Evidence and causes of recent decreases in nitrogen deposition in temperate forests in Northeast China.

High reactive nitrogen (N) emissions due to anthropogenic activities in China have led to an increase in N deposition and ecosystem degradation. The Chinese government has strictly regulated reactive N emissions since 2010, however, determining whether N deposition has reduced requires long-term monitoring. Here, we report the patterns of N deposition at a rural forest site (Qingyuan) in northeastern China over the last decade. We collected 456 daily precipitation samples from 2014 to 2022 and analysed the temporal dynamics of N deposition. NH4+-N, NO3--N, and total inorganic N (TIN) deposition ranged from 10.5 ± 3.5 (mean ± SD), 6.1 ± 1.6, and 16.6 ± 4.7 kg N ha-1 year-1, respectively. Over the measurement period, TIN deposition at Qingyuan decreased by 55 %, whereas that in comparable sites in East Asia declined by 14-34 %. We used a random forest model to determine factors influencing the deposition of NH4+-N, NO3--N, and TIN during the study period. NH4+-N deposition decreased by 60 % because of decreased agricultural NH3 emissions. Furthermore, NO3--N deposition decreased by 42 %, due to reduced NOx emissions from agricultural soil and fossil fuel combustion. The steep decline in N deposition in northeastern China was attributed to reduced coal consumption, improved emission controls on automobiles, and shifts in agricultural practices. Long-term monitoring is needed to assess regional air quality and the impact of N emission control regulations.

Large Seasonal Variation in Nitrogen Isotopic Abundances of Ammonia Volatilized from a Cropland Ecosystem and Implications for Regional NH3 Source Partitioning.

Ammonia (NH3) volatilization from agricultural lands is a main source of atmospheric reduced nitrogen species (NHx). Accurately quantifying its contribution to regional atmospheric NHx deposition is critical for controlling regional air nitrogen pollution. The stable nitrogen isotope composition (expressed by δ15N) is a promising indicator to trace atmospheric NHx sources, presupposing a reliable nitrogen isotopic signature of NH3 emission sources. To obtain more specific seasonal δ15N values of soil NH3 volatilization for reliable regional seasonal NH3 source partitioning, we utilized an active dynamic sampling technique to measure the δ15N-NH3 values volatilized from maize cropping land in northeast China. These values varied from -38.0 to -0.2‰, with a significantly lower rate-weighted value observed in the early period (May-June, -30.5 ± 6.7‰) as compared with the late period (July-October, -8.5 ± 4.3‰). Seasonal δ15N-NH3 variations were related to the main NH3 production pathway, degree of soil ammonium consumption, and soil environment. Bayesian isotope mixing model analysis revealed that without considering the seasonal δ15N variation in soil-volatilized NH3 could result in an overestimate by up to absolute 38% for agricultural volatile NH3 to regional atmospheric bulk ammonium deposition during July-October, further demonstrating that it is essential to distinguish seasonal δ15N profile of agricultural volatile NH3 in regional source apportionment.

Delayed recovery of surface water chemistry from acidification in subtropical forest region of China.

The three largest acid rain regions of current earth are located in northern and western Europe, eastern North America, and East Asia. Sulfur and nitrate concentrations in headwater streams in Europe and North America decreased as atmospheric sulfur and nitrogen deposition decreased, albeit with a considerable delay. However, how water chemistry responds to the declining sulfur and nitrogen deposition in China is unclear. The regional survey of surface water chemistry during 2010 and 2018 within the Sichuan Basin in southwestern China showed that the recovery of the surface water chemistry was delayed for at least 5 years owing to the release of previously deposited sulfur and nitrogen stored in the soil. After sulfur deposition declined from its peak value, the subregions of purplish soil with low sulfate adsorption capacity still exhibited a net sulfur release in 2010, but this release was no longer evident by 2018. The subregions with the red and yellow soils, which have a high sulfate adsorption capacity, operated as sulfur sinks during 2010 and 2018, indicating a continuous immobilization process through sulfate reduction despite a decrease in sulfur deposition. Additionally, this sulfate reduction countered the release of sulfate caused by sulfur desorption. There was a substantial nitrogen sink within the Sichuan Basin. Nitrogen leaching decreased slowly with the declined nitrogen deposition, except in regions where nitrogen deposition exceeded the critical threshold. Compared to temperate forest regions in Europe, the Sichuan Basin and its surrounding areas have experienced higher decline rates in the leaching of sulfur and nitrogen, highlighting that the subtropical forest region undergoes a faster restoration of surface water chemistry.

NO2 Sensor Based on Faraday Rotation Spectroscopy Using Ring Array Permanent Magnets.

Faraday rotation spectroscopy (FRS) exploits the magneto-optical effect to achieve highly selective and sensitive detection of paramagnetic molecules. Usually, a solenoid coil is used to provide a longitudinal magnetic field to produce the magneto-optical effect. However, such a method has the disadvantages of excessive power consumption and susceptibility to electromagnetic interference. In the present work, a novel FRS approach based on a combination of a neodymium iron boron permanent magnet ring array and a Herriott multipass absorption cell is proposed. A longitudinal magnetic field was generated by using 14 identical neodymium iron boron permanent magnet rings combined in a non-equidistant form according to their magnetic field's spatial distribution characteristics. The average magnetic field strength within a length of 380 mm was 346 gauss. A quantum cascade laser was used to target the optimum 441 ← 440 Q-branch nitrogen dioxide transition at 1613.25 cm-1 (6.2 µm) with an optical power of 40 mW. Coupling to a Herriott multipass absorption cell, a minimum detection limit of 0.4 ppb was achieved with an integration time of 70 s. The low-power FRS nitrogen dioxide sensor proposed in this work is expected to be developed into a robust field-deployable environment monitoring system.

Fluxes of H2S and SO2 above a subtropical forest under natural and disturbed conditions induced by temporal land-use change.

Hydrogen sulfide (H2S) is one of predominant biogenic sulfur gases, influencing aerosol formation and climate change. There is considerable uncertainty of the global budget of H2S due to limited field data, especially in subtropical forests. In addition, an interaction between soil-emitted H2S and ambient sulfur dioxide (SO2) might exist within forest ecosystems. In this study, the aerodynamic gradient method was applied to consecutively measure H2S and SO2 fluxes above a subtropical forest canopy in Southwest China under natural and disturbed conditions induced by temporal land-use changes. The average H2S concentration and flux under natural conditions were 0.79 ± 0.07 ppbv and 0.04 ± 0.01 g S m-2 yr-1, respectively. The emission was larger than that in most croplands and freshwater wetlands. Vegetation emissions might account for about 26% of the total forest H2S emissions at this site. The deposition of SO2 was likely balanced by H2S oxidization under the forest canopy, with the mean concentration and net flux as 1.23 ± 0.11 ppbv and -0.03 ± 0.10 g S m-2 yr-1, respectively. Under disturbed conditions with soils excavation and scattering on the forest floor, simultaneously high emissions of H2S and SO2 were observed above the canopy, reaching 5.78 ± 0.16 and 1.60 ± 0.87 g S m-2 yr-1, respectively. This suggested that land-use change in subtropical forests might lead to release of legacy S in subsoils to the atmosphere in the form of H2S and SO2. Regarding the widely documented large S accumulation and expanding deforestation across subtropical forests, potentially high emissions of H2S and SO2 from subtropical forests should be carefully considered in regional air quality control and forest management.

Temporal variations of soil NO and NO2 fluxes in two typical subtropical forests receiving contrasting rates of N deposition.

Soils have been widely acknowledged as important natural sources of nitric oxide (NO) and meanwhile sinks of nitric dioxide (NO2). High nitrogen deposition across South China could potentially result in large NO emissions from subtropical forests soils there. In this study, the dynamic chamber method was applied to monitor NO and NO2 fluxes at two subtropical forest sites in South China, namely "Qianyanzhou" (QYZ) and "Tieshanping" (TSP). Chronically higher N deposition occurred at TSP than that at QYZ. Besides soil water filled pore spaces (WFPS) and temperature, ambient NO concentration could also possibly be important in regulating temporal NO emissions, especially in the winter. For both sites, the optimum soil temperature was above 25 °C, while the optimum WFPS for NO release at QYZ was higher (65-70%) than that at TSP (<23%). Moreover, heavy rainfall could trigger NO emission pulses from moist soils at QYZ, while rainfall-induced NO pulses were only observed after a long drying period at TSP. Distinctly different contents of mineral nitrogen and soil moisture conditions between the two sites might induce the divergent preference of WFPS and responses to rainfall. The cumulative soil emission of NO reached 0.41 ± 0.01 and 0.76 ± 0.01 kg N ha-1 yr-1 at QYZ and TSP, contributing to 2.5% and 1.4% of the annual throughfall N input, respectively. At both sites, NO2 were mainly deposited to soils, accounting for 2% and 21% of soil-emitted NO at QYZ and TSP, respectively. The observed annual NO emissions at these two sites were larger than the median values observed for tropical and temperate forests and unfertilized croplands. Higher N deposition could induce larger NO emission potential, while soil temperature and pH might also be important in regulating regional soil NO emissions as N-loss from subtropical forests.

[Effects of soil moisture on microbial processes of soil nitrogen gases production under anaerobic conditions]. / 土壤水分对土壤产生气态氮的厌氧微生物过程的影响.

Gaseous nitrogen (N) emission [nitric oxide (NO), nitrous oxide (N2O), and nitrogen (N2)] is an important pathway of soil N loss. Nitrification and denitrification are the main processes of gaseous N production in soil. However, the contribution of heterotrophic nitrification, co-denitrification, and anammox to gaseous N production remains uncertain. In a laboratory soil incubation experiment, we used the 15N labelling and pairing technique, combining the nitrification inhibitor dicyandiamide (DCD), to quantify the contribution of different microbial processes to soil NO, N2O and N2 production under anaerobic conditions. The results showed that after 24 h anaerobic incubation, the highest total 15N recovery of three gases occurred at 65% water filled pore space (WFPS), accounting for 20.0% of total added 15N. Denitrification contributed 49.9%-94.1%, 29.0%-84.7%, and 58.2%-85.8% to the production of NO, N2O and N2 respectively, suggesting that denitrification was the predominant process of those three N gases emission. Heterotrophic nitrification was an important pathway of NO and N2O production, particularly at conditions with low soil water content (10% WFPS), with its contribution to those two N gases production being 50.1% and 42.8%, respectively. Co-denitrification contributed 10.6%-30.7% of N2O production. For N2 production, the total contribution of co-denitrification and anammox was 14.2%-41.8%. The role of co-denitrification can not be ignored for N2O and N2 production. Our results demonstrated that the 15N labelling and pairing technique is a promising tool to quantify the contribution of different microbial processes to gaseous N loss.

Interannual and seasonal variabilities in soil NO fluxes from a rainfed maize field in the Northeast China.

Nitric oxide (NO) plays a critical role in atmospheric chemistry and also is a precursor of nitrate, which affects particle matter formation and nitrogen deposition. Agricultural soil has been recognized as a main source of atmospheric NO. However, quantifying the NO fluxes emitted from croplands remains a challenge and in situ long-term measurements of NO are still limited. In this study, we used an automated sampling system to measure NO fluxes with a high temporal resolution over two years (April 2017 to March 2019) from a rainfed maize field in the Northeast China. The cumulative annual NO emissions were 8.9 and 2.3 kg N ha-1 in year 1 (April 2017 to March 2018) and year 2 (April 2018 to March 2019), respectively. These interannual differences were largely related to different weather conditions encountered. In year 1, a month-long drought before and after the seeding and fertilizing reduced plant N uptake and dramatically increased soil N concentration. The following moderate rainfalls promoted large amount of NO emissions, which remained high until late September. The NO fluxes in both years showed clearer seasonal patterns, being highest after fertilizer application in summer, and lowest in winter. The seasonal patterns of NO fluxes were mainly controlled by soil available N concentrations and soil temperatures. The contribution of NO fluxes during the spring freeze-thaw in both years was no more than 0.2% of the annual NO budget, indicating that the freeze-thaw effect on agricultural NO emissions was minimal. In addition, with high-resolution monitoring, we found that soil not only act as a NO source but also a sink. Long-term and high-resolution measurements help us better understand the diurnal, seasonal, and annual dynamics of NO emissions, build more accurate models and better estimate global NO budget and develop more effective policy responses to global climate change.

Multiyear Measurements on Δ17O of Stream Nitrate Indicate High Nitrate Production in a Temperate Forest.

Nitrification is a crucial step in ecosystem nitrogen (N) cycling, but scaling up from plot-based measurements of gross nitrification to catchments is difficult. Here, we employed a newly developed method in which the oxygen isotope anomaly (Δ17O) of nitrate (NO3-) is used as a natural tracer to quantify in situ catchment-scale gross nitrification rate (GNR) for a temperate forest from 2014 to 2017 in northeastern China. The annual GNR ranged from 71 to 120 kg N ha-1 yr-1 (average 94 ± 10 kg N ha-1 yr-1) over the 4 years in this forest. This result and high stream NO3- loss (4.2-8.9 kg N ha-1 yr-1) suggest that the forested catchment may have been N-saturated. At the catchment scale, the total N output of 10.7 kg N ha-1 yr-1, via leaching and gaseous losses, accounts for 56% of the N input from bulk precipitation (19.2 kg N ha-1 yr-1). This result indicates that the forested catchment is still retaining a large fraction of N from atmospheric deposition. Our study suggests that estimating in situ catchment-scale GNR over several years when combined with other conventional flux estimates can facilitate the understanding of N biogeochemical cycling and changes in the ecosystem N status.

Fluxes of nitrogen oxides above a subtropical forest canopy in China.

Dry deposition of Nitrogen (N) in forests is commonly estimated from inferential method and/or throughfall measurements, with inevitable uncertainty. In this study, we applied an aerodynamic gradient method to directly measure the nitrogen oxides (NOx) flux above the canopy of a subtropical forest in southeastern China for two consecutive years. The flux and transfer velocity generally reached the maximum absolute values in the midday, with the largest diurnal maximum of absolute flux values observed in the winter of 2015 and that of transfer velocity in the autumn of 2015. The annual average transfer velocity was -0.79 and -0.38 cm s-1 in 2015 and 2016, respectively. Although the net downward NOx fluxes predominated for both years, upward flux (net emission) of NOx was observed during spring months, which reflected the possible bi-directional exchange balanced by soil-atmosphere and foliage-atmosphere exchanges. The NOx concentration seemed to be the most important factor controlling the NOx exchange above canopy, and could mainly explain the seasonal variation of N deposition. The linear regression between the NOx flux and concertation was explored, and it was observed that the deposition of NOx was offset by possible underlayer emission of NOx when the ambient NOx concentration below1.7 ppbv and 1.9 ppbv at night and in the day, respectively. The average dry deposition of NOx for the two years was 6.28 ± 0.06 kg N ha-1 a-1, >40% of which might be uptake by the canopy, estimated by comparing the wet/throughfall deposition measurement of nitrate with the observation of NOx flux. This indicated the importance of stomatal uptake of NOx in nitrogen budget in subtropical forests.

Nitrification is the primary source for NO in N-saturated subtropical forest soils: Results from in situ 15 N labeling.

RATIONALE: Acidic subtropical forest soils that receive high atmospheric nitrogen (N) deposition have been identified as important sources of nitric oxide (NO). The relative importance of major processes producing NO is unclear. METHODS: To partition NO sources, we conducted an in situ tracing experiment with 15 NH4 NO3 and NH4 15 NO3 in well-drained acid soils of an N-saturated subtropical forest in Chongqing, southwest China. RESULTS: In the 15 NH4 NO3 treatment, the 15 N signature of NO emitted from the foot of the hillslope (Lower site) was similar to that of the NH4 + pool, indicating predominant autotrophic nitrification for NO formation. In the NH4 15 NO3 treatment, the 15 N enrichment of NO was smaller than that of the NO3 - pool, suggesting minor contribution of denitrification to NO production (~15%). CONCLUSIONS: Nitrification is the main process responsible for NO emissions, even in monsoonal summers when soil water-filled pore space values are relatively high.

Monitoring Effect of SO2 Emission Abatement on Recovery of Acidified Soil and Streamwater in Southwest China.

Following Europe and North America, East Asia has become a global hotspot of acid deposition, with very high deposition of both sulfur (S) and nitrogen (N) occurring in large areas in southwest and southeast China. Great efforts have been made in reducing national emission of sulfur dioxide (SO2) since 2006 in China. However, the total emission of nitrogen oxides (NOx) continued to increase until 2011. To evaluate the effects of SO2 and NOx emission abatement on acid deposition and acidification of soil and water, we monitored the chemical composition of throughfall, soil water, and streamwater from 2001 to 2013 in a small, forested catchment near Chongqing city in Southwestern China. The deposition of S decreased significantly, whereas N deposition increased in the recent years. This clearly showed the effect of SO2 abatement but not of NOx. Overall the rate of acid deposition was reduced. However, there was delay in the recovery of soil and surface water from acidification, probably due to desorption of previously stored sulfate (SO42-) and increase in nitrate (NO3-) leaching from soil. The average acid input by N transformations has greatly exceeded the H+ input directly by atmospheric deposition. The reversal of acidification with an increase in pH of soil water, requires additional abatement of emissions of both SO2 and NOx.

Modified Method for Trapping and Analyzing 15N in NO Released from Soils.

15N isotope tracing is an effective and direct approach to investigate sources of nitric oxide (NO) formed in soils. However, NO is highly reactive and rapidly converted to nitrogen dioxide (NO2) in the presence of ozone, making it impossible to directly measure 15N in NO. Various wet-chemical methods for conversion of NO to nitrite (NO2-) and nitrate (NO3-) have been proposed for 15N analysis in high-concentration NO sources, such as combustion processes. In contrast, NO concentrations in the soil surface-near air are usually small (ppbv-range), posing major challenges to conversion efficiency and blank correction. Here, we present a modified method in which NO is oxidized quantitatively to NO2 by chromium trioxide (CrO3), before conversion to NO2- and NO3- in an alkaline hydrogen peroxide (H2O2) solution. A denitrifier method was used to reduce NO2- and NO3- in the trapping solution quantitatively to nitrous oxide (N2O) for subsequent 15N analysis. NO trapping efficiencies of >85% were obtained with 50 ppb NO in a 0.5 L min-1 air stream bubbling through a solution of 1.2 M H2O2 and 0.5 M NaOH. In a laboratory test with distinct 15NO abundances, the overall precision was 0.29‰ (δ-values) for natural abundance NO and 0.13 atom % for labeled NO, suggesting that our method can be used for both natural abundance studies and 15N labeling experiments. In a soil incubation experiment with 15NH4NO3, NH415NO3, or Na15NO2 amendments, we found distinct 15N abundances in NO, indicating that our method is well suited to investigate NO sources in soils.

A relative method for measuring nitric oxide (NO) fluxes from forest soils.

Many forest ecosystems in the world are suffering from high load of nitrogen (N) deposition and acting as potential contributors to atmospheric nitric oxide (NO), which regulates the oxidative capacity of the troposphere. However, the observation of NO flux with traditional dynamic chamber method is laborious in the forest ecosystem, particularly when the electric power generation system is unavailable. In this work, a relative method based on Fick's law of diffusion was developed to measure NO fluxes from forest soils. This method describes the relationship between NO and other trace gases, such as N2O or CO2, concerning gas fluxes and gas concentration gradients between the uppermost soil layer and the atmosphere. This relative method can be expressed as two forms: based on the directly obtained soil gas and based on the equilibrium gas at soil water surface. To testify the applicability of this method, both laboratory and field experiments were conducted with soil from an N-saturated subtropical forest in Southwestern China. The results demonstrate that the NO fluxes measured based on the later form agreed well with those observed by chamber method, with the deviation rates of around 9% and 30%, respectively. In conclusion, this relative method provides a sound methodological basis for interpreting NO flux variations in the field, especially in N-saturated forest ecosystems, and allows an improvement of statistical N-budget in the world.

[Responses of Soil and Plant 15N Natural Abundance to Long-term N Addition in an N-Saturated Pinus massoniana Forest in Southwest China].

Increasing N deposition in China will possibly cause N saturation of forest ecosystem, further resulting in a series of serious environmental problems. In order to explore the response of forest ecosystem to N deposition in China, and further evaluate and predict the N status of ecosystem, the 15N natural abundance (delta 15N) of soil and plants was measured in a typical Masson pine (Pinus massoniana) forest in southwest China to examine the potential use of delta 15N enrichment factor (epsilon(p/s)) as an effective indicator of N status. Long-term high N addition could significantly increase delta 15N of soil and plants, which was suggested by an on-going N fertilizing experiment with NH4NO3 or NaNO3 for 7 years. Meanwhile, delta 15N of soil and plants under NH, deposition was significantly higher than that under NO- deposition, suggesting different responses of ecosystem to different N-forms of deposition. The "N enrichment factor (epsilon(p/s)) had positive correlations with N deposition, N nitrification, and N leaching in the soil water. Linear correlation between "N enrichment factor and N deposition was found for all Masson pine forests investigated in this and previous studies in China, demonstrating that 15N enrichment factor could be used as an indicator of N status. The NH3 emission control should also be carried out accompanying with NOx emission control in the future, because NH4- deposition had significantly greater impact on the forest ecosystem than NO3- deposition with the same equivalence.

Effects of calcite and magnesite application to a declining Masson pine forest on strongly acidified soil in Southwestern China.

Liming of strongly acidified soil under a Masson pine (Pinus massoniana Lamb.) forest was studied through a seven-year field manipulation experiment at Tieshanping, Chongqing in Southwestern China. To distinguish between the individual effects of Ca(2+) and Mg(2+) addition, we separately applied calcite (CaCO3) and magnesite (MgCO3), rather than using dolomite [CaMg(CO3)2]. Both calcite and magnesite additions caused a significant increase in pH and a decrease in dissolved inorganic monomeric aluminium (Ali) concentration of soil water. Ecological recovery included increases of herb biomass (both treatments) and Mg content in Masson pine needles (magnesite treatment only). However, the growth rate of Masson pine did not increase under either treatment, possibly because of nutrient imbalance due to phosphorus (P) deficiency or limited observation period. In China, acid deposition in forest ecosystems commonly coincides with large inputs of atmogenic Ca(2+), both enhancing Mg(2+) leaching. Calcite addition may further decrease the Mg(2+) availability in soil water, thereby exacerbating Mg(2+) deficiency in the acidified forest soils of southern and southwestern China. The effect of anthropogenic acidification of naturally acid forest soils on P availability needs further study.

[Monitoring nitrogen deposition on temperate grassland in Inner Mongolia].

Nitrogen deposition on temperate steppe was monitored from November 2011 to October 2012 in Taipusi County, Inner Mongolia. The dry deposition of gaseous nitrogen compounds was calculated based on online-monitored atmospheric concentrations of NH3 and NO2 and dry deposition velocity simulated by CMAQ model. The wet deposition, dry deposition of particle, and throughfall deposition were also estimated by collecting rainfall, dust fall, and throughfall samples and the chemical analysis of NH4+ and NO3-concentrations. Results showed that the total deposition of nitrogen was up to 3.43 g x (m2 x a)(-1), which might be harmful to the ecosystem. The wet deposition accounted for about 44% of the total deposition, while dry deposition of gases and particle accounted for 38% and 18%, respectively. Since the deposition contributed more than wet deposition, a great attention should be paid on dry deposition monitoring. However, the very simple method for total deposition monitoring based on throughfall seemed not suitable for grassland because the monitored throughfall deposition was much lower than the total deposition. In addition, reduced nitrogen (NH4+ and NH3) contributed to 71% of the total deposition, while oxidation nitrogen (NO3- and NO2) was only 29%. Therefore, NH3 emission reduction should be considered as important as nitrogen oxides (NO3x) for controlling nitrogen deposition.

[Current status of surface water acidification in Northeast China].

In order to evaluate the status of surface water acidification in Northeast China, chemical composition of 33 small streams was investigated in August, 2011. It was found that only a few waters located in Changbai Mountain had pH of lower than 6.0, and all waters had acid neutralizing capacity (ANC) of higher than 0.2 meq x L(-1). This indicated that surface water acidification was not a regional environmental issue in Northeast China. HCO3- was the major anion, with SO4(2-) concentration mostly below 150 microeq x L(-1) and even much lower NO3- concentration. Low concentration of SO4(2-) and NO3- means no serious acid deposition in this area. However, the distribution of acidic forest soils, with low base cation weathering rate, could only provide limited buffering capacity for surface water to acidification in Northeast China, and the potential risk of water acidification still existed. Currently, acid deposition in Northeast Asia could hardly cause severe acidification of surface water. The neighboring countries should therefore not amplify the environmental impact by transboundary air pollutants from China.

[Effect of flue gas desulfurization gypsum application on remediation of acidified forest soil].

Effect of flue gas desulfurization gypsum (FGDG) application on remediation of a typical acidified forest soil was studied through field experiments at Tieshanping, Chongqing in southwest China for one year. To evaluate the effect and risk of FGDG application, pH value, major ions and heavy metal of soil water in different soil layers were observed dynamically, and heavy metal contained in soil and FGDG were measured. Results showed that Ca2+ and SO4(-2) concentration of soil water in FGDG plots increased with time, pH value was elevated slightly, and n(Ca)/n(Al) value of annual average increased from 2.16, 1.35 and 0.88 to 2.58, 1.52 and 1.12 compared with control plots. The concentration of As, Cu, Cr, Ni and Zn in soil water was not elevated significantly. However, slight enrichment of Cr, Ni and Zn in some upper soil layers was observed. Consequently, FGDG application can improve acidified forest soil, without obviously heavy metal increasing in soil water. However, risk for heavy metal enrichment still exists, which is need for further study.