Differential effects of warming on the complexity and stability of the microbial network in Phragmites australis and Spartina alterniflora wetlands in Yancheng, Jiangsu Province, China.

The impact of climate warming on soil microbial communities can significantly influence the global carbon cycle. Coastal wetlands, in particular, are susceptible to changes in soil microbial community structure due to climate warming and the presence of invasive plant species. However, there is limited knowledge about how native and invasive plant wetland soil microbes differ in their response to warming. In this study, we investigated the temporal dynamics of soil microbes (prokaryotes and fungi) under experimental warming in two coastal wetlands dominated by native Phragmites australis (P. australis) and invasive Spartina alterniflora (S. alterniflora). Our research indicated that short-term warming had minimal effects on microbial abundance, diversity, and composition. However, it did accelerate the succession of soil microbial communities, with potentially greater impacts on fungi than prokaryotes. Furthermore, in the S. alterniflora wetland, experimental warming notably increased the complexity and connectivity of the microbial networks. While in the P. australis wetland, it decreased these factors. Analysis of robustness showed that experimental warming stabilized the co-occurrence network of the microbial community in the P. australis wetland, but destabilized it in the S. alterniflora wetland. Additionally, the functional prediction analysis using the Faprotax and FunGuild databases revealed that the S. alterniflora wetland had a higher proportion of saprotrophic fungi and prokaryotic OTUs involved in carbon degradation (p < 0.05). With warming treatments, there was an increasing trend in the proportion of prokaryotic OTUs involved in carbon degradation, particularly in the S. alterniflora wetland. Therefore, it is crucial to protect native P. australis wetlands from S. alterniflora invasion to mitigate carbon emissions and preserve the health of coastal wetland ecosystems under future climate warming in China.

Spatial distribution and sources of heavy metals in the sediment and soils of the Yancheng coastal ecosystem and associated ecological risks.

Studies of heavy metal pollution are essential for the protection of coastal environments. In this study, positive matrix factorization (PMF) and a GeoDetector model were used to evaluate the sources of heavy metal contamination and associated ecological risks along the Yancheng Coastal Wetland. The distribution of heavy metals was shown to be greatly affected by clay content, except for Cr in shoal. Components from 6.5 to 9φ have the strongest ability to absorb heavy metals, where the effects of Cd and Zn sequestration in the wetlands were most apparent. The abilities of various wetland environments to sequester heavy metals were shown to be Spartina alterniflora wetland > woodland > Phragmites australis wetland > aquaculture pond > shoal > paddy > meadow > dry land. The sources of the heavy metals included parent soil material (59%), agriculture (15%), and industrial pollutants (26%). According to the single-factor pollution index, there was no evidence of pollution except Cr and Pb. In general, the heavy metal pollution was insignificant. The order of pollution loading index was shoal > paddy field > dry land > Spartina Alterniflora wetland > aquaculture ponds > woodland > meadow > Phragmites australis wetland. The ecological harm of heavy metal exposure was slight except for Cd and Hg, where vehicle emissions appeared to be the main cause of heavy metal pollution.

Responses of photosynthetic characteristics of Phragmites australis to simulated warming in salt marshes of the Yellow Sea and Bohai Sea, China.

Coastal wetlands are highly efficient in blue carbon sequestration. The impacts of climate warming on photosynthetic rates and light response characteristics of wetland plants would change the magnitude of carbon sequestration in coastal wetlands. We constructed warming observation stations in Phragmites australis (Phragmites) wetlands located in the Yellow River Delta in Dongying with dry climate, and in Yancheng by the Yellow Sea with wet climate. By using a Li-6800 photosynthesis system, we investigated the responses of simulated warming on photosynthetic characteristics of Phragmites in both wetlands, and compared the difference between months (June and August) in Dongying wetland. The results showed the photosynthetic rates of Phragmites were higher in June than in August. Warming increased net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs) and intercellular carbon dioxide concentration (Ci) in the two months, but the variability of Pn to warming was lower in August. The Pn and water use efficiency (WUE) of Phragmites in the Yancheng wetland were higher than Dongying wetland, and the maximum net photosynthetic rate (Pn max), light saturation point (LSP), apparent quantum efficiency (AQY), and dark respiration rate (Rd) of the former responded more positively to warming. The values of AQY, LSP and Pn max of Phragmites in the Yancheng wetlands were increased by 16.7%, 53.6% and 30.3%, respectively, in the warming plots. Our results suggested that warming could improve the utilization efficiency of weak light, the adaptability to strong light and photosynthetic potential of Phragmites under rainy and humid conditions. This study is of importance for accurately quantifying carbon sequestration of coastal wetlands at the regional and seasonal scales in the context of climate warming.

Pollen distribution and transportation patterns in surface sediments of Liaodong Bay, China.

Understanding pollen transport pathways and dispersal mechanism from the land to sea is a prerequisite for marine palynological study. Palynological analysis of 164 surface sediment samples in Liaodong Bay, and 39 analogous surface alluvium samples from its five inflowing rivers, identifies the distribution patterns, pathways and possible sources of pollen and spores. The results show that pollen and spore assemblages in surface sediments are well correlated to regional vegetation distribution, and the variations of pollen assemblage in different parts of Liaodong Bay reflected local vegetation changes along the coast. High pollen concentrations are mainly distributed in the estuaries of inflowing rivers, coastal waters and sea muddy areas. The pollen assemblage characteristics of alluvial samples are similar to those from coastal waters with water depths <8.5 m. Samples from the alluvium and surface sediments of coastal waters were dominated by herbaceous pollen taxa including Artemisia, Amaranthaceae, Poaceae, Cyperaceae and Typha. Herbaceous pollen percentages and concentrations decreased as the water depth increased, indicating that pollen and spores in the coastal waters of Liaodong Bay are mainly carried by the inflowing rivers. However, pollen assemblages for samples with water depth >8.5 m are significantly different from those of the alluvium. In samples taken below a depth of 8.5 m, the arboreal pollen is dominated by airborne Pinus, and there is a high number of the waterborne Selaginella fern spores, both of which are sourced from a wider region. In the Liaodong Bay, both wind and ocean current transportation determines the pollen distribution patterns in deeper waters, while fluvial and longshore current transportation determines the pollen assemblages found in shallow waters. The dispersal characteristics of pollen assemblages between the land and the sea in Liaodong Bay provide a theoretical basis for the interpretation of fossil pollen assemblages and past sea level changes.

The concentration distribution and pollution assessment of heavy metals in surface sediments of the Bohai Bay, China.

Three hundred five surface sediment samples from the Bohai Bay in northeastern China were examined for grain size, organic carbon (Corg) concentration, and concentrations of heavy metals (Pb, Zn, Cu, As, Cr, Cd, and Hg). Average metal concentrations were 33 mg/kg (Cu), 27 mg/kg (Pb), 95 mg/kg (Zn), 75 mg/kg (Cr), 0.3 mg/kg (Cd), 13 mg/kg (As), and 72 µg/kg (Hg). In most cases, these concentrations were lower than the China Marine Sediment Quality criteria. Enrichment factors, however, suggested moderate to strong Cd and Hg contamination of the Bohai Bay. The fact that 68.6% of Pollution Load Index (PLI) values exceeded 2 demonstrated strong pollution of the Bohai Bay, Hg contributed the most to the PLI.

Spatial distribution and ecological risk assessment of heavy metals in coastal surface sediments in the Hebei Province offshore area, Bohai Sea, China.

Seven hundred and nine surface sediment samples, along with deeper sediment samples, were collected from Hebei Province along the coastal section of the Bohai Sea, China, and analyzed for grain size, concentrations of organic carbon (Corg) and heavy metals (Cu, Pb, Zn, Cr, Cd, As, and Hg). Results indicated that the average concentrations in the sediments were 16.1 mg/kg (Cu), 19.4 mg/kg (Pb), 50 mg/kg (Zn), 48.8 mg/kg (Cr), 0.1 mg/kg (Cd), 8.4 mg/kg (As), and 20.3 µg/kg (Hg). These concentrations generally met the China Marine Sediment Quality criteria. However, both pollution assessments indicated moderate to strong Cd and Hg contamination in the study area. The potential ecological risk index suggested that the combined ecological risk of the seven studied metals may be low, but that 24.5% of the sites, where sediments were finer and higher in Corg concentration, had high ecological risk in Hg and Cd pollution.

Surface sediment properties and heavy metal contamination assessment in river sediments of the Pearl River Delta, China.

Concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn), grain sizes, and concentrations of organic carbon (Corg) were measured in 323 river sediment samples from the Pearl River Delta (PRD). Results showed that the heavy metal concentrations in the sediments ranged from 1.6-93 mg/kg for As, 0.04-9.3 mg/kg for Cd, 2-315 mg/kg for Cr, 1.1-352 mg/kg for Cu, 0.01-0.67 mg/kg for Hg, 11-221 mg/kg for Pb, and 11-1234 mg/kg for Zn. The highest values of As, Cr, Cu, Hg, Pb, and Zn appeared in the Beijiang River, whereas Cd was high in the Xijiang River. The overall sediment quality in the area with respect to metal concentrations generally met the primary standard criteria of China (Marine Sediment Quality), except for Cd and Cu. The spatial distributions of the heavy metals were influenced by both grain sizes and Corg concentrations. The Igeo geo-accumulation index indicated that there was no significant Cr, Cu, Hg, or Zn pollution, slight to moderate pollution by As and Pb, and moderate Cd pollution in the study area. Spatial distributions of an eco-toxicological index based on probable effect levels indicated that there was a 21% probability that the combination of the seven metals was exerting a toxic stress in the PRD river sediments.

Metal pollution across the upper delta plain wetlands and its adjacent shallow sea wetland, northeast of China: implications for the filtration functions of wetlands.

Grain size and concentrations of organic carbon (Corg) and particulate metals (PMs) As, Cd, Cr, Cu, Hg, Pb, Zn, Al, Fe, and Mn of 373 surface sediment samples, salinities in 67 surface water samples, were analyzed in various environments, including the upper delta plain wetlands (UDPW), its adjacent shallow sea wetland (SSW) in the Liaodong Bay, and river channels that are running through the Liaohe Delta, to evaluate the spatial distribution, transportation environmental dynamics of metals, and the provenance of metal pollution and assess the filtration functions of wetlands. The concentrations of PMs for UDPW were generally higher by a factor of ~ 10-22% compared with its analogues in SSW, suggesting the accumulation of PMs within the UDPW indicates that the UDPW systems are efficiently physical and chemical traps for PMs of anthropogenic sources by retaining and storing pollutants flowing into the sea. However, there was sever sewage irrigation-induced Cd pollution with a geo-accumulation index of 0.62-3.11 in an area of ~ 86 km2 of the adjacent shallow sea wetland, where large amount wetlands were historically moved for agriculture in the UDPW. Remarkably, the distributions of PMs were controlled by salinity-induced desorption and re-adsorption mechanisms and significantly dispersed the contamination coverage by the three-dimensional hydrodynamic and sedimentation processes that dominated by inputs of freshwater and ocean dynamics including NE-SW tidal currents and NE-E longshore drifts in the SSW of the Liaodong Bay. A high agreement between the UDPW and the SSW datasets in principal component analysis essentially reflects that the characteristics of PM sources in the SSW were actually inherited from that in the UDPW, with a much closer relationship among metals, organic matter, and fine particulates in SSW than that of UDPW, which was judged by their correlation coefficient range of 0.406-0.919 in SSW against those of 0.042-0.654 in UDPW.

Sediment record of polycyclic aromatic hydrocarbons in the Liaohe River Delta wetland, Northeast China: Implications for regional population migration and economic development.

The polycyclic aromatic hydrocarbons (PAHs) of a 210Pb-dated sediment core extracted from the Liaohe River Delta wetland were measured to reconstruct the sediment record of PAHs and its response to human activity for the past 300 years in Northeast China. The concentrations of the 16 U.S. Environmental Protection Agency priority PAHs (∑16PAHs) ranged from 46 to 1167 ng g-1 in this sediment core. The concentrations of the 16 PAHs (especially 4- and 5+6-ring PAHs) after the 1980s (surface sediments 0-6 cm) were one or two orders of magnitudes higher than those of the down-core samples. The exponential growth of 4-ring and 5+6-ring PAH concentrations after the 1980s responded well to the increased energy consumption and number of civil vehicles resulting from the rapid economic development in China. Prior to 1950, relatively low levels of the 16 PAHs and a high proportion of 2+3-ring PAHs was indicative of biomass burning as the main source of the PAHs. A significant increase in the 2 + 3 ring PAH concentration from the 1860s-1920s was observed and could be attributed to a constant influx of population migration into Northeast China. It was suggested that the link between historical trend of PAHs and population or energy use involves two different economic stages. Typically, in an agricultural economy, the greater the population size, the greater the emission of PAHs from biomass burning, while in an industrial economy, the increase in sedimentary PAH concentrations is closely related to increasing energy consumption of fossil fuels.

Surface sediment properties and heavy metal pollution assessment in the Pearl River Estuary, China.

Grain size and concentrations of heavy metals (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn)) of 148 surface sediments and activities of 210Pb and heavy metal concetrantions of one sediment core from the Pearl River Estuary were analyzed. The surface sediments were dominated by silt and sandy silt. Sediment type controlled the spatial distribution patterns of the heavy metals. The heavy metal concentrations in the sediments ranged from 3.34 to 37.11 mg/kg for As, 0.06 to 2.06 mg/kg for Cd, 12 to 130 mg/kg for Cr, 5.8 to 170.6 mg/kg for Cu, 0.01 to 0.25 mg/kg for Hg, 23 to 78 mg/kg for Pb, and 32 to 259 mg/kg for Zn. Both contents of clay and organic carbons were significantly positively correlated with heavy metals. The baseline values of elements in the study area were 12.97 mg/kg for As, 0.14 mg/kg for Cd, 68 mg/kg for Cr, 28.9 mg/kg for Cu, 0.08 mg/kg for Hg, 33 mg/kg for Pb, and 92 mg/kg for Zn. The metal enrichment factor (EF) and geoaccumulation index (Igeo) were calculated to assess anthropogenic contamination. Results showed slight to moderate Cd contamination in the region. Principle component analysis indicated that Cd could be attributed to anthropogenic sources; As and Hg were predominantly affected by human activities; and Pb, Cr, Cu, and Zn were associated with both natural and anthropogenic sources.

Surface sediment properties and heavy metal pollution assessment in the Shallow Sea Wetland of the Liaodong Bay, China.

Liaodong Bay, a semi-enclosed bay located in northeastern China, is impacted by the discharges of five rivers. We analyzed 100 surface sediment samples from the Shallow Sea Wetland of Liaodong Bay for grain size and concentrations of organic carbon (Corg) and heavy metals. The ranges of the heavy metal concentrations were 2.32-17µg/g (As), 0.025-1.03µg/g (Cd), 18.9-131µg/g (Cr), 4.6-36.1µg/g (Cu), 0.012-0.29µg/g (Hg), 13.7-33.9µg/g (Pb), and 17.4-159µg/g (Zn). Pollution assessments revealed that some stations were moderately to highly polluted with As, Cd, and Hg. Severe pollution was apparent in the Xiaoling River estuary; lower concentrations of heavy metals were observed in other river mouths, where the sediments were more coarse. The distributions of the heavy metals were closely associated with Corg and grain size.

Assessment of heavy metal contamination in surface sediments of the west Guangdong coastal region, China.

Heavy metals (As, Cd, Cr, Cu, Hg, Pb, Zn), organic carbon and grain size of 237 surface sediment samples and one sediment core, taken from the west Guangdong coastal region in January 2008, were analyzed to evaluate the spatial distribution and pollution status. Results show that the ranges of the measured heavy metal concentrations in sediments are as follows: 8.33-39.49mg/kg for As, 0.1-1.49mg/kg for Cd, 33-108mg/kg for Cr, 11.5-78.8mg/kg for Cu, 0.04-0.26mg/kg for Hg, 21-73mg/kg for Pb, 56-248mg/kg for Zn. The heavy metal enrichment is closely associated with Corg and grain size. Both the metal enrichment factor and geoaccumulation index indicate that there was no detected pollution on metals As, Cr, Cu, Pb in our study area and a slight to moderate contamination of Cd, Hg and Zn. However, As, Cr and Cu have showed a certain risk.

Distribution and contamination of heavy metals in surface sediments of the Daya Bay and adjacent shelf, China.

Heavy metal (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn)) concentrations from the Daya Bay and adjacent shelf were determined to evaluate their levels and spatial distributions. The measured concentrations ranged from 1.94-13.67mg/kg for As, 0.03-0.13mg/kg for Cd, 10-85mg/kg for Cr, 1-39.5mg/kg for Cu, 0.01-0.09mg/kg for Hg, 11-56mg/kg for Pb, and 13-125mg/kg for Zn. The spatial distributions exhibited a gradual decrease from west to east, and the concentrations of the seven heavy metals met the China Marine Sediment Quality criteria. Both metal enrichment factor (EF) and geo-accumulation index (Igeo) values showed that Cd, Cr, Cu, Hg, and Zn were not at pollution levels in the region. Multivariate analysis (PCA) revealed that lithogenic factors dominated the distribution of most of the metals, whereas As and Hg were clearly influenced by anthropogenic input.

Inter-Annual Variability of Area-Scaled Gaseous Carbon Emissions from Wetland Soils in the Liaohe Delta, China.

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO2 and CH4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO2 (~98%). Photosynthetic uptake of CO2 would mitigate most of the soil CO2 emissions, but CH4 emissions would persist. Overall, CH4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.

Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in surface soils of the Yellow River Delta, China.

PAH concentrations of 61 surface soil samples collected from the Yellow River Delta (YRD), China were measured to determine occurrence levels, sources, and potential toxicological significance of PAHs. The total concentrations of ∑PAHs ranged from 27 to 753 ng/g d.w., with a mean of 118±132 ng/g. The highest concentrations was found in the mid-southern part of the YRD (753 ng/g), which was associated with the oil exploration. The ratios indicated that the PAHs throughout the YRD were mostly of pyrogenic origin; while various sites in mid-southern part in the region were derived mainly from the petrogenic sources. Multivariate statistical analyses supported that the PAHs in surface soils of the YRD were principally from the coal and biomass combustion, petroleum spills, and/or vehicular emissions. The toxic assessment suggested that the PAHs in soils were at low potential of ecotoxicological contamination level for the YRD.

Source apportionment of polycyclic aromatic hydrocarbons in soils of wetlands in the Liao River Delta, Northeast China.

The polycyclic aromatic hydrocarbons (PAHs) of 55 surface soil samples from the wetlands in the Liao River Delta, Northeast China were measured in order to apportion their sources. The total concentrations of 16 US EPA priority PAHs and alkyl-PAHs in this region ranged 106-3148 ng g⁻¹ (dry weight) (average: 550 ± 565 ng g⁻¹) and 54-5564 ng g⁻¹ (average: 517 ± 838 ng g⁻¹), respectively. Based on the positive matrix factorization analysis of alkylated and parent PAHs, six sources of PAHs were identified including petroleum (23%), biomass burning (23%), air-soil exchange (18%), coal combustion (17%), traffic emission (14%) and biogenic origin (6%). The positive correlation between low molecular weight (LMW) PAHs and TOC contents could demonstrate a potential positive influence of TOC on the accumulations of LMW PAHs in soils by the air-soil exchange. The petrogenic PAHs may pose a limited harmful effect on aquatic organisms although they were abundant in the area.

Sources and preservation of organic matter in soils of the wetlands in the Liaohe (Liao River) Delta, North China.

Total organic carbon, total nitrogen, δ(13)Corg, δ(15)N, and aliphatic and polyaromatic hydrocarbons of fifty-five soil samples collected from the coastal wetlands of the Liaohe Delta were measured, in order to determine the sources and possible preservation of organic matter (OM). The δ(15)N and δ(13)Corg values in the samples ranged from 3.0‰ to 9.4‰ and from -30.4‰ to -20.3‰, respectively, implying that the OM in the soils is predominantly derived from C3 plant. The long-chain n-alkanes had a strong odd-over-even carbon number predominance, suggesting a significant contribution from waxes of higher plants. The ubiquitous presence of unresolved complex mixture, alkylated polycylic aromatic hydrocarbons and typical biomarkers of petroleum hydrocarbons (pristane, phytane, hopanes and steranes) indicates that there is a contribution of petroleum hydrocarbons to the organic carbon pool in the wetland soils. P. australis-vegetated wetlands have strong potentials for the preservation of organic carbon in the wetlands.

[Hydrochemical characteristics and formation mechanism of shallow groundwater in the Yellow River Delta].

Understanding the chemical characteristics of groundwater in the Yellow River Delta is very important. It can provide a useful reference for the development and construction of the Yellow River Delta High-efficiency Ecological Economic Zone and ecological regulation in the lower Yellow River. Based on partitioning the sediment environment and the recharge-runoff-discharge system, we studied the hydrochemical features and causes of shallow groundwater in the Yellow River Delta by mathematical statistics and geostatistics, Piper diagram, ion ratios and so on. Following results are obtained: 1) Major cations and anions such as Na+, Mg2+, Ca2+, Cl(-), SO4(2-), HCO3(-) and TDS concentrations range from 0.1-25.0 g x L(-1), 3.6-3 815.0 mg x L(-1), 5.6-3 377.0 mg x L(-1), 0.1-45.1 g x L(-1), 24.2-4 947.0 mg x L(-1), 62.6-850.0 mg x L(-1) and 0.4-80.7 g x L(-1). Average ion concentrations further indicate that Cl(-), Na+ and TDS concentrations are high while HCO3(-), CO3(2-) and K+ concentrations are very low in the study area. 2) The Cl(-) and TDS concentrations of shallow groundwater possess conspicuous directional spatial variability and gradually increase along the groundwater flow direction, showing that Cl(-) is the most critical ion of shallow groundwater. 3) From the recharge area to the discharge area, shallow groundwater changes from the Na+ -Mg2+ -Ca2+ -Cl(-) -SO4(2-) facies to the Na -Mg2 + -Ca2+ -Cl(-), Mg2+ -Na+ -Ca2+ -Cl(-) and Na+ -Mg2+ -Cl(-) facies, finally evolves into Na+ -Cl(-) facies in the coast. 4) Ion ratios indicate that the following main hydrochemical processes are inferred to control the shallow groundwater chemical composition: mixing, evaporation concentrating, mineral dissolution, cation exchange and adsorption and human activities. These findings strongly suggest that changes of the Yellow River water course and seawater intrusion are key drivers to form the chemical characteristics of shallow groundwater in the region.

Sequestration of metals through association with pyrite in subtidal sediments of the Nanpaishui Estuary on the Western Bank of the Bohai Sea, China.

Measurements were made of the degree of trace metal pyritization (DTMP) and ancillary characteristics of four undisturbed sediment cores collected from the subtidal zone of the Nanpaishui Estuary on the Western Bank of the Bohai Sea, a seriously polluted inland sea in northeastern China. The remarkably low concentrations of organic carbon (<0.72%) in these sediments likely constrained sulfate reduction rates, and the low concentrations of acid volatile sulfide (AVS) (<12.5 µmol g(-1)) limited the sequestration of metals through association with pyrite. The most consistent cause of inter-station differences and depth variations in the degree of pyritization was differences in pyrite metal concentrations rather than reactive metal concentrations. Reactive metal concentrations were in several cases negatively correlated with pore water concentrations, consistent with a dissolution/precipitation mechanism. The relationship between pore water metal concentrations and DTMPs was evidenced by a qualitative similarity of the inter-station variability of these same parameters.