Effects Of Heavy Metal Cu And Zn On Microbial Community Metabolic Profiles And Hydrolytic Enzyme Activities In Composting

Livestock and poultry manure is one kind of important fertilizer resources. Fertilization and recycle of livestock and poultry manure is main research orientation of recycling agriculture. Owing to the requirement of economic benefit, farms often feed livestock and poultry with fodder added the additives which contain heavy metal element. Livestock and poultry have lower absorption rate for the heavy metal elements, leading to most of the heavy metal elements discharging from their bodies(above 95%). The concentration of Cu in pig manure ranged from 12.1 mg·kg^-1to1742.1 mg·kg^-1and the concentration of Zn in pig manure ranged from 40.5 mg·kg^-1to 2286.8 mg·kg^-1. Composting progresses under the mirobe and enzyme,and is one of effective pathways for agricultral waste,s recycle and hazard freetreatment. Heavy metals have some effects on the enzymes. Heavy metals not only have activating effects on the enzymes as a kind of coenzyme or prosthetic group, but also have inhibiting effects. The effects of heavy metal in the livestock and poultry manure on the composting is one important problem in the treatment of agricutral waste. It is distinctly important for recycle and harmlessness of livestock and poultry manure to intensive study of the problem. The paper studied the effects of heavy metal Cu and Zn on the physicochemical property and hydrolase activity,and first researched the effects of heavy metal Cu and Zn on the microbial community metabolic property. The results obtained mainly were:An experiment was conducted using mixed materials of pig excrement, wheat straw and waste auricularia-bran to study the effect of the heavy metal copper (Cu) on physicochemical characteristics, hydrolase activities and the microbial community metabolic property during composting at high temperature and static state. There are three treatments in this experiment which were the CK treatment (without added Cu), the low Cu treatment (L;Cu concentration 100 mg/kg), The high Cu treatment(H;Cu concentration 500 mg/kg).The results indicated that:1. The change of microbial community metabolic property: low density of heavy metal Cu treatment can enhance the metabolic capability of amino acids and polymers,while high density of heavy metal Cu treatment had depression effect on the metabolic capability of polymers and intermediate metabolite.2. The changes of hydrolase activity during composting: low density of heavy metal Cu treatment produced activation effection on hydrolytic enzyme activities,while high density of heavy metal Cu treatment showed depression effect on them. The average enzyme activities of three kinds of hydrolase showed that those of L treatment were highest and those of H treatment were lowest. The average enzyme activities of protease respectively were: (2.10±0.41), (2.38±0.59), (1.98±0.37) mg glycine·(g·d)^-1; The average enzyme activities of urease respectively were: (31.21±6.87), (31.36±6.91), (22.05±5.43) mg NH3-N·(g·d)^-1; The average enzyme activities of cellulase respectively were: (31.97±15.23), (34.35±12.33), (27.48±12.52) mg glucose·(g·d)^-1.3. The changes of physicochemical property during composting: CK treatment achieved the requirement of the harmlessness;the harmless degree of L treatmentwas not perfect,and its high temperature phase(>50℃) only lasted 4 d;the H treatment didn't achieve the requirement of the harmlessness(it exceeded 55℃only 1 d and the high temperature phase lasted 2 d).The effects of Cu on electrical conductivity during the composting mainly lied in high-temperature phase and hypothermic phase,and the average value of electrical conductivity were: L>CK>H. The difference between treatments was also mainly in high-temperature phase and cooling phase, and the peak value of three treatments were 8.06, 8.27, 7.51 respectively at 4 d. An experiment was conducted using mixed materials of pig excrement, wheat straw and waste auricularia-bran to study the effect of the heavy metal zinc (Zn) on physicochemical characteristics, hydrolase activities during composting at high temperature and static state. There are three treatments in this experiment which were the CK treatment (without added Zn), the low Zn treatment (L;Zn concentration 400 mg/kg), The high Zn treatment(H;Zn concentration 1000 mg/kg).The results indicated that:1. The changes of hydrolase activity during composting: L treatment showed an activatiing effect on cellulase activity, while the H treatment had a depressive effect on the high-temperature phase. Addition of Zn (both L and H) showed a negative effect on the hypothermic phase. Addition of Zn (both L and H) showed an activating effect on protease activity in the initial phase of composting (0?4 d). Protease activity in the H treatment was significantly higher than that of the CK treatment. Both L and H treatments showed a negative effect on protease activity in the high-temperature and hypothermic phases. Addition of Zn (both L and H) showed an activating effect on urease activity in the initial phase of composting, but produced a negative effect and hampered the acidamide conversion process in anaphase of composting.2. The CK treatment (without added Zn) achieved the requirement for harmlessness; the harmless degree of the L treatment (Zn concentration 400 mg/kg) was not perfect, as the high-temperature phase (>50°C) only lasted 3 d. The H treatment (Zn concentration 1000 mg/kg) did not achieve the requirement for harmlessness. The effect of Zn on EC was mainly in anaphase of the calefactive phase, high-temperature phase, and cubhood of the hypothermic phase. The effect of Zn on pH was mainly in the high-temperature phase, and only CK was in the optimal pH range (7.5⁸.5).