Arsenate (AsO4 3−): chemistry, biology, and environmental significance

Chemical characteristics and forms

Chemically, arsenate behaves as a trivalent anion with three negative charges and a tetrahedral geometry around the arsenic atom. In aqueous solution it exists in equilibrium with protonated species (dihydrogen arsenate H2AsO4 − and hydrogen arsenate HAsO4 2−) depending on pH and ionic strength. Arsenates are typically oxidizing compared with lower-valent arsenic species and form stable crystalline minerals and soluble salts.

• Related concepts: definition and basic data: definition and formula.
• Oxidation state: arsenic in arsenate is As(V): oxidation state.
• Acid/base relationship: conjugate base of arsenic acid.

Biological effects and mechanism of toxicity

Arsenate’s structural similarity to phosphate allows it to enter cells via phosphate transporters and to replace phosphate groups in biochemical reactions. For example, arsenate can form unstable analogs of phosphate esters and ADP–arsenate, which interfere with ATP production and energy metabolism. This disruption of phosphorylation and other phosphate-dependent pathways is a primary reason for arsenate’s toxicity to plants, animals and humans.

Some microorganisms have evolved strategies to tolerate or exploit arsenate. Certain bacteria reduce arsenate to arsenite or use arsenate as an electron acceptor in respiration; these microbes are subjects of environmental microbiology and bioremediation research. For microbial roles and examples see microbial arsenic cycling and arsenate respiration.

Environmental occurrence and applications

Arsenate is naturally found in oxidizing environments, mineral deposits and groundwater where arsenic-bearing minerals weather. Human activities such as mining, pesticide use and improper waste disposal can increase arsenate concentrations in soil and water. Historically, arsenate salts were used as pesticides and wood preservatives; many of those uses have been reduced or banned because of health and environmental concerns.

Uses, risks, and notable distinctions

Modern concerns about arsenate focus on drinking-water contamination, soil remediation and regulatory limits. Analytical chemistry methods routinely monitor arsenate alongside other arsenic species because toxicity and mobility differ by oxidation state. Important distinctions include arsenate (As(V)) versus arsenite (As(III)); arsenite is typically more mobile in reducing conditions and often more acutely toxic.

1. Salts and minerals of arsenate: broad industrial and geological relevance — mineralogy.
2. Public health and remediation: monitoring and mitigation strategies — public health.
3. Research directions: microbial transformation and engineered remediation — bioremediation research.
4. Further reading and educational resources: introductory materials and databases — reference materials.

Because arsenate intersects inorganic chemistry, environmental science and biology, it is important both as a laboratory subject and a public-health concern. The interplay between its chemical similarity to phosphate and its distinct redox chemistry explains why arsenate remains a notable anion in natural and contaminated systems.