Effect of organic mineral supplementation in reducing oxidative stress in Holstein calves during short‑term heat stress and recovery conditions

Background This study investigated the effects of inorganic and organic minerals on physiological responses,oxidative stress reduction,and rumen microbiota in Holstein bull calves(123.81±9.76 kg;5 months old)during short-term heat stress(HS)and recovery periods.Eight Holstein calves were randomly assigned to four treatment groups:no mineral supplementation(Con),inorganic minerals(IM),organic minerals(OM),and high-concentration organic minerals(HOM)and two thermal environments(HS and recovery)using 4×2 factorial arrangement in a crossover design of four periods of 35 d.Calves were maintained in a temperature-controlled barn.The experimental period consisted of 14 d of HS,14 d of recovery condititon,and a 7-d washing period.Results Body temperature and respiration rate were higher in HS than in the recovery conditions(P<0.05).Selenium concentration in serum was high in the HOM-supplemented calves in both HS(90.38μg/dL)and recovery periods(102.00μg/dL)(P<0.05).During the HS period,the serum cortisol was 20.26 ng/mL in the HOM group,which was 5.60 ng/mL lower than in the control group(P<0.05).The total antioxidant status was the highest in the OM group(2.71 mmol Trolox equivalent/L),followed by the HOM group during HS,whereas it was highest in the HOM group(2.58 mmol Trolox equivalent/L)during the recovery period(P<0.05).Plasma malondialdehyde and HSP70 levels were decreased by HOM supplementation during the HS and recovery periods,whereas SOD and GPX levels were not significantly affected(P>0.05).The principal coordinate analysis represented that the overall rumen microbiota was not influenced by mineral supplementation;however,temperature-induced microbial structure shifts were indicated(PERMANOVA:P<0.05).At the phylum level,Firmicutes and Actinobacteria decreased,whereas Fibrobacteres,Spirochaetes,and Tenericutes increased(P<0.05),under HS conditions.The genus Treponema increased under HS conditions,while Christensenella was higher in recovery conditions(P<0.05).Conclusion HOM supplementation during HS reduced cortisol concentrations and increased total antioxidant status in Holstein bull calves,suggesting that high organic mineral supplementation may alleviate the adverse effects of HS.

Formation,evolution,reconstruction of black shales and their influence on shale oil and gas resource

Black shales are important products of material cycling and energy exchange among the lithosphere,atmosphere,hydrosphere,and biosphere.They are widely distributed throughout geological history and provide essential energy and mineral resources for the development of human society.They also record the evolution process of the earth and improve the understanding of the earth.This review focuses on the diagenesis and formation mechanisms of black shales sedimentation,composition,evolution,and reconstruction,which have had a significant impact on the formation and enrichment of shale oil and gas.In terms of sedimentary environment,black shales can be classified into three types:Marine,terrestrial,and marine-terrestrial transitional facies.The formation processes include mechanisms such as eolian input,hypopycnal flow,gravity-driven and offshore bottom currents.From a geological perspective,the formation of black shales is often closely related to global or regional major geological events.The enrichment of organic matter is generally the result of the interaction and coupling of several factors such as primary productivity,water redox condition,and sedimentation rate.In terms of evolution,black shales have undergone diagenetic evolution of inorganic minerals,thermal evolution of organic matter and hydrocarbon generation,interactions between organic matter and inorganic minerals,and pore evolution.In terms of reconstruction,the effects of fold deformation,uplift and erosion,and fracturing have changed the stress state of black shale reservoirs,thereby having a significant impact on the pore structure.Fluid activity promotes the formation of veins,and have changed the material composition,stress structure,and reservoir properties of black shales.Regarding resource effects,the deposition of black shales is fundamental for shale oil and gas resources,the evolution of black shales promotes the shale oil and gas formation and storage,and the reconstruction of black shales would have caused the heterogeneous distribution of oil and gas in shales.Exploring the formation mechanisms and interactions of black shales at different scales is a key to in-depth research on shale formation and evolution,as well as the key to revealing the mechanism controlling shale oil and gas accumulation.The present records can reveal how these processes worked in geological history,and improve our understanding of the coupling mechanisms among regional geological events,black shales evolution,and shale oil and gas formation and enrichment.

Effects of Nitrogen Treatments on Organic Carbon Mineralization of Citrus Orchard Soil

[Objective] This study aimed to investigate the effect of soil organic carbon mineralization at different temperature on the amount of nitrogen application, in order to provide references for the establishment of carbon circulation model for orchard eco-system. [Method] The effects of nitrogen treatments on soil organic carbon mineralization of citrus orchard soil were investigated under 10, 20, 30 ℃ by laboratory simulated experiment. [Result] The mineralization rate decreased quickly at the be- ginning of the experiment but remained stable at the late period under three temper- ature treatments. The amounts of CO2 ranged from 1 328.25-2 219.42 mg/kg under three temperature condition, and the amount of soil organic carbon mineralization of 100 mg/kg （N4） treatment was the greatest, while that of CK was the lowest. High level nitrogen treatment （N4 and N3） were significant higher than the lower level nitro- gen treatment （N2 and N1）. The soil organic carbon mineralization rate increased with the temperature from 10 to 30℃. The dependence of soil carbon mineralization to temperature （Q10） was different under different nitrogen treatments that the Qlo value of N2 treatment was the lowest while that of the N4 treatment was the greatest. The soil organic carbon mineralization in Citrus orange orchard soil was affected significantly by high level nitrogen treatment, but with no significance under lower nitrogen treatment. [Conclusion] The dependence of soil carbon mineralization to temperature （Q10） increased with the increasing nitrogen input. The combination of nitrogen with temperature may increase the CO2 emission from Citrus orchard soil.

Predicting dynamics of soil organic carbon mineralization with a double exponential model in different forest belts of China

The dynamics of soil organic carbon （SOC） was analyzed by using laboratory incubation and double exponential model that mineralizable SOC was separated into active carbon pools and slow carbon pools in forest soils derived from Changbai and Qilian Mountain areas. By analyzing and fitting the CO2 evolved rates with SOC mineralization, the results showed that active carbon pools accounted tor 1.0% to 8.5% of SOC with an average of mean resistant times （MRTs） for 24 days, and slow carbon pools accounted for 91% to 99% of SOC with an average of MRTs for 179 years. The sizes and MRTs of slow carbon pools showed that SOC in Qilian Mountain sites was more difficult to decompose than that in Changbai Mountain sites. By analyzing the effects of temperature, soil clay content and elevation on SOC mineralization, results indicated that mineralization of SOC was directly related to temperature and that content of accumulated SOC and size of slow carbon pools from Changbai Mountain and Qilian Mountain sites increased linearly with increasing clay content, respectively, which showed temperature and clay content could make greater effect on mineralization of SOC.

Composition and mineralization of soil organic carbon pools in four single-tree species forest soils

Forest soil carbon （C） is an important compo- nent of the global C cycle. However, the mechanism by which tree species influence soil organic C （SOC） pool composition and mineralization is poorly understood. To understand the effect of tree species on soil C cycling, we assessed total, labile, and recalcitrant SOC pools, SOC chemical composition by 13C nuclear magnetic resonance spectroscopy, and SOC mineralization in four monoculture plantations. Labile and recalcitrant SOC pools in surface （0-10 cm） and deep （40-60 cm） soils in the four forests contained similar content. In contrast, these SOC pools exhibited differences in the subsurface soil （from 10 to 20 cm and from 20 to 40 cm）. The alkyl C and O-alkyl C intensities of SOC were higher in Schima superba and Michelia macclurei forests than in Cunninghamia lanceolata and Pinus massoniana forests. In surface soil, S. superba and M. macclurei forests exhibited higher SOC mineralization rates than did P. massoniana and C.lanceolata forests. The slope of the straight line between C60 and labile SOC was steeper than that between C60 and total SOC. Our results suggest that roots affected the composition of SOC pools. Labile SOC pools also affected SOC mineralization to a greater extent than total SOC pools.

Effects of organic mineral fertiliser on heavy metal migration and potential carbon sink in soils in a karst region

Heavy metal pollution in karst mountainous area of Guizhou has spread due to the long-term exploitation of mineral resources and the improper disposal of environmentally hazardous waste. Heavy metals are characterised by non-degradation, strong toxicity, and constant accumulation, posing a grave threat to karst mountain fragile soil ecosystem. To reduce the harm caused by heavy metal pollution and damage to agricultural products, research was undertaken on the basis of previous work by simulating pot experiments on pak choi cabbage(Brassica rapa chinensis)planted in Cd-contaminated soil: different amounts of organic mineral fertilisers(OMF) compared with chemical fertiliser(CF) were used and by detecting the amount of heavy metal in the mature vegetable, a better fertilisation strategy was developed. The results showed that the Cd content in vegetables grown with CF was 23.70 mg/kg,while that of vegetables grown with OMF and bacterial inoculant was the lowest at 15.13 mg/kg. This suggests that the use of OMF and microbes in karst areas not only promotes plant growth but also hinders plant absorption of heavy metal ions in the soil. In addition, through the collection of pot leachate, the detection of water chemistrycharacteristics, and the calculation of the calcite saturation index, it was found that the OMF method also induces certain carbon sink effects. The results provide a new way in which rationalise the use of OMFs in karst areas to alleviate soil heavy metal pollution and increase soil carbon sequestration.

Effects of Continuous Mineral and Organic Fertilizer Inputs and Ploughing on Groundnut Yield and Soil Fertility in a Groundnut-Sorghum Rotation in Central Burkina Faso

Two field experiments were conducted at Saria in the centre of Burkina Faso in order to assess the effect of chemical and organic fertilizers on yields and soil fertility on two different soils. Groundnut haulm yield, pod yield, number of pods, % 2-seeded pods, % pod rot, seed yield and 100 seeds weight as well as sorghum dry shoot and grain yields were measured. Most of the different variables were affected by continuous cropping without fertilizer application on the two soils, in particular on the coarse one. The effect of nutrient deficiencies was observed. The mineral fertilizers maintained yields, but their supply was not able to replenish the nutrient uptake by plants. The effect of compost on crop production was initially minimal, but improved during years seven and height. Tillage had also a slightly positive effect on yield, which varied with soil type. In the control plot, the content of organic matter decreased in five years and did not increase with the application of fertilizers. In contrast, addition of fertilizers increased total N and Bray-I P. Nitrogen, P, K and Ca balances were negative in almost all treatments without mineral fertilizers. Results showed that fertilizers used were inadequate for maintaining soil fertility and yields in long run. However, extra production did not provide significant profits.

Preservation of organic matter in soils of a climobiosequence in the Main Range of Peninsular Malaysia

Limited information is available about factors of soil organic carbon(SOC) preservation in soils along a climo-biosequence. The objective of this study was to evaluate the role of soil texture and mineralogy on preservation of SOC in the topsoil and subsoil along a climo-biosequence in the Main Range of Peninsular Malaysia. Soil samples from the A and B-horizons of four representative soil profiles were subjected to particle-size fractionation and mineralogical analyses including X-ray diffraction and selective dissolution. The proportion of SOC in the 250-2000 μm fraction(SOC associated with coarse sand) decreased while the proportion of SOC in the <53 μm fraction(SOC associated with clay and silt)increased with depth. This reflected the importance of the fine mineral fractions of the soil matrix for SOC storage in the subsoil. Close relationships between the content of SOC in the <53 μm fraction and the content of poorly crystalline Fe oxides [oxalate-extractable Fe(Fe_o) – pyrophosphate-extractable Fe(Fe_p)] and poorly crystalline inorganic forms of Al [oxalateextractable Al(Al_o) – pyrophosphate-extractable Al(Al_p)] in the B-horizon indicated the importance of poorly crystalline Fe oxides and poorly crystalline aluminosilicates for the preservation of SOC in the Bhorizon. The increasing trend of Fe_o-Fe_p and Al_o-Al_p over elevation suggest that the importance of poorly crystalline Fe oxides and poorly crystalline aluminosilicates for the preservation of SOC in the Bhorizon increased with increasing elevation. This study demonstrates that regardless of differences in climate and vegetation along the studied climobiosequence, preservation of SOC in the subsoil depends on clay mineralogy.

Mineralization and Transformation of Nitrogen Derived from Plant Materials in Soils over 10 Years

Results of a 10-year decomposition experiment indicated that the annual mineralization rate of organic N in newly-formed humus varied with the type of original plant materials and the water regimes for decomposition, ranging from 0.028 to 0.074. The mineralization rate under waterlogged conditions was higher than that under upland conditions. The proportion of α-amino acid N in humus newly-formed under waterlogged conditions was slightly higher than that under upland conditions. It decreased gradually with time, while the proportion of nonhydrolyzable N showed no consistent trend, irrespective of the water regimes for decomposition. The distribution of amino acids in humus newly- formed from different plant materials under various water regimes was quite similar with that in original plant materials, and only minor differences could be found among them. For example, in comparison to original plant materials, the newly-formed humus contained higher proportions of isoleucine, cystine, γ-amino-butync acid and ornithine, and lower proportions of phenylalanine and proline. Moreover the proportion of phenylalanine was higher in the humus newly-formed under waterlogged conditions than that under upland conditions.

Linking soil organic carbon mineralization to soil physicochemical properties and bacterial alpha diversity at different depths following land use changes

Background Anthropogenic land use changes(LUCs)impart intensifying impacts on soil organic carbon(SOC)turnover,leading to uncertainty concerning SOC mineralization patterns and determining whether soils act as“source”or“sink”in the global carbon budget.Therefore,understanding the SOC mineralization characteristics of different LUC patterns and their potential influencing factors is crucial.An indoor incubation experiment was conducted to study the SOC mineralization patterns and their relevance to soil physicochemical properties,soil enzyme activity,SOC fractions,and bacterial alpha diversity.The soils were collected from two layers of five typical LUC patterns in Yellow Sea Forest Park,including four that were converted from wheat-corn rotation systems[a gingko plantation(G),a metasequoia plantation(M),a gingko-wheat-corn agroforestry system(GW),and a gingko-metasequoia system(GM)]and a traditional wheat-corn system(W).Results LUCs had significant and diverse impacts on the SOC content and SOC fraction contents and on soil enzyme activity.The cumulative SOC mineralization was significantly higher in the M systen than in the W and GW systems at 0-20 cm depth and higher in the G system than in the GW system at 20-40 cm depth after 60-day incubation.The mineralization ratio was highest in the W system and lowest in the GW system.The soil pH and bulk density had a significant negative correlation with the cumulative SOC mineralization,while the soil bacterial Shannon index had a significant positive correlation with cumulative SOC mineralization.Multiple stepwise linear regression analysis showed that the SOC mineralization potential was dominantly explained by the bacterial Shannon index and operational taxonomic units(OTUs).The GW system had lower potentially mineralizable SOC and higher SOC stability.Additionally,the incubation time and cumulative SOC mineralization were well fitted by the first-order kinetic equation.Conclusions LUCs significantly changed SOC mineralization characteristics and the results highlighted the important roles of the bacterial community in soil carbon cycling,which contributes to the fundamental understanding of SOC turnover regulation.

Phosphate and Nitrate Release from Mucky Mineral Soils

High-organic (mucky) mineral soils make a small proportion of the Canadian agricultural land but are highly productive, especially for organic farming. Although these high-quality soils may release large amounts of nitrate and phosphate to the environment, there is yet no reliable agro-environmental indicator for managing N and P compared to the adjacent mineral and organic soils. Our objective was to quantify the N mineralization and P environmental risks of mucky mineral soils. Nine Canadian soil series (eight Orthic Humic Gleysols and one Terric Humisol with three variants) were analyzed for texture, pH(CaCl2), total C and N, oxalate and Mehlich-III (M-III) extractable P, Al and Fe, and water extractable P (Pw). Soil texture varied from loamy sand to heavy clay, organic carbon (OC) content ranged from 14 to 392 g·OC·kg-1, total N from 1.21 to 16.38 g·N·kg-1, and degree of P saturation (DPSM-III) as molar (P/[Al + γFe])M-III percentage between 0.3% and 11.3%. After 100 d of incubation, soils released 31 to 340 mg·N·kg-1. The N mineralization rate was closely correlated to organic matter content (r = 0.91, p Sandy to loamy soils released 1.2 - 1.8 kg·N·ha-1·d-1 compared to 1.6 - 2.4 kg·N·ha-1·d-1 for clayey soils, 2.0 - 2.8 kg·N·ha-1·d-1 for mucky clayey soils and 2.6 - 2.7 kg·N·ha-1·d-1 for Humisol. For (P/[Al + 3Fe])M-III ratios of mucky clayey soils below 4.5%, water-extractable P did not exceed threshold of 9.7 mg Pw L-1. Mucky clayey soils could be managed for N similarly to Humisol and for P with (P/[Al + 3Fe])M-III percentage not exceeding 4.5%.

Limited impacts of occasional tillage on dry aggregate size distribution and soil carbon and nitrogen fractions in semi-arid drylands

Tillage management that minimizes the frequency and intensity of soil disturbance can increase soil carbon(C)and nitrogen(N)sequestration and improve the resilience of dryland cropping systems,yet the impact of occasional disturbance on soil aggregate formation and the soil organic carbon(SOC)storage within aggregates has not been studied well.We evaluated the effect of four tillage management practices on soil dry aggregate size distribution,aggregate-protected C and N,mineral-associated organic matter carbon(MAOM-C),particulate organic matter carbon(POM-C),and corn(Zea mays L.)and sorghum(Sorghum bicolor(L.)Moench)yields in a semi-arid dryland cropping system.Treatments included conventional tillage(CT),strip-tillage(ST),no-tillage(NT),and occasional tillage(OT)management in a corn-sorghum rotation.Soil macro-aggregates were 51-54%greater under ST,NT,and OT,while small and micro-aggregates were greater in CT.Conventional tillage reduced soil aggregate-associated C by 28-31%in macro-aggregates and 47-53%in small aggregates at 26 months(M)sampling compared to ST,NT,and OT.In clay+silt fraction,CT had 14-16%,21-26%,and 36-43%less SOC at 7,14,and 26M samplings,respectively,than ST,NT,and OT.Aggregate associated N was generally similar under ST,NT,and OT,which was greater on average than CT.Soil MOAM-C and POM-C under ST,NT,and OT were generally greater than respective SOC fractions under CT at 19 and 26 M after OT implementation.Corn and sorghum yields were similar among tillage systems in 2020,but greater under ST,NT,and OT than CT in 2021.Our results suggest that while frequent intensive tillage can lower SOC and N storage,a single stubble mulch occasional tillage after several years of NT does not lead to soil C and N losses and soil structural instability in semi-arid drylands.

Bulk density of mineral and organic soils in the Canada’s arctic and sub-arctic

Bulk density is an indicator of soil compaction subject to anthropogenic impact,essential to the interpretation of any nutrient budgets,especially to perform carbon inventories.It is so expensive to measure bulk density in arctic/sub-arctic and there are relatively very few field measurements are available.Therefore,to establish a bulk density and SOC empirical relationship in Canada’s arctic and sub-arctic ecosystems,compiled all the bulk density and SOC measurements that are available in Northern Canada.In addition an attempt has been made for bulk density and SOC field measurement in Yellowknife and Lupin,to develop an empirical relationship for Canada’s arctic and sub-arctic.Relationships between bulk density(BD)and soil organic carbon(SOC)for mineral soil and organic soils(0–100 cm depth)were described by exponential functions.The best fit model,predictive bulk density(BDp),for mineral soil,(BDp=0.701+0.952 exp(
0.29 SOC),n=702,R2=0.99);for organic soil(BDp=0.074+2.632 exp(
0.076 SOC),n=674,R2=0.93).Different soil horizons have different bulk densities and may require different predictive equations,therefore,developed predictive best fit exponential equation for both mineral and organic soils together(BDp=0.071+1.322 exp(
0.071 SOC),n=1376,R2=0.984),where X is a dummy variable with a value of 0 for surface peat(0–25 cm depth)and 1 for subsurface peat(25–175 cm).We recommend using the soil organic carbon density approach to estimate BD from SOC because it allows BD to be predicted without significant bias.

Dissimilatory iron reduction contributes to anaerobic mineralization of sediment in a shallow transboundary lake

Dissimilatory iron reduction(DIR)coupled with carbon cycling is increasingly being recognized as an influential process in freshwater wetland soils and sediments.The role of DIR in organic matter(OM)mineralization,however,is still largely unknown in lake sediment environments.In this study,we clarified rates and pathways of OM mineralization in two shallow lakes with seasonal hydrological connectivity and different eutrophic situations.We found that in comparison with the domination of DIR(55%)for OM mineralization in Lake Xiaoxingkai,the contribution of methanogenesis was much higher(68%)in its connected lake(Lake Xingkai).The differences in rates and pathways of sediment OM mineralization between the two lakes were attributed to higher concentrations of carbonate associated iron oxides(Fecarb)in Lake Xiaoxingkai compared to Lake Xingkai(P=0.002),due to better deposition mixing,more contributions of terrigenous detrital materials,and higher OM content in Lake Xiaoxingkai.Results of structural equation modeling showed that Fecarb and total iron content(TFe)regulated 25%of DIR in Lake Xiaoxingkai and 76%in Lake Xingkai,accompanied by a negative effect of TFe on methanogenesis in Lake Xingkai.The relative abundance and diversity of Fe-reducing bacteria were significantly different between the two lakes,and showed a weak effect on sediment OM mineralization.Our findings emphasize the role of iron minerals and geochemical characterizations in regulating rates and pathways of OM mineralization,and deepen the understanding of carbon cycling in lake sediments.

Thermochemical sulphate reduction and Huayuan lead-zinc ore deposit in Hunan, China

In recent years, some arguments with regard to the organicmineralization of MVT lead-zinc ore deposit are focused on the thermochemical sulphate reduction in the presence of organic matter. Based on the research into the organic geochemistry and C, O, S isotopes of mineralized host rocks, mineral gas fluid inclusion and solid bitumen from Huayuan (W. Hunan, China) lead-zinc ore deposit formed in the algal limestones of Qingxudong formation, Lower Cambrian, the authors consider that a lot of organic matter occurred and participated in mineralization. The organic matter from different sources participated in the mineralization with two main forms: thermochemical sul-phate reduction and thermal degradation which supplied abundant H2S for the precipitation.

Iron Mobilization and Mineralogical Alterations Induced by Iron-Deficient Cucumber Plants (Cucumis sativus L.) in a Calcareous Soil

Dicotyledons cope with ion(Fe) shortage by releasing low-molecular-weight organic compounds into the rhizosphere to mobilize Fe through reduction and complexation mechanisms. The effects induced by these root exudates on soil mineralogy and the connections between Fe mobilization and mineral weathering processes have not been completely clarified. In a batch experiment, we tested two different kinds of organic compounds commonly exuded by Fe-deficient plants, i.e., three organic acids(citrate, malate, and oxalate)and three flavonoids(rutin, quercetin, and genistein), alone or in combination, for their ability to mobilize Fe from a calcareous soil and modify its mineralogy. The effect of root exudates on soil mineralogy was assessed in vivo by cultivating Fe-deficient and Fe-sufficient cucumber plants(Cucumis sativus L.) in a RHIZOtest device. Mineralogical analyses were performed by X-ray powder diffraction. The batch experiment showed that citrate and, particularly, rutin(alone or combined with organic acids or genistein)promoted Fe mobilization from the soil. The combinations of rutin and organic acids modified the soil mineralogy by dissolving the amorphous fractions and promoting the formation of illite. These mineralogical alterations were significantly correlated with the amount of Fe mobilized from the soil. The RHIZOtest experiment revealed a drastic dissolution of amorphous components in the rhizosphere soil of Fe-deficient plants, possibly caused by the intense release of phenolics, amino acids, and organic acids, but without any formation of illite. Both batch and RHIZOtest experiments proved that exudates released by cucumber under Fe deficiency concurred to the rapid modification(on a day-scale) of the mineralogy of a calcareous soil.

Theoretical limiting concentration for mineralization of trichloromethane and dichloromethane in aqueous solutions by AOPs

It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting concentration,LC)is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane(CHCl3)and dichloromethane(CH2Cl2) are selected as the model systems,and the equilibrium concentration(theoretical limiting concentration,TLC)for the mineralization of chlorinated methanes in aqueous solutions at the different initial concentrations of chlorinated methanes,pH values and·OH concentrations by AOPs are investigated by thermodynamic analysis.The results in this paper show that the TLC for the mineralization of CHCl3 and CH2Cl2 with·OH increases with increasing initial concentrations of CHCl3 and CH2Cl2,decreases with increasing concentration of·OH,and the TLC for the mineralization of CHCl3 decreases with increasing pH values except that the pH value changes from 3.0 to 3.5.For the mineralization of CH2Cl2 with·OH,at the concentrations of·OH obtained from the literature,there is no obvious change of the TLC with pH values,while as the concentrations of·OH increase by 10 and 100 times,the TLC decreases with the increasing pH values from 2.0 to 3.0 and from 3.5 to 4.5,and increases with the increasing pH values from 3.0 to 3.5 and from 4.5 to 5.0.The investigations in this paper imply that high concentration of·OH,a bit higher pH values(4.0–5.0)in acid environment and low initial concentrations of the organic contaminants are beneficial for the complete mineralization of chlorinated methanes by AOPs.