, which are primarily from peat into particulate and aqueous phase. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are a kind of organic pollutants with carcinogenic, teratogenic, and mutagenic effects. This study aims to assess the effects of changes in China's socio-economic indicators represented by energy consumption and number of motor vehicles, on PAHs and black carbon (BC) deposition. For this, a 50-cm peat core from Dajiuhu peatland, Central China, was collected and divided into 50 subsamples to establish a sedimentary record of about 200 years with radioactive 210Pb. The Σ16PAH concentration ranged from 212.67 to 830.10 ng·g−1, mainly composed of 2- and 3-ring PAHs, and BC ranged from 7.89 to 36.48%. The deposition characteristics of BC first increased and then decreased from the core bottom to the top. The predominant of the carcinogenic PAHs (C-PAHs) was Dibenzo[a,h]anthracene (DBA) before 1949, and then changed to Benzo[b]fluoranthene (BbF). Ratio of Fla/Pyr, (3+4)-ring/(5+6)-ring PAHs, and BaA/(BaA+Chr), IcdP/(IcdP+BghiP) suggested that long-range atmospheric transmission (LRAT) and pyrogenic were the main PAHs sources, but that local PAH emission contribution gradually increased since 1990, and mixed (petroleum and combustion) sources were the dominant since 2000. The high concentration of Phenanthrene (Phe) and Naphthalene (Nap) were likely from plant product. Furthermore, increased concentrations of 4-, 5-, and 6-ring PAHs showed significant correlations with increased coal and petroleum consumption and the number of motor vehicles, respectively, and this influence has strengthened after 2000. These were caused by rapid urbanization and industrialization following the implementation of the reform and opening up policy in 1978, and a new round of urbanization after 2000. [ABSTRACT FROM AUTHOR]

Detailed organic carbon isotope (δ13Corg) measurements were conducted on two peat sequences recovered from the north bank of the Yangtze River, East China. Seven radiocarbon dates provided firm age control of this δ13Corg record and reveal palaeoclimatic changes since the Late Glacial period. The results show that the Holocene Megathermal Maximum occurred between 8385 and 7040 cal. yr BP. The Late Glacial climate was generally cold but fluctuated frequently between 12940 and 11815 cal. yr BP. The Older Dryas (from 12940 to 12810 cal. yr BP) and the Younger Dryas (from 12645 to 12170 cal. yr BP) were characterised by cold climate conditions. In contrast, 12810 to 12645 cal. yr BP (corresponding to the Allerød Warm Period) and 12170 to 11815 cal. yr BP (corresponding to a rapid warming period after the Younger Dryas, marking the beginning of the Holocene) were relatively warm phases. In contrast to other high-resolution records, it shows that the δ13Corg records of our study peats are largely controlled by a common forcing mechanism of solar insolation changes in the Northern Hemisphere, and exhibit similar variability to δ18O records obtained from stalagmites and GISP2 during the Late Glacial and early-mid Holocene. [ABSTRACT FROM AUTHOR]

A high‐resolution study of bulk properties in a peat sequence from the Xinjiang Altai Mountains of northwestern China has allowed reconstruction of local variations in peat properties and peat C and N accumulation rates (CAR and NAR) during the Holocene. Analyses of peat bulk density, loss on ignition, and concentrations of total organic carbon (TOC) and total nitrogen (TN) and their elemental ratios and stable isotopic values suggest that changes in peat‐forming vegetation types during different parts of this epoch are the major factors responsible for the variations of peat properties in this sequence. The long‐term peat CAR has been 25.4 ± 7.7 (SD) g C/m2/yr, with lower values during the early Holocene and higher accumulations during the late Holocene, which is opposite to the Holocene variations in CAR in other northern peatlands. In contrast, the long‐term peat NAR is 1.5 ± 0.5 (SD) g N/m2/yr and is higher during the early and middle Holocene and lower during the late Holocene as in other northern peatlands. However, unlike other northern peatlands, long‐term peat NAR does not vary with the CAR, which is influenced by the peat density and accumulation rate. Variations in long‐term peat C and N accumulations in the Altai Mountains can be attributed to changes in primary productivity, in the dominant plant types and in peat decomposition caused by changes in both regional Holocene climate and local conditions. Plain Language Summary: Variations in Holocene carbon and nitrogen accumulations in a peat sequence in the Altai Mountains of northwestern China can be attributed to changes in plant productivity, in the dominant plant types and in peat decomposition caused by changes in both regional climate and site‐specific environmental conditions. Key Points: A high‐resolution study was conducted of bulk properties in a peat sequence from the Xinjiang Altai Mountains of northwest ChinaReconstructions of Holocene peat C and N accumulations in the Altai Mountains of northwest China were doneRegional comparisons imply that plant communities and productivities are major controls on peat C and N accumulation in northwest China [ABSTRACT FROM AUTHOR]

A high-resolution peat humification record is obtained from Hani peatland, northeastern China to study climate change. An absorbance value time series from alkali-extraction is used as a peat humification indicator. In addition, Hani peat magnetic susceptibility and trace elements have also been investigated. There is a sensitive response to abrupt climate changes when comparing a high-resolution peat humification record with a Hani δ18O temperature proxy record and a drift ice record from the North Atlantic Ocean. Based on analyses of factors that affect peat decomposition, we suggest similar paleoclimate significance between the Hani and Dajiuhu peat on the degree of humification with a higher peat humification indicating colder and drier climate conditions. In contrast, a warm and moist climate provides a deoxidized condition that results in lower peat humification. Moreover, the Rb/Sr ratios and χlf in Hani peatland also indicate different climate conditions, especially in late Holocene. According to the Hani peat data, regional paleoclimate variations can be divided into the following five phases: 11.5-10.0 cal. kyr BP with warm climate conditions; 10.0-8.8 cal. kyr BP with sharply cooling and warming climate conditions; 8.8-4.8 cal. kyr BP with alternating cooling and warming climate conditions; 4.8-1.6 cal. kyr BP with warm climate conditions overall and 1.6-0 cal. kyr BP with cold climate conditions. [ABSTRACT FROM AUTHOR]

To achieve a better understanding of Holocene climate change in the monsoon regions of China, we investigated the molecular distributions and carbon and hydrogen isotope compositions (δ13C and δD values) of long-chain n-alkanes in a peat core from the Shiwangutian (SWGT) peatland, south China over the last 9 ka. By comparisons with other climate records, we found that the δ13C values of the long-chain n-alkanes can be a proxy for humidity, while the δD values of the long-chain n-alkanes primarily recorded the moisture source δD signal during 9–1.8 ka BP and responded to the dry climate during 1.8–0.3 ka BP. Together with the average chain length (ACL) and the carbon preference index (CPI) data, the climate evolution over last 9 ka in the SWGT peatland can be divided into three stages. During the first stage (9–5 ka BP), the δ13C values were depleted and CPI and Paq values were low, while ACL values were high. They reveal a period of warm and wet climate, which is regarded as the Holocene optimum. The second stage (5–1.8 ka BP) witnessed a shift to relatively cool and dry climate, as indicated by the more positive δ13C values and lower ACL values. During the third stage (1.8–0.3 ka BP), the δ13C, δD, CPI and Paq values showed marked increase and ACL values varied greatly, implying an abrupt change to cold and dry conditions. This climate pattern corresponds to the broad decline in Asian monsoon intensity through the latter part of the Holocene. Our results do not support a later Holocene optimum in south China as suggested by previous studies. [ABSTRACT FROM AUTHOR]

The Asian summer monsoon is a very important climatic component affecting the land ecosystem on the eastern Asian continent. Here we assess microbe-derived lipid biomarker evidence from a well-dated peat core from Dajiuhu to reconstruct paleotemperature changes in central China through the last 13 ka. The branched fatty alcohol ratio BNA15, which is defined as the relative contribution of branched C15 fatty alcohols over their straight-chain homolog, shows a positive correlation with air temperature (R= 0.83, n=11, p<0.001) in an altitude transect at Shennongjia Mountain, central China. This correspondence suggests that the microbial activities associated with branched fatty alcohol synthesis are sensitive to differences in temperature. The BNA15 sequence in the Dajiuhu peat deposit shows a trend similar to the paleotemperature record derived from pollen results over the last 13 ka, further supporting that BNA15 is a sensitive proxy of paleotemperature. Absolute temperatures estimated from BNA15 values of modern surface peats are about 3–4°C lower than the modern annual mean air temperature in the peatland, which may result from the influences of factors other than temperature or from the different microbial communities in the mountain soils used to calibrate the BNA15 acidic peats. Fluctuations in the continuous 13 ka BNA15-derived record of relative temperature change from the Dajiuhu peat core imply that solar activity is the dominant cause for most cold events at multicentennial to submillennial timescales. [ABSTRACT FROM AUTHOR]

The last glacial–interglacial climate transition in East Asia was characterized by an intensified monsoon, but knowledge about hydrological responses at a regional scale during this transitional period is limited. Here we provide a novel lipid-based paleohydrological record for this period from the Dajiuhu peat deposit, central China. High water levels and persistent wet conditions during the Younger Dryas (12.5–11.6 ka) and the early Holocene (10.5–9.9 ka) were inferred on the basis of enrichments of sterenes, a group of unstable intermediate diagenetic products derived from biogenic sterols that are most likely preserved under a waterlogged peatland surface. These two wet intervals were accompanied by temperature decreases indicated by an increase in pollen abundance from cold favoring conifer trees and a decrease in total hardwood tree pollen. This cold and wet climate pattern, which is different from the concordant cold-dry pattern documented in north China, was probably caused by the regional influence of the western Pacific subtropical high on the residence time of the Meiyu rainband in the middle and lower reaches of the Yangtze River Valley. [ABSTRACT FROM AUTHOR]

High-precision 210Pb dating technology was applied to a peat core with a time span of about 150 years that was taken from Hongyuan, Sichuan Province, China. The concentrations of total mercury (Hg) and stable isotope compositions of mercury in the peat core were measured using a LUMEX 915 instrument and multi-collector inductively coupled plasma mass spectrometer, respectively. Total mercury (Hg) concentrations in the peat core had a clearly increasing trend from the bottom to top of the core while δ202Hg values (relative to NIST 3133) of peat had a decreasing trend. The total mercury (Hg) concentration varied from 16.7 to 101.3 ng/g and the δ202Hg values ranged from -0.44‰ ± 0.14‰ to -1.45‰ ± 0.22‰. We clearly show that the study area experienced mercury pollution after the industrial revolution, and the mercury emitted from natural sources and anthropogenic sources had different Hg isotope signatures. [ABSTRACT FROM AUTHOR]

A peat core with depths of 297 cm was obtained from the Dajiuhu Basin (31°29'27"N, 109°59'45"E, 1760 m) in Hubei Province, Central China. 10 AMS ages provide a time control and reveal that this core spans the past about 16.0 kaBP (calibrated age) (14C age: 13.3 kaBP). Multi-proxy indexes analysis of geochemistry shows the following character of climate and environmental changes since about 16 kaBP: (1) The climate during the late-glacial period was cold and wet as a whole, but fluctuated continually. 11.4-12.6 cal. kaBP, 12.6-15.2 cal. kaBP and 15.2-16 kaBP were corresponding respectively to the Younger Drays, Bolling-Allerød Warm Period and the Oldest Drays. (2) Inheriting the some climate characteristics of the late-glacial, the climate during the early-Holocene was wet and temperature increased gradually, during which an obvious dry event around 10.6 cal. kaB appeared. (3) The climate during the mid-Holocene was generally warm and wet. During 9.2-7.5 kaBP, temperature increased gradually, precipitation was less comparatively and the 8.2 kaBP cold event which might be representative in the globe was reflected markedly. Then, multi-proxy records were relatively stable during 6.7-4.2 kaBP, which shows the best water and thermal condition in the Holocene Optimum. (4) Around 4.2 kaBP, the climate and environment transform from warm and wet to cool and dry, which may result in the collapse of the Neolithic Culture and midwifery the civilization of Xia Dynasty in this region. After 0.9 kaBP, the climate turned cool and wet. Climate and environmental changes archived in Dajiuhu peat respond to the global changes since the late-glacial period and can be contrasted to the changes recorded in other high-resolution archives from the East Asia Monsoon region, which take on the variety model that the monsoon strengthened abruptly after the late-glacial, was strong during the early Holocene, subsequently declined and became weak after the middle Holocene with dry climate. According to our analysis, the driving mechanism should be the response of solar radiation changes in the East Asia Monsoon region at middle latitudes. [ABSTRACT FROM AUTHOR]

The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.